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graphic abstract for brain tumor paper

First large-scale proteogenomic analysis offers insights into pediatric brain tumor biology

graphic abstract for brain tumor paper

In the first large-scale, multicenter study of its kind, researchers conducted comprehensive analysis yielding a more complete understanding of pediatric brain tumors (PBT), which are the leading cause of cancer-related deaths in children. Researchers from the Clinical Proteomic Tumor Analysis Consortium (CPTAC) and Children’s Brian Tumor Network (CBTN) generated and analyzed proteomic data, which identifies common biological characteristics among different tumor types. The consortia consist of collaborators from the Icahn School of Medicine at Mount Sinai, National Cancer Institute, Fred Hutchinson Cancer Research Center, Children’s National Hospital and Children’s Hospital of Philadelphia. The study, published in Cell on November 25, 2020, provides a clearer understanding of the molecular basis of pediatric brain tumors and proposes new therapeutic avenues.

The molecular characterization of brain tumors has largely hinged upon the presence of unique alterations in the tumor genome ignoring the many layers of regulation that exist between DNA and the functional biology of the tumor cell that is actuated by proteins. The integration of proteomic data identifies common biological themes that span histologic boundaries, suggesting that treatments used for one histologic type may be applied effectively to other tumors sharing similar proteomic features.

Brian Rood, M.D., medical director of the Brain Tumor Institute and associate professor of pediatrics in the Center for Cancer and Blood Disorders at Children’s National Hospital, participated in this study and explains the importance of what the team discovered.

Q: Why was it important that researchers came together to do this work?

A: Comprehensive characterization of the fundamental biology of pediatric brain tumors, including the proteogenomic analysis done in this study, is essential to better understand and treat pediatric brain tumors.

Our study is based on the recognition that proteomics and phosphoproteomics needs to be integrated with other omics data to gain an improved systems biology view of the molecular features of brain tumors. In addition, characterizing biological themes that cross histologic boundaries and cells of origin can suggest extending treatments shown to be effective in one type of tumor to other histologically disparate tumors sharing the same proteomic features.

Proteomic data further reveal the functional impacts of somatic mutations and copy number variations (CNVs) not evident in transcriptomic data alone. Further, kinase-substrate network analyses identify activated biological mechanisms of tumor biology.

This work was only possible because of a unique collaboration between the CPTAC program of the NCI and the CBTN, of which Children’s National is a member.

Q: How will this work advance understanding and treatment of pediatric brain tumors?

A: Pediatric brain tumors have not benefitted from molecularly targeted drugs as much as other tumor types largely because they harbor relatively few gene mutations. Therefore, identifying key pathways to target in these patients’ tumors has been a challenge. The integration of proteomic and phosphoproteomic data with genomic data allows for the construction of a more comprehensive model of brain tumor biology and nominates specific key pathways to be targeted.

Q: What did you find that excites you?

A: Proteomic data revealed a number of findings that were not present in the genomic data. We found evidence to support a molecularly targeted approach to treating craniopharyngioma, a tumor that has previously been unresponsive to chemotherapy. We also found a prognostic marker for high grade gliomas that do not have a mutation in the H3 histone. We were able to identify specific kinases that may dictate the aggressive nature of certain ependymoma tumors. Importantly, we demonstrated the potential of proteomic studies to uncover unique tumor biology, paving the way for more extensive investigations using this approach.

You can find the full study published in Cell. Learn more about the Brain Tumor Institute at Children’s National.

Yuan Zhu

Study suggests glioblastoma tumors originate far from resulting tumors

Yuan Zhu

“The more we continue to learn about glioblastoma,” Yuan Zhu, Ph.D., says, “the more hope we can give to these patients who currently have few effective options.”

A pre-clinical model of glioblastoma, an aggressive type of cancer that can occur in the brain, suggests that this recalcitrant cancer originates from a pool of stem cells that can be a significant distance away from the resulting tumors. The findings of a new study, led by Children’s National Hospital researchers and published July 22 in the journal Nature Communications, suggest new ways to fight this deadly disease.

