The C-terminal fragment of prostate-specific antigen, a 2331 Da peptide, as a new urinary pathognomonic biomarker candidate for diagnosing prostate cancer.

BACKGROUND AND OBJECTIVES: Prostate cancer (PCa) is one of the most common cancers and leading cause of cancer-related deaths in men. Mass screening has been carried out since the 1990s using prostate-specific antigen (PSA) levels in the serum as a PCa biomarker. However, although PSA is an excellent organ-specific marker, it is not a cancer-specific marker. Therefore, the aim of this study was to discover new biomarkers for the diagnosis of PCa. MATERIALS AND METHODS: We focused on urine samples voided following prostate massage (digital rectal examination [DRE]) and conducted a peptidomic analysis of these samples using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS(n)). Urinary biomaterials were concentrated and desalted using CM-Sepharose prior to the following analyses being performed by MALDI-TOF/MS(n): 1) differential analyses of mass spectra; 2) determination of amino acid sequences; and 3) quantitative analyses using a stable isotope-labeled internal standard. RESULTS: Multivariate analysis of the MALDI-TOF/MS mass spectra of urinary extracts revealed a 2331 Da peptide in urine samples following DRE. This peptide was identified as a C-terminal PSA fragment composed of 19 amino acid residues. Moreover, quantitative analysis of the relationship between isotope-labeled synthetic and intact peptides using MALDI-TOF/MS revealed that this peptide may be a new pathognomonic biomarker candidate that can differentiate PCa patients from non-cancer subjects. CONCLUSION: The results of the present study indicate that the 2331 Da peptide fragment of PSA may become a new pathognomonic biomarker for the diagnosis of PCa. A further large-scale investigation is currently underway to assess the possibility of using this peptide in the early detection of PCa.

[Fundamental evaluation of HCV core antigen method comparison with Cobas Amplicor HCV monitor v2.0 (high range method)].

Quantitative measurement of hepatitis C virus (HCV) has been performed by PCR method. However, PCR method has problems such as a special instrument, a complicated manual skill and a high cost. Recently, simple and highly sensitive HCV core antigen (Ag) method has been developed. We performed fundamental evaluation of HCV core Ag method, and compared HCV core Ag method with HCV PCR high-range method. The intra-assay and inter-assay variation coefficients for HCV core Ag were calculated to be within the ranges of 1.0-11.3% and 0.8-9.3%, respectively. The test of dilution linearity revealed the unstableness in the vicinity of a cut-off level of 50 fmol/L. Based on the result of the high-range method; sensitivity, specificity, positive predictive value, negative predictive value, and agreement rate were 97.0%, 100%, 100%, 82.0%, and 96.5%, respectively. The correlation between the HCV core Ag method and the high-range method was r = 0.87. Cost per sample and time from sample preparation to final report for HCV core Ag were cheaper and shorter than those of HCV PCR method, respectively. We consider that the HCV core Ag method seems to be useful as the quantitative measurement of HCV with respect to rapidness, easiness and low cost.