Experimental study of antitumor effect of methyl-B12

We examined the antitumor effect of vitamin B12 (methyl-B12) using C3H/He, C57BL/6 and BALB/C mice for animals and MH134 hepatoma ascites cells, Lewis lung cancer cells and Ehrlich ascites tumor cells for tumor cells. At 1.0-10 micrograms/ml, methyl-B12 enhanced PHA- and Con-A-induced lymphocyte blastoformation of C3H/He mice. The growth of MH134 tumors on the backs of C3H/He mice were suppressed by the 7-day administration of 50 or 100 micrograms/day i.p. and their survival was longer than that of untreated mice. However, methyl-B12 administration did not positively affect the survival of C3H/He mice that had been irradiated with 60Co 300 R on the day before tumor cell inoculation. The growth of Ehrlich ascites tumor cells inoculated into BALB/C mice was also reduced at 17 and 19 days after tumor inoculation by administration of methyl-B12 50 micrograms/day i.p. and the mice survived longer than the untreated mice.