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. This evidence concerns the gene DNMT3B and lung cancer.