Suppression by Vitamins D<sub>2</sub> and D<sub>3 </sub>of Hamster Cheek Pouch Carcinoma Induced with 9,10-Dimethyl-1,2-benzanthracene

Abstract

Local application of vitamins D<sub>2</sub> and D<sub>3</sub> caused inhibition of tumor formation in the hamster cheek pouch, induced by topical treatment with DMBA. These results and data from the literature are used in an attempt to explain the mechanism of carcinogenesis by DMBA, and the inhibition of this process by vitamin D. In tumor cells the amount of alkaline phosphatase and the amount of calcium bound to the cell membrane are both decreased. It is probable that the protein molecule alkaline phosphatase can also act as calcium binding protein. The decreased amount of calcium bound to the membrane of tumor cells leads to increased permeability, with an increased and less controlled flow of metabolites to and from the cytoplasm, resulting in a decreased control of the mitotic process. Vitamins D cause induction of the synthesis of alkaline phosphatase/calcium binding protein, and this may explain the marked inhibition of DMBA carcinogenesis in animals treated simultaneously with DMBA and vitamin D. This effect of vitamin D is probably not specific, and there are indications that other substances which cause induction of alkaline phosphatase also inhibit tumor formation.