The role of human glandular kallikrein 2 for prediction of pathologically organ confined prostate cancer

Unlocking the mystery associated with infertility and prostate cancer: an update

Male-specific reproductive disorders and cancers have increased intensely in recent years, making them a significant public health problem. Prostate cancer (PC) is the most often diagnosed cancer in men and is one of the leading causes of cancer-related mortality. Both genetic and epigenetic modifications contribute to the development and progression of PC, even though the exact underlying processes causing this disease have yet to be identified. Male infertility is also a complex and poorly understood phenomenon believed to afflict a significant portion of the male population. Chromosomal abnormalities, compromised DNA repair systems, and Y chromosome alterations are just a few of the proposed explanations. It is becoming widely accepted that infertility shares a link with PC. Much of the link between infertility and PC is probably attributable to common genetic defects. This article provides an overview of PC and spermatogenic abnormalities. This study also investigates the link between male infertility and PC and uncovers the underlying reasons, risk factors, and biological mechanisms contributing to this association.

A pre-specified model based on four kallikrein markers in blood improves predictions of adverse pathology and biochemical recurrence after radical prostatectomy

Background

A pre-specified model based on four kallikrein markers in blood, commercially available as 4Kscore, predicts Gleason Grade (GG) 3 + 4 or higher prostate cancer on biopsy. However, sampling error and variation in pathology reporting may miss aggressive disease.

Methods

The 4Kscore was measured in cryopreserved blood from 2330 men obtained before prostatectomy at a single institution between 2002 and 2010. Adverse surgical pathology and biochemical recurrence (BCR) were pre-specified to be assessed in all men, biopsy GG 3 + 3, and 3 + 4.

Results

Adjusted for established clinical predictors, the 4Kscore was significantly associated with adverse pathology (OR 1.49; 95% CI 1.32, 1.67; p < 0.0001). Adding 4Kscore increased discrimination from (AUC) 0.672 to 0.718 and 0.644 to 0.659 within biopsy GG 3 + 3 and 3 + 4, respectively. Higher 4Kscore was associated with higher risk of BCR (HR 1.16, 95% CI 1.06, 1.26; p = 0.001). Adding 4Kscore improved the prediction of BCR (C-index 0.630–0.660) within GG 3 + 3, but not GG 3 + 4.

Conclusions

The 4Kscore can help guide the clinical decision whether additional risk assessment—such as confirmatory biopsy—is needed to decide between active surveillance versus curative therapy. Evidence that the panel could influence management in biopsy GG 3 + 4 is less strong and requires further investigation.

Role of CYP3A5 in Modulating Androgen Receptor Signaling and Its Relevance to African American Men with Prostate Cancer

Androgen receptor signaling is crucial for prostate cancer growth and is positively regulated in part by intratumoral CYP3A5. As African American (AA) men often carry the wild type CYP3A5 and express high levels of CYP3A5 protein, we blocked the wild type CYP3A5 in AA origin prostate cancer cells and tested its effect on androgen receptor signaling. q-PCR based profiler assay identified several AR regulated genes known to regulate AR nuclear translocation, cell cycle progression, and cell growth. CYP3A5 processes several commonly prescribed drugs and many of these are CYP3A5 inducers or inhibitors. In this study, we test the effect of these commonly prescribed CYP3A5 inducers/inhibitors on AR signaling. The results show that the CYP3A5 inducers promoted AR nuclear translocation, downstream signaling, and cell growth, whereas CYP3A5 inhibitors abrogated them. The observed changes in AR activity is specific to alterations in CYP3A5 activity as the effects are reduced in the CYP3A5 knockout background. Both the inducers tested demonstrated increased cell growth of prostate cancer cells, whereas the inhibitors showed reduced cell growth. Further, characterization and utilization of the observation that CYP3A5 inducers and inhibitors alter AR signaling may provide guidance to physicians prescribing CYP3A5 modulating drugs to treat comorbidities in elderly patients undergoing ADT, particularly AA.

Discovery of novel transcripts of the human tissue kallikrein (KLK1) and kallikrein-related peptidase 2 (KLK2) in human cancer cells, exploiting Next-Generation Sequencing technology

Tissue kallikrein, kallikrein-related peptidases (KLKs), and plasma kallikrein form the largest group of serine proteases in the human genome, sharing many structural and functional properties. Several KLK transcripts have been found aberrantly expressed in numerous human malignancies, confirming their prognostic or/and diagnostic values. However, the process of alternative splicing can now be studied in-depth due to the development of Next-Generation Sequencing (NGS). In the present study, we used NGS to discover novel transcripts of the KLK1 and KLK2 genes, after nested touchdown PCR. Bioinformatics analysis and PCR experiments revealed a total of eleven novel KLK transcripts (two KLK1 and nine KLK2 transcripts). In addition, the expression profiles of each novel transcript were investigated with nested PCR experiments using variant-specific primers. Since KLKs are implicated in human malignancies, qualifying as potential biomarkers, the quantification of the presented novel transcripts in human samples may have clinical applications in different types of cancer.

The Use of Biomarkers in Prostate Cancer Screening and Treatment

Prostate cancer screening and diagnosis has been guided by prostate-specific antigen levels for the past 25 years, but with the most recent US Preventive Services Task Force screening recommendations, as well as concerns regarding overdiagnosis and overtreatment, a new wave of prostate cancer biomarkers has recently emerged. These assays allow the testing of urine, serum, or prostate tissue for molecular signs of prostate cancer, and provide information regarding both diagnosis and prognosis. In this review, we discuss 12 commercially available biomarker assays approved for the diagnosis and treatment of prostate cancer. The results of clinical validation studies and clinical decision-making studies are presented. This information is designed to assist urologists in making clinical decisions with respect to ordering and interpreting these tests for different patients. There are numerous fluid and biopsy-based genomic tests available for prostate cancer patients that provide the physician and patient with different information about risk of future disease and treatment outcomes. It is important that providers be able to recommend the appropriate test for each individual patient; this decision is based on tissue availability and prognostic information desired. Future studies will continue to emphasize the important role of genomic biomarkers in making individualized treatment decisions for prostate cancer patients.

