Emerging Biomarkers for the Diagnosis and Prognosis of Prostate Cancer

The failure of protein cancer biomarkers to reach the clinic: why, and what can be done to address the problem?

There is a plethora of published cancer biomarkers but the reality is that very few, if any, new circulating cancer biomarkers have entered the clinic in the last 30 years. I here try to explain this apparent oxymoron by classifying circulating cancer biomarkers into three categories: fraudulent reports (rare); true discoveries of biomarkers, that then fail to meet the demands of the clinic; and false discoveries, which represent artifactual biomarkers. I further provide examples of combinations of some known cancer biomarkers that can perform well in niche clinical applications, despite individually being not useful.

The role of combined measurement of tissue mRNA levels of AMACR and survivin in the diagnosis and risk stratification of patients with suspected prostate cancer

AIM

To determine whether the measurement of tissue mRNA levels of AMACR and survivin has a role in distinguishing prostate cancer (PCa) from benign lesions and high risk from low-risk PCa in men with suspected PCa.

METHODS

TRUS prostate biopsies from 170 patients with suspected PCa were used to measure the mRNA levels of AMACR and survivin using semi-quantitative RT-PCR technique. The diagnosis, staging and risk stratification of PCa was based on established clinical criteria. The ability of tissue mRNA levels to distinguish benign from malignant prostate and high- and low-risk PCa was assessed. The diagnostic value for the two genes was evaluated by calculating their individual and combined sensitivity and specificity, which were compared with that of PSA.

RESULTS

Histological examination showed 90/170 (53%) of patients had benign prostate pathology, while 80/170 (47%) had PCa. Tissue mRNA levels of both AMACR and survivin were able to distinguish benign from PCa biopsies (p<0.0001) and also high-risk from low-risk PCa cases (p<0.02, p<0.05, respectively). Compared with serum PSA levels, the combined use of tissue mRNA levels of AMACR and survivin yielded a higher detection specificity (84 vs. 22%).

CONCLUSION

Based on AMACR and survivin combined sensitivity and specificity, these mRNA markers can be used as an adjunct to distinguish patients with and without PCa and in men with PCa may help to identify those with low- or high-risk PCa.

Development of an ELISA to detect the secreted prostate cancer biomarker AGR2 in voided urine

BACKGROUND

Comparative transcriptomics between sorted cells identified AGR2 as one of the highest up-regulated genes in cancer. Overexpression in primary tumors was verified by tissue microarray analysis. AGR2 encodes a 19-kDa secreted protein that might be found in urine.

METHODS

Monoclonal antibodies were generated against AGR2. One antibody pair, P1G4 (IgG1) to capture and P3A5 (IgG2a) to detect, showed good performance characteristics in a sandwich ELISA. This assay could detect AGR2 at sub ng/ml quantities.

RESULTS

AGR2 was detected in tissue digestion media of tumor specimens and culture media of AGR2-secreting prostate cancer cell lines. Additional testings involved frozen section immunohistochemistry, immunoprecipitation, and Western blot analysis. Voided urine samples were collected from pre-operative cancer patients, and urinary protein was desalted and concentrated by filtration. The amount of AGR2 detected was scored as pg/100 µg total protein, and then converted to pg/ml urine. The developed ELISA detected AGR2 protein, ranging from 3.6 to 181 pg/ml, in an initial cohort of samples. AGR2 was not detected in the urine of non-cancer and a bladder cancer patient.

CONCLUSIONS

For prostate cancer, an AGR2 urine test could be used for diagnosis. The data, although derived from a small number of samples assayed, showed that developing such a test for clinical application is viable because AGR2 is specific to cancer cells, and apparently secreted into urine.

