Bloodborne biomolecular markers in prostate cancer development and progression

Evaluation of Plasma Circulating Cell Free DNA Concentration and Integrity in Patients with Prostate Cancer in Jamaica: A Preliminary Study

Background: Cell free circulating DNA (cfcDNA) is a promising diagnostic tool for prostate cancer (PCa). This study aimed to measure the cfcDNA concentration and integrity in PCa patients using quantitative polymerase chain reaction (qPCR) analysis. This study also assessed the correlation between these molecular biomarkers with total prostate-specific antigen (PSA), Gleason score, prostate volume, and age. Methods: Eleven PCa patients and 9 persons with benign prostatic hyperplasia (BPH) were recruited. Blood samples were collected before prostate biopsy and plasma quantified by qPCR amplification of the ALU 115 DNA sequence, with the ratio of ALU 247 to ALU 115 reflecting cfcDNA integrity. Results: There were no significant differences in median, interquartile range (IQR) cfcDNA concentration or cfcDNA integrity between the patients with PCa (47.9 (214.93) ng/mL; 0.61 (0.49)) and persons with BPH (41.5 (55.13) ng/mL, p = 0.382; 0.67 (0.45), p = 0.342). A weakly positive correlation exists between cfcDNA concentration and total PSA (r = 0.200, p = 0.555) but not with age or Gleason score in PCa patients. Conclusion: cfcDNA concentration was relatively nonsignificantly higher in PCa patients in comparison to persons with BPH, whereas cfcDNA integrity was similar in both groups. Though limited in sample size, this study shows that cfcDNA concentration may be a potentially valuable noninvasive biomarker for the diagnosis of PCa.

Colorimetric switchable linker-based bioassay for ultrasensitive detection of prostate-specific antigen as a cancer biomarker

The use of colorimetric bioassays for protein detection is one of the most interesting diagnostic approaches, but their relatively poor detection limits have been a critical issue. In this study, we developed an efficient colorimetric bioassay based on switchable linkers (SLs) for the detection of prostate-specific antigen (PSA), which is one of the most widely used protein biomarkers for the diagnosis of prostate and breast cancers. SLs can cross-link gold nanoparticles (AuNPs) to generate large-scale aggregates and thereby induce precipitation to achieve visual signal amplification. In addition, when SLs are occupied by target proteins (referred to as 'switch-off'), highly sensitive detection is enabled. To maximize sensitivity, we adjusted the total surface area of AuNPs by controlling their concentration. As a result, PSA was detected at an ultralow concentration of 100 fg mL-1. This SL-based assay is shown to be simple, easy to handle and visualize, and highly sensitive. Therefore, in addition to PSA, the proposed SL-based assay could be used to detect other protein biomarkers.

Graphene-based biosensors for the detection of prostate cancer protein biomarkers: a review

Prostate cancer (PC) is the sixth most common cancer type in the world, which causes approximately 10% of total cancer fatalities. The detection of protein biomarkers in body fluids is the key topic for the diagnosis and prognosis of PC. Highly sensitive screening of PC is the most effective approach for reducing mortality. Thus, there are a growing number of literature that recognizes the importance of new technologies for early diagnosis of PC. Graphene is playing an important role in the biosensor field with remarkable physical, optical, electrochemical and magnetic properties. Many recent studies demonstrated the potential of graphene materials for sensitive detection of protein biomarkers. In this review, the graphene-based biosensors toward PC analysis are mainly discussed in two groups: Firstly, novel biosensor interfaces were constructed through the modification of graphene materials onto sensor surfaces. Secondly, ingenious signal amplification strategies were developed using graphene materials as catalysts or carriers. Graphene-based biosensors have exhibited remarkable performance with high sensitivities, wide detection ranges, and long-term stabilities.

