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A transient low-dose MEKi treatment in a pre-clinical model prevents NF1-OPG formation

Using targeted signaling pathway therapy to prevent pediatric glioma formation

Researchers at Children’s National Hospital identified a vulnerability in a developmental signaling pathway that can be hijacked to drive pediatric low-grade glioma (pLGG) formation, according to a pre-clinical study published in Developmental Cell. The study demonstrated that targeted treatment prevents tumor formation, long before irreversible damage to the optic nerve can cause permanent loss of vision. This finding will inform chemo-prevention therapeutic trials in the future.

Brain tumors are the most common solid tumors in children, the most prevalent of which are pLGGs. Approximately 10% to 15% of pLGGs arise in patients with the familial cancer predisposition syndrome known as neurofibromatosis type 1 (NF1). This is a genetic condition that increases risks of developing tumors along the nerves and in the brain.

Nearly 20% of children with NF1 develop pLGGs along the optic pathway, also known as NF1-associated optic pathway glioma (NF1-OPG). Despite many advances in cancer therapy, there are no definitive therapies available that prevent or alleviate the neurological deficits (i.e. vision loss) and that could improve the quality of life.

“The evidence presented can inform chemoprevention therapeutic trials for children with NF1-OPG,” said Yuan Zhu, Ph.D., scientific director and Gilbert Family Endowed professor at the Gilbert Family Neurofibromatosis Institute and associate director of the Center for Cancer and Immunology Research, both part of Children’s National. “This therapeutic strategy may also be applicable to children with the developmental disorders that are at high risk of developing pediatric tumors, such as other RASopathies.”

The mechanism of vulnerability to pLGGs during development is not fully understood. It has been implied that the cell population of origin for this debilitating tumor is transiently proliferative during development. The NF1 gene produces a protein that helps regulate normal cell proliferation, survival and differentiation by inhibiting MEK/ERK signaling. When there is loss of function in NF1, it abnormally activates the MEK/ERK signaling pathway and leads to tumor formation.

Certain cells that exist transiently during the normal development of the brain and optic nerve are vulnerable to tumor formation because they depend on the MEK/ERK signaling. In this study, researchers in Zhu’s lab identified cells that were MEK/ERK pathway dependent and grew during a transient developmental window as the lineage-of-origin for NF1-OPG in the optic nerve. The researchers used a genetically engineered pre-clinical model to design a transient, low-dose chemo-preventative strategy, which prevented these tumors entirely.

“When we provided a dose-dependent inhibition of MEK/ERK signaling, it rescued the emergence and increase of brain lipid binding protein-expressing (BLBP+) migrating GPs glial progenitors, preventing NF1-OPG formation,” wrote Jecrois et al. “Equally importantly, the degree of ERK inhibition required for preventing NF1-OPG formation also greatly improved the health and survival of the NF1-deficient model.”

Ongoing clinical trials using MEK inhibitors (MEKi) are being performed for children as young as 1 month old. Thus, it becomes increasingly feasible to design a chemo-preventative trial using a MEKi to treat children with NF1. These treatment paradigms may have the potential to not only prevent OPG formation, but also other NF1-associated and RASopathies-associated developmental defects and tumors.

A transient low-dose MEKi treatment in a pre-clinical model prevents NF1-OPG formation

A transient low-dose MEKi treatment in a pre-clinical model prevents NF1-OPG formation. The middle panels highlighted by a red dashed box show an OPG in the optic nerve (arrows, top), exhibiting abnormal triply-labeled tumor cells, inflammation and nerve damage (the bottom three panels), which are absent in the normal (left panels) or MEKi-treated Nf1-deficient optic nerves (right panels). [Credit: Jecrois et al., Developmental Cell, (2021)]

Yuan Zhu

Yuan Zhu, Ph.D., receives Outstanding Scientist Award

Yuan Zhu

The George Washington University (GW) Cancer Center recently announced the selection of the 2021 GW Cancer Center Awards, recognizing excellence in research, mentorship and early career contributions.

