[Periostin regulated by let-7/miR-98 family mediates the apoptosis and epithelial-mesenchymal transition of colon cancer].

ABSTRACT

Objective: To observe the expressions of periostin (Postn) in colon cancer tissues and cells, and to investigate its biological effect and mechanism in colon cancer cells. Methods: Real-time quantitative polymerase chain reaction (RT-qPCR) and western blot were used to detect the expressions of Postn, let-7a and miR-98 in 20 pairs of colon cancer tissues and adjacent normal tissues, colon cancer cell lines including SW480, HT-29, HCT-116 and human normal colon epithelial cell NCM460. Small interfering RNAs (siRNAs) of Postn, pcDNA3.1-Postn plasmids, let-7a mimic and its negative control let-7a mimic-NC, miR-98 mimic and its negative control miR-98 mimic-NC were transfected into HCT-116 cells. 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2H tetrazolium bromide (MTT) was used to detect cell viability. Flow cytometry was used to detect cell apoptosis. Luciferase reporter gene assay was used to determine the targeting relationship between miRNAs and Postn. Results: Compared with adjacent normal tissues, Postn expression was up-regulated (P<0.05) while let-7a/miR-98 expression was down-regulated (P<0.05) in colon cancer tissues. Compared with NCM460 cells, Postn expression was up-regulated (P<0.05) while let-7a/miR-98 expression was down-regulated (P<0.05) in SW480, HT-29 and HCT-116 cells. In colon cancer tissues, the expression of Postn was negatively correlated with the expressions of let-7a and miR-98 (r=-0.69, P<0.001; r=-0.80, P<0.001). Inhibition of Postn in vitro reduced the viability of HCT-116 cells [(53.73±7.63)%, P<0.05], increased the apoptotic rate [(22.88±3.40)%, P<0.05], enhanced the expression of epithelial-mesenchymal transition (EMT) marker E-cadherin (2.44±0.39, P<0.05), while down-regulated the expressions of N-cadherin and Vimentin (0.44±0.07 and 0.38±0.06, P<0.05). Overexpression of Postn in vitro enhanced the cell viability of HCT-116 cells [(134.41±8.82) %, P<0.05], decreased the expression of E-cadherin (0.55±0.09, P<0.05), increased the expressions of N-cadherin and Vimentin (2.93±0.42 and 2.24±0.34, P<0.05), but had no effect on the apoptotic rate (P>0.05). Overexpression of let-7a or miR-98 partially reversed the biological effects of Postn overexpression in colon cancer cells, which implicated that Postn was a target gene of let-7a/miR-98. Conclusions: Postn is a cancer-promoting molecule of colon cancer, and inhibition of Postn expression can increase the apoptotic rate of colon cancer cells and repress EMT. Postn expression and function is regulated by let-7a/miR-98.