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.

Kallikreins as biomarkers for prostate cancer

The introduction of testing for prostate-specific antigen (PSA), a member of the fifteen-gene family of kallikrein-related peptidases and also known as kallikrein-related peptidase 3 (KLK3), in blood has revolutionized both the detection and management of prostate cancer. Given the similarities between PSA and other KLK gene family members along with limitations of PSA as a biomarker for prostate cancer mainly in reference to diagnostic specificity, the potential roles of other members of this gene family as well as PSA derivatives and isoforms in the management of prostate cancer have been studied extensively. Of these, approaches to measure distinct molecular forms of PSA (free, intact, complexed PSA, and pro-PSA) combined with kallikrein-related peptidase 2 (KLK2), also known as hK2, have been considered holding particular promise in enhancing the diagnosis of prostate cancer. Recently, an integrated approach of applying a panel of four kallikrein markers has been demonstrated to enhance accuracy in predicting the risk of prostate cancer at biopsy. This review presents an overview of kallikreins, starting with the past and current status of PSA, summarizing published data on the evaluations of various KLKs as biomarkers in the diagnosis, prognostication, and monitoring of prostate cancer.

Predicting high risk disease using serum and DNA biomarkers

PURPOSE OF REVIEW

To explore several serum and genetic-based biomarkers that may prove useful in following men being managed with active surveillance for localized prostate cancer by predicting those that either have the potential to develop, or already harbor occult high grade disease.

RECENT FINDINGS

There is increasing evidence that serum biomarkers human Kallikrein 2, early prostate cancer antigen, urokinase-type plasminogen activator/urokinase-type plasminogen activator receptor, transforming growth factor-β1 and interleukin-6/interleukin-6 receptor and genetic biomarkers BRCA1 and BRCA2, Phosphatase and tensin homolog, cellular myelocytomatosis oncogene and NKX3.1 may predict for aggressive high grade disease and are identifiable early in prostate carcinogenesis.

SUMMARY

One of the barriers of widespread adoption of active surveillance for low risk, localized prostate cancer is the concern that some patients may harbor occult high-risk disease at diagnosis, or develop more aggressive/noncurable disease not detected by our current well established prognostic factors. This review examines several serum and genetic-based biomarkers that appear to be of value in localized prostate cancer, unlike the vast majority of more established prostate cancer biomarkers that have been validated in far more advanced disease. Although the biomarkers discussed show exciting promise, their clinical utility is unknown, and their role in the active surveillance scenario needs further study.

Prognostic determinants in prostate cancer

Clinical outcomes in prostate cancer are heterogeneous, and given the high prevalence of the disease, there is a pressing need to identify clinically useful markers of prognosis. Many clinical, pathological, molecular, and genetic factors have been investigated in this capacity, although relatively few are routinely used. With a growing understanding of the molecular pathogenesis of prostate cancer, there is the potential that the next generation of makers will prove sufficiently robust to guide the optimal management of men with prostate cancer. Here, we review the various clinical and molecular prognostic determinants in prostate cancer.

Differentiation of lethal and non lethal prostate cancer: PSA and PSA isoforms and kinetics

Prostate-specific antigen (PSA) testing for the early diagnosis of prostate cancer has led to a decrease in cancer mortality. However, the high prevalence of low-grade prostate cancer and its long natural history, competing causes of death in older men and treatment patterns of prostate cancer, have led to dramatic overtreatment of the disease. Improved markers of prostate cancer lethality are needed to reduce the overtreatment of prostate cancer that leads to a reduced quality of life without extending life for a high proportion of men. The PSA level prior to treatment is routinely used in multivariable models to predict prostate cancer aggressiveness. PSA isoforms and PSA kinetics have been associated with more aggressive phenotypes, but are not routinely employed as part of prediction tools prior to treatment. PSA kinetics is a valuable marker of lethality post treatment and routinely used in determining the need for salvage therapy.

Predicting prostate biopsy result in men with prostate specific antigen 2.0 to 10.0 ng/ml using an investigational prostate cancer methylation assay

PURPOSE

The inadequacies of prostate specific antigen testing have created a need for novel markers for prostate cancer screening. The investigational ProCaM™ prostate cancer methylation assay detects aberrant methylation of DNA in cells associated with prostate cancer. We describe a large, prospective, multicenter study done to verify the performance of this assay.

MATERIALS AND METHODS

The assay is designed to detect epigenetic modifications in the 3 markers GSTP1, RARβ2 and APC, which are indicative of prostate cancer. A total of 232 men with cancer and 283 without cancer from 18 clinical sites were evaluated by trained operators at central testing laboratories. Study inclusion criteria were age 40 to 75 years, total prostate specific antigen between 2.0 and 10.0 ng/ml, and a digital rectal examination result. All participants signed an informed consent form and underwent transrectal ultrasound guided needle biopsy with 10 or more cores.

RESULTS

Assay sensitivity was 60%, specificity was 80% and the informative rate was 97%. Assay predictive accuracy was higher than that of age, digital rectal examination, family history, prostate specific antigen, prior negative biopsy and prostate volume (AUC 0.73 vs 0.52 to 0.66, p <0.038). Risk factors plus the assay improved overall predictive power (AUC 0.79, p = 0.001). A man with a positive prostate cancer methylation result was 7.7 times more likely to have high grade cancer.

