An in vitro investigation of the antineoplastic effects of tamoksifen and zoledronic acid combination in breast cancer cell lines

Bisphosphonates are well established in the management of breast-cancer induced bone disease. Recent studies have suggested that these compounds are effective in preventing the development of bone metastases. In this study using substance 1, 10, 100 ?M/L concentration of zoledronic acid, 10, 100 nM/L concentration of tamoxifen and zoledronic tamoxifen combinations groups were established out of MCF-7 cell line to be examined at 24th, 48th and 72nd hours. The effects of zoledronic acid, tamoxifen and combinations were determined by assessing cell number using a inverted microscopy.Zoledronic acid was not sufficient to cause a significant reduction in cell number in 24 hours. At 10 ?M/L concentration of zoledronic acid decrease in cell number 13 % and 25 % of cells after 48 and 72 hours of incubation respectively whereas these rates were 16 % and 52 % at 100 ?M/L concentration of zoledronic acid respectively. The cytotoxic effect of zoledronic acid increases with dose and incubation time. Combination with 100 ?M/L concentration of zoledronic acid and 100 nM/L concentrations of tamoxifen decrease in cell number 28 % and 63 % after 48 and 72 hours of incubation respectively (p=0.0000007).These data suggest that zoledronic acid has a direct anti-tumour activity on breast cancer cells in vitro and potentiates the anti-tumour effects of commonly used antineoplastic agent tamoxifen.