To investigate the inhibitory effect of bicalutamide (BIC) combined with paclitaxel (PTX) on the proliferation of androgen receptor (AR) -positive triple negative breast cancer MDA-MB-231 cells and its possible mechanism.

The CCK-8 kit was used to determine the effect of BIC (0.1, 1.0, 10.0 μmol/L) and PTX at different concentrations (0.1, 1.0, 10.0, 100.0, 1000.0, 10 000.0 nmol/L)in monotherapy or in sequential combination of both on the proliferation of MDA-MB-231 cells. Inhibition rate was compared using one-way analysis of variance. The pairwise comparison was performed using the LSD method. MDA-MB-231 cells were treated with 10 nmol/L PTX and 10 nmol/L DMSO respectively for 72 h. Three cell samples were taken in each group to analyze the relevant gene expression profiling in array using a bioinformatic method. The adjusted t test was used to screen out differential genes.

After MDA-MB-231 cells were treated with different concentrations of BIC for 24, 48 and 72 h, respectively, the inhibition rates of MDA-MB-231 cells were statistically different at different time points (F=4.124, 8.189, 4.139, P=0.037, 0.004, 0.032). The inhibition rate of MDA-MB-231 cells reached the highest [(12.9 ± 5.5)%] at 48 h after the treatment of 10.0 μmol/L BIC. The inhibition rates of MDA-MB-231 cells were significantly different at different time points (F=8.407, 47.432, 14.907, P<0.001) after the treatment of PTX at different concentrations. The half inhibitory concentration (IC₅₀) of PTX in MDA-MB-231 cells at 48 h was 5 380.0 nmol/L. After 48 h treatment of 5 000.0 nmol/L PTX alone or combined with 0.1, 1.0, 10.0 μmol/L BIC, the inhibition rate of MDA-MB-231 cells was (53.2 ± 2.7)%, (53.2 ± 3.1)%, (51.7 ± 3.4)%, (51.0 ± 2.3)% in PTX monotherapy group and three experimental groups, respectively, indicating no significant difference (F=0.831, P=0.492). MDA-MB-231 cells were treated with sequential combination of 5 000.0 nmol/L PTX and 10.0 μmol/L BIC (PTX 24 h+ BIC 24 h group, BIC 24 h+ PTX 24 h group, PTX 48 h+ BIC 24 h group, BIC 48h+ PTX 24 h group), the monotherapy with 5 000.0 nmol/L PTX (PTX 48 h group) or 10.0 μmo/L BIC (BIC 48 h group) and the synchronous combined therapy of PTX and BIC(PTX 48 h+ BIC 48 h group), respectively. The result showed that there was a statistically significant difference in inhibition rate (F=241.466, P<0.001). The result of pairwise comparison showed that the inhibition rate in PTX 24 h + BIC 24 h group was (72.9 ± 1.9)%, significantly higher than (42.9 ± 1.7)% in BIC 24 h + PTX 24 h group (P<0.001), (60.9 ± 3.7)% in PTX 48 h group(P<0.001) and (60.3 ± 4.1)% in PTX 48 h + BIC 48 h group (P<0.001). There was a significant difference in the expression of seven genes (EGR1, FST, FOS, IL8, IL6, RPL27A and CA2) between PTX-treated group and DMSO-treated group (t=18.647, 10.336, 10.098, 9.683, 9.408, 9.050, 8.001, all P<0.050)

Sequential administration of PTX and BIC can inhibit the proliferation of AR-positive triple negative breast cancer MDA-MB-231 cells more effectively compared with the monotherapy and other combination methods. The two drugs may have the synergistic effect.