Study Shows Potential Of Targeted Microbubbles Using Peregrine's VTA Technology To Identify Which Cancer Patients Would Benefit

Peregrine Pharmaceuticals, Inc. (Nasdaq: PPHM), a clinical stage biopharmaceutical company developing targeted therapeutics for the treatment of cancer and hepatitis C virus (HCV) infection, today announced publication of a study demonstrating that microbubbles targeted to tumor blood vessels can be used to monitor patient response to anti-angiogenesis therapy, identifying at an early stage which cancer patients are benefiting from the treatment. This information could allow oncologists to modify patient treatment regimens soon after starting therapy, so that non-responders could be switched to other therapies that might be more effective for them. The potential of the approach is enhanced by the fact that the targeted microbubbles are "read" using ultrasound technology, which is widely available in most physicians' offices and is minimally invasive, safe and cost-effective.

The research, the results of which appear in the January 1, 2007 issue of Clinical Cancer Research, was conducted by scientists at the University of Texas Southwestern Medical Center and funded by Peregrine. The published article demonstrates the potential of Peregrine's Vascular Targeting Agent (VTA) technology platform for imaging and diagnosis of solid tumors using agents targeted to tumor blood vessels. Patents covering Peregrine's VTA technology platform have been exclusively licensed from the UT Southwestern Medical Center. The "personalized medicine" made feasible by this approach has the potential to increase the efficacy of cancer regimens, reduce side effects from ineffective treatments and improve the overall cost effectiveness of cancer therapy.

Anti-angiogenesis agents such as Avastin(R) treat cancer by preventing the formation of tumor blood vessels, thereby "starving" tumors. They are increasingly being used in combination with chemotherapy agents as cornerstones of cancer therapy, yet not all patients actually respond to the approach (the patient response rate in two recent studies ranged from 26% to 35%). The ability to determine which cancer patients are responding to anti-angiogenesis treatment early in the process could enable oncologists to ensure that each patient was receiving the therapy that is most effective for their specific condition, while reducing the risk of side effects from ineffective treatments and also enabling the health care system to avoid large expenditures on regimens that ultimately produce little therapeutic benefit.

"We believe this study demonstrating the potential utility of targeted microbubbles could be a breakthrough in developing cost-effective methods for monitoring the effectiveness of anti-angiogenesis therapies which may have great clinical and commercial significance," said Steven W. King, president and CEO of Peregrine. "This technology could have potential not only for evaluating the effectiveness of currently approved agents such as Avastin(R) but also for assessing new anti-angiogenesis approaches currently in clinical development, and eventually for evaluating the effectiveness of anti-angiogenic agent cocktails, which are likely to be developed as more products in this class are approved. We look forward to continuing our collaboration with the researchers at UT Southwestern to advance this technology toward human clinical studies in order to fully evaluate its potential."

The UT Southwestern researchers, led by Dr. Rolf Brekken, tested the targeted microbubble approach in several mouse models of pancreatic cancer, a particularly aggressive and lethal disease. The microbubbles are tiny lipid or albumin shells filled with an inert gas that have a well-established safety record as contrast agents for ultrasound imaging applications, and they are currently widely used in cardiovascular medicine.

In the reported studies, Dr. Brekken and his colleagues linked the microbubbles to antibodies that target them to specific markers on tumor blood vessels. The microbubbles were then administered to tumor-bearing animals and ultrasound images of the tumor were recorded. The ultrasound images identified the number of tumor blood vessel markers that were present before and after treatment with several anti-angiogenic agents, including Avastin and 2C3, a novel anti-angiogenic antibody in preclinical development by Peregrine. A decrease in the number of tumor blood vessel markers indicated that the treatment was working as intended. The researchers determined that measurements of tumor blood vessel markers made using the microbubble approach correlated well with measurements made using conventional invasive techniques.

"These encouraging results indicate that targeted microbubble contrast agents could be a robust and accessible method for increasing the utility and cost-effectiveness of anti-angiogenic cancer treatments," said Dr. Brekken, assistant professor of surgery and pharmacology, a researcher at the Nancy B. and Jake L. Hamon Center for Therapeutic Oncology Research and Effie Marie Cain Research Scholar in Angiogenesis Research at UT Southwestern. "The ability to rapidly monitor and modify therapy would be valuable for patients, physicians and the larger healthcare system. The clinical development of contrast agents is typically faster than for therapeutics, and clinical trials of this approach could be feasible within 12 to 18 months. We look forward to working with Peregrine to advance this potentially important new approach."

The article, "Monitoring Response to Anticancer Therapy by Targeting Microbubbles to Tumor Vasculature," is published in Clinical Cancer Research 2006:12(23) January 1, 2007.

About Peregrine Pharmaceuticals

Peregrine Pharmaceuticals, Inc. is a biopharmaceutical company with a portfolio of innovative product candidates in clinical trials for the treatment of cancer and hepatitis C virus (HCV) infection. The company is pursuing five separate clinical trials in cancer and HCV infection in the U.S. and India with its lead product candidates bavituximab and Cotara(R). Peregrine also has in-house manufacturing capabilities through its wholly owned subsidiary Avid Bioservices, Inc. (http://www.avidbio.com), which provides development and bio-manufacturing services for both Peregrine and outside customers. Additional information about Peregrine can be found at http://www.peregrineinc.com.

Safe Harbor Statement:

Statements in this press release which are not purely historical, including statements regarding Peregrine Pharmaceuticals' intentions, hopes, beliefs, expectations, representations, projections, plans or predictions of the future are forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. The forward-looking statements involve risks and uncertainties including, but not limited to, the risk that use of targeted microbubbles to monitor patient response to anti-angiogenesis therapy may not be as effective when used in connection with human patients. It is important to note that the company's actual results could differ materially from those in any such forward-looking statements. Factors that could cause actual results to differ materially include, but are not limited to, uncertainties associated with completing preclinical and clinical trials for our technologies; the early stage of product development; the significant costs to develop our products as all of our products are currently in development, preclinical studies or clinical trials; obtaining additional financing to support our operations and the development of our products; obtaining regulatory approval for our technologies; anticipated timing of regulatory filings and the potential success in gaining regulatory approval and complying with governmental regulations applicable to our business. Our business could be affected by a number of other factors, including the risk factors listed from time to time in the Company's SEC reports including, but not limited to, the annual report on Form 10-K for the year ended April 30, 2006, and the quarterly report on Form 10-Q for the quarter ended October 31, 2006. The Company cautions investors not to place undue reliance on the forward-looking statements contained in this press release. Peregrine Pharmaceuticals, Inc. disclaims any obligation, and does not undertake to update or revise any forward-looking statements in this press release.

Peregrine Pharmaceuticals, Inc.
http://www.peregrineinc.com

Genetic Factors Associated With Head And Neck Cancer Examined By Study

Preliminary research indicates that several specific genetic alterations are associated with the development of smoking-related head and neck skin cancers, according to a report in the January 10 issue of JAMA.

Despite its slowly declining incidence rate and a modest improvement in 5-year survival, squamous cell carcinoma (SCC; a type of cancer similar to the common form of skin cancer) of the head and neck continues to be a clinical challenge. With a worldwide prevalence of more than 1.6 million, it is estimated that in 2006, about 30,990 new cases will be diagnosed in the United States. Even with the use of modern therapeutic options that include surgery, radiation therapy, and chemotherapeutic intervention, 50 percent of all patients will ultimately die of this disease, with more than 7,400 deaths projected for 2006 in the United States, according to background information in the article.

Charis Eng, M.D., Ph.D., of the Genomic Medicine Institute at the Cleveland Clinic Foundation, Cleveland, and colleagues conducted a study to determine the extent of genomic alterations in the stroma (connective tissue) of head and neck SCC. Tumor epithelium (the cancer itself) and surrounding stroma were isolated from 122 patients with oral cavity and oropharyngeal (relating to the mouth and pharynx) or hypopharyngeal (bottom part of throat) SCC and these tissues were subjected to whole genome analysis.

Tumor-associated stroma of head and neck SCC from smokers were found to have a high degree of genomic alterations. A correlation between tumor aggressiveness could be found for a specific set of 5 loci. Three stroma-specific loci were associated with tumor size and regional nodal (small mass) metastases. Also, 2 specific genomic alterations (markers termed "hot spots") were positively correlated with node metastases and clinical stage.

