HMGA 2 is down‐regulated by micro RNA let‐7 and associated with epithelial–mesenchymal transition in oesophageal squamous cell carcinomas of K azakhs

Aims To investigate the expression of let‐7 and its regulation of high‐mobility group A2 protein ( HMGA 2), and to verify the relationship between let‐7, HMGA 2 and the process of epithelial–mesenchymal transition ( EMT ), in oesophageal squamous cell carcinomas ( OSCC ) of K azakh patients. Methods and results Expression of let‐7 was significantly lower in E ca109 cells than in normal oesophageal squamous epithelium ( P   =   2.4 × 10 −7 ). Increased accumulation of let‐7 after transfection of Eca109 cells with synthetic let‐7 inhibited cell proliferation. Let‐7 could repress expression of HMGA 2 after co‐transfection with let‐7 and HMGA 2 ( P   =   0.002). Moreover, let‐7 expression was observed less frequently ( P   =   2.0 × 10 −8 ), and HMGA 2 expression more frequently ( P   =   1.0 × 10 −10 ), in OSCC than in normal adjacent tissues; and let‐7 expression was observed less frequently in OSCC from K azakh patients than in those from Han and Uygur patients ( P   =   0.041). There was a reverse correlation between expression of let‐7 and HMGA 2 ( P   =   0.018). Expression of Snail was statistically higher in K azakhs' OSCC ( P   =   0.029), and was correlated with depth of invasion ( P   =   0.021) and HMGA 2 expression ( P   =   0.026). Conclusions Expression of let‐7 can suppress cell proliferation by acting directly on regulation of HMGA 2 in OSCC . High expression of Snail and its correlation with HMGA 2 expression and tumour invasion suggest that HMGA 2 may be involved in EMT in the OSCC of Kazakh patients.