上皮细胞黏附分子增强细胞间紧密连接促进乳腺癌细胞耐药

Epithelial Cell Adhesion Molecules(EpCAMs)Promote Drug Resistance in Breast Cancer Cells by Enhancing Tight Junctions

乳腺癌是致死率很高的恶性肿瘤,由ABCG2(ATP-binding cassette G2)介导的多药耐药(multidrug resistance,MDR)是导致其化疗失败的重要原因,探讨ABCG2介导的耐药机制并探寻其关键分子是当前亟待解决的难题。上皮细胞黏附分子(epithelial cell adhesion molecule,EpCAM)参与多种肿瘤耐药,且与乳腺癌MDR密切相关,但它在ABCG2介导的乳腺癌耐药中的作用尚未阐明。本研究目的在于探究EpCAM对于ABCG2介导的乳腺癌细胞的多药耐药的调节作用及其机制。CCK8细胞毒性结果证实,相对于人乳腺癌药物敏感株MCF-7,耐药株MCF-7/MX对米托蒽醌(mitoxantrone,MX)的耐药性显著增强;Western印迹结果显示,与MCF-7相比,MCF-7/MX细胞中ABCG2高表达,EpCAM表达上调。siRNA法敲低MCF-7/MX细胞中EpCAM可下调其ABCG2表达,并恢复对MX的敏感性。倒置显微镜观察细胞形态,发现敲低EpCAM可减少MCF-7/MX细胞间连接。免疫荧光双染法观察到EpCAM与密封蛋白1(claudin 1)在MCF-7/MX细胞共定位;进一步Western印迹结果表明,敲低EpCAM减少MCF-7/MX细胞中密封蛋白1表达。综上所述,EpCAM可能通过与密封蛋白1相互作用,增强细胞间紧密连接,促进ABCG2介导的乳腺癌多药耐药。

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.