"Stroma-specific genetic alterations are associated with smoking-related head and neck SCC genesis," the authors write. "We hope that our genomic observations, which point to genomic regions that may harbor many genes, will guide future in-depth functional and mechanistic studies. Nevertheless, our current observations can be used to identify new biomarkers for prediction of clinical outcome and potentially novel compartments for targeted therapy and prevention."

###

(JAMA. 2007;297:187-195)

This study was funded in part by a grant from the state of Ohio and the Doris Duke Distinguished Clinical Scientist Award. Cleveland Clinic Innovations has submitted a provisional patent application based on these observations. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.

Contact: Molly Johnson
JAMA and Archives Journals

Scripps Research Combination Therapy Obliterates New Vessel Growth In Tumors And Retinopathy

The paper is being published online in the Proceedings of the National Academy of Sciences.

"While a number of new drugs that inhibit new blood vessel growth are now available in the clinics, no one so far has been cured with available anti-angiogenic agents," said Professor Martin Friedlander, a Scripps Research scientist and retina specialist at Scripps Clinic who led the study. "Our study shows that combining anti-angiogenic agents that target multiple angiogenic pathways can significantly increase the effectiveness of such a therapeutic approach. Such combination angiostatic therapy provides a whole new range of treatment options for patients with neovascular diseases, where complete inhibition of new blood vessel growth is the desired result."

While new blood vessel growth from preexisting capillaries ("angiogenesis") is fundamental to survival, the abnormal formation of new blood vessels ("neovascularization") contributes to the pathogenesis of tumor growth and metastasis as well as the vast majority of diseases that lead to catastrophic loss of vision. A number of angiostatic molecules have been used to impair blood vessel formation as clinical adjuncts to conventional radio- and chemotherapy. Others have proven to be modestly effective in treating neovascular eye diseases.

The new study combined the actions of three classes of angiostatic compounds, each targeting different angiogenic pathways, and showed striking results in the treatment of an animal model of glioblastoma, a highly malignant brain cancer, and ischemic retinopathy, excessive blood vessel growth in the eye that is a major cause of blindness worldwide.

"Our combination therapy reduced tumor mass and increased survival in the glioblastoma model," Friedlander said. "In models of neovascular eye diseases, the therapy resulted in complete inhibition of pathological neovascularization in more than 60 percent of the eyes; over 90 percent had greater than 75 percent inhibition of new vessel growth with no adverse affects on normal tissue vasculature. In contrast, individual therapies with comparable doses of individual drugs were minimally effective, if at all."

Importantly, Friedlander notes that the use of single therapies can result in the activation of alternative compensatory pro-angiogenic pathways designed to stimulate new vessel growth, while the combination approach significantly reduced such compensatory upregulation.

"The fact that multiple angiogenic pathways are activated in response to single therapies, but not to combination treatment, supports the hypothesis that compensatory mechanisms might prevent single angiostatics from inhibiting neovascularization," he said. "These results suggest that combination therapy prevents this natural compensation, enhancing the overall anti-angiogenesis effect."

In combination, the angiostatic therapies were effective at much lower concentrations than when used as individual monotherapies. Even when diluted up to 100-fold, the triple combination inhibited angiogenesis at levels comparable to optimal doses of any single therapy. A ten-fold dilution of the triple combination demonstrated extensive neovascular inhibition with complete inhibition observed in 44 percent of the treated retinas. At these same concentrations, the angiostatic activity of each monotherapy was negligible, indicating that combining multiple angiostatic drugs was synergistic rather than additive.

The effectiveness of combination therapies at relatively low doses may be a distinct advantage in therapy, the study noted. In the elderly or diabetic patients, high levels of circulating angiostatics could precipitate stroke or heart attack due to the fact that such patients make collateral blood vessels in hearts and brains that are starved for oxygen from vascular diseases such as arteriosclerosis, hypertension, and diabetes. For these and other patients, the use of lower doses of angiostatic therapies could minimize potential adverse side effects.

"The point of the study was to show proof-of-concept that targeting multiple angiogenic pathways will be more effective than inhibiting single ones due to potential compensatory upregulation," Friedlander said. "As more and more anti-angiogenic agents reach the market, there will be even more combinations to choose from. In our laboratory, we're now looking at new combinations of approved angiostatic drugs to see if we can achieve similar promising results that can have immediate translation into the clinic."

###

Other authors of the study, Combination Angiostatic Therapy Completely Inhibits Ocular and Tumor Angiogenesis, were Michael I. Dorrell, Edith Aguilar, Lea Scheppke, and Faith H. Barnett of The Scripps Research Institute. See: Proceedings of the National Academy of Sciences of the United States of America

The study was supported by the National Eye Institute, the Scripps Fonseca/Mericos Fund, the V. Kann Rasmussen and MacTel Foundations, and the Skaggs Scholars in Clinical Science.

About The Scripps Research Institute

The Scripps Research Institute is one of the world's largest independent, non-profit biomedical research organizations, at the forefront of basic biomedical science that seeks to comprehend the most fundamental processes of life. Scripps Research is internationally recognized for its discoveries in immunology, molecular and cellular biology, chemistry, neurosciences, autoimmune, cardiovascular, and infectious diseases, and synthetic vaccine development. Established in its current configuration in 1961, it employs approximately 3,000 scientists, postdoctoral fellows, scientific and other technicians, doctoral degree graduate students, and administrative and technical support personnel. Scripps Research is headquartered in La Jolla, California. It also includes Scripps Florida, whose researchers focus on basic biomedical science, drug discovery, and technology development. Currently operating from temporary facilities in Jupiter, Scripps Florida will move to its permanent campus in 2009.

Contact: Marisela Chevez
Scripps Research Institute

A New Target For The Treatment Of Breast Cancer:

The active ingredient in a drug currently being tested to treat rheumatoid arthritis might also one day serve as an effective means of treating one of the deadliest forms of breast cancer. Researchers with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have demonstrated that inhibiting the activity of the protease enzyme known as TACE can deprive tumor cells of a key factor needed for their proliferation. TACE is strongly present in a form of breast cancer which responds poorly to current therapies.

We have shown that inhibition of the TACE protease in breast cancer cells blocks the shedding of two critical growth factor proteins and results in an inhibition of a key signaling pathway that controls cell division," said Paraic Kenny, a post-doctoral cell biologist with the research group of Mina Bissell in Berkeley Lab's Life Sciences Division. "Based on analysis of cells grown in three-dimensional cultures, the inhibition of this protease results in the reversion of the malignant phenotype of these breast cancer cells and switches their behavior back to a phenotype very reminiscent of non-malignant breast epithelial cells."

Kenny is the co-author along with Bissell of a paper published in the Journal of Clinical Investigation entitled: Targeting TACE-Dependent EGFR-ligand Shedding in Breast Cancer. This paper presents the latest experimental results from an on-going investigation led by Bissell into the ecology of tumors.

It has long been Bissell's contention that "no tumor is an island." Tumor cells, she maintains, exist in the same microenvironment as healthy cells and must therefore appropriate normal physiological processes to facilitate their growth and spread. As she and her colleagues have repeatedly demonstrated, this idea can open up potential new avenues and targets for diagnostic and therapeutic applications.

For this latest paper, Kenny and Bissell looked into the pathway by which the EGFR signal is carried. EGFR, which stands for Epidermal Growth Factor Receptor, is the protein on the outer surface of a cell that is activated by EGF and related growth factors and signals for the cell to divide. Given that one of the hallmarks of cancer is cell division run amok, the reduction of high levels of EGFR activity has long been a primary target for anti-cancer drug development. So far, however, drugs aimed at directly inhibiting EGFR activity have met with only limited success in the cancer clinic, primarily in a small number of lung cancers.

"Because of this, we turned our attention to the processes that regulate the production of the ligands which bind and activate EGFR," Kenny said. "We reasoned that this binding and activation is essential for EGFR activation and that finding a way to block this interaction might prove to be an important additional approach to explore for inhibition of this pathway."

Earlier studies had indicated that TACE (tumor necrosis factor-alpha-converting enzyme) acts like a "molecular scissors" that releases from the cell surface a pair of ligands, called Amphiregulin and TGF-alpha, which activate EGFR. Bissell and Kenny found that by targeting TACE (also known as ADAM17) with either molecular inhibitors or short interfering RNAs (siRNAs) that silence the TACE gene, they could effectively block the shedding of Amphiregulin and TGF-alpha ligands. This resulted in the inhibition of EGFR signaling and the reversion of malignant characteristics in tumor cells. It is the first reported use of protease inhibitors to stop breast cancer cell proliferation and restore the normal breast tissue structure.

