As shown in Table 1, METTL1, METTL3, METTL4, METTL5, METTL6 and METTL13 were associated with poor prognosis in various tumors including liver hepatocellular carcinoma (LIHC) [159, 160], breast invasive carcinoma (BRCA) [161–163], and lung adenocarcinoma (LUAD) [164]. Here, METTL4 is linked to invasive breast carcinoma.