M6A mediated upregulation of lncRNA CASC9 in head and neck squamous cell carcinoma.

Abstract

e15165 Background: Long noncoding RNAs (lncRNAs) are dysregulated in many cancers including head and neck squamous cell carcinoma (HNSCC). Many recent studies have shown that abnormal expression of lncRNA CASC9 (CASC9) is involved in the pathophysiological processes of cancers. N6-methyladenosine (m6A) represents the most common methylation modification of lncRNAs and has been shown to play important roles in the development of different cancer types. However, the potential role of m6A mediated upregulation of CASC9 in HNSCC and its molecular mechanisms remain largely unknown. In the present study, we identified the molecular mechanisms of CASC9 in promoting the malignancy of HNSCC. Methods: We used real-time polymerase chain reaction (qPCR) to identify the level of CASC9 expression in HNSCC clinical samples and cell lines. The oncogenic role of CASC9 in HNSCC was analyzed using online tool UALCAN. RNA immunoprecipitation sequencing (MeRIP-seq) was performed to determine the m6A modification of CASC9. The relationship between CASC9 expression and patients prognosis was analysed using Kaplan-Meier plotter. Loss of function studies used to evaluate cell proliferation, viability, and migration of HNSCC cell lines. Results: Results revealed that m6A mediated CASC9 expression was significantly upregulated in HNSCC tissues than those in the paired adjacent non-tumor tissues. Similarly, m6A mediated CASC9 was significantly overexpressed in the HNSCC cell lines compared with normal cells. The upregulated CASC9 expression was significantly associated with advanced stages and closely correlated to the unfavorable prognosis. m6A was highly enriched within CASC9 and enhanced its RNA stability. Knockdown of CASC9 remarkably inhibited the proliferation, migration and promoted the apoptosis of HNSCC cells. Mechanistically, we found that IGF2BP2 (insulin-like growth factor 2 mRNA binding protein 2), m6A reader could recognize the m6A site in CASC9 and enhance its stability. Conclusions: Overall, this work highlights for the first time that m6A modification enhance CASC9 stability may serve as a potential prognostic biomarker and therapeutic target in HNSCC.