"We have designed an entirely new way of targeting EGFR signaling in breast cancer," said Kenny. "Almost all the work to date has involved the use of antibodies that stick to kinases or drugs that block kinase activities."

These newest results are very much in keeping with Bissell's contention that cancer growth and spread is not solely a tumor cell-autonomous process brought on by a genetic mutation. Bissell is one of the leading proponents of the idea that a cell's genetic information is supplemented by contextual information encoded within the microenvironment that surrounds the cell.

"It is becoming increasingly apparent that, as with other organs, the biogenesis of the tumor represents an interaction between the tumor cell, other types of cells and the rest of the microenvironment," she said.

Kenny and Bissell successfully tested their protease blocking approach on several different breast cancer cell lines. In addition, they examined the data from 295 breast cancer patients and found that tumors which produced the highest levels of TACE and the TGF-alpha ligand posed the greatest risk to women.

"Women with those types of tumors would seem to be poorly served by existing treatments and may stand to benefit from therapies that are based on the inhibition of TACE activity," said Kenny. "We would like to see some of the companies who have developed the new generation TACE inhibitors for treatment of rheumatoid arthritis also consider evaluating them in cancer patients."

Kenny stressed that the importance of EGFR to so many different tumor types, including lung, head and neck, bladder, colorectal and kidney, makes it likely that "TACE inhibition has the potential to be an effective means of stopping tumor growth for EGFR-dependent cancers outside the breast as well."

This research was supported by grants and a Distinguished Fellowship Award from the U.S. Department of Energy's Office of Biological and Environmental Research, the National Cancer Institute,and an Innovator award from the U.S. Department of Defense's Breast Cancer Research Program to Bissell, and by a Susan G. Komen Breast Cancer Foundation fellowship to Kenny.

Berkeley Lab is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research and is managed by the University of California. Visit our Website at http://www.lbl.gov/.

* For more information on the research of Mina Bissell and Paraic Kenny, please visit the Website at http://www.lbl.gov/lifesciences/BissellLab/main.html

Contact: Lynn Yarris
DOE/Lawrence Berkeley National Laboratory

Scripps Research Combination Therapy Obliterates New Vessel Growth In Tumors And Retinopathy

The paper is being published online in the Proceedings of the National Academy of Sciences.

"While a number of new drugs that inhibit new blood vessel growth are now available in the clinics, no one so far has been cured with available anti-angiogenic agents," said Professor Martin Friedlander, a Scripps Research scientist and retina specialist at Scripps Clinic who led the study. "Our study shows that combining anti-angiogenic agents that target multiple angiogenic pathways can significantly increase the effectiveness of such a therapeutic approach. Such combination angiostatic therapy provides a whole new range of treatment options for patients with neovascular diseases, where complete inhibition of new blood vessel growth is the desired result."

While new blood vessel growth from preexisting capillaries ("angiogenesis") is fundamental to survival, the abnormal formation of new blood vessels ("neovascularization") contributes to the pathogenesis of tumor growth and metastasis as well as the vast majority of diseases that lead to catastrophic loss of vision. A number of angiostatic molecules have been used to impair blood vessel formation as clinical adjuncts to conventional radio- and chemotherapy. Others have proven to be modestly effective in treating neovascular eye diseases.

The new study combined the actions of three classes of angiostatic compounds, each targeting different angiogenic pathways, and showed striking results in the treatment of an animal model of glioblastoma, a highly malignant brain cancer, and ischemic retinopathy, excessive blood vessel growth in the eye that is a major cause of blindness worldwide.

"Our combination therapy reduced tumor mass and increased survival in the glioblastoma model," Friedlander said. "In models of neovascular eye diseases, the therapy resulted in complete inhibition of pathological neovascularization in more than 60 percent of the eyes; over 90 percent had greater than 75 percent inhibition of new vessel growth with no adverse affects on normal tissue vasculature. In contrast, individual therapies with comparable doses of individual drugs were minimally effective, if at all."

Importantly, Friedlander notes that the use of single therapies can result in the activation of alternative compensatory pro-angiogenic pathways designed to stimulate new vessel growth, while the combination approach significantly reduced such compensatory upregulation.

"The fact that multiple angiogenic pathways are activated in response to single therapies, but not to combination treatment, supports the hypothesis that compensatory mechanisms might prevent single angiostatics from inhibiting neovascularization," he said. "These results suggest that combination therapy prevents this natural compensation, enhancing the overall anti-angiogenesis effect."

In combination, the angiostatic therapies were effective at much lower concentrations than when used as individual monotherapies. Even when diluted up to 100-fold, the triple combination inhibited angiogenesis at levels comparable to optimal doses of any single therapy. A ten-fold dilution of the triple combination demonstrated extensive neovascular inhibition with complete inhibition observed in 44 percent of the treated retinas. At these same concentrations, the angiostatic activity of each monotherapy was negligible, indicating that combining multiple angiostatic drugs was synergistic rather than additive.

The effectiveness of combination therapies at relatively low doses may be a distinct advantage in therapy, the study noted. In the elderly or diabetic patients, high levels of circulating angiostatics could precipitate stroke or heart attack due to the fact that such patients make collateral blood vessels in hearts and brains that are starved for oxygen from vascular diseases such as arteriosclerosis, hypertension, and diabetes. For these and other patients, the use of lower doses of angiostatic therapies could minimize potential adverse side effects.

"The point of the study was to show proof-of-concept that targeting multiple angiogenic pathways will be more effective than inhibiting single ones due to potential compensatory upregulation," Friedlander said. "As more and more anti-angiogenic agents reach the market, there will be even more combinations to choose from. In our laboratory, we're now looking at new combinations of approved angiostatic drugs to see if we can achieve similar promising results that can have immediate translation into the clinic."

###

Other authors of the study, Combination Angiostatic Therapy Completely Inhibits Ocular and Tumor Angiogenesis, were Michael I. Dorrell, Edith Aguilar, Lea Scheppke, and Faith H. Barnett of The Scripps Research Institute. See: Proceedings of the National Academy of Sciences of the United States of America

The study was supported by the National Eye Institute, the Scripps Fonseca/Mericos Fund, the V. Kann Rasmussen and MacTel Foundations, and the Skaggs Scholars in Clinical Science.

About The Scripps Research Institute

The Scripps Research Institute is one of the world's largest independent, non-profit biomedical research organizations, at the forefront of basic biomedical science that seeks to comprehend the most fundamental processes of life. Scripps Research is internationally recognized for its discoveries in immunology, molecular and cellular biology, chemistry, neurosciences, autoimmune, cardiovascular, and infectious diseases, and synthetic vaccine development. Established in its current configuration in 1961, it employs approximately 3,000 scientists, postdoctoral fellows, scientific and other technicians, doctoral degree graduate students, and administrative and technical support personnel. Scripps Research is headquartered in La Jolla, California. It also includes Scripps Florida, whose researchers focus on basic biomedical science, drug discovery, and technology development. Currently operating from temporary facilities in Jupiter, Scripps Florida will move to its permanent campus in 2009.

Contact: Marisela Chevez
Scripps Research Institute

A New Target For The Treatment Of Breast Cancer:

The active ingredient in a drug currently being tested to treat rheumatoid arthritis might also one day serve as an effective means of treating one of the deadliest forms of breast cancer. Researchers with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have demonstrated that inhibiting the activity of the protease enzyme known as TACE can deprive tumor cells of a key factor needed for their proliferation. TACE is strongly present in a form of breast cancer which responds poorly to current therapies.

We have shown that inhibition of the TACE protease in breast cancer cells blocks the shedding of two critical growth factor proteins and results in an inhibition of a key signaling pathway that controls cell division," said Paraic Kenny, a post-doctoral cell biologist with the research group of Mina Bissell in Berkeley Lab's Life Sciences Division. "Based on analysis of cells grown in three-dimensional cultures, the inhibition of this protease results in the reversion of the malignant phenotype of these breast cancer cells and switches their behavior back to a phenotype very reminiscent of non-malignant breast epithelial cells."

Kenny is the co-author along with Bissell of a paper published in the Journal of Clinical Investigation entitled: Targeting TACE-Dependent EGFR-ligand Shedding in Breast Cancer. This paper presents the latest experimental results from an on-going investigation led by Bissell into the ecology of tumors.

