title: Biological characteristics of luminal subtypes in pre- and postmenopausal estrogen receptor-positive and HER2-negative breast cancers.
abstract: BACKGROUND
  Estrogen receptor (ER)-positive and human epidermal growth factor receptor 2 (HER2)-negative breast cancers can be divided into luminal A and luminal B subtypes based on Ki67 expression levels. However, the biological differences in ER and progesterone receptor (PR) expression levels between these luminal subtypes are not clear.
  
  
  METHODS
  We examined immunohistochemical expression levels of ER, PR, and Ki67 in 180 ER-positive/HER2-negative breast cancers while taking menopausal status into account. Breast cancers were divided according to ER and PR levels (H: >50%, L: ≤ 50%), and luminal A and B were classified by the Ki67 labeling index (A: Ki67 <14%, B: Ki67 ≥ 14%).
  
  
  RESULTS
  When breast cancers were classified based on ER and PR levels, the distribution of pre- and postmenopausals was significantly different for luminal A (P < 0.0001), but not for luminal B cancers. As for luminal A, ER-H/PR-L cancers were rare among premenopausals (8%), but frequent among postmenopausals (54%). Correlation between ER and PR levels among luminal A cancers was strong in premenopausals but weak in postmenopausals. Since crosstalk with growth factor signaling is unlikely in luminal A, we speculate that intratumoral estrogen insufficiency contributed to the characteristics of postmenopausal ER-H/PR-L cancers.
  
  
  CONCLUSIONS
  We speculate that the biological characteristics of luminal A cancers are influenced by the estrogen environment, but its influence on luminal B cancers may be limited. We believe these considerations constitute useful information for a better understanding of the biology of ER-positive-HER2-negetive breast cancers.
authors.affiliation: Division of Breast and Endocrine, Department of Surgery, Hyogo College of Medicine, Mukogawa-cho 1-1, Nishinomiya, Hyogo, 663-8501, Japan.
authors.forename: Keiko
authors.initials: K
authors.lastname: Murase
authors.forename: Ayako
authors.initials: A
authors.lastname: Yanai
authors.forename: Masaru
authors.initials: M
authors.lastname: Saito
authors.forename: Michiko
authors.initials: M
authors.lastname: Imamura
authors.forename: Yoshimasa
authors.initials: Y
authors.lastname: Miyagawa
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Takatsuka
authors.forename: Natsuko
authors.initials: N
authors.lastname: Inoue
authors.forename: Takashi
authors.initials: T
authors.lastname: Ito
authors.forename: Seiichi
authors.initials: S
authors.lastname: Hirota
authors.forename: Mitsunori
authors.initials: M
authors.lastname: Sasa
authors.forename: Toyomasa
authors.initials: T
authors.lastname: Katagiri
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Fujimoto
authors.forename: Takuya
authors.initials: T
authors.lastname: Hatada
authors.forename: Shigetoshi
authors.initials: S
authors.lastname: Ichii
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Nishizaki
authors.forename: Naohiro
authors.initials: N
authors.lastname: Tomita
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Miyoshi
mesh_terms: D014408:Biomarkers, Tumor / Q000378:metabolism; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology*; D005260:Female; D006801:Humans; D019394:Ki-67 Antigen / Q000378:metabolism; D008875:Middle Aged; D017698:Postmenopause; D017697:Premenopause; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000378:metabolism*; D011980:Receptors, Progesterone / Q000378:metabolism*
chemical_list: D014408:Biomarkers, Tumor; D019394:Ki-67 Antigen; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; C508053:ERBB2 protein, human