Urinary CD14 as a potential biomarker for benign prostatic hyperplasia - discovery by combining MALDI-TOF-based biostatistics and ESI-MS/MS-based stable-isotope labeling

Purpose: Quest for specific urinary biomarkers for benign prostatic hyperplasia (BPH). Experimental design: Proteomics studies were conducted with urines of the training set to discovering marker candidates that could differentiate BPH from normal subjects by matching results deduced from MALDI-TOF of individual samples and results deduced from nanoLC-ESI-MS/MS-based stable isotope dimethyl labeling of two pooled samples (BPH and normal). Samples were digested before analysis and such an approach takes into account the subject-to-subject variation and differential amount, as well as protein identification. Selected markers were validated by ELISA conducted on the training set and the test set as well as another set of urines collected from prostate cancer patients. Results: Nine marker candidates were identified from proteomics studies; CD14, prostate-specific antigen and pancreatic α-amylase precursor were further selected for ELISA validation. Urinary CD14 is among the best match with high specificity (>81%) for both training and test sets. In addition, from the study of prostate cancer patients, CD14 also allows the distinction of BPH from cancer with high specificity (84-100%) when combined with urinary prostate-specific antigen. Conclusions and clinical relevance: Urinary CD14 is suggested to have a high specificity in the diagnosis of BPH in distinction from normal as well as cancer subjects.