Serum human glandular kallikrein-2 protease levels predict the presence of prostate cancer among men with elevated prostate-specific antigen

Markers of Toxicity and Response to Radiation Therapy in Patients With Prostate Cancer

The main treatment modalities for localized prostate cancer are surgery and radiation. Surgery removes the whole prostate gland, whereas with radiation therapy the irradiated prostate remains within the patient's body. Biomarkers specific to the prostate gland should become undetectable after surgery, but this is not the case when radiation therapy is used, as residual prostate cells may still be metabolically active. Here, we review the role of tumor markers of toxicity and response to radiation therapy in patients with prostate cancer, including prostate specific antigen, human kallikrein 2, osteopontin, prostate cancer associated 3, citrulline, and others.

Clinical utility of kallikrein-related peptidases (KLK) in urogenital malignancies

Kallikrein-related peptidases (KLK), which represent a major tissue-associated proteolytic system, stand for a rich source of biomarkers that may allow molecular classification, early diagnosis and prognosis of human malignancies as well as prediction of response or failure to cancer-directed drugs. International research points to an important role of certain KLKs in female and male urogenital tract malignancies, in addition to cancers of the lung, brain, skin, head and neck, and the gastrointestinal tract. Regarding the female/male urogenital tract, remarkably, all of the KLKs are expressed in the normal prostate, testis, and kidney whereas the uterus, the ovary, and the urinary bladder are expressing a limited number of KLKs only. Most of the information regarding KLK expression in tumour-affected organs is available for ovarian cancer; all of the 12 KLKs tested so far were found to be elevated in the malignant state, depicting them as valuable biomarkers to distinguish between the normal and the cancerous phenotype. In contrast, for kidney cancer, a series of KLKs was found to be downregulated, while other KLKs were not expressed. Evidently, depending on the type of cancer or cancer stage, individual KLKs may show characteristics of a Janus-faced behaviour, by either expanding or inhibiting cancer progression and metastasis.

Effect of radical prostatectomy on levels of cancer related epitopes in circulating macrophages of patients with clinically localized prostate cancer

OBJECTIVE

Epitopes of the apoptosis related protein DNaseX (Apo10) and the pentose-phosphate-pathway associated protein transketolase-like 1 (TKTL1) have been shown to be increased in circulating macrophages of patients with different cancer types including prostate cancer (PC). So far, the effect of cancer-specific therapies on the levels of these markers in blood samples of patients with PC has not been evaluated yet. The aim of the present study was to prospectively assess the effect of surgical removal of the prostate on levels of Apo10 and TKTL1 in blood macrophages using Epitope Detection In Monocytes (EDIM).

METHODS

We prospectively enrolled 174 patients with clinically localized PC undergoing radical prostatectomy. Peripheral blood was collected preoperatively in all patients and postoperatively in a subgroup of 72 patients. We separately assessed the proportion of CD14/CD16-positive monocytes expressing Apo10 and TKTL1 using flow cytometry. The proportion of positive cells was multiplied by ten to generate a score for Apo10 and TKTL1, separately. Pre- and postoperative scores of Apo10 and TKTL1 were compared. Moreover, results were correlated with clinicopathologic parameters.

RESULTS

In the total cohort, Median preoperative Apo10 and TKTL1 scores were 136 (Range 101-254) and 139 (102-216). In patients who underwent blood collection and testing either pre- and postoperatively (n = 72), median pre- versus postoperative scores were 132 (101-215) versus 103 (70-156) for Apo10 (P < 0.0001) and 140 (102-212) versus 115 (84-187) (P < 0.0001) for TKTL1. Following radical prostatectomy, 56 (77.7%) and 59 (81.9%) patients in the cohort of patients with blood collection before and after prostatectomy showed a decrease of Apo10 and TKTL1 expressing monocytes. TKTL1 and Apo10 did not show any correlation with known histopathologic and clinical risk parameters.

CONCLUSIONS

The present study demonstrates that surgical removal of the primary tumor leads to a significant decrease of Apo10 and TKTL1 expressing macrophages. This observation further encourages studies assessing the optimal clinical utility of EDIM-based detection of Apo10 and TKTL1 in patients with PC.

Novel biomarkers for the detection of prostate cancer

Prostate-specific antigen (PSA) is widely used as a biomarker in the detection of prostate cancer and for decision making regarding treatment options, response to therapy, and clinical follow-up. Despite its widespread use, it is well recognised that PSA has suboptimal performance as a screening tool due to poor specificity, resulting in high negative biopsy rates and potential ‘over-diagnosis’ and ‘over-treatment’ of clinically insignificant cancers. In particular, PSA does not reliably distinguish either cancer from benign prostatic conditions, or ‘clinically significant’ from ‘indolent cancers’, and it is inaccurate in predicting disease burden and response to treatment. There is an urgent demand for novel biomarkers to address these clinical needs. This article provides an update on the novel candidate biomarkers in development, which have shown potential for improving the detection of clinically significant cases of this malignancy.

Human Kallikrein-2, Prostate Specific Antigen and Free- Prostate Specific Antigen in Combination to Discriminate Prostate Cancer from Benign Diseases in Syrian Patients

BACKGROUND

The high incidence of prostate cancer as the most common malignancy in males in many countries raises the question of developing reliable detection tests. The prostate specific antigen (PSA) test is the most widely used for screening for prostate cancer; however, its low specificity elevates the number of unnecessarily biopsies. Serum human kallikrein-2 (hK2) is considered as a promising marker, and especially its ratio to fPSA, for predicting the presence of malignancy to select the best choice referring to biopsy or surveillance. In this study, we investigated the role of hK2 and its combinations with other markers to discriminate prostate cancer from benign diseases in Syrian patients.

MATERIALS AND METHODS

In this prospective oriented cross-sectional cohort study, serum samples were collected from patients referred to many Hospitals in Damascus, Syria, between May 2011 and March 2012, and diagnosed with biopsy proven benign prostate hyperplasia (BPH) or prostate cancer (PCa). Serum was analyzed for hK2, PSA and fPSA, and the ratios of fPSA/PSA and hK2/fPSA were calculated.

RESULTS

We found that mean hK2/fPSA ratios were significantly higher (P=0.01) in prostate cancer patients than in the BPH or control groups. Also the ratio hk2/fPSA gave the largest area under the curve (AUC:0.96) which was significantly larger than for fPSA/PSA (AUC:0.41) indicative of higher specificity.

CONCLUSIONS

Our results demonstrate that the ratio of hK2/fPSA might be superior to the use of fPSA/PSA alone. The hK2 could be shown to enhance the early detection of prostate cancer; especially the ratio hK2/fPSA improves specificity and hence may reduce the number of negative biopsies.