An electrochemical immunosensor for the prostate specific antigen based on the use of reduced graphene oxide decorated with gold nanoparticles

The authors describe an immunosensor for the prostate specific antigen (PSA). It was obtained by modifying a glassy carbon electrode (GCE) first modified with gold nanoparticles and then with reduced graphene oxide that was decorated with gold nanoparticles. The AuNPs on reduced graphene oxide provide a suitable surface for attachment of antibodies. On binding of the antigen, the square wave voltammetric signal (measured by using hexacyanoferrate as a probe) reduced. This method has two logarithmically linear analytical ranges that extend from 25 to 55 fg.mL^-1 and from 1 to 36 ng.mL^-1, respectively. The lowest detection limit is 2 pg.mL^-1. Electrochemical impedance spectroscopy was also carried out for PSA determination. EIS works in the 0.0018 to 41 ng.mL^-1 concentration range and has an LOD of 60 pg.mL^-1. This method was applied to the determination of PSA in (spiked) human serum samples. In order to survey the selectivity of immunosensor, determination of PSA was performed in human serum samples, and finally sensitivity and reproducibility were examined. Graphical abstract Facile label free immunosensor based on reduced graphene oxide decorated with gold nanoparticles for early diagnosis prostate cancer via ultrasensitive detection of PSA biomarker: application in human serum.

Cancer Targeting Potential of 99mTc-Finasteride in Experimental Model of Prostate Carcinogenesis

This study aimed to radiolabel finasteride, a novel 5α-reductase inhibitor, to evaluate its cancer targeting potential in experimental model of prostate carcinogenesis. Finasteride was effectively radiolabeled with ^99mTc and showed >90% labeling efficiency. The radiopharmaceutical was found to be stable up to 6 hours in rat serum at 37°C. The blood kinetics of the ^99mTc-finasteride followed a biphasic release pattern, whereby fast-release phase was observed at 15 seconds and a slow-release phase was observed after 30 minutes of administration. The plasma protein binding of the radio complex observed was 83.89%. For biodistribution studies, the rats were divided into two groups. Group I served as normal controls, while group II was subjected to carcinogen N-methyl-N-nitrosourea (MNU) and hormone testosterone propionate (T) for induction of prostate carcinogenesis, which was confirmed histopathologically. The biodistribution studies on control and carcinogen-treated rats revealed a significant percent-specific uptake in prostate, which was found to be increased significantly as a function of time. The most significant finding of the study was an increase in the percent-specific uptake in prostate of carcinogen-treated animals when compared to the percent-specific uptake in prostate of normal rats after 2 and 4 hours postinjection. The study concludes that ^99mTc-finasteride possesses selectively toward prostate cancer tissue and can be explored further for its role in detection of prostate cancer.

REST is a crucial regulator for acquiring EMT-like and stemness phenotypes in hormone-refractory prostate cancer

Castration-resistance prostate cancer (CRPC), also known as hormone-refractory prostate cancer (HRPC), requires immediate attention since it is not only resistant to androgen ablation, chemo- and radiotherapy, but also highly metastatic. Increasing evidence suggests that enrichment of neuroendocrine (NE) cells is associated with CRPC. Here, combined RNA-seq and ChIP-seq analysis reveals that REST is involved in epithelial-mesenchymal transition (EMT) and stemness acquisition in NE differentiated prostate cancer (PCa) cells via direct transcriptional repression of Twist1 and CD44. Specifically we show that short-term knockdown of REST induces NE differentiation of LNCaP cells. Long-term REST knockdown enhanced the expression of Twist1 and CD44, cell migration and sphere formation. Overexpression of REST in hormone-refractory CWR22Rv1 PCa cells significantly reduces Twist1 and CD44 expression, cell migration and sphere formation. Collectively, our study uncovers REST in regulating EMT and stemness properties of NE PCa cells and suggests that REST is a potential therapeutic target for CRPC.

Locus-specific gene repositioning in prostate cancer

The spatial organization of the genome is altered in prostate cancer compared to normal tissue in a gene-specific manner. The repositioning of two genes, FLI1 and MMP9, is specific to cancer, and the positioning patterns of these genes may serve as diagnostic biomarkers.

Genes occupy preferred spatial positions within interphase cell nuclei. However, positioning patterns are not an innate feature of a locus, and genes can alter their localization in response to physiological and pathological changes. Here we screen the radial positioning patterns of 40 genes in normal, hyperplasic, and malignant human prostate tissues. We find that the overall spatial organization of the genome in prostate tissue is largely conserved among individuals. We identify three genes whose nuclear positions are robustly altered in neoplastic prostate tissues. FLI1 and MMP9 position differently in prostate cancer than in normal tissue and prostate hyperplasia, whereas MMP2 is repositioned in both prostate cancer and hyperplasia. Our data point to locus-specific reorganization of the genome during prostate disease.

