Differential diagnosis of prostate cancer and benign prostate hyperplasia using two-dimensional electrophoresis

Abstract

Prostate specific antigen (PSA) is a protease which is characteristic of the prostate. It is widely used as a serum marker for the early diagnosis of prostate cancer (PCa). Nevertheless, for concentrations between 4 and 10 ng/mL, PSA does not enable PCa to be distinguished from benign diseases, such as benign prostate hyperplasia (BPH). In sera, the use of a ratio between free PSA (PSA uncomplexed with protease inhibitor) and total PSA (free PSA and PSA bound to alpha-1 anti-chymotrypsin) enables the "gray zone" to be reduced, but an important proportion of patients are still wrongly classed. Using two-dimensional electrophoresis, we demonstrated using 52 PCa and 40 BPH well-documented clinical cases that BPH sera show a significantly greater percentage of low-molecular-weight free PSA elements (IwPSA) than PCa sera. In our study, the use of a ratio between IwPSA and standard free PSA enables the correct diagnosis of 100% of PCa and 82.5% of BPH cases as against when 73.1% and 42.5% respectively were correctly diagnozed using the total PSA and the free/total PSA ratio. This important finding may be related to differences in the mechanism secreting PSA from the prostate into the bloodstream. We have shown how a tissue marker may be turned into a powerful tumor marker by events probably unrelated to its expression.

Analysis of Subforms of Free Prostate-Specific Antigen in Serum by Two-Dimensional Gel Electrophoresis: Potential to Improve Diagnosis of Prostate Cancer

“…There were also more acidic spots (e.g., spot J) with lower molecular masses but also spots (A, B, C, D) with higher molecular masses of ϳ35 kDa detected only in PCa patients. These results generally confirm the previous 2DE data of Charrier and coworkers (11,22 ), who did not describe the spots in more detail. However, similar to our study, the fPSA forms with molecular masses Ͻ30 kDa also accounted for only ϳ5-10% of the total fPSA (11,22 ).…”

“…The specificity of the fPSA spots was confirmed by addition of anti-PSA antibody 13C9E9D6G8, which was used by Charrier and coworkers (11,22 ), to the polyclonal anti-PSA antibody A056201 (Dako). As demonstrated in Fig.…”

“…However, an even larger number of PSA subforms could be separated as specific spots by two-dimensional electrophoresis (2DE) and immunoblotting (11,21 ). Charrier and coworkers (11,22 ) used the 2DE pattern of fPSA subforms obtained by this technique as a tool to differentiate between patients with PCa and BPH. However, because of the limited analytical sensitivity of their electrophoretic procedure, only combined groups of spots and not single spots could be evaluated with regard to their diagnostic relevance.…”

An investigation of plasma collection, stabilization, and storage procedures for proteomic analysis of clinical samples

“…Two-dimensional gel electrophoresis (2-DE) remains the most widely used proteomic technique owing to the fact that it is currently the method that can separate and measure hundreds of proteins from a single biological sample simultaneously (5,6). Analysis by 2D-PAGE has been used for proteomic studies of breast cancer (7)(8)(9), prostate cancer (10,11), hepatocellular carcinoma (12,13), renal cell carcinoma (14), rheumatoid arthritis (15,16), and hepatitis B infection (17). Many of these biomarker studies utilized human blood serum or plasma samples.…”

A better understanding of molecular mechanisms underlying human disease

“…Using this tool, different low molecular weight-free PSA elements were identified as potential biomarkers to discriminate between benign prostate hyperplasia and prostate cancer [159]. Improvement in both specificity and sensitivity of total PSA and % free PSA (ratio of free PSA to total PSA) using several free PSA subforms, identified by 2-DE, have also been described [160].…”