MiR-125b inhibits anaplastic thyroid cancer cell migration and invasion by targeting PIK3CD

Emerging evidences indicate that dysregulated microRNAs are implicated in the process of tumorigenesis and progression. The miRNA-125b (miR-125b) is downregulated and identified as tumor supressor in various cancers including thyroid cancer. However, the role and mechanism of miR-125b in anaplastic thyroid cancer (ATC) migration and invasion remain unknown. In the present study, the expression levels of miR-125b were downregulated and the expression levels of phosphoinositide 3-kinase catalytic subunit delta (PIK3CD) were upregulated in ATC tissues and cell lines. Moreover, miR-125b expression was negatively related to PIK3CD expression in ATC tissues. A computational search and luciferase assay identified PIK3CD as a direct target of miR-125b in ATC and PIK3CD expression was downregulated by miR-125b in ATC cells. In terms of function, miR-125b repressed migration and invasion of ATC cells, whereas PIK3CD overexpression reversed this effect. Furthermore, we showed that exogenous miR-125b decreased the PI3K, phospho-Akt, and phospho-mTOR expression in ATC cells. In conclusion, these results indicated that miR-125b suppressed ATC cell migration and invasion by targeting PIK3CD expression, and suggested novel potential therapeutic targets for the treatment of ATC.