Cytotoxic effects of 24R,25-dihydroxycholecalciferol on the proliferation of various tumor cell lines in vitro and its antitumor effects in vivo.

24R,25(OH)2D3, one of the endogenous active metabolites of vitamin D3, showed suppressive effects on the proliferation of various tumor cells in vitro, and showed a suppressive effect on the growth of human osteosarcoma transplanted in nude mice. 24R,25(OH)2D3 increased bone strength lowered by the tumor burden which causes abnormal calcium metabolism and results in hypercalcemia.