Tennis et al. showed that overexpression of DNMT1 induced methylation of the tumor suppressor Wnt7a in non-small cell lung cancer, rendering it inactive and knocking down DNMT1 by shRNA, and activated it through decreasing its methylation in non-transformed lung epithelial cell lines cultured in 1% cigarette smoke condensate [29]. Here, DNMT1 is linked to non-small cell lung carcinoma.