Vitamin E protection against tumor formation by transplanted murine sarcoma cells

Mice fed vitamin E at a level of 0.5 g DL-alpha-tocopheryl acetate/kg diet demonstrated decreased incidence and rate of appearance of tumors produced by transplanted sarcoma cells (K3T3), compared to control groups fed diets without the vitamin supplement. Protection was dependent on the degree of unsaturation of dietary fat and on the size of the tumor cell challenge. When vitamin E was increased 10-fold (to 5 g/kg diet), the protective effect was no longer observed. Protection may be mediated through the host immune system, because sublethal, whole-body X-irradiation abrogated differences in tumor development between the +E and the -E mice. Studies with in vitro immunization showed that treatment of the K3T3 cell with vitamin E enhanced its ability to induce a cytotoxic response. It appears that the direct effect of vitamin E is on the tumor cell rather than on the immune system, since spleen cells from mice fed diets with and without vitamin E supplementation were indistinguishable in their response to untreated K3T3 cells. K3T3 cells treated with excessive levels of vitamin E were unable to induce a cytotoxic response, a result that correlates with the loss of protection against tumor development when massive doses of vitamin E were fed.