A search for reliable molecular markers of prognosis in prostate cancer: a study of 240 cases

Most prostate cancers are treated, although more than 80% remain clinically insignificant and fewer than 3% are fatal. This retrospective study of 240 radical prostatectomy cases with comprehensive follow-up was a search for reliable markers of prostate cancer prognosis evaluable on biopsy specimens to enable minimization of unnecessary treatment, morbidity, and costs. Representative cancer and benign tissue from each prostatectomy specimen was made into tissue microarrays and stained with antibodies targeting 20 gene sequences. Traditional clinical and pathologic prognosticators and the 20 antibody stains were correlated with patient outcomes. By univariable analysis 4 of 20 antibodies (STMN1/stathmin 1, CYP4Z1/cytochrome p450-4z1, CDH1/E-cadherin, and Hey2), Gleason score, perineural invasion, and apical involvement were statistically significant outcome predictors for biopsy tissue. By multivariate analysis, Gleason score, Hey2, and CYP4Z1 were independently predictive. STMN1 and CDH1 were not independent of Gleason score but remain useful because marker interpretation is objective and Gleason scores often differ for biopsy and prostatectomy specimens.

Prostate cancer targeting motifs: expression of αν β3, neurotensin receptor 1, prostate specific membrane antigen, and prostate stem cell antigen in human prostate cancer cell lines and xenografts

BACKGROUND

Membrane receptors are frequent targets of cancer therapeutic and imaging agents. However, promising in vitro results often do not translate to in vivo clinical applications. To better understand this obstacle, we measured the expression differences in receptor signatures among several human prostate cancer cell lines and xenografts as a function of tumorigenicity.

METHODS

Messenger RNA and protein expression levels for integrin α(ν) β(3), neurotensin receptor 1 (NTSR1), prostate specific membrane antigen (PSMA), and prostate stem cell antigen (PSCA) were measured in LNCaP, C4-2, and PC-3 human prostate cancer cell lines and in murine xenografts using quantitative reverse transcriptase polymerase chain reaction, flow cytometry, and immunohistochemistry.

RESULTS

Stable expression patterns were observed for integrin α(ν) and PSMA in all cells and corresponding xenografts. Integrin β(3) mRNA expression was greatly reduced in C4-2 xenografts and greatly elevated in PC-3 xenografts compared with the corresponding cultured cells. NTSR1 mRNA expression was greatly elevated in LNCaP and PC-3 xenografts. PSCA mRNA expression was elevated in C4-2 xenografts when compared with C4-2 cells cultured in vitro. Furthermore, at the protein level, PSCA was re-expressed in all xenografts compared with cells in culture.

CONCLUSIONS

The regulation of mRNA and protein expression of the cell-surface target proteins α(ν) β(3), NTSR1, PSMA, and PSCA, in prostate cancer cells with different tumorigenic potential, was influenced by factors of the microenvironment, differing between cell cultures and murine xenotransplants. Integrin α(ν) β(3), NTRS1 and PSCA mRNA expression increased with tumorigenic potential, but mRNA expression levels for these proteins do not translate directly to equivalent expression levels of membrane bound protein.

Assessing prostate cancer growth with citrate measured by intact tissue proton magnetic resonance spectroscopy

BACKGROUND

Annual PSA tests have led to a significant increase in the number of prostate cancer (PCa) cases diagnosed. This increased incidence has led to overtreatment of many patients, as current pathology often cannot distinguish latent from aggressive PCa. Studies have shown that the depletion of zinc in prostate cells correlated with cell-line growth rates, and may therefore relate to the progression of PCa. Furthermore, as zinc is normally an inhibitor of citrate oxidation, the reduction of zinc in PCa may cause a decrease in citrate secretion levels in the glandular epithelia of PCa patients.

METHODS

Using high-resolution magic angle spinning proton magnetic resonance spectroscopy followed by quantitative histopathology, we investigate unit histo-benign prostate epithelial citrate concentrations in intact tissue samples obtained from 18 patients with pre-surgical PSA values less than 20 ng/ml. Using these data, we evaluate correlations between citrate concentrations and PSA velocities, densities and blood percent-free PSA.

RESULTS

We observe different linear patterns between citrate concentrations and histo-benign glandular epithelia from patients of different PSA velocities. More importantly, we obtain a significant correlation between PSA velocity, density and percent-free PSA, and citrate concentrations in unit volume of histo-benign epithelial glands of the peripheral zone.

