The improvement of doxorubicin activity on breast cancer cell lines by tangeretin through cell cycle modulation

Tangeretin, shows cytotoxic effect on COLO 205 colon cancer cells. Combination of tangeretin with tamoxifen showed synergistic effect and increased the cancer cell sensitivity towards tamoxifen on T47D cells. However, the combination of tangeretin with chemotherapeutic agent doxorubicin on breast cancer cells have not been explored yet. Therefore, the aim of this research is to examine the improvement of cytotoxic effect of doxorubicin by tangeretin through cell death induction and cell cycle modulation on MCF-7 and T47D cells. The cytotoxic effect of tangeretin, doxorubicin, and their combination on tested cells were carried out by using MTT assay. Cell cycle distribution was determined by flowcytometer FACS-Calibur and the flowcytometry data was analyzed using ModFit LT 3.0 program. Cell death assay were done by double staining method using ethydium bromide-acridin orange. Single treatment of tangeretin 5-100 mu M did not show cytotoxic effect on MCF-7 and T47D cells. The combination of tangeretin 50 and 100 mu M with doxorubicin 200 nM (MCF-7) and 7.5 nM (T47D) increased the cytotoxic effect of doxorubicin on both breast cancer cell lines. This improvement of cytotoxic effect is due to cell death induction and cell cycle modulation. Furthermore, single treatment of tangeretin showed cell death only on T47D cell and caused G1-phase arrest on MCF-7 cell and G2/M-phase arrest on T47D cell. While doxorubicin induced cell accumulation at G2/M phase in both cancer cell lines. However, combination of tangeretin and doxorubicin increased cell death on both cancer cell lines, compared with doxorubicin by itself. The combination also showed G1-phase arrest on MCF-7 cell and increased cell accumulation at G2/M phase on T47D cell. Based on this result, tangeretin is potential to be developed as co-chemotherapeutic agent for breast cancer by inducing apoptosis and cell cycle arrest. However, the molecular mechanism need to be explored further.