Despite decades of research, glioblastoma remains the most common and lethal primary brain tumor in adults, with a median survival of only 15 months from diagnosis, says study leader Yuan Zhu, Ph.D., the scientific director and endowed professor of the Gilbert Family Neurofibromatosis Institute at Children’s National. Unlike many cancers, which start out as low-grade tumors that are more treatable when they’re caught at an early stage, most glioblastomas are almost universally discovered as high-grade and aggressive lesions that are difficult to treat with the currently available modalities, including surgery, radiation and chemotherapy.

“Once the patient has neurological symptoms like headache, nausea, and vomiting, the tumor is already at an end state, and disease progression is very rapid,” Dr. Zhu says. “We know that the earlier you catch and treat cancers, the better the prognosis will be. But here, there’s no way to catch the disease early.”

However, some recent research in glioblastoma patients shows that the subventricular zone (SVZ) – an area that serves as the largest source of stem cells in the adult brain – contains cells with cancer-driving mutations that are shared with tumors found in other often far-distant brain regions.

To see if the SVZ might be the source for glioblastoma tumors, Dr. Zhu and his colleagues worked with pre-clinical models that carried a single genetic glitch: a mutation in a gene known as p53 that typically suppresses tumors. Mutations in p53 are known to be involved in glioblastoma and many other forms of cancer.

Using genetic tests and an approach akin to those used to study evolution, the researchers traced the cells that spurred both kinds of tumors back to the SVZ. Although both single and multiple tumors had spontaneously acquired mutations in a gene called Pten, another type of tumor suppressor, precursor cells for the single tumors appeared to acquire this mutation before they left the SVZ, while precursor cells for the multiple tumors developed this mutation after they left the stem cell niche. When the researchers genetically altered the animals to shut down the molecular pathway that loss of Pten activates, it didn’t stop cancer cells from forming. However, rather than migrate to distal areas of the brain, these malignant cells remained in the SVZ.

Dr. Zhu notes that these findings could help explain why glioblastoma is so difficult to identify the early precursor lesions and treat. This work may offer potential new options for attacking this cancer. If new glioblastoma tumors are seeded by cells from a repository in the SVZ, he explains, attacking those tumors won’t be enough to eradicate the cancer. Instead, new treatments might focus on this stem cell niche as target for treatment or even a zone for surveillance to prevent glioblastoma from developing in the first place.

Another option might be to silence the Pten-suppressed pathway through drugs, a strategy that’s currently being explored in various clinical trials. Although these agents haven’t shown yet that they can stop or reverse glioblastomas, they might be used to contain cancers in the SVZ as this strategy did in the pre-clinical model — a single location that might be easier to attack than tumors in multiple locations.

“The more we continue to learn about glioblastoma,” Dr. Zhu says, “the more hope we can give to these patients who currently have few effective options.”

Other Children’s National researchers who contributed to this study include Yinghua Li, Ph.D., Wei Li, Ph.D., Yuan Wang, Ph.D., Seckin Akgul, Ph.D., Daniel M. Treisman, Ph.D., Brianna R. Pierce, B.S., Cheng-Ying Ho, M.D. /Ph.D.

This work is supported by grants from the National Institutes of Health (2P01 CA085878-10A1, 1R01 NS053900 and R35CA197701).

pastel colored DNA strands

Germline microsatellite genotypes differentiate children with medulloblastoma

pastel colored DNA strands

A new study suggests that medulloblastoma-specific germline microsatellite variations mark those at-risk for medulloblastoma development.

Brian Rood, M.D., oncologist and medical director at the Brain Tumor Institute, and Harold “Skip” Garner, Ph.D., associate vice provost for research development at Edward Via College of Osteopathic Medicine, published a report in the Society for Neuro-Oncology’s Neuro-Oncology Journal about using a novel approach to identify specific markers in germline (non-tumor) DNA called microsatellites that can differentiate children who have the brain tumor medulloblastoma (MB) from those who don’t.

“Ultimately, the best way to save children from brain tumors and prevent them from bearing long-term side effects from treatment is to prevent those tumors from occurring in the first place,” says Dr. Rood. “New advancements hold the potential to finally realize the dream of cancer prevention, but we must first identify those children at-risk.”

While analyzing germline sequencing data from a training set of 120 MB subjects and 425 controls, the doctors identified 139 individual microsatellites whose genotypes differ significantly between the groups. Using a genetic algorithm, they were able to construct a subset of 43 microsatellites that distinguish MB subjects from controls with a sensitivity and specificity of 92% and 88% respectively.

