Expression Of E-Cadherin (E-CD) And CpG Island Hypermethylation Around Promoter Region Of Its Gene In Gastric Carcinomas

Objectives: 1). To study the relationship between differentiation of tumors, depth of tumor infiltration, metastasis of lymph node and expression of E-CD in gastric carcinomas 2). To investigate the correlation between histological features, metastasis of gastric carcinoma and status of CpG island hypermethylation around the promoter region of E-CD. 3). To explore the relationship between downregulation of E-CD and hypermethylation of its promoter. Methods: Immunohistochemical staining of E-CD was detected in 98 formalin-fixed, paraffin-embedded tissues from 49 patients with primary gastric carcinoma, including 49 adjacent normal tissues. Meanwhile, Methylation specific polymerase chain reaction (MSP) combined with restriction enzyme analysis and DNA sequencing were applied to evaluate the status of CpG hypermethylation in same number of fresh specimens. Results I (S-P): 1). E-CD was expressed on the membrane of cell, 32 of 49 tumors showed negative expression of E-CD and corresponding adjacent normal tissues had positive expression. 2). 16 out of 19(84.2%) poorly differentiated carcinomas (including 3 signet-ring cell cancers) had negative expression of E-CD, while there was negative expression in 16 cases of high-4-differentiation carcinomas. 3). There was negative expression of E-CD in 29 out of the 39 patients with Borrmann's III IV, while only 3 with Borrmann's I II were expressed negatively. 4). Of the 27 cases with lymph-node metastasis, 21 cases had negative E-CD expression, while 50% cases without lymph-node metastasis expressed positively. Results n (MSP) 1). There was no evidence of CpG island hypermethylation in adjacent normal tissues. 2). CpG island hypermethylation in high differentiation carcinomas occurred in 24 of 49 tumor tissues, the rate of hypermethylation in poorly differentiated carcinomas being 73.7%. 3). Hypermethylation was found in 20 of 49 cases with Borrmann's III IV. There was no significant difference between Borrmann's III IV and Borrmann's I II due to small number of early cases. 4). The rate of hypermethylation with lymph-node metastasis (74.7%) was higher than that without lymph-node metastasis (p=0.0014). Conclusions I :1). Although E-CD expressed negatively in only 3 out of 10 early carcinomas, which demonstrates that low expression of E-CD in tumors might be an early event different from that of normal tissues. 2). Negative E-CD in poorly differentiated gastric carcinomas is significantly higher than that in high differentiation, and may act as a valuable marker in cellular dedifferentiation. 3). Positive E-CD in the group with lymph-node metastasis is lower than that without lymph-node metastasis, which indicates that E-CD is linked with the lymph-node metastasis. E-CD plays an important role in carcinogenesis and metastasis and may be considered as a prognostic indicator in potential metastasis of gastric carcinomas. Conclusions n 1). CpG island hypermethylation was detected in 24 of 49 gastric carcinomas, while there was no hypermethylation detection in corresponding adjacent normal tissues, indicating that hypermethylation of upstream sequence of this gene might be an important marker different from normal tissue in the development of carcinogenesis. 2). Higher rate of hypermethylation occurred in poorly differentiated gastric carcinomas,-5-which indicates hpermethylation of E-CD gene in correlation with differentiation of tumors. 3). The status of CpG island hypermethylation significantly correlated with lymph-node metastasis, which is a risk factor. It is suggested that hypermethylation of E-CD may play an important role in development of malignancies. 4). Downregulation of E-CD expression was found to be related to promoter hypermethylation. We conclude that aberrant hypermethylation may be an important mechanism for the inactivation of this gene.