Kallikreins - The melting pot of activity and function

The human tissue kallikrein and kallikrein-related peptidases (KLKs), encoded by the largest contiguous cluster of protease genes in the human genome, are secreted serine proteases with diverse expression patterns and physiological roles. Because of the broad spectrum of processes that are modulated by kallikreins, these proteases are the subject of extensive investigations. This review brings together basic information about the biochemical properties affecting enzymatic activity, with highlights on post-translational modifications, especially glycosylation. Additionally, we present the current state of knowledge regarding the physiological functions of KLKs in major human organs and outline recent discoveries pertinent to the involvement of kallikreins in cell signaling and in viral infections. Despite the current depth of knowledge of these enzymes, many questions regarding the roles of kallikreins in health and disease remain unanswered.

Trp(250) -hK2 is defective in intracellular trafficking and activates the unfolded protein response

hK2, a member of the kallikrein protease family encoded by KLK2, is expressed exclusively in prostate and is a putative adjunct tumor marker for prostate cancer screening. The T allele of rs198977, a single nucleotide polymorphism in exon 5 of KLK2, codes for W-hK2 and is associated with lower serum hK2 levels and higher risk of prostate cancer than the C allele encoding R-hK2. To elucidate the mechanism that underlies this SNP's function, we transfected plasmids expressing R-hK2 or W-hK2 into PC3, HeLa and HEK293A cells and measured the hK2 level in cell lysates and conditioned media. The level of W-hK2 was lower than R-hK2 in conditioned media but was not different from R-hK2 in cell lysates. W-hK2 was hardly colocalized with Golgi-targeted fluorescent protein whereas R-hK2 colocalized. Reporter assays related to the unfolded protein response (UPR) and phospho-eIF2α immunoblot showed that W-hK2 increased UPR activity more than R-hK2. These results indicated that W-hK2 had a defect in cellular trafficking from the ER to the Golgi complex due to its misfolding and that it activated the UPR, suggesting a mechanism to explain the association of the T allele with higher prostate cancer risk.

The development of nomograms for stratification of men at risk of prostate cancer prior to prostate biopsy

A main limitation of early prostate cancer (PCa) detection due to elevated PSA levels is caused by the low specificity of PSA, which is associated with a high proportion of men detected with nonmalignant findings at first or subsequent prostate biopsy (PBX). Multivariate prediction models, such as nomograms, have been developed, providing a more accurate method to prospectively determine the risk of a positive PBX. Combining established clinical risk factors with novel diagnostic markers of PCa appears promising to further improve predictive accuracy estimates. Ideally, these nomograms should be capable of identifying PCa at PBX without missing men with high-grade PCa, and preventing a significant proportion of men without, or with insignificant, PCa from undergoing PBX. The intention is to reduce disease morbidity and mortality by detecting significant PCa at an early stage, and at the same time to avoid overdiagnosis as well as overintervention.

Human kallikrein-2 gene and protein expression predicts prostate cancer at repeat biopsy

Purpose

The human kallikrein-2 (hK2) protein and two single nucleotide polymorphism (SNPs) (rs2664155, rs198977) of the gene are associated with prostate cancer risk. We examined whether hK2 protein and gene SNPs predict prostate cancer at the time of repeat biopsy.

Methods

We prospectively offered a repeat biopsy to men with a negative prostate biopsy performed for a PSA >4.0 ng/mL or abnormal Digital Rectal Exam (DRE) between 2001–2005. We genotyped and measured serum hK2 levels in 941 men who underwent a repeat prostate biopsy. Logistic regression analyses were conducted to determine the significance of KLK2 SNPs and hK2 levels for predicting cancer at repeat biopsy.

Results

Of the 941 patients, 180 (19.1%) were found to have cancer. The rs198977 SNP was positively associated with cancer at repeat biopsy (OR variant T allele = 1.8, 95% CI: 1.04-3.13, p = 0.049). When combined, the odds ratio for prostate cancer for patients with high hK2 levels and the variant T-allele of rs198977 was 3.77 (95% CI: 1.94-7.32, p < 0.0001), compared to patients with low hK2 levels and the C-allele. The addition of hK2 levels and KLK2 rs198977 to the baseline predictive model did not significantly increase the area under the curve from a baseline model of 0.67 to 0.69 (p = 0.6).

Conclusions

The KLK2 SNP rs198977 was positively associated with hK2 levels and predicts prostate cancer at the time of repeat prostate biopsy. Further characterization of the KLK2 gene will be needed to determine its clinical utility.

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.

Emerging PSA-based tests to improve screening

This article updates advances in prostate cancer screening based on prostate-specific antigen, its derivatives, and human kallikrein markers. Many men are diagnosed with indolent disease not requiring treatment. Although there is evidence of a survival benefit from screening, the numbers needed to screen and treat remain high. There is risk of exposing men to the side effects of treatment for nonthreatening disease. A screening test is needed with sufficiently good performance characteristics to detect disease at an early stage so treatment may be offered with curative intent, while reducing the number of negative or unnecessary biopsies.

Prostate cancer biomarkers: an update

Many aspects of prostate cancer diagnosis and treatment could be greatly advanced with new, effective biomarkers. Prostate-specific antigen (PSA) has multiple weaknesses as a biomarker, such as not distinguishing well between cancer and benign prostatic hyperplasia or between indolent and aggressive cancers, thus leading to overtreatment, especially unnecessary biopsies. PSA also often fails to indicate accurately which patients are responding to a given treatment. Yet PSA is the only prostate cancer biomarker routinely used by urologists. Here, we provide updated information on the most relevant of the other biomarkers currently in use or in development for prostate cancer. Recent research shows improvement over using PSA alone by comparing total PSA (tPSA) or free PSA (fPSA) with new, related markers, such as prostate cancer antigen (PCA) 3, the individual molecular forms of PSA (proPSA, benign PSA, and intact PSA), and kallikreins other than PSA. Promising results have also been seen with the use of the fusion gene TMPRSS2:ERG and with various forms of the urokinase plasminogen activation receptor. Initially, there were high hopes for early PCA, but those data were not reproducible and thus research on early PCA has been abandoned. Much work remains to be done before any of these biomarkers are fully validated and accepted. Currently, the only markers discussed in this paper with Food and Drug Administration-approved tests are PCA 3 and an isoform of proPSA, [-2]proPSA. Assays are in development for most of the other biomarkers described in this paper. While the biomarker validation process can be long and filled with obstacles, the rewards will be great-in terms of both patient care and costs to the health care system.

