METTL3 promote tumor proliferation of bladder cancer by accelerating pri-miR221/222 maturation in m6A-dependent manner

Abstract

Background METTL3 is known to be involved in all stages in the life cycle of RNA. It affects the tumor formation by the regulation the m6A modification in the mRNAs of critical oncogenes or tumor suppressors. In bladder cancer, METTL3 could promote the bladder cancer progression via AFF4/NF-κB/MYC signaling network by an m6A dependent manner. Recently, METTL3 was also found to affect the m6A modification in non-coding RNAs including miRNAs, lincRNAs and circRNAs. However, whether this mechanism is related to the proliferation of tumors induced by METTL3 is not reported yet. Methods Quantitative real-time PCR, western blot and immunohistochemistry were used to detect the expression of METTL3 in bladder cancer. The survival analysis was adopted to explore the association between METTL3 expression and the prognosis of bladder cancer. Bladder cancer cells were stably transfected with lentivirus and cell proliferation and cell cycle, as well as tumorigenesis in nude mice were performed to assess the effect of METTL3 in bladder cancer. RNA immunoprecipitation (RIP), co-immunoprecipitations and RNA m6A dot blot assays were conducted to confirm that METTL3 interacted with the microprocessor protein DGCR8 and modulated the pri-miR221/222 process in an m6A-dependent manner. Luciferase reporter assay was employed to identify the direct binding sites of miR221/222 with PTEN. Colony formation assay and CCK8 assays were conducted to confirm the function of miR-221/222 in METTL3-induced cell growth in bladder cancer. Results We confirmed the oncogenic role of METTL3 in bladder cancer by accelerating the maturation of pri-miR221/222, resulting in the reduction of PTEN, which ultimately leads to the proliferation of bladder cancer. Moreover, we found that METTL3 was significantly increased in bladder cancer and correlated with poor prognosis of bladder cancer patients. Conclusions Our findings suggested that METTL3 may have an oncogenic role in bladder cancer through interacting with the microprocessor protein DGCR8 and positively modulating the pri-miR221/222 process in an m6A-dependent manner. To our knowledge, this is the first comprehensive study that METTL3 affected the tumor formation by the regulation the m6A modification in non-coding RNAs, which might provide fresh insights into bladder cancer therapy. Electronic supplementary material The online version of this article (10.1186/s12943-019-1036-9) contains supplementary material, which is available to authorized users.

Multiple Functions and Mechanisms Underlying the Role of METTL3 in Human Cancers

“…Recent studies noted that METTL3 was drastically upregulated in bladder cancer tissues and was related to tumor histological grade. Patients with high expression of METTL3 had poor prognosis and reduced survival time (28)(29)(30). Knockdown of METTL3 significantly reduced bladder cancer cell invasion, proliferation, and survival in vitro and tumorigenicity in vivo (31).…”

“…Alarcon et al found that METTL3 promotes the maturation of miRNAs by interacting with the microprocessor protein DGCR8 (2,20). Han et al found that METTL3 positively modulates pri-miR221/222 processing in an m 6 A-dependent manner by interacting with DGCR8, resulting in a reduction in the PTEN level, which ultimately results in proliferation of bladder cancer (29). Wang et al explored the function and mechanism of METTL3 and m 6 A in colistin-induced kidney injury and found that METTL3 interacts with DGCR8 and positively modulates the processing of mature miR-873-5p in an m 6 A-dependent manner (54).…”

N6-Methyladenosine: A Novel RNA Imprint in Human Cancer

“…Scientists have also reported in bladder cancer that METTL3 accelerates the processing of pri-miR221/222 via recognition by DGCR8 (46). Subsequently, mature miR221/222 restrains the expression of the antioncogene PTEN and ultimately boosts tumor growth both in vitro and in vivo.…”

Methyltransferase like 3 promotes colorectal cancer proliferation by stabilizing CCNE1 mRNA in an m6A‐dependent manner

“…As the critical m6A methyltransferase, the role of METTL3 in tumours is controversial. Some studies reported that METTL3 played an oncogenic role in myeloid leukaemia, liver cancer, breast cancer, glioblastoma, bladder cancer and lung cancer . Other studies indicated that METTL3 played a tumour suppressor in renal cell carcinoma and glioblastoma .…”

“…[3][4][5] mRNA modifications represent another layer of epigenetic regulation of gene expression, which has been termed 'RNA epigenetics' or 'epitranscriptomics'. Among these, m6A modification is the most prevalent one in eukaryotes, 6 which occurs in mammalian mRNAs, 7,8 long noncoding RNAs, 9 micro RNAs, 10,11 involving in many RNA functions such as mRNA stability, 7 splicing, 12 transport, 13 localization and translation, 8,14 primary microRNA processing 10 and RNA-protein interactions. 15 The levels of m6A modification in mRNAs were usually controlled by so-called 'reader', 'writer' and 'eraser'.…”