Genetic Fingerprints Identify Brain Tumors' Origins

Genetic fingerprints that reveal where a brain cell came from remain distinct even after the cell becomes a brain tumor, an international coalition of scientists will report in the February 1 issue of Cancer Research.

The finding adds a new layer of complexity to the quest to understand the causes of childhood brain cancers, according to senior author David H. Gutmann, M.D., Ph.D., the Donald O. Schnuck Family Professor of Neurology at Washington University School of Medicine in St. Louis and co-director of the neuro-oncology program at the Siteman Cancer Center.

"Our findings suggest that brain tumors arising in different regions may be genetically distinct as a consequence of their unique cellular origins," Gutmann says. "This is yet another factor we need to consider when trying to understand how pediatric brain tumors form."

Researchers use information about tumor origins to develop new tests and treatments for the tumors. Brain tumors are the leading cause of cancer-related death in children, and the most common childhood brain tumor is the pilocytic astrocytoma (PA). Approximately 15 percent of all PAs are linked to neurofibromatosis 1 (NF1), a genetic condition that causes childhood brain tumors and is a primary focus of Gutmann's research. However, the genetic basis for the majority of PAs is unexplained.

In the new study, Gutmann led six laboratories in the most detailed genetic analysis of PAs to date.

"We were hoping to identify genes that contribute to the formation of these tumors and find indicators that might help us predict which tumors will be relatively well-behaved and which will be more aggressive," Gutmann says.

Previous studies have failed to produce any solid leads on the genetic alterations that predispose children to PAs.

"It should be recognized that the genetic alterations in this tumor may be very subtle," Gutmann notes. "When we looked at gene activity levels in the tumors as a function of brain location, though, a very interesting pattern began to emerge."

Cells in different parts of the brain carry the same genes, but they also contain factors that modify the use of those genes, suppressing some genes and activating others to allow the cells to take on specialized characteristics as the brain matures. These changes in gene activity levels are called changes in gene expression.

The researchers found that tumors arising in different regions of the brain retain distinct patterns of gene expression. These patterns provided genetic fingerprints or bar codes for the location of PAs, as well as for another glial cell tumor called an ependymoma. In addition, scientists also detected these distinct patterns of expression in normal glia and stem cells from these brain locations, suggesting that genetic fingerprints can be used to identify the potential origins of brain tumors.

"There's been a movement in recent years to link normal brain development to pediatric neuro-oncology, and these findings affirm that as a necessary approach," Gutmann says. "We won't fully understand the causes of pediatric brain tumors until we consider them in the context of factors that shape the development and specialization of different brain regions."

Sharma MK, Mansur DB, Reifenberger G, Perry A, Leonard JR, Aldape KD, Albin MG, Emnett RJ, Loeser S, Watson MA, Nagarajan R, Gutmann DH. Distinct genetic signatures among pilocytic astrocytomas relate to their brain region origin. Cancer Research, February 1, 2007.

Funding from Schnuck Markets, Inc.; Hyundai Motors; and the National Cancer Institute supported this research.

Washington University School of Medicine's full-time and volunteer faculty physicians also are the medical staff of Barnes-Jewish and St. Louis Children's hospitals. The School of Medicine is one of the leading medical research, teaching and patient care institutions in the nation, currently ranked fourth in the nation by U.S. News & World Report. Through its affiliations with Barnes-Jewish and St. Louis Children's hospitals, the School of Medicine is linked to BJC HealthCare.

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Novel Vaccine Curbs Brain Tumor Growth, Increases Survival

A novel vaccine has significantly increased life expectancy in patients with glioblastoma multiforme (GBM), the most dangerous type of brain tumor, a researcher from The University of Texas M. D. Anderson Cancer Center is reporting at the annual meeting of the American Association of Neurological Surgeons (AANS).

Median survival for the 23 patients tested at M. D. Anderson and at Duke University Medical Center is at least 19 months, and only four patients have died from the cancer, says Amy Heimberger, M.D., an assistant professor of Neurosurgery at M. D. Anderson. That figure surpasses the median survival of 14 months for patients with GBM who are treated with the most current chemotherapy and radiation, and the 4-month median survival for untreated patients, she says.

"We can't say this vaccine is better than chemotherapy because we haven't tested the two treatments head-to-head yet," she says. "However, so far, results have exceeded the expectations we had for this vaccine."