The Kallikrein Panel for prostate cancer screening: its economic impact

BACKGROUND

Current diagnostic testing for prostate cancer results in numerous unnecessary biopsy procedures and creates a substantial financial burden. A statistical prediction model for prostate cancer has been developed, based on four Kallikrein markers in blood. This systematic review and meta-analysis examines the aggregated results from published studies of the Kallikrein Panel.

METHODS

Literature searches to identify relevant studies were conducted. A meta-analysis of the results was performed using inverse variance, mean difference with corresponding 95% confidence intervals (CI). The results of the meta-analysis were used to assess the Kallikrein Panel's effect on healthcare costs.

RESULTS

The Kallikrein Panel has been evaluated in more than 8,500 patients (2,780 with prostate cancer and 598 with high grade prostate cancer). Meta-analysis demonstrates a statistically significant improvement of 8-10% in predictive accuracy. In addition, 48% to 56% of current prostate biopsies could be avoided. Use of the Kallikrein Panel could result in annual US savings approaching $1 billion.

CONCLUSIONS

The Kallikrein Panel has the potential to improve patient outcomes and reduce costs. The panel provides significantly improved specificity. Because the Kallikrein Panel has been studied in a range of clinical settings, it is a test that could be readily and widely used in practice.

Genetic variation in KLK2 and KLK3 is associated with concentrations of hK2 and PSA in serum and seminal plasma in young men

BACKGROUND

Genetic variants in KLK2 and KLK3 have been associated with increased serum concentrations of their encoded proteins, human kallikrein-related peptidase 2 (hK2) and prostate-specific antigen (PSA), and with prostate cancer in older men. Low PSA concentrations in seminal plasma (SP) have been associated with low sperm motility. To evaluate whether KLK2 and KLK3 genetic variants affect physiological prostatic secretion, we studied the association of SNPs with hK2 and PSA concentrations in SP and serum of young, healthy men.

METHODS

Leukocyte DNA was extracted from 303 male military conscripts (median age 18.1 years). Nine SNPs across KLK2-KLK3 were genotyped. We measured PSA and hK2 in SP and serum using immunofluorometric assays. The association of genotype frequencies with hK2 and PSA concentrations was tested with the Kruskal-Wallis test.

RESULTS

Four KLK2 SNPs (rs198972, rs198977, rs198978, and rs80050017) were strongly associated with hK2 concentrations in SP and serum, with individuals homozygous for the major alleles having 3- to 7-fold higher concentrations than the intermediate concentrations found in other homozygotes and heterozygotes (all P < 0.001). Three of these SNPs were significantly associated with percentage of free PSA (%fPSA) in serum (all P < 0.007). Three KLK3 SNPs showed associations with PSA in SP, and the rs1058205 SNP was associated with total PSA in serum (P = 0.001) and %fPSA (P = 0.015).

CONCLUSIONS

Associations observed in young, healthy men between the SP and serum concentrations of hK2 and PSA and several genetic variants in KLK2 and KLK3 could be useful to refine models of PSA cutoff values in prostate cancer testing.

Emerging clinical importance of the cancer biomarkers kallikrein-related peptidases (KLK) in female and male reproductive organ malignancies

Background

Tumor tissue-associated KLKs (kallikrein-related peptidases) are clinically important biomarkers that may allow prognosis of the cancer disease and/or prediction of response/failure of cancer patients to cancer-directed drugs. Regarding the female/male reproductive tract, remarkably, all of the fifteen KLKs are expressed in the normal prostate, breast, cervix uteri, and the testis, whereas the uterus/endometrium and the ovary are expressing a limited number of KLKs only.

Conclusions

Most of the information regarding elevated expression of KLKs in tumor-affected organs is available for ovarian cancer; depicting them as valuable biomarkers in the cancerous phenotype. In contrast, for breast cancer, a series of KLKs was found to be downregulated. However, in breast cancer, KLK4 is elevated which is also true for ovarian and prostate cancer. In such cases, selective synthetic KLK inhibitors that aim at blocking the proteolytic activities of certain KLKs may serve as future candidate therapeutic drugs to interfere with tumor progression and metastasis.

Molecular diagnosis of prostate cancer: are we up to age?

Prostate cancer (PCa), a highly heterogeneous disease, is the one of the leading cause of morbidity and mortality in the developed countries. Historically used biomarkers such as prostatic acid phosphatase (PAP), serum prostate-specific antigen (PSA), and its precursor have not stood the challenge of sensitivity and specificity. At present, there is need to re-evaluate the approach to diagnose and monitor PCa. To this end, molecular markers that can accurately identify men with PCa at an early stage, and those who would benefit from early therapeutic intervention, are the need of the hour. There has been unprecedented progress in the development of new PCa biomarkers through advancements in proteomics, tissue DNA and protein/RNA microarray, identification of microRNA, isolation of circulating tumor cells, and tumor immunohistochemistry. This review will examine the current status of prostate cancer biomarkers with emphasis on emerging biomarkers by evaluating their diagnostic and prognostic potentials.

Assays for prostate cancer : changing the screening paradigm?

Prostate cancer (PCa) screening and detection have changed dramatically since the introduction of serum prostate-specific antigen (PSA) testing. Despite the resulting improvement in early PCa detection and stage migration, in clinical practice the use of PSA testing may cause overdetection and ultimately overtreatment. As a consequence, novel biomarkers are needed to increase the specificity of PCa detection. The aim of this article is to present an overview of novel blood- and urine-based biomarkers that may optimize PCa detection, with improved identification of patients with significant PCa and avoidance of unnecessary prostate biopsies. A systematic and comprehensive PubMed search was performed using the MeSH search terms 'prostate cancer', 'biomarker', 'marker', and 'detection'. Results were restricted to the English language. Several blood- and urine-based biomarkers have the potential to improve prediction of the presence and/or significance of PCa. Ideally, biomarkers should be used in combination within multivariate models, leading to superior accuracy for prediction of any PCa or clinically significant PCa, compared with the use of a single marker.

Defining prostate cancer risk before prostate biopsy

Prostate cancer is the most commonly diagnosed cancer in men. At present, patients are selected for prostate biopsy on the basis of age, serum prostate specific antigen (PSA), and prostatic digital rectal examination (DRE) findings. However, due to limitations in the use of PSA and DRE, many patients undergo unnecessary prostate biopsy. A further problem arises as many patients are diagnosed and treated for indolent disease. This review of the literature highlights the strengths and weaknesses of existing methods of prebiopsy risk stratification and evaluates promising serum, urine, and radiologic prostate cancer biomarkers, which may improve risk stratification for prostate biopsy in the future.

