title: Expression of the HER family mRNA in breast cancer tissue and association with cell cycle inhibitors p21(waf1) and p27(kip1).
abstract: BACKGROUND
  The HER family of the receptor tyrosine kinases epidermal growth factor receptor (EGFR), HER2, HER3 and HER4 are involved in the pathogenesis of many human malignancies. Although there is extensive literature on the expression of single HER-2 and EGFR receptors in breast cancer, little is known concerning the simultaneous expression at the mRNA level of these four receptors in human breast tissue and their influence in downstream signaling pathways that control cell cycle and proliferation.
  
  
  METHODS
  The mRNA expression pattern of the four HER-receptors has been investigated and correlated with the expression of the cyclin-dependent kinase (CDK) inhibitors p21(Waf1) and p27(Kip1) in 67 breast cancer specimens.
  
  
  RESULTS
  A positive correlation between HER-3 and HER-4 mRNA levels and a negative correlation between HER-2 and HER-3 was found. Compared to normal breast tissue, all four receptors were overexpressed in breast tumors and the strongest overexpression was found for HER-3 (p = 0.001). HER-4 expression was inversely related to histopathological grading (HPG), suggesting that elevated HER-4 mRNA expressions could be a biological marker of a more differentiated phenotype. The expression of p21(Waf1) protein was higher in HER-2-negative tumors, compared to HER-2-positive breast carcinomas. Compared to normal breast tissue, p21delta, the 19 kDa degraded form of p21 protein, was markedly expressed in breast cancer (p < 0.001). Conversely, p27(Kip1) was positively associated with HER-2 receptor and inversely associated with HER-3.
  
  
  CONCLUSIONS
  The HER family members are overexpressed in breast cancer. Complex patterns of HER family expression were observed and the effect on cell cycle regulation was dependent on that pattern.
authors.affiliation: Department of Biology and Genetics, Medical Faculty, Aristotle University of Thessaloniki, Thessaloniki GR 54124, Greece.
authors.forename: Theodora G
authors.initials: TG
authors.lastname: Kalemi
authors.forename: Konstantinos T
authors.initials: KT
authors.lastname: Papazisis
authors.forename: Alexandros F
authors.initials: AF
authors.lastname: Lambropoulos
authors.forename: Soultana
authors.initials: S
authors.lastname: Voyatzi
authors.forename: Alexandros
authors.initials: A
authors.lastname: Kotsis
authors.forename: Alexandros H
authors.initials: AH
authors.lastname: Kortsaris
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000201:enzymology / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000096:biosynthesis*; D050760:Cyclin-Dependent Kinase Inhibitor p27; D005260:Female; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D008875:Middle Aged; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000235:genetics; D020794:Receptor Protein-Tyrosine Kinases / Q000096:biosynthesis / Q000235:genetics*
chemical_list: C493956:CDKN1A protein, human; C436291:CDKN1B protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D047908:Intracellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D050760:Cyclin-Dependent Kinase Inhibitor p27; D020794:Receptor Protein-Tyrosine Kinases