title: WAF1/CIP1 protein expression in human breast tumors.
abstract: WAF1/CIP1 is a cyclin-dependent kinase inhibitor which is directly induced by p53 and negatively controls cell proliferation. To test the hypothesis that increased levels of WAF1 would be associated with a lower S-phase fraction and better prognosis, WAF1 protein was assessed by immunohistochemistry (IHC) in 115 node-negative human breast tumors, and results were correlated with established prognostic factors and clinical outcome. Nuclear staining was observed in malignant cells in 43% of tumors. In most (90%) of the positive tumors, the proportion of cells staining for WAF1 was low (< 10%). WAF1 was not detected in the cytoplasm, or in non-malignant epithelium. Contrary to expectations, the accumulation of p53 protein, a surrogate marker of p53 inactivation, was weakly but positively associated with WAF1 expression (p = 0.05). Surprisingly, there was no significant correlation with S-phase fraction, ER or PgR status, tumor size, age, ploidy, nuclear grade, or survival.
  
  
  CONCLUSIONS
  WAF1 expression is found in the nuclei of a small fraction of cells in human breast tumors. WAF1 status is not significantly associated with cell proliferation, other established prognostic factors, or clinical outcome.
authors.affiliation: University of Texas Health Science Center, Department of Medicine/Medical Oncology, San Antonio 78284-7884, USA.
authors.forename: S G
authors.initials: SG
authors.lastname: Diab
authors.forename: Y Y
authors.initials: YY
authors.lastname: Yu
authors.forename: S G
authors.initials: SG
authors.lastname: Hilsenbeck
authors.forename: D C
authors.initials: DC
authors.lastname: Allred
authors.forename: R M
authors.initials: RM
authors.lastname: Elledge
mesh_terms: D001943:Breast Neoplasms / Q000737:chemistry* / Q000473:pathology; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000032:analysis*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008875:Middle Aged; D011379:Prognosis; D016196:S Phase / Q000502:physiology; D013194:Staining and Labeling; D016159:Tumor Suppressor Protein p53 / Q000032:analysis
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D016159:Tumor Suppressor Protein p53