Suspecting epigenetic regulation of p21 expression in tumor cells, we performed pyrosequencing and found an increased methylation of CpG in the p21 promoter in forestomach tumor samples of Tgfbr2fspKO (77%) compared to that of Tgfbr2flox/flox mice (29%) (Figure 2C, left panel). Here, CDKN1A is linked to neoplasm.