Alendronate inhibits intraperitoneal dissemination in in vivo ovarian cancer model

Ovarian cancer is characterized by diffuse peritoneal carcinomatosis and often by large volumes of ascites. We previously reported that alendronate, a nitrogen-containing bisphosphonate, inhibited ovarian cancer cell migration by attenuating the activation of Rho through inhibiting the mevalonate pathway. However, questions remain about the ability of alendronate to inhibit the invasiveness of cancer cells to the adherent tissues and the growth of disseminated ovarian cancer in vivo. We established an in vivo ovarian cancer model with i.p. carcinomatosis in athymic immunodeficient mice. In the prevention model, in which alendronate administration started from the day after tumor inoculation, alendronate prevented the stromal invasion, reduced the tumor burden, and inhibited ascites accumulation. Histologic observation revealed that alendronate treatment decreased the stromal invasion of the i.p. tumor while inhibiting the metalloproteinase-2 activity in ascites. This antitumor effect might result from the inhibition of cancer cell migration and proteolytic activity. In the treatment model, in which alendronate was given from 10 days after tumor inoculation when macroscopic tumors are already implanted in the peritoneum, the antitumor effect was weaker but still significant. Furthermore, alendronate administration decreased the serum CA-125 levels of mice bearing disseminated ovarian cancer compared with those of nontreated mice. The potent effects of alendronate in reducing stromal invasion, tumor burden, and ascites suggest that it will be of value in regimens for treatment of women with ovarian cancer.