Growth regulation of prostatic stromal cells by prostate-specific antigen

Effect of Tetragonia tetragonoides (Pall.) Kuntze Extract on Andropause Symptoms

Testosterone and free testosterone levels decrease in men as they age, consequently inducing andropause symptoms, such as weight gain, fatigue, and depression. Therefore, this study aimed to evaluate the reducing effect of New Zealand spinach (NZS) on these androgenic symptoms by orally administering its extract to 26-week-old rats for four weeks. Biochemical blood testing was conducted, and the andropause symptoms-related indicators and muscular endurance levels were examined. In the NZS extract-treated rats, the decrease in muscle mass was suppressed, and immobility time was reduced in the forced swim test. In addition, the grip force and muscular endurance of the forelimbs were significantly increased compared to the control group; therefore, NZS extract exhibits a positive effect on the maintenance of muscle mass and improves muscular endurance. The representative male hormones, testosterone and progesterone, in the NZS extract-treated group were 1.84 times and 2.48 times higher than those in the control groups, respectively. Moreover, cholesterol and low-density lipoprotein, which affect lipid metabolism, were significantly reduced in the NZS extract-treated group. Overall, NZS extract shows potential for further development as a functional food material for improving muscle strength and relieving andropause symptoms.

Remodelling of the tumour microenvironment by the kallikrein-related peptidases

Kallikrein-related peptidases (KLKs) are critical regulators of the tumour microenvironment. KLKs are proteolytic enzymes regulating multiple functions of bioactive molecules including hormones and growth factors, membrane receptors and the extracellular matrix architecture involved in cancer progression and metastasis. Perturbations of the proteolytic cascade generated by these peptidases, and their downstream signalling actions, underlie tumour emergence or blockade of tumour growth. Recent studies have also revealed their role in tumour immune suppression and resistance to cancer therapy. Here, we present an overview of the complex biology of the KLK family and its context-dependent nature in cancer, and discuss the different therapeutic strategies available to potentially target these proteases.

Lower urinary tract symptoms in patients with small prostates: Smooth muscle proliferation and calcification might be causative factors

OBJECTIVES

The current study is designed to evaluate and compare the histological changes in the surgical samples of prostate taken from patients undergoing transurethral resection of prostate (TURP) for benign prostate hyperplasia (BPH) with different sizes.

METHODS

Prostate surgical tissue samples were obtained from BPH patients undergoing TURP after taking informed consent. Ultrasound measure of prostatic weight and prostate-specific antigen (PSA) levels were obtained from the patients along with other clinical and demographic details. Tissue samples were fixed, processed, sectioned and stained with hematoxylin and eosin and Masson's trichrome to look for histological features, specifically smooth muscle proliferation. Immunohistochemical expression of bone morphogenetic protein (BMP)-2 was recorded to assess the calcification potential.

RESULTS

Fifty-nine surgical samples were obtained from the patients of age range 50-90 years and body mass index (BMI) 15.6-33.3 kg/m² . The range of ultrasound measures of prostate weight was 20-137 g with PSA ranged 1.03-93.3 ng/mL. Patients with small-sized prostate had significant severe smooth muscle proliferation (P < .001). Prostate size/weight had significant positive association with BMI (P < 0.001, r = 0.543) and negative association with BMP-2 (P < 0.001, r = -0.654). Samples with severe smooth muscle proliferation were with increased BMP-2 expression (P < .001) and higher levels of PSA levels (P = 0.004). BMP-2 expression revealed positive significant association with PSA (P < .001, r = 0.432).

CONCLUSION

From this study we conclude that BPH patients with small-sized glands and high PSA levels have increased smooth muscle proliferation and calcification potential causing the symptoms of lower urinary tract symptoms in these patients.

Short-term aromatase inhibition induces prostatic alterations in adult wistar rat: A biochemical, histopathological and immunohistochemical study

PURPOSE

This study aimed to evaluate the effects of estrogen reduction on amyloid deposition, some lipid metabolism and oxidative stress markers, PSA-like production and p63 expression in the prostate of the adult rat.

METHODS

Aromatase inhibitor: Formestane (4-OHA), was administrated to male rats, at a dose of 0.1 mg/kg b.w./day, for 10 days. The control group (CONT) received the same volume of placebo injection (NaCl 0.9%).

RESULTS

4-OHA treatment induced a significant accumulation of intraprostatic cholesterol (138.90 ± 17.64 vs 85.12 ± 2.87, p = 0.01); against an insignificant diminution of malondialdehyde (412.6 ± 54.35 vs 842.70 ± 336.50, p > 0.05) and glutathione (2.40 ± 0.23 vs 3.65 ± 0.88, p > 0.05). This was associated with a significant decrease of nitric oxide (31.76 ± 7.07 vs 179.40 ± 58.35, p = 0.024). Additionally, 4-OHA significantly increased the intraprostatic production of PSA-like (11.12 ± 2.78 vs 3.91 ± 0.43, p = 0.043). The prostatic histology revealed an amyloid deposition, in all prostatic lobes and a smooth muscle layer growth (p < 0.05); especially significant in the dorsal and lateral lobes. Theses lobes manifested a basal cells proliferation, with a 3-fold increase of p63 expression (p < 0.001). The ventral lobe presented epithelial atrophy (37.80 ± 16.20 vs 167.60 ± 5.16, p < 0.05); with occasional and significant proliferative foci (247.00 ± 9.573 vs 167.60 ± 5.16 p < 0.05).

DISCUSSION AND CONCLUSION

Aromatase inhibition, in the adult male rat, alters the prostatic function by reducing nitric oxide availability and inducing amyloid deposition along with limiting the differentiation of basal cells, through a lobe-specific p63-overexpression.

E-cadherin is downregulated in benign prostatic hyperplasia and required for tight junction formation and permeability barrier in the prostatic epithelial cell monolayer

BACKGROUND

We previously reported the presence of prostate-specific antigen (PSA) in the stromal compartment of benign prostatic hyperplasia (BPH). Since PSA is expressed exclusively by prostatic luminal epithelial cells, PSA in the BPH stroma suggests increased tissue permeability and the compromise of epithelial barrier integrity. E-cadherin, an important adherens junction component and tight junction regulator, is known to exhibit downregulation in BPH. These observations suggest that the prostate epithelial barrier is disrupted in BPH and E-cadherin downregulation may increase epithelial barrier permeability.