CONCLUSIONS

Low levels of citrate in unit volume represent rapidly increasing PSA values, and, therefore, may be used as an indicator of fast-growing PCa. Thus, tissue samples obtained at the time of biopsy may be evaluated for their citrate concentrations for the prediction of PCa growth rates, allowing for the implementation of alternative treatment options and reducing overtreatment.

New insights into the mechanisms of green tea catechins in the chemoprevention of prostate cancer

Prostate cancer is the most commonly diagnosed cancer and second most common cause of cancer deaths in American men. Its long latency, slow progression, and high incidence rate make prostate cancer ideal for targeted chemopreventative therapies. Therefore, chemoprevention studies and clinical trials are essential for reducing the burden of prostate cancer on society. Epidemiological studies suggest that tea consumption has protective effects against a variety of human cancers, including that of the prostate. Laboratory and clinical studies have demonstrated that green tea components, specifically the green tea catechin (GTC) epigallocatechin gallate, can induce apoptosis, suppress progression, and inhibit invasion and metastasis of prostate cancer. Multiple mechanisms are involved in the chemoprevention of prostate cancer with GTCs; understanding and refining models of fundamental molecular pathways by which GTCs modulate prostate carcinogenesis is essential to apply the utilization of green tea for the chemoprevention of prostate cancer in clinical settings. The objective of this article is to review and summarize the most current literature focusing on the major mechanisms of GTC chemopreventative action on prostate cancer from laboratory, in vitro, and in vivo studies, and clinical chemoprevention trials.

Elevated levels of Dickkopf-related protein 3 in seminal plasma of prostate cancer patients

BACKGROUND

Expression of Dkk-3, a secreted putative tumor suppressor, is altered in age-related proliferative disorders of the human prostate. We now investigated the suitability of Dkk-3 as a diagnostic biomarker for prostate cancer (PCa) in seminal plasma (SP).

METHODS

SP samples were obtained from 81 patients prior to TRUS-guided prostate biopsies on the basis of elevated serum prostate-specific antigen (PSA; > 4 ng/mL) levels and/or abnormal digital rectal examination. A sensitive indirect immunoenzymometric assay for Dkk-3 was developed and characterized in detail. SP Dkk-3 and PSA levels were determined and normalized to total SP protein. The diagnostic accuracies of single markers including serum PSA and multivariate models to discriminate patients with positive (N = 40) and negative (N = 41) biopsy findings were investigated.

RESULTS

Biopsy-confirmed PCa showed significantly higher SP Dkk-3 levels (100.9 ± 12.3 vs. 69.2 ± 9.4 fmol/mg; p = 0.026). Diagnostic accuracy (AUC) of SP Dkk-3 levels (0.633) was enhanced in multivariate models by including serum PSA (model A; AUC 0.658) or both, serum and SP PSA levels (model B; AUC 0.710). In a subpopulation with clinical follow-up > 3 years post-biopsy to ensure veracity of negative biopsy status (positive biopsy N = 21; negative biopsy N = 25) AUCs for SP Dkk-3, model A and B increased to 0.667, 0.724 and 0.777, respectively.

CONCLUSIONS

In multivariate models to detect PCa, inclusion of SP Dkk-3 levels, which were significantly elevated in biopsy-confirmed PCa patients, improved the diagnostic performance compared with serum PSA only.

Biomarkers in prostate cancer epidemiology

Understanding the etiology of a disease such as prostate cancer may help in identifying populations at high risk, timely intervention of the disease, and proper treatment. Biomarkers, along with exposure history and clinical data, are useful tools to achieve these goals. Individual risk and population incidence of prostate cancer result from the intervention of genetic susceptibility and exposure. Biochemical, epigenetic, genetic, and imaging biomarkers are used to identify people at high risk for developing prostate cancer. In cancer epidemiology, epigenetic biomarkers offer advantages over other types of biomarkers because they are expressed against a person's genetic background and environmental exposure, and because abnormal events occur early in cancer development, which includes several epigenetic alterations in cancer cells. This article describes different biomarkers that have potential use in studying the epidemiology of prostate cancer. We also discuss the characteristics of an ideal biomarker for prostate cancer, and technologies utilized for biomarker assays. Among epigenetic biomarkers, most reports indicate GSTP1 hypermethylation as the diagnostic marker for prostate cancer; however, NKX2-5, CLSTN1, SPOCK2, SLC16A12, DPYS, and NSE1 also have been reported to be regulated by methylation mechanisms in prostate cancer. Current challenges in utilization of biomarkers in prostate cancer diagnosis and epidemiologic studies and potential solutions also are discussed.

