To investigate the effect of Rocaglamide (Roc-A) on paclitaxel (PTX) resistance in breast cancer MCF-7/PTX cell line and its mechanism.

With breast cancer MCF-7 cells as the research object, PTX resistant MCF-7/PTX cell line was obtained by continuous induction with low concentration of PTX. Methyl thiazolyl tetrazolium (MTT) method was used to determine the drug resistance index of MCF-7/PTX cell line, the effect of Roc-A on the proliferation activity of MCF-7/PTX cell line and the drug resistance reversal multiple. MCF-7/PTX cell lines were divided into control group (normal cultured cells), PTX group (40.8 nmol·L^-1 PTX), PTX+Roc-A-L group (40.8 nmol·L^-1 PTX+25 nmol·L^-1 Roc-A), PTX+Roc-A-M group (40.8 nmol·L^-1 PTX+50 nmol·L^-1 Roc-A) and PTX+Roc-A-H group (40.8 nmol·L^-1 PTX+100 nmol·L^-1 Roc-A). The apoptosis level of each group was detected by flow cytometry; the relative expression levels of cell autophagy related protein LC3 were detected by immunofluorescence assay; Western blotting was used to detect the relative expression levels of cell apoptosis related proteins, such as B cell lymphoma-2 associated X protein (Bax) and autophagy associated protein autophagy microtubule associated protein light chains 3 (LC3).

The PTX resistant cell line MCF-7/PTX of breast cancer was successfully constructed with a drug resistance index of 5.49; Roc-A could inhibit the proliferation activity of MCF-7/PTX cell lines in a concentration dependent manner, while the reversal multiples of PTX resistance of MCF-7/PTX cell lines to Roc-A at different concentrations (25, 50, 100 nmol·L^-1) were 1.57, 2.68 and 6.16, respectively. The apoptosis rates of the control group, PTX group, PTX+Roc-A-L group, PTX+Roc-A-M group and PTX+Roc-A-H group were (4.75±2.10)%, (21.79±3.61)%, (32.54±3.43)%, (39.82±3.26)% and (55.61±4.22)%, respectively; the relative expression levels of LC3 fluorescence were 1.00±0.08, 0.77±0.06, 0.60±0.06, 0.41±0.04 and 0.26±0.03, respectively; the relative expression levels of Bax protein were 0.12±0.04, 0.25±0.09, 0.48±0.10, 0.86±0.12 and 1.10±0.13, respectively; the LC3Ⅱ/LC3Ⅰ protein ratio were 6.52±0.27, 3.75±0.23, 1.76±0.17, 1.31±0.10 and 1.02±0.06, respectively. Compared with the control group, the PTX group, PTX+Roc-A-L group, PTX+Roc-A-M group, PTX+Roc-A-H group showed statistically significant differences in the above indicators (all P<0.05); the above indicators in the PTX+Roc-A-L group, PTX+Roc-A-M group and PTX+Roc-A-H group were compared with those in the PTX group, and the differences were statistically significant (all P<0.05), showing a dose-dependent relationship.

Roc-A can reverse the resistance of breast cancer drug resistant cell line MCF-7/PTX to PTX, and the mechanism may be related to the reduction of autophagy.