CONCLUSIONS

The prostate cancer methylation assay correlated with positive biopsy and with Gleason score. This assay has the potential to add value to the biopsy decision making process by improving current prostate cancer screening algorithms to more accurately identify men with prostate cancer.

Exploratory study of a KLK2 polymorphism as a prognostic marker in prostate cancer

OBJECTIVES

An association of a single nucleotide polymorphism (SNP) of the KLK2 gene (rs198977; c.748C>T; R250W) with risk for developing prostate cancer has been observed. We evaluated the role of R250W SNP for prognosis in prostate cancer.

METHODS

The c.748C>T SNP was genotyped from blood DNA of 182 patients after completing initial cancer treatments. For evaluating prognosis of genotype groups, associations were performed with Gleason score (GS) and biochemical recurrence free survival (bRFS) in patients demonstrating PSA-recurrence after initial cancer therapy.

RESULTS

Overall distribution of the CC, CT and TT genotypes for the SNP was 48%, 44% and 8%, respectively. The distribution of high (8-10), moderate (5-7) and low (2-4) GS among the genotype groups was 17%, 74% and 9% for CC group compared to 25%, 74% and 1% for the CT/TT (P=0.04). Median bRFS time for CT/TT group was 36.5 months compared to 44.5 months for the CC group (P=0.16), while genotype groups combined with morphology revealed significantly different bRFS (P=0.004).

CONCLUSIONS

This exploratory analysis in prostate cancer patients revealed the W allele of the KLK2 R250W SNP to be less likely associated with low GS morphology. Further studies will be needed to confirm this observation in larger cohorts.

Evaluation of molecular forms of prostate-specific antigen and human kallikrein 2 in predicting biochemical failure after radical prostatectomy

Most pretreatment risk-assessment models to predict biochemical recurrence (BCR) after radical prostatectomy (RP) for prostate cancer rely on total prostate-specific antigen (PSA), clinical stage, and biopsy Gleason grade. We investigated whether free PSA (fPSA) and human glandular kallikrein-2 (hK2) would enhance the predictive accuracy of this standard model. Preoperative serum samples and complete clinical data were available for 1,356 patients who underwent RP for localized prostate cancer from 1993 to 2005. A case-control design was used, and conditional logistic regression models were used to evaluate the association between preoperative predictors and BCR after RP. We constructed multivariable models with fPSA and hK2 as additional preoperative predictors to the base model. Predictive accuracy was assessed with the area under the ROC curve (AUC). There were 146 BCR cases; the median follow up for patients without BCR was 3.2 years. Overall, 436 controls were matched to 146 BCR cases. The AUC of the base model was 0.786 in the entire cohort; adding fPSA and hK2 to this model enhanced the AUC to 0.798 (p=0.053), an effect largely driven by fPSA. In the subgroup of men with total PSA<or=10 ng/ml (48% of cases), adding fPSA and hK2 enhanced the AUC of the base model to a similar degree (from 0.720 to 0.726, p=0.2). fPSA is routinely measured during prostate cancer detection. We suggest that the role of fPSA in aiding preoperative prediction should be investigated in further cohorts.

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.

The Tissue Kallikrein Family of Serine Proteases: Functional Roles in Human Disease and Potential as Clinical Biomarkers

Prostate specific antigen (PSA) or human kallikrein 3 (hK3) has long been an effective biomarker for prostate cancer. Now, other members of the tissue kallikrein (KLK) gene family are fast becoming of clinical interest due to their potential as prognostic biomarkers. particularly for hormone dependent cancers. The tissue kallikreins are serine proteases that are encoded by highly conserved multi-gene family clusters in rodents and humans. The rat and mouse loci contain 10 and 25 functional genes, respectively, while the human locus at 19q 13.4 contains 15 genes. The structural organization and size of these genes are similar across species; all genes have 5 coding exons that encode a prepro-enzyme. Although the physiological activators of these zymogens have not been described, in vitro biochemical studies show that some kallikreins can auto-activate and others can activate each other, suggesting that the kallikreins may participate in an enzymatic cascade similar to that of the coagulation cascade. These genes are expressed, to varying degrees, in a wide range of tissues suggesting a functional involvement in a diverse range of physiological and pathophysiological processes. These include roles in normal skin desquamation and psoriatic lesions, tooth development, neural plasticity, and Alzheimer's disease (AD). Of particular interest is the expression of many kallikreins in prostate, ovarian, and breast cancers where they are emerging as useful prognostic indicators of disease progression.

Impact of cytogenetic and genomic aberrations of the kallikrein locus in ovarian cancer

The tissue kallikrein (KLK) genes are a new source for biomarkers in ovarian cancer. However, there has been no systematic analysis of copy number and structural rearrangements related to their protein expression. Chromosomal rearrangements and copy number changes of the KLK region were studied by FISH with protein levels measured by ELISA. Ovarian cancer and cell lines revealed the KLK region was subject to copy number imbalances or involved in unbalanced translocations and were associated with increased protein expression of KLKs 5, 6, 7, 8, 9, 10 and 11. In this initial study, we introduce the potential for long-range chromosomal effects and copy number as a mechanism for the previously reported aberrant expression of many KLK genes in ovarian cancers.

Blood biomarkers for prostate cancer detection and prognosis

Prostate cancer is the most non-cutaneous malignancy diagnosed in men in the USA. The discovery of prostate-specific antigen (PSA) revolutionized prostate cancer diagnosis and management in the 1990s. Despite its remarkable performance as a marker for prostate cancer, PSA is not prostate cancer specific. PSA can be released by normal as well as hyperplastic prostate cells, which undermines the specificity of PSA for prostate cancer diagnosis. Hence, there is a need for new biomarkers that can detect prostate cancer and, in addition, distinguish indolent from biologically aggressive cancers. Moreover, the emergence of new therapeutic approaches for prostate cancer cannot flourish without a more reliable set of markers to serve as prognosticators, targets and surrogate end points of disease progression and response to treatment. As the most useful clinical biomarkers are likely to be those assayed from blood, there is an increasing interest in profiling blood proteins. With recent advances in biotechnology such as high-throughput molecular analyses, many potential blood biomarkers have been identified and are currently under investigation.

