Mitophagy Inhibition Promotes Survival and Mitochondrial Function in MYC-driven HCC

Hepatocellular carcinomas (HCC) are genetically heterogeneous cancers frequently characterized by MYC gene amplification or hyperactivating {beta}-catenin (CTNNB1) mutations. Analysis of TCGA transcriptomics revealed that MYC-driven HCC tumors have decreased expression of mtDNA-encoded genes, but increased expression of nuclear-encoded mitochondrial genes. To investigate this apparent discrepancy, we generated MYC- and CTNNB1-driven murine HCCs, all of which displayed aberrant mitochondrial metabolism. Notably, MYC-driven tumors exhibited significant reductions in OXPHOS and TCA cycle activity that correlated with increased ROS levels, as well as elevated mitochondrial turnover through mitochondrial fission and mitophagy. MYC induces the expression of nuclear respiratory factor 1 (NRF1), which regulates DRP1 and other genes to promote receptor-mediated mitophagy. Knocking out DRP1 reduced mitophagy and ROS levels and promoted survival of HCC-bearing mice. These results identify elevated mitochondrial turnover as a potential therapeutic target in MYC-driven HCC. SignificanceHepatocellular carcinoma can arise from multiple oncogenes, making targeted therapy more difficult. Here we show that tumors with MYC amplification lose mitochondrial function via fission and mitophagy upregulation. Targeting mitochondrial quality control results in increased survival suggesting a therapeutic window in MYC-driven HCC.