Benign prostate-specific antigen (BPSA) in serum is increased in benign prostate disease

Software-Assisted Data Processing Workflow for Intact Glycoprotein Mass Spectrometry

Intact protein analysis by mass spectrometry is important for several applications such as assessing post-translational modifications and biotransformation. In particular, intact protein analysis allows the detection of proteoforms that are commonly missed by other approaches such as proteolytic digestion followed by bottom-up analysis. Two quantification methods are mainly used for intact protein data quantification, namely the extracted ion and deconvolution approaches. However, a consensus with regard to a single best practice for intact protein data processing is lacking. Furthermore, many data processing tools are not fit-for-purpose and, as a result, the analysis of intact proteins is laborious and lacks the throughput required to be implemented for the analysis of clinical cohorts. Therefore, in this study, we investigated the application of a software-assisted data analysis and processing workflow in order to streamline intact protein integration, annotation, and quantification via deconvolution. In addition, the assessment of orthogonal data sets generated via middle-up and bottom-up analysis enabled the cross-validation of cleavage proteoform assignments present in seminal prostate-specific antigen (PSA). Furthermore, deconvolution quantification of PSA from patients' urine revealed results that were comparable with manually performed quantification based on extracted ion electropherograms. Overall, the presented workflow allows fast and efficient processing of intact protein data. The raw data is available on MassIVE using the identifier MSV000086699.

Profiling the proteoforms of urinary prostate-specific antigen by capillary electrophoresis - mass spectrometry

Early detection of prostate cancer may lead to the overdiagnosis and overtreatment of patients as well as missing significant cancers. The current diagnostic approach uses elevated serum concentrations of prostate-specific antigen (PSA) as an indicator of risk. However, this test has been widely criticized as it shows poor specificity and sensitivity. In order to improve early detection and diagnosis, several studies have investigated whether different PSA proteoforms are correlated to prostate cancer. Until now, studies and methodologies for the comprehensive characterization of PSA proteoforms from biofluids are scarce. For this purpose, we developed an intact protein assay to analyze PSA by capillary electrophoresis-electrospray ionization-mass spectrometry after affinity purification from patients' urine. Here, we determined six proteolytic cleavage variants. In regard to glycosylation, tri-, di-, mono- and non-sialylated complex-type N-glycans were found on non-cleaved PSA, as well as the non-glycosylated variant. The performance of the intact protein assay was assessed using a pooled sample, obtaining an inter-day variability of 15%. Furthermore, urinary patient samples were analyzed by intact protein analysis and a bottom-up approach (glycopeptide analysis). This combined approach revealed complimentary information on both levels, demonstrating the benefit of using two orthogonal techniques to provide a thorough profile of urinary PSA. SIGNIFICANCE: The detection of clinically relevant prostate cancer requires a more specific and sensitive biomarker and, in this case, several PSA proteoforms may be able to aid or improve the current PSA test. However, a comprehensive analysis of the intact PSA proteoform profile is still lacking. This study investigated the PSA proteoforms present in urine and, in particular, determined the relative contribution of cleaved PSA and non-cleaved PSA forms to the total glycosylation profile. Importantly, intact protein analysis did not require further sample treatment before being measured by CE-ESI-MS. Furthermore, its glycosylation was also assessed in a bottom-up approach to provide complementary information. Overall, these results represent an important basis for future characterization and biomarker studies.

Molecularly imprinted polymers in biological applications

Molecularly imprinted polymers (MIPs) are currently widely used and further developed for biological applications. The MIP synthesis procedure is a key process, and a wide variety of protocols exist. The templates that are used for imprinting vary from the smallest glycosylated glycan structures or even amino acids to whole proteins or bacteria. The low cost, quick preparation, stability and reproducibility have been highlighted as advantages of MIPs. The biological applications utilizing MIPs discussed here include enzyme-linked assays, sensors, in vivo applications, drug delivery, cancer diagnostics and more. Indeed, there are numerous examples of how MIPs can be used as recognition elements similar to natural antibodies.

Detection of prostate specific antigen (PSA) in human saliva using an ultra-sensitive nanocomposite of graphene nanoplatelets with diblock-co-polymers and Au electrodes

Prostate-specific antigen (PSA) is a commonly used biomarker for the detection of prostate cancer (PCa) and there are numerous data available for its invasive detection in the serum and whole blood. In this work, an electrochemical sensing method was devised to detect traces of PSA in human saliva using a hybrid nanocomposite of graphene nanoplatelets with diblock co-polymers and Au electrodes (GRP-PS₆₇-b-PAA₂₇-Au). The pure graphitic composition on filter paper provides significantly high electrical and thermal conductivity while PS₆₇-b-PAA₂₇ makes an amphiphilic bridge between GRP units. The sensor utilizes the binding of an anti-PSA antibody with an antigen-PSA to act as a resistor in a circuit providing an impedance change that in turn allows for the detection and quantification of PSA in saliva samples. A miniaturized electrical impedance analyzer was interfaced with a sensor chip and the data were recorded in real-time using a Bluetooth-enabled module. This fully integrated and optimized sensing device exhibited a wide PSA range of detection from 0.1 pg mL^-1 to 100 ng mL^-1 (R² = 0.963) with a lower limit of detection of 40 fg mL^-1. The performance of the biosensor chip was validated with an enzyme-linked immunosorbent assay technique with a regression coefficient as high as 0.940. The advantages of the newly developed saliva-PSA electrical biosensor over previously reported serum-PSA electrochemical biosensors include a faster response time (3-5 min) to achieve a stable electrical signal for PSA detection, high selectivity, improved sensitivity, no additional requirement of a redox electrolyte for electron exchange and excellent shelf life. The presented sensor is aimed for clinical commercialization to detect PSA in human saliva.

Human Serum Low Molecular Mass Prostate-specific Antigen As Biomarker

Background

Prostate-specific antigen (PSA) is a glycoprotein tumor marker known to exist as numerous glycospecies. Investigations on its glycobiochemical properties aimed at their use in the preparation of adjuncts in determining PSA concentration for clinical purposes have accumulated a lot of data on its structural properties. In this study, we reconsidered unexplored ubiquitously present low molecular mass species of PSA regarding to molecular mass, origin and pathophysiological source specificity in order to evaluate them as biomarkers.

Methods

Data on low molecular mass PSA-immunoreactive species from sera of subjects with prostate cancer (PCa), benign prostatic hyperplasia (BPH), breast cancer (BCa), and urine of healthy males obtained by on-chip immunoaffinity chromatography combined with mass spectrometry were analyzed.

