To test the possibility that siRNA-DNMT1 demethylated the promoters of RASSF1A and APC, we estimated the status of methylation of two lung cancer cells and found that RASSF1A and APC were demethylated by DNMT1 knockdown for 48h (Figure 3E and 3F), which suggested that loss-of-function of DNMT1 by siRNA could effectively reactivate the tumor suppressive genes RASSF1A and APC via demethylation. This evidence concerns the gene RASSF1 and lung cancer.