Characterization and Therapeutic Targeting of Surface Markers in Glioblastoma Pre-Clinical Models

Abstract

Glioblastoma (GBM) remains the most aggressive primary brain tumor in adults. Since 2005, Standard of Care (SoC) consists of surgical resection followed by radiation and adjuvant chemotherapy with temozolomide. Treatment failure is attributed to intratumoral heterogeneity with populations capable of mechanisms to repair damaged DNA. Given the lack of progress to improve patient outcomes, the current work encompasses how multi-omic approaches can be utilized to uncover novel biology in GBM and develop precision medicines to exploit these cancer specific phenomena. Using patient derived GBM samples I first used the surface marker CD133 to interrogate glioblastoma stem cells, a subpopulation of cells identified to withstand conventional therapies and lead to tumor relapse. I used a genome-wide CRISPR-Cas9 library to conduct an unbiased loss-of-function phenotypic screen to identify regulators of CD133. I then validated SOX2 as a direct transcription factor to PROM1 encoding CD133. These findings further show the untapped potential of CRISPR to uncover novel biology to directly apply to broader fields of stem cells and cancer biology. Next, I combed GBM data sets at transcriptomic and proteomic levels to identify understudied proteins as potential targets for immunotherapies. Glycoprotein nonmetastatic melanoma protein B (GPNMB) has previously been identified as a clinically relevant target in GBM and shown to be active in the tumor immune microenvironment. I found GPNMB to be upregulated in recurrent GBM and macrophage populations which can be exploited in a more comprehensive manner to treat GBM. Through a series of models, I elucidated how GPNMB influences GBM biology, its effectiveness as a target for Chimeric Antigen Receptor T-cells, and how it can be paired with CD133 therapies to provide better coverage of tumor cells. Together, these studies highlight how advances in pre-clinical models and technologies can be leveraged to develop new therapies in a rational manner.