Study On Expression,Function And Mechanism Of ALDH1 And ABCG2 In Triple-negative Breast Cancer

Objective: To determine the expression of aldehyde dehydrogenase 1(ALDH1)and ATP binding cassette superfamily G member 2(ABCG2)in patients with triple-negative breast cancer,and to understand the the mechanism of ALDH1 and ABCG2 in tumor drug resistance for triple-negative breast cancer.Methods: A total of 56 patients who received triple-negative breast cancer resection and axillary lymph node dissection at our hospital between August 2013 and June 2016 were included in the present study.Primary focus tissues,tumor-adjacent tissues and lymph node tissues of the patients were collected.Tumor-adjacent tissues were used as control group.Quantitative real-time polymerase chain reaction was used to determine the expression of m RNA,while Western blotting was carried out to measure protein expression.Immunohistochemistry was performed to detect the expression of ALDH1 and BCRP and whether there is a correlation between and explore their relationship with clinical pathological features and their expression.MDA-MB-231 cells were transfected with small-interfering RNA to inhibit the expression of ALDH1 and ABCG2.MTT assay,colony formation assay and flow cytometry were employed to determine the proliferation and apoptosis of MDA-MB-231 cells.Cell migration and invasion were examined using a transwell chamber assay pre and post small-interfering RNA transfection.Xenograft modles of the female nude mice were used,which were randomly divided into two groups(MDA-MB-231 group and small-interfering RNA group).The mice were euthanized and the tumors were weighted for effectiveness assesment.Levels of reactive oxygen species and epithelial-mesenchymal transition relating proteins were detected to explore the mechanism of improving the chemotherapy sensitivity for Epirubicin.Results: Expression of ALDH1 and ABCG2 m RNA and protein was elevated in triple negative breast cancer tissues and metastatic lymph node.There was significant correlationbetween the expression of ALDH1 and the tumor grade,lymphanode staging and pathologica grade,p=0.044,0.009 and 0.030.The expression of ABCG2 protein in breast cancer was significant higher for patients with axis lymphanode metastactisis and pathologica grade,p=0.005 and 0.005.No significant correlation was found between the expression of ALDH1 and ABCG2,p=0.890.The expression of ALDH1 with Transfection with the siRNA of ALDH1 and ABCG2 reduced the expression of ALDH1 and ABCG2,respectively.According to MTT results at24 h,48h and 72 h after transfection,down-regulation of ALDH1 and ABCG2 expression decreased the proliferation of MDA-MB-231 cells.MDA-MB-231 colony formation was obviously inhibited by transfection of both ALDH1 and ABCG2 siRNA,which was more significantly inhibited when combinded with Epirubicin.The apoptosis of MDA-MB-231 cells were significantly increased by the combinations of ALDH1/ABCG2 siRNA transfection and Epirubicin.Both the employment of siRNA transfection and Epirubicin resulted in the increasment of ROS level in MDA-MB-231 cells,moreover which was significantly elevated by the combinations of ALDH1 siRNA transfection and Epirubicin.Meanwhile,compared to MDA-MB-231 cells,the significant up-regulation of E-cad protein and down-ragulation of Vimentin protein was observed in the ABCG2 siRNA group.Conclusion: ALDH1 and ABCG2 may be two independent factors,which participating breast cancer drug resistance in the chemotherapy and tumor invasion and metastasis,wherease no significant relationship was found between them.By ALDH1 or ABCG2 suppression,MDA-MB-231 cell proliferation and migration/invasion were inhibited,while cell apoptosis and chemotherapy sensitivity for Epirubicin were enhanced.Two different mechanisms might be concluded,which was owing to the up-ragulation of ROS with regard to ALDH1 and which was the suppression of EMT progress with regard to ABCG2.