Electrophoretic fingerprint metallothionein analysis as a potential prostate cancer biomarker

Prostate-specific antigen (PSA) is a routinely used marker of prostate cancer; however, the cut-off values for unambiguous positive/negative prostate cancer diagnoses are not defined. Therefore, despite the best effort, certain percentage of misdiagnosed cases is being recorded every year. For this reason, search for more specific diagnostic markers is of great interest. In this study, systematic comparison of PSA and metallothionein (MT) levels in blood serum of 46 prostate cancer-diagnosed patients is presented. It is clearly demonstrated that PSA levels vary significantly and despite normal total PSA values in the range of 0 - 4 ng/mL were obtained in over 36.9% of cases, positive prostate cancer was diagnosed by biopsy. In contrary, MT levels were considerably elevated in all tested samples and no significant variations were observed. These results are indicating the potential of MT as an additional prostate cancer marker reducing, in combination with PSA, the probability of false positive/negative diagnosis. To increase the throughput of the screening, chip-based capillary electrophoresis was suggested as a rapid and effective method for the fingerprinting analysis of prostate cancer from diseased blood sera.

Elevated serum matrix metalloproteinase 7 levels predict poor prognosis after radical prostatectomy

Elevated matrix metalloproteinase-7 (MMP-7) tissue expression and serum concentration have been shown to be associated with cancer progression and metastasis. The aim of our study was to assess the prognostic value of preoperative circulating MMP-7 levels in serum samples of patients with clinically localized prostate cancer. Furthermore, we compared the serum MMP-7 levels between patients with organ confined and metastatic prostate cancer. MMP-7 levels were measured in 93 patients with localized prostate cancer, 13 patients with distant bone metastasis and in sera of 19 controls using enzyme-linked immunosorbent assay. The results were compared to the clinical follow-up data. We did not find any significant difference in MMP-7 serum levels between patients and controls (p = 0.268). Circulating MMP-7 serum concentration was significantly elevated in patients with distant metastasis (p < 0.001). For the detection of distant prostate cancer metastasis, using a cut-off value of 3.7 ng/ml, a specificity of 69% and a sensitivity of 92% were observed. Multivariate analysis identified high MMP-7 serum concentration as an independent risk factor for prostate cancer-related death both in a preoperative and a postoperative model (p = 0.003 and 0.018, respectively). Furthermore, the evaluation of predictive models revealed that addition of serum MMP-7 levels to the preoperatively available predictors improves prognostic accuracy (the concordance index increased from 0.631 to 0.734 when MMP-7 was included). Based on these, we concluded that MMP-7 is a potential marker to identify patients with metastatic prostate cancer. In clinically localized prostate cancer, MMP-7 may provide independent prognostic information, thereby helping to optimize therapy decisions.

Urine markers and prostate cancer

Prostate cancer (PCa) is globally the most common cancer in men, with an estimated prevalence of more than two million cases. Given the poor success rate in treating advanced PCa, intervention in early stages may reduce the progression of a small, localized carcinoma to a large metastatic lesion, thereby reducing disease-related deaths. Urine is readily available and can be used to detect either exfoliated cancer cells or secreted products. The major advantages of urine-based assays are their noninvasive character and ability to monitor PCa with heterogeneous foci. The aim of this review was to summarize the current evidence regarding performance characteristics of tests proposed for urine-based prostate cancer detection.