It has long been Bissell's contention that "no tumor is an island." Tumor cells, she maintains, exist in the same microenvironment as healthy cells and must therefore appropriate normal physiological processes to facilitate their growth and spread. As she and her colleagues have repeatedly demonstrated, this idea can open up potential new avenues and targets for diagnostic and therapeutic applications.

For this latest paper, Kenny and Bissell looked into the pathway by which the EGFR signal is carried. EGFR, which stands for Epidermal Growth Factor Receptor, is the protein on the outer surface of a cell that is activated by EGF and related growth factors and signals for the cell to divide. Given that one of the hallmarks of cancer is cell division run amok, the reduction of high levels of EGFR activity has long been a primary target for anti-cancer drug development. So far, however, drugs aimed at directly inhibiting EGFR activity have met with only limited success in the cancer clinic, primarily in a small number of lung cancers.

"Because of this, we turned our attention to the processes that regulate the production of the ligands which bind and activate EGFR," Kenny said. "We reasoned that this binding and activation is essential for EGFR activation and that finding a way to block this interaction might prove to be an important additional approach to explore for inhibition of this pathway."

Earlier studies had indicated that TACE (tumor necrosis factor-alpha-converting enzyme) acts like a "molecular scissors" that releases from the cell surface a pair of ligands, called Amphiregulin and TGF-alpha, which activate EGFR. Bissell and Kenny found that by targeting TACE (also known as ADAM17) with either molecular inhibitors or short interfering RNAs (siRNAs) that silence the TACE gene, they could effectively block the shedding of Amphiregulin and TGF-alpha ligands. This resulted in the inhibition of EGFR signaling and the reversion of malignant characteristics in tumor cells. It is the first reported use of protease inhibitors to stop breast cancer cell proliferation and restore the normal breast tissue structure.

"We have designed an entirely new way of targeting EGFR signaling in breast cancer," said Kenny. "Almost all the work to date has involved the use of antibodies that stick to kinases or drugs that block kinase activities."

These newest results are very much in keeping with Bissell's contention that cancer growth and spread is not solely a tumor cell-autonomous process brought on by a genetic mutation. Bissell is one of the leading proponents of the idea that a cell's genetic information is supplemented by contextual information encoded within the microenvironment that surrounds the cell.

"It is becoming increasingly apparent that, as with other organs, the biogenesis of the tumor represents an interaction between the tumor cell, other types of cells and the rest of the microenvironment," she said.

Kenny and Bissell successfully tested their protease blocking approach on several different breast cancer cell lines. In addition, they examined the data from 295 breast cancer patients and found that tumors which produced the highest levels of TACE and the TGF-alpha ligand posed the greatest risk to women.

"Women with those types of tumors would seem to be poorly served by existing treatments and may stand to benefit from therapies that are based on the inhibition of TACE activity," said Kenny. "We would like to see some of the companies who have developed the new generation TACE inhibitors for treatment of rheumatoid arthritis also consider evaluating them in cancer patients."

Kenny stressed that the importance of EGFR to so many different tumor types, including lung, head and neck, bladder, colorectal and kidney, makes it likely that "TACE inhibition has the potential to be an effective means of stopping tumor growth for EGFR-dependent cancers outside the breast as well."

This research was supported by grants and a Distinguished Fellowship Award from the U.S. Department of Energy's Office of Biological and Environmental Research, the National Cancer Institute,and an Innovator award from the U.S. Department of Defense's Breast Cancer Research Program to Bissell, and by a Susan G. Komen Breast Cancer Foundation fellowship to Kenny.

Berkeley Lab is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research and is managed by the University of California. Visit our Website at http://www.lbl.gov/.

* For more information on the research of Mina Bissell and Paraic Kenny, please visit the Website at http://www.lbl.gov/lifesciences/BissellLab/main.html

Contact: Lynn Yarris
DOE/Lawrence Berkeley National Laboratory

New England Journal Of Medicine Publishes Study Identifying A Tumorigenic Cancer Cell Gene Signature That Appears Predictive Of Clinical Outcomes

OncoMed Pharmaceuticals, a company developing novel therapeutics that target cancer stem cells, today announced the publication in the New England Journal of Medicine of the discovery of a novel gene expression signature associated with tumorigenic breast cancer cells, also known as cancer stem cells. Cancer stem cells, a small subset of cells found in solid tumors, have the capacity to self-renew and differentiate, initiate tumors and drive tumor growth, recurrence and metastasis. Researchers found that the gene expression signature is highly correlated with clinical outcomes in patients with breast cancer and certain other types of solid tumors. The study, titled "The Prognostic Role of a Gene Signature from Tumorigenic Breast Cancer Cells," was conducted collaboratively by researchers at OncoMed Pharmaceuticals, the University of Michigan and Stanford University, including the lab of OncoMed co-founder Michael Clarke, MD, currently Deputy Director of the Stanford Institute for Stem Cell Biology and Regenerative Medicine.

The data published today describes a set of 186 specific genes, dubbed, the "invasiveness" gene signature or IGS, that are differentially expressed in tumorigenic cells relative to normal breast tissue. Using breast cancer patient information from the Netherlands Cancer Institute and the Erasmus Medical Center, two large published gene expression and clinical databases, study authors evaluated the relationship between the IGS and patient outcomes. Researchers found that among patients whose tumor gene expression profiles correlated to the IGS, there was a statistically significant increase in risks of breast cancer metastasis and reduced survival rates. The predictive power of the IGS was independent of established clinical and pathological criteria, such as tumor size, lymph node status, histologic grade and estrogen receptor status. In addition, researchers found that the IGS was also predictive of clinical outcomes in individuals with prostate cancer, lung cancer and medulloblastoma. These findings suggest that this cancer stem cell gene signature may be used to identify patients at the highest risk for disease recurrence and metastasis. A series of patent applications were filed by OncoMed and the University of Michigan covering this discovery and its potential applications and are owned by or licensed to OncoMed.

"We are excited about these data and their potential application to the diagnosis and treatment of cancer. The newly identified 186 cancer stem cell gene signature was observed to be highly predictive of breast cancer, independent of other factors typically used to forecast a patient's prognosis," said John Lewicki, PhD, Senior Vice President Research and Development of OncoMed Pharmaceuticals. "Interestingly, we found that the gene signature appeared to correlate to the risk of death and metastasis for multiple tumor types, demonstrating the central importance of cancer stem cells in the recurrence and progression of solid tumors."

"This study published in today's New England Journal of Medicine further adds to the substantial body of data establishing the central role of cancer stem cells in tumor growth, recurrence and metastases," said Paul Hastings, OncoMed's President and Chief Executive Officer. "We believe the discovery of a novel tumorigenic gene expression signature may prove important in identifying patients at highest risk and selecting those individuals most likely to respond to therapies, including cancer stem cell-directed treatments."

In another aspect of the work reported today, when the tumorigenic stem cell signature was combined with a 512-gene wound response signature previously published by Stanford University investigators, the resulting data were even more significant in predicting a patient's outcome, thus pointing to a potential dependency between cancer stem cells and their surrounding tumor environment.

About OncoMed Pharmaceuticals

OncoMed Pharmaceuticals is discovering and developing novel therapeutics targeting cancer stem cells, the cells believed to be capable of driving tumor growth, recurrence and metastases. The company has established a library of antibodies to cancer stem cell proteins for the treatment of solid tumors such as breast, colon, prostate, and lung cancers. The company is a leader in cancer stem cell research and the identification of novel cancer stem cell targets.

OncoMed's investors include Latterell Venture Partners, US Venture Partners, Morgenthaler Ventures, the Vertical Group, Adams Street Partners, DeNovo Ventures, and Bay Partners. Information can also be found at the company's website http://www.oncomed.com/.

OncoMed Pharmaceuticals
http://www.oncomed.com/

Peregrine Pharmaceuticals' Tumor Necrosis Therapy Product For The Treatment Of Lung Cancer Launched In China

Peregrine Pharmaceuticals, Inc. (Nasdaq: PPHM), a clinical stage biopharmaceutical company developing targeted therapeutics for the treatment of cancer and hepatitis C virus (HCV) infection, today reported that Shanghai Medipharm Biotech (Medipharm) has launched an iodine-131 radiolabeled Tumor Necrosis Therapy (TNT) antibody for the treatment of lung cancer in the People's Republic of China. The new drug is part of Peregrine's proprietary TNT technology platform that also includes its investigational drug Cotara(R). Peregrine is currently conducting Phase II clinical trials of Cotara as a treatment for malignant brain cancer in the U.S. and India.

