Targeting Ketone Body Metabolism in Mitigating Gemcitabine Resistance

Chemotherapy is often combined with surgery for muscle invasive and non-muscle invasive bladder cancer. However, 70% of the patients recur within 5 years. Metabolic reprogramming is an emerging hallmark in cancer chemoresistance. Here, we report a gemcitabine resistance mechanism which promotes cancer reprogramming via the metabolic enzyme, OXCT1. This mitochondrial enzyme, responsible for the rate-limiting step in β-hydroxybutyrate (βHB) catabolism, was elevated in muscle invasive disease and in chemo-resistant bladder cancer patients. Resistant orthotopic tumors presented an OXCT1-dependent rise in mitochondrial oxygen consumption rate, ATP, and nucleotide biosynthesis. In resistant bladder cancer, knocking out OXCT1 restored gemcitabine sensitivity, and administering the non-metabolizable βHB, enantiomer (S-βHB) only partially restored gemcitabine sensitivity. Suggesting an extra-metabolic role for OXCT1, multi-omics analysis of gemcitabine sensitive and resistant cells revealed an OXCT1-dependent signature with the transcriptional repressor, OVOL1, as a master regulator of epithelial differentiation. The elevation of OVOL1 target genes was associated with its cytoplasmic translocation and poor prognosis in a chemotherapy-treated BCa patient cohort. The knockout of OXCT1 restored OVOL1 transcriptional repressive activity by its nuclear translocation. Orthotopic mouse models of bladder cancer supported OXCT1 as a mediator of gemcitabine sensitivity through ketone metabolism and regulating cancer stem cell differentiation. Three independent clones of 5637 parental and 5637 gemcitabine resistant cells were analyzed for gene expression differences associated with gemcitabine resistance.