Abstract: The aim of this study was to identify some biomarkers for predicting lymph node metastasis and prognosis of human epidermal growth factor receptor 2 (Her-2)-positive breast cancer (BC). We analyzed correlations between microRNAs (miRNAs) and the prognosis of patients with BC based on data collected from The Cancer Genome Atlas (TCGA) database. The expression levels of miR-455, miR-143, and miR-99a were measured in clinical samples of Her-2-positive BC patients with different degrees of lymph node metastasis. We investigated the impacts of overexpressed miR-455 on the proliferation and invasiveness of MDA-MB-453 cells and measured its effects on the expression of long non-coding RNA (lncRNA) metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) by quantitative real-time polymerase chain reaction (qRT-PCR). The expression of miR-455 was significantly and positively correlated to the prognosis and overall survival (OS) of the BC (P=0.028), according to TCGA information. The expression level of miR-455 was positively correlated with OS and relapse-free survival (RFS) of patients with Her-2-positive BC, and was negatively correlated with the number of metastatic lymph nodes (P<0.05). Transwell assay suggested that MDA-MB-453 cells became much less invasive (P<0.01) after being transfected with miR-455 mimics. During the qRT-PCR, the expression level of MALAT1 declined significantly after transfection (P<0.01). Overexpressed miR-455 significantly inhibited the proliferation and migration of MDA-MB-453 cells and the expression of MALAT1. We conclude that miR-455 may be a useful potential biomarker for forecasting lymph node metastasis and the prognosis of Her-2-positive BC patients. miR-455 may play an important role in lymph node metastasis of BC by interacting with MALAT1.

Key words: Breast cancer (BC); Human epidermal growth factor receptor 2 (Her-2); Lymphatic metastasis; MicroRNA (miRNA); Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1)

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