Tumor markers in prostate cancer I: blood-based markers

The introduction of total prostate specific antigen (total PSA) testing in blood has revolutionized the detection and management of men with prostate cancer (PCa). The objective of this review was to discuss the challenges of PCa biomarker research, definition of the type of PCa biomarkers, the statistical considerations for biomarker discovery and validation, and to review the literature regarding total PSA velocity and novel blood-based biomarkers.

METHODS

An English-language literature review of the Medline database (1990 to August 2010) of published data on blood-based biomarkers and PCa was undertaken.

RESULTS

The inherent biological variability of total PSA levels affects the interpretation of any single result. Men who will eventually develop PCa have increased total PSA levels years or decades before the cancer is diagnosed. Total PSA velocity improves predictiveness of total PSA only marginally, limiting its value for PCa screening and prognostication. The combination of PSA molecular forms and other biomarkers improve PCa detection substantially. Several novel blood-based biomarkers such as human glandular kallikrein 2 (hK2), urokinase plasminogen activator (uPA) and its receptor (uPAR), transforming growth factor-beta 1 (TGF-β1); interleukin-6 (IL-6) and its receptor (IL-6R) may help PCa diagnosis, staging, prognostication, and monitoring. Panels of biomarkers that capture the biologic potential of PCa are in the process of being validated for PCa prognostication.

CONCLUSIONS

PSA is a strong prognostic marker for long-term risk of clinically relevant cancer. However, there is a need for novel biomarkers that aid clinical decision making about biopsy and initial treatment. There is no doubt that progress will continue based on the integrated collaboration of researchers, clinicians and biomedical firms.

Tissue kallikrein in cardiovascular, cerebrovascular and renal diseases and skin wound healing

Tissue kallikrein (KLK1) processes low-molecular weight kininogen to produce vasoactive kinins, which exert biological functions via kinin receptor signaling. Using various delivery approaches, we have demonstrated that tissue kallikrein through kinin B2 receptor signaling exhibits a wide spectrum of beneficial effects by reducing cardiac and renal injuries, restenosis and ischemic stroke, and by promoting angiogenesis and skin wound healing, independent of blood pressure reduction. Protection by tissue kallikrein in oxidative organ damage is attributed to the inhibition of apoptosis, inflammation, hypertrophy and fibrosis. Tissue kallikrein also enhances neovascularization in ischemic heart and limb. Moreover, tissue kallikrein/kinin infusion not only prevents but also reverses kidney injury, inflammation and fibrosis in salt-induced hypertensive rats. Furthermore, there is a wide time window for kallikrein administration in protection against ischemic brain infarction, as delayed kallikrein infusion for 24 h after cerebral ischemia in rats is effective in reducing neurological deficits, infarct size, apoptosis and inflammation. Importantly, in the clinical setting, human tissue kallikrein has been proven to be effective in the treatment of patients with acute brain infarction when injected within 48 h after stroke onset. Finally, kallikrein promotes skin wound healing and keratinocyte migration by direct activation of protease-activated receptor 1.

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.

[PSA and hK2 in the diagnosis of prostate cancer]

Serum markers for prostate carcinoma are widely applied for the purpose of early detection of cancer and the differentiation between benign and malignant disease, for the pre-treatment staging of detected prostatic cancers, and for the monitoring of prostate cancer after curative or palliative therapies. Since its discovery in 1979, serum PSA has been the most powerful marker of prostate cancer, but, when used alone, PSA is not sufficiently sensitive or specific to consider it an ideal tool for the early detection or staging of prostate cancer. To optimize the use of PSA, the concepts of PSA velocity, PSA density, and age-related PSA values were developed. Moreover, the molecular forms of PSA, especially the percentage of free PSA, seem to be useful tools for the detection of prostate cancer in men with slightly elevated total PSA. Human kallikrein 2 (hK2), a serine protease closely related to PSA that also is expressed predominantly in the prostate, is a new complementary marker to PSA for early detection of prostate cancer. In this review, we examine PSA testing and its effectiveness in the diagnosis of prostate cancer. Further, we also evaluate recent literature regarding the use of hk2.

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.

A panel of kallikrein markers can reduce unnecessary biopsy for prostate cancer: data from the European Randomized Study of Prostate Cancer Screening in Göteborg, Sweden

BACKGROUND

Prostate-specific antigen (PSA) is widely used to detect prostate cancer. The low positive predictive value of elevated PSA results in large numbers of unnecessary prostate biopsies. We set out to determine whether a multivariable model including four kallikrein forms (total, free, and intact PSA, and human kallikrein 2 (hK2)) could predict prostate biopsy outcome in previously unscreened men with elevated total PSA.

METHODS

The study cohort comprised 740 men in Göteborg, Sweden, undergoing biopsy during the first round of the European Randomized study of Screening for Prostate Cancer. We calculated the area-under-the-curve (AUC) for predicting prostate cancer at biopsy. AUCs for a model including age and PSA (the 'laboratory' model) and age, PSA and digital rectal exam (the 'clinical' model) were compared with those for models that also included additional kallikreins.

RESULTS

Addition of free and intact PSA and hK2 improved AUC from 0.68 to 0.83 and from 0.72 to 0.84, for the laboratory and clinical models respectively. Using a 20% risk of prostate cancer as the threshold for biopsy would have reduced the number of biopsies by 424 (57%) and missed only 31 out of 152 low-grade and 3 out of 40 high-grade cancers.

CONCLUSION

Multiple kallikrein forms measured in blood can predict the result of biopsy in previously unscreened men with elevated PSA. A multivariable model can determine which men should be advised to undergo biopsy and which might be advised to continue screening, but defer biopsy until there was stronger evidence of malignancy.

Expression analysis and clinical utility of L-Dopa decarboxylase (DDC) in prostate cancer

BACKGROUND

L-Dopa decarboxylase (DDC) is a pyridoxal 5'-phosphate-dependent enzyme that was found to be involved in many malignancies. The aim of this study was to investigate the mRNA expression levels of DDC in prostate tissues and to evaluate its clinical utility in prostate cancer (CaP).

METHODS

Total RNA was isolated from 118 tissue specimens from benign prostate hyperplasia (BPH) and CaP patients and a highly sensitive quantitative real-time RT-PCR (qRT-PCR) method for DDC mRNA quantification has been developed using the SYBR Green chemistry. LNCaP prostate cancer cell line was used as a calibrator and GAPDH as a housekeeping gene.