Biomarkers for early detection and as surrogate endpoints in cancer prevention trials: issues and opportunities

In order to improve the early detection and diagnosis of cancer, give more accurate prognoses, stratify individuals by risk, predict response to treatment, and help the transition of basic research into clinical application, biomarkers are needed that accurately represent or predict clinical outcomes. To be useful in trials for chemopreventive agent development, biomarkers must be subject to modulation, easy to obtain and quantify, and have biological meaning, ideally representing steps in well-understood carcinogenic pathways. Though difficult to validate fully, wisely chosen biomarkers in early-phase trials can inform the prioritization of large-scale, long-term trials that measure clinical outcomes. When well-designed, smaller trials using biomarkers as surrogate endpoints should promote faster decisions regarding which targeted preventive agents to pursue, promising greater progress in the personalization of medicine. Biomarkers could become useful in distinguishing indolent from aggressive forms of ductal carcinoma in situ as well as localized invasive breast and prostate cancer, lesions that are often overtreated. Chemopreventive strategies that reduce the progression of early forms of premalignancy can benefit patients not only by reducing their risk of cancer and death from cancer but also by reducing their need for invasive interventions. Genomic and proteomic methods offer the possibility of revealing new potential markers, especially for diseases whose biology is complex or not well understood. Panels of markers may be used to accommodate the molecular heterogeneity of cancers. Biomarkers in phase 2 prevention trials of combinations of chemopreventive drugs have been used to demonstrate synergistic action of multiple agents, allowing use of lower doses, with less toxicity, a critical feature of interventions intended for cancer prevention.

Endothelin-1: a predictor of extracapsular extension in clinically localized prostate cancer?

OBJECTIVE

To assess the value of endothelin-1 (ET-1) expression in predicting extracapsular extension (ECE) in clinically localized prostate cancer (PCa).

PATIENTS AND METHODS

ET-1 expression was determined by immunohistochemistry on archival needle biopsies (NBs) from 94 patients (49 pT2 and 45 pT3a) who underwent radical prostatectomy (RP) for clinical T1-T2 PCa. Each sample was analysed independently by two pathologists blinded to the clinical data.

RESULTS

In univariate analysis, high ET-1 expression in NBs, pre-operative prostate-specific antigen (PSA) level >10 ng/ml, percentage of positive biopsy cores and NB Gleason score ≥7 were significantly associated with ECE as determined on subsequent RP. No significant association was found between clinical stage and ECE. In multivariate analysis, there was a significant association with high ET-1 expression in NBs (p = 0.006), pre-operative PSA level >10 ng/ml (p = 0.049), and NB Gleason score ≥7 (p = 0.002). These three pre-operative factors combined provided the best model for predicting ECE with 93.3% sensitivity, 49% specificity, 62.5% positive predictive value, 88.9% negative predictive value. The combination yielded a higher concordance index (0.760 vs 0.720) and offered a higher log partial likelihood than the same model without ET1 (112.8 vs 105.7, p = 0.01).

CONCLUSIONS

ET-1 expression was strongly associated with ECE and, when combined with pre-operative PSA level and Gleason score, improved the predictive accuracy of pre-operative NBs. Its assessment in patients with localized PCa might be useful when making treatment decisions. Further studies with standardisation of immunohistochemical staining and multi-institutional validation are now needed to establish the appropriate use of ET-1 staining in PCa staging and to evaluate inter-observer reproducibility.

Osteopontin is a tumor autoantigen in prostate cancer patients

Anti-tumor antibodies act as biomarkers for the early diagnosis of prostate cancer (PCa). Osteopontin (OPN) is overexpressed in PCa cells and contributes to the progression of the disease. This study aimed to evaluate whether OPN evokes a humoral immune response in PCa patients and whether the reactivity levels of anti-OPN antibodies may be used to better differentiate PCa from benign and healthy donor plasma samples. Plasma samples from biopsy-proven PCa patients (29), benign prostate hyperplasia (BPH) (18) and control healthy donors (HD) (30) were tested by immunoblots using the recombinant human OPN. The frequency of anti-OPN antibodies was significantly higher in PCa (66%) plasma samples as compared to BPH (33%) and HD controls (10%). Anti-OPN antibodies were detected in a high proportion of plasma samples from patients with a Gleason score of less than 6 (57%), prostate-specific antigen levels lower than 10 ng/ml (67%) and pT2 organ-confined disease (70%), suggesting that anti-OPN antibodies may be used as an early serum marker for PCa. To the best of our knowledge, this is the first description of OPN as a tumor autoantigen and one of the most reactive individual autoantigens described thus far. These data support the inclusion of OPN in a multiplex of tumor antigens in order to perform antibody profiling in PCa as well as in other malignancies overexpressing OPN.

