| Background and Objective: mi R-134 exhibits aberrantly low expression in various human malignancies, including breast cancer, on the other way at extremely high levels in some other human malignancies. Previous studies reported that mi R-134 was capable of downregulating multidrug resistance associated protein 1 MRP1/ABCC1 to confer Adriamycin-sensitivity in non-small cell lung cancer cells. However, limited attention has been directed towards the expression and contribution of mi R-134 and ABCC1 to adriamycin-resistance of breast cancer cells. This study aimed to explore the expression and the relationship of mi R-134 and ABCC1, as well as evaluate the potential effects of mi R-134 on the proliferation and apoptosis in adriamycin-resistant breast cancer cells.Methods: 1. q RT-PCR was employed to detect the expression of mi R-134 in nomal breast cancer tissue(ASBC), para-carcinoma tissue(ASPT), Adriamycin resistant breast cancer tissue(ARBC) and respective para-carcinoma tissue(ARPT), as well as in MCF-7 cells and Adriamycin resistant MCF-7/ADR cells. 2. q RT-PCR and western blot were performed to evaluate the expression of ABCC1 in ASBC, ASPT, ARBC and ARPT tissues, as well as in MCF-7 cells and Adriamycin resistant MCF-7/ADR cells. 3. The mi R-134 mimics and mi R-134 NC were transfected into MCF-7/ADR cells respectively, and the overexpression of mi R-134 was verified by q RT-PCR. Then the expression of ABCC1 at both m RNA and protein levels were analyzed by q RT-PCR, immunohistochemical and western blot. 4. MTT assay was used to examine the IC50 values and the proliferation of mi R-134-overpressed MCF-7/ADR cells upon IC50 Adriamycin treatment. 5. TUNEL staining and flow cytometry were carried out to address the apoptosis of mi R-134-overpressed MCF-7/ADR cells upon IC50 Adriamycin treatment.Results: 1. The expression of mi R-134 in breast cancer tissues was decreased significantly compared with respective para-carcinoma tissues(p<0.001). Moreover, the expression of mi R-134 m RNA in ARBC tissues was much lower than in ASBC tissues(p<0.001). Similarly, the expression of mi R-134 in MCF-7/ADR cells was declined notably compared with in MCF-7 cells(p<0.01). 2. The expression of ABCC1 at both m RNA and protein levels in breast cancer tissues were increased significantly compared with those in respective para-carcinoma tissues(p<0.001). Moreover, the m RNA and protein levels of ABCC1 in ARBC tissues were much higher than those in ASBC tissues(p<0.05). Similarly, the expression of ABCC1 in MCF-7/ADR cells was elevated notably in comparison with in MCF-7 cells(p<0.001). 3. The expression of mi R-134 m RNA in MCF-7/ADR cells transfected with mi R-134 mimics was much higher than those in control cells transfected with mi R-134 NC(p<0.001). The expression of the m RNA for ABCC1 in mi R-134 overexpressed MCF-7/ADR cells was basically unchanged, along with sharply reduced protein levels compared with control(p<0.001). 4. The IC50 of mi R-134-overpressed MCF-7/ADR cells was 226ng/ml. Overexpression of mi R-134 remarkably suppressed the proliferation of Adriamycin treated MCF-7/ADR cells. The growth inhibitory effect was prominent at the point of 48 h(p<0.05), and a more elevated trend at 72 h and 96 h(p<0.01). 5. Overexpression of mi R-134 significantly enhanced the apoptosis of Adriamycin treated MCF-7/ADR cells(p<0.01).Conclusions: 1. The expression of mi R-134 was downregulated in breast cancer tissues, and exhibited lowest expression in Adriamycin resistant breast cancer tissues and cells. 2. The expression of ABCC1 was upregulated in breast cancer tissues, and exhibited highest levels in Adriamycin resistant breast cancer tissues and cells. 3. mi R-134 could downregulate the expression of ABCC1. 4. Overexpression of mi R-134 promoted the anti-proliferative and pro-apoptotic effects of Adriamycin in MCF-7/ADR cells, confer Adriamycin-sensitivity in MCF-7/ADR cells by decreasing the expression of ABCC1. |
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