Abstract
Objective: This study investigated the mechanism of methyltransferase-like 14 (METTL14)-mediated epigenetic transcriptome modification of RAD21 mRNA in inhibiting thyroid cancer (TC) development. Methods: TCGA and Starbase databases were used to predict the differential expression of METTL14 in TC tissues. First, 48 patients were enrolled. Immunohistochemistry, reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and Western blot (WB) were employed for detecting METTL14 and RAD21 expression levels. The overall RNA N6-methyladenosine (m6A) methylation level was measured using m6A-RNA immunoprecipitation (MeRIP). TC cell lines were transfected with Ad-METTL14 and/or Ad-RAD21, and then detected for proliferation, apoptosis, migration, and invasion using cell count kit-8 assay, flow cytometry, and Transwell assay, respectively. MeRIP-qPCR was adopted to detect the RAD21 m6A modification level. RT-qPCR was applied for detecting RAD21 mRNA stability in actinomycin D-treated cells. RIP was implemented to detect METTL14-RAD21 interaction. Tumor formation assay was performed in nude mice. Tumor weight and volume were recorded. The collected tumor tissues were measured for Ki67-positive cell levels using immunohistochemistry, and METTL14 and RAD21 protein levels using WB. Results: METTL14 was notably downregulated and RAD21 was upregulated in TC tissues and cells. METTL14 overexpression inhibited TC cell proliferation, migration, and invasion, and promoted cell apoptosis. METTL14 overexpression reduced RAD21 mRNA stability and inhibited RAD21 expression through m6A modification. RAD21 upregulation caused opposite results to METTL14 overexpression on inhibiting TC cell malignant behaviors. METTL14 overexpression inhibited tumor formation in nude mice in vivo. Conclusion: METTL14 inhibits tumorigenesis in TC mice in vivo by mediating m6A modification of RAD21 and decreasing RAD21 mRNA stability.