Objectives: 1,25-Dihydroxyvitamin D can inhibit the proliferation of prostate cancer cells, but its clinical use is limited by hypercalcemia. We examined the effects of a "noncalcemic" vitamin D analogue, 1,25-Dihydroxy-16-ene-23-yne-cholecalciferol (16-23-D3), on the proliferation of human prostate cancer cells in a mouse model.
Methods: Twenty-four athymic nude mice were inoculated with human prostate carcinoma cells from the PC-3 cell line. Twelve mice (experimental group) received injections of 1.6 micrograms of 16-23-D3 on alternate days over a 22-day period. Twelve mice (control group) received sham injections. Tumor volumes, pathologic findings, and terminal serum calcium levels were compared between groups.
Results: The relative increase in tumor volume was significantly lower in the experimental than in the control group in the first interval following treatment (P < 0.01). Mean tumor volumes in the experimental group were approximately 15% smaller than in the control group. Serum calcium levels did not differ between groups.
Conclusions: 16-23-D3 showed modest antiproliferative effects on prostate cancer cells in this model without evidence of drug-induced hypercalcemia. These findings support the concept that vitamin D analogues can inhibit the proliferation of human prostate cancer cells in vivo.