Results

The results obtained indicated PSA species common to BCa, PCa, and BPH at 12-13 kDa, 17-19 kDa and 21-24 kDa. The striking difference in predominant frequencies made the profile characteristic in each examined pathophysiological condition. On the other hand, paired groups of prostatic and extraprostatic PSA contained rare species with small differences among groups concerning individual species. Low molecular mass PSA also included rare species unique for each group of samples.

Conclusion

The results obtained revealed that uniformity of low molecular mass PSA-immunoreactive species in sera prevails over diversity related to cancer and non-cancer conditions, but at the same time some of them are molecules with biomarker potential for BPH detection.

Investigation of contactless detection using a giant magnetoresistance sensor for detecting prostate specific antigen

This paper presents a contactless detection method for detecting prostate specific antigen with a giant magnetoresistance sensor. In contactless detection case, the prostate specific antigen sample preparation was separated from the sensor that prevented the sensor from being immersed in chemical solvents, and made the sensor implementing in immediately reuse without wash. Experimental results showed that applied an external magnetic field in a range of 50 Oe to 90 Oe, Dynabeads with a concentration as low as 0.1 μg/mL can be detected by this system and could give an approximate quantitation to the logarithmic of Dynabeads concentration. Sandwich immunoassay was employed for preparing PSA samples. The PSA capture was implemented on a gold film modified with a self-assembled monolayer and using biotinylated secondary antibody against PSA and streptavidinylated Dynabeads. With DC magnetic field in the range of 50 to 90 Oe, PSA can be detected with a detection limit as low as 0.1 ng/mL. Samples spiked with different concentrations of PSA can be distinguished clearly. Due to the contactless detection method, the detection system exhibited advantages such as convenient manipulation, reusable, inexpensive, small weight. So, this detection method was a promising candidate in biomarker detection, especially in point of care detection.

MIP-Based Sensors: Promising New Tools for Cancer Biomarker Determination

Detecting cancer disease at an early stage is one of the most important issues for increasing the survival rate of patients. Cancer biomarker detection helps to provide a diagnosis before the disease becomes incurable in later stages. Biomarkers can also be used to evaluate the progression of therapies and surgery treatments. In recent years, molecularly imprinted polymer (MIP) based sensors have been intensely investigated as promising analytical devices in several fields, including clinical analysis, offering desired portability, fast response, specificity, and low cost. The aim of this review is to provide readers with an overview on recent important achievements in MIP-based sensors coupled to various transducers (e.g., electrochemical, optical, and piezoelectric) for the determination of cancer biomarkers by selected publications from 2012 to 2016.

The Present and Future of Biomarkers in Prostate Cancer: Proteomics, Genomics, and Immunology Advancements

Prostate cancer (PC) is the second most common form of cancer in men worldwide. Biomarkers have emerged as essential tools for treatment and assessment since the variability of disease behavior, the cost and diversity of treatments, and the related impairment of quality of life have given rise to a need for a personalized approach. High-throughput technology platforms in proteomics and genomics have accelerated the development of biomarkers. Furthermore, recent successes of several new agents in PC, including immunotherapy, have stimulated the search for predictors of response and resistance and have improved the understanding of the biological mechanisms at work. This review provides an overview of currently established biomarkers in PC, as well as a selection of the most promising biomarkers within these particular fields of development.

Sensitivity improvement of a sandwich-type ELISA immunosensor for the detection of different prostate-specific antigen isoforms in human serum using electrochemical impedance spectroscopy and an ordered and hierarchically organized interfacial supramolecular architecture

A gold millielectrode (GME) functionalized with a mixed (16-MHA + EG3SH) self-assembled monolayer (SAM) was used to fabricate an indirect enzyme-linked immunosorbent assay (ELISA) immunosensor for the sensitive detection of prostate-specific antigen (PSA), a prostate cancer (PCa) biomarker, in human serum samples. To address and minimize the issue of non-specific protein adsorption, an organic matrix (amine-PEG3-biotin/avidin) was assembled on the previously functionalized electrode surface to build up an ordered and hierarchically organized interfacial supramolecular architecture: Au/16-MHA/EG3SH/amine-PEG3-biotin/avidin. The electrode was then exposed to serum samples at different concentrations of a sandwich-type immunocomplex molecule ((Btn)Ab-AgPSA-(HRP)Ab), and its interfacial properties were characterized using electrochemical impedance spectroscopy (EIS). Calibration curves for polarization resistance (RP) and capacitance (1/C) vs. total and free PSA concentrations were obtained and their analytical quality parameters were determined. This approach was compared with results obtained from a commercially available ELISA immunosensor. The results obtained in this work showed that the proposed immunosensor can be successfully applied to analyze serum samples of patients representative of the Mexican population.

Current biomarkers for diagnosing of prostate cancer

Prostate cancer (PCa) is mostly detected by prostate-specific antigen (PSA) as one of the most widely used tumor markers. But PSA is limited with its low specificity. The prostate health index (phi) can improve specificity over percent free and total PSA and correlates with aggressive cancer. The urinary PCA3 also shows its utility to detect PCa but its correlation with aggressiveness and the low sensitivity at high values are limitations. While the detection of alterations of the androgen-regulated TMPRSS2 and ETS transcription factor genes in tissue of ˜50% of all PCa patients was one research milestone, the urinary assay should only be used in combination with PCA3. Both US FDA-approved markers phi and PCA3 perform equally.

Combination of Autoantibody Signature with PSA Level Enables a Highly Accurate Blood-Based Differentiation of Prostate Cancer Patients from Patients with Benign Prostatic Hyperplasia

Although an increased level of the prostate-specific antigen can be an indication for prostate cancer, other reasons often lead to a high rate of false positive results. Therefore, an additional serological screening of autoantibodies in patients’ sera could improve the detection of prostate cancer. We performed protein macroarray screening with sera from 49 prostate cancer patients, 70 patients with benign prostatic hyperplasia and 28 healthy controls and compared the autoimmune response in those groups. We were able to distinguish prostate cancer patients from normal controls with an accuracy of 83.2%, patients with benign prostatic hyperplasia from normal controls with an accuracy of 86.0% and prostate cancer patients from patients with benign prostatic hyperplasia with an accuracy of 70.3%. Combining seroreactivity pattern with a PSA level of higher than 4.0 ng/ml this classification could be improved to an accuracy of 84.1%. For selected proteins we were able to confirm the differential expression by using luminex on 84 samples. We provide a minimally invasive serological method to reduce false positive results in detection of prostate cancer and according to PSA screening to distinguish men with prostate cancer from men with benign prostatic hyperplasia.

