title: Hornerin Is Involved in Breast Cancer Progression.
abstract: OBJECTIVE
  The S100 gene family, which comprises over 20 members, including S100A1, S100A2, S100A8, S100A9, profilaggrin, and hornerin encodes low molecular weight calcium-binding proteins with physiological and pathological roles in keratinization. Recent studies have suggested a link between S100 proteins and human cancer progression. The purpose of the present study was to determine the expression levels of hornerin, S100A8, and S100A9 and evaluate their roles in the progression of invasive ductal carcinoma (IDC).
  
  
  METHODS
  Seventy cases of ductal carcinoma in situ (DCIS), IDC, and metastatic carcinoma in lymph nodes (MCN) were included. Tissue microarrays were constructed from lesions of DCIS, IDC, and MCN from the same patients. Expression of hornerin, S100A8, and S100A9 was analyzed using immunohistochemistry.
  
  
  RESULTS
  The expression of hornerin was associated with the estrogen receptor-negative (p=0.003) and the human epidermal growth factor receptor 2-positive (p=0.002) groups. The expression of S100A8 was associated with a higher pT stage (p=0.017). A significant (p<0.001) correlation between the expression of S100A9 and S100A8 was also found. The mean percentages of hornerin-positive tumor cells in DCIS, IDC, and MCN were 1.0%±3.3% (mean±standard deviation), 12.0%±24.0%, and 75.3%± 27.6%, respectively. The expression of hornerin significantly (p<0.001) increased with the progression of carcinoma. The mean levels of S100A8 and S100A9 in DCIS, IDC, and MCN were not significantly (p>0.050) different. The expression of hornerin increased in a stepwise manner (DCIS<IDC<MCN).
  
  
  CONCLUSIONS
  Our data suggest that hornerin is involved in breast cancer progression and malignant transformation from preinvasive lesions.
authors.affiliation: Department of Pathology, Korea University Guro Hospital, Seoul, Korea.
authors.forename: Jinhyuk
authors.initials: J
authors.lastname: Choi
authors.affiliation: Green Cross Reference Laboratory, Yongin, Korea.
authors.forename: Dong-Il
authors.initials: DI
authors.lastname: Kim
authors.affiliation: Department of Pathology, Korea University Guro Hospital, Seoul, Korea.
authors.forename: Jinkyoung
authors.initials: J
authors.lastname: Kim
authors.affiliation: Department of Pathology, Korea University Guro Hospital, Seoul, Korea.
authors.forename: Baek-Hui
authors.initials: BH
authors.lastname: Kim
authors.affiliation: Department of Pathology, Korea University Guro Hospital, Seoul, Korea.
authors.forename: Aeree
authors.initials: A
authors.lastname: Kim
keywords: Breast neoplasms; Hornerin protein; S100 proteins