Abstract: Objective To evaluate the effect of docetaxel (DTX) combined with a heptapeptide (LPLTPLP, namely P7) on the human triple-negative breast cancer cell MDA-MB-231 in vitro. Methods The cell viability was measured by SRB assay followed by evaluation of their combination effect using the isobologram. Flow cytometry was performed to quantify apoptotic cells following treatment of DTX, P7 and DTX combined with P7 and the expression of the apoptosis-related proteins were determined by western blot analysis. Results P7 has been shown to synergize with DTX in cell viability detection. The apoptotic rate was highly increased with increasing Bax/Bcl-2 ratio after MDA-MB-231 cells were exposed to DTX and P7 combination. Conclusion Combination of P7 and DTX exhibits synergistic effects on MDA-MB-231 cells as characterized by increasing apoptosis activation, in which the expression of pro-apoptotic protein Bax increased with a decline in apoptotic protein Bcl-2.

Key words: Triple-negative breast cancer, Apoptosis, Docetaxel, Heptapeptide, Synergy