METTL3 facilitates tumor progression via an m6A-IGF2BP2-dependent mechanism in colorectal carcinoma

Abstract

Background Colorectal carcinoma (CRC) is one of the most common malignant tumors, and its main cause of death is tumor metastasis. RNA N 6 -methyladenosine (m 6 A) is an emerging regulatory mechanism for gene expression and methyltransferase-like 3 (METTL3) participates in tumor progression in several cancer types. However, its role in CRC remains unexplored. Methods Western blot, quantitative real-time PCR (RT-qPCR) and immunohistochemical (IHC) were used to detect METTL3 expression in cell lines and patient tissues. Methylated RNA immunoprecipitation sequencing (MeRIP-seq) and transcriptomic RNA sequencing (RNA-seq) were used to screen the target genes of METTL3. The biological functions of METTL3 were investigated in vitro and in vivo. RNA pull-down and RNA immunoprecipitation assays were conducted to explore the specific binding of target genes. RNA stability assay was used to detect the half-lives of the downstream genes of METTL3. Results Using TCGA database, higher METTL3 expression was found in CRC metastatic tissues and was associated with a poor prognosis. MeRIP-seq revealed that SRY (sex determining region Y)-box 2 (SOX2) was the downstream gene of METTL3. METTL3 knockdown in CRC cells drastically inhibited cell self-renewal, stem cell frequency and migration in vitro and suppressed CRC tumorigenesis and metastasis in both cell-based models and PDX models. Mechanistically, methylated SOX2 transcripts, specifically the coding sequence (CDS) regions, were subsequently recognized by the specific m 6 A “reader”, insulin-like growth factor 2 mRNA binding protein 2 (IGF2BP2), to prevent SOX2 mRNA degradation. Further, SOX2 expression positively correlated with METTL3 and IGF2BP2 in CRC tissues. The combined IHC panel, including “writer”, “reader”, and “target”, exhibited a better prognostic value for CRC patients than any of these components individually. Conclusions Overall, our study revealed that METTL3, acting as an oncogene, maintained SOX2 expression through an m 6 A-IGF2BP2-dependent mechanism in CRC cells, and indicated a potential biomarker panel for prognostic prediction in CRC. Electronic supplementary material The online version of this article (10.1186/s12943-019-1038-7) contains supplementary material, which is available to authorized users.

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

“…In this study, we gradually confirmed that METTL3, a critical m6A methyltransferase, played an oncogenic role in CRC . Moreover, our study and GEO database predicted that up‐regulated expression of METTL3 in CRC tissues was positively associated with overall survival and PFS in patients, which brought light to its potential prognostic value for CRC.…”

“…In this study, we gradually confirmed that METTL3, a critical m6A methyltransferase, played an oncogenic role in CRC. 37 Moreover, our study and GEO database predicted that up-regulated expres- as the downstream target of METTL3 in promoting CRC proliferation. One of the main characteristics of malignant tumours is abnormal cell growth.…”

“…34 In CRC, a recent research has verified that METTL3 could promote cell self-renewal, stem cell frequency and migration through an m6A-IGF2BP2-dependent mechanism. 37 However, another study showed that METTL3 could suppress colorectal cancer proliferation and migration through p38/ERK pathways. 38 Therefore, the role of METTL3 in CRC might be controversial and need to be further explored.…”

METTL14 suppresses proliferation and metastasis of colorectal cancer by down-regulating oncogenic long non-coding RNA XIST

“…Moreover, although TCGA data showed that abnormal expression of METTL3 may exist in CRC, our knowledge about the link between METTL3 and CRC is still limited. A recent study reported that METTL3 could promote self-renewal of CRC cells through inducing m6A and subsequent upregulation of SOX2 [32]. Similarly, METTL3 and METTL14 also showed opposite effects in the regulation of HCC as above mentioned [11,12].…”

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

“…METTL3 expression was consistently elevated in recurrent colorectal cancer, matched lymph node, and metastatic liver tissues. Colorectal cancer patients with high METTL3 expression had reduced OS and DFS times (37,38). Knockdown of METTL3 in colorectal cancer cells significantly inhibited tumorigenesis and metastasis, cell self-renewal, and the frequency and migration of stem cells in vitro and in vivo (34), suggesting the oncogenic role of METTL3 in colorectal cancer.…”