RESULTS

DDC was found to be overexpressed, at the mRNA level, in the specimens from prostate cancer patients, in comparison to those from benign prostate hyperplasia patients (p<0.001). Logistic regression and ROC analysis have demonstrated that the DDC expression has significant discriminatory value between CaP and BPH (p<0.001). DDC expression status was compared with other established prognostic factors, in prostate cancer. High expression levels of DDC were found more frequently in high Gleason's score tumors (p=0.022) as well as in advanced stage patients (p=0.032).

CONCLUSIONS

Our data reveal the potential of DDC expression, at the mRNA level, as a novel biomarker in prostate cancer.

Total and free PSA kinetics in patients without prostate cancer undergoing radical cystoprostatectomy

BACKGROUND

Radical cystoprostatectomy and radical prostatectomy are the two major operations where prostate is totally and radically removed. Radical cystoprostatectomy is usually performed in patients with invasive bladder cancer. The aim of the study was to examine Total PSA, Free PSA, and Free/Total Ratio elimination kinetics after radical cystoprostatectomy.

METHODS

Serum PSA, Free PSA, and Free/Total Ratio were determined preoperatively, at the time of cystoprostatectomy specimen removal and then at 3, 6, 12, 24, 48, 72, and 168 hr, from seven patients with muscle invasive bladder cancer, who underwent radical cystoprostatectomy. Free and Total PSA concentrations were measured with non-competitive immunological procedures. The elimination rates and half-lives of Total, Free PSA and Free/Total Ratio were studied using a nonlinear regression analysis.

RESULTS

Surgical manipulations caused about 1.5-fold increase of PSA, 5-fold increase in Free PSA and 3-fold increase in Free/Total Ratio. PSA and Free PSA followed a biphasic elimination pattern of a rapid exponential (a) phase with a half-life of 4.27 and 2.14 hr and a terminal, nonexponential (b) phase with a half-life of 63 and 173.2 hr, respectively. Free/Total PSA Ratio followed, also, a biphasic kinetic pattern of a rapid exponential decline with a half-life of 3.34 and a terminal non-exponential increase with a doubling time of 43 hr.

CONCLUSIONS

Comparing PSA kinetics after radical cystoprostatectomy with those of radical prostatectomy, it appears that PSA follows the same elimination pattern in both models. In contrast, Free PSA and Free/Total Ratio elimination kinetics' patterns differ between the two surgical models.

A novel transcript from the KLKP1 gene is androgen regulated, down-regulated during prostate cancer progression and encodes the first non-serine protease identified from the human kallikrein gene locus

BACKGROUND

The kallikrein-related (KLK) serine protease, prostate specific antigen is the current marker for prostate cancer (PCa). Other members of the KLK family are also emerging as potential adjunct biomarkers for this disease. Our aim was to identify and characterize novel KLK-related genes with potential as PCa bio-markers.

METHODS

Low stringency DNA screening was coupled with amplification techniques to identify novel sequences. Transcripts were examined by Northern blot, RT-PCR, and in situ hybridization analysis and in silico bioinformatics approaches. Protein characterization was performed by Western blot and confocal microscopy analysis. Gene regulation studies were performed by quantitative PCR and promoter reporter assays.

RESULTS

We identified a novel kallikrein-related mRNA designated KRIP1 (kallikrein-related, expressed in prostate 1) which, together with the recently reported PsiKLK1 and KLK31P transcripts, is transcribed from KLKP1; a gene evolved from, and located within, the KLK locus. Significantly, in contrast to these other non-coding KLKP1 transcripts, the KRIP1 mRNA generates an approximately 18 kDa intracellular protein-the first non-serine protease identified from the KLK locus. KRIP1 mRNA is abundant only in normal prostate and is restricted to cells of epithelial origin in normal and diseased glands. Ligand binding of the androgen receptor increases transcription from the KLKP1 gene. Consistently, KRIP1 mRNA levels are lower in PCa samples compared to benign prostatic hyperplasia.

CONCLUSIONS

Transcription from KLKP1 is reduced as cells de-differentiate on the pathway to malignancy. KLKP1/KRIP1 has potential as a marker of both PCa progression and recent evolutionary events within the KLK locus.

The multiple sclerosis degradome: enzymatic cascades in development and progression of central nervous system inflammatory disease

An array of studies implicate different classes of protease and their endogenous inhibitors in multiple sclerosis (MS) pathogenesis based on expression patterns in MS lesions, sera, and/or cerebrospinal fluid (CSF). Growing evidence exists regarding their mechanistic roles in inflammatory and neurodegenerative aspects of this disease. Proteolytic events participate in demyelination, axon injury, apoptosis, and development of the inflammatory response including immune cell activation and extravasation, cytokine and chemokine activation/inactivation, complement activation, and epitope spreading. The potential significance of proteolytic activity to MS therefore relates not only to their potential use as important biomarkers of disease activity, but additionally as prospective therapeutic targets. Experimental data indicate that understanding the net physiological consequence of altered protease levels in MS development and progression necessitates understanding protease activity in the context of substrates, endogenous inhibitors, and proteolytic cascade interactions, which together make up the MS degradome. This review will focus on evidence regarding the potential physiologic role of those protease families already identified as markers of disease activity in MS; that is, the metallo-, serine, and cysteine proteases.

New circulating biomarkers for prostate cancer

The introduction of prostate-specific antigen (PSA) revolutionized prostate cancer (PCa) screening and ushered the PSA era. However, its use as a screening tool remains controversial and changes in the epidemiology of PCa have strongly limited its prognostic role. Therefore, we need novel approaches to improve our ability to detect PCa and foretell the course of the disease. To improve the specificity of total PSA, several approaches based on PSA derivatives have been investigated such as age-specific values, PSA density (PSAD), PSAD of the transition zone, PSA velocity and assessment of various isoforms of PSA. With recent advances in biotechnology such as high-throughput molecular analyses, many potential blood biomarkers have been identified and are currently under investigation. Given the plethora of candidate PCa biomarkers, we have chosen to discuss a select group of candidate blood-based biomarkers including human glandular kallikrein, early prostate cancer antigens, insulin-like growth factor-I (IGF-I) and its binding proteins (IGFBP-2 and IGFBP-3), urokinase plasminogen activation system, transforming growth factor-beta1, interleukin-6, chromogranin A, prostate secretory protein, prostate-specific membrane antigen, PCa-specific autoantibodies and alpha-methylacyl-CoA racemase. 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 may rely on small panels of markers that can accurately predict PCa presence, stage, metastasis, and serve as prognosticators, targets and/or surrogate end points 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.