The percentage of prostate-specific antigen (PSA) isoform [-2]proPSA and the Prostate Health Index improve the diagnostic accuracy for clinically relevant prostate cancer at initial and repeat biopsy compared with total PSA and percentage free PSA in men aged ≤65 years

OBJECTIVES

To prospectively test the diagnostic accuracy of the percentage of prostate specific antigen (PSA) isoform [-2]proPSA (%p2PSA) and the Prostate Health Index (PHI), and to determine their role for discrimination between significant and insignificant prostate cancer at initial and repeat prostate biopsy in men aged ≤65 years.

PATIENTS AND METHODS

The diagnostic performance of %p2PSA and PHI were evaluated in a multicentre study. In all, 769 men aged ≤65 years scheduled for initial or repeat prostate biopsy were recruited in four sites based on a total PSA (t-PSA) level of 1.6-8.0 ng/mL World Health Organization (WHO) calibrated (2-10 ng/mL Hybritech-calibrated). Serum samples were measured for the concentration of t-PSA, free PSA (f-PSA) and p2PSA with Beckman Coulter immunoassays on Access-2 or DxI800 instruments. PHI was calculated as (p2PSA/f-PSA × √t-PSA). Uni- and multivariable logistic regression models and an artificial neural network (ANN) were complemented by decision curve analysis (DCA).

RESULTS

In univariate analysis %p2PSA and PHI were the best predictors of prostate cancer detection in all patients (area under the curve [AUC] 0.72 and 0.73, respectively), at initial (AUC 0.67 and 0.69) and repeat biopsy (AUC 0.74 and 0.74). t-PSA and %f-PSA performed less accurately for all patients (AUC 0.54 and 0.62). For detection of significant prostate cancer (based on Prostate Cancer Research International Active Surveillance [PRIAS] criteria) the %p2PSA and PHI equally demonstrated best performance (AUC 0.70 and 0.73) compared with t-PSA and %f-PSA (AUC 0.54 and 0.59). In multivariate analysis PHI we added to a base model of age, prostate volume, digital rectal examination, t-PSA and %f-PSA. PHI was strongest in predicting prostate cancer in all patients, at initial and repeat biopsy and for significant prostate cancer (AUC 0.73, 0.68, 0.78 and 0.72, respectively). In DCA for all patients the ANN showed the broadest threshold probability and best net benefit. PHI as single parameter and the base model + PHI were equivalent with threshold probability and net benefit nearing those of the ANN. For significant cancers the ANN was the strongest parameter in DCA.

CONCLUSION

The present multicentre study showed that %p2PSA and PHI have a superior diagnostic performance for detecting prostate cancer in the PSA range of 1.6-8.0 ng/mL compared with t-PSA and %f-PSA at initial and repeat biopsy and for predicting significant prostate cancer in men aged ≤65 years. They are equally superior for counselling patients before biopsy.

Prostate-specific antigen and other serum and urine markers in prostate cancer

Prostate-specific antigen (PSA) is one of the most widely used tumor markers, and strongly correlates with the risk of harboring from prostate cancer (PCa). This risk is visible already several years in advance but PSA has severe limitations for PCa detection with its low specificity and low negative predictive value. There is an urgent need for new biomarkers especially to detect clinically significant and aggressive PCa. From all PSA-based markers, the FDA-approved Prostate Health Index (phi) shows improved specificity over percent free and total PSA. Other serum kallikreins or sarcosine in serum or urine show more diverging data. In urine, the FDA-approved prostate cancer gene 3 (PCA3) has also proven its utility in the detection and management of early PCa. However, some aspects on its correlation with aggressiveness and the low sensitivity at very high values have to be re-examined. The detection of a fusion of the androgen regulated TMPRSS2 gene with the ERG oncogene (from the ETS family), which acts as transcription factor gene, in tissue of ~50% of all PCa patients was one milestone in PCa research. When combining the urinary assays for TMPRSS2:ERG and PCA3, an improved accuracy for PCa detection is visible. PCA3 and phi as the best available PCa biomarkers show an equal performance in direct comparisons.

Aberrant PSA glycosylation--a sweet predictor of prostate cancer

Prostate cancer--the most commonly diagnosed cancer in men worldwide--can have a substantial effect on quality of life, regardless of the route the cancer takes. The serum PSA assay is the current gold standard option for diagnosing prostate cancer. However, a growing body of evidence suggests that PSA screening for prostate cancer results in extensive overdiagnosis and overtreatment. It is increasingly evident that the potential harm from overdiagnosis (in terms of unnecessary biopsies) must be weighed against the benefit derived from the early detection and treatment of potentially fatal prostate cancers. Rapid screening methods have been used to analyse glycosylation patterns on glycoproteins in large cohorts of patients, enabling the identification of a new generation of disease biomarkers. Changes to the expression status of certain glycan structures are now widely thought to be common features of tumour progression. In light of this development, much research has focused on the potential role of altered PSA glycosylation patterns in discriminating between significant and insignificant prostate cancers, with the aim of developing a more reliable diagnostic tool than the current serum PSA test.

Office evaluation of male patients with lower urinary tract symptoms

Lower urinary tract symptoms due to benign prostatic hyperplasia (LUTS/BPH) are one of the most common urologic disorders in men. Accurate history-taking and focused physical examination allows us to diagnose the majority of cases. A better understanding of risk factors helps us tailor our treatment and predict outcomes more accurately. Population studies are crucial in our understanding of LUTS/BPH natural history. Temporary prostatic urethral stents that are used for the management of urinary retention may also be used for evaluation of patients with detrusor hypo-contractility. The use of ultrasound to measure intravesical prostatic protrusion (IPP) and the Doppler study for prostate capsular artery resistive index are promising. Near-infrared spectroscopy (NIRS) examines the tissue oxygenation that may be affected by bladder outlet obstruction. The mathematical algorithm needs some fine-tuning, and its reproducibility is debatable. Serum and urinary biomarkers may help us to diagnose the disorder, and more effectively monitor patients' response to therapy. Among all, IPP is clinically more applicable at this time.

Association of [-2]proPSA with biopsy reclassification during active surveillance for prostate cancer

PURPOSE

Previous studies have suggested an association between [-2]proPSA expression and prostate cancer detection. Less is known about the usefulness of this marker in following patients with prostate cancer on active surveillance. Thus, we examined the relationship between [-2]proPSA and biopsy results in men enrolled in an active surveillance program.

MATERIALS AND METHODS

In 167 men from our institutional active surveillance program we used Cox proportional hazards models to examine the relationship between [-2]proPSA and annual surveillance biopsy results. The outcome of interest was biopsy reclassification (Gleason score 7 or greater, more than 2 positive biopsy cores or more than 50% involvement of any core with cancer). We also examined the association of biopsy results with total prostate specific antigen, %fPSA, [-2]proPSA/%fPSA and the Beckman Coulter Prostate Health Index phi ([-2]proPSA/free prostate specific antigen) × (total prostate specific antigen)(½)).

