Comparison of antitumor activity of vitamins K1, K2 and K3 on human tumor cells by two (MTT and SRB) cell viability assays

Vitamin K (VK) congeners (VK1, VK2 and VK3) have been used as antihemorrhagic agents, while VK3 has also been found to inhibit growth in various rodent and human tumor cells. We have compared the antitumor activities of vitamin K1, K2, and K3 against a panel of human cancer cell lines. For each test agent, a dose-response profile was generated by using an MTT (3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) and an SRB (sulforhodamine B) assay. Both assays yielded similar results. The respective ID50 values of VK3 in five hepatoma cell lines, HA59T, HA22T, PLC, HepG2, and Hep3B, of increasing differentiation state, were 42, 36, 28, 27, and 20 μM. For nasopharyngeal carcinoma (CG1), leukemia (U937), oral epidermoid carcinoma (KB), and breast carcinoma (BC-M1) cells, the ID50 values of VK3 were 26, 15, 25, and 33 μM, respectively. For all the above cells, the ID50 values of VK1 ranged from 6 to 9 mM, and the ID50 values of VK2 ranged from 1 to 2 mM. Thus, the relative potencies of antitumor activity of VK3 compared to VK2 and to VK1 are about 60- and 300-fold, respectively. These results support the preference for use of VK3 over VK1 and VK2 in cancer therapy.