A study on the effect of vitamin A deficiency and supplementation on tumorigenesis in mice.

: The effect of vitamin A deficiency and supplementation on the incidence of tumors, tumor growth and life expectancy was assessed in a murine model. Although the nature of response varied with respect to the tumor types studied, in general an increase in incidence of tumor take and further growth was noted with a concomitant fall in the survival rates in the group maintained on a vitamin A deficient diet. Supplemental vitamin A produced a prolongation of the latent period and delayed appearance of the tumor, reduced incidence and growth and improved life expectancy. Such effects seem to be mediated by a direct action of the vitamin on tumor cells, as well as through the host immune system, as revealed by nucleic acid synthetic patterns and nature of changes in the lymphocyte/neutrophil ratio, thymus weight and PHA-induced blastogenesis of peripheral lymphocytes.