Heimberger's study was chosen by AANS for a Young Investigator's Award, and is being cited as one of the conference's most important findings.

The trial is now closed at both institutions. Given its statistically significant findings, a pharmaceutical company has acquired the rights to the drug and a larger, multi-institutional, randomized study is being planned, Heimberger says.

She describes the vaccine as an easy to use "off-the-shelf" treatment that can potentially help up to 50 percent of all GBM patients keep their cancer at bay for a period of time. Interim results of the Phase II clinical trial show that the vaccine significantly delays progression of tumors until the cancer finds a new growth pathway.

"This is a proof of concept, and optimal use of the vaccine may be with chemotherapy to further retard progression," says Heimberger. "Still, this is exciting to us because people have been trying to use immunotherapy against gliomas for a long time."

Heimberger and a team of researchers designed the vaccine to alert the brain's immune system to the presence of just one type of protein that studs the outside of a glioma tumor. This protein, epidermal growth factor variant III (EGFRvIII), is found on 30 percent to 50 percent of brain tumors, as well as on some breast and non-small-cell lung cancers, but not on normal tissue. Heimberger believes EGFRvIII drives gliomas to spread, which could explain why these brain tumors are unusually dangerous and invasive.

The vaccine contains a synthesized piece of EGFRvIII and compounds that stimulate immune system dendritic cells, which then activate the immune system in general and cytotoxic CD8 cells in particular. "It tricks the body into thinking that EGFRvIII is foreign, and the CD8 cells are sent in to kill the tumor," Heimberger says.

After initial therapy - three injections over a two-week period - patients in the clinical trial receive a monthly booster shot designed to keep the immune system activated against EGFRvIII-bearing cells. "Some patients have had booster shots for more than two years," she says. "We have found that the vaccine activates both the B- and T-cell arms of the immune system, and the vaccine is acting both as a therapy and as a preventive treatment."

When tumors began to grow again in the patients involved in the study, none of them displayed the protein. "We believe that this means the vaccine did its job," Heimberger says.

This easily manufactured and administered vaccine differs greatly from previous attempts to vaccinate patients against brain tumors, she adds, because those strategies required harvesting cells from each patient, growing them in the laboratory while manipulating them to express a certain protein, and then infusing them back into patients. "All we do for this vaccine is make sure the patient's tumor expresses EGFRvIII," Heimberger says. "The same vaccine is used for all patients who have such a tumor."

Heimberger expects that median survival rates will continue to increase over time.

UAB Launches Promising Brain Tumor Trial

UAB (University of Alabama at Birmingham) researchers are investigating whether a common but usually harmless virus can be used to treat a particularly devastating type of brain tumor called malignant glioma. The virus -- respiratory enteric orphan virus, or reovirus -- inhabits the lungs and intestines of humans. By adulthood, most humans have been exposed to it but demonstrate no illness or effects from the infection.

When the virus is introduced directly to malignant glioma cells however, it appears to be able to infect the malignant cell and then replicate, killing the cell.

"Healthy, non-cancerous cells in our bodies have the ability to prevent reovirus from replicating, so that even if we are infected with the virus we do not usually exhibit significant symptoms," said James M. Markert, M.D., professor and director of the UAB division of neurosurgery and principal investigator of the trial. "But brain tumor cells do not have that protection, due to a mutation in their DNA. The reovirus replicates, destroying the tumor cell, and the replicated virus goes in search of new tumor cells to infect."

About half of the 17,000 brain tumors diagnosed in the Unites States each year are malignant glioma, the most severe form of brain tumor. Survival rates are very poor, with as few as 10 percent of patients living for two years.

UAB is currently the only site participating in this Phase I/II trial sponsored by a Canadian biomedical company, Oncolytics Biotech Inc., using their proprietary formulation of human reovirus called REOLYSIN(R).

"The main purpose of the Phase I portion of the study is to determine whether the virus is safe." said Markert. "Previous studies give us reason to believe it will be well-tolerated without negative side effects."

Two catheters are placed in a tumor mass during a stereotactic brain surgery procedure. The reovirus is then infused through the catheters over the course of three days. MRI imaging will be used to determine whether the tumor mass shrinks over time, indicating that the virus is destroying tumor cells.

