Decreased microRNA-768-3p expression indicates a poor prognosis in patients with breast cancer and promotes breast cancer cell viability, migration and invasion

Breast cancer is the most common malignancy in women and microRNA-768-3p (miR-768-3p) is abnormally expressed in hepatocellular carcinoma, non-small cell lung carcinomas and melanoma. The aim of the present study was to evaluate the prognostic value and biological function of miR-768-3p in breast cancer. The expression of miR-768-3p in tumor tissues and adjacent tissues of 116 patients with breast cancer obtained by surgery and normal breast cell lines MCF-10A and breast cancer cell lines ( MCF-7, MDA-MB-231, T-47D and SK-BR-3) were detected by reverse transcription-quantitative PCR. The association between miR-768-3p expression and the clinicopathological characteristics of patients was analyzed using the chi(2) test. In addition, the Kaplan-Meier method was used for survival analysis. A Cox regression model was used to examine the effect of miR-768-3p on the prognosis of patients with breast cancer. Hemocytometer cell counting and Transwell assays were used to detect the effects of miR-768-3p on the characteristics of breast cancer cells. The target genes of miR-768-3p in breast cancer were identified by bioinformatics software and detected by luciferase reporter assay. Compared with normal tissues and normal breast cancer cells, miR-768-3p was significantly decreased in breast cancer tissues and cancer cells (P<0.001). The reduction in miR-768-3p was significantly associated with lymph node metastasis (P = 0.040), Tumor Node Metastasis stage (P = 0.035), and cancer subtype (P = 0.008). In addition, patients with low miR-768-3p expression had a shorter overall survival time (log-rank P = 0.022) compared with those with high expression and miR-768-3p may be a potential prognostic marker (hazard ratio=4.637; 95% confidence interval=1.296-16.597; P = 0.018). When transfected with miR-768-3p inhibitor, cell viability, migration and invasion were significantly promoted compared with the control group (P<0.05). In addition, eukaryotic translation initiation factor 4E (eIF4E) was the target gene of miR-768-3p in breast cancer. All experiments confirmed that miR-768-3p, a tumor suppressor, inhibited the viability, migration and invasion of breast cancer cells through eIF4E. miR-768-3p may be a potential prognostic marker of breast cancer and may participate in the progression of breast cancer.