METHODS

The ultra-structure of cellular junctions in BPH specimens was observed using transmission electron microscopy (TEM) and E-cadherin immunostaining analysis was performed on BPH and normal adjacent specimens from BPH patients. In vitro cell line studies using benign prostatic epithelial cell lines were performed to determine the impact of small interfering RNA knockdown of E-cadherin on transepithelial electrical resistance and diffusion of fluorescein isothiocyanate (FITC)-dextran in transwell assays.

RESULTS

The number of kiss points in tight junctions was reduced in BPH epithelial cells as compared with the normal adjacent prostate. Immunostaining confirmed E-cadherin downregulation and revealed a discontinuous E-cadherin staining pattern in BPH specimens. E-cadherin knockdown increased monolayer permeability and disrupted tight junction formation without affecting cell density.

CONCLUSIONS

Our results indicate that tight junctions are compromised in BPH and loss of E-cadherin is potentially an important underlying mechanism, suggesting targeting E-cadherin loss could be a potential approach to prevent or treat BPH.

Kallikrein-related peptidases (KLKs) and the hallmarks of cancer

The kallikrein-related peptidases (KLKs) represent the largest family of serine proteases within the human genome and are expressed in various tissues. Although they regulate several important physiological functions, KLKs have also been implicated in numerous pathophysiological processes, including cancer. Growing evidence describing the deregulation of KLK expression and secretion, as well as activation in various malignancies, has uncovered their potential as mediators of cancer progression, biomarkers of disease and as candidate therapeutic targets. The diversity of signalling pathways and proteolytic cascades involving KLKs and their downstream targets appears to affect cancer biology through multiple mechanisms, including those related to the hallmarks of cancer. The aim of this review is to provide an update on the importance of KLK-driven molecular pathways in relation to cancer cell traits associated with the hallmarks of cancer and to highlight their potential in personalized therapeutics.

A Highly Sensitive Porous Silicon (P-Si)-Based Human Kallikrein 2 (hK2) Immunoassay Platform toward Accurate Diagnosis of Prostate Cancer

Levels of total human kallikrein 2 (hK2), a protein involved the pathology of prostate cancer (PCa), could be used as a biomarker to aid in the diagnosis of this disease. In this study, we report on a porous silicon antibody immunoassay platform for the detection of serum levels of total hK2. The surface of porous silicon has a 3-dimensional macro- and nanoporous structure, which offers a large binding capacity for capturing probe molecules. The tailored pore size of the porous silicon also allows efficient immobilization of antibodies by surface adsorption, and does not require chemical immobilization. Monoclonal hK2 capture antibody (6B7) was dispensed onto P-Si chip using a piezoelectric dispenser. In total 13 × 13 arrays (169 spots) were spotted on the chip with its single spot volume of 300 pL. For an optimization of capture antibody condition, we firstly performed an immunoassay of the P-Si microarray under a titration series of hK2 in pure buffer (PBS) at three different antibody densities (75, 100 and 145 µg/mL). The best performance of the microarray platform was seen at 100 µg/mL of the capture antibody concentration (LOD was 100 fg/mL). The platform then was subsequently evaluated for a titration series of serum-spiked hK2 samples. The developed platform utilizes only 15 µL of serum per test and the total assay time is about 3 h, including immobilization of the capture antibody. The detection limit of the hK2 assay was 100 fg/mL in PBS buffer and 1 pg/mL in serum with a dynamic range of 10⁶ (10⁻⁴ to 10² ng/mL).

Prediction of prostate cancer recurrence using quantitative phase imaging

The risk of biochemical recurrence of prostate cancer among individuals who undergo radical prostatectomy for treatment is around 25%. Current clinical methods often fail at successfully predicting recurrence among patients at intermediate risk for recurrence. We used a label-free method, spatial light interference microscopy, to perform localized measurements of light scattering in prostatectomy tissue microarrays. We show, for the first time to our knowledge, that anisotropy of light scattering in the stroma immediately adjoining cancerous glands can be used to identify patients at higher risk for recurrence. The data show that lower value of anisotropy corresponds to a higher risk for recurrence, meaning that the stroma adjoining the glands of recurrent patients is more fractionated than in non-recurrent patients. Our method outperformed the widely accepted clinical tool CAPRA-S in the cases we interrogated irrespective of Gleason grade, prostate-specific antigen (PSA) levels and pathological tumor-node-metastasis (pTNM) stage. These results suggest that QPI shows promise in assisting pathologists to improve prediction of prostate cancer recurrence.

Effect of chronic Sildenafil treatment on the prostate of C57Bl/6 mice

Sildenafil is a potent and selective inhibitor of phosphodiesterase-5 (PDE5) and is considered first-line therapy for erectile dysfunction. Nowadays, Sildenafil is used extensively throughout the world on patients with pulmonary hypertension. However, few studies have evaluated the possible side effects of chronic Sildenafil treatment on the male reproductive system, specifically in the prostate. In the present study, it was demonstrated via morphological and ultrastructural analysis that chronic treatment with Sildenafil induced an enhancement of the glandular activity of the prostate. In addition, mice treated with Sildenafil showed a significant increase in testosterone serum levels. However, no statistically significant differences were observed in nitric oxide serum levels, or in sGC, eNOS, PSA and TGF-β prostatic expression. In conclusion, the present study suggests that chronic use of Sildenafil does not cause evident prostatic damage, and therefore, can be used pharmacologically to treat a variety of disorders.

Proteomic analysis of patient tissue reveals PSA protein in the stroma of benign prostatic hyperplasia

BACKGROUND

Benign prostatic hyperplasia (BPH) is an age-related disease frequently associated with lower urinary tract symptoms (LUTS) that involves hyperplasia of both epithelial and stromal cells. Stromal fibrosis is a distinctive feature of BPH, but the exact mechanisms underlying this phenomenon are poorly understood.

METHODS

In the current study, proteomics analyses were utilized to identify proteins altered in the BPH stromal compartment from patients with symptomatic BPH. Stromal cells were isolated from histological nodules of BPH by laser capture microdissection (LCM) and subjected to liquid chromatography/mass spectrometry.

RESULTS

Proteins identified included several stromal-specific proteins involved in extracellular matrix (ECM) remodeling, focal adhesion, and cellular junctions. Additionally, the proteomics array identified the presence of luminal epithelial secretory protein PSA. Immunostaining, ELISA, and in situ hybridization analyses of BPH tissues verified the presence of PSA protein but absence of PSA mRNA in the stromal compartment. E-cadherin was down-regulated in BPH epithelial cells compared to normal adjacent tissues, suggesting that alteration of cellular junctions could contribute to the presence of luminal epithelial secreted proteins PSA and KLK2 in the stromal compartment.

