FASN and breast cancer: Increased de novo FA biosynthesis and FASN upregulation has also been observed in breast cancer, melanoma, and hepatocellular carcinoma (4), and de novo FA biosynthesis and lipogenesis has been shown to be essential for protein palmitoylation of Ras, Wnt (48), calnexin (49), and Src (50) in proliferating cells (51, 52).