p53-associated miRNAs repress lncRNA ZFAS1 to retard the proliferation of papillary thyroid carcinoma.

INTRODUCTION: Thyroid carcinoma is the most frequent malignancy among endocrine-related tumours. Papillary thyroid carcinoma (PTC) is the main type of thyroid carcinoma, and almost 80% cases of thyroid carcinoma are diagnosed as PTC. The molecular mechanism underlying PTC progression is unclear. This study aims to investigate the potential mechanisms of zinc finger antisense 1 (ZFAS1) function in PTC.

MATERIAL AND METHODS: The expression of ZFAS1 and p53 was determined by quantitative polymerase chain analysis (qPCR) in PTC tissues derived from 20 PTC patients. Quantitative chromatin immunoprecipitation assay (qChIP) analysis was performed to validate the target of ZFAS1/p53 and miRNAs/p53. The Gene Expression Omnibus (GEO) dataset GSE94908 was analysed to obtain the differentially expressed p53-associated microRNAs (miRNAs). Luciferase assay validated the target of ZFAS1/miRNAs, and 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to determine the cell proliferation.

RESULTS: The expression of ZFAS1 was up-regulated in the tissues derived from PTC patients, and the expression of ZFAS1 was negatively associated with p53 expression in PTC. The expression of ZFAS1 was significantly higher in the MDA-T120 cells harbouring mutant p53. We validated that ZFAS1 is a direct target of p53. In PTC cells, p53 directly repressed the ZFAS1 expression. In addition, we determined that miR-135b-5p and miR-193a-3p are directly induced by p53 in PTC cells. Interestingly, p53-targeted miR-135b-5p, miR-193a-3p, and miR-34b repressed the expression of ZFAS1 via the seed-matching sequences in the 3'-untranslated region (3'-UTR) of ZFAS1, and thereby suppressed PTC cell proliferation induced by ZFAS1.

CONCLUSION: The oncogenic lncRNA ZFAS1 is directly repressed by p53 in PTC. p53-mediated miRNAs including miR-135b 5p, miR-193a-3p, and miR-34b repress ZFAS1 expression, and thereby inhibit the proliferation of PTC.