Overexpression of circRNA circFAT1 in Endometrial Cancer Cells Increases Their Stemness by Upregulating miR-21 Through Methylation

Background: Circular (Circ)RNA circFAT1 play tumor-suppressive or oncogenic roles in different cancers. Microarray analysis observed altered expression of circFAT1 in endometrial cancer (EC) and its inverse correlation with miR-21. Materials and Methods: Expression of circFAT1 and miR-21 in EC and paired nontumor tissues collected from 62 EC patients was analyzed by quantitative reverse transcription PCR (RT-qPCR). An experiment was conducted to evaluate the expression and interaction between circFAT1 and miR-21, followed by RT-qPCR and methylation-specific PCR. The role of circFAT1 and miR-21 in regulating the stemness was assessed by cell stemness assay. Heml 1.0 software was used to show differential gene expression. ANOVA Tukey's test and Pearson's correlation coefficient was used. Results: CircFAT1 was upregulated in EC and positively correlated with miR-21 across EC tissues. In RL95-2 and HEC-1-A cells, overexpression of circFAT1 increased the expression levels of miR-21 and decreased the methylation of miR-21 gene, whereas overexpression of miR-21 did not alter the expression of circFAT1. Cell stemness analysis showed that overexpression of circFAT1 and miR-21 increased cell stemness, and miR-21 inhibition decreased cell stemness. Moreover, inhibitor of miR-21 suppressed the role of circFAT1. Conclusions: In conclusion, circFAT1 is upregulated in EC and it may increase cancer cell stemness by upregulating miR-21.