New blood-based biomarkers for the diagnosis, staging and prognosis of prostate cancer

The introduction of prostate-specific antigen (PSA) has revolutionized the detection and management of patients with prostate cancer. Despite this there has always been a concern among clinicians about the usefulness of total PSA levels as a marker for prostate cancer. We discuss the use of calculated variables and molecular forms of PSA. The precursor forms of PSA have been associated with the presence and biological behaviour of prostate cancer. With recent advances in biotechnology, e.g. high-throughput molecular analyses, many potential blood biomarkers have been identified and are currently under investigation. Given the plethora of candidate biomarkers we discuss a selected group of novel blood-based biomarkers, e.g. human glandular kallikrein, early prostate cancer antigen, insulin-like growth factors, urokinase plasminogen activators, transforming growth factor-beta, interleukin-6, chromogranin A, and prostate secretory protein. While these and other markers have shown promise in early-phase studies, no single biomarker is likely to have the appropriate degree of certainty to dictate treatment decisions. Consequently, the future of cancer prognosis might rely on small panels of markers that can accurately predict cancer presence, stage and metastasis, and serve as prognosticators, targets, and/or surrogate endpoints of disease progression and response to therapy.

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.

Kallikrein 4 is a proliferative factor that is overexpressed in prostate cancer

Kallikrein 4 (KLK4) is a member of the human tissue KLK family. Whereas all other KLKs are secreted proteins with extracellular functions, KLK4 is primarily localized to the nucleus, indicating that it has a different function compared with other members of the KLK family. In addition, KLK4 expression is highly enriched in the prostate and is regulated by androgens. Here, we studied the possible functional role of KLK4 in prostate cancer cells and examined its expression at the protein level in prostate cancer specimens. Consistent with its mRNA expression, KLK4 protein is significantly overexpressed in malignant prostate compared with normal prostate. KLK4 expression is predominantly in the nucleus of basal cells in the prostate epithelium in keeping with its distribution in prostate cancer cells in vitro. Furthermore, adenovirus-mediated expression of KLK4 dramatically induces proliferation of prostate cancer cells, at least in part through significant alterations in cell cycle regulatory gene expression. Consistent with these data, small interfering RNA-mediated knockdown of endogenous KLK4 in LNCaP prostate cancer cells inhibits cell growth. These data identify KLK4 as the first member of the KLK family that is a proliferative factor with effects on gene expression and indicate that it may have an important role in prostate cancer development and progression.

hK2 and free PSA, a prognostic combination in predicting minimal prostate cancer in screen-detected men within the PSA range 4-10 ng/ml

OBJECTIVES

The purpose of screening for prostate cancer is to decrease the disease-specific mortality. However not every screen-detected prostate cancer is a threat to the patient's life. The risk of overdetection and subsequent overtreatment in prostate cancer has been recognised. The purpose of this investigation was to evaluate the role of tumour markers total PSA, free PSA, and hK2, and their combinations in predicting minimal prostate cancer.

METHODS

Within the European Randomized Study of Screening for Prostate Cancer (ERSPC), section Rotterdam, The Netherlands, prebiopsy serum samples were analysed for 100 selected men who underwent a radical prostatectomy for their screen-detected prostate cancer. All had a PSA value between 4 and 10 ng/ml prior to diagnosis. Minimal prostate cancer is defined as organ confined, Gleason score </=6 (no Gleason grade 4 or 5), and tumour volume <0.5 ml.

RESULTS

Sera and tumour volumes from 91 men were available for analysis. Minimal prostate cancer was diagnosed in 16.5% of the selected cases. Mean tumour volume was 1.2 ml (range: 0.04-13.5); hK2, the algorithms hK2/fPSA, and hK2/%fPSA have significant correlations with tumour volume. Both algorithms also yielded the best test results in predicting minimal disease with an area under the receiver operator characteristics curve of 82%.

CONCLUSIONS

hK2 and percent free PSA have added prognostic value for the detection of minimal prostate cancer in screen-detected cases within PSA range 4-10 ng/ml. These biomarkers can possibly be used to select less invasive treatment options like active surveillance and to prevent overtreatment.

Intact free prostate-specific antigen and free and total human glandular kallikrein 2. Elimination of assay interference by enzymatic digestion of antibodies to F(ab')2 fragments

Various blood constituents can interfere with immunoassays, usually by binding the Fc portion of antibodies. Our previously developed assays for intact free prostate-specific antigen (PSA), free human kallikrein 2 (hK2), and total hK2 frequently yielded falsely high results despite including an excess of scavenger antibodies. We investigated whether this interference could be eliminated by replacing monoclonal capture or tracer antibodies with F(ab')2 or recombinant Fab fragments. Female heparin plasma samples (n = 1092), which should have negligible PSA and hK2, and male samples (n = 957) were analyzed to identify samples manifesting interference, which then were used to optimize protocols for the immunoassays. We compared original assays (monoclonal antibodies) versus optimized assays (F(ab')2 fragments: denatured mouse IgG added as scavenger) using another set of EDTA plasma (n = 113), heparin plasma (n = 160), and serum samples (n = 171). With the original assays, the frequency of falsely elevated hK2 and intact free PSA was 15 and 13%, respectively. The optimized assays eliminated 70-85% of these falsely elevated results and importantly reduced the magnitude in the remainder. F(ab')2 fragmentation was the most important factor in reducing interference. The optimized intact free PSA, free hK2, and total hK2 assays manifested high accuracy close to the lower limit of detection.