RESULTS

While on active surveillance (median time from diagnosis 4.3 years), 63 (37.7%) men demonstrated biopsy reclassification based on the previously mentioned criteria, including 28 (16.7%) of whom had reclassification based on Gleason score upgrading (Gleason score 7 or greater). Baseline and longitudinal %fPSA, %[-2]proPSA, [-2]proPSA/%fPSA and phi measurements were significantly associated with biopsy reclassification, and %[-2]proPSA and phi provided the greatest predictive accuracy for high grade cancer.

CONCLUSIONS

In men on active surveillance, measures based on [-2]proPSA such as phi appear to provide improved prediction of biopsy reclassification during followup. Additional validation is warranted to determine whether clinically useful thresholds can be defined, and to better characterize the role of %[-2]proPSA and phi in conjunction with other markers in monitoring patients enrolled in active surveillance.

Multi-center analytical performance evaluation of the Access Hybritech® p2PSA immunoassay

BACKGROUND

Total PSA assays measure both complexed and non-complexed forms of PSA while free PSA assays only measure non-complexed forms. Free PSA is a mixture of isoforms including immature PSA (proPSA) with retained portions of the leader sequence (e.g. [-7], [-4], and [-2]proPSA) and nicked forms (BPSA). ProPSA isoforms in male sera have been associated with prostate cancer. This study characterized the analytical performance of a chemiluminescent immunoassay for [-2]proPSA.

METHODS

The Access Hybritech p2PSA assay is a sandwich immunoassay using an anti-[-2]proPSA monoclonal antibody attached to paramagnetic beads and an anti-PSA monoclonal antibody conjugated to alkaline phosphatase calibrated with recombinant [-2]proPSA. Analytical studies including sensitivity (CLSI EP17-A) and imprecision (CLSI EP5-A2) were performed.

RESULTS

The Access Hybritech p2PSA assay for [-2]proPSA had a dynamic range of 0.5 to 5000 pg/ml. The total CV of the assay was <7% for [-2]proPSA concentrations between 20 and 1000 pg/ml. The LOB was 0.50 pg/ml, LOD 0.69 pg/ml, and LOQ 3.23 pg/ml (20% CV). There was no hook effect up to 15,000 pg/ml. There was a <5% difference between calibrator and reagent lots and no interference from normal serum constituents.

CONCLUSIONS

The Access Hybritech p2PSA assay is a robust immunoassay for the measurement of serum [-2]proPSA.

Benign prostate specific antigen distribution and associations with urological outcomes in community dwelling black and white men

PURPOSE

We describe cross-sectional associations of benign prostate specific antigen with clinical urological measures and examined the risk of future urological outcomes in 2 population based cohorts of black and white men, respectively.

MATERIALS AND METHODS

Two population based cohort studies were established to characterize the natural history of and risk factors for prostate disease progression in white and black male residents of Olmsted County, Minnesota, and Genesee County, Michigan, respectively.

RESULTS

The benign prostate specific antigen distribution was similar in black men at a median of 32.9 pg/ml (25th, 75th percentiles 17.3, 68.0) and white men at a median of 32.2 pg/ml (25th, 75th percentiles 16.6, 68.9, respectively). However, it was much lower than in previous reports. For Olmsted County men in the upper quartile of benign prostate specific antigen there was a fifteenfold increased risk of prostate cancer (HR 14.6, 95% CI 3.1-68.6) and a twofold higher risk of treatment for benign prostatic hyperplasia (HR 2.2, 95% CI 1.2-4.2) after adjusting for age. After additional adjustment for baseline prostate specific antigen the association between benign prostate specific antigen and prostate cancer risk was attenuated but remained almost ninefold higher for men in the upper quartile of benign prostate specific antigen (HR 8.7, 95% CI 1.8-42.4). The twofold higher risk of treatment for benign prostatic hyperplasia also remained after adjusting for baseline prostate specific antigen for men in the upper benign prostate specific antigen quartile (HR 1.9, 95% CI 0.9-4.0).

CONCLUSIONS

Results suggest that increased benign prostate specific antigen may help identify men with prostate cancer and those at risk for benign prostatic hyperplasia treatment.

Immunoassay for the discrimination of free prostate-specific antigen (fPSA) forms with internal cleavages at Lys(₁₄₅) or Lys(₁₄₆) from fPSA without internal cleavages at Lys(₁₄₅) or Lys(₁₄₆)

Total levels of circulating prostate-specific antigen (tPSA) are strongly associated with prostate cancer (PCa) risk and outcome but benign prostate disease is the most frequent cause of a moderately elevated PSA level. Free PSA (fPSA) forms are independently associated with PCa risk and contribute modest diagnostic enhancements above and beyond tPSA alone. We developed an immunoassay for fPSA subfractions containing internal cleavages at Lys(145) or Lys(146) (fPSA-N). The assay was based on blocking intact single-chain fPSA (fPSA-I) with antibody 4D4 which does not detect PSA containing internal cleavages at Lys(145) or Lys(146). We also measured fPSA-N in blood from healthy volunteers and in anti-coagulated plasma from 76 men with or without evidence of PCa at biopsy. The analytical and functional detection limits of this assay were 0.016 ng/mL and 0.10 ng/mL, respectively. The median recovery of male fPSA-N from female plasma was 95.0%. All 12 female samples (average age 28 years) had fPSA-N concentrations at or below the analytical detection limit. The median fPSA-N concentration (0.050 ng/mL) in 9 healthy male volunteers (age<40 years) was below the functional detection limit, 0.420 ng/mL in 27 patients with benign prostate conditions and 0.239 ng/mL in 49 patients with PCa. Deming regression analysis of the patient samples showed that the measured fPSA-N concentrations were generally 23% lower than the previously calculated (fPSA minus fPSA-I) concentrations, likely due to differences in the antibody combinations used. In conclusion, we have developed a sensitive, specific and direct immunoassay for fPSA-N which can be used to study the clinical relevance of this PSA isoform.

