Zoledronic acid exhibits inhibitory effects on osteoblastic and osteolytic metastases of prostate cancer.

PURPOSE In this study we have examined the effects of zoledronic acid (ZA), a new-generation bisphosphonate, on prostate cancer (CaP) cells in vitro, and on both osteoblastic and osteolytic CaP metastases in animal models. EXPERIMENTAL DESIGN In vitro, CaP cells were treated with ZA, and the effects on proliferation, cell cycle, and apoptosis were determined. In vivo, PC-3, and LuCaP 23.1 s.c. and tibial tumors were treated with ZA. Effects on bone and tumor were determined by histomorphometry and immunohistochemistry. RESULTS ZA decreased proliferation of CaP cells, and caused G(1) arrest and apoptosis of CaP cells in vitro. In vivo, s.c. CaP tumor growth was not affected by ZA. However, growth of osteoblastic and osteolytic metastases of CaP was inhibited significantly in vivo. Matrix metalloproteinase-2, matrix metalloproteinase-9, and Cathepsin K levels were decreased in osteolytic bone metastases after ZA administration. CONCLUSIONS In conclusion, we have shown that ZA has significant antitumor effects on CaP cells in vitro and in vivo. Antiosteolytic activity and the antitumor effects of this compound could benefit CaP patients with bone metastases.