LncRNA SNHG6 promotes proliferation, invasion and migration in colorectal cancer cells by activating TGF-β/Smad signaling pathway via targeting UPF1 and inducing EMT via regulation of ZEB1

Background: Long noncoding RNAs (lncRNAs) are non-protein coding transcripts longer than 200 nucleotides in length. They drive many important cancer phenotypes through their interactions with other cellular macromolecules including DNA, RNA and protein. Recent studies have identified numerous lncRNAs active in colorectal cancer (CRC). The lncRNA small nucleolar RNA host gene 6 (SNHG6) has been reported to have an oncogenic role in multiple cancers. However, the biological role and mechanism of SNHG6 in the tumorigenesis of CRC has not been reported in-deep. Methods: The Cancer Genome Atlas (TCGA) database and GEO database were used to identify SNHG6 expression in different human cancers and explore the relationship between SNHG6 expression and patient prognosis using Kaplan-Meier method analysis. SNHG6 expression in 77 pairs of clinical CRC tissues and different CRC cell lines were analyzed by quantitative real-time PCR (qRT-PCR). A CCK-8 assay was used to assess cell proliferation, transwell assay to detect the cell metastasis, and tumor growth was investigated with a nude mice model in vivo. Whether UPF1 and ZEB1 are downstream targets of SNHG6 was verified by bioinformatics target gene prediction, qRT-PCR and western blot. Results: TCGA data showed that SNHG6 was significantly upregulated in colorectal cancer samples in comparison with healthy data samples (P < 0.01). CRC patients with high levels of SNHG6 had a significantly shorter overall survival than those with low levels of SNHG6 (P = 0.0162). qRT-PCR confirmed that the expression of SNHG6 was significantly upregulated in CRC tissues and cell lines. Upregulation of SNHG6 expression induced RKO and HCT116 cell proliferation as well as RKO cell metastasis, while downregulation of SNHG6 expression supressed the proliferation and metastasis of RKO cells and tumor growth in vivo. UPF1 was upregulated and ZEB1 was decreased when SNHG6 knockdown, regulating the TGF-β/Smad pathway and inducing EMT respectively. Conclusions: SNHG6 may play an oncogenic role in CRC cells by activating TGF-β/Smad signaling pathway via targeting of UPF1 and inducing EMT via regulating ZEB1. This could be a prognostic biomarker and therapeutic target for CRC.