The biosynthesis of tumor-associated gangliosides starts from lactosylceramide (LacCer, Gg2Cer) by the transfer in the Golgi apparatus of a first sialic acid residue catalyzed by the GM3 synthase ST3Gal V to form GM3 (II3Neu5AcGg2Cer) (Figure 1). The gene discussed is ST3GAL5; the disease is neoplasm.