PSA and new biomarkers within multivariate models to improve early detection of prostate cancer

This review gives an overview of the use of prostate-specific antigen (PSA) and percent free-PSA (%fPSA)-based artificial neural networks (ANNs) and logistic regression models (LR) to reduce unnecessary prostate biopsies. There is a clear advantage in including clinical data such as age, digital rectal examination and transrectal ultrasound (TRUS) variables like prostate volume and PSA density as additional factors to tPSA and %fPSA within ANNs and LR models. There is also positive impact of tPSA and fPSA assays on the outcome of ANNs. New markers provide additional value within ANNs but to prove their clinical usefulness further testing is necessary.

Variants of the hK2 protein gene (KLK2) are associated with serum hK2 levels and predict the presence of prostate cancer at biopsy

PURPOSE

Increased levels of serum human kallikrein-2 (hK2) and an hK2 gene (KLK2) variant are positively associated for prostate cancer, but the relationships between them remain unclear. We examined five variants of the KLK2 gene to further define its relevance to prostate cancer susceptibility and hK2 levels.

EXPERIMENTAL DESIGN

We genotyped 645 men with biopsy-proven prostate cancer (cases) and 606 males with biopsies negative for prostate cancer (controls) for five additional single nucleotide polymorphisms (SNP) across the KLK2 gene and also tested for serum hK2 levels. These SNPs were identified from sequencing the KLK2 gene among 20 patients with aggressive prostate cancer. Odds ratios (OR) for prostate cancer detection and haplotype analysis were done.

RESULTS

Among the SNPs studied, the A allele of the KLK2-SNP1 (G>A, rs2664155) and the T allele of the KLK2-SNP5 (C>T, rs198977) polymorphisms showed positive associations with prostate cancer, adjusted ORs for KLK2-SNP1 AG and AA genotypes being 1.4 [95% confidence interval (95% CI), 1.2-1.8; P=0.002] and for KLK2-SNP5 TT or CT genotypes being 1.3 (95% CI, 1.1-1.6; P=0.05). Haplotype analyses also revealed a significant association between prostate cancer and the haplotype containing both risk alleles (ACCTT), OR being 5.1 (95% CI, 1.6-6.5; P=0.005). Analysis of serum hK2 revealed hK2 levels to be significantly increased in association with KLK2-SNP1 AA and AG risk genotypes compared with the GG genotype (P=0.001) and also in association with the ACCTT risk haplotype compared with the most common non-risk haplotype (P=0.05).

CONCLUSIONS

These findings suggest a role for the KLK2 gene in prostate cancer susceptibility and imply that this role may be realized at least in part by the induction of increases in hK2 production.

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.

mRNA expression analysis of human kallikrein 11 (KLK11) may be useful in the discrimination of benign prostatic hyperplasia from prostate cancer after needle prostate biopsy

Kallikrein 11 (KLK11,TLSP, hippostatin) is a member of the human kallikrein gene family, which includes PSA,KLK2and 12 other members, all localized on chromosome 19q13.4. The aim of this study was to investigate whetherKLK11expression could be used to discriminate prostate cancer (CaP) from benign prostatic hyperplasia (BPH) in needle prostate biopsies. We analyzed the expression of the prostate-type variant of theKLK11gene in 64 CaP and BPH tissues obtained by transrectal ultrasound-guided needle biopsy. Reverse transcription (RT), PCR and image analysis methodologies were developed and used. Of the 42 BPH tissues examined, only 10 (23.8%) were positive for prostate-typeKLK11expression, while of the 22 CaP patients, 12 (54.5%) wereKLK11-positive (p=0.025). Logistic regression and receiver operating characteristic curve analyses demonstrated thatKLK11expression has a significant discriminatory value (crude odds ratio=3.84,p=0.016; area under the curve, 0.65, 95% CI 0.51–0.80) between CaP and BPH in needle prostate biopsies.

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.

Novel peptide inhibitors of human kallikrein 2

Human kallikrein 2 (hK2) is a serine protease produced by the secretory epithelial cells in the prostate. Because hK2 activates several factors participating in proteolytic cascades that may mediate metastasis of prostate cancer, modulation of the activity of hK2 is a potential way of preventing tumor growth and metastasis. Furthermore, specific ligands for hK2 are potentially useful for targeting and imaging of prostate cancer and for assay development. We have used enzymatically active recombinant hK2 captured by a monoclonal antibody exposing the active site of the enzyme to screen phage display peptide libraries. Using libraries expressing 10 or 11 amino acids long linear peptides, we identified six different peptides binding to hK2. Three of these were shown to be specific and efficient inhibitors of the enzymatic activity of hK2 toward a peptide substrate. Furthermore, the peptides inhibited the activation of the proform of prostate-specific antigen by hK2. Amino acid substitution analyses revealed that motifs of six amino acids were required for the inhibitory activity. These peptides are potentially useful for treatment and targeting of prostate cancer.

Androgen receptor signaling intensity is a key factor in determining the sensitivity of prostate cancer cells to selenium inhibition of growth and cancer-specific biomarkers

Our previous report showed that methylseleninic acid (MSA) significantly decreases the expression of androgen receptor and prostate-specific antigen (PSA) in LNCaP cells. The present study extended the above observations by showing the universality of this phenomenon and that the inhibitory effect of MSA on prostate cancer cell growth and cancer-specific biomarkers is mediated through androgen receptor down-regulation. First, MSA decreases the expression of androgen receptor and PSA in five human prostate cancer cell lines (LNCaP, LAPC-4, CWR22Rv1, LNCaP-C81, and LNCaP-LN3), irrespective of their androgen receptor genotype (wild type versus mutant) or sensitivity to androgen-stimulated growth. Second, by using the ARE-luciferase reporter gene assay, we found that MSA suppression of androgen receptor transactivation is accounted for primarily by the reduction of androgen receptor protein level. Third, MSA inhibition of five androgen receptor-regulated genes implicated in prostate carcinogenesis (PSA, KLK2, ABCC4, DHCR24, and GUCY1A3) is significantly attenuated by androgen receptor overexpression. Fourth, transfection of androgen receptor in LNCaP cells weakened noticeably the inhibitory effect of MSA on cell growth and proliferation. Androgen receptor signaling has been documented extensively to play an important role in the development of both androgen-dependent and -independent prostate cancer. Our finding that MSA reduces androgen receptor availability by blocking androgen receptor transcription provides justification for a mechanism-driven intervention strategy in using selenium to control prostate cancer progression.

Clinical utility of human glandular kallikrein 2 within a neural network for prostate cancer detection

OBJECTIVE

To assess, using artificial neural networks (ANNs), human glandular kallikrein 2 (hK2), prostate-specific antigen (PSA), and percentage free/total PSA (f/tPSA), for discriminating between prostate cancer and benign prostatic hyperplasia (BPH).

