MiRNA-221 negatively regulated downstream p27Kip1 gene expression involvement in pterygium pathogenesis

PURPOSE MiRNAs are small noncoding RNAs that have been implicated in tumor development. They regulate target gene expression either by mRNA degradation or by translation repression. Activation of β-catenin has been linked to pterygium progression. Here, we hypothesize that β-catenin-associated miRNA, miRNA-221, and downstream p27Kip1 gene expression are correlated with the pathogenesis of pterygium. METHODS We collected 120 pterygial and 120 normal conjunctival samples for this study. Immunohistochemistry and real-time reverse transcription (RT)-PCR were performed to determine β-catenin protein localization, miR-221, and p27Kip1 gene expression. Pterygium cell line (PECs) cell models were used to confirm the effect of β-catenin, miR-221, and p27Kip1 gene in the proliferation of pterygium cells. RESULTS Seventy-two (60.0%) pterygial specimens showed high miR-221 expression levels, which was significantly higher than the control groups (13 of 120, 10.8%, p<0.0001). MiR-221 expression was significantly higher in β-catenin-nuclear/cytoplasmic-positive groups than in β-catenin membrane-positive and negative groups (p=0.001). We also found that p27Kip1 gene expression in pterygium was negatively correlated with miR-221 expression (p=0.002). In the clinical association, miR-221 expression was significantly higher in the fleshy and intermediate groups than in the atrophic group (p=0.007). The association of miR-221, p27Kip1 and proliferation of pterygium were also confirmed in the PECs model. CONCLUSIONS Our study demonstrated that activation of β-catenin in pterygium may interact with miR-221, resulting in p27Kip1 gene downregulation that influences pterygium pathogenesis.