MicroRNA-144 inhibits proliferation by targeting WW domain-containing transcription regulator protein 1 in papillary thyroid cancer

Papillary thyroid carcinoma (PTC), the most common histological subtype of thyroid cancer, accounts for between 80 and 90% of all thyroid cancer cases. Previous studies have suggested that microRNAs (miRNAs/miRs) are involved in the development of PTC. The aim of the present study was to investigate whether miR-144 inhibits cellular proliferation in PTC. The expression of miR-144 was detected in PTC and corresponding adjacent non-cancerous tissues, and in the PTC cell line IHH4, using reverse transcription-quantitative polymerase chain reaction. Associations between miR-144 expression levels and the clinicopathological characteristics were analyzed. Receiver operating characteristic (ROC) curves were used to assess the diagnostic value of miR-144 expression, and the potential function of miR-144 was investigated in IHH4 cells using a Cell Counting Kit-8 and colony formation assays. Western blotting was applied to analyze the expression level of WW domain-containing transcription regulator 1 (WWTR1) in PTC tissues. miR-144 was significantly downregulated in PTC tissues and the PTC cell line. Low expression of miR-144 was associated with larger tumor sizes (P<0.001). The ROC curves demonstrated that miR-144 may be a potential biomarker for identifying PTC and non-cancerous diseases (sensitivity, 58.7%; specificity, 87.3%) as well as to differentiate PTC with tumor sizes ≥2 cm (sensitivity, 79.2%; specificity, 69.2%). Upregulation of miR-144 significantly suppressed proliferation in IHH4 cells. WWTR1 was overexpressed in PTC tissues compared with in adjacent non-cancerous tissues, and the ectopic expression of miR-144 downregulated WWTR1 in IHH4 cells. Co-transfection with pcDNA-WWTR1 and miR-144 'rescued' the proliferation inhibition. The results of the present study collectively demonstrated that miR-144 is downregulated in PTC, that low expression levels of miR-144 are associated with larger tumor sizes and that miR-144 inhibits cellular proliferation in PTC by targeting WWTR1.