Plasma Low-Molecular-Weight Proteome Profiling Identified Neuropeptide‑Y as a Prostate Cancer Biomarker Polypeptide

In
prostate cancer diagnosis, PSA test has greatly contributed
to the early detection of prostate cancer; however, expanding overdiagnosis
and unnecessary biopsies have emerged as serious issues. To explore
plasma biomarkers complementing the specificity of PSA test, we developed
a unique proteomic technology QUEST-MS (Quick Enrichment of Small
Targets for Mass Spectrometry). The QUEST-MS method based on 96-well
formatted sequential reversed-phase chromatography allowing efficient
enrichment of <20 kDa proteins quickly and reproducibly. Plasma
from 24 healthy controls, 19 benign prostate hypertrophy patients,
and 73 prostate cancer patients were purified with QUEST-MS and analyzed
by LC/MS/MS. Among 153 057 nonredundant peptides, 189 peptides showed
prostate cancer specific detection pattern, which included a neurotransmitter
polypeptide neuropeptide-Y (NPY). We further validated the screening
results by targeted multiple reaction monitoring technology using
independent sample set (n = 110). The ROC curve analysis
revealed that logistic regression-based combination of NPY, and PSA
showed 81.5% sensitivity and 82.2% specificity for prostate cancer
diagnosis. Thus QUEST-MS technology allowed comprehensive and high-throughput
profiling of plasma polypeptides and had potential to effectively
uncover very low abundant tumor-derived small molecules, such as neurotransmitters,
peptide hormones, or cytokines.