Glycan characterization of PSA 2-DE subforms from serum and seminal plasma

Prostate-specific antigen (PSA) two-dimensional electrophoresis (2-DE) subforms (F1-F5) have been described to be altered in prostate cancer (PCa) compared to benign prostatic hyperplasia (BPH). To understand their molecular differences, characterization of these subforms from PCa serum and seminal plasma, namely, at the glycan level, was performed. PSA 2-DE subforms from two serum PCa samples and seminal plasma were analyzed by N-glycan sequencing using high-performance liquid chromatography (HPLC) combined with exoglycosidase array digestions and by mass spectrometry. F1, F2, and F3 subforms showed the same N-glycan pattern, which contained higher levels of sialic acid than the F4 subform, whereas the F5 subform was unglycosylated. When comparing PSA subforms from PCa with seminal plasma, a decrease in sialylation was observed. Furthermore, the analysis of F3, the more abundant PSA subform, showed a higher proportion of alpha 2-3 sialic acid and a decrease in core fucosylated glycans in the PCa sample. These N-glycan changes in PCa PSA subforms highlight the importance of glycosylation as an indicator of PCa disease.

Prostate-specific antigen (PSA) isoform p2PSA in combination with total PSA and free PSA improves diagnostic accuracy in prostate cancer detection

BACKGROUND

Novel markers for prostate cancer (PCa) detection are needed. Total prostate-specific antigen (tPSA) and percent free prostate-specific antigen (%fPSA=tPSA/fPSA) lack diagnostic specificity.

OBJECTIVE

To evaluate the use of prostate-specific antigen (PSA) isoforms p2PSA and benign prostatic hyperplasia-associated PSA (BPHA).

DESIGN, SETTING, AND PARTICIPANTS

Our study included 405 serum samples from the Rotterdam arm of the European Randomised Study of Screening for Prostate Cancer and 351 samples from the Urology Department of Innsbruck Medical University.

MEASUREMENTS

BPHA, tPSA, fPSA, and p2PSA levels were measured by Beckman-Coulter Access Immunoassay. In addition, the Beckman Coulter Prostate Health Index was calculated: phi=(p2PSA/fPSA)×√(tPSA).

RESULTS AND LIMITATIONS

The p2PSA and phi levels differed significantly between men with and without PCa. No difference in BPHA levels was observed. The highest PCa predictive value in both cohorts was achieved by phi with areas under the curve (AUCs) of 0.750 and 0.709, a significant increase compared to tPSA (AUC: 0.585 and 0.534) and %fPSA (AUC: 0.675 and 0.576). Also, %p2PSA (p2PSA/fPSA) showed significantly higher AUCs compared to tPSA and %fPSA (AUC: 0.716 and 0.695, respectively). At 95% and 90% sensitivity, the specificities of phi were 23% and 31% compared to 10% and 8% for tPSA, respectively. In both cohorts, multivariate analysis showed a significant increase in PCa predictive value after addition of p2PSA to a model consisting of tPSA and fPSA (increase in AUC from 0.675 to 0.755 and from 0.581 to 0.697, respectively). Additionally, the specificity at 95% sensitivity increased from 8% to 24% and 7% to 23%, respectively. Furthermore, %p2PSA, phi, and the model consisting of tPSA and fPSA with or without the addition of p2PSA missed the least of the tumours with a biopsy or pathologic Gleason score ≥7 at 95% and 90% sensitivity.

CONCLUSIONS

This study shows significant increases in PCa predictive value and specificity of phi and %p2PSA compared to tPSA and %fPSA. p2PSA has limited additional value in identifying aggressive PCa (Gleason score ≥7).

Differential percentage of serum prostate-specific antigen subforms suggests a new way to improve prostate cancer diagnosis

BACKGROUND

Prostate-specific antigen (PSA) is the tumor marker currently used for prostate cancer (PCa) screening and diagnosis. However, its use is controversial as serum PSA levels are also increased in other non-malignant prostatic diseases such as benign prostatic hyperplasia (BPH). PSA sialic acid content is altered in tumor situation and modifies PSA's isoelectric point (pI). Our goal has been to evaluate serum PSA subforms from PCa and BPH patients by two-dimensional electrophoresis (2-DE) and to investigate whether they could be used to improve PCa diagnosis.

METHODS

PSA from 20 PCa and 20 BPH patients' sera was subjected to a four-step method to obtain serum PSA 2-DE subforms from free PSA (fPSA) plus PSA released from the complex with alpha-1-antichymotrypsin. Relative percentages of PSA spots were quantified and subjected to statistical analysis.

RESULTS

Five PSA subforms (F1, F2, F3, F4, and F5) of different pI were obtained. Relative percentages of F3 (%F3) and F4 (%F4) were different between PCa and BPH groups. %F3 decreased in cancers and this decrease correlated with the cancer stage, while F4 behaved oppositely. These observations were also found when only focusing on the patients within the low total PSA (tPSA) range 2-20 ng/ml.

CONCLUSIONS

%F3 showed a tendency of higher sensitivity and specificity than the currently used tPSA and %fPSA tests. Therefore, %F3 measurement should be investigated in a larger cohort of patients to study whether it could be introduced to improve PCa diagnosis.

A new algorithm in patients with elevated and/or rising prostate-specific antigen level, minor lower urinary tract symptoms, and negative multisite prostate biopsies

Patients with elevated and/or rising prostate-specific antigen (PSA), minor lower urinary tract symptoms (LUTS), and no evidence for prostate cancer on (multiple) extended prostate biopsies are a regularly encountered problem in urological practice. Even now, patients are seen with no objective explanation of this persistent elevated and/or rising PSA. So far, many strategic proposals have been elaborated and published to deal with this specific population including the use of different PSA derivates; applying different biopsy schemes—strategies—biopsy target imaging; diagnostic use of prostate cancer genes; and many more. In this review, we propose a new algorithm in which an urodynamic evaluation should be included since bladder outlet obstruction (BOO) can be expected. Once BOO is confirmed, a transurethral resection of the prostate (TURP) can be offered to these patients. This procedure will result in subjective and biochemical improvement and allows extensive histological examination. Current literature was reviewed with regard to this specific population. This research was performed using the commercially available Medline online search tools and applying the following search terms: “diagnostic TURP”; “elevated PSA”; and “prostate biopsy”. Furthermore, subsequent reference search was executed on retrieved articles.

Benign prostatic hyperplasia-associated free prostate-specific antigen improves detection of prostate cancer in an artificial neural network

OBJECTIVES

To show discriminative power between patients with prostate cancer (PCa) and those with "no evidence of malignancy" using "benign" prostate-specific antigen (bPSA) and the new automated Access benign prostatic hyperplasia-associated (BPHA) research assay within a percent free PSA (%fPSA)-based artificial neural network (ANN) model.

METHODS

The sera from 287 patients with PCa and 254 patients with no evidence of malignancy were measured using the BPHA, total PSA (tPSA), and fPSA assays with Access immunoassay technology, with a 0-10 ng/mL tPSA range. Two ANN models with Bayesian regularization and leave-one-out validation using the 4 input parameters of tPSA, %fPSA, age, and prostate volume and 1 containing BPHA/tPSA were constructed and compared by receiver operating characteristic curve analysis.

