SMAD7 and lung cancer: In the light that two de novo DNA methyltransferases DNMT3A and DNMT3B play distinct roles in lung cancer, as DNMT3B was implicated in promoting lung cancer by silencing tumor-suppressor genes, whereas DNMT3A suppressed KRASG12D-mediated lung cancer progression24–26, we further investigated whether the oncogenic DNMT3B was involved in catalyzing de novo DNA hypermethylation of SMAD7 gene.