“We made discoveries in an untapped part of the human genome, enabled by unique bioinformatics data mining approaches combined with clinical insight,” said Dr. Garner. “Our findings establish new genomic directions that can lead to high accuracy diagnostics for predicting susceptibility to medulloblastoma.”

What the doctors discovered and demonstrated in the study was that MB-specific germline microsatellite variations mark those at risk for MB development and suggest that other mechanisms of cancer predisposition beyond heritable mutations exist for MB.

“This work is the first to demonstrate the ability of specific DNA sequences to differentiate children with cancer from their healthy counterparts,” added Dr. Rood.

Contributing Authors to this research study included:  Brian R. Rood, M.D., Harold R. Garner, Ph.D., Samuel Rivero-Hinojosa, Ph.D., and Nicholas Kinney, Ph.D.

2019 at a glance: Oncology at Children’s National

Oncology at Children's National
Roger Packer

Roger J. Packer, M.D. presents keynote address for BRAIN 2019

Roger Packer

2019 Otto Lien Da Wong visiting professor in neuro-oncology at BRAIN 2019, Roger J. Packer, M.D. presented the keynote address.

 

More than 400 neurologists, neurosurgeons, pathologists, pediatricians, clinical and basic scientists gathered in Hong Kong for Brain 2019, a conjoint congress of the 3rd Asian Central Nervous System Germ Cell Tumour Conference (CNSGCT), the 9th Interim Meeting of the International Chinese Federation of Neurosurgical Sciences (ICFNS) and the 16th Asia Pacific Multidisciplinary Meeting for Nervous System Diseases (BRAIN) which is also jointly organized by The Chinese University of Hong Kong. This three-day convention discussed advances in pediatric neuro-oncology and neuro-rehabilitation.

Invited as the 2019 Otto Lien Da Wong (OLDW) visiting professor in neuro-oncology, Roger J. Packer, M.D., senior vice president for the Center of Neuroscience and Behavioral Medicine and director at the Gilbert Neurofibromatosis and Brain Tumor Institutes, presented a keynote address titled “Advances in Pediatric Brain Tumors.” Established in 2009, the purpose of the visiting professorship is to advance surgical knowledge and techniques in neuro-oncology between Hong Kong and major medical centers around the world. Dr. Packer was selected from an international field of acclaimed academic surgeons and scholars in the field of neuro-oncology. Two additional presentations included “Pediatric Brain Tumors in Molecular Era: Germ Cell Tumors” as an invited guest of the BRAIN conference and a presentation on “Treatment of Medulloblastoma and PNET” as a session presented by the ICFNS.

In addition to his presentations, Dr. Packer will participate in surgical teaching and scholastic exchange with local surgeons, surgical trainees and medical students.

Javad Nazarian

Meeting of the minds: Children’s National hosts first DIPG Round Table Discussion

Javad Nazarian at DIPG Round Table Discussion

Spearheaded by Javad Nazarian, Ph.D., MSC, Scientific Director of the Children’s National Brain Tumor Institute, the focused DIPG Round Table Discussion brought investigators, neurosurgeons and clinicians from North America, Europe and Australia to Children’s National in Washington, D.C.

Over 40 experts involved in the study and treatment of diffuse intrinsic pontine gliomas (DIPG) convened at the inaugural DIPG Round Table Discussion at Children’s National Health System Sept. 30-Oct. 2.

Spearheaded by Javad Nazarian, Ph.D., MSC, Scientific Director of the Children’s National Brain Tumor Institute, the focused DIPG Round Table Discussion brought investigators, neurosurgeons and clinicians from North America, Europe and Australia to Children’s National in Washington, D.C., to engage in dialogue and learn about the changing landscape of DIPG tumor biology and therapeutics. Attendees discussed the recent discoveries in DIPG research, precision medicine, preclinical modeling, immunotherapy, data sharing and the design of next generation clinical trials.

Families affected by DIPG also had an opportunity to participate in day 2 of the event. Many voiced the necessity of data sharing to ensure progress in the field. Dr. Nazarian seconded that point of view: “It is critical to get raw data and have it harmonized and integrated so that the end users (researchers) can utilize and do cross-data analysis…We need to break down the silos.” The highlight of the data sharing session was the Open DIPG Initiative that is spearheaded by Dr. Nazarian and the Children’s Brian Tumor Tissue Consortium (CBTTC).