RESULTS

The BPHA/tPSA-based ANN reached the significant greatest area under the receiver operating characteristic curve (AUC 0.81; P = .0004 and P = .0024) and best specificity (53.9% and 44.5%) compared with the ANN without BPHA/tPSA (AUC 0.77; specificity 50% and 40.6%) and %fPSA (AUC 0.77; specificity 40.9% and 27.2%) at 90% and 95% sensitivity, respectively. The AUCs for tPSA (0.58), BPHA (0.55), BPHA/fPSA (0.51), prostate volume (0.69), and BPHA/tPSA (0.69) were significantly lower.

CONCLUSIONS

Although BPHA as single marker or ratio to tPSA did not improve the diagnostic performance of %fPSA or tPSA, the incorporation of BPHA/tPSA into an ANN model increased the specificity compared with %fPSA by 13% and 17% at 90% and 95% sensitivity, respectively. Thus, the automated BPHA research assay might improve PCa detection when incorporating this new marker into an ANN.

Biomarkers for benign prostatic hyperplasia progression

Despite the fact that almost all men will develop symptoms associated with benign prostatic hyperplasia within their lifetimes, no molecular markers for the disease or its likelihood to progress have been established. A marker of this type could be used to stratify patients into subpopulations as well as to identify individuals whose disease is most likely to progress. Several molecular biomarkers have high potential to fulfill these needs, although none is currently approved for the clinical setting. The future does look promising as research to find novel biologic biomarkers is progressing while existing markers are optimized and validated for clinical use.

Screening for prostate cancer in 2008 II: the importance of molecular subforms of prostate-specific antigen and tissue kallikreins

CONTEXT

Over the past decades, prostate-specific antigen (PSA), its isoforms, and other members of the tissue kallikrein family have been of continuous interest with regard to early detection and screening for prostate cancer (PCa).

OBJECTIVE

This review strives to give an overview of the possible clinical utilities of these markers, focused on early diagnostics and PCa screening.

EVIDENCE ACQUISITION

Using the Medline database, a literature search was performed on the role of molecular subforms of PSA and other members of the tissue kallikrein family in PCa detection.

EVIDENCE SYNTHESIS

With respect to PSA isoforms, only the combination of the various truncated forms (pPSA) shows additional value over total PSA (tPSA) and free PSA (fPSA) in PCa detection within the range of 2-10 ng/ml tPSA. At a high sensitivity for PCa, the specificity of the ratio of pPSA to fPSA (%pPSA) is, in general, better than that of the ratio of fPSA to tPSA (%fPSA), with a gain of 5-11%. The (-2)pPSA, (-4)pPSA, (-5)pPSA, (-7)pPSA, and benign PSA (BPSA) isoforms generally show no additional value over either pPSA or the existing parameters of tPSA and fPSA. Of the other members of the tissue kallikrein family, most studies on human kallikrein 2 (hK2) show an additional value of the ratio of hK2 to fPSA (%hK2) over %fPSA alone in PCa prediction. Other tissue kallikreins cannot be recommended for diagnosing PCa, due to the lack of additional value over tPSA or fPSA or to insufficient research. Regarding a prognostic role, the value of PSA subforms as well as of other members of the tissue kallikrein family is limited with regard to existing parameters.

CONCLUSIONS

pPSA and hK2 are able to improve PCa diagnosis in the range of 4-10 ng/ml tPSA over the existing variables tPSA and fPSA.

A comprehensive approach toward novel serum biomarkers for benign prostatic hyperplasia: the MPSA Consortium

PURPOSE

Clinical benign prostatic hyperplasia is primarily diagnosed based on a diverse array of progressive lower urinary tract symptoms and is likely distinct from histological benign prostatic hyperplasia, which is detected by the presence of nonmalignant proliferation of prostate cells but may or may not be associated with symptoms. Pharmacological management of lower urinary tract symptoms has emerged as an effective initial treatment for clinical benign prostatic hyperplasia due to the introduction of new drug therapies shown to be effective in recent large clinical trials. Despite advances in symptom management and research into disease pathology, diagnostic strategies for the prediction of benign prostatic hyperplasia progression and response to drug modalities are lacking, and questions remain as to the molecular differences underlying clinical (symptomatic) vs histological (nonsymptomatic) benign prostatic hyperplasia.

MATERIALS AND METHODS

As part of the Medical Therapy of Prostatic Symptoms (MTOPS) clinical trial, which demonstrated the effectiveness of combination drug therapy in slowing benign prostatic hyperplasia progression, an archive of biological specimens linked to clinical data was collected for future profiling of disease pathology and changes associated with response to drug therapy. The MTOPS Prostatic Samples Analysis (MPSA) Consortium was established to identify and validate molecular markers that may better define benign prostatic hyperplasia related pathologies, identify risk of progression of lower urinary tract symptoms, and predict response to drug therapy using the MTOPS archive. The cooperating MPSA Biomarker Discovery Sites and Pathology Coordinating Center use diverse methodologies and scientific approaches as well as unique expertise to address the goals of the Consortium.

RESULTS

To date the MPSA has identified a number of promising biomarkers as well as other molecular and cellular changes associated with benign prostatic hyperplasia.

CONCLUSIONS

These findings and ongoing Consortium discovery efforts have the potential to provide a greater understanding of the defects underlying disease pathology, and may lead to the development of early and more effective pharmacological treatment strategies for benign prostatic hyperplasia.

Serum markers for prostate cancer: a rational approach to the literature

INTRODUCTION

Due to its universal applicability for early detection and prediction of cancer stage and disease recurrence, widespread implementation of serum-based prostate-specific antigen (PSA) measurements has a significant influence on current treatment strategies for men with prostate cancer (PCa). However, over-detection and the resultant over-treatment of indolent cancers have been strongly implicated to occur. Using current recommended guidelines, the PSA test suffers from both limited sensitivity and specificity to enable efficacious population-based cancer detection. Therefore, novel biomarkers are much needed to complement PSA by enhancing its diagnostic and prognostic performance.

METHODS

The present literature on serum markers for PCa was reviewed. PSA derivatives, molecular PSA isoforms, and novel molecular targets in blood were summarized and weighted against their potential to improve decision-making of men with PCa.

RESULTS

Current evidence suggests that no single analyte is likely to achieve the desired level of diagnostic and prognostic accuracy for PCa. However, the combination of biomarkers with clinical and demographic data, for example, using established standard nomograms, has produced progress toward the goal of both optimal screening and risk assessment. Furthermore, potential candidate molecular markers for PCa can be derived from high-throughput technologies. Current studies demonstrate that understanding dynamic PSA changes over time may offer diagnostic and prognostic information.