CONCLUSIONS

The above findings suggest that the presence of secreted proteins PSA and KLK2 from prostate luminal epithelial cells in BPH stroma is a hallmark of BPH nodules, which could in part be due to alterations in cellular junction proteins and/or increased epithelial barrier permeability. Elucidating the cause and consequence of these secreted proteins in the stromal compartment of BPH may lead to new understanding of BPH pathogenesis as well as approaches to prevent and/or treat this common disease.

Prostate-specific antigen levels are associated with arterial stiffness in essential hypertensive patients

INTRODUCTION

Prostate-specific antigen (PSA) has been recently related to cardiovascular system in a multifactorial way. Arterial stiffness is a independent predictor of cardiovascular events and is involved in the pathogenesis of hypertension. The aim of the present study was to investigate whether PSA values, are associated with arterial stiffness indices in patients with essential arterial hypertension.

METHODS

The study comprised 150 consecutive male patients (mean age 60 years) with uncomplicated never-treated essential hypertension. All patients underwent a complete clinical and laboratory evaluation, including measurement of PSA levels. Aortic stiffness and arterial wave reflection assessment was made by using carotid-femoral (PWVc-f) pulse wave velocity and aortic augmentation index corrected for heart rate (AIx75). Patients with prostate cancer or benign prostate hyperplasia (PSA > 4 ng/mL) were excluded from the study.

RESULTS

PSA was positively associated with waist-to-hip ratio (r = 0.235, P = 0.04), PWVc-f (r = 0.426, P < 0.001), AIx75 (r = 0.264, P = 0.001), and high sensitivity C-reactive protein (hsCRP; r = 0.376, P < 0.001). In categorization to PSA quartiles, patients in the higher quartile presented with higher waist-to hip ratio (P = 0.009), PWVc-f (P < 0.00001), AIx75 (P < 0.001) and hsCRP (P < 0.001) values. In multivariate analysis after adjustment for various confounders PSA remained a significant determinant of PWVc-f values (beta [SE] = 0.477 [0.13], R(2) = 0.405, P < 0.001).

CONCLUSION

The present study points towards an association between PSA levels and aortic stiffness in untreated essential hypertensive males. Potential causal relationships between PSA and arterial stiffness remain to be further explored.

Kallikreins on steroids: structure, function, and hormonal regulation of prostate-specific antigen and the extended kallikrein locus

The 15 members of the kallikrein-related serine peptidase (KLK) family have diverse tissue-specific expression profiles and putative proteolytic functions. The kallikrein family is also emerging as a rich source of disease biomarkers with KLK3, commonly known as prostate-specific antigen, being the current serum biomarker for prostate cancer. The kallikrein locus is also notable because it is extraordinarily responsive to steroids and other hormones. Indeed, at least 14 functional hormone response elements have been identified in the kallikrein locus. A more comprehensive understanding of the transcriptional regulation of kallikreins may help the field make more informed hypotheses about the physiological functions of kallikreins and their effectiveness as biomarkers. In this review, we describe the organization of the kallikrein locus and the structure of kallikrein genes and proteins. We also focus on the transcriptional regulation of kallikreins by androgens, progestins, glucocorticoids, mineralocorticoids, estrogens, and other hormones in animal models and human prostate, breast, and reproductive tract tissues. The interaction of the androgen receptor with androgen response elements in the promoter and enhancer of KLK2 and KLK3 is also summarized in detail. There is evidence that all kallikreins are regulated by multiple nuclear receptors. Yet, apart from KLK2 and KLK3, it is not clear whether all kallikreins are direct transcriptional targets. Therefore, we argue that gaining more detailed information about the mechanisms that regulate kallikrein expression should be a priority of future studies and that the kallikrein locus will continue to be an important model in the era of genome-wide analyses.

"Topological significance" analysis of gene expression and proteomic profiles from prostate cancer cells reveals key mechanisms of androgen response

BACKGROUND

The problem of prostate cancer progression to androgen independence has been extensively studied. Several studies systematically analyzed gene expression profiles in the context of biological networks and pathways, uncovering novel aspects of prostate cancer. Despite significant research efforts, the mechanisms underlying tumor progression are poorly understood. We applied a novel approach to reconstruct system-wide molecular events following stimulation of LNCaP prostate cancer cells with synthetic androgen and to identify potential mechanisms of androgen-independent progression of prostate cancer.

METHODOLOGY/PRINCIPAL FINDINGS

We have performed concurrent measurements of gene expression and protein levels following the treatment using microarrays and iTRAQ proteomics. Sets of up-regulated genes and proteins were analyzed using our novel concept of "topological significance". This method combines high-throughput molecular data with the global network of protein interactions to identify nodes which occupy significant network positions with respect to differentially expressed genes or proteins. Our analysis identified the network of growth factor regulation of cell cycle as the main response module for androgen treatment in LNCap cells. We show that the majority of signaling nodes in this network occupy significant positions with respect to the observed gene expression and proteomic profiles elicited by androgen stimulus. Our results further indicate that growth factor signaling probably represents a "second phase" response, not directly dependent on the initial androgen stimulus.

CONCLUSIONS/SIGNIFICANCE

We conclude that in prostate cancer cells the proliferative signals are likely to be transmitted from multiple growth factor receptors by a multitude of signaling pathways converging on several key regulators of cell proliferation such as c-Myc, Cyclin D and CREB1. Moreover, these pathways are not isolated but constitute an interconnected network module containing many alternative routes from inputs to outputs. If the whole network is involved, a precisely formulated combination therapy may be required to fight the tumor growth effectively.

Selection of RNA aptamers specific to active prostate-specific antigen

A counter-SELEX procedure with recombinant purified active prostate specific antigen (PSA) was used to identify specific RNA aptamers against the active PSA. We developed two different kinds of counter-SELEX methods; one includes pre-clearance step with inactive proPSA protein, and the other with tagged GST protein. After 9 iterative selection cycles, several identical RNA aptamers can be identified from both counter-SELEX methods. Real-time PCR analysis and gel retardation experiment showed that the aptamers have a specific binding activity against the active PSA, but not for GST or proPSA. These aptamers could be of potential use as specific diagnostic, imaging and/or therapeutic agents against prostate cancer.