MATERIAL AND METHODS

Serum samples from 475 patients with prostate cancer (n = 347) or BPH (n = 128) within the PSA range of 1-20 ng/mL were analysed for tPSA, fPSA and hK2 (research assay, Toronto, Canada). Data were analysed in the ranges of 1-4, 2-4, 4-10, and 2-20 ng/mL tPSA. Back-propagation ANN models with the variables PSA, f/tPSA, and hK2, hK2/fPSA and hK2/(f/tPSA) were constructed. The diagnostic validity was evaluated by receiver-operating characteristic (ROC) curve analysis.

RESULTS

Whereas the median concentration of hK2 was not significantly different between patients with BPH or prostate cancer in any of the tPSA ranges, the f/tPSA, hK2/fPSA and hK2/(f/tPSA), and the hK2-based ANN outputs were always significantly different between patients with prostate cancer or BPH. Using ROC curve comparison, all variables were significantly better than hK2 in all ranges. The hK2-based ANN performed better than f/tPSA except in the 4-10 ng/mL tPSA range. At 90% and 95% sensitivity, the hK2-based ANN was also significantly better than f/tPSA in the 1-4 ng/mL tPSA range. hK2/(f/tPSA) achieved equal results to the hK2-based ANN except in the range 2-20 ng/mL tPSA.

CONCLUSIONS

The hK2-based ANN improves the outcome of f/tPSA but not hK2/(f/tPSA) in almost all analysed subgroups. When comparing the results at 90% and 95% sensitivity the hK2-based ANN only performed significantly better than f/tPSA in the lowest tPSA range. Only in lower tPSA ranges do hK2-based ANNs show an advantage for further improving prostate cancer detection.

Relative concentrations of hK2/PSA mRNA in benign and malignant prostatic tissue

BACKGROUND

Prostate-specific antigen (PSA/KLK3) and human kallikrein 2 (hK2/KLK2) belong to the human kallikrein gene family. These two highly homologous genes are specifically expressed in the prostate under androgen control. Expression of these is regulated by similar mechanisms but changes in their relative expression have been observed in prostate cancer.

METHODS

We determined the relative levels of PSA and hK2 mRNA in benign and malignant prostate tissue using a quantitative reverse transcription-polymerase chain reaction (RT-PCR) method. The mRNA of PSA and hK2 are reverse transcribed and amplified in one reaction with the same primers.

RESULTS

The variation in the ratio of hK2/PSA mRNA was remarkably small, the difference between the highest and lowest values being three-fold. The ratio was significantly higher in WHO grade 2 compared to normal or benign prostatic hyperplasia tissue (P = 0.032 and P = 0.035, respectively) and in grade 3 compared to normal or benign prostatic hyperplasia tissue (P = 0.006 in both).

CONCLUSIONS

The new quantitative RT-PCR technique facilitates very accurate quantitation of the relative mRNA levels of homologous genes. Using this method we have shown that the ratio of hK2/PSA mRNA is higher in cancerous than in benign prostatic tissue.

RM2 antigen (beta1,4-GalNAc-disialyl-Lc4) as a new marker for prostate cancer

Although prostate-specific antigen (PSA) has been widely used for early detection of prostate cancer, PSA has problems with specificity and prediction of pathological stage. Therefore, a new marker for prostate cancer is urgently required. We examined expression of a novel carbohydrate antigen, beta1,4-GalNAc-disialyl-Lc(4), defined by the monoclonal antibody RM2, in prostate cancer using 75 cases of radical prostatectomy specimens. RM2 immunoreactivity was negative to weak in all benign glands, and weak to moderate in high-grade prostatic intraepithelial neoplasia. In prostatic adenocarcinoma, RM2 immunoreactivity was negative to weak (lower expression) in 20 cases, and moderate to strong (higher expression) in 55 cases. A clear difference of RM2 expression level was observed between Gleason patterns 3 and >/=4. Higher expression of RM2 antigen was significantly associated with primary Gleason pattern >/=4, high Gleason score (>/=8), larger tumor volume and advanced tumor stage. Furthermore, 5-year PSA failure-free survival was significantly lower in the higher expression group. However, no significant relationship was observed between RM2 expression level and preoperative serum PSA. Western blot analysis in prostate cancer cell lines PC3 and LNCap revealed that major 49-kDa and minor 39-kDa glycoproteins were common to both cells, but there was an increase of 59- and 125-kDa glycoproteins unique to LNCap and an increase of 88- and 98-kDa glycoproteins unique to PC3. RM2 antigen is a new histological marker for prostate cancer that may reflect the Gleason grading system. Identification of the glycoproteins carrying the RM2 antigen will provide new insights into the properties of prostate cancer.

Variation in patterns of practice in diagnosing screen-detected prostate cancer

OBJECTIVE

To determine the practice pattern of repeat prostate biopsies to detect prostate cancer, as there is growing evidence to support the recommendation that a repeat prostate biopsy should be taken after an initially negative prostate biopsy, the rate of cancer detection then being approximately 30%.

PATIENTS AND METHODS

We examined the practice patterns of taking a repeat prostate biopsy after an initial negative biopsy and the predictors for cancer at repeat biopsy among 1536 patients who had an initial prostate biopsy because of an elevated prostate-specific antigen (PSA) level (>4.0 ng/mL) or abnormal digital rectal examination.

RESULTS

Of the 1536 men, 712 (46.4%) had cancer detected on the first biopsy; of the remaining 824 with no cancer detected, 268 (32.5%) had a repeat biopsy within a year, and 68 of these (25.4%) had cancer detected. Of the cancers detected at repeat biopsy, 31% were high-grade. Men with abnormal histology (prostatic intraepithelial neoplasia or atypia) had an odds ratio of 3.2 (P < 0.001) for having a repeat biopsy. For men with normal initial prostate histology, those with an initial PSA of 10.0-20.0 and >20.0 ng/mL had an odds ratio of 3.6 and 4.5 (both P < 0.001), respectively, for a repeat prostate biopsy, compared with patients with a PSA of <10.0 ng/mL. However, the PSA level was not predictive of prostate cancer at repeat biopsy, but age and prostate volume were.

CONCLUSIONS

A third of patients had a repeat biopsy after a negative biopsy. The most important factors influencing whether a patient was to have a repeat biopsy were initial biopsy histology and PSA level. However, the latter was not an important factor for predicting prostate cancer at repeat biopsy.