CONCLUSIONS

Bridging the gap between basic science and clinical practice represents the main goal in the near future to enable physicians to tailor risk-adjusted screening and treatment strategies for current patients with PCa.

PSA and other tissue kallikreins for prostate cancer detection

Prostate cancer is the most common neoplasia of middle-aged men. Prostate specific antigen (PSA) is the first FDA-approved tumour marker for early detection of cancer and it is now in widespread clinical use. The discovery of different PSA molecular forms in serum (free PSA, PSA complexed with various protease inhibitors) in the early 1990s renewed clinical research to enhance the specificity of PSA. Also, the use of a homologous prostate-localised antigen, human glandular kallikrein 2 (KLK2) may further reduce the number of unnecessary prostate biopsies. More recently, promising data is emerging regarding molecular forms of free PSA (proPSA, BPSA, 'intact' PSA) and other members of the expanded human kallikrein family. These new findings may add substantial clinical information for early detection of prostate cancer.

Les formes moléculaires du PSA

Molecular forms of serum PSA (prostate specific antigen) have been developped to improve total PSA sensitivity and specificity in prostate cancer diagnosis and staging. Total PSA is measured in bound (complexed PSA) and unbound (free PSA) molecular forms. Their levels in absolute values and in relation to total PSA (f/t PSA and c/t PSA) have been evaluated. The percentage of free PSA is more specific but less sensitive than tPSA and it is not recommended as a first line diagnostic test. It may be useful as a second-line test, prescribed by the urologist after a first series of negative biopsies. There is general agreement that at high sensitivity, cPSA provides higher specificity compared with tPSA in the gray zone (2-10 ng/ml). Nevertheless the widespread use of tPSA an the small benefit in terms of specificity explains why cPSA is not generally recommanded. Molecular derivates of free PSA have been identified: proPSA (precursor inactive form of PSA), intact PSA (an additionnal form of proPSA that is found intact and inactive), human Kallikrein 2 and BPSA (for benign PSA wich is associated to BPH) have been evaluated. Preliminary studies did not have demonstrate their ability to discriminate between cancer and BPH, and did not define cutoff values.

A preliminary study of JM-27: a serum marker that can specifically identify men with symptomatic benign prostatic hyperplasia

PURPOSE

Benign prostatic hyperplasia is a common disease in men that until recently was considered a single disease with varying symptoms. Our recent analysis has revealed that a molecular marker, JM-27, is able to distinguish at the tissue level between highly symptomatic individuals and those with histological disease. The goal of these studies was to determine if a serum based assay to detect JM-27 could distinguish men with different forms of benign prostatic hyperplasia.

MATERIALS AND METHODS

A serum based enzyme-linked immunosorbent assay was developed using a novel anti-JM-27 monoclonal antibody. The assay was sensitive, detecting JM-27 at the low ng/ml level within the serum. A quantitative measurement of serum JM-27 levels was performed in 68 patients. The patients consisted of 3 groups of 29 patients with asymptomatic benign prostatic hyperplasia (American Urological Association symptom score of 15 or less), 39 with symptomatic benign prostatic hyperplasia (American Urological Association symptom score 16 to 32) and 17 with confirmed prostate cancer. The assay cutoff was determined after a pilot run of samples and applied prospectively.

RESULTS

Using the determined cutoff, serum levels of JM-27 can distinguish between symptomatic and asymptomatic patient sets. The sensitivity and specificity of the assay are 90% and 77%, respectively. The presence of prostate cancer in these men does not appear to alter the marker levels.

CONCLUSIONS

The present study is believed to represent the first characterization of a serum based marker for severe benign prostatic hyperplasia.

Biosensor developments: application to prostate-specific antigen detection

Prostate-specific antigen (PSA) is the best serum marker currently available for the detection of prostate cancer and is the forensic marker of choice for determining the presence of azoospermic semen in some sexual assault cases. Most current assays for PSA detection are processed on large analyzers at dedicated testing sites, which require that samples be sent away for testing. This leads to delays in patient management and increased administration costs. The recent emphasis placed on the need for point-of-care patient management has led to the development of novel biosensor detection strategies that are suitable for the miniaturization of assays for various targets including PSA. This review highlights the current and novel analytical technologies used for PSA detection, which will benefit clinicians, patients and forensic workers in the future.

Marqueurs biologiques du cancer de la prostate

Screening for prostate cancer is currently based on the assessment of blood prostate specific antigen (PSA). Although PSA was shown to be an adequate tool in prostate cancer screening, beginning from 4.0 ng/mL, its specificity is less significant. In men with a PSA between 4.0 and 10 ng/mL its predictive value is low. Therefore, there is a need for new instruments likely to improve the specificity of blood PSA levels between 4.0 and 10 ng/mL and the screening for prostate cancer in subjects with low PSA. Recent data are reviewed.

Characterization of monoclonal antibodies against prostate specific antigen produced by genetic immunization

Prostate specific antigen (PSA) is the most important marker for prostate cancer. Antibodies against minor variants of PSA may be useful in the development of novel diagnostic tests for prostate cancer, but it has been difficult to produce such antibodies by protein immunization. In this study, we have compared the characteristics of monoclonal antibodies (MAbs) obtained by genetic immunization with those obtained by protein immunization. The whole coding region of PSA-cDNA was cloned in a mammalian expression vector pCDNA-3. Six mice were immunized four times by intra-muscular (i.m.) injection of the PSA-pCDNA3 plasmid. The MAbs produced were characterized with respect to subclass, epitope specificity, binding to various molecular forms of PSA and affinity. After intra-muscular injection of DNA, anti-PSA antibodies were detected in the serum of all mice, but the antibody titers were markedly lower than after protein immunization. After fusion of the spleen cells from the mice, five hybridomas producing MAbs to PSA were obtained. The MAbs were of IgG1 and IgG2a isotype and they all recognized equally different forms of free PSA, namely enzymatically active, nicked and proPSA. Epitope mapping showed that these MAbs reacted with the same antigenic regions as those obtained by protein immunization. Thus, genetic immunization leads to production of anti PSA MAbs with similar characteristics to those obtained by immunizing with PSA protein. As applied in the present study, it is less efficient than protein immunization, but it is a useful technique when the antigen is not available in the quantities needed for immunization.

Prostate-specific antigen test in diagnostic evaluation of chronic prostatitis/chronic pelvic pain syndrome

OBJECTIVES

To determine whether prostate-specific antigen (PSA), the percent free PSA, or free PSA isoforms may be used as diagnostic markers for chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS; National Institutes of Health category IIIa and IIIb).

