METTL9 and hepatocellular carcinoma: Further analysis of the TCGA-LIHC data showed that METTL9 expression was significantly higher in pathological TNM stages III & IV compared to stages I & II, in T3 & T4 stages compared to T1 & T2 stages, and in G3 & G4 tissue grades compared to G1 & G2 tissue grades respectively (Fig. 1F–H), which indicated that the expression level of METTL9 increased with the advanced stage and the higher malignancy of HCC.