Mutant IDH1 Glioma Project

Glioma genetic models are needed to uncover mechanisms that mediate tumor progression, the interplay with the tumor microenvironment (TME) and response to therapeutics. We have generated the first genetically engineered mutant IDH1 mouse glioma model and isolated primary neurospheres (NS) from the tumors, which exhibit cancer stem cell-like properties. This has enabled us to develop a transplantable mIDH1 glioma model amenable to testing novel therapies. NS are derived from fully immune-competent (C57BL/6) mice, thus allowing examination of the TME and the impact of tumor mutations on the immune response. Our goals are to assess the effect of mIDH1 on transcription (using mRNA-seq) and on global DNA and histone methylation. The mIDH1 glioma model will also be used to identify promoter/enhancer region-specific changes in histone methylation marks (using chromatin immunoprecipitation followed by deep sequencing, or ChIP-seq). We are collaborating with Dr. Mats Ljungman, who pioneered bromouridine sequencing (Bru-seq), to identify and quantify nascent mRNA and gene transcription rates. Uncovering epigenetic patterning of histone 3 hypermethylation and cytosine modifications using next generation sequencing (NGS) technologies will contribute to the identification of novel pathways and gene regulatory networks which will provide novel insights into disease biology and uncover novel therapeutic targets.

DIPG Project

Diffuse intrinsic pontine glioma (DIPG) is a brainstem tumor that affects mainly children and for which there is no effective treatment. The most frequent DIPG mutations affect the N-terminal tail of histone variant H3.3 (encoded by H3F3A) and histone variant H3.1 (encoded by HIST1H3B) and result in the change of a lysine to methionine at residue 27, precluding methylation or acetylation of this key regulatory post-translational modification. In addition, six recurrent somatic activating mutations in ACVR1, which encodes for a bone morphogenetic protein (BMP) Type-I receptor, have also been identified in DIPG tumors. BMP has very context-specific roles in the brain during development but its role in pediatric cancer remains unknown. We are using the Sleeping Beauty Transposase System to generate spontaneous in vivo tumor models that will allow us to analyze the contributions of these genes to DIPG pathogenesis. This work will elucidate how ACVR1 and H3K27M mutations contribute to DIPG progression and evaluate their impact on tumor response to DNA damaging agents. These studies will uncover novel therapeutic targets to improve prognosis for patients who suffer from DIPG.

Pediatric High Grade Glioma Project

Pediatric high-grade gliomas are a currently incurable brain tumor with a median survival of 9-15 months. While progress is being made in understanding the K27M substitution found in midline tumors, the G34R/V mutations in tumors of the cerebral hemispheres in children and young adults have been left behind. A major limitation in deriving further biological insight and therapeutic opportunities associated with these mechanisms is the lack of available H3G34 model systems. We aim to address this by taking novel experimental approaches to developing novel mouse models of this subtype of glioma. We recently created a Sleeping Beauty-based H3G34 model using the transposase to simultaneously incorporate NRAS-V12, H3.3G34R, shATRX and shTP53 in neural progenitors. This project aims to harness our team’s experience in pediatric glioma genomics/epigenomics, mouse modeling and biology, and therapeutic targeting, with the potential to carry out transformative research in this subtype of glioma with unmet clinical need.

Immunotherapy Development

The adult and pediatric brain tumor models we have established in our lab are ideal for developing and testing novel immunotherapies as they are implemented in mice with a fully competent immune system. We are using both immune mediated gene therapy strategies and nanoparticle-based vaccination approaches to develop new treatment strategies for these devastating brain cancers. I have made major contributions to elucidating the immune suppressive nature of the tumor microenvironment (TME) in glioma. My group uncovered the role of plasmacytoid dendritic cells as antigen presenting cells (APCs) within the brain; uptake of tumor antigens within the TME, migration to the draining lymph node and triggering effective adaptive anti-tumor immunity, which results in the regression of a large tumor mass and immunological memory. Using KO mouse models and bone marrow adoptive transfer technologies, we established the cellular and molecular signature of immune cells responsible for therapeutic efficacy and long-term memory in brain cancer models. We uncovered that the immune cells which are present within the TME and are responsible for tumor immunity are bone marrow (BM) derived. We described the role played by Toll-like receptor 2 (TLR2) signaling on BM derived, tumor infiltrating dendritic cells (DCs) in mediating tumor regression, long term survival and anti-tumor immunological memory in response to combined conditional cytotoxic, immune-stimulatory gene therapy. Further, we demonstrated that TLR2 activation was elicited by an endogenous, cancer cells’ derived TLR ligand, i.e., HMGB1 (a transcription factor that binds to DNA in live cells) which is released from dying cancer cells in response to cancer ablative therapies. We propose the use of circulating levels of HMGB1 as a biomarker to monitor tumor progression and therapeutic efficacy. We are investigating the molecular and cellular biology effects elicited by circulating HMGB1 in mediating immune cells’ trafficking into the TME.

Clinical Trials

Our innovative work has led to an FDA-approved gene therapy Phase 1 clinical trial for malignant brain cancer which is currently enrolling patients at the University of Michigan.

GBM is the most aggressive primary brain tumor with a 5-year survival rate of <5%. Attempts at eliciting a clinically relevant anti-GBM immune response in these patients have met with limited success, due to tumor immune evasion, and a paucity of dendritic cells (DCs) within the brain. In light of the immunosuppressive nature of GBM, I hypothesized that stimulating an immune response directly from within the TME would elicit effective anti-tumor immunity. I showed that increasing the number of brain tumor infiltrating antigen presenting cells [elicited by expressing fms-like tyrosine kinase ligand (Flt3L) within the TME] in combination with the cytotoxic effects of TK (+GCV) induces effective tumor antigen (Ag) uptake, migration of DCs to draining lymph nodes (dLN), and presentation of tumor antigen to naïve T-cells culminating in effective anti-tumor immunity. Further, the induction of immunological memory mediates the elimination of a second GBM implanted in the contralateral hemisphere of long-term survivors. This led to a Phase I clinical trial: “A non-randomized, open-label dose-finding trial of combined cytotoxic and immune‐stimulatory strategy for the treatment of primary GBM, utilizing Ad-hCMV-TK expressing herpes simplex virus thymidine kinase, and Ad-hCMV-Flt3L expressing fms-like tyrosine kinase ligand” recently finished accrual at our institution (IND number BB14574, clinicaltrials.gov number NCT01811992).

Impact of Research Program

I have received several awards for my research program, including the Medallion Group Endowed Chair in Gene Therapeutics Research at Cedars-Sinai Medical Center in 2004. In August 2008, I received the “Women of Action Award” from the Israel Cancer Research Fund (ICRF), Beverly Hills, California, for achievements in the field of Brain Cancer Biology and Therapeutics. In April 2014, I was named the R. C. Schneider Collegiate Professor of Neurosurgery at the University of Michigan Medical School, Ann Arbor, USA, and in 2015 I received the Javits Award from the NIH for the grant, “Immune-suppressive Myeloid Cells in the Glioma Microenvironment: Signaling Mechanisms and Novel Therapeutic Strategies.” In November 2018, I received the Dean’s Basic Science Research Award for outstanding contributions to the University of Michigan Medical School in basice biomedical science research related to genetically engineerd mouse glioma models and epigenetic regulation of therapeutic responce. I have also received the Rogel Cancer Center Scholars Award and was an elected AAAS Fellow, both in 2019. In 2020 I became an elected Fellow of the Latin American Academy of Sciences (ACLA), Venezuela Caracas in 2020.