The GW Cancer Center Outstanding Scientist Award was presented to Yuan Zhu, Ph.D., professor of pediatrics at the GW School of Medicine and Health Sciences (SMHS) and Children’s National Hospital. The award is presented to faculty members who make a noteworthy contribution in the areas of basic science, clinical science, translational science or population science.

In his nomination, Dr. Zhu was cited for his contributions to the understanding of the mechanisms underlying the development of tumors and altered brain development arising in the setting of the inherited condition neurofibromatosis type 1 (NF1). “Throughout his career, Dr. Zhu has had a remarkable consistency of focus in his scholarly work, where he has sought to advance new molecular and mechanistic insights to understand the biological basis of NF1 and the cancers arising in individuals affected by this genetic disease.”

You can find a full list of award winners here.

Research & Innovation Campus

Virginia Tech, Children’s National Hospital award $100,000 to fund collaborative cancer research pilot projects

Research & Innovation Campus

This pilot research program represents a growing academic research partnership between Children’s National and Virginia Tech. Last year, the two institutions announced that Virginia Tech will establish a biomedical research facility on the Children’s National Research & Innovation Campus.

Children’s National Hospital and Virginia Tech have awarded two $50,000 one-year pilot grants to multi-institutional teams of scientists for pediatric brain cancer research.

The inter-institutional program, which launched in December, promotes cross-disciplinary collaborations among researchers at both institutions. At Virginia Tech, the program is part of the Virginia Tech Cancer Research Alliance. Financial support for the program was provided by the Offices of the Physician-in-Chief and Chief Academic Officer at Children’s National, and by Virginia Tech’s Office of the Vice President for Health Sciences and Technology.

“We were delighted to see so many innovative and competitive research proposals for our first round of pilot grants in the area of brain cancer. By forging new research collaborations with our partners at Children’s National, we hope to make major strides in addressing one of the most common and devastating groups of cancers in children,” said Michael Friedlander, Virginia Tech’s vice president for health sciences and technology, and the executive director of the Fralin Biomedical Research Institute at VTC. “The pilot funding will bootstrap several programs to be able to acquire ongoing sustainable funding by providing the opportunity to test novel high impact ideas for new strategies for treating these disorders. There are simply too few good options for children in this space now and this partnership can change that for the better.”

The collaborative research initiative began through an agreement between the Fralin Biomedical Research Institute and the Children’s National Research Institute. The collaborative teams formed through a series of interactive discussions among Virginia Tech’s Cancer Research Alliance faculty members from the university’s Blacksburg and Roanoke campuses, and Children’s National’s neuro-oncology researchers.

“I am extremely excited by this collaboration between VT and CNH that is focused on pediatric brain tumors which is such an area of unmet need,” said Catherine Bollard, M.D., M.B.Ch.B.,, director of Children’s National’s Center for Cancer and Immunology Research. “I am confident that the funded proposals will soon advance our understanding of pediatric brain tumors and, more importantly, facilitate more joint efforts between two world-class institutions which is especially timely with the development of the Children’s National Research & Innovation Campus.”

Yanxin Pei, Ph.D., an assistant professor in the Center for Cancer Immunology Research at Children’s National, and Liwu Li, Ph.D., a professor of biological sciences in Virginia Tech’s College of Science, were awarded one of the pilot research grants to study how white blood cells called neutrophils are involved in metastatic MYC-driven medulloblastoma, an aggressive type of brain tumor in children that often resists conventional radiation and chemotherapies.

Yuan Zhu, Ph.D., the Gilbert Family Professor of Neurofibromatosis Research at Children’s National, and Susan Campbell, Ph.D., an assistant professor of animal and poultry sciences in Virginia Tech’s College of Agriculture and Life Sciences, were awarded funds to study glioma-induced seizures in mice with a genetic mutation that inhibits the production of P53, a key protein involved in suppressing cancer cell growth and division.

The successful applicants will receive funding starting this month and are expected to deliver preliminary data to support an extramural research application by 2024.