The combined serum levels of miR-375 and urokinase plasminogen activator receptor are suggested as diagnostic and prognostic biomarkers in prostate cancer

This study aimed to assess the applicability of miR-375 in combination with the soluble urokinase plasminogen activator receptor (suPAR) protein as a diagnostic and/or prognostic biomarker for prostate cancer (PCa) patients. miR-375 levels by qRT-PCR and suPAR levels by ELISA were evaluated in serum samples from 146 PCa patients, 35 benign prostate hyperplasia (BPH) patients and 18 healthy controls. Antigen levels of suPAR differed between healthy controls and PCa or BPH patients, whereas miR-375 levels differed between PCa and BPH patients or healthy controls (p < 0.001). Additionally, suPAR levels differed between the Gleason sum groups GS = 7 versus GS > 7, with higher levels in the latter group (p = 0.011), and miR-375 levels were higher in the tumor stage group T3-T4 compared with the T1-T2 group (p = 0.039). A high concentration of suPAR was associated with a poor disease-specific survival (DSS; p = 0.039). The combination of suPAR and miR-375 levels identified a patient group possessing high levels for both parameters. This was associated with a poorer 10-year overall survival (OS) and DSS, with a 6.38-fold increased risk of death and a 7.68-fold increased risk of tumor-related death (p = 0.00026 and p = 0.014; univariate Cox's regression analysis). In a multivariate Cox's regression analysis PCa patients with high levels of suPAR and miR-375 showed a 5.72-fold increased risk of death in OS (p = 0.006). In summary, the differences between the PCa/BPH/healthy control cohorts for either suPAR and miR-375 levels in conjunction with the association of combined high suPAR/miR-375 levels with a poor prognosis suggest a diagnostic and prognostic impact for PCa patients.

The potential of neurotensin secreted from neuroendocrine tumor cells to promote gelsolin-mediated invasiveness of prostate adenocarcinoma cells

Neuroendocrine (NE) cells in prostate cancer have been shown to be associated with the progression of prostate cancer. However, little is known about the molecular basis of this association. We have previously demonstrated that NE cells promote metastasis of a human prostate cancer cell line (LNCaP) with overexpression of the gelsolin gene. The purpose of this study was to investigate the interactions between NE cells and LNCaP cells and the involvement of gelsolin in contributing to the invasive potential of LNCaP cells. In addition, we examined whether neurotensin induced gelsolin-mediated invasion. We used the NE cell line NE-CS that was established from the prostate of the LPB-Tag 12T-10 transgenic mouse. Small interfering RNA (siRNA) targeting gelsolin or not targeting it was transfected into LNCaP cells. Cell invasion was assessed by Matrigel invasion assay. The supernatant of NE-CS cells and neurotensin induced the transformation of LNCaP cells. Neurotensin was observed in the supernatant of NE-CS cells but not in LNCaP cells. The siRNA targeting of gelsolin resulted in inhibition of invasion of LNCaP cells in the culture medium with neurotensin added, and in the supernatant of NE-CS cells with epidermal growth factor. The invasive potential of LNCaP cells enhanced by neurotensin or the supernatant of NE-CS cells through neurotensin receptor 1 (NTSR1) was blocked by a phospholipase Cγ inhibitor and an intracellular calcium chelator, with concomitant gelsolin suppression. This study indicates that NE cells and neurotensin induce gelsolin-mediated invasion of LNCaP cells through NTSR1 activation.

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.

