miR-21 is negatively correlated with miR-203 in esophageal cancer tissues and functions oppositely in tumor progression

Objectives: It is well-known that microRNAs (miRNAs) function as vital regulators in the development of human malignancies as tumor suppressors or oncogenes. MiR-21 and miR-203 have been both characterized as functional miRNAs in esophageal cancer. This study aimed to evaluate the internal relationship between the two miRNAs. Methods: A total of 56 patients of esophageal cancer were enrolled and expression of miR-21 and miR203 were detected by qRT-PCR. Associations between the two miRNAs expression in different categories of these esophageal cancer samples were analyzed. Inhibitor of miR-21 and/or mimics of miR-203 was introduced into EC9706 cells and cell proliferation was measured by crystal violet staining assay. Results: MiR-21 expression was significantly elevated while miR-203 was decreased in tissue samples of esophageal cancers compared to those in the paired normal adjacent tissues. Negative correlation was found in these two miRNAs expression. Crystal violet staining assays validated that inhibition of miR-21 or forced expression of miR-203 promoted cell proliferation. In addition, inhibition of miR-21 expression led to obvious upregulation of miR-203, and forced miR-203 expression caused miR-21 repression. Conclusion: Negative correlation and opposite functions of miR-21 and miR-203 were established in esophageal cancer. The future combined assay of miR-21 and miR-203 may help to treat this disease.