METTL1 and neoplasm: As the m7G methyltransferase of miRNAs, METTL1 exhibited hyperactivity in lung and bladder cancer, positively correlating with advanced clinical stages and high tumor grades (Pandolfini et al., 2019; Ying et al., 2021), while in colon cancer, it is significantly downregulated, actively participating in multiple tumor progression-related processes through its involvement in mediating miRNA maturation or in an m7G-tRNA codon-dependent manner (Ma et al., 2021b; Chen and Liu, 2021).