Abstract 1822 Deciphering the Proteomic Landscape: Understanding the Tumor Microenvironment in Diffuse Midline Glioma

Diffuse midline glioma (DMG) is a uniformly fatal and aggressive brain tumor predominantly affecting children aged 2-10, with limited treatment options and no approved drugs available due to the blood-brain barrier (BBB) hindering effective therapeutic delivery. Despite extensive efforts, promising preclinical candidates have failed to translate into therapeutic efficacy in human clinical trials, highlighting a disconnect between existing preclinical models and their representation of human disease. To enhance preclinical models to become predictive of therapeutic response in humans, it is essential to comprehensively understand both tumor biology and the specific environmental factors influencing tumor growth. Currently, the tumor microenvironment in DMG has been insufficiently studied. In this work, the tumor microenvironment was probed between DMG tumors and BBB vasculature cells to identify mechanisms of tumor proliferation. Protein analyses were performed on cell lysates and conditioned media of two patient-derived DMG tumor cell models, as well as BBB cells (astrocytes, pericytes, and endothelial cells) to identify proteases involved DMG progression using mass spectrometry and zymography techniques. Proteomic data generated identified 122 and 67 unique proteins in cell lysates and conditioned media, respectively, with distinct patterns of expression in tumor cells versus healthy primary human brain cells. Preliminary results show the identified proteins exhibit distinct involvement in various pathways, including those related to metabolism and proliferation. These findings will inform future lab work to create an optimal model of DMG through judicious selection of optimal in vitro conditions, ensuring the successful establishment of a human-representative model tailored to be compatible with the growth medium/matrix, facilitating both proliferation and preservation of the authentic tumor biology. Dana-Farber/Harvard Cancer Center and MIT Bridge Project, AACR-Day One Biopharmaceuticals Pediatric Cancer Research Fellowship, Ford Foundation Predoctoral Fellowship, MIT Summer Research Program, Jerome A. Schiff Fellowship.