Identification of a Novel Autoimmune Peptide Epitope of Prostein in Prostate Cancer

J Proteome Res. 2017 Jan 6;16(1):204-216. doi: 10.1021/acs.jproteome.6b00620. Epub 2016 Oct 24.

Abstract

There is a demand for novel targets and approaches to diagnose and treat prostate cancer (PCA). In this context, serum and plasma samples from a total of 609 individuals from two independent patient cohorts were screened for IgG reactivity against a sum of 3833 human protein fragments. Starting from planar protein arrays with 3786 protein fragments to screen 80 patients with and without PCA diagnosis, 161 fragments (4%) were chosen for further analysis based on their reactivity profiles. Adding 71 antigens from literature, the selection of antigens was corroborated for their reactivity in a set of 550 samples using suspension bead arrays. The antigens prostein (SLC45A3), TATA-box binding protein (TBP), and insulin-like growth factor 2 mRNA binding protein 2 (IGF2BP2) showed higher reactivity in PCA patients with late disease compared with early disease. Because of its prostate tissue specificity, we focused on prostein and continued with mapping epitopes of the 66-mer protein fragment using patient samples. Using bead-based assays and 15-mer peptides, a minimal peptide epitope was identified and refined by alanine scanning to the KPxAPFP. Further sequence alignment of this motif revealed homology to transmembrane protein 79 (TMEM79) and TGF-beta-induced factor 2 (TGIF2), thus providing a reasoning for cross-reactivity found in females. A comprehensive workflow to discover and validate IgG reactivity against prostein and homologous targets in human serum and plasma was applied. This study provides useful information when searching for novel biomarkers or drug targets that are guided by the reactivity of the immune system against autoantigens.

Keywords: Human Protein Atlas; antigen; autoimmunity; epitope mapping; peptide; planar microarray; profiling; prostate cancer; prostein; suspension bead array.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Amino Acid Motifs
  • Antibodies, Neoplasm / biosynthesis
  • Antibodies, Neoplasm / chemistry
  • Autoimmunity
  • Biomarkers, Tumor / genetics*
  • Biomarkers, Tumor / immunology
  • Breast Neoplasms / diagnosis
  • Breast Neoplasms / genetics
  • Breast Neoplasms / immunology
  • Breast Neoplasms / metabolism
  • Case-Control Studies
  • Cross Reactions
  • Epitope Mapping
  • Epitopes / chemistry*
  • Epitopes / genetics
  • Epitopes / immunology
  • Female
  • Gene Expression Profiling
  • Gene Expression Regulation, Neoplastic*
  • Homeodomain Proteins / genetics
  • Homeodomain Proteins / immunology
  • Humans
  • Immunoglobulin G / biosynthesis
  • Immunoglobulin G / chemistry
  • Insulin-Like Growth Factor II / genetics*
  • Insulin-Like Growth Factor II / immunology
  • Male
  • Membrane Proteins / genetics*
  • Membrane Proteins / immunology
  • Middle Aged
  • Prostatic Neoplasms / diagnosis
  • Prostatic Neoplasms / genetics*
  • Prostatic Neoplasms / immunology
  • Prostatic Neoplasms / metabolism
  • Protein Array Analysis
  • Repressor Proteins / genetics
  • Repressor Proteins / immunology
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • TATA-Box Binding Protein / genetics*
  • TATA-Box Binding Protein / immunology

Substances

  • Antibodies, Neoplasm
  • Biomarkers, Tumor
  • Epitopes
  • Homeodomain Proteins
  • Immunoglobulin G
  • Membrane Proteins
  • Repressor Proteins
  • TATA-Box Binding Protein
  • TBP protein, human
  • TGIF2 protein, human
  • Tmem79 protein, human
  • prostein
  • Insulin-Like Growth Factor II