Nazarian Lab at DIPG Roundtable Meeting

Eshini Panditharatna, Ph.D., Madhuri Kambhampati, Sridevi Yadavilli, M.D., Ph.D., and Erin Bonner of Children’s National at the DIPG Round Table.

As recent technological and molecular advances in DIPG biology have pushed the field forward, focus groups have become essential to share data, ideas and resources with the overarching goal of expediting effective treatments for children diagnosed with DIPG. An extremely aggressive form of pediatric brain cancer, DIPG accounts for roughly 10 to 15 percent of all brain tumors in children. Between 300 and 400 children in the United States are diagnosed with DIPG each year, but the 5-year survival for the brain tumor is less than 5 percent, a strikingly low number in comparison with other types of childhood cancer. DIPG research and clinical initiatives have changed in the past years mainly due to the generous support of families for basic research. The DIPG Open Table meeting was designed to coalesce a team of experts to expedite the first crack at curing this devastating childhood cancer.

Roger Packer high fives patient Olivia Enos

Kids’ resilience pushes neurologist to seek better therapies

Roger Packer high fives patient Olivia Enos

“I get strength from kids and families, strength like that shown by Nick and his family,” answered Roger Packer, M.D., when Quicken Loans owner Dan Gilbert asked how he copes with the stress of seeing children struggling with brain tumors and other neurological problems every day.

Dr. Packer, senior vice president of the Center for Neuroscience and Behavioral Health at Children’s National Health System, joined Mr. Gilbert and his son, Nick, who was treated for neurofibromatosis at Children’s National, for a panel discussion at the recent Crain’s Health Care Heroes event. The discussion focused on Nick Gilbert, now a college student, and how he has stayed positive while undergoing intense treatments for neurofibromatosis since he was 15 months old.

Dr. Packer met Nick at age 10, when he first came to Children’s National for its world-renowned expertise in neurofibromatosis research and care. After their experiences, the Gilberts generously supported the creation of the Gilbert Family Neurofibromatosis Institute at Children’s National Health System to continue research into new and innovative treatments for the disorder.

Mr. Gilbert credits Dr. Packer with taking on difficult cases and having a positive impact on both Nick and himself. “When other doctors give up on patients, he intervenes with magic and saves lives.”

The reason, according to Dr. Packer, is that kids like Nick “don’t want to give up.” Thankfully, he notes, better tools to treat diseases like cancer and neurofibromatosis have finally arrived. “There are remarkable advances that were not possible five years ago,” he said.

The full session at the Health Care Heroes event was featured in Crain’s Detroit Business.

Roger Packer, M.D., elected Pediatric Co-Chair by the National Cancer Institute’s Brain Malignancies Steering Committee

Roger Packer, MD

Roger J. Packer, M.D., Senior Vice President, Center for Neuroscience & Behavioral Health at Children’s National Health System, has been elected by the National Cancer Institute’s Brain Malignancies Steering Committee (BMSC) as the committee’s new Pediatric Co-Chair.

One of 16 steering committees formed in response to the recommendations of the Clinical Trials Working Group mandated by the National Cancer Advisory Board (NCAB), the BMSC’s goal is to promote the best clinical and translational research for patients with brain cancer by critically reviewing Phase 2 and Phase 3 clinical trial concepts.

Dr. Packer also directs the Brain Tumor Institute and is principal investigator for the Pediatric Brain Tumor Consortium (PBTC), formed under the auspices of the National Cancer Institute (NCI). He has worked closely with the NCI and the National Institute of Neurological Disorders and Stroke (NINDS), and has served on multiple committees setting the directions for neurologic clinical and basic science research for the future. Much of Dr. Packer’s clinical research has been translational in nature. He has been part of studies evaluating the molecular genetics of childhood and adult neurologic diseases, and has also coordinated the first gene therapy study for children with malignant brain tumors in the U.S.

