Citrate Synthase Knockdown Suppresses Cell Proliferation and Induces Apoptosis in Select Human Cancer Cell Lines

Citrate synthase (CS) catalyzes the first reaction in the tricarboxylic acid (TCA) cycle and is one of the rate-limiting and regulatory enzymes of the TCA cycle. How CS influences human cells beyond its direct roles in carbohydrate metabolism and energy production is poorly understood. In this study, we used RNA interference (RNAi) to knockdown CS expression in three diverse human cancer cell lines, HCT116, HT-1080, and HepG2, and assessed changes in their cellular behaviors. In all three cell lines, the loss of CS led to are duction in cell proliferation, increased apoptosis, lower mitochondrial membrane potentials, higher reactive oxygen species (ROS) production, and reduced ATP levels. We then performed transcriptome analyses in the three cell lines, identified pathways related to the cell cycle and apoptosis that might elucidate the mechanisms underlying those cellular changes, and further verified the mRNA expression changes in specific genes associated with the apoptotic pathways. Taken together, our results suggest that CS regulates a broad spectrum of human cellular processes.