MALT1 protease as a regulator of anti-tumor immunity and tumor progression in diffuse midline glioma

PROJECT SUMMARY/ABSTRACT H3K27M-mutant diffuse midline glioma (DMG) is a devastating pediatric brain tumor. Surgical resection is difficult because these tumors are in delicate midbrain/brainstem locations and infiltrate into critical structures. Despite decades of clinical trials, H3K27M-mutant DMG is considered uniformly fatal, with a median overall survival of 9-11 months. Radiation therapy, which itself is highly toxic to the developing pediatric brain, extends survival by 2-3 months. Therefore, the development of safe and effective therapies for DMG is of utmost importance. I propose to evaluate the effect of inhibiting MALT1 on the pathogenesis of H3K27M-mutant DMG. MALT1 is the effector molecule of the CARMA/CARD-BCL10-MALT1 (CBM) signalosome, a cytoplasmic protein complex that drives downstream pro-survival NF-kB transcriptional activity. MALT1 possesses both scaffolding and protease activities. Our laboratory and others have demonstrated that MALT1 protease activity promotes cancer cell viability, proliferation, and migration/invasion in multiple cancer types. In addition to its role within cancer cells, MALT1 is also a critical regulator of immune cell responses, and our laboratory is investigating the impact of MALT1 protease in the tumor microenvironment (TME) of high-grade glioma. Based on my preliminary data, I hypothesize that inhibiting MALT1 proteolytic activity could provide dual benefit in H3K27M-mutant DMG, both via the direct effects of inhibiting MALT1 within the cancer cells and via the effects of inhibiting MALT1 protease within immune cells of the TME to promote anti-tumor immune activation. In Aim 1 of this proposal, we will evaluate the influence of MALT1 protease activity on the H3K27M-mutant DMG TME. Experimental techniques utilized in this aim will include use of murine models, single cell RNA sequencing, and multispectral immunofluorescence. In Aim 2 of this proposal, we will evaluate the impact of MALT1 protease inhibition on malignant features of H3K27M-mutant DMG cells, using a series of in vitro analyses. Finally, in Aim 3, we will analyze the impact of MALT1 protease inhibition, with or without radiation, in our orthotopic/syngeneic H3K27M-mutant DMG model. Overall, this project evaluates inhibition of MALT1 protease as a potential therapeutic approach for H3K27M- mutant DMG. Completion of this proposal will provide me with exceptional research training by an outstanding team of scientists and physician-scientists. This training experience will prepare me for a career as a physician- scientist who studies the molecular underpinnings of pediatric cancers to develop new and improved treatments.