Robert H. Getzenberg

Biomarkers for prostate cancer

The development of biomarkers for prostate cancer screening, detection, and prognostication has revolutionized the management of this disease. Prostate-specific antigen (PSA) is a useful, though not specific, biomarker for detecting prostate cancer. We review the literature on prostate cancer biomarkers, including serum markers (PAP, tPSA, fPSA, proPSA, PSAD, PSAV, PSADT, EPCA, and EPCA-2), tissue markers (AMACR, methylated GSTP1, and the TMPRSS2-ETS gene rearrangement), and a urine marker (DD3PCA3/UPM-3). Future research should focus on validation of already existing biomarkers and the discovery of new markers to identify men with aggressive prostate cancer.

DNA Methylation Alterations Exhibit Intraindividual Stability and Interindividual Heterogeneity in Prostate Cancer Metastases

Prostate tumors develop a unique epigenetic DNA methylation signature that is clonally maintained in disseminated metastases. Surveying the DNA Methylation “Cityscape” of Prostate Cancer Alterations in DNA methylation are a hallmark of human cancers, including prostate cancer. Understanding which of these alterations “drive” cancer initiation, progression, and metastasis, and which of these are merely “passengers” not involved in the chain of causation, is a major translational challenge. To tackle this challenge in the context of metastatic prostate cancer, Aryee et al. carried out genome-scale analyses of DNA methylation alterations in multiple metastases from each of 13 men who had died of metastatic prostate cancer. To visualize both the frequency of each methylation alteration in the metastases and the consistency with which each alteration was maintained across all metastases from an individual, the authors created DNA methylation “cityscape” plots. These analyses revealed that each individual developed a unique DNA methylation signature that was largely maintained across all metastases within that individual. Additionally, a set of DNA “hypermethylation” alterations, defined as regions that were normally unmethylated but acquired cancer-specific DNA methylation, were enriched for prostate cancer “drivers.” Such DNA hypermethylation alterations are attractive potential targets for development of longitudinal markers and therapeutic strategies for prostate cancer management. Human cancers almost ubiquitously harbor epigenetic alterations. Although such alterations in epigenetic marks, including DNA methylation, are potentially heritable, they can also be dynamically altered. Given this potential for plasticity, the degree to which epigenetic changes can be subject to selection and act as drivers of neoplasia has been questioned. We carried out genome-scale analyses of DNA methylation alterations in lethal metastatic prostate cancer and created DNA methylation “cityscape” plots to visualize these complex data. We show that somatic DNA methylation alterations, despite showing marked interindividual heterogeneity among men with lethal metastatic prostate cancer, were maintained across all metastases within the same individual. The overall extent of maintenance in DNA methylation changes was comparable to that of genetic copy number alterations. Regions that were frequently hypermethylated across individuals were markedly enriched for cancer- and development/differentiation-related genes. Additionally, regions exhibiting high consistency of hypermethylation across metastases within individuals, even if variably hypermethylated across individuals, showed enrichment for cancer-related genes. Whereas some regions showed intraindividual metastatic tumor heterogeneity in promoter methylation, such methylation alterations were generally not correlated with gene expression. This was despite a general tendency for promoter methylation patterns to be strongly correlated with gene expression, particularly at regions that were variably methylated across individuals. These findings suggest that DNA methylation alterations have the potential for producing selectable driver events in carcinogenesis and disease progression and highlight the possibility of targeting such epigenome alterations for development of longitudinal markers and therapeutic strategies.

Detection of Prostate Cancer with a Blood-Based Assay for Early Prostate Cancer Antigen

Prostate-specific antigen lacks specificity for prostate cancer, so the identification and characterization of a unique blood-based marker for the disease would provide for a more accurate diagnosis, reducing both unnecessary biopsies and patient uncertainty. We previously identified a novel biomarker for prostate cancer, early prostate cancer antigen (EPCA). EPCA antibodies positively stained the negative biopsies of men who, as much as 5 years later, were diagnosed with prostate cancer. The goal of this study was to determine whether EPCA antibodies could be used in a clinically applicable plasma-based immunoassay to specifically detect prostate cancer. Using an EPCA-based ELISA, the protein was measured in the plasma of 46 individuals, including prostate cancer patients, healthy individuals, other cancer patients, spinal cord injury victims, and patients with prostatitis. With a predetermined cutoff value of 1.7 absorbance at 450 nm, only the prostate cancer population, as a whole, expressed plasma-EPCA levels above the cutoff. Statistical analysis showed a significant difference in EPCA levels between the prostate cancer population and each of the other groups, specifically the healthy donors (P < 0.0001), bladder cancer patients (P = 0.03), and spinal cord injury patients (P = 0.001). Sensitivity of the EPCA assay for prostate cancer patients was 92% whereas the overall specificity was 94%. Specificity for the healthy donors was 100%. Although larger trials are required, this initial study shows the potential of EPCA to serve as a highly specific blood-based marker for prostate cancer. EPCA, when coupled with prostate-specific antigen, may help reduce the number of both unnecessary biopsies and undetected prostate tumors.

