title: Type 1 protein tyrosine kinases in benign and malignant breast lesions.
abstract: OBJECTIVE
  To determine their significance, we examined the expression pattern of the four epidermal growth factor receptor (EGFR) family members as well as the phosphotyrosine kinase activity in breast tumour tissues.
  
  
  RESULTS
  Fifty-three malignant breast tumours, four breast cancer cell lines, and 10 benign breast tumours were investigated. Fifty-three per cent (28/53) of the malignant tumours expressed EGFR protein, and the majority of these positive tumours were strongly positive. Eighty per cent (8/10) of the benign tumours also expressed EGFR protein, but all in a lower or moderate level. An association between EGFR expression and increasing malignancy grade was found in the group of infiltrating ductal carcinomas. Of the malignant tumours, 35.8% (19/53) expressed c-erbB-2 protein and 17% (9/53) c-erbB-3 protein, while no expression of c-erbB-2 and c-erbB-3 proteins was found in the benign tumours. Contrary to previous reports, we observed c-erbB-4 receptor protein to be less expressed in the malignant breast tumours. The 'normal' breast epithelial cells adjacent to the malignant tumours and the benign tumours demonstrated intensified membrane staining for c-erbB-4, while a number of the malignant tumours demonstrated a weak cytoplasmic staining or were negative. However, several malignant tumours with strong membrane staining for the c-erbB-4 protein were also found. No simple association between the expression of the four receptors and phosphotyrosine kinase activity was found.
  
  
  CONCLUSIONS
  Our study has revealed a complex expression pattern of the EGFR family members in breast tumour cells. While the data about EGFR, c-erbB-2, c-erbB-3 and phosphotyrosine are largely in line with what has been reported, we found the c-erbB-4 protein expression to be decreased in the malignant tumours.
authors.affiliation: Department of Pathology, Norwegian Radium Hospital and Institute for Cancer Research, University of Oslo, Norway.
authors.forename: Z
authors.initials: Z
authors.lastname: Suo
authors.forename: E
authors.initials: E
authors.lastname: Emilsen
authors.forename: K M
authors.initials: KM
authors.lastname: Tveit
authors.forename: J M
authors.initials: JM
authors.lastname: Nesland
mesh_terms: D000328:Adult; D000368:Aged; D001940:Breast / Q000201:enzymology; D001943:Breast Neoplasms / Q000201:enzymology*; D002277:Carcinoma / Q000201:enzymology*; D066246:ErbB Receptors / Q000378:metabolism; D005260:Female; D018226:Fibroadenoma / Q000201:enzymology*; D006801:Humans; D007150:Immunohistochemistry; D008875:Middle Aged; D019000:Phosphotyrosine / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D020893:Receptor, ErbB-3; D066247:Receptor, ErbB-4; D014407:Tumor Cells, Cultured
chemical_list: D066246:ErbB Receptors; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases; D011518:Proto-Oncogene Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; D020893:Receptor, ErbB-3; D066247:Receptor, ErbB-4; C587689:ERBB4 protein, human