Prevention of experimental cancer and immunostimulation by vitamin E (immunosurveillance)

Eighty young adult male Syrian hamsters were divided into four equal groups. Group 1 animals had the right buccal pouches painted with a 0.1% solution of 7,12 dimethylbenz(a)anthracene (DMBA) three times per wk for 28 wk. Group 2 animals were similarly painted with DMBA for 28 wk but were also given 140 micrograms vitamin E in 0.4 ml mineral oil three times weekly on days alternate to DMBA painting. Group 3 animals were used as DMBA-vehicle controls. Group 4 animals were vitamin E controls. Animals were killed after 28 wk, the pouches photographed and tumors counted, measured. The pouches were fixed in formalin, sectioned in paraffin and studied histologically and histochemically for tumor necrosis factors alpha and beta. All animals in Group 1 and 3 had gross tumors of the right buccal pouch. None of the animals in Group 2 had grossly visible tumors. Microscopic studies revealed that, while no gross tumors were seen in the Group 2 animals, there was histologic evidence of dysplasia and early carcinoma-in-situ undergoing degeneration. Immunohistochemical staining revealed a dense infiltrate of mononuclear cells adjacent to tumor sites with a large number of cytotoxic T lymphocytes and macrophages. Vitamin E appears to prevent tumor formation by stimulating a potent immune response to selectively destroy tumor cells as they begin to develop into recognizable microscopic foci of carcinoma.