Markert said the trial will also examine whether the virus will be effective against glioma cells that have begun to spread away from the primary tumor. Glioma cells can break away from a tumor mass and migrate to other parts of the brain, traveling along nerve transmission lines called axons. Markert said there is evidence that reovirus, when infused slowly over several days, may have the same ability to travel via nerve axons, allowing the virus to pursue and destroy glioma cells away from the tumor mass itself.

UAB plans to enroll 15 people with recurrent malignant glioma in the Phase I portion of the trial.

About Oncolytics Biotech Inc.

Oncolytics is a Calgary-based biotechnology company focused on the development of oncolytic viruses as potential cancer therapeutics. Oncolytics' clinical program includes a variety of Phase I and Phase I/II human trials using REOLYSIN(R), its proprietary formulation of the human reovirus, alone and in combination with radiation.

New Targeted Brain Tumor Treatment Shows Promise In Pre-clinical Models

Gliomas are the most common primary brain tumors, and also one of the most complicated cancers to treat. Currently, treatment options such as surgery, radiation and chemotherapy are only marginally beneficial and present significant risks for patients, including loss of physical and cognitive abilities. But, a new study published today in Clinical Cancer Research found that treatment with a novel monoclonal antibody (mAb) L2G7 inhibited the growth of glioma cells, induced glioma regression within the brain and prolonged survival - a finding that could be translated into human trials as early as next year. "There is a tremendous need for advancement in the treatment of malignant brain tumors, which are the number one cancer killer of children under age 20 and a devastating diagnosis for adults as well," said Dr. John Laterra, M.D., Ph.D., research scientist at the Kennedy Krieger Institute and senior author of the study. "The results of this study bring us closer to developing an alternative treatment option for both adults and for pediatric patients, who are hardest hit by conventional therapies." A team of researchers, led by Dr. Jin Kim of Galaxy Biotech, LLC in Mountain View, CA and Dr. John Laterra of the Kennedy Krieger Institute in Baltimore, MD, designed the study to evaluate the effectiveness of L2G7 in treating human gliomas implanted in mouse models. Results indicate that treatment with L2G7 completely inhibited the growth of the tumors when established under the skin of animals, while control mAb had only a minimal effect. Even more promising results were observed in mice with tumors implanted within the brain. In this setting, L2G7 not only induced tumor regression, but dramatically increased survival. Animals treated with the control all died within 41 days of starting the experiment. All mice treated with L2G7 survived through day 70, and 80% of the animals were alive at day 90, six weeks after stopping the L2G7 treatment. L2G7 was developed by Dr. Kim's team to inhibit the activities of hepatocyte growth factor (HGF). HGF is known to be a promising target for cancer therapy by virtue of its multiple actions that promote cancer malignancy. HGF stimulates tumor cell division, tumor angiogenesis (blood vessel formation) and tumor cell resistance to toxic agents such as chemotherapy and radiation. In this study, brain tumor cells were injected both under the skin and within the brain to specifically evaluate anti-tumor responses within the central nervous system. The central nervous system is a location often protected from cancer therapies by the "blood-brain barrier," which could possibly limit the effects of mAb therapy on tumors situated within the brain. Treatment with L2G7 or a control mAb was given to both subsets of mice twice weekly. In one experiment, the researchers delayed treatment of a subset of mice for 18 days to determine the effect of L2G7 on larger, more advanced tumors within the brain. At that time, the average tumor size was 26.7 mm3, but following only three doses of L2G7, tumors shrank to 11.7 mm3. Conversely, tumors treated with the control mAb grew 5-fold to 134.3 mm3 during the same period, with a mean volume 12 times larger than the L2G7-treated tumors.
"Monoclonal antibodies to growth factors or their receptors are playing an increasingly important role in cancer therapy," said Dr. Cary Queen, President of Galaxy Biotech. "Because of its specificity for HGF, L2G7 may prove to be particularly effective at halting tumor growth while minimizing side effects and harm to the surrounding healthy brain cells."

"Our company is committed to the clinical development of L2G7, and we hope to extend the current success of targeted antibody therapies in the treatment of breast, colon and lung cancer patients to the treatment of serious central nervous system malignancies such as gliomas."

In a related study (Lal et al., Clin Cancer Res. 11:4479-4486, 2005), Dr. Laterra's research team showed that targeting brain tumor HGF with gene therapy can substantially enhance the anti-tumor effects of radiation therapy, again emphasizing the important role HGF plays in brain tumors.

