[Expression of microRNA-17-5p in esophageal squamous cell carcinoma and its effects on cell proliferation and invasion].

To explore the expression of microRNA-17-5p (miR-17-5p) in esophageal squamous cell carcinoma (ESCC) and its effects on cell proliferation and invasion ability. Real-time quantitative PCR (RT-qPCR) was used to detect the miR-17-5p level in ESCC tissues and cells. MiR-17-5p inhibitor and negative control (NC) were transfected into EC9706 and TE1 cells, and miR-17-5p expression was examined by using RT-qPCR. Cell counting kit-8 (CCK-8) and EdU were conducted to detect cell proliferation and Transwell chamber was used to investigate cell invasion ability. Dual-luciferase reporter assay was used to detect the direct interaction of miR-17-5p and retinoblastoma-like protein-2 (RBL2). Western blot and RT-qPCR were used to detect the expression of RBL2 in ESCC tissues, respectively. Finally, the correlation between RBL2 and miR-17-5p was analyzed. The miR-17-5p level in ESCC tissues was 4.222±0.392, significantly higher than 1.081±0.046 in normal esophageal epithelial tissues (<0.001). The expressions of miR-17-5p in ESCC cells, including EC9706, Eca109, TE1, KYSE450, KYSE70 and KYSE520, were 13.84±1.266, 6.453±0.293, 11.41±0.520, 2.613±0.548, 5.251±0.239 and 4.251±0.195, respectively, all obviously higher than (1.007±0.079) in normal esophageal epithelial cell Het-1A (<0.05). The miR-17-5p level in patients with ESCC ⅢⅣ was 5.094±0.562, markedly higher than 2.934±0.364 in patients with ESCCⅠⅡ(<0.01). Moreover, the miR-17-5p level in ESCC patients with lymph node metastasis was 5.523±0.634, markedly higher than 3.533±0.461 in ESCC patients without lymph node metastasis (<0.05). The survival ratio of ESCC patients with higher miR-17-5p level was evidently lower than that of ESCC patients with lower miR-17-5p level (<0.05). MiR-17-5p inhibitor significantly downregulated the miR-17-5p expression in EC9706 and TE1, which suppressed cell proliferation and invasion ability. Dual-luciferase reporter assay revealed that co-transfection of 3' untranslated region-wild type (3'UTR-WT) of RBL2 and miR-17-5p mimic significantly reduced luciferase activity in EC9706 and TE1 cells (<0.01), which implicated that RBL2 was the direct target of miR-17-5p. The result of western blot revealed that RBL2 protein expressions in miR-17-5p group of EC9706 and TE1 cells were 0.936±0.055 and 0.923±0.048, obviously higher than 0.087±0.019 and 0.102±0.010 in control group (<0.001). The expression of RBL2 in ESCC tissues was 0.219±0.510, markedly lower than 0.983±0.324 in normal esophageal epithelial tissues (<0.001). The miR-17-5p level exhibited a negative correlation with RBL2 level in ESCC tissues (=-0.462, <0.001). Downregulation of RBL2 reversed the miR-17-5p inhibitor induced suppression of cell proliferation and invasion ability. MiR-17-5p participates in the carcinogenesis and development of ESCC, thus may be a potential therapeutic target for ESCC patients.