Prostate cancer cells survive anti-androgen and mitochondrial metabolic inhibitors by modulating glycolysis and mitochondrial metabolic activities

Background: Most cancer cells are more glycolytic even under aerobic conditions compared with their normal counterparts. Recent evidence of tumor cell metabolism, however, shows that some tumors also increase mitochondrial oxidative phosphorylation (ox-phos) at some disease states during progression and/or development of drug resistance. Our data show that anti-androgen enzalutamide (ENZA) resistant prostate cancer (PCa) cells use more mitochondrial metabolism leading to higher ox-phos as compared to the ENZA-sensitive cells and can become vulnerable to mitochondrial metabolism targeted therapies. Methods: Seahorse assay, mass spectrometry and high resolution fluorescence confocal microscopy coupled with image analysis has been used to compare mitochondrial metabolism in ENZA-treated and -untreated anti-androgen-sensitive LNCaP and -resistant C4-2, CWR22ν1, and PCa2b cells. Ex vivo fluorescence microscopy and image analysis has been standardized to monitor mitochondrial electron transport (ETS) activity that likely increases ox-phos in circulating tumor cells (CTCs) isolated fom patients undergoing AR-targeted therapies. Results: Our data show that PCa cells that are resistant to anti-androgen ENZA switch from glycolysis to ox-phos leading to an increased ETS activity. ENZA pretreated cells are more vulnerable to ETS component complex I inhibitor IACS-010759 (IACS) and mitochondrial glutaminase inhibitor CB-839 that reduces glutamate supply to tricarboxylic acid cycle. CTCs isolated from 6 of 20 patient blood samples showed relatively higher ETS activity than the rest of the patients. All six patients have developed ENZA resistance within less than 6 months of the sample collection. Conclusion: The enhanced growth inhibitory effects of mitochondrial metabolic inhibitors IACS and CB-839 in ENZA pretreated PCa cells provides a rationale for designing a drug combination trial. Patients can be selected for such trials by monitoring the mitochondrial ETS activities in their CTCs to maximize success.