This pilot research program represents a growing academic research partnership between Children’s National and Virginia Tech. Last year, the two institutions announced that Virginia Tech will establish a biomedical research facility on the Children’s National Research & Innovation Campus. It will be the first research and innovation campus in the nation focused on pediatrics when it opens later this year and will house newly recruited teams of pediatric brain cancer researchers.

Liwu Li, Yanxin Pei, Susan Campbell, and Yuan Zhu

Liwu Li, Ph.D., Yanxin Pei, Ph.D., Susan Campbell, Ph.D., and Yuan Zhu, Ph.D., were awarded funding through the new pilot research program.

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).

Yuan Zhu

The brain tumor field moves forward with new findings and a research grant

Yuan Zhu

Yuan Zhu, Ph.D., and other experts completed new research findings evaluating the effects of manipulating the growth-promoting signaling pathways in brain tumors associated with adults and children.

This month, experts at Children’s National Health System made great strides in brain tumor research, specifically in gliomas, glioblastomas and medulloblastomas. Led by Yuan Zhu, Ph.D., the scientific director and Gilbert Endowed Professor of the Gilbert Family Neurofibromatosis Institute and Center for Cancer and Immunology Research at Children’s National, the team completed new research findings evaluating the effects of manipulating the growth-promoting signaling pathways in brain tumors associated with adults and children. Dr. Zhu’s research was recently published in Cell Reports and he was also awarded a U.S. Department of Defense (DoD) grant to gain a better understanding of how low-grade gliomas form. Together, this work moves the needle on developing more effective treatments for these debilitating and life-threatening tumors.

The study

In his recently published paper, Dr. Zhu and his colleagues, including Drs. Seckin Akgul and Yinghua Li, studied glioblastomas, the most common brain tumor in adults, and medulloblastomas, the most common brain tumor found in children, in genetically engineered experimental models. Dr. Zhu found that when they removed the p53 gene (the most commonly mutated tumor suppressor gene in human cancers) in the experimental model’s brain, most developed malignant gliomas and glioblastomas, while Sonic Hedgehog (SHH)-subtype (SHH) medulloblastomas were also observed. They further suppressed the Rictor/mTorc2 molecular pathway that is known in the regulation of tumor growth. This action greatly reduced the incidence of malignant gliomas and extended the survival of the models, validating the concept that Rictor/mTorc2 could be a viable drug target for this lethal brain cancer in adults.

The study also found that the same Rictor/mTorc2 molecular pathway serves the opposite function in SHH medulloblastoma formation, acting as a tumor suppressor. Findings suggest that if the same drug treatment is used for treating SHH medulloblastoma in children, it could potentially have an adverse effect and promote growth of the tumors.

Ultimately, the study demonstrates that Rictor/mTORC2 has opposing functions in glioblastomas in adults and SHH medulloblastomas in children. While drug therapies targeting Rictor/mTORC2 may be successful in adults, the findings reveal the risks of treating children with pediatric brain tumors when using the same therapies.

The grant

Continuing the study of brain tumors, Dr. Zhu recently received a $575,000 grant from DoD to research benign gliomas, with the hope of gaining a greater understanding of how the tumors form. Low-grade gliomas, or benign brain tumors, are the most common brain tumors in children. While not lethal like their high-grade counterpart, these tumors can lead to significant neurological defects, permanently impacting a child’s quality of life. Most commonly, the tumor can impair vision, often leading to blindness.

Since the tumors only occur in children under the age of eight, Dr. Zhu believes they are linked to neural stem or progenitor cells that exist in the optic nerve only during development, or when children are under eight-years-old. To test if his hypothesis is correct, Dr. Zhu will develop a preclinical model that mimics human brain tumors to study the development of the optic nerve. If his theory proves correct, Dr. Zhu’s long-term goal is to develop a strategy that prevents the tumor formation from ever occurring, ultimately preventing vision loss in children. The grant begins in July and will run for three years.

