Long non‑coding RNA TTN‑AS1 promotes breast cancer cell migration and invasion via sponging miR‑140‑5p

Breast cancer (BC) is one of the most common fatal cancers. Recent studies have identified the vital role of long non-coding RNAs (lncRNAs) in the development and progression of BC. In this investigation, lncRNA TTN-AS1 was studied to identify its function in the metastasis of BC. TTN-AS1 expression of tissues was detected by real-time quantitative polymerase chain reaction (RT-qPCR) in 56 BC patients. Wound healing assay and transwell assay were used to observe the biological behavior changes of BC cells through gain or loss of TTN-AS1. In addition, luciferase assays and RNA immunoprecipitation (RIP) assay were performed to discover the potential targets of TTN-AS1 in BC cells. TTN-AS1 expression level in BC samples was higher than that of adjacent tissue. Besides, the ability of cell migration and invasion of BC cells was inhibited after TTN-AS1 was silenced, while cell migration and cell invasion of BC cells were promoted after TTN-AS1 was overexpressed. In addition, miR-140-5p was upregulated after silencing of TTN-AS1 in BC cells, while miR-140-5p was downregulated after overexpression of TTN-AS1 in BC cells. Furthermore, luciferase assays and RIP assay showed that miR-140-5p was a direct target of TTN-AS1 in BC. Our study uncovered a new oncogene in BC and suggests that TTN-AS1 enhances BC cell migration and invasion via sponging miR-140-5p, which provides a novel therapeutic target for BC patients.