Zoledronic acid inhibits gastric cancer cells by induction of apoptosis

3806 BACKGROUND AND AIM: Zoledronic acid, the 3rd generation bisphosphonate, is clinically available for skeletal complications, such as cancer-induced osteolysis and osteoporosis. Additionally, it has been reported to exert strong anti-cancer activities, against breast cancer, prostate cancer, leukemia, among others. Here, we aimed to investigate the anti-tumor effect of Zoledronic acid on gastric cancer, which is one of the most popular diseases in East Asia, and especially in Japan. METHODS: The gastric adenocarcinoma cell lines, namely MKN-45, and MKN74, were used. Zoledronic acid was kindly gifted by Novartis pharma, and tested at various concentrations (5, 10, 25, 50 and 100 μmol/L). The proliferative activity of gastric cancer cells was assessed by the MTS assay. The annexin V / PI staining was used to analyze the induction of apoptosis. In addition, to clarify the mechanisms of the apoptosis induction, the activation of caspases-8, -9 and -3 was evaluated by flow-cytometry. And Western blotting was performed to analyze the expression of apoptosis-associated proteins. RESULTS: Zoledronic acid treatment for 24-72h resulted in a dose- and time-dependent inhibition of the proliferative activity of both gastric cancer cell lines tested. This inhibitory effect was dependent on induction of apoptosis, as confirmed by the annexin V / PI staining. Both the caspase-8 and -9 cascades were activated in the apoptotic cells. However, the expression of the apoptosis-associated proteins investigated, namely Bcl-2, Bcl-xL, and Bax, were not changed. The Ras protein expression, analyzed by Western blot, was not changed in the whole cell lysates. CONCLUSION: Zoledronic acid caused a dose- and time-dependent inhibition of the proliferative activity of gastric cancer cells, by induction of cell apoptosis. The probable mechanism of apoptosis induction is the inhibition of Ras protein plenylation, as demonstrated by the change of Ras protein distribution from the cytosol to the membrane fraction. It should be considered a promising anti-gastric cancer agent, and since it is already available for clinical use, clinical trials should be started to confirm its properties in human beings.