Roles and mechanisms of m6A modification regulating RP11-426A6.5 in laryngeal squamous cell carcinoma

Abstract

Objective: To investigate the roles of N6-methyladenosine (m6A) modification in regulating RP11-426A6.5 in the development of laryngeal squamous cell carcinoma (LSCC). Methods: The methylation and expression levels of lncRNAs were identified and important lncRNAs were screened utilizing long non-coding RNA (lncRNA) m6A methylation microarray. Cancer and para cancer tissue samples were taken from 48 LSCC patients hospitalized to the Department of Otolaryngology-Head and Neck Surgery of the Second Affiliated Hospital of Harbin Medical University between January and September 2017. Expression profiling microarray was performed in 3 of 48 LSCC samples, and methylated RNA immunoprecipitation-quantitative PCR (MeRIP-qPCR) and quantitative real-time fluorescent PCR (qRT-PCR) were performed in the remaining 45 LSCC samples to verify the m6A modification and expression levels of RP11-426A6.5. Correlations between RP11-426A6.5 and clinical factors were anlysed. Laryngeal cancer cell line with low expression of RP11-426A6.5 was created in vitro using RNA interference (RNAi) technology. The 5-Ethynyl-2'-deoxyuridine (EdU) cell proliferation experiment, wound healing experiment, and transwell invasion experiment were used respectively to measure the proliferation, migration, and invasion of LSCC cells. The effect of RP11-426A6.5 down-regulation on the growth of transplanted tumors in vivo was verified by nude mice tumorigenesis assay. The Cancer Genome Atlas (TCGA) database and sequence-based RNA adenosine methylation site predictor (SRAMP) website were used to predict the enzymes and corresponding methylation sites. MazF digestion was chosen to validate the binding sites. RNAi technology was used to observe the changes in cell function after interfering with the expression of the corresponding genes of the modified enzymes. MeRIP-qPCR was used to detect the level of RP11-426A6.5 m6A cell line treated with actinomycin D was used to observe the stability of RP11-426A6.5. Results: RP11-426A6.5 methylation and expression levels were significantly higher in LSCC tissues than those in paracancerous tissues (methylation levels: 23.828±4.975 vs 20.280±3.607; expression levels: 1.197±0.314 vs 1.015±0.170, all P values<0.05). RP11-426A6.5 expression levels were closely correlated with T stage (T1-2: 1.081±0.298 vs T3-4: 1.306±0.292, χ2=5.35, P<0.05). The postoperative survival of patients with high RP11-426A6.5 expressions was significantly lower than that of patients with low RP11-426A6.5 expression (P=0.046). Assays in vitro and in vivo showed that the downregulation of RP11-426A6.5 significantly decreased the proliferation, migration, and invasion abilities of LSCC cells and the growth of transplanted tumors. The binding of methyltransferase-like 3 (METTL3), an m6A-modified enzyme, to the corresponding methylation site of RP11-426A6.5 enhanced its stability and mediated its regulation of malignant behaviors of LSCC cells. Conclusions: RP11-426A6.5 can regulate the malignant behaviors of LSCC cells, which is mediated by the m6A modification process involving in the methyltransferase METTL3.