Cytotoxic activity of cobalamin in cultured malignant and nonmalignant cells

The cytotoxic effect of cobalamin (vitamin B12) on the growth of malignant and nonmalignant cell lines in culture has been examined. Among the four cobalamins studied, 5'-deoxyadenosylcobalamin, an enzymatically active derivative, was an effective cytotoxic agent. The data indicated that adenosylcobalamin seemed to act selectively on fast-growing malignant cells. Methylcobalamin was also effective at elevated concentrations. Cyanocobalamin was not toxic to all cell lines studied. Hydroxocobalamin at very high concentrations was able to slightly decrease growth of certain cell lines. The results support the hypothesis that the cytotoxic effect of cobalamin was associated with the metabolic activities of this vitamin at the cellular level. Also, cobalamin may be a potential antitumor agent.