Fusion of an Fc chain to a VHH boosts the accumulation levels in Arabidopsis seeds

Nanobodies® (VHHs) provide powerful tools in therapeutic and biotechnological applications. Nevertheless, for some applications, bivalent antibodies perform much better, and for this, an Fc chain can be fused to the VHH domain, resulting in a bivalent homodimeric VHH-Fc complex. However, the production of bivalent antibodies in Escherichia coli is rather inefficient. Therefore, we compared the production of VHH7 and VHH7-Fc as antibodies of interest in Arabidopsis seeds for detecting prostate-specific antigen (PSA), a well-known biomarker for prostate cancer in the early stages of tumour development. The influence of the signal sequence (camel versus plant) and that of the Fc chain origin (human, mouse or pig) were evaluated. The accumulation levels of VHHs were very low, with a maximum of 0.13% VHH of total soluble protein (TSP) in homozygous T3 seeds, while VHH-Fc accumulation levels were at least 10- to 100-fold higher, with a maximum of 16.25% VHH-Fc of TSP. Both the camel and plant signal peptides were efficiently cleaved off and did not affect the accumulation levels. However, the Fc chain origin strongly affected the degree of proteolysis, but only had a slight influence on the accumulation level. Analysis of the mRNA levels suggested that the low amount of VHHs produced in Arabidopsis seeds was not due to a failure in transcription, but rather to translation inefficiency, protein instability and/or degradation. Most importantly, the plant-produced VHH7 and VHH7-Fc antibodies were functional in detecting PSA and could thus be used for diagnostic applications.

Challenges and opportunities for cancer vaccines in the current NSCLC clinical scenario

This review is aimed to focus on NSCLC as an emerging and promising model for active immunotherapy and the challenges for its inclusion in the current clinical scenario. Cancer vaccines for NSCLC have been focused as a therapeutic option based on the identification of a tumor hallmark and the active immunization with the related molecules that triggers cellular and/or humoral responses that consequently destroy or delay the rate of malignant progression. This therapeutic intervention in an established disease state has been aimed to impact into prolonging patient´s survival with ethically accepted quality of life. Understanding of relationship between structure and function in cancer vaccines is essential to interpret their opportunities to impact into prolonging survival and increasing quality of life in cancer patients. It is widely accepted that the failure of the cancer vaccines in the NSCLC scenario is related with its introduction in the advanced disease stages and poor performance status of the patients due to the combination of the tumor induced immunosuppression with the immune senescence. Despite first, second and emerging third line of onco-specific treatments the life expectancy for NSCLC patients diagnosed at advanced stages is surrounding the 12 months of median survival and in facts the today real circumstances are extremely demanding for the success inclusion of cancer vaccines as therapeutic choice in the clinical scenario. The kinetics of the active immunizations encompasses a sequential cascade of clinical endpoints: starting by the activation of the immune system, followed by the antitumor response and finalizing with the consequential impact on patients’ overall survival. Today this cascade of clinical endpoints is the backbone for active immunization assessment and moreover the concept of cancer vaccines, applied in the NSCLC setting, is just evolving as a complex therapeutic strategy, in which the opportunities for cancer vaccines start from the selection of the target cancer hallmark, followed by the vaccine formulation and its platforms for immune potentiating, also cover the successful insertion in the standard of care, the chronic administration beyond progression disease, the personalization based on predictors of response and the potential combination with other targeted therapies.

Hypoxia enhances the expression of prostate-specific antigen by modifying the quantity and catalytic activity of Jumonji C domain-containing histone demethylases

Oxygen concentration in prostate cancer tissue is significantly low, i.e. ~0.3% O2. This study showed that pathological hypoxia (<0.5% O2) increased the expression of androgen receptor (AR) target genes such as prostate-specific antigen (PSA) and kallikrein-related peptidase 2 in LNCaP human prostate cancer cells by modifying the quantity and activity of related Jumonji C domain-containing histone demethylases (JMJDs). Under pathological hypoxia, the catalytic activities of JMJD2A, JMJD2C and Jumonji/ARID domain-containing protein 1B (JARID1B) were blocked due to the lack of their substrate, i.e. oxygen. Chromatin immunoprecipitation analyses showed that hypoxia increased the appearance of H3K9me3 and H3K4me3, substrates of JMJD2s and JARID1B, respectively, in the PSA enhancer. In contrast, JMJD1A, which demethylates both H3K9me2 and H3K9me1, maintained its catalytic activity even under severe hypoxia. Furthermore, hypoxia increased the expression of JMJD1A. Hypoxia and androgen additively increased the recruitment of JMJD1A and p300 on the enhancer region of PSA through interaction with the hypoxia-inducible factor-1α and AR, both of which bind the PSA enhancer. Thus, hypoxia enhanced the demethylation of H3K9me2 and H3K9me1, leading to provide unmethylated H3K9 residues that are substrates for histone acetyltransferase, p300. Consequently, hypoxia increased the acetylation of histones of the PSA enhancer, which facilitates its transcription.

