METTL3-mediated m6A Modification of hsa_circ_0131922 Attenuates the Progression of Papillary Thyroid Cancer by Regulating the p53 Pathway.

Aims: This study aimed to confirm the regulatory role and mechanism of circular RNA (circRNA) hsa_circ_0131922 in Papillary Thyroid Carcinoma (PTC) progression.

Background: Accumulating evidence suggests that N6-methyladenosine (m6A)-modified circular RNAs (circRNAs) perform pivotal functions in various malignancies. However, the specific role of the m6A modification of circRNA mediated by METTL3 in Papillary Thyroid Carcinoma (PTC) remains undocumented.

Objective: In this work, we aimed to examine the molecular mechanisms of a novel m6Amodified circRNA, hsa_circ_0131922, in PTC progression.

Methods: Potential circRNA was identified from GEO datasets. The RNA or protein levels of hsa_circ_0131922, METTL3, p53, and p21 were evaluated by qRT-PCR or western blot assays. The various cellular functions were checked by CCK8, wound healing, transwell, and xenograft tumor assays. MeRIP-qPCR was performed to observe the METTL3-mediated m6A modification of hsa_circ_0131922. Furthermore, the interactions between hsa_circ_0131922 and METTL3 in PTC were analyzed by bioinformatics analysis and various rescue experiments.

Results: The levels of hsa_circ_0131922 were markedly downregulated in PTC tissues and cell lines. In addition, the lower hsa_circ_0131922 levels correlated with poor prognosis in PTC patients. The hsa_circ_0131922 overexpression reduced the malignant phenotypes of PTC cells and activated the p53/p21 pathway. Bioinformatic analysis showed the m6A-modified sites of hsa_circ_0131922, and a positive correlation between hsa_circ_0131922 and METTL3. Moreover, overexpression of METTL3 increased the levels of m6A modification of hsa_circ_0131922. Mechanistically, the anti-tumor effects of hsa_circ_0131922 overexpression have been found to be partially reversed by silencing METTL3 in vivo and in vitro.

Conclusion: The results have demonstrated m6A-modified hsa_circ_0131922 by METTL3 to attenuate the progression of PTC by regulating the p53 pathway. Therefore, hsa_circ_0131922 could be a predictive prognostic biomarker and therapeutic target for PTC.