Abstract: ObjectiveTo investigate the expression and clinical significance of microRNA210 (miR210) in breast cancer tissues, and to investigate its effect on the proliferation and metastasis of human triple negative breast cancer cell line MDAMB231 in vitro. MethodsThe breast cancer tissues and paracancerous tissues in 82 patients were collected in the Department of Pathology of Hunan Cancer Hospital  from December 2013 to September 2015. Quantitative realtime polymerase chain reaction (qRTPCR) technique was used to detect the expression level of miR210 in tissues and cells. The relationship between the expression of miR210 and clinical data and prognosis of patients were analyzed. The triple negative breast cancer cell line MDAMB231 transfected with fulllength miR210 plasmid was regarded as test group, and the cell transfected with blank vector was regarded as control group. CCK8 assay was used to detect the proliferation ability of cells in both groups. Transwell invasion and migration assays were used to detect the metastasis and invasion ability of  cells. ResultsThe results of qRTPCR showed that the expression level of miR210 was 0.198±0.014 in breast cancer tissues, which was significantly higher than that in paracancerous tissues (0.084±0.009), and the difference was statistically significant (t=8.141, P＜0.001). The expression level of miR210 in triple negative breast cancer tissues was 0.254±0.026, which was significantly higher than that in nontriple negative breast cancer tissues (0.167±0.015), and the difference was statistically significant (t=3.175, P=0.003). There were significant differences in TNM staging and molecular typing between the patients with high and low expression of miR210 (χ2=7.859, P=0.005; χ2=7.053, P=0.008). The 4year survival rate of patients with high expression of miR210 was significantly lower than that of patients with low expression of miR210 (49.37% vs. 76.80%), and the difference was statistically significant (χ2=4.743, P=0.024). The results of qRTPCR showed that the expression of miR210 in cells in test group was 0.517±0.038, which was significantly higher than that in control group (0.284±0.022), and the difference was statistically significant (t=9.280, P＜0.001). The results of CCK8 assay showed that the proliferation abilities of the test group were significantly higher than those of the control group in 48, 72 and 96 h (3.771±0.452 vs. 3.206±0.314; 7.662±0.619 vs. 6.736±0.552; 15.477±1.425 vs. 11.592±1.243), and the differences were statistically significant (t=2.296, P=0.025; t=2.496, P=0.019; t=4.594, P=0.001). The results of Transwell invasion assay showed that the cell number of test group in inferior surface was 107.8±13.0, which was significantly higher than that of control group (74.4±10.9), and the difference was statistically significant (t=3.732, P=0.001). The results of Transwell migration assay showed that the cell number of test group in inferior surface was 136.5±18.5, which was significantly higher than that of control group (87.4±15.7), and the difference was statistically significant (t=4.256, P＜0.001). ConclusionThe expression of miR210 in breast cancer tissues is high, and its expression is closely related to progression, malignancy and prognosis of patients. In vitro, miR210 can promote the malignant behavior of triple negative breast cancer cell line MDAMB231. It is a potential molecular marker and targeted treatment site.

Key words: Breast neoplasms, Cell proliferation, Neoplasm invasiveness, Cell movement, MicroRNA210