According to clinical data reported by Medipharm in 2003, a registration study of advanced lung cancer patients in China demonstrated that Peregrine's radiolabeled TNT agent provided encouraging signs of patient benefit. Of the patients treated in the study, almost 4% experienced complete remissions, almost 31% had partial remissions involving at least 50% shrinkage of their tumors, 55% had their disease stabilized (representing no change in the tumor mass), and about 10% reported progressive disease. Responses to the therapy were defined according to the World Health Organization criteria for measuring solid tumors and confirmation of responses was obtained by using thoracic radiograph and computer tomography.

"The market launch of this TNT anti-cancer agent in China is a signal event further validating the potential clinical utility of Peregrine's TNT technology," said Steven W. King, president and CEO of Peregrine. "This development is especially positive since lung cancer is a major and growing health issue in China. This launch is also timely since Peregrine has recently established a wholly owned subsidiary in China where we plan to pursue product development and commercialization activities on our own and in collaboration with Chinese biopharmaceutical partners."

Peregrine had licensed certain rights to the company's TNT technology platform for development and commercialization in China exclusively to Cancer Therapeutics Laboratories, Inc. (CTL), which has a purported sublicense arrangement with Medipharm, the Chinese company developing and launching the new TNT drug for lung cancer. Peregrine recently filed a lawsuit against CTL alleging various breaches of contract following repeated attempts by Peregrine to obtain adequate information concerning the purported agreement. Peregrine will pursue its remedies under the lawsuit while it explores its options in China regarding other avenues for commercialization for its TNT technology platform.

Peregrine recently announced that it had established a wholly foreign-owned enterprise (WFOE) in the People's Republic of China. The new subsidiary, Peregrine Beijing Pharmaceuticals Technology Development Ltd., is expected to engage in a variety of drug development and commercialization activities.

Peregrine's proprietary Tumor Necrosis Therapy (TNT) approach links a radioactive isotope to a targeted monoclonal antibody that is designed to bind to a type of DNA that is exposed only on dead and dying cells. Solid tumors have a significant number of dead and dying cells at their center and the TNT agent's targeting mechanism enables it to home in on these dying tumor cells, delivering its radioactive "payload" directly to the center of the tumor mass. TNT agents thus literally destroy the tumor "from the inside out" with minimal radiation exposure to healthy tissue. Peregrine's TNT agent Cotara is currently in a multi-center trial in the U.S. for the treatment of glioblastoma multiforme (GBM) in collaboration with New Approaches to Brain Tumor Therapy (NABTT), a consortium of leading U.S. academic brain cancer centers. Peregrine has also received regulatory approval to initiate a Phase II Cotara trial for the treatment of GBM in India pending manufacturing clearance in that country. Cotara has been granted orphan drug status and fast track designation by the U.S. Food and Drug Administration for the treatment of GBM.

About Peregrine Pharmaceuticals

Peregrine Pharmaceuticals, Inc. is a biopharmaceutical company with a portfolio of innovative product candidates in clinical trials for the treatment of cancer and hepatitis C virus (HCV) infection. The company is pursuing five separate clinical trials in cancer and HCV infection in the U.S. and India with its lead product candidates bavituximab and Cotara(R). Peregrine also has in-house manufacturing capabilities through its wholly owned subsidiary Avid Bioservices, Inc. (http://www.avidbio.com), which provides development and bio-manufacturing services for both Peregrine and outside customers. Additional information about Peregrine can be found at http://www.peregrineinc.com.

Safe Harbor Statement: Statements in this press release which are not purely historical, including statements regarding Peregrine Pharmaceuticals' intentions, hopes, beliefs, expectations, representations, projections, plans or predictions of the future are forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. The forward-looking statements involve risks and uncertainties including, but not limited to, the risk that Medipharm will not be able to successfully market the drug or that the drug will not gain market acceptance in China, and the uncertainty of Peregrine's rights with respect to the sale of the drug by Medipharm in China. It is important to note that the company's actual results could differ materially from those in any such forward-looking statements. Factors that could cause actual results to differ materially include, but are not limited to, uncertainties associated with completing preclinical and clinical trials for our technologies; the early stage of product development; the significant costs to develop our products as all of our products are currently in development, preclinical studies or clinical trials; obtaining additional financing to support our operations and the development of our products; obtaining regulatory approval for our technologies; anticipated timing of regulatory filings and the potential success in gaining regulatory approval and complying with governmental regulations applicable to our business. Our business could be affected by a number of other factors, including the risk factors listed from time to time in the Company's SEC reports including, but not limited to, the annual report on Form 10-K for the year ended April 30, 2006, and the quarterly report on Form 10-Q for the quarter ended October 31, 2006. The Company cautions investors not to place undue reliance on the forward-looking statements contained in this press release. Peregrine Pharmaceuticals, Inc. disclaims any obligation, and does not undertake to update or revise any forward-looking statements in this press release.

Peregrine Pharmaceuticals, Inc.
http://www.peregrineinc.com

Brain Tumor Researchers Find Their "Niche"

Brain tumors appear to arise from cancer stem cells (CSCs) that live within microscopic protective "niches" formed by blood vessels in the brain; and disrupting these niches is a promising strategy for eliminating the tumors and preventing them from re-growing, according to results of a study by investigators at St. Jude Children's Research Hospital. CSCs are cells that continually multiply, acting as the source of tumors.

"The finding that brain CSCs exist in protective vascular (blood vessel) niches helps explain the origin of brain tumors and suggests a new strategy for eliminating them," said Richard Gilbertson, M.D., Ph.D., co-director of the Neurobiology and Brain Tumor Program at St. Jude. Gilbertson is senior author of a report on this work that appears in the January issue of Cancer Cell.

"Our data indicate that brain CSCs are nurtured by these vascular niches and that disrupting them blocks tumor growth by removing CSCs from tumors," he said. "These niches might also protect CSCs from chemotherapy drugs and irradiation therapy. So our findings could explain why aggressive tumors rapidly produce new blood vessels and why brain tumors reappear following treatment."

The St. Jude team first determined that CSCs are located in vascular niches by identifying cells carrying a protein called Nestin that marks stem cells (Nestin+ cells) in four types of brain cancer removed from patients: medulloblastoma, ependymoma, oligodendroglioma and glioblastoma. They found that tumors with the densest system of tiny blood vessels contained the greatest number of Nestin+ cells, and that Nestin+ cells are located next to blood vessels in brain tumors.

The investigators then examined thin sections of brain tumors and found that more than one-third of the Nestin+ cells next to blood vessels in the vascular niches had a mutation known to be linked to cancer, which suggested they were CSCs, Gilbertson said. About 30 percent of these cells were multiplying abnormally and rapidly, as expected for cancer cells.

The team showed in mouse models that CSCs from brain tumors have a more natural tendency to associate closely with blood vessels than do non-CSC tumor cells. The researchers also demonstrated in test tube experiments that CSCs bind closely to cells isolated from human blood vessels. Further, the investigators found that human blood vessel cells release molecules that trigger brain CSCs to keep their identity as stem cells and continue to multiply rapidly.

"This is strong evidence that the cells making up the vascular niche send signals to CSCs in the brain, causing them to grow and multiply," Gilbertson said.

Gilbertson's team also studied the interaction of blood vessel cells with CSCs using mouse models of brain cancer. Mixing brain CSCs with human blood vessel cells dramatically increased the formation and growth of tumors. Brain CSCs inserted into the brain without human blood vessel cells produced tumors slowly, reaching a maximum size after seven weeks. In contrast, tumors formed by mixtures of brain CSCs and blood vessel cells grew much more rapidly, reaching a maximum growth after only four weeks. The blood vessel cells did not increase tumor growth by forming new vessels, but by associating with CSCs and stimulating these directly to produce tumors.

Finally, the investigators showed that increasing the numbers of blood vessels in mouse models of brain tumors markedly increased the numbers of CSCs in tumors. The scientists also showed that drugs that deplete blood vessels from tumors inhibit tumor growth by reducing the number of CSCs. For example, the team depleted blood vessels in tumors with Avastin® (bevacizumab), an anti-angiogenic drug that blocks a protein called VEGF. Anti-angiogenic drugs block the formation of new blood vessels.