GAD1 is a biomarker for benign and malignant prostatic tissue

OBJECTIVE

Tissue-specific markers are useful for identification of tumour type in advanced cancers of unknown origin. This study investigated the expression of glutamate decarboxylase 1 (GAD1) in prostate and control tissue compared with the established prostate-specific markers prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSMA).

MATERIAL AND METHODS

A tissue microarray was constructed of 36 prostate adenocarcinomas, eight benign prostate samples and benign and malignant control tissues from urinary bladder, lung and rectum. Immunohistochemistry for GAD1, PSA and PSMA was performed. The products of staining intensity and extent were analysed. The GAD1 antibody was validated by Western blot. Real-time polymerase chain reaction (RT-PCR) was performed on malignant and benign samples from each tissue type.

RESULTS

GAD1 and PSA immunostains were significantly stronger in malignant and benign prostatic tissue than in controls. PSMA was stronger in prostate cancer than in urothelial and rectal cancer but had a lower specificity than GAD1 and PSA. GAD1 expression decreased with increasing Gleason score. RT-PCR confirmed the presence of mRNA for GAD1, PSA and PSMA in prostate samples.

CONCLUSION

GAD1 is expressed in benign and malignant prostatic tissue and may serve as a highly prostate-specific tissue biomarker.

Novel diagnostic biomarkers for prostate cancer

Prostate cancer is the most frequently diagnosed malignancy in American men, and a more aggressive form of the disease is particularly prevalent among African Americans. The therapeutic success rate for prostate cancer can be tremendously improved if the disease is diagnosed early. Thus, a successful therapy for this disease depends heavily on the clinical indicators (biomarkers) for early detection of the presence and progression of the disease, as well as the prediction after the clinical intervention. However, the current clinical biomarkers for prostate cancer are not ideal as there remains a lack of reliable biomarkers that can specifically distinguish between those patients who should be treated adequately to stop the aggressive form of the disease and those who should avoid overtreatment of the indolent form.

A biomarker is a characteristic that is objectively measured and evaluated as an indicator of normal biologic processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention. A biomarker reveals further information to presently existing clinical and pathological analysis. It facilitates screening and detecting the cancer, monitoring the progression of the disease, and predicting the prognosis and survival after clinical intervention. A biomarker can also be used to evaluate the process of drug development, and, optimally, to improve the efficacy and safety of cancer treatment by enabling physicians to tailor treatment for individual patients. The form of the prostate cancer biomarkers can vary from metabolites and chemical products present in body fluid to genes and proteins in the prostate tissues.

Current advances in molecular techniques have provided new tools facilitating the discovery of new biomarkers for prostate cancer. These emerging biomarkers will be beneficial and critical in developing new and clinically reliable indicators that will have a high specificity for the diagnosis and prognosis of prostate cancer. The purpose of this review is to examine the current status of prostate cancer biomarkers, with special emphasis on emerging markers, by evaluating their diagnostic and prognostic potentials. Both genes and proteins that reveal loss, mutation, or variation in expression between normal prostate and cancerous prostate tissues will be covered in this article. Along with the discovery of prostate cancer biomarkers, we will describe the criteria used when selecting potential biomarkers for further development towards clinical use. In addition, we will address how to appraise and validate candidate markers for prostate cancer and some relevant issues involved in these processes. We will also discuss the new concept of the biomarkers, existing challenges, and perspectives of biomarker development.

