title: p53 overexpression is different in Epstein-Barr virus-associated and Epstein-Barr virus-negative carcinoma.
abstract: OBJECTIVE
  Epstein-Barr virus (EBV) is associated with a subset of gastric and head and neck carcinomas. While p53 mutation and overexpression is common in gastric cancer, in nasopharyngeal carcinoma p53 is overexpressed yet mutation is uncommon, leading to a proposed viral mechanism of p53 upregulation. We examined the expression of p53 protein in 18 EBV-associated gastric carcinomas (EBV-GA) and compared it with 29 age and sex matched EBV-negative gastric carcinomas (EBV0-GA) and 23 non-nasopharyngeal EBV-associated carcinomas (EBV-CAs) arising from various head and neck regions.
  
  
  RESULTS
  Using two monoclonal antibodies (DO7 and PAb1801) with microwave pre-treatment, the p53 protein was scored according to the intensity and percentage of positive cells. The EBV0-GA showed a clear cut bimodal distribution of p53 levels, with either homogeneous intense staining of most tumour nuclei, or only very weak expression in a few cells. Nearly all the EBV-GA and EBV-CAs showed a weak to moderate p53 expression, characterized by heterogeneous intensity of staining in a variable proportion of tumour cells.
  
  
  CONCLUSIONS
  The difference in p53 levels in the EBV0-GA and EBV-GA is statistically significant. The heterogeneous level of p53 in the EBV-GA and EBV-CAs and its difference from the EBV0-GA is suggestive of a non-mutational mechanism of p53 upregulation and underscores the role of the virus in the oncogenic pathway.
authors.affiliation: Department of Pathology, University of Hong Kong, Queen Mary Hospital, Hong Kong.
authors.forename: S Y
authors.initials: SY
authors.lastname: Leung
authors.forename: K Y
authors.initials: KY
authors.lastname: Chau
authors.forename: S T
authors.initials: ST
authors.lastname: Yuen
authors.forename: K M
authors.initials: KM
authors.lastname: Chu
authors.forename: F J
authors.initials: FJ
authors.lastname: Branicki
authors.forename: L P
authors.initials: LP
authors.lastname: Chung
mesh_terms: D002277:Carcinoma / Q000378:metabolism* / Q000821:virology*; D005260:Female; D006258:Head and Neck Neoplasms / Q000378:metabolism* / Q000821:virology; D004854:Herpesvirus 4, Human / Q000302:isolation & purification*; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008297:Male; D008875:Middle Aged; D013274:Stomach Neoplasms / Q000378:metabolism* / Q000821:virology; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: D016159:Tumor Suppressor Protein p53