Expression of ABCG2 and p-glycoprotein in residual breast cancer tissue after chemotherapy and their correlation with epithelial-mesenchymal transition

Abstract

To explore the expression of breast cancer resistance protein (ABCG2), p-glycoprotein (P-gp) in residual breast cancer tissue after chemotherapy and their correlation with epithelial mesenchymal transition (EMT). Seventy-six cases of breast cancer were collected. The expression of ABCG2, P-gp and EMT markers E-cadherin and vimentin in residual breast cancer tissue after chemotherapy was detected by immunohistochemistry (EnVision method). MCF7 cells were divided into three group:untreated control group, positive control (TGF-β1 induced) group and drug surviving cells (DSC) group (selected viable MCF7 cells after docetaxel and epirubicin treatment). The expression of EMT markers E-cadherin and vimentin was detected by immunofluorescence. The mRNA and protein expression of ABCG2, P-gp and EMT markers were detected by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot, respectively. Compared with breast cancer tissue before chemotherapy, ABCG2, P-gp and vimentin protein were highly expressed in residual breast cancer tissue after chemotherapy. The expression of ABCG2 and P-gp correlated positively with vimentin protein (r1=0.97, P1=0.000; r2=0.83, P2=0.001) and negatively with E-cadherin protein (r3=-0.55, P3=0.010; r4=-0.43, P4=0.020) expression. RT-PCR results showed that ABCG2, P-gp and vimentin mRNA were highly expressed in residual breast cancer tissue after chemotherapy. The expression of ABCG2 and P-gp mRNA correlated positively with vimentin mRNA (r1=0.99, r2=0.96, P<0.05) but negatively with E-cadherin protein (r3=-0.99, r4=-0.98, P<0.05); Western blot showed that ABCG2, P-gp and vimentin protein were highly expressed in residual breast cancer tissue after chemotherapy. The expression of ABCG2 and P-gp protein correlated positively with vimentin protein (r1=0.98, r2=0.89, P<0.05) and negatively with E-cadherin protein (r3=-0.47, r4=-0.33, P<0.05). The expression of resistance-associated proteins in the residual breast cancer tissue after chemotherapy is significantly correlated with EMT. The expression of EMT profile may be one of important mechanisms for multidrug resistance in breast cancer.