title: Analysis of EGFR, HER2, and TOP2A gene status and chromosomal polysomy in gastric adenocarcinoma from Chinese patients.
abstract: BACKGROUND
  The EGFR and HER2 genes are located on chromosomes 7 and 17, respectively. They are therapeutic targets in some tumors. The TOP2A gene, which is located near HER2 on chromosome 17, is the target of many chemotherapeutic agents, and co-amplification of HER2 and TOP2A has been described in several tumor types. Herein, we investigated the gene status of EGFR, HER2, and TOP2A in Chinese gastric carcinoma patients. We determined the rate of polysomy for chromosomes 7 and 17, and we attempted to clarify the relationship between EGFR, HER2, and TOP2A gene copy number and increased expression of their encoded proteins. Furthermore, we tried to address the relationship between alterations in EGFR, HER2, and TOP2A and chromosome polysomy.
  
  
  METHODS
  One hundred cases of formalin fixed and paraffin embedded tumor tissues from Chinese gastric carcinoma patients were investigated by immunohistochemistry and fluorescence in situ hybridization (FISH) methods.
  
  
  RESULTS
  Forty-two percent of the cases showed EGFR overexpression; 16% showed EGFR FISH positive; 6% showed HER2 overexpression; and 11% showed HER2 gene amplification, including all six HER2 overexpression cases. TOP2A nuclear staining (nuclear index, NI) was determined in all 100 tumors: NI values ranged from 0.5-90%. Three percent of the tumors showed TOP2A gene amplification, which were all accompanied by HER2 gene amplification. Nineteen percent of the tumors showed chromosome 7 polysomy, and 16% showed chromosome 17 polysomy. Chromosome 7 polysomy correlated significantly with EGFR FISH-positivity, but was not associated with EGFR overexpression. HER2 overexpression associated significantly with HER2 gene amplification. TOP2A gene amplification was significantly associated with HER2 gene amplification. No relationship was found between alterations in the EGFR, HER2, and TOP2A genes and clinicopathologic variables of gastric carcinoma.
  
  
  CONCLUSIONS
  The data from our study suggest that chromosome 7 polysomy may be responsible for increased EGFR gene copy number in gastric carcinomas, and that HER2 gene amplification may be the major reason for HER2 protein overexpression. A combined investigation of the gene status of EGFR, HER2, and TOP2A should facilitate the identification of a target therapeutic regimen for gastric carcinoma patients.
authors.affiliation: Department of Pathology, Peking Union Medical College Hospital, Chinese Academy of Medical Science, Beijing 100730, PR China. liangzhiyong1220@yahoo.com
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Liang
authors.forename: Xuan
authors.initials: X
authors.lastname: Zeng
authors.forename: Jie
authors.initials: J
authors.lastname: Gao
authors.forename: Shafei
authors.initials: S
authors.lastname: Wu
authors.forename: Peng
authors.initials: P
authors.lastname: Wang
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Shi
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Tonghua
authors.initials: T
authors.lastname: Liu
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics* / Q000473:pathology; D000782:Aneuploidy; D000951:Antigens, Neoplasm / Q000235:genetics / Q000378:metabolism*; D002681:China; D002886:Chromosomes, Human, Pair 17; D002897:Chromosomes, Human, Pair 7; D004250:DNA Topoisomerases, Type II / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D005260:Female; D018628:Gene Dosage; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D000075223:Poly-ADP-Ribose Binding Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D013274:Stomach Neoplasms / Q000235:genetics* / Q000473:pathology
chemical_list: D000951:Antigens, Neoplasm; D004250:DNA Topoisomerases, Type II; D004268:DNA-Binding Proteins; D066246:ErbB Receptors; D000075223:Poly-ADP-Ribose Binding Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; C512478:EGFR protein, human; C508053:ERBB2 protein, human; C000618811:TOP2A protein, human