title: Peroxiredoxin-1 protects estrogen receptor α from oxidative stress-induced suppression and is a protein biomarker of favorable prognosis in breast cancer.
abstract: BACKGROUND
  Peroxiredoxin-1 (PRDX1) is a multifunctional protein, acting as a hydrogen peroxide (H2O2) scavenger, molecular chaperone and immune modulator. Although differential PRDX1 expression has been described in many tumors, the potential role of PRDX1 in breast cancer remains highly ambiguous. Using a comprehensive antibody-based proteomics approach, we interrogated PRDX1 protein as a putative biomarker in estrogen receptor (ER)-positive breast cancer.
  
  
  METHODS
  An anti-PRDX1 antibody was validated in breast cancer cell lines using immunoblotting, immunohistochemistry and reverse phase protein array (RPPA) technology. PRDX1 protein expression was evaluated in two independent breast cancer cohorts, represented on a screening RPPA (n = 712) and a validation tissue microarray (n = 498). In vitro assays were performed exploring the functional contribution of PRDX1, with oxidative stress conditions mimicked via treatment with H2O2, peroxynitrite, or adenanthin, a PRDX1/2 inhibitor.
  
  
  RESULTS
  In ER-positive cases, high PRDX1 protein expression is a biomarker of improved prognosis across both cohorts. In the validation cohort, high PRDX1 expression was an independent predictor of improved relapse-free survival (hazard ratio (HR) = 0.62, 95% confidence interval (CI) = 0.40 to 0.96, P = 0.032), breast cancer-specific survival (HR = 0.44, 95% CI = 0.24 to 0.79, P = 0.006) and overall survival (HR = 0.61, 95% CI = 0.44 to 0.85, P = 0.004). RPPA screening of cancer signaling proteins showed that ERα protein was upregulated in PRDX1 high tumors. Exogenous H2O2 treatment decreased ERα protein levels in ER-positive cells. PRDX1 knockdown further sensitized cells to H2O2- and peroxynitrite-mediated effects, whilst PRDX1 overexpression protected against this response. Inhibition of PRDX1/2 antioxidant activity with adenanthin dramatically reduced ERα levels in breast cancer cells.
  
  
  CONCLUSIONS
  PRDX1 is shown to be an independent predictor of improved outcomes in ER-positive breast cancer. Through its antioxidant function, PRDX1 may prevent oxidative stress-mediated ERα loss, thereby potentially contributing to maintenance of an ER-positive phenotype in mammary tumors. These results for the first time imply a close connection between biological activity of PRDX1 and regulation of estrogen-mediated signaling in breast cancer.
authors.forename: Patrick C
authors.initials: PC
authors.lastname: O'Leary
authors.forename: Marta
authors.initials: M
authors.lastname: Terrile
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Bajor
authors.forename: Pawel
authors.initials: P
authors.lastname: Gaj
authors.forename: Bryan T
authors.initials: BT
authors.lastname: Hennessy
authors.forename: Gordon B
authors.initials: GB
authors.lastname: Mills
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Zagozdzon
authors.forename: Darran P
authors.initials: DP
authors.lastname: O'Connor
authors.forename: Donal J
authors.initials: DJ
authors.lastname: Brennan
authors.forename: Kate
authors.initials: K
authors.lastname: Connor
authors.forename: Jane
authors.initials: J
authors.lastname: Li
authors.forename: Ana Maria
authors.initials: AM
authors.lastname: Gonzalez-Angulo
authors.forename: Han-Dong
authors.initials: HD
authors.lastname: Sun
authors.forename: Jian-Xin
authors.initials: JX
authors.lastname: Pu
authors.forename: Fredrik
authors.initials: F
authors.lastname: Pontén
authors.forename: Mathias
authors.initials: M
authors.lastname: Uhlén
authors.forename: Karin
authors.initials: K
authors.lastname: Jirström
authors.forename: Dominika A
authors.initials: DA
authors.lastname: Nowis
authors.forename: John P
authors.initials: JP
authors.lastname: Crown
authors.forename: Radoslaw
authors.initials: R
authors.lastname: Zagozdzon
authors.forename: William M
authors.initials: WM
authors.lastname: Gallagher
mesh_terms: D014408:Biomarkers, Tumor; D001943:Breast Neoplasms / Q000378:metabolism* / Q000401:mortality*; D045744:Cell Line, Tumor; D015331:Cohort Studies; D047628:Estrogen Receptor alpha / Q000378:metabolism*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D018384:Oxidative Stress; D054464:Peroxiredoxins / Q000378:metabolism*; D011379:Prognosis; D015398:Signal Transduction
chemical_list: D014408:Biomarkers, Tumor; D047628:Estrogen Receptor alpha; D054464:Peroxiredoxins