Epithelial Cell Adhesion Molecules (EpCAMs) Promote Drug Resistance in Breast Cancer Cells by Enhancing Tight Junctions / 中国生物化学与分子生物学报

Breast cancer is a malignant tumor with high mortality, and multidrug resistance (MDR) mediated by ABCG2 (ATP-Binding cassette G2) is an important cause of chemotherapy failure. It is an urgent problem to explore the mechanism of ABCG2-mediated drug resistance and its key molecules. Epithelial cell adhesion molecule (EpCAM) is involved in multiple tumor drug resistance and is closely related to breast cancer MDR. However, its role in ABCG2-mediated breast cancer drug resistance has not been clarified. The purpose of this study was to explore the regulation of EpCAM on ABCG2-mediated MDR in breast cancer cells and its mechanism. CCK8 cytotoxicity assays confirmed that the drug resistance of MCF-7/MX cell line to mitoxantrone (MX) was significantly increased compared with MCF-7 drug-sensitive strain of human breast cancer. Western blotting results showed that ABCG2 was highly expressed and EpCAM was up-regulated in MCF-7/MX cells compared with MCF-7. SiRNA knockdown of EpCAM in MCF-7/MX cells down-regulated ABCG2 expression and restored sensitivity to MX. Cell morphology was observed under an inverted microscope, and it was found that knocking down EpCAM reduced cell-cell connections between MCF-7/MX cells. The co-localization of EpCAM and claudin 1 in MCF-7/MX cells was observed by immunofluorescence. Furthermore, Western blotting results showed that EpCAM knockdown reduced claudin 1 expression in MCF-7/MX cells. In conclusion, EpCAM may promote ABCG2-mediated mMDR in breast cancers by enhancing intercellular tight junctions through interaction with claudin 1.

Downregulation of cytokeratin 18 increases NMIIA expression and promotes breast cancer metastasis / 中国药理学通报

Aim To investigate the role of aberrant cytokeratin 18(CK18) expression in breast cancer metastasis, anrl to elucidate the mechanism by identif¬ying its target.Methods The expression of CK.18 in human breast cancer tissues and cells was determined using immunohistochemical staining and Western blot, respectively.CK18 expression in human breast cancer MCF-7 cells was effectively down-regulated by shRNA, and its effect on breast cancer metastasis was further determined by scratch wound healing assay.The co-lo- cation of CK18 and non-muscle II A ( NMIIA) in MCF-7 cells was examined using double immunofluo¬rescence staining.The effect of CK18 down-regulation on the levels of NMIIA and c-Abl-ERK signaling was quantified by Western blot.Results Lower CK18 lev¬els was found in metastatic than that in primary breast cancer tissues and in highly invasive MDA-MB-231 than that in MCF-7 cells.CK.18 down-regulation pro¬moted the wound repair ability of MCF-7 cells 72h after scratch.CK18 and NMIIA were shown to co-locate in cytoplasm of MCF-7 cells.Moreover, down-regulation of CK18 increased NMIIA expression and activated the c-Abl-ERK signaling pathway in MCF-7 cells.Con¬clusions Down-regulation of CK18 could promote me¬tastasis of breast cancer, which is related to increased NMIIA expression and the activation of c-Abl-ERK sig¬naling pathway.