Zoledronic acid but not somatostatin analogs exerts anti-tumor effects in a model of murine prostatic neuroendocrine carcinoma of the development of castration-resistant prostate cancer

BACKGROUND

Since neuroendocrine (NE) cells play an important role in the development of castration-resistant prostate cancer (CRPC), target therapy to NE cells should be considered for treating CRPC. We investigated the effects zoledronic acid (ZOL) and two somatostatin analogs (octreotide: SMS, and pasireotide: SOM) on an NE allograft (NE-10) and its cell line (NE-CS), which were established from the prostate of the LPB-Tag 12T-10 transgenic mouse.

METHODS

We examined the in vivo effects of ZOL, SMS and SOM as single agents and their combinations on subcutaneously inoculated NE-10 allografts and the in vitro effects on NE-CS cells. Apoptosis and cell cycle activity were assessed by immunohistochemistry using TdT-mediated dUTP-biotin nick-end labeling (TUNEL) and a Ki-67 antibody, respectively.

RESULTS

In vivo growth of NE-10 tumors treated with ZOL, ZOL plus SMS, or ZOL plus SOM was significantly inhibited compared to the control as a consequence of induction of apoptosis and cell cycle arrest. ZOL induced time- and dose-dependent inhibition of in vitro proliferation of NE-CS cells, but the somatostatin analogs (SMS and SOM) did not. ZOL also inhibited migration of NE-CS cells. These effects were caused by inhibition of Erk1/2 phosphorylation via impairment of prenylation of Ras.

CONCLUSIONS

ZOL, but not SMS or SOM, induced apoptosis and inhibition of proliferation and migration through impaired prenylation of Ras in NE carcinoma models. Our findings support the possibility that ZOL could be used in the early phase for controlling NE cells, which may trigger progression to CRPC.

Hybridoma technology for the generation of monoclonal antibodies

Hybridoma technology has long been a remarkable and indispensable platform for generating high-quality monoclonal antibodies (mAbs). Hybridoma-derived mAbs have not only served as powerful tool reagents but also have emerged as the most rapidly expanding class of therapeutic biologics. With the establishment of mAb humanization and with the development of transgenic-humanized mice, hybridoma technology has opened new avenues for effectively generating humanized or fully human mAbs as therapeutics. In this chapter, an overview of hybridoma technology and the laboratory procedures used routinely for hybridoma generation are discussed and detailed in the following sections: cell fusion for hybridoma generation, antibody screening and characterization, hybridoma subcloning and mAb isotyping, as well as production of mAbs from hybridoma cells.

Cyr61 is up-regulated in prostate cancer and associated with the p53 gene status

Cysteine-rich 61 (Cyr61) is a member of the CCN protein family that has been implicated in diverse biological processes such as cell adhesion, proliferation, angiogenesis, and tumorigenesis. Altered expression of Cyr61 is found to be associated with human cancers. Here we show that Cyr61 was up-regulated in prostate cancer cell lines and tumor tissues. A significant correlation of Cyr61 expression was found between benign prostatic hyperplasia and prostate cancer (P = 0.002). However, there was no significant correlation between levels of PSA and Cyr61 expression (P = 0.2). Cyr61 may represent an independent prostate cancer biomarker and potentially a useful therapeutic target for prostate cancer treatment. In addition, our analysis based on published data and data present in this report indicted that levels of Cyr61 expression associated with the status of the tumor suppressor gene p53 in 32 cancer cell lines analyzed, high levels of Cyr61 expression were found in cell lines with mutant or null p53 gene, whereas lower expression levels of Cyr61 in the cell lines with wild-type p53. We further show that over-expression of dominant negative p53 or down-expression of endogenous wild-type p53 resulted in up-regulation of Cyr61 expression, suggesting a functional link between Cyr61 and p53 in cancers.

