Antitumor effect of 22-oxacalcitriol on estrogen receptor-negative MDA-MB-231 tumors in athymic mice.

Abstract

The purpose of this study was to evaluate the usefulness of 22-oxacalcitriol (OCT) in the treatment of estrogen receptor (ER)-negative breast cancer. The antitumor effect of this agent and its effect combined with doxifluridine (5'-DFUR) on MDA-MB-231 tumors in female athymic mice were investigated. We also examined the effect of OCT on the expression of vascular endothelial growth factor (VEGF) which had been reported to generate angiogenesis in tumors. OCT significantly suppressed the growth of tumors without inducing hypercalcemia in a dose dependent manner. The effect of OCT combined with 5'-DFUR did not exceed the effect of a single agent therapy. The expressions of VEGF analyzed by enzyme-linked immunosorbent assay were significantly decreased in the OCT-treated group. These results suggest that OCT may partially suppress tumor growth by inhibiting neovascularization and it would likely have positive application as a treatment of ER-negative breast cancer.