title: Inflammatory biomarkers for persistent fatigue in breast cancer survivors.
abstract: OBJECTIVE
  This study seeks to define immunologic and inflammatory variables associated with persistent post-treatment fatigue in breast cancer survivors.
  
  
  METHODS
  Leukocyte subsets, plasma inflammatory markers, and ex vivo proinflammatory cytokine production were assessed in 50 fatigued and nonfatigued breast cancer survivors recruited > or = 2 years after successful primary therapy. Multivariate statistical analyses were used to define a composite immunologic biomarker of fatigue risk.
  
  
  RESULTS
  Fatigued breast cancer survivors were distinguished from nonfatigued survivors by increased ex vivo monocyte production of interleukin (IL)-6 and tumor necrosis factor-alpha following lipopolysaccharide stimulation, elevated plasma IL-1ra and soluble IL-6 receptor (sIL-6R/CD126), decreased monocyte cell-surface IL-6R, and decreased frequencies of activated T lymphocytes and myeloid dendritic cells in peripheral blood (all P < 0.05). An inverse correlation between sIL-6R and cell-surface IL-6R was consistent with inflammation-mediated shedding of IL-6R, and in vitro studies confirmed that proinflammatory cytokines induced such shedding. Multivariate linear discriminant function analysis identified two immunologic markers, the ratio of sIL-6R to monocyte-associated IL-6R and decreased circulating CD69+ T lymphocytes, as highly diagnostic of fatigue (P = 0.0005), with cross-validation estimates indicating 87% classification accuracy (sensitivity = 0.83; specificity = 0.83).
  
  
  CONCLUSIONS
  These results extend links between fatigue and inflammatory markers to show a functional alteration in proinflammatory cytokine response to lipopolysaccharide and define a prognostic biomarker of behavioral fatigue.
authors: Cousins Center for Psychoneuroimmunology, University of California at Los Angeles Semel Institute for Neuroscience and Human Behavior, Los Angeles, California 90095-7076, USA.
authors: Alicia
authors: A
authors: Collado-Hidalgo
authors: Julienne E
authors: JE
authors: Bower
authors: Patricia A
authors: PA
authors: Ganz
authors: Steve W
authors: SW
authors: Cole
authors: Michael R
authors: MR
authors: Irwin