 

Coenzyme Q10

Supplement might help kidney disease

Coenzyme Q10

A research team was able to “rescue” phenotypes caused by silencing the fly CoQ2 gene by providing nephrocytes with a normal human CoQ2 gene, as well as by providing flies with Q10, a popular supplement.

A new study led by Children’s National research scientists shows that coenzyme Q10 (CoQ10), a popular over-the-counter supplement sold for pennies a dose, could alleviate genetic problems that affect kidney function. The work, done in genetically modified fruit flies — a common model for human genetic diseases since people and fruit flies share a majority of genes — could give hope to human patients with problems in the same genetic pathway.

The new study, published April 20 by Journal of the American Society of Nephrology, focuses on genes the fly uses to create CoQ10.

“Transgenic Drosophila that carry mutations in this critical pathway are a clinically relevant model to shed light on the genetic mutations that underlie severe kidney disease in humans, and they could be instrumental for testing novel therapies for rare diseases, such as focal segmental glomerulosclerosis (FSGS), that currently lack treatment options,” says Zhe Han, Ph.D., principal investigator and associate professor in the Center for Cancer & Immunology Research at Children’s National and senior study author.

Nephrotic syndrome (NS) is a cluster of symptoms that signal kidney damage, including excess protein in the urine, low protein levels in blood, swelling and elevated cholesterol. The version of NS that is resistant to steroids is a major cause of end stage renal disease. Of the more than 40 genes that cause genetic kidney disease, the research team concentrated on mutations in genes involved in the biosynthesis of CoQ10, an important antioxidant that protects the cell against damage from reactive oxygen.

Drosophila pericardial nephrocytes perform renal cell functions including filtering of hemolymph (the fly’s version of blood), recycling of low molecular weight proteins and sequestration of filtered toxins. Nephrocytes closely resemble, in structure and function, the podocytes of the human kidney.  The research team tailor-made a Drosophila model to perform the first systematic in vivo study to assess the roles of CoQ10 pathway genes in renal cell health and kidney function.

One by one, they silenced the function of all CoQ genes in nephrocytes. If any individual gene’s function was silenced, fruit flies died prematurely. But silencing three specific genes in the pathway associated with NS in humans – Coq2, Coq6 and Coq8 – resulted in abnormal localization of slit diaphragm structures, the most important of the kidney’s three filtration layers; collapse of membrane channel networks surrounding the cell; and increased numbers of abnormal mitochondria with deformed inner membrane structure.

Journal of the American Society of Nephrology September 2017 cover

The flies also experienced a nearly three-fold increase in levels of reactive oxygen, which the study authors say is a sufficient degree of oxidative stress to cause cellular injury and to impair function – especially to the mitochondrial inner membrane. Cells rely on properly functioning mitochondria, the cell’s powerhouse, to convert energy from food into a useful form. Impaired mitochondrial structure is linked to pathogenic kidney disease.

The research team was able to “rescue” phenotypes caused by silencing the fly CoQ2 gene by providing nephrocytes with a normal human CoQ2 gene, as well as by providing flies with Q10, a readily available dietary supplement. Conversely, a mutant human CoQ2 gene from an patient with FSGS failed to rescue, providing evidence in support of that particular CoQ2 gene mutation causing the FSGS. The finding also indicated that the patient could benefit from Q10 supplementation.

“This represents a benchmark for precision medicine,” Han adds. “Our gene-replacement approach silenced the fly homolog in the tissue of interest – here, the kidney cells – and provided a human gene to supply the silenced function. When we use a human gene carrying a mutation from a patient for this assay, we can discover precisely how a specific mutation – in many cases only a single amino acid change – might lead to severe disease. We can then use this personalized fly model, carrying a patient-derived mutation, to perform drug testing and screening to find and test potential treatments. This is how I envision using the fruit fly to facilitate precision medicine.”

Related resources:
News release: Drosophila effectively models human genes responsible for genetic kidney diseases
Video: Using the Drosophila model to learn more about disease in humans