"This strongly suggests that disrupting the blood vessels in brain tumors might block tumor growth by disrupting brain CSC niches," Gilbertson said. "This is important since the mechanism by which anti-angiogenic drugs, like Avastin, block tumor growth is largely unknown. Our data suggest a previously unrecognized way that anti-angiogenic agents inhibit tumor growth."

The St. Jude investigators have now translated these findings into a clinical trial to determine the effectiveness of Avastin and another drug, Traceva® (erlotinib), in eliminating tumors and preventing their recurrence in children with brain cancers.

The other authors of this study include Christopher Calabrese, Helen Poppleton, Mehmet Kocak, Twala L. Hogg, Christine Fuller, Blair Hamner, Eun Y. Oh, M. Waleed Gaber, David Finklestein, Meredith Allen, Adrian Frank, Ildar T. Bayazitov, Stanislav S. Zakharenko, Amar Gajjar and Andrew Davidoff.

This work was supported in part by the Sontag Foundation, The National Cancer Institute, the V Foundation for Cancer Research and ALSAC.

St. Jude Children's Research Hospital

St. Jude Children's Research Hospital is internationally recognized for its pioneering work in finding cures and saving children with cancer and other catastrophic diseases. Founded by late entertainer Danny Thomas and based in Memphis, Tenn., St. Jude freely shares its discoveries with scientific and medical communities around the world. No family ever pays for treatments not covered by insurance, and families without insurance are never asked to pay. St. Jude is financially supported by ALSAC, its fund-raising organization. For more information, please visit http://www.stjude.org.

St. Jude Children's Research Hospital
332 N. Lauderdale St., Mail Stop 761
Memphis, TN 38122
United States
http://www.stjude.org

Vascular Niche Nurtures Brain Tumor Stem Cells

Self-renewing cancer stem cells (CSCs) comprise only a tiny fraction of most brain tumors, but eliminating them is likely to have a profound impact on the ability of a tumor to survive and grow. However, CSCs might resist traditional therapies that target the great bulk of the cells in cancers. Now, new research published in the January 2007 issue of the journal Cancer Cell, published by Cell Press, reveals that small blood vessels associated with brain tumors orchestrate a distinct microenvironment that is critical for maintaining CSCs. Importantly, antiangiogenic drugs that disrupt this microenvironment reduce the CSC population and arrest tumor growth.

Dr. Richard J. Gilbertson and colleagues from the St. Jude Children's Research Hospital established that CSCs in human brain tumors are associated with blood vessels and that vascular cells physically interact with and maintain brain CSCs in culture. A similar interaction was not observed for the bulk of non-CSC tumor cells. To examine whether the vessel-derived factors promote maintenance of CSCs and tumor propagation in vivo, the researchers transplanted human brain tumors into mice with or without vascular cells. The mice with extra vascular cells exhibited an increase in CSCs as well as enhanced initiation and proliferation of tumors. The authors also found that when antiangiogenic therapies were used to diminish tumor blood vessels, CSCs were reduced and tumor growth was arrested, further supporting the importance of the vascular microenvironment to CSCs.

"Our data identify a possible role for niche microenvironments in the maintenance of CSCs and identify a mechanism by which antiangiogenic drugs inhibit brain tumor growth," concludes Dr. Gilbertson. "If the notion that niches protect CSCs proves correct, then targeting these microenvironments could prove highly effective treatments of cancer." Further research and clinical trials are needed to investigate this important new mechanism associated with antiangiogenic cancer therapies. It seems likely that effective cancer treatments must target both the bulk of rapidly proliferating tumor cells and the smaller population of self-renewing CSCs.

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The researchers include Christopher Calabrese, Helen Poppleton, Mehmet Kocak, Twala L. Hogg, Christine Fuller, Blair Hamner, Eun Young Oh, M. Waleed Gaber, David Finklestein, Meredith Allen, Adrian Frank, Ildar T. Bayazitov and Stanislav S. Zakharenko, Amar Gajjar, Andrew Davidoff and Richard J. Gilbertson of St. Jude Children's Research Hospital in Memphis, TN.

This work was supported by the Sontag Foundation (R.J.G.), NCI grant CA096832 (R.J.G.), the V-Foundation for Cancer Research (R.J.G.), and the American Lebanese Syrian Associated Charities (ALSAC).

Calabrese et al.: "A Perivascular Niche for Brain Tumor Stem Cells." Publishing in Cancer Cell 11, 69-82, January 2007. DOI 10.1016/j.ccr.2006.11.020 http://www.cancercell.org/

Contact: Erin Doonan
Cell Press

Chemical Switch Triggers Critical Cell Activities

St. Jude study shows simple thioester chemical bond acts like a switch that activates protein movements among three enzymes, triggering specific, critical biochemical activities inside the cell

The freeze-frame image of a molecular relay race, in which one enzyme passes off a protein like a baton to another enzyme, has solved a key mystery to how cells control some vital functions, according to investigators at St. Jude Children's Research Hospital. A report on this work appears in the advanced online publication issue of Nature.

The St. Jude discovery explains how a simple chemical link between molecules called a thioester bond acts like a switch to control the handoff of a protein called NEDD8 like a baton from one enzyme called E1 to a second enzyme called E2. When attached to E2, this thioester bond allows E2 to bind to a third enzyme called E3, which then helps E2 hand NEDD8 off to the ultimate target molecule at the end of the race. In the cell, this NEDD8 relay race triggers a number of biochemical reactions, one of which takes the brakes off cell division, allowing cells to multiply, according to the researchers. These thioester bonds are chemical links between two biological molecules that form when a sulfur atom on one of the molecules binds to an atom that is part of the other molecule.

Understanding how the thioester bond switch works is important not only because it explains a critical step in the NEDD8 hand-off from E1 to E2, but also because enzymes related to E1 and E2 run similar relays with other important protein batons, said Brenda Schulman, Ph.D., associate member of the St. Jude Structural Biology and Genetics and Tumor Cell Biology departments. "Our study shows that this simple switch could control comparable relays in charge of several different biochemical activities that keep cells alive and functioning normally." Schulman, a Howard Hughes Medical Institute (HHMI) investigator, is senior author of the Nature report.

Scientists already knew that E1 momentarily juggles two NEDD8 molecules at once, holding them in two different "hands." They also knew that E2 takes the NEDD8 that is in E1's left hand; and that the other NEDD8 then hops over from the right hand to E1's empty left hand. That leaves the right hand free to grab yet another NEDD8. By continually passing the NEDD8 proteins from the right hand to the left hand and on to E2, E1 keeps a relay of these batons flowing. In turn, that keeps the specific biochemical cascade triggered by NEDD8 in action.

But in order for the handoff to work, E2 must first insert itself into a docking site on E1, next to E1's left hand, so it can grab NEDD8, Schulman explained. However, the E2 docking site is initially turned away from E1: so if E2 hopped into the docking site at that point, it would be too far away from NEDD8 to grab it, she noted. And that was the puzzle the St. Jude researchers solved.

Specifically, the St. Jude study showed that when NEDD8 forms a thioester bond with E1's left hand, it squeezes itself next to the E2 docking site, which is facing away from NEDD8, according to Danny Huang, Ph.D., HHMI postdoctoral research associate and Harold Hunt, HHMI research technologist,. These researchers in Schulman's laboratory did most of the work on this project.

In such close quarters, NEDD8 bumps the docking site, making it rotate like the paddle wheel on a riverboat that carries a notch on one of its paddles. As the docking site rotates, it carries the notch all the way around to the other side, next to NEDD8. As soon as the notch of the docking site is next to NEDD8, the notch catches E2, so E2 is bound to the notch, right next to NEDD8. NEDD8 then breaks its thioester bond with E1 and reforms it with E2. As soon as NEDD8 breaks its thioester bond to E1 and forms a thioester bond with E2 instead, E2 falls away from E1 taking NEDD8 with it. Then E2 can interact with E3 to pass NEDD8 onto the target.

The investigators were able to make sense of this combination of relay race and rotating paddle wheel by using a technique called X-ray crystallography. In X-ray crystallography, scientists bombard crystals of proteins with X-rays and use the patterns formed by beams bouncing off the crystals to create computer-generated 3-D images of the molecules.

