Biomarkers For Detection Of Prostate Cancer Research Articles

Biomarkers for prostate cancer detection and progression: Beyond prostate-specific antigen

Prostate cancer is a major health problem with an incompletely understood pathogenesis and etiology. The advent of the prostate-specific antigen (PSA) test in the 1980s caused a revolution in how the disease was detected, but the evidence for PSA as a screening test is deficient. Biomarkers have been investigated, both for detection and discrimination of indolent from aggressive cancers. Refinements to the PSA test have been proposed but for practical and evidence-based reasons none have translated through to widespread clinical use. Of the novel biomarkers, the most promising is the prostate cancer antigen 3 (PCA3) test. New biomarkers to predict aggressive disease are even more contentious. The pathological grade of tumor remains the most powerful biomarker of prognosis. Other proven variables include tumor extent on biopsy and serum PSA. Tissue biomarkers have proven unhelpful due to a variable and biased literature with multiple methodological flaws, but Ki-67 probably shows more promise than any other current tissue biomarker. The recent discovery of a family of fusion genes in the prostate has led to considerable discussion on their prognostic role. Dissection of the genetic basis of the disease may lead to discoveries that will enhance our understanding and aid the search for prognostically valuable biomarkers.

Other biomarkers for detecting prostate cancer

Prostate-specific antigen (PSA) has been used for detecting prostate cancer since 1994. Although it is the best cancer biomarker available, PSA is not perfect. It lacks both the sensitivity and specificity to accurately detect the presence of prostate cancer. None of the PSA thresholds currently in use consistently identify patients with prostate cancer and exclude patients without cancer. Novel approaches to improve our ability to detect prostate cancer and predict the course of the disease are needed. Additional methods for detecting prostate cancer have been evaluated. Despite the discovery of many new biomarkers, only a few have shown some clinical value. These markers include human kallikrein 2, urokinase-type plasminogen activator receptor, prostate-specific membrane antigen, early prostate cancer antigen, PCA3, alpha-methylacyl-CoA racemase and glutathione S-transferase pi hypermethylation. We review the reports on biomarkers for prostate cancer detection, and their possible role in the clinical practice.

Biomarkers for prostate cancer

The detection of prostate cancer using a blood test has by many standards changed the face of the disease. Despite this tremendous success, there are limitations attributed to the use of prostate specific antigen (PSA) as a means to screen and detect prostate cancer. PSA, as its name implies, is not specific for prostate cancer and as such is often found elevated in other prostatic diseases/symptoms associated with the aging male. Clearly, more specific marker(s) that could identify which individuals actually have prostate cancer and differentiate them from those without the disease would be of tremendous value. The search for more accurate and clinically useful biomarkers of prostate cancer has been extensive. This has focused on individual markers, as well as groups of markers. Included among these are PSA isoforms, pathological indicators and stains, nucleic acids and others. This article highlights the discovery of PSA as a first blood-based biomarker for prostate cancer detection, as well as other molecular biomarkers and their potential application in detection of the disease.

Beyond PSA: Utility of novel tumor markers in the setting of elevated PSA

The introduction of prostate-specific antigen (PSA) for prostate cancer screening and detection has been used for over 20 years and has dramatically changed the face of prostate cancer. Although it is a highly sensitive serum test, its routine use has been the subject of continued controversy owing to its limited specificity. Due to this lack of specificity, many have proposed modifications of PSA in an attempt to bolster the performance of this analyte. The human genome project and high throughput gene expression profiling has recently yielded several promising molecular biomarkers for prostate cancer detection beyond PSA or PSA modifications. This review will first highlight several characteristics of an ideal biomarker, then focus on select emerging biomarkers for the detection of prostate cancer.

The Role of Prostate Specific Membrane Antigen and Pepsinogen C Tissue Expression as an Adjunctive Method to Prostate Cancer Diagnosis

