Inhibiting MYC-regulated Glutaminase Metabolic Axis is an Effective Synthetic Lethal Approach for Treating Chemoresistant Cancers

Amplification and expression of the MYC oncogene in tumor cells, including ovarian cancer cells correlates with poor responses to chemotherapy. As MYC is not directly targetable, we have analyzed molecular pathways downstream of MYC to identify potential therapeutic targets. We have discovered that ovarian cancer cells overexpressing glutaminase (GLS), a MYC target and a key enzyme in glutaminolysis, are intrinsically resistant to platinum chemotherapy, and are enriched in the intracellular antioxidant glutathione. Deprivation of glutamine by glutamine-withdrawal, GLS knockdown, or exposure to the GLS inhibitor CB-839 resulted in robust induction of reactive oxygen species in high GLS-expressing but not low GLS-expressing ovarian cancer cells. Treatment with CB-839 rendered GLShigh 10 cells vulnerable to the poly(ADP-ribose) polymerase (PARP) inhibitor, olaparib, and prolonged survival in tumor-bearing mice. Our findings suggest that applying a combined therapy of GLS inhibitor and PARP inhibitor could effectively treat chemoresistant ovarian cancers, especially those with high GLS expression. MYC ChIP-seq experiments in two human cancer cell lines. ChIP-seq library preparation and sequencing were performed by NextSeq500 platform.