Comparison of Free and Total Forms of Serum Human Kallikrein 2 and Prostate-Specific Antigen for Prediction of Locally Advanced and Recurrent Prostate Cancer

Background: We evaluated the association of total and free forms of serum human kallikrein 2 (hK2) and prostate-specific antigen (PSA) with prostate cancers of unfavorable prognosis.

Methods: We retrospectively measured total PSA (tPSA), free PSA (fPSA), and total hK2 (thK2) in preoperative serum samples from 867 men [and assessed free hK2 (fhK2) measured in 577 of these men] treated with radical prostatectomy for clinically localized prostate cancer. Associations between biomarker concentrations and extracapsular extension, seminal vesicle invasion, and biochemical recurrence (BCR) were evaluated. A subset of patients with PSA ≤10 μg/L, the group most commonly seen in clinical practice in the US, was analyzed.

Results: thK2 was the strongest predictor of extracapsular extension and seminal vesicle invasion (areas under the ROC curve [AUC], 0.662 and 0.719, respectively), followed by tPSA (AUC, 0.654 and 0.663). All biomarkers were significant predictors of BCR. hK2 forms, but not PSA forms, remained highly significant for predicting BCR in the low-PSA group. Combining tPSA, fPSA, and thK2 in a multivariable model improved prediction compared with any biomarker used individually (AUC, 0.711, 0.755, and 0.752 for this combination predicting extracapsular extension, seminal vesicle invasion, and BCR, respectively; P &lt;0.001 for all).

Conclusions: Increased concentrations of hK2 in the blood are significantly associated with unfavorable features of prostate cancer, and thK2 is predictive of locally advanced and recurrent cancer in patients with PSA ≤10 μg/L. Independent of tPSA and fPSA, hK2 predicts unfavorable prognosis.

Molecular markers of prostate cancer

Although prostate-specific antigen (PSA) has evolved as a very useful tool for detection of prostate cancer, there remains an urgent need for more accurate biomarkers to diagnose prostate cancer and predict cancer-related outcomes. Recent advances in the study of proteomics and high throughput techniques have led to the discovery of many potential biomarkers for prostate cancer. This article briefly reviews the current status of PSA testing and discusses several candidate protein biomarkers for prostate cancer, as well as highlighting some recent proteomic discoveries with the potential to supplement or even replace PSA for the diagnosis and prognosis of prostate cancer.

Free and total human glandular kallikrein 2 in patients with prostate cancer

OBJECTIVES

The use of prostate-specific antigen (PSA, hK3) results in the overdiagnosis and overtreatment of prostate cancer. Markers are needed that could identify aggressive, fast-growing tumors and help decide which patients would benefit most from aggressive treatment. Human glandular kallikrein 2 (hK2) could be such a marker. The aim of this study was to test how PSA and hK2 could predict the pathologic stage and grade in a set of patients with clinically organ-confined disease.

METHODS

Heparin plasma was collected from 188 patients who had undergone radical prostatectomy at the Turku University Central Hospital. Total and free PSA, as well as total and free hK2, were measured and the results compared with the pathologic TNM stage, tumor World Health Organization grade, and Gleason score.

RESULTS

Free and total hK2 performed similarly to PSA in their ability to separate groups of patients with different stages or grades. Concentrations of both kallikreins were significantly different in patients with World Health Organization grade 1 cancer compared with grade 2. Neither marker could separate patients with different Gleason scores. Although PSA concentrations increased most between patients with Stage pT2b and those with pT3a, the increase in hK2 was most pronounced between those with Stage pT3a and those with pT3b.

CONCLUSIONS

Although hK2 could not predict the cancer stage or grade better than PSA, changes in the hK2 and PSA concentrations occurred at different points in cancer progression. hK2 may have a role in the prognosis of prostate cancer, but additional studies with longer follow-up are required to determine whether hK2 can help when selecting treatment options.

Is Free/Total PSA Predictive of Pathological Stage and Gleason Score in Patients with Prostate Cancer and Serum PSA ≤10 ng/ml?

INTRODUCTION

To evaluate whether percent free prostate-specific antigen (%-fPSA) could be predictive of pathological stage and Gleason score in patients with prostate cancer (PCa) and serum PSA of 10 ng/ml or less.

MATERIALS AND METHODS

In 100 patients with total PSA<or=10 ng/ml who underwent radical retropubic prostatectomy as primary treatment of PCa, %-fPSA levels in organ-confined vs. non-organ-confined PCa and in patients with Gleason score<or=or>7 were compared.

RESULTS

32 patients had an organ-confined and 68 a locally advanced PCa. Median %-fPSA level was 15%; Gleasonscore was <7 in 49 patients, equal to 7 in 40 and >7 in 11. Median %-fPSA levels in PCa with Gleason score<or=or>7 was 14, 15.5 and 15%, respectively. Multiple logistic regression analysis did not show any correlation between %-fPSA in organ-confined vs. non-organ-confined PCa (p=0.4991) either between Gleason score<7 vs. equal to 7 (p=0.588) or >7 (p=0.547).

CONCLUSIONS

%-fPSA cut-off does not seem to be useful for preoperative staging of patients with PCa and serum PSA<or=10 ng/ml.

Serum human glandular kallikrein 2 (hK2) for distinguishing stage and grade of prostate cancer

BACKGROUND

Human glandular kallikrein (hK2) has been shown to add important information regarding the early detection and staging of prostate cancer. Preliminary analysis pointed out that hK2 may discriminate between pT2 and pT3 tumors, and that hK2 may predict Gleason grade 4/5 cancer volume, better than prostate-specific antigen (PSA) or percent free PSA (%fPSA). We investigated the role of hK2 serum values for predicting pathological stage, grade and Gleason score.

