L-Selenocystine Dihydrochloride is the HCl salt of L-Selenocystine (S253100) which is a diselenide-bridged amino acid which show chemopreventive activity against tobacco-derived nitrosamine (NNK) induced lung tumors. It causes apoptosis in A375, HepG2 and MCF7 cancer cells by inducing intracellular reactive oxygen species.