title: Cystatin M loss is associated with the losses of estrogen receptor, progesterone receptor, and HER4 in invasive breast cancer.
abstract: BACKGROUND
  This study was aimed at understanding the clinicopathological significance of cystatin M loss, and investigating possible factors responsible for cystatin M loss in breast cancer.
  
  
  METHODS
  The expression of estrogen receptor (ER), progesterone receptor (PR), HER2, HER4, and cystatin M was retrospectively analyzed using immunohistochemistry in 117 patients with ductal carcinoma in situ (DCIS) and in 175 patients with invasive breast cancer (IBC). The methylation status of CST6 gene encoding cystatin M was evaluated using methylation-specific polymerase chain reaction (PCR) in formalin-fixed paraffin-embedded tissues from 292 participants and using pyrosequencing in fresh-frozen tumor and matched normal tissues from 51 IBC patients.
  
  
  RESULTS
  Cystatin M loss was found in 9 (8%) of 117 patients with DCIS and in 99 (57%) of 175 with invasive breast cancer (IBC) (P < 0.0001). Cystatin M loss was found in 58 (57%) of 101 HER2-negative IBCs and in 41 (55%) of 74 HER2-positive IBCs, and this difference was not statistically significant (P = 0.97). However, cystatin M loss was significantly associated with the loss of ER (P = 0.01), PR (P = 0.002), and HER4 (P = 0.003) in IBCs. Cystatin M loss occurred in 34 (76%) of the 45 HER4-negative IBCs and in 65 (50%) of the 130 HER4-positive IBCs. Multivariate analysis showed that cystatin M loss occurred at a 3.57 times (95% CI = 1.28 to 9.98; P = 0.01) higher prevalence in the triple-negative IBCs of ER, PR, and HER4 than in other subtypes, after adjusting for age. The quantity of CST6 methylation was associated with ER loss (P = 0.0002) in IBCs but not with the loss of PR (P = 0.64) or HER4 (P = 0.87).
  
  
  CONCLUSIONS
  The present study suggests that cystatin M loss may be associated with the losses of ER, PR, and HER4 in IBC.
authors.affiliation: Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, Jangan-gu, Suwon, Gyeonggi-do 440-746, Korea. eunkyung.ko@sbri.co.kr
authors.forename: Eunkyung
authors.initials: E
authors.lastname: Ko
authors.forename: Seong-Eun
authors.initials: SE
authors.lastname: Park
authors.forename: Eun Yoon
authors.initials: EY
authors.lastname: Cho
authors.forename: Yujin
authors.initials: Y
authors.lastname: Kim
authors.forename: Jung-Ah
authors.initials: JA
authors.lastname: Hwang
authors.forename: Yeon-Su
authors.initials: YS
authors.lastname: Lee
authors.forename: Seok Jin
authors.initials: SJ
authors.lastname: Nam
authors.forename: Saik
authors.initials: S
authors.lastname: Bang
authors.forename: Joobae
authors.initials: J
authors.lastname: Park
authors.forename: Duk-Hwan
authors.initials: DH
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D018899:CpG Islands / Q000235:genetics; D055332:Cystatin M / Q000235:genetics* / Q000378:metabolism*; D019175:DNA Methylation; D066246:ErbB Receptors / Q000378:metabolism*; D005260:Female; D005455:Fluorescent Antibody Technique; D015870:Gene Expression; D006801:Humans; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D016133:Polymerase Chain Reaction; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D066247:Receptor, ErbB-4; D011960:Receptors, Estrogen / Q000378:metabolism*; D011980:Receptors, Progesterone / Q000378:metabolism*; D046888:Tissue Array Analysis
chemical_list: D055332:Cystatin M; D066246:ErbB Receptors; D018719:Erb-b2 Receptor Tyrosine Kinases; D066247:Receptor, ErbB-4; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; C525104:CST6 protein, human; C508053:ERBB2 protein, human; C587689:ERBB4 protein, human