Dichloroacetate induces apoptosis and cell-cycle arrest in colorectal cancer cells

BACKGROUND: Cancer cells are highly dependent on glycolysis. Our aim was to determine if switching metabolism from glycolysis towards mitochondrial respiration would reduce growth preferentially in colorectal cancer cells over normal cells, and to examine the underlying mechanisms. METHODS: Representative colorectal cancer and non-cancerous cell lines were treated with dichloroacetate (DCA), an inhibitor of pyruvate dehydrogenase kinase. RESULTS: Dichloroacetate (20 mM) did not reduce growth of non-cancerous cells but caused significant decrease in cancer cell proliferation (P=0.009), which was associated with apoptosis and G(2) phase cell-cycle arrest. The largest apoptotic effect was evident in metastatic LoVo cells, in which DCA induced up to a ten-fold increase in apoptotic cell counts after 48 h. The most striking G(2) arrest was evident in well-differentiated HT29 cells, in which DCA caused an eight-fold increase in cells in G(2) phase after 48 h. Dichloroacetate reduced lactate levels in growth media and induced dephosphorylation of E1α subunit of pyruvate dehydrogenase complex in all cell lines, but the intrinsic mitochondrial membrane potential was reduced in only cancer cells (P=0.04). CONCLUSIONS: Pyruvate dehydrogenase kinase inhibition attenuates glycolysis and facilitates mitochondrial oxidative phosphorylation, leading to reduced growth of colorectal cancer cells but not of non-cancerous cells.