Role of microRNA let-7 and effect to HMGA2 in esophageal squamous cell carcinoma

To investigated the role of microRNA (miRNA) let-7 and its regulation on high mobility group A2 (HMGA2) protein expression in esophageal squamous cell carcinoma (ESCC). Let-7 expressions were detected in esophageal cancer cell line Eca109, and 45 paired of fresh ESCC and normal adjacent tissues (NAT) by real-time quantitative PCR (qRT–PCR). To evaluate the role of let-7 and HMGA2, cell proliferations were analyzed with synthetic let-7 mimics- or its inhibitor-transfected cells. Moreover, expressions of HMGA2 were performed by western blotting and further confirmed by 150 paired of formalin-fixed, paraffin-embeded (FFPE) ESCC and NAT by immunohistochemistry (IHC). In Eca109, when transfected with let-7 mimics, accumulation of let-7 was obviously suppressed cell proliferation with approximately 14%. Conversely, when Eca109 transfected with let-7 inhibitor, expression of let-7 was declined, which promoted cell proliferation with approximately 16%. Both of them had no effect on the level of HMGA2 mRNA. The transcription of let-7 inversely correlated with HMGA2 protein. Compared with the NAT, expression of let-7 was significantly lower in ESCC tissues (P < 0.05), and there was a significant correlation between low expression of let-7 and lymph node metastasis in ESCC (P < 0.05). Moreover, the protein expression of HMGA2 was significantly higher in ESCC compared with NAT (P < 0.05). However, mRNA expression of HMGA2 had no obvious significance between them. The present results demonstrated that let-7 and HMGA2 involved in ESCC carcinogenesis. Let-7 could inhibit cell proliferation and lower expressed in ESCC, and there was a correlation between let-7 lower expression and lymph node metastasis in ESCC patients. As well as, HMGA2 protein expression was significantly higher in ESCC than that in NAT, and HMGA2 may negatively regulated by let-7 at the post- transcriptional level in ESCC.