Fatty acid metabolism in breast cancer cells: differential inhibitory effects of epigallocatechin gallate (EGCG) and C75

Endogenous fatty acid metabolism is crucial to maintain the cancer cell malignant phenotype. Lipogenesis is regulated by the enzyme fatty acid synthase (FASN); and breakdown of fatty acids is regulated by carnitine palmitoyltransferase-1 (CPT-I). FASN is highly expressed in breast cancer and most common human carcinomas. Several compounds can inhibit FASN, although the degree of specificity of this inhibition has not been addressed. We have tested the effects of C75 and (-)-epigallocatechin-3-gallate (EGCG) on fatty acid metabolism pathways, cellular proliferation, induction of apoptosis and cell signalling in human breast cancer cells. Our results show that C75 and EGCG had comparable effects in blocking FASN activity. Treating cancer cells with EGCG or C75 induced apoptosis and caused a decrease in the active forms of oncoprotein HER2, AKT and ERK1/2 to a similar degree. We observed, in contrast, marked differential effects between C75 and EGCG on the fatty acid oxidation pathway. While EGCG had either no effect or a moderate reduction in CPT-I activity, C75 stimulated CPT-I activity (up to 129%), even in presence of inhibitory levels of malonyl-CoA, a potent inhibitor of the CPT-I enzyme. Taken together, these findings indicate that pharmacological inhibition of FASN occurs uncoupled from the stimulation of CPT-I with EGCG but not with C75, suggesting that EGCG might be free of the CPT-I related in vivo weight-loss that has been associated with C75. Our results establish EGCG as a potent and specific inhibitor of fatty acid synthesis (FASN), which may hold promise as a target-directed anti-cancer drug.