Antiangiogenic properties of prostate-specific antigen (PSA)

The prostate produces high levels of prostate-specific antigen (PSA, also known as kallikrein-related peptidase 3, KLK3), which is a potential target for tumor imaging and treatment. Although serum PSA levels are elevated in prostate cancer, PSA expression is lower in malignant than in normal prostatic epithelium and it is further reduced in poorly differentiated tumors. PSA has been shown to inhibit angiogenesis both in in vitro and in vivo models. In this review we focus on our recent studies concerning the mechanism of the antiangiogenic function of PSA. We have recently shown that the antiangiogenic activity of PSA is related to its enzymatic activity. Inactive PSA isoforms do not have antiangiogenic activity as studied by a human umbelical vein endothelial cell (HUVEC) tube formation model. Furthermore, inhibition of PSA, either by a monoclonal antibody or small molecule inhibitors abolishes the effect of PSA, while a peptide that stimulates the activity of PSA enhances the antiangiogenic effect. We have analyzed changes in gene expression associated with the PSA induced reduction of tube formation in the HUVEC model. Several small changes were observed and they were found to be opposite to those associated with tube formation. Taken together, these studies suggest that PSA exerts antiantiogenic activity related to its enzymatic activity. Thus it might be associated with the slow growth of prostate cancer.

Prostate-specific antigen kallikrein: from prostate cancer to cardiovascular system

Prostate-specific antigen (PSA), considered only an established marker for the detection of prostate cancer, has been identified as a member (hK3) of the human kallikrein family of serine proteases and now, it is known that PSA is not specific to prostate, semen, and gender. Increased PSA serum levels have been reported also in cardiovascular patients and both elevated as well as diminished PSA have been reported during acute myocardial infarction (AMI). Preliminary observations have concluded that when elevation of prostate-specific antigen occurs during AMI, it seems to relate to a higher occurrence of major adverse cardiac events and that coronary lesions are frequent and often more severe than when a diminution of PSA occurs. Large studies need to be done to confirm these preliminary results but the journey of PSA could be longer than expected.

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.

Development of peptides specifically modulating the activity of KLK2 and KLK3

The prostate produces several proteases, the most abundant ones being kallikrein-related peptidase 3 (KLK3, PSA) and KLK2 (hK2), which are potential targets for tumor imaging and treatment. KLK3 expression is lower in malignant than in normal prostatic epithelium and it is further reduced in poorly differentiated tumors, in which the expression of KLK2 is increased. KLK3 has been shown to inhibit angiogenesis, whereas KLK2 may mediate tumor growth and invasion by participating in proteolytic cascades. Thus, it may be possible to control prostate cancer growth by modulating the proteolytic activity of KLK3 and KLK2. We have developed peptides that very specifically stimulate the activity of KLK3 or inhibit that of KLK2. Using these peptides we have established peptide-based methods for the determination of enzymatically active KLK3. The first-generation peptides are unstable in vivo and are rapidly cleared from the circulation. Currently we are modifying the peptides to make them suitable for in vivo applications. We have been able to considerably improve the stability of KLK2-binding peptides by cyclization. In this review we summarize the possible roles of KLK3 and KLK2 in prostate cancer and then concentrate on the development of peptides that modulate the activity of these proteases.

Tissue prostate-specific antigen facilitates refractory prostate tumor progression via enhancing ARA70-regulated androgen receptor transactivation

Despite being well recognized as the best biomarker for prostate cancer, pathophysiologic roles of prostate-specific antigen (PSA) remain unclear. We report here that tissue PSA may be involved in the hormone-refractory prostate cancer progression. Histologic analyses show that the increased tissue PSA levels are correlated with lower cell apoptosis index and higher cell proliferation rate in hormone-refractory tumor specimens. By stably transfecting PSA cDNA into various prostate cancer cell lines, we found that PSA could promote the growth of androgen receptor (AR)-positive CWR22rv1 and high-passage LNCaP (hormone-refractory prostate cancer cells) but not that of AR-negative PC-3 and DU145 cells. Surprisingly, the protease activity of PSA is not crucial for PSA to stimulate growth and promote AR transactivation. We further showed that increased PSA could enhance ARA70-induced AR transactivation via modulating the p53 pathway that results in the decreased apoptosis and increased cell proliferation in prostate cancer cells. Knockdown of PSA in LNCaP and CWR22rv1 cells causes cell apoptosis and cell growth arrest at the G(1) phase. In vitro colony formation assay and in vivo xenografted tumor results showed the suppression of prostate cancer growth via targeting PSA expression. Collectively, our findings suggest that, in addition to being a biomarker, PSA may also become a new potential therapeutic target for prostate cancer. PSA small interfering RNA or smaller molecules that can degrade PSA protein may be developed as alternative approaches to treat the prostate cancer.

Down regulation of PSA by C/EBPalpha is associated with loss of AR expression and inhibition of PSA promoter activity in the LNCaP cell line

Background

C/EBPα is a transcription factor essential for terminal differentiation of several cell types. It has not known if C/EBPα protein is expressed and functions in the prostate gland.

Methods

The presence of C/EBPα in normal and cancerous prostate epithelium was examined by immunochemistry. Over expression of C/EBPα in LNCaP cells was conducted with retrovirus-mediated transduction. PSA expression was examined by RT-PCR and western blot and PSA promoter activity by luciferase reporter assay.

Results

In normal prostate C/EBPα was expressed in the basal layer of the epithelium. In prostate cancer C/EBPα was detected at low levels throughout the cancers and in advanced prostate cancer C/EBPα expression was associated with decreased expression of AR and PSA. Overexpression of C/EBPα inhibited epigenetically PSA expression and was accompanied by the loss of expression of AR. Transient increase of C/EBPα inhibited the PSA promoter/enhancer activity independently of expression of AR.

Conclusion

In LNCaP cells C/EBPα over expression inhibits expression of PSA by AR -dependent and independent mechanisms and by extinguishing AR expression provides a model for hormonal independent cell growth.

