Cellular Plasticity and equilibrium in GBM Progression

To advance our understanding of therapeutic resistance in Glioblastoma (GBM), it is essential to characterize the individual cell during therapy those fueling tumor recurrence in GBM. However, it is challenging to study the GBM during conventional radio- and chemotherapy due to limited accessibility to patient samples during this time period. Our lab performed a single-cell RNA sequencing screen in the patient-derived xenograft model of GBM during temozolomide (TMZ) therapy. Our analysis revealed that the Ribonucleotide Reductase Regulatory Subunit 2 (RRM2) mediates deoxynucleoside triphosphates (dNTPs) production necessary for proper DNA replication stable cell growth, promotes metabolic adaptation to TMZ therapy, and initiate recurrence. We have identified a novel mechanism where RRM2-mediated dCTP and dGTP can enhance the DNA repair in response to TMZ and promotes resistance to therapy. Based on this, we hypothesize that RRM2-mediated RNR activity is critical for chemoresistance in GBM. To investigate this hypothesis, we will first characterize the RNR subunit expression pattern and activity concerning dNTP biogenesis in different subtypes of GBM (Aim 1). Next, we intend to elucidate the RNR-mediated chemoresistance in GBM (Aim 2). And Finally, we will evaluate a blood-brain permeable RRM2 inhibitor to prevent RNR-mediated chemoresistance in GBM. We established collaboration with Nanopharmaceutic, which holds the patent for producing clinical-grade 3-AP and will provide us with 3-AP to test its efficacy further and advance our understanding of the mechanism of action by which it can be used to treat GBM patients. Collectively, our studies will provide novel insights regarding changes in dNTP synthesis that are associated with GBM adaptation and resistance during chemotherapy. This information, in turn, is expected to reveal novel approaches for delaying, if not preventing, tumor recurrence.