METTL3 and hepatocellular carcinoma: Interestingly, although METTL3 and METTL14 seem to play completely opposite roles in HCC progression, which may not be the case in other tumors, such as downregulated METTL3 expression detected in approximately 70% of endometrial cancers, which may be related to tumor heterogeneity (Liu et al., 2018a).