Acetyl-CoA Carboxylase α Is Essential to Breast Cancer Cell Survival

Activation of de novo fatty acid synthesis is a characteristic feature of cancer cells. We have recently described an interaction between acetyl-CoA carboxylase α (ACCα), a key enzyme in fatty acid synthesis, and BRCA1, which indicates a possible connection between lipid synthesis and genetic factors involved in susceptibility to breast and ovarian cancers. For this reason, we explored the role of ACCα in breast cancer cell survival using an RNA interference (RNAi) approach. We show that specific silencing of either the ACCα or the fatty acid synthase (FAS) genes in cancer cells results in a major decrease in palmitic acid synthesis. Depletion of the cellular pool of palmitic acid is associated with induction of apoptosis concomitant with the formation of reactive oxygen species (ROS) and mitochondrial impairment. Expression of a small interfering RNA (siRNA)–resistant form of ACCα mRNA prevented the effect of ACCα-RNAi but failed to prevent the effect of FAS gene silencing. Furthermore, supplementation of the culture medium with palmitate or with the antioxidant vitamin E resulted in the complete rescue of cells from both ACCα and FAS siRNA–induced apoptosis. Finally, human mammary epithelial cells are resistant to RNAi against either ACCα or FAS. These data confirm the importance of lipogenesis in cancer cell survival and indicate that this pathway represents a key target for antineoplastic therapy that, however, might require specific dietary recommendation for full efficacy. (Cancer Res 2006; 66(10): 5287-94)