In addition, we showed in 15-week-old mice exposed solely to in utero SHS that Dnmt3a, which (1) is responsible for de novo DNA methylation, (2) plays a key role in epigenetic mechanisms, and (3) whose deficiency in mice is associated with lung cancer, was significantly down-regulated (Noël et al., 2017). This evidence concerns the gene DNMT3A and lung cancer.