RNA N6-Methyladenosine Methyltransferase METTL3 Facilitates Colorectal Cancer by Activating the m6A-GLUT1-mTORC1 Axis and Is a Therapeutic Target

Abstract

Background & aims: RNA N⁶-methyladenosine (m⁶A) modification has recently emerged as a new regulatory mechanism in cancer progression. We aimed to explore the role of the m⁶A regulatory enzyme METTL3 in colorectal cancer (CRC) pathogenesis and its potential as a therapeutic target.

Methods: The expression and clinical implication of METTL3 were investigated in multiple human CRC cohorts. The underlying mechanisms of METTL3 in CRC were investigated by integrative m⁶A sequencing, RNA sequencing, and ribosome profiling analyses. The efficacy of targeting METTL3 in CRC treatment was elucidated in CRC cell lines, patient-derived CRC organoids, and Mettl3-knockout mouse models.

Results: Using targeted clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 dropout screening, we identified METTL3 as the top essential m⁶A regulatory enzyme in CRC. METTL3 was overexpressed in 62.2% (79/127) and 88.0% (44/50) of primary CRCs from 2 independent cohorts. High METTL3 expression predicted poor survival in patients with CRC (n = 374, P < .01). Functionally, silencing METTL3 suppressed tumorigenesis in CRC cells, human-derived primary CRC organoids, and Mettl3-knockout mouse models. We discovered the novel functional m⁶A methyltransferase domain of METTL3 in CRC cells by domain-focused CRISPR screening and mutagenesis assays. Mechanistically, METTL3 directly induced the m⁶A-GLUT1-mTORC1 axis as identified by integrated m⁶A sequencing, RNA sequencing, ribosome sequencing, and functional validation. METTL3 induced GLUT1 translation in an m⁶A-dependent manner, which subsequently promoted glucose uptake and lactate production, leading to the activation of mTORC1 signaling and CRC development. Furthermore, inhibition of mTORC1 potentiated the anticancer effect of METTL3 silencing in CRC patient-derived organoids and METTL3 transgenic mouse models.

Conclusions: METTL3 promotes CRC by activating the m⁶A-GLUT1-mTORC1 axis. METTL3 is a promising therapeutic target for the treatment of CRC.

Keywords: Colorectal Cancer; Glucose Metabolism; N(6)-Methyladenosine; mTORC1.