METTL3 facilitates tumor progression via an m 6 A-IGF2BP2-dependent mechanism in colorectal carcinoma

Mol Cancer. 2019 Jun 24;18(1):112. doi: 10.1186/s12943-019-1038-7.

Abstract

Background: Colorectal carcinoma (CRC) is one of the most common malignant tumors, and its main cause of death is tumor metastasis. RNA N6-methyladenosine (m6A) 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 m6A "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 m6A-IGF2BP2-dependent mechanism in CRC cells, and indicated a potential biomarker panel for prognostic prediction in CRC.

Keywords: Colorectal cancer; IGF2BP2; METTL3; N6-methyladenosine (m6A); SOX2.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine / analogs & derivatives*
  • Adenosine / metabolism
  • Animals
  • Cell Line, Tumor
  • Cell Proliferation
  • Colorectal Neoplasms / genetics
  • Colorectal Neoplasms / metabolism
  • Colorectal Neoplasms / pathology*
  • Gene Expression Profiling
  • Gene Expression Regulation, Neoplastic
  • HCT116 Cells
  • Humans
  • Methyltransferases / genetics*
  • Methyltransferases / metabolism*
  • Mice
  • Neoplasm Transplantation
  • Prognosis
  • RNA-Binding Proteins / genetics*
  • SOXB1 Transcription Factors / genetics*
  • Sequence Analysis, RNA
  • Signal Transduction
  • Up-Regulation

Substances

  • IGF2BP2 protein, human
  • RNA-Binding Proteins
  • SOX2 protein, human
  • SOXB1 Transcription Factors
  • N-methyladenosine
  • Methyltransferases
  • METTL3 protein, human
  • Adenosine