FADS2 and breast carcinoma: Interestingly, FADS2 overexpression in MCF-7 breast cancer cells, which have no detectable basal Δ6-desaturase activity, increased the endogenous biosynthesis of the polyunsaturated fatty acids docosahexaenoic acid (22:6n-3) and docosapentaenoic acid (22:5n-6) via a delta-4 desaturation reaction, to add to the well-established delta-6 and delta-8 desaturation activity of the FADS2 gene product [190].