Effects of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) and its analogues (EB1089 and analog V) on canine adenocarcinoma (CAC-8) in nude mice.

摘要

The aim of this study is to determine the effects of 1,25(OH)2D3 and its analogues on tumor growth and body weight, changes in plasma ionized calcium, parathyroid hormone-related protein (PTHrP) production, bone resorption, and the distribution of the 1,25(OH)2D3 receptor (VDR) on tumors in nude mice-bearing the canine adenocarcinoma (CAC-8). Thirty-seven nude mice were implanted subcutaneously with CAC-8. Two weeks after implantation, the mice were divided into 5 groups and injected intraperitoneally 3 times/week for 4 weeks with 5 different substrates. Group I (nontumor-bearing mice) were injected with vehicle. Groups II through V were CAC-8-bearing mice injected with the following: Grp. II, vehicle; Grp. III, analog V; Grp. IV, 1,25(OH)2D3; and Grp. V, EB1089. Our results showed that mice body weight (% change) of CAC-8-bearing mice was significantly lower than those of nontumor-bearing mice (p<0.05). CAC-8-bearing mice treated with analog V maintained their body weight better than CAC-8-bearing mice treated with either vehicle, 1,25(OH)2D3, or EB1089. A reduction of tumor growth was observed in CAC-8-bearing mice treated with 1,25(OH)2D3 and its analogues; however, the reduction was not statistically significant compared to the vehicle-treated CAC-8-bearing mice. All CAC-8-bearing mice increased osteoclastic bone resorption and hypercalcemia. Immunohistochemical staining of CAC-8 with VDR antibody demonstrated a positive reaction in nuclei of tumor cells. In conclusion, CAC-8-bearing mice treated with analog V were more active and maintained their body weight better than other CAC-8-bearing groups. Analog V-treated mice also showed no toxic side effects of hypercalcemia despite an increase in plasmaionized calcium comparable to nontumor-bearing mice. Tumor volumes of CAC-8-bearing mice treated with 1,25(OH)2D3 and its analogues were smaller than vehicle-treated CAC-8-bearing mice. This finding suggested an inhibitory effect on tumor cell growth.