MicroRNA-574 enhances doxorubicin resistance through down-regulating SMAD4 in breast cancer cells.

OBJECTIVE: Drug resistance has become an important factor that threatens the survival and prognosis of patients with breast cancer, especially in patients with advanced breast cancer. Several microRNAs have been proved to participate in the resistant process; however, the role of miR-574 in doxorubicin (Dox) resistant breast cancer is still unclear. PATIENTS AND METHODS: Quantitative Real-time poly chain reaction (qRT-PCR) was employed to detect the expression level of miR-574 in breast cancer Dox-resistant MCF-7/Adr cell line and parental MCF-7 cell line. Using miR-574 mimics and inhibitors, miR-574 level was up- or down- regulated. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay was handled to detect the IC50, and flow cytometric analysis was employed to measure the apoptosis and cell circle. Dual-luciferase and Western-blot experiments were applied to verify the direct target gene of miR-574. RESULTS: miR-574 expression level was significantly higher in MCF-7/Adr cells compared to normal MCF-7 cells. Up-regulation of miR-574 level in MCF-7 cells promoted the cell growth and G0/G1-to-S phase transition but inhibited cell apoptosis. However, knockdown of miR-574 in MCF-7/Adr cells decreased the IC50 and cell growth. Using luciferase assay, SMAD4 was confirmed to be a potential target of miR-574, and the expression of SMAD4 protein was regulated by miR-574. In blood samples of patients, the miR-574 level before chemotherapy was higher than that after chemotherapy. CONCLUSIONS: We revealed miR-574 could promote doxorubicin resistance of breast cancer MCF-7 cells via down-regulating SMAD4, thus providing a novel target for advancing breast cancer chemotherapy.

Effect of lutein and doxorubicin combinatorial therapy on S180 cell proliferation and tumor growth.

OBJECTIVE: Multidrug resistance and toxicity significantly compromise the therapeutic efficacy for sarcomas. We aimed at evaluating the effect of lutein-doxorubicin (DOX) combinatorial therapy on inhibiting S180 (Sarcoma 180) cell proliferation and tumor growth. MATERIALS AND METHODS: S180 cells in logarithmic growth phase were treated with lutein, DOX, or lutein-DOX combinatorial therapy for 48 h. The cell survival rate was determined by MTT assay. Apoptosis was detected by flow cytometry. The expression of PCNA, P53, and NF-κB was assessed by Western blot. Further, mice bearing S180 tumors received lutein, DOX, or lutein-DOX combinatorial therapy by oral gavage. RESULTS: Lutein-DOX combinatorial therapy significantly decreased the proliferation of S180 cells (p<0.01) in vitro. Also, the expression of proliferating cell nuclear antigen (PCNA) (p<0.05) and the apoptosis-relevant gene p53 were decreased, which resulted in increased cell apoptosis (p<0.05). The level of nuclear factor kappa B (NF-κB) was also decreased by the combinatorial therapy. Lutein-DOX combinatorial therapy reduced the cytotoxicity of DOX and reduced the inflammatory response. The inhibitory effect of lutein-DOX combinatorial therapy on cell proliferation was confirmed in vivo. The growth rate and size of the tumor at 30 d after treatment were significantly lower than those of the control group and DOX single therapy. CONCLUSIONS: Lutein and DOX synergistically inhibit sarcoma cell proliferation and tumor growth. This novel therapeutic regimen could potentially improve clinical outcome of sarcoma patients.