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| Background：Chemotherapy, being as one of the three cornerstones in breast cancer treatment, is playing an important role in controlling the disease. However, growing evidences indicate that after several regimens, chemotherapy does not effectively alleviate disease for patients with advanced breast cancer. Different studies had indicated that the tumor cells underwent epithelial-mesenchymal transition (EMT). In recent years, there have been literature studies confirmed that miRNAs play a regulatory role in chemotherapy resistance and chemotherapy-induced EMT. However the underlying mechanisms is not clear. Methods：To address this question, we constructed drug-resistant breast cancer cell lines, and then observed if breast cancer resistant cell lines EMT displayed. Changes in cell morphology are observed under the microscope. We also detected the expressions of EMT markers E-cadherin, Vimentin, N-cadherin by qRT-PCR, western blotting, and the invasion and migration ability of tumor cells by modified chamber assay. Results：Compared with the parental cells, there were 16 miRNA expression increased and 20 downregulated miRNA in resistant cell lines, demonstrated by miRNA microarray. Of which miR-200b is the most obvious. Elavated miR-200b level in drug-resistant cells could reverse features of parental cells, and inhibit invasion and migration ability, but increase sensitivity to doxorubicin. Knockdown miR-200b in parental cells can promote transition to mesenchymal features, increase the invasion and migration ability, induce resistance to doxorubicin. Luciferase experiments showed that miR-200b target was FN1.Upregulated miR-200b inhibit FN1 expression and luciferase activity. Compared with the parental cell line, FN1 was significantly elevated in MCF-7/Adr. Knockdowning FN1 reverse mesenchyal features, decrease cell migration and invasion capacity, and improve drug sensitivity to doxorubicin. Conclusion: Our data suggest that FN1 is the target of mir-200b, which gets the regulation role of the chemotherapeutic resistance to doxorubicin in breast cancer cells. Therefore miR-200b may serve as an effective tumor inhibitor, play a role in the future to pave the way for targeted cancer therapy. |
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| Keywords:oncology; breast cancer; chemotherapy resistance; EMT; mir-200b; FN1????? |
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