Epigenetic regulation of Wnt/β-catenin signal-associated genes in gastric neoplasia of the fundic gland (chief cell-predominant) type.

Gastric neoplasia of the fundic gland (chief cell-predominant) type (GNCCP) is a rare variant of gastric tumor. This tumor is associated with activation of the Wnt/β-catenin signaling pathway; however, the mechanisms underlying this activation remain unknown. To elucidate potential roles of Wnt/β-catenin signal-associated gene methylation in GNCCP, we performed β-catenin immunostaining and methylation-specific polymerase chain reaction (PCR) for their associated genes, including SFRPs, APC, AXIN2, and MCC, in 26 GNCCPs [i.e., 11 intramucosal (GNCCP-Ms) and 15 submucosal tumors (GNCCP-SMs)], and compared with 27 fundic gland polyps (FGPs), 12 FGPs with dysplasia (FGP-Ds), 27 conventional gastric adenocarcinomas (CGAs). Nuclear β-catenin labeling indices were higher in GNCCPs and CGAs than in FGPs and FGP-Ds. SFRPs, APC, and AXIN2 were more frequently methylated in GNCCPs and CGAs (SFRP1, 88%/96%; SFRP2, 85%/93%; SFRP4, 73%/81%; APC, 81%/81%; AXIN2, 81%/85%; respectively) than in FGPs and FGP-Ds (37%/50%; 41%/42%; 41%/58%; 37%/33%; 41%/50%; respectively). A significant correlation was seen between nuclear β-catenin expression and methylation of SFRP1 in GNCCPs. Furthermore, nuclear β-catenin expression was significantly frequent in high-methylated GNCCPs than in low-methylated tumors. In conclusion, our results suggest that activation of this pathway, mediated by gene methylation, may be associated with progression of some GNCCP cases, similar to CGAs.