METHODS

Prostate-specific antigen, free PSA and hK2 were measured on 222 untreated prostate cancer patients who had received radical prostatectomy at the Charité Hospital, Berlin, Germany. Pathological work up revealed pT2-cancer in 111 patients and pT3-cancer in 111 patients. Grade 2 was found in 118 patients whereas grade 3 tumors were found in 104 patients.

RESULTS

For pT2 and pT3 patients, the %fPSA (P=0.006), the ratios hK2/fPSA (P=0.08) and hK2xtPSA/fPSA (P=0.002) were all significant different whereas hK2 (P=0.143) and PSA (P=0.1) did not differ. Between grade 2 and grade 3 tumors, the hK2 alone (P=0.27), the %fPSA (P=0.13), the ratios hK2/fPSA (P=0.94) and hK2xtPSA/fPSA (P=0.12) did not separate, whereas PSA (P=0.039) showed a difference. The same relationships were found between the two groups in Gleason score<7 and >or=7. Neither the hK2 ratio, nor % fPSA was different.

CONCLUSION

Human glandular kallikrein was not different between pT2 and pT3, nor between G2 versus G3 or Gleason scores<7 and >or=7 prostate cancer. Together with %fPSA, hK2 may only help to distinguish preoperatively between pT2 and pT3 prostate cancer but cannot add further information.

Risk assessment for biochemical recurrence prior to radical prostatectomy: significant enhancement contributed by human glandular kallikrein 2 (hK2) and free prostate specific antigen (PSA) in men with moderate PSA-elevation in serum

Most models to predict biochemical recurrence (BCR) of prostate cancer use pretreatment serum prostate-specific antigen (PSA), clinical stage and prostate biopsy Gleason grade. We investigated whether human glandular kallikrein 2 (hK2) and free prostate-specific antigen (fPSA) measured in pretreatment serum enhance prediction. We retrospectively measured total PSA (tPSA), fPSA and hK2 in preoperative serum samples from 461 men with localized prostate cancer treated with radical prostatectomy between 1999 and 2001. We developed a regression model to predict BCR using preoperative tPSA, clinical stage and biopsy Gleason grade. We then compared the predictive accuracy of this "base" model with a model with fPSA and hK2 as additional predictors. BCR was observed in 90 patients (20%), including 48 patients with a pretreatment tPSA < or = 14 ng/ml (13%), and 28 patients (10%) with a pretreatment tPSA < or = 10 ng/ml. Overall, the predictive accuracy of the base model (bootstrap-corrected concordance index of 0.813) was not improved after the addition of fPSA or hK2 (0.818). However, for men with moderate tPSA-elevation (tPSA < or = 10 ng/ml), addition of fPSA and hK2 data increased predictive accuracy (from a base model concordance index of 0.756-0.815, p = 0.005). The improvement in accuracy was not sensitive to the threshold for "moderately elevated" PSA. For patients with a moderate tPSA-elevation (tPSA < or = 10 ng/ml), which closely corresponds to concurrent disease demographics, BCR-prediction was enhanced when fPSA and hK2 were added to the conventional model. Measurements of fPSA and hK2 improve on our ability to counsel patients prior to treatment as to their risk of BCR.

High-speed biomarker identification utilizing porous silicon nanovial arrays and MALDI-TOF mass spectrometry

Speed and accuracy are crucial prerequisites in the application of proteomic methods to clinical medicine. We describe a microfluidic-based nanovial array for rapid proteolytic processing linked to MALDI-TOF MS. This microscale format consumes only minute amounts of sample, and it is compatible with rapid bioanalytical protocols and high-sensitivity readouts. Arrays of vials (300 microm in diameter and 25 microm deep), isotropically etched in silicon wafers were electrochemically porosified. Automated picoliter microdispensing was employed for precise fluid handling in the microarray format. Vials were prefilled with trypsin solution, which was allowed to dry. Porosified and nonporosified nanovials were compared for trypsin digestion and subsequent MS identification of three model proteins: lysozyme, alcohol dehydrogenase, and serum albumin at levels of 100 and 20 fmol. In an effort to assess the rapid digestion platform in a context of putative clinical applications, two prostate cancer biomarkers, prostate-specific antigen (PSA) and human glandular kallikrein 2 (hK2), were digested at levels of 100 fmol (PSA), 20 fmol (PSA) and 8 fmol (hK2). All biomarker digestions were completed in less than 30 s, with successful MS identification in the porous nanovial setting.

Translational Crossroads for Biomarkers

A group of investigators met at a Specialized Programs of Research Excellence Workshop to discuss key issues in the translation of biomarker discovery to the development of useful laboratory tests for cancer care. Development and approval of several new markers and technologies have provided informative examples that include more specific markers for prostate cancer, more sensitive tests for ovarian cancer, more objective analysis of tissue architecture and an earlier indication of response to treatment in breast cancer. Although there is no clear paradigm for biomarker development, several principles are clear. Marker development should be driven by clinical needs, including early cancer detection, accurate pretreatment staging, and prediction of response to treatment, as well as monitoring disease progression and response to therapy. Development of a national repository that uses carefully preserved, well-annotated tissue specimens will facilitate new marker development. Reference standards will be an essential component of this process. Both hospital-based and commercial laboratories can play a role in developing biomarkers from discovery to test validation. Partnering of academe and industry should occur throughout the process of biomarker development. The National Cancer Institute is in a unique position to bring together academe, industry, and the Food and Drug Administration to (a) define clinical needs for biomarkers by tumor type, (b) establish analytic and clinical paradigms for biomarker development, (c) discuss ways in which markers from different companies might be evaluated in combination, (d) establish computational methods to combine data from multiple biomarkers, (e) share information regarding promising markers developed in National Cancer Institute-supported programs, and (f) exchange data regarding new platforms and techniques that can accelerate marker development.