Ovarian cancer, the coagulation pathway, and inflammation

Epithelial ovarian cancer (EOC) represents the most frequent cause of death in the United States from a cancer involving the female genital tract. Contributing to the overall poor outcome in EOC patients, are the metastases to the peritoneum and stroma that are common in this cancer. In one study, cDNA microarray analysis was performed on fresh tissue to profile gene expression in patients with EOC. This study showed a number of genes with significantly altered expression in the pelvic peritoneum and stroma, and in the vicinity of EOC implants. These genes included those encoding coagulation factors and regulatory proteins in the coagulation cascade and genes encoding proteins associated with inflammatory responses. In addition to promoting the formation of blood clots, coagulation factors exhibit many other biologic functions as well as tumorigenic functions, the later including tumor cell proliferation, angiogenesis, invasion, and metastasis. Coagulation pathway proteins involved in tumorigenesis consist of factor II (thrombin), thrombin receptor (protease-activated receptors), factor III (tissue factor), factor VII, factor X and factor I (fibrinogen), and fibrin and factor XIII. In a recent study we conducted, we found that factor XII, factor XI, and several coagulation regulatory proteins, including heparin cofactor-II and epithelial protein C receptor (EPCR), were also upregulated in the peritoneum of EOC. In this review, we summarize evidence in support of a role for these factors in promoting tumor cell progression and the formation of ascites. We also discuss the different roles of coagulation factor pathways in the tumor and peritumoral microenvironments as they relate to angiogenesis, proliferation, invasion, and metastasis. Since inflammatory responses are another characteristic of the peritoneum in EOC, we also discuss the linkage between the coagulation cascade and the cytokines/chemokines involved in inflammation. Interleukin-8, which is considered an important chemokine associated with tumor progression, appears to be a linkage point for coagulation and inflammation in malignancy. Lastly, we review findings regarding the inflammatory process yielded by certain clinical trials of agents that target members of the coagulation cascade in the treatment of cancer. Current data suggest that disrupting certain elements of the coagulation and inflammation processes in the tumor microenvironment could be a new biologic approach to cancer therapeutics.

Effect of the Synthetic Retinoid Fenretinide on Circulating Free Prostate-Specific Antigen, Insulin-Like Growth Factor-I, and Insulin-Like Growth Factor Binding Protein-3 Levels in Men with Superficial Bladder Cancer

PURPOSE

Fenretinide (4-HPR) is a synthetic retinoid that has shown a preventive activity in prostate cancer animal models.

EXPERIMENTAL DESIGN

We measured the changes in total and free prostate-specific antigen (PSA) and its association with insulin-like growth factor I (IGF-I) and IGFBP-3 levels after 1 year of treatment in 24 subjects given 4-HPR and 24 control subjects enrolled in a randomized bladder cancer prevention trial.

RESULTS

No significant effect of 4-HPR was observed on total and free fraction of PSA levels. The median percentage [95 confidence interval (95% CI)] change for % free PSA and total PSA in the 4-HPR and the control group were, respectively, 7.6 (95% CI, -4.0 to 69.3) versus 5.1 (95% CI, -21.4 to 59.8) and -7.8 (95% CI, -18.2 to 52.5) versus -12.3 (95% CI, -44.6 to 9.6). However, in patients ages <60 years, there was a trend to an increase of total free PSA and % free PSA after treatment with 4-HPR that was different from a trend to a decrease in the control group (P = 0.002 and 0.052, respectively). The interaction between age and treatment was statistically significant on free PSA (P = 0.001). A similar pattern was noted with smoking status (P = 0.011 for the interaction on free PSA). No association was observed between PSA levels and IGF-I or IGFBP-3 levels.

CONCLUSIONS

We conclude that 4-HPR has no significant effect on circulating PSA, but it increases significantly free PSA levels in subjects younger than 60 years and in nonsmokers. These effects might support an activity in prostate cancer prevention but further studies are required.

The emerging roles of human tissue kallikreins in cancer

Human tissue kallikreins (hKs), which are encoded by the largest contiguous cluster of protease genes in the human genome, are secreted serine proteases with diverse expression patterns and physiological roles. Although primarily known for their clinical applicability as cancer biomarkers, recent evidence implicates hKs in many cancer-related processes, including cell-growth regulation, angiogenesis, invasion and metastasis. They have been shown to promote or inhibit neoplastic progression, acting individually and/or in cascades with other hKs and proteases, and might represent attractive targets for therapeutic intervention.

Human Tissue Kallikreins: Physiologic Roles and Applications in Cancer

Tissue kallikreins are members of the S1 family (clan SA) of trypsin-like serine proteases and are present in at least six mammalian orders. In humans, tissue kallikreins (hK) are encoded by 15 structurally similar, steroid hormone–regulated genes (KLK) that colocalize to chromosome 19q13.4, representing the largest cluster of contiguous protease genes in the entire genome. hKs are widely expressed in diverse tissues and implicated in a range of normal physiologic functions from the regulation of blood pressure and electrolyte balance to tissue remodeling, prohormone processing, neural plasticity, and skin desquamation. Several lines of evidence suggest that hKs may be involved in cascade reactions and that cross-talk may exist with proteases of other catalytic classes. The proteolytic activity of hKs is regulated in several ways including zymogen activation, endogenous inhibitors, such as serpins, and via internal (auto)cleavage leading to inactivation. Dysregulated hK expression is associated with multiple diseases, primarily cancer. As a consequence, many kallikreins, in addition to hK3/PSA, have been identified as promising diagnostic and/or prognostic biomarkers for several cancer types, including ovarian, breast, and prostate. Recent data also suggest that hKs may be causally involved in carcinogenesis, particularly in tumor metastasis and invasion, and, thus, may represent attractive drug targets to consider for therapeutic intervention.

Recombinant prostate specific antigen inhibits angiogenesis in vitro and in vivo

BACKGROUND

Prostate specific antigen (PSA) is a kallikrein family member with serine protease activity commonly used as a diagnostic marker for prostate cancer. We recently described anti-angiogenic properties of PSA [Fortier et al.: JNCI 91:1635-1640].

METHODS

Two forms of PSA were cloned and expressed in Pichia pastoris: one, an intact PSA with an N-terminus of IVGGVS em leader; the second, an N-1 PSA variant. The recombinant proteins were tested for serine protease activity and for anti-angiogenic activity in vitro and in vivo.

RESULTS

The rate of substrate hydrolysis by the intact recombinant PSA was similar to that of PSA isolated and purified from human seminal plasma. In contrast, the N-1 PSA variant lacked serine protease activity. In an endothelial cell migration assay, the concentration that resulted in 50% inhibition (IC(50)) was: 0.5 microM for native PSA, 0.5 microM for intact recombinant protein, and 0.1 microM for the N-1 variant PSA. Both the intact recombinant and the N-1 recombinant PSA inhibited angiogenesis in vivo.

CONCLUSIONS

Purified recombinant PSA inhibits angiogenesis, proving the concept that PSA is an anti-angiogenic, and serine protease activity, as determined by synthetic substrate hydrolysis, is distinct from the anti-angiogenic properties of PSA.

