Clinicopathological Characteristics And Germline E-cadherin Gene (CDH1) Mutations In Familial Gastric Cancer

Objective:(1) To study the clinicopathological characteristics and provide evidence for clinical management or health counseling to the patients of familial gastric cancer as well as the familial members.(2) To explore the alterations of E-cadherin and BRCA2 protein expression in familial and non-familial gastric cancer tissues and analyzed the relation with the hereditary susceptibility of familial gastric cancer.(3) To evaluated the incidence of germline CDH1 gene mutations in Chinese familial gastric cancer and provide evidence for screening,diagnosis and therapy.Materials and Methods:(1) The patients with gastric cancer treated in the Department of Surgery,Cancer Hospital,Fudan University,from January 1996 to December 2007,were analyzed retrospectively.Sex,age,location of the tumor, histological type and family history of malignant tumor were all recorded and analyzed.(2) The E-cadherin and BRCA2 protein expression status in tumor tissue from eighty gastric cancer patients was examined using immunohistochemical technology.The 80 patients included four groups:familial diffuse gastric cancer, familial intestinal gastric cancer,sporadic diffuse gastric cancer and sporadic intestinal gastric cancer,and each group had twenty patients.(3) Thirty-nine peripheral blood samples were recruited from 39 patients with gastric cancer from September 2006 to September 2008.32 cases of patients fulfilled the broad screen criteria recommended by ICG-HGC and 7 cases of patients fulfilled the criteria of early on-set diffused gastric cancer and not fulfilled the criteria of ICG-HGC.Of the 32 cases,24 were diffuse gastric cancer and 8 were intestinal gastric cancer.The genomic DNA was isolated from peripheral blood leukocytes using the TIANamp Blood DNA Kit according to the manufacturer's instructions.All 16 coding regions of the CDH1 gene were amplified by PCR.The products of PCR were purified using TIANgel Midi Purification Kit according to the manufacturer's instructions.The entire coding sequences of the CDH1 gene were screened by denatured high-performance liquid chromatography analysis using a 3500HT WAVE DNA analysis system.The mutation samples were confirmed by DNA direct sequencing. Four samples with a family history of pancreatic cancer,breast cancer or ovarian cancer were screened for germline BRCA2 gene mutation using the methods mentioned above.Results:(1) 4426 patients with gastric cancer were treated between January 1996 to December 2007 in the Department of Surgery,Cancer Hospital,Fudan University. 619 patients had positive family history of malignant tumors,of these patients,323 patients(7.3%) with gastric cancer and 370 patients(8.3%) with malignant tumors beyond stomach in first and/or second degree relatives.156 patients(3.5%) fulfilled the broad screen criteria of hereditary gastric cancer recommended by ICG-HGC.The mean patient age at initial diagnosis in familial gastric cancer was 50.2 year(range 14-91 year;median 58 year),while 57.6 year(range 14-91year,median 57.6 year) in non-familial gastric cancer(P=0.000).The age of the second generation was younger than the first generation(mean age 58.3 vs.49.7,P=0.005).32 patients(20.5%) in familial gastric cancer were diagnosed at early stage,while 528 patients(12.4%) in non-familial gastric cancer(P=0.003).Extra-gastric malignant tumors(21.2%vs. 7.9%,P=0.000),especially in colorectal cancer(7.7%vs.1.3%,P=0.000),hepatic cancer(4.5%vs.1.4%) and leukemia(1.3%vs.0.2%,P=0.046),were more frequent in patients' relatives of familial gastric cancer than in the patients' relatives of non-familial gastric cancer.There is no statistic difference in the tumor location and histological type between familial and non-familial gastric cancer.(2) Negative E-cadherin expression was found in 45 patients(56.3%).There was no statistically significant difference between familial and non-familial gastric cancer(60%vs. 52.5%,P=0.499).Negative BRCA2 protein expression was found in 32 patients(40%).Of the 40 familial gastric cancer,21 patients(52.5%)were negative, while 11 patients(27.5%) in sporadic gastric cancer(P=0.022).Further study found that the difference was caused by familial diffuse gastric cancer,of which 13 patients (65%) were negative.The negative expression of E-cadherin or BRCA2 protein was also found in 6(45.5%) and 4(36.4%) early gastric cancer respectively.(3) Mutational analysis of CDH1 was performed for 39 patients.Two of the 24 patients(8.3%) fulfilled ICG-HCG broad screen criteria and with diffuse gastric cancer were found to have CDH1 germline mutations.No CDH1 germline mutation was found in the 8 patients with familial intestinal gastric cancer and 7 patients with early on-set diffuse gastric cancer.BRCA2 germline mutation was not found in the 4 patients with a family history of pancreatic cancer,breast cancer or ovarian cancer.The two mutations were missense mutation:1795A-T(T599S),928G-A,(E310K).The two mutations were all located at the extracellular domain and maybe influence the cell-to-cell adhesion.Conclusion:(1) Familial gastric cancer accounted for 3.5%patients of all gastric cancer.Age of onset in familial gastric cancer was younger than non-familial gastric cancer and decreased by the generation.Counseling and guidance should be given to the descendants of the patients in familial gastric cancer.Colorectal cancer was the most common cancer of extra-gastric cancer in familial gastric cancer,and than hepatic cancer and leukemia in our country.So for the familial gastric cancer patients' relatives,we should alert on the extra-gastric cancer as well as gastric cancer.Familial gastric cancer can also be detected at early stage by endoscope.(2) Both BRCA2 protein and E-cadherin are related to the gastric cancer development,even at early stage.But our result suggests that only BRCA2 protein may play a role in the susceptibility to familial diffuse gastric cancer.(3) Low frequency of germline E-cadherin(CDH1) gene mutations was found in Chinese familial gastric cancer in our study.Genetic study of familial gastric cancer in our country can't be only restricted in CDH1 gene reported by foreign researchers and other candidate gene should be considered.Further study on familial intestinal gastric cancer should be initiated.Genetic screen depended on cumulative knowledge.