The up-regulated lncRNA DLX6-AS1 in colorectal cancer promotes cell proliferation, invasion and migration via modulating PI3K/AKT/mTOR pathway.

Abstract

Colorectal cancer (CRC) is one of the leading causes of cancer-related deaths around the world. Recently, using the high-throughput techniques, long non-coding RNAs (lncRNAs) have been shown to play an important role in CRC progression. In the present study, we aimed to determine lncRNA DLX6 Antisense RNA 1 (DLX6-AS1) in CRC tissues and cell lines and to investigate the molecular mechanisms of DLX6-AS1 in CRC progression. Quantitative real-time PCR was performed to detect gene expression; cell counting kit-8, colony formation, cell invasion, and migration assays were performed to determine cell proliferation, invasion, and migration, respectively; caspase-3 activity assay kit was used to detect caspase-3 activity; in vivo tumor growth was evaluated in a nude mice xenograft model. DLX6-AS1 was up-regulated in 60 CRC tissues when compared to normal adjacent colorectal tissues, and high expression of DLX6-AS1 was correlated with advanced T stage and distant metastasis in CRC patients. The up-regulation of DLX6-AS1 was further confirmed in CRC cell lines. The gain-of-function assays showed that DLX6-AS1 overexpression promoted HCT116 cell proliferation, invasion, and migration, but inhibited cell apoptosis; while the loss-of-function assays showed that DLX6-AS1 knockdown exerted the opposite effects in SW480 cells. In vivo studies revealed that DLX6-AS1 knockdown suppressed tumor growth in the nude mice xenograft model. In addition, DLX6-AS1 overexpression caused an increase in the phosphorylated phosphoinositide 3-kinase (p-PI3K), p-AKT and p-mammalian target of rapamycin (mTOR) protein levels, and DLX6-AS1 knockdown had the opposite effects. Blockade of PI3K/AKT/mTOR signalling pathway by using mTOR inhibitor partially abolished the enhanced effects of DLX6-AS1 overexpression on CRC cell proliferation and metastasis. In summary, our data indicated that DLX6-AS1 promoted CRC cell proliferation, invasion, and migration but inhibited cell apoptosis via targeting PI3K/AKT/mTOR signalling pathway, suggesting the key role of DLX6-AS1 in CRC progression.