title: High EZH2 Protein Expression Is Associated with Poor Overall Survival in Patients with Luminal A Breast Cancer.
abstract: OBJECTIVE
  The enhancer of zeste homologue 2 (EZH2) is a catalytic subunit of the polycomb repressive complex 2, a highly conserved histone methyltransferase. EZH2 overexpression has been implicated in various malignancies, including breast cancer, where is associated with poor outcomes. This study aims to clarify nuclear EZH2 expression levels in breast cancers using immunohistochemistry (IHC) and correlate these findings with clinicopathologic variables, including prognostic significance.
  
  
  METHODS
  IHC was performed on tissue microarrays of 432 invasive ductal carcinoma (IDC) tumors. Associations between EZH2 expression, clinicopathologic characteristics, and molecular subtype were retrospectively analyzed. The relationship between EZH2 protein expression in normal breast tissue and ductal carcinoma in situ (DCIS) was also assessed.
  
  
  RESULTS
  High EZH2 expression was demonstrated in 215 of 432 tumors (49.8%). EZH2 was more frequently expressed in DCIS and IDC than in normal breast tissue (p=0.001). High EZH2 expression significantly correlated with high histologic grade (p<0.001), large tumor size (p=0.014), advanced pathologic stage (p=0.006), negative estrogen receptor status (p<0.001), positive human epidermal growth factor receptor 2 (HER2) status (p<0.001), high Ki-67 staining index (p<0.001), positive cytokeratin 5/6 status (p=0.003), positive epidermal growth factor receptor status (p<0.001), and positive p53 status (p<0.001). Based on molecular subtypes, high EZH2 expression was significantly associated with HER2-negative luminal B, HER2-positive luminal B, and HER2 type and triple-negative basal cancers (p<0.001). In patients with luminal A, there was a significant trend toward shorter overall survival for those with tumors having high EZH2 expression compared to those with tumors having low EZH2 expression (p=0.045).
  
  
  CONCLUSIONS
  EZH2 is frequently upregulated in breast malignancies, and it may play an important role in cancer development and progression. Furthermore, EZH2 may be a prognostic marker, especially in patients with luminal A cancer.
authors.affiliation: Department of Pathology, Soonchunhyang University Cheonan Hospital, Soonchunhyang University College of Medicine, Cheonan, Korea.
authors.forename: Si-Hyong
authors.initials: SH
authors.lastname: Jang
authors.affiliation: Department of Surgery, Soonchunhyang University Cheonan Hospital, Soonchunhyang University College of Medicine, Cheonan, Korea.
authors.forename: Jong Eun
authors.initials: JE
authors.lastname: Lee
authors.affiliation: Department of Pathology, Soonchunhyang University Cheonan Hospital, Soonchunhyang University College of Medicine, Cheonan, Korea.
authors.forename: Mee-Hye
authors.initials: MH
authors.lastname: Oh
authors.affiliation: Department of Pathology, Soonchunhyang University Cheonan Hospital, Soonchunhyang University College of Medicine, Cheonan, Korea.
authors.forename: Ji-Hye
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Department of Pathology, Soonchunhyang University Cheonan Hospital, Soonchunhyang University College of Medicine, Cheonan, Korea.
authors.forename: Hyun Deuk
authors.initials: HD
authors.lastname: Cho
authors.affiliation: Department of Pathology, Soonchunhyang University Cheonan Hospital, Soonchunhyang University College of Medicine, Cheonan, Korea.
authors.forename: Kyung-Ju
authors.initials: KJ
authors.lastname: Kim
authors.affiliation: Department of Surgery, Soonchunhyang University Cheonan Hospital, Soonchunhyang University College of Medicine, Cheonan, Korea.
authors.forename: Sung Yong
authors.initials: SY
authors.lastname: Kim
authors.affiliation: Department of Surgery, Soonchunhyang University Cheonan Hospital, Soonchunhyang University College of Medicine, Cheonan, Korea.
authors.forename: Sun Wook
authors.initials: SW
authors.lastname: Han
authors.affiliation: Division of Hemato-Oncology, Department of Internal Medicine, Soonchunhyang University Cheonan Hospital, Soonchunhyang University College of Medicine, Cheonan, Korea.
authors.forename: Han Jo
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: Division of Hemato-Oncology, Department of Internal Medicine, Soonchunhyang University Cheonan Hospital, Soonchunhyang University College of Medicine, Cheonan, Korea.
authors.forename: Sang Byung
authors.initials: SB
authors.lastname: Bae
authors.affiliation: Department of Pathology, Soonchunhyang University Cheonan Hospital, Soonchunhyang University College of Medicine, Cheonan, Korea.
authors.forename: Hyun Ju
authors.initials: HJ
authors.lastname: Lee
keywords: Breast neoplasms; Enhancer of zeste homologue 2; Immunohistochemistry; Prognosis