METTL3/YTHDF2 m⁶A axis promotes tumorigenesis by degrading SETD7 and KLF4 mRNAs in bladder cancer

Abstract

| INTRODUC TI ONBladder cancer (BCa) is the most common malignant tumour of the urinary tract and the 10th most common type of carcinoma worldwide. Approximately 549 000 new cases and 200 000 deaths were estimated by GLOBOCAN in 2018. 1 In 2019, approximately 80 470 patients (including 61 700 men) were diagnosed with BCa and 17 670 patients (including 12 870 men) died from BCa in the United States; thus, BCa ranks the forth in incidence and eighth in mortality in men. 2 The increasing trend in these numbers constantly urges researchers to better understand the mechanisms underlying the pathogenesis of BCa to identify potential therapies against BCa. m 6 A, a modification first identified in mRNA-enriched RNA fractions in 1974, 3 refers to methylation of the N6 position of adenosine bases, which are widely distributed in the mammalian mRNA. 4,5 With the application of available methods for detecting m 6 A, insights into the regulatory mechanism have been revealed in recent years. m 6 A RNA modification is a dynamic and reversible posttranscriptional modification process maintained by a multicomponent Abstract N6-Methyladenosine (m 6 A) modification, the most prevalent modification of eukaryotic messenger RNA (mRNA), is involved in the progression of various tumours.However, the specific role of m 6 A in bladder cancer (BCa) is still poorly understood.In this study, we demonstrated the tumour-promoting function and specific regulatory mechanism of m 6 A axis, consisting of the core 'writer' protein METTL3 and the major reader protein YTHDF2. Depletion of METTL3 impaired cancer proliferation and cancer metastasis in vitro and in vivo. Through transcriptome sequencing, m 6 A methylated RNA immunoprecipitation (MeRIP) and RIP, we determined that the METTL3/YTHDF2 m 6 A axis directly degraded the mRNAs of the tumour suppressors SETD7 and KLF4, contributing to the progression of BCa. In addition, overexpression of SETD7 and KLF4 revealed a phenotype consistent with that induced by depletion of the m 6 A axis. Thus, our findings on the METTL3/YTHDF2/SETD7/KLF4 m 6 A axis provide the insight into the underlying mechanism of carcinogenesis and highlight potential therapeutic targets for BCa. K E Y W O R D Sbladder cancer, carcinogenesis, METTL3/YTHDF2 m 6 A axis, mRNA degradation, RNA modification | 4093 XIE Et al.

Roles of METTL3 in cancer: mechanisms and therapeutic targeting

“…Two groups found that METTL3 was upregulated in BCa patient samples and further demonstrated that METTL3-mediated m 6 A modification in target transcripts, such as CDCP1 and ITGA6 , promoted mRNA translation via YTHDF1/3 binding [ 86 , 87 ]. Other mRNA transcripts, including AFF4 , IKBKB , RELA , and MYC , were revealed to be targets of METTL3 and mediated the role of METTL3 in promoting cell proliferation, invasion, and survival [ 85 ], whereas SETD7 and KLF4 tumor suppressors were negatively regulated by METTL3 in a YTHDF2-dependent manner [ 88 ]. Recently, a study by Han et al showed that METTL3-mediated m 6 A modification in pri-miR221/222 facilitates miRNA maturation, resulting in the reduction of PTEN , which ultimately leads to BCa cell proliferation [ 84 ].…”

Role of methyltransferase-like enzyme 3 and methyltransferase-like enzyme 14 in urological cancers

“…METTL3 also catalyzes m6A modifications in the mRNAs of SETD7 and KLF4, two tumor suppressors that are part of the METTL3/YTHDF2-SETD7/KLF4 m6A axis. YTHDF2 recognizes these m6A modifications and degrades the SETD7 and KLF4 mRNAs, leading to bladder cancer progression (Xie et al, 2020).…”

The Potential Roles of RNA N6-Methyladenosine in Urological Tumors

“…Increased m 6 A methylation enhanced the translation of ITGA6 mRNA by binding of YTHDF1 and YTHDF3 and promoted malignant phenotypes in BCa. Xie and coworkers found that knockout of METTL3 impaired tumor growth and metastasis, METTL3/YTHDF2 m 6 A axis could directly degrad the mRNA expression of the tumor suppressors SETD7 and KLF4, leading to the development and progression of BCa (Xie et al, 2020). Gu et al (2019) found a decrease of N6-methyladenosine in BCa and bladder tumor initiating cells (TICs).…”