Dr. Roger Packer

New brain tumor research collaborative taps Children’s for scientific director

Dr. Roger Packer

This year, more than 4,600 children and adolescents (0-19 years) will be diagnosed with a pediatric brain tumor. Brain tumors have now passed leukemia as the leading cause of pediatric cancer-related deaths. Despite this, there has never been a drug developed specifically to treat pediatric brain tumors and for many pediatric brain tumor-types, no standards of care or effective treatment options exist. In particular, pediatric high-grade gliomas have no standard of care and a very low survival rate.

To combat this, the National Brain Tumor Society (NBTS), the largest nonprofit dedicated to the brain tumor community in the United States, with its partner, the St. Baldrick’s Foundation, the largest private funder of childhood cancer research grants, as well as several world-renowned experts in the field of pediatric neuro-oncology, announced a new awareness and fundraising campaign to support a major translational research and drug discovery program. The campaign, called “Project Impact: A Campaign to Defeat Pediatric Brain Tumors,” was unveiled at the National Press Club in Washington, DC, on Sept. 12. Watch the live streaming replay.

Children’s National brain tumor expert leads the way
The collaborative hopes to improve clinical outcomes for pediatric brain tumor patients and inform the development of the first standard of care for treating pediatric high-grade gliomas, including DIPG – the deadliest of pediatric cancers.

Roger J. Packer, M.D., Senior Vice President of the Center for Neuroscience and Behavioral Medicine and Director of Brain Tumor Institute at Children’s National Health System, serves as the Scientific Director of the Defeat Pediatric Brain Tumors Research Collaborative.

“Treatment of pediatric high-grade gliomas has been extremely frustrating with little progress made over the past quarter century,” said Dr. Packer. “New molecular insights provide hope that therapies will be dramatically more effective in the very near future. In the last two years alone we have had great breakthroughs, primarily identifying genes which are critical in development of new pediatric treatments. But we need to maintain forward momentum from discovering the molecular and genetic underpinnings of these tumors, to understanding how these changes drive these tumors, and to ultimately developing effective, biologically precise therapies. This is a major opportunity for the field, patients, and their families.”

Pediatric high-grade gliomas make up to 20 percent of all pediatric brain tumors with roughly 500-1,000 new diagnoses every year. These tumors are WHO Grade III and Grade IV gliomas, including: pediatric glioblastoma (GMB); glioma malignant, NOS; pediatric anaplastic astrocytoma; anaplastic oilgodendroglioma; giant cell glioblastoma; gliosarcoma; and diffuse intrinsic pontine gliomas (DIPG).

David Arons, CEO of the National Brain Tumor Society said, “Researching and developing new treatments for pediatric brain tumors is a particularly challenging task, which faces multiple – but interrelated – barriers that span the research and development spectrum from small patient populations, lack of effective preclinical models, to complex basic biology, regulatory hurdles and economic disincentives. To overcome these complex challenges, and get better treatments to patients, we needed to create an equally sophisticated intervention. We believe that having groups with complementary skills work together in a coordinated effort, sharing data and expertise, and tackling the problem from multiple angles as one team is the starting point for greater and faster progress.”

How the collaborative is set up
The model for the collaborative consists of scientists and researchers who will each lead interrelated “Cores” to work on critical areas of research simultaneously and in concert with one another, encouraging sharing of findings real time. This design allows new findings to quickly move onto the next stage of research without barriers or other typical delays, significantly speeding up the research process.

Dr. Packer said the goal of this research collaboration is to work with pediatric brain tumor researchers from around the world to discover new treatments for children in the next two to three years, instead of the next decade.

Javad Nazarian

Surviving pediatric diffuse intrinsic pontine glioma

Mutations in histone-encoding genes are associated with the vast majority of pediatric DIPG cases.

For more than four decades, clinicians around the nation have been giving the parents of pediatric patients diagnosed with diffuse intrinsic pontine glioma (DIPG) the same grim prognosis. In the past five years, there has been an explosion of innovative research at Children’s National Health System and elsewhere that promises to change that narrative. That’s because the black box that is DIPG is beginning to divulge its genetic secrets. The new-found research knowledge comes as a direct result of parents donating specimens, judicious shepherding of these scarce resources by researchers, development of pre-clinical models, and financing from small foundations.

From just 12 samples six years ago, Children’s National has amassed one of the nation’s largest tumor bio banks – 3,000 specimens donated by more than 900 patients with all types of pediatric brain tumors, including DIPG.

