OBJECTIVETo observe the synergistic effect of beta-elemene Injection (betaI) combined Paclitaxel Injection (PI) on breast cancer MB-468 cells and to study possible mechanisms.

METHODSBreast cancer MB-468 cells were treated with betaI (2.5, 5.0, 10.0, 20.0, 40.0, 80.0, 160.0, 320.0, and 640.0 microg/mL), PI (0.00100, 0.00200, 0.00400, 0.00800, 0.01600, 0.03125, 0.06250, 0.12500, and 0.25000 microg/mL), and betaI combined PI for 24 h and 48 h respectively. Cell proliferation was determined using SRB assay. Cell apoptosis and cell cycle phase distribution were detected using flow cytometry. The post-intervention expressions of cell cycle proteins [cyclin-dependent kinase (CDK1), cyclin-B1, P21(cip1), and P27(kip1)] were detected by Western blot.

RESULTSBeta-elemene or paclitaxel inhibited the growth of MB-468 cell line. The IC50 and IC20 values treated with beta-elemene for 24 h were 34.20 and 52.59 microg/mL and for 48 h were 10.15 and 17.81 microg/mL respectively, while the IC50 values treated with paclitaxel for 24 h and 48 h were 2.449 and 1.698 microg/mL respectively. Beta-elemene (20 and 40 microg/mL respectively) and Paclitaxel (0.016 and 0.008 microg/mL respectively) synergistically inhibited cell proliferation of MB-468 cells, with Q value > 1.15. Beta-elemene alone (52.59 microg/mL) apparently decreased the expression of cyclin-B1 protein. The expression of cyclin-B1 protein in the combined group was also lower than that in the PI group (1.698 microg/mL). The expression of P27(kip1) was up-regulated when compared with that in the betaI group or the PI group.

CONCLUSIONBeta-elemene had synergistic effect with Paclitaxel, and its possible mechanism might be correlated with down-regulating the cell cycle protein cyclin-B1 expression and up-regulating the P27(kip1) expression.