Induction of apoptosis in an androgen-dependent mouse mammary carcinoma cell line by methylcobalamin.

SC-3 is a cloned cell line derived from an androgen-dependent mouse mammary tumor (Shionogi Carcinoma 115). A physiological level of androgen stimulates the growth of SC-3 cells through the production of androgen-induced growth factor. Methylcobalamin (MeCbl), one of the active cobalamins, inhibits the growth of SC-3 cells stimulated by androgen. It is known that apoptosis has an important role in tumor growth. The specific aim of this study is to examine the effects of MeCbl, in the presence of androgen, on apoptosis in SC-3 cells. Morphological analysis revealed budding nuclei and chromatin condensation in cells cultured with MeCbl, but few in cells cultured without MeCbl. Low molecular weight DNA extracted from cells cultured with or without MeCbl was analysed by gel electrophoresis. A characteristic nucleosomal size ladder was detected in the culture with MeCbl. The terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end-labelling method was also used to evaluate apoptotic cell death in SC-3 cells. Apoptosis was observed more frequently in SC-3 cells treated with MeCbl than in those without MeCbl. These results demonstrate that androgen-dependent SC-3 cells undergo apoptosis by MeCbl even if in the presence of androgen.