The goal was to create a freeze-frame image that captured the fleeting moment when E2 is next to NEDD8, just before it falls off and carries NEDD8 with it. To do that, Schulman's team first had to prevent E2 from binding with NEDD8, so it would not fall away from E1. The investigators used a mutated form of E2 that binds to the docking site and gets near NEDD8, but cannot form a thioester bond with it. The team reasoned that if E2 could not bind to NEDD8, it would be stuck on the docking site with nothing to do and nowhere to go. An X-ray crystallography image could then capture that moment.

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Schulman's team previously published in Nature their discovery of how E1 juggles E2 and NEDD8 batons (http://www.stjude.org/media/0,2561,453_2137_3985,00.html); and followed that report with one in Nature Structural & Molecular Biology, detailing how a molecular tail on E2 stabilizes the brief combination of that enzyme with E1 (http://www.stjude.org/media/0,2561,453_5297_12275,00.html).

The other authors of this report include Min Zhuang (St. Jude and University of Tennessee); Melanie D. Ohi (Harvard Medical School, Boston, Mass.); and James M. Holton, Lawrence Berkeley National Laboratory, University of California, Berkeley, Calif).

This work was supported in part by ALSAC, the National Institutes of Health and the Charles A. King Medical Foundation.

St. Jude Children's Research Hospital

St. Jude Children's Research Hospital is internationally recognized for its pioneering work in finding cures and saving children with cancer and other catastrophic diseases. Founded by late entertainer Danny Thomas and based in Memphis, Tenn., St. Jude freely shares its discoveries with scientific and medical communities around the world. No family ever pays for treatments not covered by insurance, and families without insurance are never asked to pay. St. Jude is financially supported by ALSAC, its fund-raising organization. For more information, please visit http://www.stjude.org/.

Contact: Summer Freeman
St. Jude Children's Research Hospital

Brain Tumor Researchers Find Their 'niche'

Demonstration by St. Jude researchers that special niches made of capillaries protect and stimulate cancer stem cells in the brain explains the origin of these cancers and their reappearance following treatment

Brain tumors appear to arise from cancer stem cells (CSCs) that live within microscopic protective "niches" formed by blood vessels in the brain; and disrupting these niches is a promising strategy for eliminating the tumors and preventing them from re-growing, according to results of a study by investigators at St. Jude Children's Research Hospital. CSCs are cells that continually multiply, acting as the source of tumors.

"The finding that brain CSCs exist in protective vascular (blood vessel) niches helps explain the origin of brain tumors and suggests a new strategy for eliminating them," said Richard Gilbertson, M.D., Ph.D., co-director of the Neurobiology and Brain Tumor Program at St. Jude. Gilbertson is senior author of a report on this work that appears in the January issue of Cancer Cell.

"Our data indicate that brain CSCs are nurtured by these vascular niches and that disrupting them blocks tumor growth by removing CSCs from tumors," he said. "These niches might also protect CSCs from chemotherapy drugs and irradiation therapy. So our findings could explain why aggressive tumors rapidly produce new blood vessels and why brain tumors reappear following treatment."

The St. Jude team first determined that CSCs are located in vascular niches by identifying cells carrying a protein called Nestin that marks stem cells (Nestin+ cells) in four types of brain cancer removed from patients: medulloblastoma, ependymoma, oligodendroglioma and glioblastoma. They found that tumors with the densest system of tiny blood vessels contained the greatest number of Nestin+ cells, and that Nestin+ cells are located next to blood vessels in brain tumors.

The investigators then examined thin sections of brain tumors and found that more than one-third of the Nestin+ cells next to blood vessels in the vascular niches had a mutation known to be linked to cancer, which suggested they were CSCs, Gilbertson said. About 30 percent of these cells were multiplying abnormally and rapidly, as expected for cancer cells.

The team showed in mouse models that CSCs from brain tumors have a more natural tendency to associate closely with blood vessels than do non-CSC tumor cells. The researchers also demonstrated in test tube experiments that CSCs bind closely to cells isolated from human blood vessels. Further, the investigators found that human blood vessel cells release molecules that trigger brain CSCs to keep their identity as stem cells and continue to multiply rapidly.

"This is strong evidence that the cells making up the vascular niche send signals to CSCs in the brain, causing them to grow and multiply," Gilbertson said.

Gilbertson's team also studied the interaction of blood vessel cells with CSCs using mouse models of brain cancer. Mixing brain CSCs with human blood vessel cells dramatically increased the formation and growth of tumors. Brain CSCs inserted into the brain without human blood vessel cells produced tumors slowly, reaching a maximum size after seven weeks. In contrast, tumors formed by mixtures of brain CSCs and blood vessel cells grew much more rapidly, reaching a maximum growth after only four weeks. The blood vessel cells did not increase tumor growth by forming new vessels, but by associating with CSCs and stimulating these directly to produce tumors.

Finally, the investigators showed that increasing the numbers of blood vessels in mouse models of brain tumors markedly increased the numbers of CSCs in tumors. The scientists also showed that drugs that deplete blood vessels from tumors inhibit tumor growth by reducing the number of CSCs. For example, the team depleted blood vessels in tumors with Avastin® (bevacizumab), an anti-angiogenic drug that blocks a protein called VEGF. Anti-angiogenic drugs block the formation of new blood vessels.

"This strongly suggests that disrupting the blood vessels in brain tumors might block tumor growth by disrupting brain CSC niches," Gilbertson said. "This is important since the mechanism by which anti-angiogenic drugs, like Avastin, block tumor growth is largely unknown. Our data suggest a previously unrecognized way that anti-angiogenic agents inhibit tumor growth."

The St. Jude investigators have now translated these findings into a clinical trial to determine the effectiveness of Avastin and another drug, Traceva® (erlotinib), in eliminating tumors and preventing their recurrence in children with brain cancers.

###

The other authors of this study include Christopher Calabrese, Helen Poppleton, Mehmet Kocak, Twala L. Hogg, Christine Fuller, Blair Hamner, Eun Y. Oh, M. Waleed Gaber, David Finklestein, Meredith Allen, Adrian Frank, Ildar T. Bayazitov, Stanislav S. Zakharenko, Amar Gajjar and Andrew Davidoff.

This work was supported in part by the Sontag Foundation, The National Cancer Institute, the V Foundation for Cancer Research and ALSAC.

St. Jude Children's Research Hospital St. Jude Children's Research Hospital is internationally recognized for its pioneering work in finding cures and saving children with cancer and other catastrophic diseases. Founded by late entertainer Danny Thomas and based in Memphis, Tenn., St. Jude freely shares its discoveries with scientific and medical communities around the world. No family ever pays for treatments not covered by insurance, and families without insurance are never asked to pay. St. Jude is financially supported by ALSAC, its fund-raising organization. For more information, please visit http://www.stjude.org/.

Contact: Summer Freeman
St. Jude Children's Research Hospital

New Angiogenesis Inhibitor Has Promise For Treating Deadly Brain Tumor

Researchers from the Massachusetts General Hospital (MGH) Cancer Center have found that AZD2171 (RECENTIN(tm)), a new angiogenesis inhibitor, can significantly reduce the size of the deadly brain tumors called glioblastomas and has the potential of improving the effectiveness of other therapeutic techniques. The Phase 2 clinical trial also finds that AZD2171 treatment can alleviate brain swelling (edema), a debilitating symptom in many brain cancer patients that currently can be treated only with steroid drugs. Appearing in the January 2007 issue of Cancer Cell, the study is too preliminary to determine whether this new drug may have an impact on overall patient survival.

"Patients with recurrent glioblastomas desperately need new, effective treatment alternatives," says Tracy Batchelor, MD, chief of Neuro-Oncology in the MGH Cancer Center, the study's lead author. "While these are preliminary results of an initial trial, it's looking like these agents may play an increasingly important role in the treatment of patients whose tumors have recurred and perhaps in newly diagnosed patients as well."

Glioblastoma is the most malignant form of brain tumor and has a very poor prognosis. Standard treatments - including surgery, chemotherapy and radiation therapy - may delay tumor growth, but patients usually survive for little more than a year. There are currently no effective options for patients whose tumors recur, the vast majority of whom die within 6 months.

Angiogenesis inhibitors suppress the growth of blood vessels supplying a tumor and have received a lot of attention as potential cancer-fighting agents. While the earliest clinical trials did not meet expectations that these drugs would 'starve' tumors, the agents did improve patient survival when combined with traditional anticancer therapies. Three such drugs have received FDA approval for the treatment of certain tumors, and several others are under investigation. An oral medication, AZD2171 is a potent inhibitor of the three primary receptors for the powerful angiogenesis factor VEGF, known be present on glioblastoma blood vessels. Manufactured by AstraZeneca, AZD2171 is currently available only to participants in clinical trials.