Prostate-specific antigen (PSA) protein does not affect growth of prostate cancer cells in vitro or prostate cancer xenografts in vivo

BACKGROUND

Prostate-specific antigen (PSA) is produced in high amounts by normal and malignant prostate cancer cells. PSA is a serine protease with substrates that include semenogelin I and II, insulin-like growth factor binding protein 3, fibronectin, and laminin. PSA, via its enzymatic activity, may play a role in growth, invasion, and metastasis of prostate cancer cells. Recent data also suggest that the PSA protein itself, independent of enzymatic activity, may also function as an endothelial cell-specific inhibitor of angiogenesis.

METHODS

Human (PC3, DU145) and rat (AT2, AT6) prostate cancer cell lines were transfected with the full PSA gene encoding preproPSA protein. PSA-producing clones of each cell line were selected and the amount of enzymatically active PSA produced by each cell line determined using a PSA-specific fluorescent peptide substrate. In vitro and in vivo growth characteristics of PSA-producing transfectants were compared to neomycin controls and wild type cells.

RESULTS

All selected clones produced and secreted PSA (5-120 ng/ml/10(5) cells). None of the PSA-transfected cell lines produced detectable amounts of enzymatically active PSA. Production of enzymatically inactive PSA by prostate cancer cell lines did not alter growth kinetics in vitro. PSA-producing xenograft doubling times in vivo were similar to neomycin controls and wild type.

CONCLUSION

Although recent reports suggest the PSA protein itself may be antiangiogenic, our results demonstrate that production of PSA protein by prostate cancer cells does not significantly alter growth in vitro or in vivo.

Bloodborne biomolecular markers in prostate cancer development and progression

Prostate cancer is notoriously difficult to treat, which makes its early detection a priority. Biomarkers have been used to diagnose and monitor prostate cancer for more than 50 years, and the discovery of the serum marker prostate-specific antigen (PSA) significantly altered the detection and management of prostate cancer. But imperfect correlation with cancer hinders the usefulness of PSA. The elucidation and validation of new biological markers of prostate cancer should aid detection, and improve the application of the available therapeutics.

Human tissue kallikreins: a new enzymatic cascade pathway?

Serine proteases are proteolytic enzymes with an active serine residue in their catalytic site. Kallikreins are a subgroup of the serine protease family which is known to have diverse physiological functions. The human kallikrein gene family has now been fully characterized and includes 15 members tandemly located on chromosome 19q13.4. Here we discuss the common structural features of kallikreins at the DNA, mRNA and protein levels and summarize their tissue expression and hormonal regulation patterns. Kallikreins are expressed in many tissues including the salivary gland, endocrine tissues such as testis, prostate, breast and endometrium, and in the central nervous system. Most genes appear to be under steroid hormone regulation. The occurrence of several splice variants is common among kallikreins, and some of the splice variants seem to be tissue-specific and might be related to certain pathological conditions. Kallikreins are secreted in an inactive 'zymogen' form which is activated by cleavage of an N-terminal peptide. Some kalikreins can undergo autoactivation while others may be activated by other kallikreins or other proteases. Most kallikreins are predicted to have trypsin-like enzymatic activity except three which are probably chymotrypsin-like. New, but mainly circumstantial evidence, suggests that at least some kallikreins may be part of a novel enzymatic cascade pathway which is turned-on in aggressive forms of ovarian and probably other cancers.

Inhibition of prostate-specific antigen (PSA) by alpha(1)-antichymotrypsin: salt-dependent activation mediated by a conformational change

Prostate-specific antigen (PSA) and its SDS-stable complex with the serine proteinase inhibitor (serpin) alpha(1)-antichymotrypsin (ACT), which is the dominant form of PSA in serum, are in widespread use as markers for the diagnosis of prostate cancer, and there is increasing evidence for the involvement of PSA proteinase activity itself in the development of prostate and other cancers. However, both the formation and degradation of the PSA-ACT complex, denoted PSA*ACT* to indicate substantial changes in the structure of both proteins on complex formation, have been incompletely studied. Here we determine rate and equilibrium constants for the steps involved in PSA*ACT* formation and demonstrate that (a) the effects of added NaCl, polyamines, and Zn(2+) on this process parallel their effects on PSA catalytic activity [Hsieh, M.-C., and Cooperman, B. S. (2000) Biochim. Biophys. Acta 1481, 75-87], (b) the effect of added NaCl in dramatically increasing the rate of ACT inhibition of PSA correlates with salt-induced changes in PSA conformation, and (c) the PSA*ACT* complex is subject to proteolysis by human neutrophil elastase. Possible clinical implications of these findings are considered.

Prostate-specific antigen and other prostate-derived proteases cleave IGFBP-3, but prostate cancer is not associated with proteolytically cleaved circulating IGFBP-3

BACKGROUND

Proteolysis of insulin-like growth factor-binding proteins (IGFBPs) may increase IGF-mediated growth stimulation and development of cancer in the organs producing large amounts of proteases, such as the prostate.

METHODS

We studied proteolysis of IGFBP-3 by three prostate-derived proteases, namely prostate specific antigen (PSA), human kallikrein 2 (hK2), and trypsin, and also by native seminal plasma. Cleavage of 125I-IGFBP-3 was studied by SDS-PAGE and autoradiography. We also used two different sandwich-type IGFBP-3 immunoassays, called "intact" and "total" IGFBP-3 assays. These assays differ in their capacity to recognize proteolytically degraded IGFBP-3.

RESULTS

HK2, PSA, and trypsin all cleaved IGFBP-3 at the concentrations normally present in seminal plasma. The IGFBP-3 cleavage by seminal plasma was inhibited by ZnCl2, which strongly inhibits hK2 and PSA, but not by a specific trypsin inhibitor. The IGFBP-3 fragments resulting from proteolytic cleavage by PSA, hK2, or trypsin were undetectable in the "intact IGFBP-3 assay," whereas the "total IGFBP-3 assay" also detected the proteolytic fragments. No increased fragmentation of IGFBP-3 was found in serum of 659 men with elevated PSA concentrations, of whom 178 had a proven prostate cancer. Furthermore, the IGFBP-3 levels were not associated with the PSA concentrations.

CONCLUSIONS

These results show that, while seminal plasma and prostate-derived proteases can cleave IGFBP-3, in patients with prostate cancer the circulating IGFBP-3 is not significantly proteolyzed by either PSA, hK2, or trypsin.

