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[The immunological role of carotenoids in the prevention of cancer].

Epidemiological studies have suggested that the intake of green-yellow vegetables decrease the risk of cancer. Vitamin A, which is abundantly present in green-yellow vegetables in the form of provitamin A, was demonstrated to inhibit chemical and viral-carcinogenesis in experimental animals. However, little is known about the mechanism of anti-carcinogenic effect of vitamin A. Our data seem to support a hypothesis that vitamin A may contribute to the prevention of cancer by augmenting an immunosurveillance system. We found that vitamin A and provitamin A, beta-carotene, enhanced tumor immunity using a syngeneic murine tumor system.