SFRP1 and gastric cancer: Fourth, and most importantly, only SFRP2, but not SFRP1 silencing by promoter methylation was observed in oral SSC [45] and gastric cancer [46], and promoter methylation is significantly higher in SFRP2 than SFRP1 in cervical cancer [47], as well as in cervical adenocarcinoma [46], [48].