Such donated specimens have led to the identification of H3K27M mutations, a groundbreaking finding that has been described as the single-most important discovery in DIPG. Mutations in histone-encoding genes are associated with the vast majority of pediatric DIPG cases.

Histone mutations (also referred to as oncohistones) are sustained in the tumor throughout its molecular evolution, found a research team led by Javad Nazarian, Ph.D. Not only were H3K27M mutations nearly ubiquitous in all samples studied, the driver mutation maintained partnerships with other secondary mutations as DIPG tumor cells spread throughout the developing brain. Children’s National researchers have identified tumor driver mutations and obligate partner mutations in DIPG. They are examining what happens downstream from the histone mutation – changes in the genome that indicate locations they can target in their path toward personalized medicine. The value of that genomic knowledge is akin to emergency responders being told the specific house where their help is needed, rather than a ZIP code or city name, Dr. Nazarian says. While there is currently no effective treatment for DIPG, new research has identified a growing number of genomic targets for future therapeutics.“That changed the dynamic,” says Dr. Nazarian. “In DIPG clinical research, nothing had changed for 45 years. Now we know some of the genomic mutations, how the tumor was evolving – gaining new mutations, losing mutations. With precision medicine, we can target those mutations.”

Another study led by neuro-oncologist Eugene Hwang, M.D., reported the most comprehensive phenotypic analyses comparing multiple sites in a young girl’s primary and metastatic tumors. This study showed that despite being uniform, small molecules (mRNA) could be used to distinguish an evolved tumor from its primary original tumor mass.Key to this multidisciplinary work is collaboration across divisions and departments. Within the research lab, knowledge about DIPG is expanding.

Each member of the DIPG team – neurosurgery, neuro-oncology, immunology, genomics, proteomics – feeds insight back to the rest of the team, accelerating the pace of research discoveries being translated into clinical care. Among the challenges that the team will address in the coming months is outmaneuvering tumors that outsmart T-cells (immune cells).

“What is happening in the checkpoint inhibitor field is exciting,” says Catherine M. Bollard, MBChB, MD, Chief of Allergy and Immunology and Director of the Program for Cell Enhancement of Technologies for Immunotherapy. “The inhibitors work by reversing the ‘off’ switch – releasing the brake that has been placed on the T-cells so they can again attack multiple tumor proteins. The next exciting step, and novel to Children’s National, will be to combine this approach with T-cell therapies specifically designed to attack the DIPG tumors. Unlike the use of combination chemotherapy, which has had a limited impact, we hope that the novel combination of immunotherapeutic approaches will offer the hope of a potential cure.”

Dr. Hwang, another member of the multidisciplinary team, adds: “When you’re looking at the landscape – for me, at least – it starts and ends with how my patients are doing. There are kids for whom we have had great successes in improving survival rates in some cancers, like leukemia, and some where the needle has moved nowhere, like DIPG. We’re still trying to figure out the whole picture of who responds. The immune system is present in all kids. Its ability to attack is present in all kids.”

Children’s National is one of the few hospitals in the nation that conducts brainstem biopsies for DIPG and does so with very little chance of complications. The pons is like a superhighway through which nerves pass, making it instrumental in smooth operation of such vital functions as breathing, heart rate, sleeping, and consciousness. The ability of neurosurgeon Suresh Magge, MD, to perform such sensitive biopsies upends conventional wisdom that these procedures were inherently too dangerous. Within two weeks of diagnosis, genomics analyses are run to better understand the biology of that specific tumor. Within the following weeks, the tumor board occurs, and patients with DIPG are placed on therapy that best targets their tumor’s mutations.

The black box that is diffuse intrinsic pontine glioma is beginning to divulge its genetic secrets.

Despite an increasing number of experimental therapies tested via clinical trials, more than 95 percent of children with DIPG die within two years of diagnoses. Biomarkers that point to DIPG – like the copies of DNA that tumors shed and leave behind in the bloodstream – could enable creation of liquid biopsies, compared with today’s surgical approach.

Children’s also is making a concerted effort to create preclinical models of DIPG. Preclinical models will be used to winnow the field of potential therapeutics to the candidates most likely to help children survive DIPG. The preclinical tumor cells will be labeled with luciferase – enzymes that, like photoproteins, produce bioluminescence – permitting the researcher to visually see the formation, progression, and response of DIPG tumors to treatment in preclinical settings.