The MGH trial, sponsored by the National Cancer Institute, was designed to assess whether AZD2171 could benefit patients with recurrent glioblastomas and also if the drug might normalize tumor vasculature. Blood vessels that develop around and within tumors are leaky and disorganized, potentially blocking the delivery of chemotherapy drugs or the effectiveness of radiation therapy, which requires an adequate supply of oxygen to the tumor. The fact that combining angiogenesis inhibitors with other therapies improved survival for some patients supports a theory developed by Rakesh Jain, PhD, director of the Steele Laboratory in the MGH Department of Radiation Oncology, that the agents temporarily 'normalize' blood vessels, creating a period during which chemotherapy and radiation treatment can be more effective. Jain is the senior author of the Cancer Cell article.

The paper reports on the first 16 patients to enter the clinical trial, which began in January 2006. All had glioblastomas that had resumed growing despite prior radiation or chemotherapy. Participants took a daily oral dose of AZD2171, which started at 45 mg and could be reduced in those experiencing negative side effects, including fatigue, diarrhea and hypertension. Participants were followed with regular physical, neurological, and MR imaging exams during the 6-month study period.

Imaging studies showed that tumors began to shrink in most participants within 28 days of the initial AZD2171 dose. Overall, the tumors shrank by at least 25 percent in three-quarters of the study participants and by 50 percent or more in half of the patients. Factors indicating a normalization of the tumors' blood vessels - including reduction in size and a decrease in permeability or 'leakiness' - were seen almost immediately in most participants and continued for at least 28 days, with some features persisting up to four months. These results are the first to define how long the period of vascular normalization might last, which may establish a window of time during which applying additional therapies would be most effective.

The highly advanced MR imaging techniques used in this report, developed at MGH, showed the vascular normalization to be very rapid, beginning after the first dose in some patients. Other MGH-pioneered MRI techniques showed that AZD2171 treatment led to a rapid decrease in brain edema, an effect that continued as long as the medication was taken. Edema produces many of the symptoms experienced by brain tumor patients and can only be treated with steroids, which have negative side effects of their own. The alleviation of edema allowed several study participants to reduce or even discontinue steroid treatment.

Analysis of potential biomarkers - molecular and cellular factors that can be measured in the blood - identified several that may indicate when the period of vascular normalization is ending or which patients' tumors are most likely to become resistant to AZD2171 treatment. These findings suggest that the imaging and biomarker studies will be important scientific tools for future assessment of therapy with AZD2171 and other drugs.

"This small group of patients needs to be followed for a longer period of time, but we are cautiously optimistic that this trial and future studies will lead to positive long-term outcomes for some patients," says Jain. He is the Cook Professor of Radiation Oncology at Harvard Medical School, where Batchelor is an associate professor of Neurology. The researchers expect that the complete results of this trial, which enrolled a total of 31 patients, will be available later this year. They also are exploring additional trials to further define the role of AZD2171 in glioblastoma treatment and hope to study the drug in combination with traditional therapies and in newly diagnosed patients.

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A. Gregory Sorensen, MD, codirector of the Martinos Center for Biomedical Imaging at MGH, is the co-lead author of the Cancer Cell report. Additional co-authors are Emmanuelle Di Tomaso, PhD, Wei-Ting Zhang, MD, Dan Duda, DMD, PhD, Kenneth Cohen, MD, Kevin Kozak, MD, PhD, Daniel Cahill, MD, Poe-Jou Chen, Mingwang Zhu, Marek Ancukiewicz, PhD, Maciej Mrugala, MD, PhD, Scott Plotkin, MD, PhD, David N. Louis, MD, David T. Scadden, MD, Thomas Benner, PhD, and Jay Loeffler, MD, of the MGH; Jan Drappatz, MD, and Patrick Y. Wen, MD, Dana-Farber Cancer Institute; and Percy Ivy, MD, National Cancer Institute. The study was supported by grants from the National Cancer Institute, the Simches Endowment for Brain Tumor Research, the Montesi Family Fund, the National Center for Research Resources, the MIND Institute and an AACR-Genentech BioOncology Career Development Award.

An integral part of one of the world's most distinguished medical centers, the Massachusetts General Hospital Cancer Center is chosen by more cancer patients than any other hospital in New England. Known for providing individualized, compassionate care to both adults and children, the MGH Cancer Center is comprised of 16 fully integrated, multidisciplinary clinical programs and a vast network of support and educational services. Scientific investigations are conducted as part of the largest hospital-based research program in the United States, and a powerful synergy between physicians and laboratory scientists fosters innovation in basic, translational and clinical research. The MGH is consistently ranked as one of the best cancer treatment centers and among the top three neurological centers by US News and World Report; and MGH nurses were the first in the state to achieve Magnet status for exceptional nursing care.

Contact: Sue McGreevey
Massachusetts General Hospital

Stem Cells Cultured From Human Bone Marrow Behave Like Those Derived From Brain Tissue

Stem cells taken from adult human bone marrow have been manipulated by scientists at the Maxine Dunitz Neurosurgical Institute at Cedars-Sinai Medical Center to generate aggregates of cells called spheres that are similar to those derived from neural stem cells of the brain.

In addition, the bone marrow-derived stem cells, which could be differentiated into neurons and other cells making up the central nervous system, spread far and wide and behaved like neural stem cells when transplanted into the brain tissue of chicken embryos.

Results of the experiments, described in the February 2007 of the Journal of Neuroscience Research, support the concept of using bone marrow-derived stem cells to create therapies to treat brain tumors, strokes and neurodegenerative diseases. A similar study using bone marrow-derived stem cells of rats appeared as the cover article of the December 2002 issue of Experimental Neurology.

"These findings reinforce the data that came from our study of rat bone marrow-derived stem cells," said John S. Yu, M.D., neurosurgeon, co-director of the Comprehensive Brain Tumor Program, and senior author of both articles. "Using two methods, we show evidence for the bone marrow-derived stem cells being neural cells, and we demonstrate that it is feasible to grow the cells in large numbers. We also document that these cells function electrophysiologically as neurons, using similar voltage-regulating mechanisms."

Progressing from the rat study to experiments with human cells and transplantation into mammal brain tissue, the research team continues to build a foundation for translating laboratory research into human clinical trials.

"Based on our studies to date, a patient's own bone marrow appears to offer a viable and renewable source of neural stem cells, allowing us to avoid many of the issues related to other types of stem cells," said Keith L. Black, M.D., director of the Maxine Dunitz Neurosurgical Institute and chairman of Cedars-Sinai's Department of Neurosurgery.

The replacement of damaged brain cells with healthy cells cultured from stem cells is considered to potentially be a promising therapy for the treatment of stroke, neurodegenerative disorders and even brain tumors, but finding a reliable source for generating neural cells for transplantation has been a challenge. The use of embryonic and fetal tissue has raised ethical questions among some, and brings with it the possibility of immune rejection. And while neural stem cells can be taken from brain tissue, the removal of healthy tissue from a patient's brain introduces a new set of safety, practicality and ethical issues.

In their recent work, the Cedars-Sinai researchers documented that several genes that speed up and control the proliferation process could be used to rapidly expand the supply of marrow-derived neural stem cells, writing in the article that "this novel method of expansion … may prove to be useful in the design of novel therapeutics for the treatment of brain disorders, including tumors."

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The study was supported by grants from the National Institutes of Health.

Citation: Journal of Neuroscience Research, Feb. 2007, "Manipulation of proliferation and differentiation of human bone marrow derived neural stem cells in vitro and in vivo"

One of seven hospitals in California whose nurses have been honored with the prestigious Magnet designation, Cedars-Sinai Medical Center is one of the largest nonprofit academic medical centers in the Western United States. For 19 consecutive years, it has been named Los Angeles' most preferred hospital for all health needs in an independent survey of area residents. Cedars-Sinai is internationally renowned for its diagnostic and treatment capabilities and its broad spectrum of programs and services, as well as breakthroughs in biomedical research and superlative medical education. It ranks among the top 10 non-university hospitals in the nation for its research activities and is fully accredited by the Association for the Accreditation of Human Research Protection Programs, Inc. (AAHRPP). Additional information is available at http://www.cedars-sinai.edu/.

Contact: Sandy Van
Cedars-Sinai Medical Center