Development of sensitive immunoassays for free and total human glandular kallikrein 2

BACKGROUND

Free and total human kallikrein 2 (hK2) might improve the discrimination between prostate cancer and benign prostatic hyperplasia. Concentrations of hK2 are 100-fold lower than concentrations of prostate-specific antigen (PSA); therefore, an hK2 assay must have a low detection limit and good specificity.

METHODS

PSA- and hK2-specific monoclonal antibodies were used in solid-phase, two-site immunofluorometric assays to detect free and total hK2. The total hK2 assay used PSA-specific antibodies to block nonspecific signal. The capture antibody of the free hK2 assay did not cross-react with PSA. To determine the hK2 concentrations in the male bloodstream, total hK2 was measured in a control group consisting of 426 noncharacterized serum samples. Free and total hK2 were measured in plasma from 103 patients with confirmed prostate cancer.

RESULTS

All 426 males in the control group had a total hK2 concentration above the detection limit of 0.0008 microg/L. The median total hK2 concentration was 0.022 microg/L (range, 0.0015-0.37 microg/L). hK2 concentrations were 0.1-58% of total PSA (median, 3.6%). hK2 concentrations were similar in men 41-50 and 51-60 years of age. The ratio of hK2 to PSA steadily decreased from 5-30% at PSA <1 microg/L to 1-2% at higher PSA concentrations. In 103 patients with prostate cancer, the median hK2 concentration in plasma was 0.079 microg/L (range, 0.0015-16.2 microg/L). The median free hK2 concentration was 0.070 (range, 0.005-12.2) microg/L. The proportion of free to total hK2 varied from 17% to 131% (mean, 85%).

CONCLUSIONS

The wide variation in the free-to-total hK2 ratio suggests that hK2 in blood plasma is not consistently in the free, noncomplexed form in patients with prostate cancer. The new assay is sufficiently sensitive to be used to study the diagnostic accuracies of free and total hK2 for prostate cancer.

Immunohistochemical localization of human kallikreins 6, 10 and 13 in benign and malignant prostatic tissues

Human kallikreins 6, 10 and 13 (hK6, hK10 and hK13) are expressed by many normal, mainly glandular tissues, including prostatic epithelium. Some kallikreins may function as tumor suppressors or are downregulated during cancer progression. The aim of this study was to evaluate the immunoexpression of these kallikreins in benign and malignant prostatic tissues and correlate their expression with prostate cancer (PC) prognosis. Included in the study were 25 cases of nonmalignant prostate and 179 cases of PC. Among them, 122 PC cases were immunostained for hK6, 94 for hK10 and 113 for hK13, respectively. The follow-up period for a subset of 68 patients who had undergone radical prostatectomy (RP) was 1-58 months (mean=13.4 +/- 1.7 and median=8.0 months). A cutoff value of 0.2 microg/l of serum PSA was established as a biochemical recurrence threshold. Follow-up information was available for 26/55 RP cases stained for hK6, 14/32 cases stained for hK10 and 25/59 cases stained for hK13. Gleason score (GS) 7 carcinomas were stratified as 7a and 7b, according to the primary grade. PC with GS 2-7a were histologically categorized as low malignant (LM) and PC with GS 7b-10 as high malignant (HM). The immunohistochemical method of streptavidin-biotin-peroxidase using monoclonal and polyclonal antibodies was performed. In the benign prostate and in prostatic intraepithelial neoplasia, a cytoplasmic immunostaining of varying intensity was evident. In PC, the immunoexpression of all kallikreins was decreased: 102/122 cases (84%) were positive for hK6, 73/94 (78%) for hK10 and 97/113 (86%) for hK13, respectively. A statistically significant difference in expression was found, in comparison to nonmalignant prostates (P=0.029, 0.009 and 0.045, respectively). Also, a positive correlation was observed between the immunoexpression of these three kallikreins. Concerning the histological grade, HM-PC expressed all three kallikreins with a slightly higher percentage than LM-PC: 79 vs 88% for hK6, 76 vs 79% for hK10 and 76 vs 92% for hK13. These differences were statistically significant only in the case of hK13 (P=0.024). Serum PSA did not correlate with kallikrein immunoexpression in PC. Furthermore, there was no significant correlation between kallikrein expression and pathological stage or recurrence, in the cases of RP. All three kallikreins are expressed in the nonmalignant and malignant prostate, with cancer tissues demonstrating slightly lower expression. Expression levels did not correlate with aggressiveness and they do not seem to have value for prostate cancer prognosis.

Update of staging and risk assessment for prostate cancer patients

PURPOSE OF REVIEW

This paper will review the current staging system for prostate adenocarcinoma patients, and will also review new information that can be combined with clinical and pathological staging in order to assess a patient's risk of success or failure of treatment.

RECENT FINDINGS

There has been significant stage migration of prostate cancer patients in the past 15 years, such that patients are currently being diagnosed younger, with lower clinical stages and serum prostate-specific antigen levels, and a lower risk of metastatic disease than previously. The incorporation of the results of extended prostate biopsy schemes, with stage, grade and serum prostate-specific antigen levels, improves the risk assessment of newly diagnosed prostate cancer patients. New imaging techniques, such as transrectal ultrasound Doppler flow and magnetic resonance spectroscopy hold promise for improving risk assessment. Molecular biomarkers may improve risk assessment in the future, although none are currently approved by the US Food and Drug Administration for this indication. Gene chip arrays may further refine risk assessment and assist with the identification of therapeutic targets.

SUMMARY

There has been significant stage migration of prostate cancer patients in the prostate-specific antigen era. Incorporating biopsy information into nomograms and risk assessment equations improves upon clinical staging and risk assessment. New imaging techniques, molecular markers and gene chip arrays hold promise for future risk assessment.

Prostate-specific antigen and related isoforms in the diagnosis and management of prostate cancer

Despite its unparalleled merits for prostate cancer detection and staging, prostate-specific antigen (PSA) is not a marker for prostate cancer only, but also is expressed in benign conditions. For early detection, limitations of PSA are obvious. Its widespread use has led to an extensive amount of expensive and often unnecessary diagnostic procedures associated with significant morbidity. Total PSA derivatives may enhance the accuracy of prostate cancer diagnosis. The ratio of free-to-total PSA improves specificity while maintaining a high sensitivity for prostate cancer detection for men with a total PSA of 2.5 to 10 ng/mL. Human glandular kallikrein also has the potential to be a valuable tool in combination with total and free PSA for early diagnosis of prostate cancer. Complex PSA seems to be a reliable tool to improve specificity at high sensitivity levels in men with suspected prostate cancer (mainly in PSA levels below 4 ng/mL). Newly discovered isoforms of free PSA also may impact early detection of prostate cancer with encouraging preliminary results that warrant further clinical investigation.