Abstract
Clinical targeting of the altered metabolism of tumor cells has long been considered an attractive hypothetical approach. However, this strategy has yet to perform well clinically. Metabolic redundancy is among the limitations on effectiveness of many approaches, engendering intrinsic single-agent resistance or efficient evolution of such resistance. We describe new studies of the multi-target, tumor-preferential inhibition of the mitochondrial tricarboxylic acid (TCA) cycle by the first-in-class drug CPI-613® (devimistat). By suppressing the TCA hub, indispensable to many metabolic pathways, CPI-613 substantially reduces the effective redundancy of tumor catabolism. This TCA cycle suppression also engenders an apparently homeostatic accelerated, inefficient consumption of nutrient stores in carcinoma cells, eroding some sources of drug resistance. Nonetheless, sufficiently abundant, cell line-specific lipid stores in carcinoma cells are among remaining sources of CPI-613 resistance in vitro and during the in vivo pharmacological drug pulse. Specifically, the fatty acid beta-oxidation step delivers electrons directly to the mitochondrial electron transport system (ETC), by-passing the TCA cycle CPI-613 target and producing drug resistance. Strikingly, tested carcinoma cell lines configure much of this fatty acid flow to initially traverse the peroxisome enroute to additional mitochondrial beta-oxidation. This feature facilitates targeting as clinically practical agents disrupting this flow are available. Two such agents significantly sensitize an otherwise fully CPI-613-resistant carcinoma xenograft in vivo. These and related results are strong empirical support for a potentially general class of strategies for enhanced clinical targeting of carcinoma catabolism.