MicroRNA‑509 targets PAX6 to inhibit cell proliferation and invasion in papillary thyroid carcinoma.

MicroRNAs (miRNAs/miRs) negatively regulate the expression of numerous genes and therefore contribute to the occurrence and development of papillary thyroid carcinoma (PTC). Hence, further investigation into the specific roles of miRNAs in PTC is valuable for developing effective therapeutic methods for patients with this disease. MiRNA‑509 is dysregulated and serves pivotal roles in several types of human cancer; however, the expression and roles of miR‑509 in PTC and its underlying mechanism require further investigation. In the present study, the expression of miR‑509 in PTC tissues and cell lines was detected and the specific functions of miR‑509 in the progression of PTC were investigated. Additionally, the molecular mechanisms underlying the action of miR‑509 in PTC were determined. The present study demonstrated that miR‑509 was significantly downregulated in PTC tissues and cell lines. MiR‑509 upregulation inhibited the PTC cell proliferation and invasion. Mechanistically, paired box 6 (PAX6) was identified as a novel target of miR‑509 in PTC cells. In clinical PTC samples, miR‑509 was significantly overexpressed and inversely correlated with PAX6 expression. PAX6 restoration effectively reversed the inhibitory effects of miR‑509 overexpression on PTC cell proliferation and invasion. These results demonstrated that miR‑509 may act as a tumor suppressor in PTC by directly targeting PAX6. Thus, miR‑509 may be a potential therapeutic target for the treatment of patients with PTC.