Molecular markers for early detection

A common belief is that the earlier that cancer is detected, the better the chance exists for reduced mortality and morbidity. The advent of new and emerging molecular, genetic, and imaging technologies has broadened the possible strategies for early detection and prevention, but a beneficial impact on mortality needs to be supported by clinical evidence. Molecular markers are being identified that are enhancing our ability to predict and detect cancer before it develops and at the earliest signs of impending carcinogenic transformation. Of the innumerable molecular markers in development, a standalone early detection marker with acceptable sensitivity and specificity is available for bladder cancer, although for most cancer sites there are promising avenues of research that will likely produce results in the next decade. The perfect molecular marker would be one that is inherently related to the disease, specifically to the processes of malignant tumorigenesis or to the defense mechanisms of the individual. For example, mutations associated with increased cancer risk often produce gene products that interfere with tumor-suppressor pathways (eg, DNA repair or cell-cycle control) or support oncogenic pathways (eg, through genetic instability or silencing the apoptotic pathway). Finding molecular markers associated with these processes, and where in the process they produce their actions, can lead to interventions based on maintaining support for the normal process and interrupting the action of the products of the mutation. The search for molecular markers for cancer prevention and early detection presents a formidable challenge that requires a systematic and scientifically sound validation process. The search encompasses a broad range of scientific disciplines, including biochemistry, genetics, histology, immunology, informatic technologies, and epidemiology; strategies to identify and understand molecular markers are approached with multidisciplinary teams focused on understanding the mechanistic basis of cancer and the processes and pathways that underlie carcinogenesis.

Cancer biomarker discovery: the entropic hallmark

Background

It is a commonly accepted belief that cancer cells modify their transcriptional state during the progression of the disease. We propose that the progression of cancer cells towards malignant phenotypes can be efficiently tracked using high-throughput technologies that follow the gradual changes observed in the gene expression profiles by employing Shannon's mathematical theory of communication. Methods based on Information Theory can then quantify the divergence of cancer cells' transcriptional profiles from those of normally appearing cells of the originating tissues. The relevance of the proposed methods can be evaluated using microarray datasets available in the public domain but the method is in principle applicable to other high-throughput methods.

Methodology/Principal Findings

Using melanoma and prostate cancer datasets we illustrate how it is possible to employ Shannon Entropy and the Jensen-Shannon divergence to trace the transcriptional changes progression of the disease. We establish how the variations of these two measures correlate with established biomarkers of cancer progression. The Information Theory measures allow us to identify novel biomarkers for both progressive and relatively more sudden transcriptional changes leading to malignant phenotypes. At the same time, the methodology was able to validate a large number of genes and processes that seem to be implicated in the progression of melanoma and prostate cancer.

Conclusions/Significance

We thus present a quantitative guiding rule, a new unifying hallmark of cancer: the cancer cell's transcriptome changes lead to measurable observed transitions of Normalized Shannon Entropy values (as measured by high-througput technologies). At the same time, tumor cells increment their divergence from the normal tissue profile increasing their disorder via creation of states that we might not directly measure. This unifying hallmark allows, via the the Jensen-Shannon divergence, to identify the arrow of time of the processes from the gene expression profiles, and helps to map the phenotypical and molecular hallmarks of specific cancer subtypes. The deep mathematical basis of the approach allows us to suggest that this principle is, hopefully, of general applicability for other diseases.

Prognostic value and biological role of the kallikrein-related peptidases in human malignancies

Cancer is a substantial health problem for the populations of the Western world. The discovery of new molecular biomarkers for diagnosis, prognosis and monitoring patients' response to therapy can aid in combating this complicated disease. The human kallikrein-related peptidases (human tissue kallikreins [KLKs]) are encoded by a continuous multigene family, located on chromosomal region 19q13.3-4. KLK3 (prostate-specific antigen) is the most efficient cancer biomarker ever employed. KLK genes are expressed abnormally in various malignancies, where they affect cancer-cell growth and metastasis. Their deregulated expression pattern, often associated with various clinicopathological characteristics of cancer patients, can be exploited, solely or within multiparametric panels, as a prognostic biomarker. Recent data illustrate that discernible molecular modulations of KLKs, occurring as a result of cancer cells' treatment with antitumor agents, may serve as new potential biomarkers, possibly predicting patients' treatment response. It is believed that KLKs might be employed in future clinical practice as novel and effective tumor markers.

The cancer cell secretome: a good source for discovering biomarkers?

