title: DCYTB is a predictor of outcome in breast cancer that functions via iron-independent mechanisms.
abstract: Duodenal cytochrome b (DCYTB) is a ferrireductase that functions together with divalent metal transporter 1 (DMT1) to mediate dietary iron reduction and uptake in the duodenum. DCYTB is also a member of a 16-gene iron regulatory gene signature (IRGS) that predicts metastasis-free survival in breast cancer patients. To better understand the relationship between DCYTB and breast cancer, we explored in detail the prognostic significance and molecular function of DCYTB in breast cancer.
  
  
  
  The prognostic significance of DCYTB expression was evaluated using publicly available microarray data. Signaling Pathway Impact Analysis (SPIA) of microarray data was used to identify potential novel functions of DCYTB. The role of DCYTB was assessed using immunohistochemistry and measurements of iron uptake, iron metabolism, and FAK signaling.
  
  
  
  High DCYTB expression was associated with prolonged survival in two large independent cohorts, together totaling 1610 patients (cohort #1, p = 1.6e-11, n = 741; cohort #2, p = 1.2e-05, n = 869; log-rank test) as well as in the Gene expression-based Outcome for Breast cancer Online (GOBO) cohort (p < 1.0e-05, n = 1379). High DCYTB expression was also associated with increased survival in homogeneously treated groups of patients who received either tamoxifen or chemotherapy. Immunohistochemistry revealed that DCYTB is localized on the plasma membrane of breast epithelial cells, and that expression is dramatically reduced in high-grade tumors. Surprisingly, neither overexpression nor knockdown of DCYTB affected levels of ferritin H, transferrin receptor, labile iron or total cellular iron in breast cancer cells. Because SPIA pathway analysis of patient microarray data revealed an association between DCYTB and the focal adhesion pathway, we examined the influence of DCYTB on FAK activation in breast cancer cells. These experiments reveal that DCYTB reduces adhesion and activation of focal adhesion kinase (FAK) and its adapter protein paxillin.
  
  
  
  DCYTB is an important predictor of outcome and is associated with response to therapy in breast cancer patients. DCYTB does not affect intracellular iron in breast cancer cells. Instead, DCYTB may retard cancer progression by reducing activation of FAK, a kinase that plays a central role in tumor cell adhesion and metastasis.
authors.affiliation: Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT, 06030, USA.|Present address: Department of Molecular Biomedical Sciences, North Carolina State University, CVM Research Building 474, Raleigh, NC, 27695, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Lemler
authors.affiliation: Center for Quantitative Medicine, University of Connecticut Health Center, Farmington, CT, 06030, USA.|Present address: Statistical Sciences Group CCS-6, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
authors.forename: Miranda L
authors.initials: ML
authors.lastname: Lynch
authors.affiliation: Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT, 06030, USA.
authors.forename: Lia
authors.initials: L
authors.lastname: Tesfay
authors.affiliation: Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT, 06030, USA.
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Deng
authors.affiliation: Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT, 06030, USA.
authors.forename: Bibbin T
authors.initials: BT
authors.lastname: Paul
authors.affiliation: Department of Pathology, University of Connecticut Health Center, Farmington, CT, 06030, USA.
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Pathology, University of Connecticut Health Center, Farmington, CT, 06030, USA.
authors.forename: Poornima
authors.initials: P
authors.lastname: Hegde
authors.affiliation: Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT, 06030, USA.|School of Dental Medicine, University of Connecticut Health Center, Farmington, CT, 06030, USA.
authors.forename: David H
authors.initials: DH
authors.lastname: Manz
authors.affiliation: Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT, 06030, USA. storti@uchc.edu.
authors.forename: Suzy V
authors.initials: SV
authors.lastname: Torti
authors.affiliation: Department of Medicine, University of Connecticut Health Center, Farmington, CT, 06030, USA.
authors.forename: Frank M
authors.initials: FM
authors.lastname: Torti
mesh_terms: D014408:Biomarkers, Tumor; D001943:Breast Neoplasms / Q000378:metabolism* / Q000401:mortality* / Q000473:pathology / Q000628:therapy; D002448:Cell Adhesion / Q000235:genetics; D003573:Cytochrome b Group / Q000235:genetics / Q000378:metabolism*; D030541:Databases, Genetic; D005260:Female; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism; D015870:Gene Expression; D055785:Gene Knockdown Techniques; D006801:Humans; D007150:Immunohistochemistry; D007501:Iron / Q000378:metabolism*; D053208:Kaplan-Meier Estimate; D009362:Neoplasm Metastasis; D009367:Neoplasm Staging; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D011379:Prognosis; D016896:Treatment Outcome
chemical_list: D014408:Biomarkers, Tumor; D003573:Cytochrome b Group; D007501:Iron; D010088:Oxidoreductases; C422926:CYBRD1 protein, human; D051416:Focal Adhesion Protein-Tyrosine Kinases
keywords: Breast; Cancer; Cancer therapy; DCYTB; Focal adhesion; Iron; Prognosis; Survival