Long non-coding RNA TMPO-AS1 promotes tumor progression via sponging miR-140-5p in breast cancer

Long non-coding RNAs (lncRNAs) are involved in carcinogenesis and tumor suppression, and are novel biological tumor regulators. However, the functional roles of lncRNAs and their underlying dysregulation mechanisms in breast cancer are not completely understood. The aim of the present study was to investigate the clinical significance and biological functions of lncRNA TMPO antisense RNA 1 (TMPO-AS1) in breast cancer. TMPO-AS1 levels were measured in human cancer tissues and breast cancer cell lines, and the functional roles of TMPO-AS1 in breast cancer cells were investigated by performing in vitro and in vivo assays. Additionally, luciferase reporter assays were conducted to detect the association between microRNA (miR)-140-5p and TMPO-AS1. TMPO-AS1 expression levels were significantly increased in breast cancer tissues and cell lines compared with adjacent non-cancerous tissues and MCF-10A cells, respectively. In vitro and in vivo studies indicated that TMPO-AS1 knockdown significantly suppressed breast cancer cell viability at 48 and 72 h compared with the small interfering (si)RNA negative control group (NC; siNC). TMPO-AS1 knockdown in vitro inhibited MCF-7 and T47D cell migration and invasion compared with the siNC group. TMPO-AS1 knockdown in metastatic breast cancer cells also decreased metastatic colonization in the mouse lung compared with the short hairpin RNA NC group. Mechanistically, TMPO-AS1 promoted cellular viability and migration as a competing endogenous RNA by sponging miR-140-5p. The results suggested that TMPO-AS1 may serve as a potential therapeutic target in patients with breast cancer.