Expression of m6A methylation-modified circRNA in malignant transformation of oral leukoplakia tissue

Objective This study aimed to investigate the expression and clinical significance of N6-methyladenosine (m6A) modification of circular RNA (circRNA) in oral leukoplakia (OLK) and oral squamous carcinoma cell (OSCC) tissues. Methods Using methylation RNA immunoprecipitation high-throughput sequencing technology (MeRIP-seq) and RNA high-throughput sequencing technology (RNA-seq), the first circRNA transcriptome analysis for detecting m6A methylationome profiles in OLK and OSCC tissues was obtained, followed by bioinformatics analysis. The qRT-PCR technique and protein immunoblotting technique were used to detect the expression of m6A methylesterase in OLK versus OSCC tissues. Results In this study, 275 differential m6A methylation peaks were identified in OLK and OSCC, among which 193 peaks were up-regulated and 82 were down-regulated. Additionally, 198 differential m6A methylation modified circRNAs were observed, with 127 up-regulated and 71 down-regulated (FC = 2, P < 0.05). Most of the identified circRNAs that underwent m6A methylation alterations were derived from overlapping regions. It was found that the differential expression of circRNAs was not correlated with the joint analysis of significantly different m6A-circRNAs between the two groups. Furthermore, downregulation of mETTL14 and FTO protein levels was observed in OSCC tissues, although there were no discernible alterations in RNA levels. Conclusion Our study suggests that m6A methylation modification of circRNA may play a role in the development of oral leukoplakia, and that METTL14 and FTO may be important methylation enzymes that influence the development of oral leukoplakia. These findings may open up new research directions for in-depth investigations to clarify the molecular mechanisms of OLK carcinogenesis. Overall design: From August 2020 to September 2021, we collected lesion tissues from patients with oral leukoplakia (OLK) and oral mucosal squamous cell carcinoma (OSCC) from the Department of Oral Mucosa of our hospital. For high-throughput sequencing of methylated RNA co-immunoprecipitation, three samples from each of the LK group and the SCC group were selected.