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About Brain Tumors
Primary brain tumors originate in the brain. As the most common primary brain tumors, gliomas are the leading cancer killer of children under age 20, now surpassing acute lymphoblastic leukemia (ALL), and are the third leading cause of cancer death in young adults ages 20-39, according to the National Brain Tumor Foundation. Metastatic brain tumors (cancer that spreads from other parts of the body to the brain) occur at some point in 10-15% of persons with cancer. Each year, 190,000 people in the United States will be diagnosed with a primary or metastatic brain tumor. Because brain tumors are located at the control center for thought, emotion and movement, the effects of toxic modalities such as chemotherapy and radiation can be devastating, especially in young children. Surgery to remove malignant brain tumors is a complex and difficult procedure, and typically does not eliminate all of the cancer cells.

About the Kennedy Krieger Institute
Internationally recognized for improving the lives of children and adolescents with disorders and injuries of the brain and spinal cord, the Kennedy Krieger Institute in Baltimore, MD serves more than 12,000 children each year through inpatient and day treatment programs, outpatient clinics, home and community services and school-based programs. Kennedy Krieger provides a wide range of services for children with developmental concerns mild to severe, and is home to a team of investigators who are contributing to the understanding of how disorders develop and pioneering new interventions and earlier diagnosis. For more information on Kennedy Krieger Institute, visit http://www.kennedykrieger.org/.

About Galaxy Biotech, LLC
A start-up company with laboratories in Mountain View, CA, Galaxy Biotech is developing humanized antibodies against growth factors and their receptors for the treatment of cancer. The company was founded by Dr. Jin Kim, who while a senior scientist at Genentech, Inc. developed the mouse mAb from which the approved drug Avastin� was made, and by Dr. Cary Queen, who previously co-founded PDL BioPharma, Inc. and developed fundamental technology for the humanization of antibodies.

International Study: No Clear Connection Between Mobile Phone Use And Brain Cancer

According to a study conducted in five Northern European countries, there is no clear connection between mobile phone use and malignant brain tumours. The results of the study were published in the web version of the International Journal of Cancer on 19th January.

The study on the possible connection between mobile phone use and the risk of a malignant brain tumour, glioma, was carried out in Denmark, Finland, Norway, Sweden and England. The study showed that mobile phone users were not at an increased risk of developing a glioma.

Regular use of a mobile phone, duration of use, or the cumulative number of calls had no effect on the risk. The only indication of a potential effect was found among mobile phone users who had used a mobile phone for at least 10 years. They were found to have a slightly increased risk of a tumour on the side of the head on which they held the phone. Information on mobile phone use was collected using personal interviews. There is always a risk of error associated with recall, which affects the reliability of the results.

The research data from the participating countries was analysed by the Radiation and Nuclear Safety Authority (STUK). Funding for the study in Finland was provided by the Emil Aaltonen Foundation, Academy of Finland and Doctoral Programs for Public Health (DPPH).

The most extensive study so far

The study data collected between 2000 and 2004 included 1,521 glioma patients and 3,301 healthy controls. The number of people who had used a mobile phone for longer than 10 years was higher (222) than in previous studies.

"Even though the results do not indicate that mobile phone use increases the risk of cancer, we need more research data on long-term use," says Anssi Auvinen, Research Professor at the Radiation and Nuclear Safety Authority.

The completion of an extensive international study (INTERPHONE) on the connection between the use of mobile phone and brain tumour based on data collected in 14 countries is expected in the future.

About SUOMEN AKATEMIA (ACADEMY OF FINLAND)

Suomen Akatemia on tiederahoituksen asiantuntijaorganisaatio. Akatemian tehtaevaenae on edistaeae korkeatasoista tieteellistae tutkimusta - laatuun perustuvalla pitkaejaenteisellae tutkimusrahoituksella, - tieteen ja tiedepolitiikan asiantuntemuksella sekae - tieteen ja tutkimustyoen aseman vahvistamisella. Vuonna 2001 Akatemia rahoittaa paeaeasiassa yliopistoissa ja tutkimuslaitoksissa tehtaevaeae tutkimusta runsaalla miljardilla markalla (yli 180 miljoonalla eurolla). Se on noin 14 prosenttia Suomen valtion tutkimuspanostuksesta. Akatemian rahoittamissa hankkeissa tehdaeaen vuosittain noin 3000 tutkijatyoevuotta.

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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.

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