Abstract: Objective To explore the effect of miR-25 on invasion and migration of esophageal cancer and its potential ability as a biomarker for the diagnosis of esophageal cancer. Methods (1) The expression levels of miR-25 in cancer tissues and adjacent tissues of 54 patients with esophageal cancer were detected by fluorescence quantitative PCR (qPCR). (2) Human esophageal cancer cells EC109 were divided into the miR-25 mimic group, the NC mimic group, the miR-25 inhibitor group and the NC inhibitor group. After transfection of the corresponding sequences, miR-25 overexpression and interference efficiency were detected by qPCR. Transwell assay was used to detect the effect of overexpression or silencing of miR-25 on the invasion and migration of EC109 cells. Targetscan database predicted the target gene of miR-25 and selected the target gene salt-induced kinase 1 (SIK1). Western blot assay and double luciferase report experiment identified the targeting relationship between silencing and overexpression of miR-25 and SIK1. (3) EC109 cells were divided into the pcDNA 3.1 group, the SIK1 overexpression group and the miR-25 + SIK1 overexpression group. Transwell assay was used to detect the effect of miR-25 targeting SIK1 on the invasion and migration of EC109 cells. (4) The plasma exosomes of patients with esophageal cancer (54 cases) and healthy controls (54 cases) were extracted, the relative expression of miR-25 in plasma exosomes was compared between the two groups. The correlation between miR-25 in tissues and plasma exosomes of patients with esophageal cancer was analyzed. Results (1) The relative expression level of miR-25 was higher in esophageal carcinoma tissues than that in adjacent tissues. (2) After overexpression of miR-25, the invasion and migration ability of EC109 cells increased, while after silencing miR-25 expression, the invasion and migration ability of EC109 cells decreased. The Targetscan database predicted that SIK1 was the target gene of miR-25. Western blot assay showed that the expression of SIK1 protein decreased after miR-25 overexpression. On the contrary, the protein expression of SIK1 increased after knocking down the expression of miR-25. (3) Transwell experiment showed that compared with the pcDNA 3.1 group, the number of invasion and migration of EC109 cells decreased in SIK1 overexpression group, while the number of invasion and migration of EC109 cells increased in the miR-25 and SIK1 overexpression group compared with the SIK1 overexpression group. (4) The expression of miR-25 in plasma exosomes of esophageal cancer was higher than that in healthy controls, and the expression of miR-25 in esophageal cancer was positively correlated with that in plasma exosomes. Conclusion miR-25 may promote the invasion and migration of esophageal cancer through targeting the regulation of SIK1, and miR-25 has the potential as a biomarker for the early detection of esophageal cancer.

Key words: esophageal neoplasms, microRNAs, cell movement, exosomes, miR-25, salt-induced kinase 1, EC109 cells