Endo180 expression with cofunctional partners MT1-MMP and uPAR-uPA is correlated with prostate cancer progression

Endo180 (CD280; MRC2; uPARAP) regulates collagen remodelling and chemotactic cell migration through cooperation with membrane type-1 matrix metalloproteinase (MT1-MMP), urokinase-type plasminogen activator receptor (uPAR) and urokinase-type plasminogen activator (uPA). One hundred and sixty nine prostate tissue sections clinically graded as benign prostatic hyperplasia (BPH) (n=29) or prostate cancer (PCA) with Gleason scores indicating low (< or =7(3+4); n=26), intermediate (7(4+3)-8; n=96) or high (9-10; n=19) clinical risk were immunofluorescently stained for Endo180, pan-cytokeratin (pCk), vimentin, MT1-MMP and uPAR-uPA. Quantification of % Endo180(+)/pCk(-) and Endo180(+)/pCk(+) cells in entire tissue cores revealed stromal (p=0.0001) and epithelial (p=0.0001) upregulation of Endo180 in PCA compared to BPH. Epithelial Endo180 expression was significantly different between the three clinical risk groups of PCA (p<0.05). Correlations with MT1-MMP and uPAR-uPA confirmed the functionality of Endo180 during PCA progression. This molecular evaluation is the first step in the exploration of Endo180 in PCA diagnosis and therapy.

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.

Auto-antibodies in prostate cancer: humoral immune response to antigenic determinants coded by the differentially expressed transcripts FLJ23438 and VAMP3

BACKGROUND

Here we evaluate auto-antibody response against two potential antigenic determinants of genes highly expressed in low Gleason Score prostate cancer (PC) tumor samples, namely FLJ23438 and VAMP3.

METHODS

RT-PCR assays were used to analyze mRNA expression profiles of FLJ23438 and VAMP3 transcripts. The auto-antibody response against FLJ23438 and VAMP3 recombinant proteins was tested by immunoblot assays using PC, benign prostate hyperplasia (BPH), healthy donors (HD), and other human cancers plasma samples.

RESULTS

Our data showed that 37% (10/27) and 7.4% (2/27) of PC plasma samples presented auto-antibodies against FLJ23438 and VAMP3, respectively. Only 8.3% (1/12) of BPH plasma samples were reactive for both auto-antibodies, while none (0/12) of HD plasma samples tested were reactive.

CONCLUSIONS

The prevalence of 37% of positive PC plasma samples for anti-FLJ23438 antibodies suggests that humoral immune response against this antigenic determinant could be a potential serum marker for this cancer.

Prognostic value of serum markers for prostate cancer

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

Prostate-specific antigen immunosensing based on mixed self-assembled monolayers, camel antibodies and colloidal gold enhanced sandwich assays

Prostate-specific antigen (PSA) is a valuable biomarker for prostate cancer screening. We developed a PSA immunoassay on a commercially available surface plasmon resonance biosensor. Our PSA receptor molecule consists of a single domain antigen-binding fragment, cAbPSA-N7, derived from dromedary heavy-chain antibodies and identified after phage display. It binds PSA with a high k(on) value of 1.9x10(6) M-1 s-1, and was covalently immobilised on a gold substrate via a mixed self-assembled monolayer (SAM) of alkanethiols by using carbodiimide-coupling chemistry in 10mM acetate buffer pH 5.5 to obtain an optimal pre-concentration. The best performing and optimised mixed SAM consisted of (10%) 16-mercapto-1-hexadecanoic acid (16-MHA) for covalent cAbPSA-N7 immobilisation and (90%) 11-mercapto-1-undecanol (11-MUOH) to minimise non-specific adsorption of the analyte. In this way, two advantages are incorporated in a single coupling layer. Up to 28 fmol/mm2 of cAbPSA-N7 could be immobilised and 30% of its binding sites participate actively in PSA interaction. In addition, the optimised layer showed also optimal performance to assess physiological samples. Although PSA concentrations as low as 10 ng/ml could be detected directly, this detection limit could be enhanced to PSA levels in the sub ng/ml range by introducing a sandwich assay involving a biotinylated secondary antibody and streptavidin modified gold nanoparticles. This approach realizes the PSA detection at clinical relevant concentrations.

