摘 要 目的：探讨乳腺癌细胞中上皮间质转化（epithelial-mesenchymal transition, EMT）与P-糖蛋白（P-glucoprotein, P-gp）介导的多药耐药（multidrug resistance, MDR）的关系及其可能的机制。方法：将携Snail基因的真核表达载体pcDNA-Snail转染人乳腺癌细胞MCF-7，用多柔比星（doxorubicin, DOX）诱导各组细胞耐药。免疫细胞荧光检测上皮标志物E-钙黏素（E-cadherin）、间质标志物波形蛋白（vimentin）以及P-gp的表达,MTT检测耐药细胞的增殖,RT-PCR检测Snail、MDR1、p38-MAPK mRNA的表达。结果：细胞免疫荧光显示,转染pcDNA-Snail载体后,MCF-7细胞发生EMT,E-cadherin表达显著降低，vimentin表达显著升高；P-gp在发生EMT的MCF-7细胞中表达显著升高。经DOX诱导，MCF-7/Snail细胞的耐药能力较MCF-7/DOX细胞显著增强（P<0.05）。RT-PCR显示，MCF-7细胞发生EMT后,p38-MAPK表达显著升高（P<0.05），MDR1表达较亲本细胞明显升高（P<0.01）。结论：MCF-7细胞发生EMT后，可能通过p38-MAPK引发P-gp介导的MDR。

Abstract Objective:To investigate the relationship between epithelial-mesenchymal transition (EMT) and P-glucoprotein (P-gp)-induced multidrug resistance (MDR) in breast cancer cells and the corresponding mechanisms. Methods: Eukaryotic expression vector pcDNA-Snail was constructed and then transfected into human breast cancer cell line MCF-7. Multidrug resistance was induced by doxorubicin (DOX) in different groups. Expressions of epithelial marker E-cadherin, interstitial marker vimentin, and P-glucoprotein (P-gp) were detected by immunofluorescence. MTT assay was used to measure the proliferation of drug resistant MCF-7 cells. Expressions of Snail, MDR1, and p38-MAPK mRNA were evaluated by RT-PCR. Results: Immunofluorescence showed that MCF-7 cells had EMT after transfection with pcDNA-Snail vector. The expression of E-cadherin was downregulated, and expressions of vimentin and P-gp were upregulated in EMT-like MCF-7 cells. Drug resistance of MCF-7/Snail cells was significantly enhanced compared with MCF-7 cells after induction by DOX (P<0.05). The expressions of MDR1 and p38-MAPK mRNA in EMT-like cells were also significantly increased compared with those in parental MCF-7 cells (P<0.05). Conclusion: EMT may trigger DOX-induced and P-gp-mediated MDR via p38-MAPK in MCF-7 cells.

山东省自然科学基金资助项目（No.Y2008C75）