METHODS

We evaluated 421 patients enrolled in the Chronic Prostatitis Cohort Study and 112 age-matched controls. Subjects were stratified by the number of white blood cells (WBCs) in their expressed prostatic secretions and pain as determined by the National Institutes of Health Chronic Prostatitis Symptom Index.

RESULTS

Total PSA, free PSA, and [-2]proPSA ([-2]pPSA) were significantly elevated in those with CP/CPPS compared with controls (mean PSA 1.97 ng/mL versus 1.72 ng/mL, P = 0.03; mean free PSA 0.76 ng/mL versus 0.70 ng/mL, P = 0.01; and [-2]pPSA 2.38 ng/mL versus 1.80 ng/mL, P = 0.04). The percent free PSA was not significantly different between the patients and controls. For those with CP/CPPS, the percent free PSA was significantly lower as the WBC count rose in the expressed prostatic secretions (0 WBCs = 43.29 versus more than 25 WBCs = 26.52; P < .0001). A PSA level of 4.0 ng/mL or greater was found in 10% of patients and 7% of controls (P = 0.03).

CONCLUSIONS

Men with elevated PSA values and CP/CPPS should be treated as one would any other patient screened for prostate cancer with an elevated PSA level. Although PSA, free PSA, and [-2]pPSA were slightly elevated in men with CP/CPPS, the low sensitivity and specificity do not warrant using them as biomarkers for CP/CPPS.

Prognostic value of serum markers for prostate cancer

The incidence of prostate cancer has increased dramatically during the last 10-15 years and it is now the commonest cancer in males in developed countries. The increase is mainly caused by the increasing use of opportunistic screening or case-finding based on the use of prostate-specific antigen (PSA) testing in serum. With this approach, prostate cancer is detected 5-10 years before giving rise to symptoms and on average 17 years before causing the death of the patient. While this has led to detection of prostate cancer at a potentially curable stage, it has also led to substantial overdiagnosis, i.e. detection of cancers that would not surface clinically in the absence of screening. A major challenge is thus to identify the cases that need to be treated while avoiding diagnosing patients who will not benefit from being diagnosed and who will only suffer from the stigma of being a cancer patient. It would be useful to have prognostic markers that could predict which patients need to be diagnosed and which do not. Ideally, it should be possible to measure these markers using non-invasive techniques, i.e. by means of serum or urine tests. As it is very useful for both early diagnosis and monitoring of prostate cancer, PSA is considered the most valuable marker available for any tumor. Although the prognostic value of PSA is limited, measurement of the proportion of free PSA has improved the identification of patients with aggressive disease. Furthermore, the rate of increase in serum PSA reflects tumor growth rate and prognosis but, due to substantial physiological variation in serum PSA, reliable estimation of the rate of PSA increase requires follow-up for at least 2 years. Algorithms based on the combined use of free and total PSA and prostate volume in logistic regression and neural networks can improve the diagnostic accuracy for prostate cancer, and assays for minor subfractions of PSA and other new markers may provide additional prognostic information. Markers of neuroendocrine differentiation are useful for the monitoring of androgen-independent disease and various bone markers are useful in patients with metastatic disease.

Additional use of [-2] precursor prostate-specific antigen and "benign" PSA at diagnosis in screen-detected prostate cancer

OBJECTIVES

To evaluate the adjuvant clinical use of [-2] precursor prostate-specific antigen ([-2]pPSA), which is associated with prostate cancer (PCa), and "benign" PSA, related to benign prostatic hyperplasia, in selecting a treatment strategy in patients with screen-detected PCa.

METHODS

Research-use immunoassays (Beckman Coulter) were used to measure [-2]pPSA, sum [-7, -5, -4, and -2]pPSA, and benign PSA from the frozen serum of participants from the screen arm of the European Randomized Study of Screening for Prostate Cancer, section Rotterdam, diagnosed with PCa with a serum PSA level lower than 15 ng/mL. We compared men with relatively benign PCa (Epstein's criteria; group 1) and men with arbitrarily defined aggressive PCa characteristics (Gleason score greater than 4 + 4 and more than four cores with PCa invasion or pT3C disease; group 2).

RESULTS

The data of 61 patients were evaluated. The median age in both groups was 68 years. Total PSA performed best in a univariate analysis, although in the multivariate analysis, the combination of pPSA and percent free PSA could correctly predict 95.5% of group 1 and 82.4% of group 2. The pPSA and percent free PSA forms remained statistically significant in the multivariate analysis of a subgroup of 30 participants normalized for PSA level and prostate volume; combined they correctly identified 89.5% and 54.5% of patients identified as having relatively favorable and aggressive PCa characteristics, respectively.

CONCLUSIONS

Adjuvant clinical use of pPSA over traditional parameters in selecting treatment strategies for men with PCa cannot yet be definitely determined. However, the promising results in a subgroup analysis warrant further investigation.

Evaluation of precursor prostate-specific antigen isoform ratios in the detection of prostate cancer

OBJECTIVE

Disease-associated isoforms of the prostate-specific antigen (PSA) have recently been identified. We evaluated the efficacy of using precursor isoforms of PSA (pPSA) and their ratios for the detection of prostate cancer.

METHODS

Serum concentrations of [-2], [-4], and [-7]pPSA, BPSA, and free PSA (fPSA) were retrospectively measured in 43 selected men. Of the 43 men, 15 had clinical T2 prostate cancer with ultrasound-estimated prostate volumes (PVs) of >50 cm(3), 13 had clinical T2 prostate cancer with (PVs) <25 cm(3), and 15 were prostate cancer-free with PV >50 cm(3). We calculated sum pPSA ([-2]+[-4]+[-7]pPSA). We also compared the ratios of: free/total PSA, [-2]pPSA/fPSA, [-2]pPSA/BPSA, [-2]pPSA/(fPSA-BPSA), [-2]pPSA/(fPSA-sum pPSA), and [-2]pPSA/{fPSA-(sum pPSA+BPSA)} among these three groups.

RESULTS

The median [-2]pPSA/(fPSA-sum pPSA) ratio was significantly higher in men with prostate cancer with or without large PV compared with men with large PV without prostate cancer. Values for median [-2]pPSA/free PSA ratio were higher in men with prostate cancer with or without large PV compared with men with large PV, and without prostate cancer, but the differences were not statistically significant.

CONCLUSIONS

In this preliminary study, [-2]pPSA/(fPSA-sum pPSA) ratio was not associated with prostate gland volume but was associated with prostate cancer. This ratio may be useful in the detection of prostate cancer, particularly in men with larger glands.