Cancer is a leading cause of death. Early detection is usually associated with better clinical outcomes. Recent advances in genomics and proteomics raised hopes that new biomarkers for diagnosis, prognosis or monitoring therapeutic response will soon be discovered. Proteins secreted by cancer cells, referred also as "the cancer cell secretome", is a promising source for biomarker discovery. In this review we will summarize recent advances in cancer cell secretome analysis, focusing on the five most fatal cancers (lung, breast, prostate, colorectal, and pancreatic). For each cancer type we will describe the proteomic approaches utilized for the identification of novel biomarkers. Despite progress, identification of markers that are superior to those currently used has proven to be a difficult task and very few, if any, newly discovered biomarker has entered the clinic the last 10 years.

Biomarkers for prostate cancer detection

Since its approval by the US FDA in 1986, prostate-specific antigen (PSA) has been employed to monitor men with a diagnosis of prostate cancer. In 1994, PSA was approved for use in prostate cancer screening and has been employed worldwide. However, due to the limited specificity of PSA for the disease, novel biomarkers are needed for detecting prostate cancer and for determining which cancers need to be treated. This review will discuss the development of new biomarkers for prostate cancer detection and disease prognostication, focusing on recent progress and particular topical issues related to the development and validation of these new markers.

Polymorphisms of pro-inflammatory genes and prostate cancer risk: a pharmacogenomic approach

In this paper, we consider the role of the genetics of inflammation in the pathophysiology of prostate cancer (PCa). This paper is not an extensive review of the literature, rather it is an expert opinion based on data from authors' laboratories on age-related diseases and inflammation. The aim is the detection of a risk profile that potentially allows both the early identification of individuals at risk for disease and the possible discovery of potential targets for medication. In fact, a major goal of clinical research is to improve early detection of age-related diseases, cancer included, by developing tools to move diagnosis backward in disease temporal course, i.e., before the clinical manifestation of the malady, where treatment might play a decisive role in preventing or significantly retarding the manifestation of the disease. The better understanding of the function and the regulation of inflammatory pathway in PCa may help to know the mechanisms of its formation and progression, as well as to identify new targets for the refinement of new treatment such as the pharmacogenomics approach.

TLR4 polymorphisms and ageing: implications for the pathophysiology of age-related diseases

INTRODUCTION

Innate immunity provides a first line of host defense against infection by recognizing and killing microbes while simultaneously activating an instructive immune response. Toll-like receptors (TLRs) are principal mediators of rapid microbial recognition and function mainly by detection of pathogen-associated molecular patterns that do not exist in the host. Recognition of their ligands leads to a series of signaling events resulting in acute host responses, involved in killing pathogens.

DISCUSSION

We describe the involvement of TLR4 polymorphisms in ageing, and in particular in age-related diseases, suggesting the crucial role of molecules of innate immunity in pathophysiology of these diseases. Hence, we observed that pro-inflammatory alleles may be related to unsuccessful ageing, such as Alzheimer's disease, prostate cancer, and atherosclerosis; in contrast, the control of inflammation by anti-inflammatory alleles may result in increased longevity and successful ageing. Finally, a possible therapeutic approach to delay age-related diseases is outlined.

Prostate-specific antigen-based screening for prostate cancer in the third millennium: useful or hype?

Prostate cancer is the most prevalent malignancy in men and the third leading cause of cancer deaths worldwide. Although the wide-spread introduction of total prostate-specific antigen (tPSA) testing has revolutionized the approach to the managed care of this disease, there are some biological, analytical, clinical, and economical issues that argue against the cost-effectiveness of tPSA-based population screening for early identification of cancer. The on-going standardization/harmonization efforts, along with the outcomes of recent epidemiological investigations, demonstrate that the current tPSA thresholds might be revised and possibly recalculated according to several demographical variables, such as age, ethnicity, genotype, family history, and body mass index. A major shortcoming of tPSA screening is the lack of reliable evidences of reduction in prostate cancer-associated mortality, due to the large lead-time because of the indolent growth rate, the impossibility to differentiate high-grade from indolent cancers, and the treatment-associated morbidity. Since no single tPSA cut-off was proven able to efficiently identify men at higher risk of death, the jeopardy of over-diagnosis and over-treatment is also tangible. The large expenditure is an additional source of concern. Finally, a wide-spread population screening also carries several ethical, social, and psychological implications, which might overwhelm the potential benefits.