Long non-coding RNA LINC01503 promotes colorectal cancer cell proliferation and invasion by regulating miR-4492/FOXK1 signaling

Increasing evidence indicates that long non-coding RNAs (lncRNAs) are closely associated with the progression of human cancer, including colorectal cancer (CRC). A previous study suggested that lncRNA LINC01503 promotes squamous cell carcinoma progression. However, the function of LINC01503 in CRC has remained elusive. The present study indicated that LINC01503 was significantly upregulated in CRC tissues compared with that in adjacent normal tissues as detected by reverse transcription-quantitative polymerase chain reaction. It was demonstrated that knockdown of long intergenic non-protein coding RNA (LINC)01503 markedly inhibited the proliferation and invasion of CRC cells, whereas overexpression of LINC01503 had the opposite effects, as indicated by Cell Counting kit-8 and Transwell assays. Mechanistically, it was revealed that LINC01503 serves as a sponge for microRNA (miR)-4492, which targets forkhead box K1 (FOXK1) in CRC cells. In addition, luciferase reporter assays demonstrated the direct binding of miR-4492 mimics to LINC01503 and to a sequence in the 3'-untranslated region of FOXK1. Furthermore, it was demonstrated that overexpression of LINC01503 reduced the availability of miR-4492 in CRC cells. Furthermore, miR-4492 mimics inhibited FOXK1 expression, while simultaneous overexpression of LINC01503 abolished this effect. Finally, it was demonstrated that restoration of FOXK1 abolished the inhibitory effect of LINC01503 knockdown on CRC cell proliferation and invasion. Taken together, the present results suggested that LINC01503 promotes CRC progression via acting as a competing endogenous RNA for miR-4492/FOXK1.