[The expression and functional mechanism of long non-coding RNA LINC00339 in colorectal cancer]

Objective: To investigate the expression of long non-coding RNA LINC00339 in colorectal cancer patients and its effect and mechanism on proliferation and apoptosis of colorectal cancer cells. Methods: A retrospective analysis of 158 pathology-confirmed colorectal cancer patients, who were enrolled from August 2015 to January 2017, was performed. LINC00339 expression in colorectal cancer tissues and adjacent colorectal sampleswas detected by Real-time PCR. The correlation between LINC00339 expression and clinicopathological features as well as the relationship between LINC00339 and microRNA (miR)-218 expression was assayed. The interaction between LINC00339 and miR-218 was further confirmed by dual luciferase report system. Downregulation of LINC00339 was performed by siRNA interference technology in LoVo and HCT116 cells. Real-time PCR was used to detect miR-218 expression. 3-(4,5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT) analysis was carried out to examine cell viability. Flow cytometry was used to determine cell apoptosis. Additionally, LINC00339 siRNA and miR-218 antagomirs (anti-miR-218) were co-transfected into LoVo and HCT116 cells, and then cell viability and apoptosis were detected. Results: LINC00339 expression was significantly increased in colorectal cancer tissues compared with adjacent colorectal tissues (4.69±1.52 vs 1.02±0.38, P<0.05). LINC00339 expression was not related to the age and gender of patients (P>0.05), but was associated with TNM stage, lymphatic metastasis, tumor maximum diameters, and differentiation degree (all P<0.05). LINC00339 expression was negatively correlated with miR-218 expression in colorectal cancer tissues (P<0.05). miR-218 mimics remarkably suppressed the fluorescence intensity of wild-type LINC00339 plasmid (P=0.001), but did not affect the fluorescence intensity of the mutant ones(P=0.88). Knockdown of LINC00339 remarkably inhibited proliferation, but promoted apoptosis of LoVo and HCT116 cells (all P<0.05). Compared with cells transfected with LINC00339 siRNA only, downregulation of miR-218 elevated proliferation and decreased apoptosis of LoVoand HCT116 cells. Conclusions: LINC00339 expression is upregulated in colorectal cancer tissues and correlated with patients' clinicopathological features. LINC00339 promotes proliferation, and suppresses apoptosis of colorectal cancer cells via downregulating miR-218.