Enhancement of the antitumor effect of 6-mercaptopurine by vitamin A.

Abstract

The inhibition of the growth of HeLa cells in culture by 6-mercaptopurine was greatly enhanced in combination with retinol, retinal or retinol acetate, but not in combination with retinoic acid or retinol palmitate. The antitumor effect of retinol palmitate combined with 6-mercaptopurine was examined in BDF1 mice with L1210 leukemia. The blood level of retinol, a strong potentiator of 6-mercaptopurine among vitamin A compounds, was increased in BDF1 mice after retinol palmitate injection. Retinol palmitate was found to enhance the antitumor effect of 6-mercaptopurine against murine L1210 leukemia to a significant extent (69% increase in life span).