Effect of pyridoxine and pyridoxal on the in vitro growth of human malignant melanoma.

The in vitro effect of vitamin B-6 supplementation on the growth of a human malignant melanoma cell line (M21-HPB) was investigated. Varying concentrations of pyridoxine (PN) or pyridoxal (PL) were added to cell cultures and incubated for 12 days. Pharmacologic levels of PL (0.25-0.5 mM) resulted in significant reductions in cell proliferation. Physiologic levels (0.005 mM) did not retard growth. Cells incubated with PN showed growth stimulation. Intracellular levels of PL and pyridoxal 5'-phosphate (PLP) were increased in cells exposed to pharmacologic PL (0.05-0.5 mM) concentrations, but not PN. These data suggest that PL or PLP may be involved in regulating the growth of melanoma cells and that vitamin B-6 may have potential use as an antineoplastic agent.