Functionality of androgen receptor-based gene expression imaging in hormone refractory prostate cancer

PURPOSE

A highly augmented, prostate-specific two-step transcriptional amplification (TSTA) method was developed with the ultimate goal of delivering an effective and safe gene-based treatment to prostate cancer patients. Because very limited treatment options are available for recurrent hormone refractory prostate cancer (HRPC), it is imperative to assess whether the prostate-specific antigen (PSA) promoter-based TSTA gene therapy will be functional in HRPC.

EXPERIMENTAL DESIGN

We tested the TSTA-driven adenovirus vector on three androgen-dependent and six HRPC models. Real-time gene expression was monitored by both optical imaging and the combined modality of positron emission tomography (PET) and computed tomography.

RESULTS

The TSTA-driven firefly luciferase expressing adenoviral vector was active in all androgen receptor (AR)-expressing HRPC models, but inactive in AR- and PSA-negative lines. Interestingly, the TSTA-mediated gene expression was induced by hydrocortisone in MDA PCa 2b, a cell line with mutated AR that possesses altered ligand specificity. In animal models, the TSTA-mediated optical signal was more robust in the HRPC than androgen-dependent tumors. In a parallel trend, a TSTA vector that expresses the herpes simplex virus thymidine kinase PET reporter gene also displayed more robust PET signal in the HRPC tumor.

CONCLUSIONS

The activity of TSTA system is AR dependent and it recapitulates the functional status of endogenous AR. These data support the conclusion that AR function is activated in HRPC despite castrated levels of androgen. Together with the fact that majority of recurrent prostate cancers express AR and PSA, we foresee that the TSTA approach can be a promising gene therapy strategy for the advanced stages of prostate cancer.

Combined application of RT-PCR and immunohistochemistry on paraffin embedded sentinel lymph nodes of prostate cancer patients

The detection of tumor cells in the sentinel lymph node (SLN) is of great importance for the prognosis of cancer patients. At present, immunohistochemistry and RT-PCR for tumor marker expression are the most sensitive techniques available for this analysis. However, so far, most RT-PCR-based analyses of SLNs have been performed on fresh material, excluding a direct comparison with the (immuno)histologic results. In our view, this does not entirely aid routine diagnosis. We established an efficient method for RNA extraction and RT-PCR from paraffin sections of SLNs from prostate cancer patients and compared the results with the (immuno)histologic data of adjacent sections. Amplifiable RNA was obtained from 133 SLNs of 68 prostate cancer patients. Correlation of PSA-specific RT-PCR with (immuno)histologic findings showed a positive and negative predictive value of 83% and 100%, respectively, for the prostate cancer patients investigated. Four of 12 patients with biochemical relapse, but without (immuno)histologically detectable tumor cells were RT-PCR-positive for PSA. We found that single sections of paraffin-embedded SLNs are suitable for routinely performed RT-PCR. Combined with (immuno)histology, PSA-specific RT-PCR is a revealing supplementary technique for the detection of tumor cells in SLNs of prostate cancer patients.

Differential immunization identifies PHB1/PHB2 as blood-borne tumor antigens

Early diagnosis of cancer is crucial for successful treatment. Noninvasive assays for detecting tumor-derived antigens in serum and other bodily fluids have the potential to screen healthy individuals for hitherto undetected cancers. Very few such assays have been successfully developed, in part because identifying potential target antigens remains a challenge. To identify new blood-borne tumor antigens for the purpose of establishing such assays, we have developed a novel technique called differential immunization. Using this method, we have identified PHB1 and PHB2, proteins thought to function as mitochondrial chaperones and transcriptional regulators, as antigens released from colorectal tumors in vivo. Serum from colorectal patients contains significantly higher levels of these antigens compared to serum from healthy volunteers. These data demonstrate that differential immunization is an effective new method for identifying tumor-derived antigens in serum.

