Development and clinical testing of individual immunoassays for the quantification of serum glycoproteins to diagnose prostate cancer

PLoS One. 2017 Aug 2;12(8):e0181557. doi: 10.1371/journal.pone.0181557. eCollection 2017.


Prostate Cancer (PCa) diagnosis is currently hampered by the high false-positive rate of PSA evaluations, which consequently may lead to overtreatment. Non-invasive methods with increased specificity and sensitivity are needed to improve diagnosis of significant PCa. We developed and technically validated four individual immunoassays for cathepsin D (CTSD), intercellular adhesion molecule 1 (ICAM1), olfactomedin 4 (OLFM4), and thrombospondin 1 (THBS1). These glycoproteins, previously identified by mass spectrometry using a Pten mouse model, were measured in clinical serum samples for testing the capability of discriminating PCa positive and negative samples. The development yielded 4 individual immunoassays with inter and intra-variability (CV) <15% and linearity on dilution of the analytes. In serum, ex vivo protein stability (<15% loss of analyte) was achieved for a duration of at least 24 hours at room temperature and 2 days at 4°C. The measurement of 359 serum samples from PCa positive (n = 167) and negative (n = 192) patients with elevated PSA (2-10 ng/ml) revealed a significantly improved accuracy (P <0.001) when two of the glycoproteins (CTSD and THBS1) were combined with %fPSA and age (AUC = 0.8109; P <0.0001; 95% CI = 0.7673-0.8545). Conclusively, the use of CTSD and THBS1 together with commonly used parameters for PCa diagnosis such as %fPSA and age has the potential to improve the diagnosis of PCa.

MeSH terms

  • Aged
  • Biomarkers, Tumor / blood
  • Cathepsin D / blood*
  • Granulocyte Colony-Stimulating Factor / blood
  • Humans
  • Immunoassay
  • Intercellular Adhesion Molecule-1 / blood
  • Male
  • Middle Aged
  • Prostate-Specific Antigen / blood*
  • Prostatic Neoplasms / diagnosis*
  • ROC Curve
  • Sensitivity and Specificity
  • Thrombospondin 1 / blood*


  • Biomarkers, Tumor
  • ICAM1 protein, human
  • OLFM4 protein, human
  • Thrombospondin 1
  • thrombospondin-1, human
  • Intercellular Adhesion Molecule-1
  • Granulocyte Colony-Stimulating Factor
  • Prostate-Specific Antigen
  • CTSD protein, human
  • Cathepsin D

Grant support

The measurement of clinical samples was conducted at ProteoMediX Inc. and ProteoMediX Inc. funded the assay development at NMI Tübingen. KE, AA and RS are employed by ProteoMediX. MR is providing paid statistical consultancy to ProteoMediX through its company (Abanovus LLC). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.