Long non-coding RNA SNHG1 promotes breast cancer progression by regulation of LMO4

Long non-coding RNA (lncRNA) small nucleolar RNA host gene 1 (SNHG1) was reported to be a critical regulator of tumorigenesis and is frequently deregulated in several cancer types. However, the exact mechanism by which SNHG1 contributes to breast cancer progression has not been fully elucidated. The identification of the molecular mechanism of SNHG1 is important for understanding the development of breast cancer and for improving the prognosis of the patients with this disease. In the present study, increased expression levels of SNHG1 were noted in breast cancer tumors following analysis of differentially expressed lncRNAs between 1,063 tumor and 102 normal tissues derived from The Cancer Genome Atlas Breast Invasive Carcinoma (TCGA-BRCA) dataset. This finding was further validated using 50 pairs of normal and tumor tissues that were collected from patients with breast cancer. Notably, SNHG1 expression was significantly correlated with estrogen receptor (ER)/progesterone receptor (PR) negative status (ER-/PR-) and advanced clinical stage in breast cancer tissues. Knockdown of SNHG1 led to cell growth arrest, cell cycle redistribution and cell migration inhibition of breast cancer cells. The miRDB database predicted that miR-573 interacts with SNHG1. RT-PCR confirmed the negative regulation of miR-573 levels by SNHG1 in breast cancer cells and the Dual-luciferase reporter assay confirmed their complementary binding. The repression of miR-573 by SNGH1 decreased LIM domain only 4 (LMO4) mRNA and protein expression levels in the breast cancer cell lines tested and induced the expression of cyclin D1 and cyclin E. In vitro experiments indicated that LMO4 overexpression could reverse siSNHG1-induced cell growth arrest, cell cycle redistribution and inhibition of cell migration in breast cancer cells. Moreover, the tumor xenograft model indicated that SNHG1 knockdown inhibited MDA-MB-231 growth in vivo and LMO4 overexpression reversed the tumor growth inhibition induced by SNHG1 knockdown. The present study demonstrated that SNHG1 acts as a novel oncogene in breast cancer via the SNHG/miR-573/LMO4 axis and that it could be a promising therapeutic target for patients with breast cancer.