STEM-21. INHIBITING ADENINE SYNTHESIS ATTENUATES GLIOBLASTOMA CELL STEMNESS AND TEMOZOLOMIDE RESISTANCE

Abstract

Abstract Glioblastoma (GBM) is a lethal brain cancer that exhibits high levels of drug resistance, a feature partially imparted by tumor cell stemness. Recent work has shown that homozygous MTAP deletion, a frequent genetic alteration in GBM, promotes the stemness of GBM cells. Here, exploiting the MTAP loss-conferred deficiency in adenine salvage, we demonstrated that subtle levels of adenine blockade via treatment with Alanosine, an inhibitor of de novo adenine synthesis, attenuate the stemness of MTAP-null GBM cells. Transcriptomic profiling performed on Alanosine-treated GBM cells revealed a reduction of mitochondrial DNA-encoded gene expression. Furthermore, Seahorse XF analysis showed that Alanosine treatment led to a reduction in mitochondrial respiration and eliminated GBM cells’ spare respiratory capacity, an important metabolic measure of cell fitness that is representative of their ability to respond to oxidative stress. Importantly, long term adenine shortage via treatment with low doses of Alanosine resulted in similarly compromised mitochondria functionality and attenuated GBM cells’ stemness. In further supporting this adenine blockade – compromised mitochondria – reduced stemness cascade, treatment with a mitochondrial respiration inhibitor attenuated the stemness of GBM cells, suggesting the importance of mitochondrial function in maintaining GBM stemness. Finally, in agreement with the diminished stemness and compromised mitochondrial function, we showed that Alanosine sensitized GBM cells to temozolomide (TMZ) in both in vitro cultures and in an orthotopic GBM model. Collectively, these results identify critical roles of adenine supply in maintaining stemness and mitochondrial function in GBM cells, suggest a targeted method of abrogating stemness and chemoresistance in GBMs, and support targeting adenine synthesis as a complementary approach for treating the half of GBMs harboring MTAP deletions.