Serum levels of IL-6 and TNF-alpha correlate with clinicopathological features and patient survival in patients with prostate cancer

Interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-α) are important multifunctional cytokines involved in tumour growth and metastasis. In this study, we have measured serial levels of serum IL-6 and TNF-α in prostate cancer patients. A total of 80 patients with carcinoma of the prostate and 38 controls were studied. Three patient groups, with small bulk localised, large volume localised and metastatic prostate cancer, were assessed. Serum IL-6 and TNF-α levels were measured and correlated with clinicopathological variables and patient survival. Serial changes in these cytokines were also assessed and related to disease progression in 40 patients with recurrent prostate cancer. Serum IL-6 levels in patients with metastatic disease (9.3±7.8 pg ml⁻¹) were higher than those in patients with localised disease (1.3±0.8 pg ml⁻¹, P<0.001). Significantly elevated levels of TNF-α were found in metastatic disease (6.3±3.6 pg ml⁻¹) compared with localised disease (1.1±0.5 pg ml⁻¹, P<0.001). The levels of both cytokines were directly correlated with the extent of the disease. Serial analysis in 40 patients with recurrent tumours showed that both cytokines became elevated at the point of prostate-specific antigen progression. In conclusion, these results suggest that IL-6 and TNF-α correlate with the extent of disease in patients with prostate cancer and may be monitored in conjunction with other disease markers.

Optimization of adenoviral vectors to direct highly amplified prostate-specific expression for imaging and gene therapy

Gene expression-based imaging coupled to gene therapy will permit the prediction of therapeutic outcome. A significant challenge for successful gene therapy is to achieve a high-level of specific gene expression; however, tissue-specific promoters are weak. We postulate that if the weak activity of tissue-specific promoters can be amplified to the levels of strong viral promoters, which have been successful in preclinical scenarios, while retaining specificity, the therapeutic index of gene therapy can be greatly augmented. With this in mind, we developed a two-step transcriptional activation (TSTA) system. In this two-tiered system, a modified prostate-specific antigen promoter was employed to drive a potent synthetic transcriptional activator, GAL4-VP2. This, in turn, activated the expression of a GAL4-dependent reporter or therapeutic gene. Here we demonstrate that recombinant adenoviral vectors (Ads) in which we have incorporated prostate-targeted TSTA expression cassettes retain cell specificity and androgen responsiveness in cell culture and in animal models, as measured by noninvasive optical bioluminescence imaging. We investigated the mechanism of TSTA in different adenoviral configurations. In one configuration, both the activator and the reporter components are inserted into a single Ad (AdTSTA-FL). The activity of AdTSTA-FL exceeds that of a cytomegalovirus promoter-driven vector (AdCMV-FL), while maintaining tissue specificity. When the activator and reporter components are placed in two separate Ads, androgen induction is more robust than for the single AdTSTA-FL. Based on these findings, we hope to refine the TSTA Ads further to improve the efficacy and safety of prostate cancer gene therapy.

Molecular and genetic prognostic factors of prostate cancer

Prostate cancer is the most commonly diagnosed cancer in Western males, responsible for 3% of all deaths in men over 55 years of age and second only to lung cancer as a cause of cancer death. Biomarkers have become an important diagnostic tool in prostate cancer. The discovery of the serum marker prostate-specific antigen (PSA) significantly facilitated the detection and management of prostate cancer. As we enter into the post-genomics era, novel biomarkers of prostate cancer of therapeutic significance will invariably emerge. Here we review a series of existing and emerging molecular-based prognostic markers particularly with radiotherapy.

Prostate cancer biomarkers: a current perspective

Genomic- and proteomic-based studies have led to the identification of a large number of candidate biomarkers, as well as signature patterns of multiple markers for prostate cancer diagnosis, disease progression and prediction of survival. While these candidates include the usual suspects, including oncogenes, proliferation markers and cytoskeletal proteins, there are many additional unexpected molecules such as those involved in processes such as transcriptional repression and fatty acid metabolism. Patterns of expression serving as useful biomarkers is a new and, as yet, clinically untested concept which promises to permit a consideration of the complex milieu of cancer. Exciting as these developments are, clinical application will have to await careful validation of these candidates by independent biochemical approaches over large and diverse samples.

Challenges to cancer control by screening

Population-based screening seems to be a common-sense strategy for controlling cancer, but recent reports have raised controversy concerning the benefits of common screening procedures. Intense efforts to develop and evaluate novel screening technologies are underway; however, effective use of any screening method must take into account any underlying biological considerations. What are these biological issues, and what challenges do clinicians face in screening for common cancers?