MiR-218-5p promotes breast cancer progression via LRIG1

Abstract Background : MiR-218-5p is a small non-coding RNA acting as either oncogenes or tumor suppressor genes in human cancer. The expression levels of some miRNAs in human breast cancer plays a potential role in disease pathogenesis. Methods : Thirty pairs of invasive ductal carcinoma and adjacent specimens were included in the study. Breast tissues cell lines MCF-7 and MDA-MB-231 were identified as a breast cancer research cell line. MiR-218-5p mimics, miR-218-5p inhibitor, or negative controls were transfected. Specific antibodies were probed with LRIG1, ErbB2, and EGFR. Proliferation, migration, cell cycle and apoptosis, dual-luciferase reporter assay and immunohistochemistry were used to analyze miR-218-5p、LRIG1 and so on. Results : It was shown that miR-218-5p expression was higher in 30 breast cancer specimens than adjacent normal breast tissues. In human breast cancer cells MCF-7 and MDA-MB-231, restoring miR-218-5p promoted cell proliferation and migration and inhibited cell apoptosis and cell cycle arrest in the G1 stage. Luciferase assays indicated miR-218-5p could bind with its putative target site in the 3'-untranslated region (3'-UTR) of LRIG1. RT-qPCR, western blot, and immunocytochemistry analyses all indicated miR-218-5p overexpression results in LRIG1 downregulation at the mRNA and protein levels. ErbB2 and EGFR were found to be downstream effectors of miR-218-5p. Conclusion : MiR-218-5p promotes ErbB2 and EGFR expression by inhibiting LRIG1 in breast cancer cells, which suggests miR-218-5p and LRIG1 may act as an oncogene in breast cancer and it could be used as a therapeutic target for breast cancer treatments. Keywords: Breast cancer; miR-218-5p; LRIG1; Oncogene