Association of free-prostate specific antigen subfractions and human glandular kallikrein 2 with volume of benign and malignant prostatic tissue

BACKGROUND

We investigated the association of different subfractions of prostate specific antigen (PSA) and human glandular kallikrein 2 (hK2), such as total PSA (tPSA), complexed PSA (cPSA), free PSA (fPSA), "single-chain Intact fPSA" (fPSA-I), "multi-chain nicked fPSA" (fPSA-N), and total hK2 with volumes of total prostate gland, transition zone (tz), and prostate cancer (PCa) tissue in patients with benign and malignant prostatic disease.

METHODS

Serum samples were collected from men with negative biopsy (n=164) and PCa (n=252). Total and fPSA were measured using a commercially immunoassay. We measured hK2 and fPSA-I by previously reported in-house research assays specific for hK2 and single-chain, non-cleaved fPSA, respectively. Levels of fPSA-N (=fPSA-fPSA-I) and cPSA (=tPSA-fPSA) were calculated. Total prostate and tz volume were measured using transrectal ultrasound (TRUS); PCa volume was calculated using a computer assisted volumetric program. Association with tz and cancer volumes (CaVols) was performed by linear regression analysis.

RESULTS

All PSA subfractions and hK2 were associated with tz volume in multivariable linear regression analysis. Only hK2, fPSA, and fPSA-N were significantly associated with CaVol in multivariable analysis, fPSA-I seemed to be cancer related.

CONCLUSIONS

The multi-chain fPSA-N subfractions of fPSA may be a valuable predictor of both benign prostate hyperplasia (BPH) and CaVol that is likely to be more useful in predicting tz volumes than CaVols. fPSA-I may provide information on cancer without being influenced by the presence of BPH.

Comparison of predictive accuracy for pathologically organ confined clinical stage T1c prostate cancer using human glandular kallikrein 2 and prostate specific antigen combined with clinical stage and Gleason grade

PURPOSE

Previously human glandular kallikrein 2 (hK2) has been implicated to predict pathologically organ confined prostate cancer (PCa) in patients with stage T2 disease. Now we evaluated the usefulness of hK2, as measured by 2 entirely different immunoassay designs, to enhance the discrimination of pathologically organ from nonorgan confined clinical stage T1c PCa.

MATERIALS AND METHODS

A consecutive series of pretreatment serum from 148 men with clinical stage T1c PCa was used in 2 equally sensitive and specific methods to measure total hK2 with independent reagents and entirely different assay designs. Total prostate specific antigen (tPSA) and free PSA (fPSA) were measured and percent fPSA was calculated. We determined the algorithm, hK2*tPSA/fPSA, from data generated by each hK2 assay, calculated means, medians and ranges for each analyte and algorithm, and calculated the significance of differences on univariate analysis. Using pretreatment PSA, clinical stage and biopsy Gleason grade we then developed a multivariate logistic regression base model to predict organ confined cancer and we compared predictions of the base model supplemented by the different hK2 measurements.

RESULTS

hK2 and hK2 based algorithms obtained by each hK2 assay were significantly different for pT2a/b vs pT3a or greater PCa (p = 0.034 to 0.0001) compared to tPSA (p = 0.06), fPSA (p = 0.90) or percent fPSA (p = 0.059). However, AUC (0.67 to 0.70) calculated by ROC analysis of the 4 models containing hK2 derived information was not significantly larger than that of the base model (AUC = 0.64, p = 0.52).

CONCLUSIONS

The current data confirm that hK2 alone or hK2*tPSA/fPSA measured by 2 immunoassays is significantly lower in men with pT2a/b vs pT3a or greater PCa compared to tPSA, fPSA or percent fPSA on univariate analysis of a validation set of clinical stage T1c prostate cancer treated at an American center of excellence for prostate cancer surgery. However, the incorporation of preoperative hK2 into multiparameter predictive models for pT2 cancers did not increase predictive accuracy in this cohort of men.

Screening for prostate cancer: current recommendations

Recent studies have questioned the efficacy of PSA as a marker for the early detection of prostate cancer, but techniques are being investigated to improve the sensitivity and specificity of screening. It is hoped that new methods can differentiate between lethal and nonlethal cancers, thereby avoiding lead-time bias. Even with the current limitations of PSA, the combination of stage migration seen with screening, the recent Scandinavian study showing decrease of disease progression following surgical extirpation, and the known mortality in patients presenting with advanced disease help support PSA screening for prostate cancer. It is hoped that prospective, randomized, long-term screening studies, such as the PLCO and ERSCP trials, will show improved survival using the admittedly imperfect PSA marker in prostate cancer screening.

Serum pro-prostate specific antigen preferentially detects aggressive prostate cancers in men with 2 to 4 ng/ml prostate specific antigen

PURPOSE

Pro forms of prostate specific antigen (PSA) have been reported to be more cancer specific markers of prostate cancer than total PSA and they also may preferentially detect the more aggressive forms of the disease.

MATERIALS AND METHODS

Research immunoassays with high specificity for pro-PSA forms were used to study 1091 retrospective serum specimens, including 555 with 2 to 4 and 536 with 4 to 10 ng/ml PSA, from men enrolled in prostate cancer screening studies who underwent prostate biopsy.