Amidolytic activity of prostatic acid phosphatase on human semenogelins and semenogelin-derived synthetic substrates

In addition to kallikrein hK3, a serine protease generally reported as PSA (prostate-specific antigen), at least two other enzymes in human seminal plasma also cleave synthetic peptidyl substrates derived from the sequence of human semenogelins. We have identified one of these as prostatic acid phosphatase (PAP), a major component of prostatic fluid whose physiological function is unclear. The other is a high Mr basic protein present at low concentrations in seminal plasma and that remains to be characterized. PAP was purified to homogeneity from freshly ejaculated seminal plasma. Its N-terminal sequence and its phosphatase properties (hydrolysis of para-nitrophenylphosphate at low pH) were determined, and its inhibition by sodium fluoride measured. Both purified and commercial PAP also had amidolytic activity on peptide substrates derived from the semenogelin sequence at neutral and slightly basic pH. The k(cat)/K(m) values were in the 10(2)-10(3) m(-1) x s(-1) range using fluorogenic semenogelin-derived substrates whose peptidyl moiety included cleavage sites that had been identified ex vivo. PAP cleavage sites differed from those of hK3 and were mainly at P1 = Gln residues or between residues bearing hydroxyl groups. PAP amidolytic activity was poorly inhibited by all currently used wide spectrum proteinase inhibitors. Only 3-4 dichloroisocoumarin and benzamidine inhibited purified PAP. Purified human semenogelin was cleaved by purified and commercial PAP at neutral pH; the two main cleavage sites were at Tyr292 and Ser170 (semenogelin I sequence), only the former has been identified ex vivo by analysis of seminal plasma.

Modulation of recombinant human prostate-specific antigen: activation by Hofmeister salts and inhibition by azapeptides. Appendix: thermodynamic interpretation of the activation by concentrated salts

Prostate specific antigen (PSA, also known as human kallikrein 3) is an important diagnostic indicator of prostatic disease. PSA exhibits low protease activity (>10(4)-fold less than chymotrypsin) under the usual in vitro assay conditions. In addition, PSA does not react readily with prototypical serine protease inactivators. We expressed human PSA (rh-PSA) in Escherichia coli and have demonstrated that rh-PSA has properties similar to those of native PSA isolated from human seminal fluid. Both PSA and rh-PSA are >10(3)-fold more active in the presence of 1.3 M Na(2)SO(4). This activation is anion-dependent, following the Hofmeister series when normality is considered: SO(4)(2)(-) approximately citrate > Ac(-) > Cl(-) > Br(-) > I(-). The nature of the cation has little effect on salt activation. The rate of inactivation of rh-PSA by DFP is 30-fold faster in the presence of 0.9 M Na(2)SO(4), and the rate of inactivation by Suc-Ala-Ala-Pro-Phe-CK is >20-fold faster under these conditions. Azapeptides containing Phe or Tyr at position P(1) also inactivate rh-PSA in the presence of high salt concentrations. These compounds represent the first described inhibitors designed to utilize the substrate binding subsites of PSA. CD spectroscopy demonstrates that the conformation of rh-PSA changes in the presence of high salt concentrations. Analytical ultracentifugation and dynamic light scattering indicate that PSA remains monomeric under high-salt conditions. Interestingly, human prostatic fluid contains as much as 150 micro mol citrate/g wet weight, which suggests that salt concentrations may regulate PSA activity in vivo.

Characterization of PSA-RP2, a protein related to prostate-specific antigen and encoded by alternative hKLK3 transcripts

Despite the wide use of prostate-specific antigen (PSA) as a marker of prostate cancer, analysis of its gene products has not yet been completed. The structure of two alternative mRNAs (0.9 and 1.65 kb) of the hKLK3 gene that retain the third intron is reported here. These partially spliced transcripts were detected by hybridization or RT-PCR in normal prostate tissue, benign prostate hyperplasia (BPH) and cancerous prostate tissues, and also in the prostate LNCaP cell line. Insertion of the unspliced intron creates an in-frame stop codon and results in a truncated prepro PSA variant of 180 amino-acid residues. This novel variant, designated PSA-RP2, has an alternate C-terminal tail and lacks the serine residue essential for the catalytic activity of PSA. Prepro PSA-RP2 was transiently produced in COS-7 cells and detected in the spent medium using an anti-PSA serum. Secreted PSA-RP2 was glycosylated with an apparent molecular mass of 25 kDa. Our findings suggest that PSA-RP2 contributes to the molecular heterogeneity of free-PSA in the serum of patients with benign or malignant prostate tumors.

The role of transforming growth factor-beta and its receptors in human prostate smooth muscle cell fibronectin production

In the present study, the role of transforming growth factor-beta (TGFbeta) on the production of the extracellular matrix component, fibronectin, in the prostate has been studied. The mRNA levels of fibronectin, TGFbeta and the two TGFbeta receptors, ALK5 (activin like kinase) and type II, were measured using reverse-transcription polymerase chain reaction (RT-PCR). TGFbeta increased fibronectin mRNA and protein (7-fold) in a concentration-dependent fashion. An interesting relationship between the two TGFbeta receptors was found in that TGFbeta caused an upregulation of its type I receptor mRNA (5-6-fold) and a downregulation of the type II receptor mRNA (5-fold). Time-course experiments revealed that the change in expression of the TGFbeta receptors reached maximum at 24 h with an early increase at 4-5 h, whereas the fibronectin gene expression was not significantly stimulated until about 24 h. These data provide evidence that TGFbeta stimulates extracellular matrix production in prostate cells.

The new human tissue kallikrein gene family: structure, function, and association to disease

The human tissue kallikrein gene family was, until recently, thought to consist of only three genes. Two of these human kallikreins, prostate-specific antigen and human glandular kallikrein 2, are currently used as valuable biomarkers of prostatic carcinoma. More recently, new kallikrein-like genes have been discovered. It is now clear that the human tissue kallikrein gene family contains at least 15 genes. All genes share important similarities, including mapping at the same chromosomal locus (19q13.4), significant homology at both the nucleotide and protein level, and similar genomic organization. All genes encode for putative serine proteases and most of them are regulated by steroid hormones. Recent data suggest that at least a few of these kallikrein genes are connected to malignancy. In this review, we summarize the recently accumulated knowledge on the human tissue kallikrein gene family, including gene and protein structure, predicted enzymatic activities, tissue expression, hormonal regulation, and alternative splicing. We further describe the reported associations of the human kallikreins with various human diseases and identify future avenues for research.

