[Effects of miR-449a on proliferation and migration of human breast cancer cell line MCF-7].

OBJECTIVE: To study the effects of knockdown of miR-449a on the proliferation and migration of human breast cancer cell line Michigan Cancer Foundation-7 (MCF-7). METHODS: Using miRNA chip screening of the differential expressions of miRNA in human breast cancer cell MCF-7 and normal breast cells MCF-10A. The inhibitor of miR-449a was synthesized by chemical and detected by real-time PCR after transfection aimed to verify the expression. Cell Counting Kit-8 (CCK-8) assay was used to detect the ability of cell proliferation after transfection with miR-449a inhibitor. Scratch assay was used to detect cell migration of MCF-7, and cell invasion ability was showed by transwell assay; The MCF-7 cell proliferation and migration related proteins, ß-catenin and E-cadherin, were detected by Western blot. The potential target gene of miR-449a was predicted by bioinformatics software, and Notch homolog 1 (Notch 1) was proved to be the target gene of miR-449a by luciferase assay. RESULTS: MCF-7 and MCF-10a cells were collected separately, and miRNA chip results showed that the level of miR-449a in MCF-7 cells was significantly higher than that of MCF-10A. In this study, the cells were divided into mock group, negative control group (NC group) and treatment group, the MCF-7 cells were collected before and after treatment and CCK-8 results showed that knockdown of miR-449a decreased MCF-7 cell proliferation ability significantly. Scratch assay results showed that downregulated miR-449a was related to the decreased metastasis of MCF-7 cells. Transwell results showed that knockdown of miR-449a inhibited the invasion of MCF-7 cells. Western blot showed the expression of ß-catenin was decreased and the expression of E-cadherin was increased after knockdown of miR-449a. Luciferase assay showed that miR-449a could significantly decrease the luciferase activity of Notch homolog 1-untranslated region (Notch 1-3'-UTR) plasmid (P<0.01). CONCLUSIONS: Inhibition of miR-449a in breast cancer cell line MCF-7 can significantly inhibit the proliferation and migration of cancer cells, which may be achieved by decreasing the expression of Notch 1 protein.

Activation of BK(Ca) channels in zoledronic acid-induced apoptosis of MDA-MB-231 breast cancer cells.

BACKGROUND: Zoledronic acid, one of the most potent nitrogen-containing biphosphonates, has been demonstrated to have direct anti-tumor and anti-metastatic properties in breast cancer in vitro and in vivo. In particular, tumor-cell apoptosis has been recognized to play an important role in the treatment of metastatic breast cancer with zoledronic acid. However, the precise mechanisms remain less clear. In the present study, we investigated the specific role of large conductance Ca(2+)-activated potassium (BK(Ca)) channel in zoledronic acid-induced apoptosis of estrogen receptor (ER)-negative MDA-MB-231 breast cancer cells. METHODOLOGY/PRINCIPAL FINDINGS: The action of zoledronic acid on BK(Ca) channel was investigated by whole-cell and cell-attached patch clamp techniques. Cell apoptosis was assessed with immunocytochemistry, analysis of fragmented DNA by agarose gel electrophoresis, and flow cytometry assays. Cell proliferation was investigated by MTT test and immunocytochemistry. In addition, such findings were further confirmed with human embryonic kidney 293 (HEK293) cells which were transfected with functional BK(Ca) α-subunit (hSloα). Our results clearly indicated that zoledronic acid directly increased the activities of BK(Ca) channels, and then activation of BK(Ca) channel by zoledronic acid contributed to induce apoptosis in MDA-MB-231 cells. The possible mechanisms were associated with the elevated level of intracellular Ca(2+) and a concomitant depolarization of mitochondrial membrane potential (Δψm) in MDA-MB-231 cells. CONCLUSIONS: Activation of BK(Ca) channel was here shown to be a novel molecular pathway involved in zoledronic acid-induced apoptosis of MDA-MB-231 cells in vitro.