RESULTS

In the 2 to 4 ng/ml PSA range the ratio of pro- to free-PSA (percent pro-PSA) using a cutoff of 1.8% for recommending prostate biopsy detected 90% of cancers, including 16 of 16 extracapsular tumors and 28 of 29 tumors with a pathology Gleason score of 7 or greater, while avoiding 19% of unnecessary biopsies. Serum percent pro-PSA was significantly increased for Gleason score 7 or greater vs less than 7 (p = 0.0018). In the PSA range of 4 to 10 ng/ml percent pro-PSA had the highest cancer specificity, avoiding 31% of unnecessary biopsies, while detecting 34 of 35 cancers with a pathology Gleason score of 7 or greater and 29 of 31 extracapsular tumors. Neither percent free PSA nor complexed PSA enhanced the detection of aggressive cancers in the 4 to 10 ng/ml PSA range.

CONCLUSIONS

Percent pro-PSA was superior to percent free and calculated complexed PSA for the detection of prostate cancer in the PSA range of 2 to 10 ng/ml and it had selectivity for detecting more aggressive cancers, as indicated by Gleason score 7 or greater and/or extracapsular tumor extension.

Screening for Prostate Cancer

Prostate cancer is a highly prevalent disease in the Western world. In the United States alone, prostate cancer affects approximately 230,000 men and causes the death of 30,000 American men annually. Several theoretical health care measures may be implemented to decrease the morbidity and mortality of any disease. These measures include prevention, screening, improved curative treatment, and the transformation of an acute lethal disease to a chronic, tolerable one. This summary focuses on the screening aspects of prostate cancer.

Early detection of prostate cancer in African-American men through use of multiple biomarkers: human kallikrein 2 (hK2), prostate-specific antigen (PSA), and free PSA (fPSA)

Recent studies have reported enhanced prostate cancer detection in Caucasians with serum human glandular kallikrein 2 (hK2) in combination with total- (tPSA) and free-prostate-specific antigen (fPSA). The purpose of this study is to validate these findings in an African-American patient cohort. A total of 137 African-American men were found by routine screening to have tPSA levels above 2.5 ng/ml or an abnormal digital rectal examination. Sera were drawn prior to biopsy of the prostate and Hybritech PSA, FPSA and hK2 (for research use only, not for use in diagnostic procedures) concentrations were determined on Beckman Coulter's Access immunoanalyzer. These independent variables and the ratios of percent fPSA (%fPSA), hK2/tPSA, hK2/fPSA, and hK2*tPSA/fPSA were compared between cancer and non-cancer groups. In all, 49 of 137 men had prostate cancer. hK2 and its calculated ratios outperformed tPSA on receiver operator characteristic (ROC) analysis, but %fPSA had statistically the highest area under the curve (AUC) at 0.801. When restricting the analysis to only the tPSA range of 4.0-10 ng/ml, hK2/fPSA yielded the highest AUC (0.721). The ratio of hK2/fPSA was also found to increase the positive predictive value (PPV) of the %fPSA ranges less than 10 and 10-25%. %fPSA offered the best performance and highest specificity in prostate cancer detection in African-American males over the entire range of tPSA. hK2/fPSA may offer modest improvement in the tPSA range of 4.0-10 ng/ml. Furthermore, hK2/fPSA can enhance the PPV of low %fPSA values. Therefore, the use of multiple biomarkers may ultimately increase the specificity of prostate cancer screening in African-American men.

Human prostate cancer risk factors

Prostate cancer has the highest prevalence of any nonskin cancer in the human body, with similar likelihood of neoplastic foci found within the prostates of men around the world regardless of diet, occupation, lifestyle, or other factors. Essentially all men with circulating androgens will develop microscopic prostate cancer if they live long enough. This review is a contemporary and comprehensive, literature-based analysis of the putative risk factors for human prostate cancer, and the results were presented at a multidisciplinary consensus conference held in Crystal City, Virginia, in the fall of 2002. The objectives were to evaluate known environmental factors and mechanisms of prostatic carcinogenesis and to identify existing data gaps and future research needs. The review is divided into four sections, including 1) epidemiology (endogenous factors [family history, hormones, race, aging and oxidative stress] and exogenous factors [diet, environmental agents, occupation and other factors, including lifestyle factors]); 2) animal and cell culture models for prediction of human risk (rodent models, transgenic models, mouse reconstitution models, severe combined immunodeficiency syndrome mouse models, canine models, xenograft models, and cell culture models); 3) biomarkers in prostate cancer, most of which have been tested only as predictive factors for patient outcome after treatment rather than as risk factors; and 4) genotoxic and nongenotoxic mechanisms of carcinogenesis. The authors conclude that most of the data regarding risk relies, of necessity, on epidemiologic studies, but animal and cell culture models offer promise in confirming some important findings. The current understanding of biomarkers of disease and risk factors is limited. An understanding of the risk factors for prostate cancer has practical importance for public health research and policy, genetic and nutritional education and chemoprevention, and prevention strategies.

Molecular markers to identify patients at risk for recurrence after primary treatment for prostate cancer

Accurate prognostication is a prerequisite for accurate therapeutics and management of prostate cancer because indolent tumors may require no intervention, whereas aggressive tumors lead to patient mortality. There is a critical need to define these subgroups of patients with prostate cancer differing in clinical outcome. Prognostic nomograms based on clinical data provide useful predictions of clinical states and outcomes, but they need further refinements to improve accuracy and universality. Genomic and proteomic analyses have provided many novel markers that may help define prognostic parameters based on the underlying biology of prostate cancer progression at the molecular level. These molecular markers are likely to augment traditional prognostic modalities by providing a set of molecularly defined and quantifiable variables. Encompassing the genome, transcriptome, and proteome of prostate cancer will likely provide "molecular signatures" that will bridge prognostication, prediction, and treatment in a single continuum.