The diagnosis of prostate cancer in men with persistently increased prostate specific antigen after a negative prostate biopsy has become a great challenge for urologists and pathologists. We analyzed the diagnostic value of 6 genes in the tissue of patients with prostate cancer. The study was comprised of 50 patients with localized disease who underwent radical prostatectomy. Gene selection was based on a previous microarray analysis. Among 4,147 genes with different expressions between 2 pools of patients 6 genes (PSMA, TMEFF2, GREB1, TH1L, IgH3 and PGC) were selected. These genes were tested for diagnostic value using the quantitative reverse transcription polymerase chain reaction method. Initially malignant tissue samples from 33 patients were analyzed and in the second part of the study we analyzed benign tissue samples from the other 17 patients with prostate cancer. The control group was comprised of tissue samples of patients with benign prostatic hyperplasia. Analysis of malignant prostatic tissue demonstrated that prostate specific membrane antigen was over expressed (mean 9 times) and pepsinogen C was under expressed (mean 1.3 x 10(-4) times) in all cases compared to benign prostatic hyperplasia. The other 4 tested genes showed a variable expression pattern not allowing for differentiation between benign and malignant cases. When we tested these results in the benign prostate tissues from patients with cancer, pepsinogen C maintained the expression pattern. In terms of prostate specific membrane antigen, despite over expression in most cases (mean 12 times), 2 cases (12%) presented with under expression. Pepsinogen C tissue expression may constitute a powerful adjunctive method to prostate biopsy in the diagnosis of prostate cancer cases.

Hyperpolarized 13C Lactate, Pyruvate, and Alanine: Noninvasive Biomarkers for Prostate Cancer Detection and Grading

An extraordinary new technique using hyperpolarized (13)C-labeled pyruvate and taking advantage of increased glycolysis in cancer has the potential to improve the way magnetic resonance imaging is used for detection and characterization of prostate cancer. The aim of this study was to quantify, for the first time, differences in hyperpolarized [1-(13)C] pyruvate and its metabolic products between the various histologic grades of prostate cancer using the transgenic adenocarcinoma of mouse prostate (TRAMP) model. Fast spectroscopic imaging techniques were used to image lactate, alanine, and total hyperpolarized carbon (THC = lactate + pyruvate + alanine) from the entire abdomen of normal mice and TRAMP mice with low- and high-grade prostate tumors in 14 s. Within 1 week, the mice were dissected and the tumors were histologically analyzed. Hyperpolarized lactate SNR levels significantly increased (P < 0.05) with cancer development and progression (41 +/- 11, 74 +/- 17, and 154 +/- 24 in normal prostates, low-grade primary tumors, and high-grade primary tumors, respectively) and had a correlation coefficient of 0.95 with the histologic grade. In addition, there was minimal overlap in the lactate levels between the three groups with only one of the seven normal prostates overlapping with the low-grade primary tumors. The amount of THC, a possible measure of substrate uptake, and hyperpolarized alanine also increased with tumor grade but showed more overlap between the groups. In summary, elevated hyperpolarized lactate and potentially THC and alanine are noninvasive biomarkers of prostate cancer presence and histologic grade that could be used in future three-dimensional (13)C spectroscopic imaging studies of prostate cancer patients.

Abstract 4741: Application of nanotechnology for enhanced early detection of prostate cancer in African-American men

Abstract Background: African American men in the US have the highest incidence and mortality from prostate cancer in the world. Five-year survival rates are almost 100% of African American men diagnosed with early stage prostate cancer but only 29% for men diagnosed in the late stages of the disease. Early detection is thus the key to improved mortality and morbidity. We are investigating nanotechnologies to enhance the detection of prostate cancer biomarkers at extremely low levels in blood serum. Our goal is to engineer a multi-biomarker panel that will provide sufficiently high sensitivity and specificity such that it can be applied as a screening test and decrease prostate cancer morbidity and mortality among African-American men. Objectives: 1.To engineer quantum dot - antibody conjugates targeting established prostate cancer biomarkers (antigens): prostate specific antigen (PSA), Kallikrein 2 (KLK2), Kallikrein 14 (KLK14), Osteoprotegerin (OPG), Antip53Ab, Caveolin-1 (Cav-1) and Interleukin-6 (IL-6) 2. To define the photoluminescence signatures of bound versus unbound QDs, reflecting antigen-antibody complex formation. 3. To derive optimal cutpoints for the sensitivity and specificity of the novel QD-conjugated biomarkers individually, and in combination, for the early detection of prostate cancer in African-American men. Results: We have established an African American prostate cancer case-control collection. We have successfully conjugated antibodies to the above biomarkers to quantum dots and these are undergoing characterization. We have observed that the bio-conjugated QD shows a spectral shift of the maximum position on average by 4 nm in comparison to non-conjugated QDs. The shift is towards a shorter wavelengths “blue” shift for conjugated quantum dots. Its existence was confirmed with repetition of the conjugation scheme with identical parameters and the “blue” shift was observed in all repeated experiments. The PL spectral shift observed on bio-conjugated QDs with antigens may be attributed to the existence of an external local electric field that is imposed by the surrounding biomolecules (Stark effect). The shift varied depending on the different antibodies attached and on QDs of different wavelengths. Conclusions: We have observed a spectral shift of the bio-conjugated quantum dots compared to unconjugated quantum dots. The benefit of this observation may lie in the fact that the shift is different for each antibody, thus will show a peak at different wavelengths. This effect may provide a powerful tool for multiplexing proteins for early cancer detection. This study has enormous potential impact on improved detection of this disease in the early and more curable stage which in turn would lead to decreased morbidity and mortality.