These preclinical models could be used to test multiple drug combinations in conjunction with radiation therapy. Molecular signatures and response to treatment could then be assessed to learn how the tumor resists therapy. Due to the obligate partnerships between driver mutations and secondary mutations, the research team already knows that effective DIPG medicines will need more than one target. If there were a single mutation, that would be like having a single master key to open many locks. Multiple mutations imply that more than one key will be needed. Thus, the search for cures for DIPG will necessitate taking a multi-pronged approach.

Combined drug regimens, including those created with proprietary technology, with or without radiation, will be keys to targeting myriad mutations in order to kill tumors where they are. Those drug combinations that demonstrate they can do their jobs – slowing tumor growth, increasing chances of survival, taming toxicity – will be selected for clinical application.

Immunotherapy leverages T-cells, the immune system’s most able fighters, to help in the overall goal of extending patients’ survival. One of the most challenging aspects of pediatric brain tumors is the body does a very good job of shielding the brain from potential pathogens. Precise drug delivery means finding innovative ways for therapeutics to cross the blood-brain barrier in order to reach the tumor. The team has identified one such potential target, the protein NG2, which may represent a good target for immune therapy. The protein is expressed in primitive cells that have not become specialized – meaning there may be an opportunity to intervene before it is driven to become a tumor cell.

Related resources
Research at a Glance: Clinicopathology of diffuse intrinsic pontine glioma and its redefined genomic and epigenomic landscape
Research at a Glance: The role of NG2 proteoglycan in glioma
Research at a Glance: Spatial and temporal homogeneity of driver mutations in diffuse intrinsic pontine glioma
Research at a Glance: Histological and molecular analysis of a progressive diffuse intrinsic pontine glioma: a case report

researcher using ice bucket in lab

Spatial and temporal homogeneity of driver mutations in diffuse intrinsic pontine glioma

What’s Known
Needle biopsies help to guide diagnosis and targeted therapies for diffuse intrinsic pontine gliomas (DIPGs), which make up 10 percent to 15 percent of all pediatric brain tumors but carry a median survival of 9 to 12 months. This dismal survival rate compares with a 70 percent chance of children surviving other central nervous system tumors five years post diagnosis. In DIPG, tumors appear in the pons, an area of the brain that houses cranial nerve nuclei. Surgical options are limited. Spatial and temporal tumor heterogeneity is a major obstacle to accurate diagnosis and successful targeted therapy.

What’s New
The team sought to better define DIPG heterogeneity. They analyzed 134 specimens from nine patients and found that H3K27M mutations were ubiquitous in all 41 samples with oncogenic content, and always were associated with at least one partner driver mutation: TP53, PPM1D, ACVR1 or PIK3R1. These H3K27M mutations are the initial oncogenic event in DIPG, writes the research team led by Children’s National Health System. “Driver” mutations, such as H3K27M, are essential to begin and sustain tumor formation. This main driver partnership is maintained throughout the course of the disease, in all cells across the tumor, and as tumors spread throughout the brain. Because homogeneity for main driver mutations persists for the duration of illness, efforts to cure DIPG should be directed at the oncohistone partnership, the authors write. Based on early tumor spread, efforts to cure DIPG should aim for early systemic tumor control, rather focused exclusively on the pons.

Questions for Future Research
Q: If a larger sample size were analyzed, what would it reveal about the true heterogeneity/homogeneity status of DIPGs?
Q: “Accessory” driver mutations are not absolutely essential but do help to further promote and accelerate tumor growth. What is their precise role?

Source: Spatial and Temporal Homogeneity of Driver Mutations in Diffuse Intrinsic Pontine Glioma.” H. Nikbakht, E. Panditharatna, L.G. Mikael, R. Li, T. Gayden, M. Osmond, C.Y. Ho, M. Kambhampati, E.I. Hwang, D. Faury, A. Siu, S. Papillon-Cavanagh, D. Bechet, K.L. Ligon, B. Ellezam, W.J. Ingram, C. Stinson, A.S. Moore, K.E. Warren, J. Karamchandani, R.J. Packer, N. Jabado, J. Majewski, and J. Nazarian. Published by Nature Communications on April 6, 2016.