Equivalent racial outcome after conformal radiotherapy for prostate cancer: a single departmental experience

PURPOSE

African-American (AA) men with prostate cancer present with advanced disease, relative to white (W) men. This report summarizes our clinical and biochemical control (bNED) rates after conformal radiotherapy (RT). In particular, we aim to characterize any race-based outcome differences seen after comparable treatment.

PATIENTS AND METHODS

We reviewed 893 patients (418 AA and 475 W) with clinically localized prostate cancer treated between 1988 and 1997. Neoadjuvant hormonal blockade was used in 22.5% of cases, and all patients received conformal RT to a median dose of 68 Gy (range, 60 to 74.8 Gy). Biochemical failure was defined according to the American Society of Therapeutic Radiology and Oncology consensus definition. Median follow-up was 24 months (range, 1 to 114 months).

RESULTS

The 5-year actuarial survival, disease-free survival, and bNED rates for the entire population were 80.5%, 70.0%, and 57.6%, respectively. When classified by prognostic risk category, the 5-year actuarial bNED rates were 78.7% for favorable, 57.7% for intermediate, and 39.8% for unfavorable category patients. AA men presented at younger ages and with more advanced disease. Controlled for prognostic risk category, AA and W men had similar 5-year actuarial bNED rates in favorable (78% v 79%, P: = .91), intermediate (52% v 62%, P: =.44), and unfavorable categories (36% v 45%, P: = .09). Race was not an independent prognostic factor (P: = .36).

CONCLUSION

Conformal RT is equally effective for AA and W patients. More research is needed in order to understand and correct the advanced presentations in AA men. These data suggest a need for early screening in AA populations.

High levels of zinc ions induce loss of mitochondrial potential and degradation of antiapoptotic Bcl-2 protein in in vitro cultivated human prostate epithelial cells

Prostate epithelial cells contain the highest levels of zinc among all organs and tissues in the human body. Zinc is accumulated primarily in the mitochondria, where it is responsible for inhibition of mitochondrial aconitase activity, thereby increasing citrate production. The present study was designed to clarify the role of zinc for human prostate epithelial cell growth and apoptosis. Apoptosis of in vitro cultivated human prostate epithelial cells exposed to ZnCl(2) was analyzed by determination of phospholipid membrane asymmetry, nuclear fragmentation, DNA strand breaks, changes of mitochondrial potential and cellular pro/antiapoptotic proteins. Zinc induced apoptosis without involvement of p53 by decreasing mitochondrial transmembrane potential (DeltaPsi(m)) and Bcl-2 protein levels in proliferating epithelial cells. Thus, the high local concentrations of zinc ions in the prostatic lumen seem to be necessary to regulate proliferative activities and to enforce epithelial differentiation processes.

Aging of the male reproductive system

Reproductive and sexual physiology, changes in body composition and mental performance in the aging male cannot simply be reduced to presumptive hypogonadism defined by low androgen serum levels or by decreasing levels of growth hormone (GH) and melatonin. Morphological changes in organs at different regulatory levels of hormonal networks governing, for example reproduction, such as diminished hypothalamic pulse generator mass, focal degeneration and loss of Leydig cells in testicular tissue, lead to diminished reserve capacities in production and to loss of coordinated pulsatile release of hypothalamic neuropeptides (e.g. gonadotropin releasing hormone, GnRH) and consequently diminished release of pituitary protein and glycoprotein hormones and testicular steroid hormones. Owing to presumptive alterations in feedback sensitivity, decreased testosterone levels do not necessarily upregulate pituitary LH secretion. Alternatively, increased serum levels of LH and FSH can be observed in old men either because of primary hypogonadism or to decreased hypothalamic opioid tone. In general, endocrine functions are sufficient to maintain fertility in elderly men because, except for sperm motility, quantitative and qualitative functional semen parameters are apparently not affected by age. Nevertheless, reduced endocrine and organic functions might become critical at different levels, with high inter-individual variability, of the hypothalamo/pituitary/gonadal-axis. One of the most intriguing organic manifestations of male aging is benign prostatic hyperplasia (BPH), the pathologic prevalence of which closely matches age. Age-associated changes in the endocrine system and in local networks of epithelial, stromal and luminal factors may play important roles in BPH development.

Cultured stromal cells: an in vitro model of prostatic mesenchymal biology

BACKGROUND

Initial efforts to develop in vitro models to study prostatic biology focused on the culture and characterization of epithelial cells. Recently, attention has turned towards inclusion of stromal cells in experimental systems.

METHODS

Improved methods to isolate and culture stromal cells have been developed. An array of markers are employed to characterize subtypes of stromal cells, with particular interest in smooth muscle differentiation.

RESULTS

Defined, serum-free media are available for certain experimental applications. Conditions that promote smooth muscle differentiation have been identified. Investigators have characterized hormonal and peptide factors that regulate the growth of prostatic stromal cells, and have also described paracrine factors produced by stromal cells that influence epithelial biology.

CONCLUSIONS

Prostatic stromal-cell cultures are now widely employed by a large number of investigators for a diverse array of experimental purposes. While further refinement is required to obtain model systems that fully mimic in vivo processes, the availability of stromal- and epithelial-cell cultures provides a valuable resource for studying normal prostatic biology as well as benign prostatic hyperplasia (BPH) and cancer.

Insulin-like growth factor I is not a useful marker of prostate cancer in men with elevated levels of prostate-specific antigen

High serum levels of insulin-like growth factor I (IGF-I) and low levels of IGF-binding protein-3 (IGFBP-3) have been shown to correlate with increased prostate cancer risk. To evaluate this, IGF-I, IGFBP-3, and prostate-specific antigen (PSA) were measured in serum from 665 consecutive men (179 with prostate cancer), aged 55-67 yr, with elevated serum prostate-specific antigen (PSA; > or = 4 microg/L) in a screening trial. Men in the highest quartile of IGF-I levels had an odds ratio (OR) for prostate cancer of 0.50 [95% confidence interval (CI) 0.26-0.97] when adjusting for serum IGFBP-3. IGFBP-3 itself was not significantly associated with prostate cancer risk (OR, 1.24; 95% CI, 0.68-2.24). Prostate volume was larger in men without than in those with prostate cancer (P < 0.001), and after adjustment for prostate volume, the negative association between serum IGF-I and prostate cancer risk was no longer significant (OR, 0.57; 95% CI, 0.28-1.16). In screen-positive men with elevated serum PSA, serum IGF-I is not a useful diagnostic test for prostate cancer, but it may be associated with benign prostatic hyperplasia and enlargement.