Quantum dot‐based protein micro‐ and nanoarrays for detection of prostate cancer biomarkers

In this article, we demonstrate the fabrication and detection of cancer protein biochips consisting of micro- and nanoarrays whereby pegylated quantum dots (QDs) conjugated to antibodies (Abs) of prostate specific antigens (PSA) were used for the detection of clinical biomarkers such as PSA. BSA which acts as an efficient blocking layer in microarrays, tends to show an interaction with QDs. In view of this fact, we investigated two series of samples which were fabricated in the presence and absence of BSA blocking layer. Variation in the incubation time required for the antigen-antibody interaction to take place, different proteins as controls and the effect of bare QDs on these microarrays, were the three main parameters which were studied in these two series. Samples fabricated in the absence of BSA blocking layer exhibited an extremely high specificity in the detection of cancer proteins and were also marked by negligible nonspecific binding effects of QDs, in stark contrast to the samples fabricated using BSA as a blocking layer. Fabrication of nanoarrays of QD-conjugated PSA Abs having a spot size of nearly 900 nm has also been demonstrated. Thus, we show the potential offered by QDs in in vitro analysis of cancer biomarker imaging.

Hypermethylation of MCAM gene is associated with advanced tumor stage in prostate cancer

DNA methylation has emerged as a promising biomarker for prostate cancer detection. In this report, we screened 36 candidate genes generated by a bioinformatic analysis of the human genome, and found that the melanoma cell adhesion molecule (MCAM) was an excellent candidate for cancer-specific methylation in prostate cancer. Direct sequencing of bisulfite-treated genomic DNA, conventional methylation-specific PCR (MSP), real-time quantitative methylation-specific PCR, immunohistochemistry, colony formation assay, and statistical analysis. We found that the melanoma cell adhesion molecule (MCAM) gene promoter was specifically methylated in prostate cancer cell lines and primary prostate cancer (PCa) but not in non-neoplastic prostate (BPH) tissues by direct sequencing of bisulfite-treated genomic DNA and conventional methylation-specific PCR (MSP). Further analysis with quantitative MSP showed greater hypermethylation of the MCAM promoter (80%, 70/88) in primary prostate cancer compared to 12.5% (3/24) in BPH. Prostatic intraepithelial neoplasias (PIN), potential precursors of prostate carcinoma, showed an intermediate methylation rate of 23% (7/30). We further observed that MCAM promoter methylation was directly correlated with tumor stage (pT3+pT4) (P = 0.001) and Gleason score (P = 0.018) in primary prostate carcinoma. Our results suggest that MCAM promoter hypermethylation deserves further attention as a potential diagnostic prostatic DNA marker in human prostate cancer.

Blood Biomarkers For Prostate Cancer Detection and Prognosis

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

Blood-based biomarkers for detecting aggressive prostate cancer at time of biopsy

