METTL4 and cancer: Previous studies have shown that m6A modification regulators, including m6A writers [METTL3 (Lin et al., 2016) and METTL4 (Gong et al., 2020; Liu et al., 2020; Wang et al., 2021b; Nombela et al., 2021)], m6A erasers [FTO (Liu et al., 2018; Chen and Du, 2019; Tang et al., 2020; Nombela et al., 2021) and ALKBH5 (Jin et al., 2020)], and m6A readers [YTHs (Jin et al., 2020) and IGF2BPs (Degrauwe et al., 2016; Müller et al., 2019)], play important roles in the occurrence and development of various cancers.