4637 Background: To date, we have applied our unique methodology (the Sentinel Principle) to identify blood-based gene expressed biomarkers for several diseases including osteoarthritis, bladder cancer and psychiatric disorders. It is well known that new biomarkers for prostate cancer detection are needed, particularly aggressive forms of prostate cancer. Our objective was to identify gene expression signatures and to characterize a set of biomarkers from whole blood to identify patients with aggressive forms of prostate cancer at the time of prostate biopsy. Methods: We conducted a two staged study. The first stage was for gene discovery using microarrays (Affymetrix U133Plus2.0 GeneChips) among 47 patients (all Caucasian) who underwent a prostate biopsy for prostate cancer. We included 16 patients (cases) diagnosed with aggressive forms of prostate cancer defined as having a histologic grade of Gleason Score 7 or more and 31 patients with no evidence of cancer at biopsy (controls). The second stage was a validation study (108 patients) using real-time RT-PCR methods. Logistic regression was used to assess the ability of linear combinations of specific transcripts to distinguish cancers from controls. Results: In the first stage, we identified 1661 probes that were significantly different in blood gene expression profiles between cases and controls (p&lt;0.05). In the second stage, real-time RT-PCR assays validated four genes among 33 cases and 75 controls: three up-regulated genes: A 1.4 fold, p&lt;0.001, B 1.2 fold, p=0.03, C 1.3 fold, p=0.08; and one down-regulated gene D 0.70, p=0.008. Linear combination of these 4 genes discriminated the cases from controls with a sensitivity of 90% and specificity of 53% (AUC: 0.80, 95% C.I.: 0.713∼0.871). The performance of PSA (4 ng/ml cut-off) in the same 108 sample set was 91% sensitivity and 13% specificity (AUC: 0.67, 95% CI: 0.75∼0.98). The performance of combining the four blood biomarkers with PSA yielded an AUC of 0.86 (95% C.I.: 0.77∼0.91) with a sensitivity 90% and specificity 70%. Conclusions: When used with PSA, these four blood-based biomarkers improved the overall accuracy to identify patients with prostate cancer at biopsy. These results would have important implications for new biomarkers discovery for prostate cancer detection. [Table: see text]

Kallikrein 4 (hK4) and prostate-specific antigen (PSA) are associated with the loss of E-cadherin and an epithelial-mesenchymal transition (EMT)-like effect in prostate cancer cells

Prostate-specific antigen (PSA) and the related kallikrein family of serine proteases are current or emerging biomarkers for prostate cancer detection and progression. Kallikrein 4 (KLK4/hK4) is of particular interest, as KLK4 mRNA has been shown to be elevated in prostate cancer. In this study, we now show that the comparative expression of hK4 protein in prostate cancer tissues, compared with benign glands, is greater than that of PSA and kallikrein 2 (KLK2/hK2), suggesting that hK4 may play an important functional role in prostate cancer progression in addition to its biomarker potential. To examine the roles that hK4, as well as PSA and hK2, play in processes associated with progression, these kallikreins were separately transfected into the PC-3 prostate cancer cell line, and the consequence of their stable transfection was investigated. PC-3 cells expressing hK4 had a decreased growth rate, but no changes in cell proliferation were observed in the cells expressing PSA or hK2. hK4 and PSA, but not hK2, induced a 2.4-fold and 1.7-fold respective increase, in cellular migration, but not invasion, through Matrigel, a synthetic extracellular matrix. We hypothesised that this increase in motility displayed by the hK4 and PSA-expressing PC-3 cells may be related to the observed change in structure in these cells from a typical rounded epithelial-like cell to a spindle-shaped, more mesenchymal-like cell, with compromised adhesion to the culture surface. Thus, the expression of E-cadherin and vimentin, both associated with an epithelial-mesenchymal transition (EMT), was investigated. E-cadherin protein was lost and mRNA levels were significantly decreased in PC-3 cells expressing hK4 and PSA (10-fold and 7-fold respectively), suggesting transcriptional repression of E-cadherin, while the expression of vimentin was increased in these cells. The loss of E-cadherin and associated increase in vimentin are indicative of EMT and provides compelling evidence that hK4, in particular, and PSA have a functional role in the progression of prostate cancer through their promotion of tumour cell migration.

Proteinchip(R) surface enhanced laser desorption/ionization (SELDI) mass spectrometry: a novel protein biochip technology for detection of prostate cancer biomarkers in complex protein mixtures.

Improving early detection, diagnosis, treatment monitoring and prognosis of cancer will require rapid and high throughput detection, identification, and measurement of multiple biomarkers. In this study, we demonstrate the versatility of the innovative SELDI ProteinChip(R) MS technology for the rapid, reproducible and simultaneous identification of four well-characterized prostate cancer-associated (PCA) biomarkers, prostate specific antigen (free and complexed forms), prostate specific peptide, prostate acid phophatase and prostate specific membrane antigen in cell lysates, serum and seminal plasma. Proteins corresponding to the mass of these biomarkers could readily be captured and detected using either chemically defined or antibody coated ProteinChip(R) arrays. Several (yet to be identified) proteins were found upregulated in cell lysates of pure populations of PCA cells procured by laser capture microdissection (LCM) when compared with mass spectra of normal cell lysates. Coupling LCM with SELDI provides tremendous opportunities to discover and identify the signature proteins associated with each stage of tumor development. Collectively, these observations demonstrate the potential of SELDI for the discovery and simultaneous detection of and clinical assay development for PCA biomarkers in complex biological mixtures.