Altered Expression and Localization of Creatine Kinase B, Heterogeneous Nuclear Ribonucleoprotein F, and High Mobility Group Box 1 Protein in the Nuclear Matrix Associated with Colon Cancer

Identification of biomarkers could lead to the development of effective screening tests for colorectal cancer. A previous study from our laboratory showed specific alterations of nuclear structure in colon cancer. In an effort to characterize these biomarkers, protein spots were selected from separations made by two-dimensional gel electrophoresis, which were analyzed by mass spectrometry. The sequences obtained from the isolated spots revealed that they have close similarity to creatine kinase B (CKB) isoforms, heterogeneous nuclear ribonucleoprotein F (hnRNP F) and high mobility group box 1 protein (HMGB1) isoforms. To determine the expression of these proteins in colon cancer, expression was studied in 9 tumor and matched adjacent normal pairs, 5 donor colons, 16 polyps, 4 metastatic liver lesions and matched adjacent normal pairs, and 3 liver donors. CKB and hnRNP F were expressed in 78% and 89% of colon tumors, respectively. hnRNP F had a higher frequency of expression than CKB in premalignant polyps. With the establishment of differential expression of the proteins in colon cancer, their subcellular localization was analyzed. The subcellular fractions studied both showed high protein levels of hnRNP F in colon tumors compared with normal colon tissues. Surprisingly, subcellular levels of CKB were decreased in colon tumors, suggesting that the observed high CKB levels in nuclear matrix extracts are caused by the enhanced localization of CKB to the nuclear matrix during colon tumorigenesis. These results suggest an involvement of hnRNP F and CKB in colorectal cancer. Additionally, they suggest that hnRNP F is a potential marker for colorectal cancer progression.

A majority of the cancer/testis antigens are intrinsically disordered proteins

The cancer/testis antigens (CTAs) are a group of heterogeneous proteins that are typically expressed in the testis but aberrantly expressed in several types of cancer. Although overexpression of CTAs is frequently associated with advanced disease and poorer prognosis, the significance of this correlation is unclear since the functions of the CTAs in the disease process remain poorly understood. Here, employing a bioinformatics approach, we show that a majority of CTAs are intrinsically disordered proteins (IDPs). IDPs are proteins that, under physiological conditions in vitro, lack rigid 3D structures either along their entire length or in localized regions. Despite the lack of structure, most IDPs can transition from disorder to order upon binding to biological targets and often promote highly promiscuous interactions. IDPs play important roles in transcriptional regulation and signaling via regulatory protein networks and are often associated with dosage sensitivity. Consistent with these observations, we find that several CTAs can bind DNA, and their forced expression appears to increase cell growth implying a potential dosage‐sensitive function. Furthermore, the CTAs appear to occupy “hub” positions in protein regulatory networks that typically adopt a “scale‐free” power law distribution. Taken together, our data provide a novel perspective on the CTAs implicating them in processing and transducing information in altered physiological states in a dosage‐sensitive manner. Identifying the CTAs that occupy hub positions in protein regulatory networks would allow a better understanding of their functions as well as the development of novel therapeutics to treat cancer. J. Cell. Biochem. 112: 3256–3267, 2011.

Down‐regulating cold shock protein genes impairs cancer cell survival and enhances chemosensitivity

The microenvironment of the cancer cell is pivotal to its phenotypic regulation. One of the central components of the microenvironment is temperature. An elevation in environmental temperature has been shown to increase the cancer cells susceptibility to chemo‐ and radiation therapy. The goal of the studies described here was to identify some of the pathways that are modified by a mild increase in temperature in cancer cells. Using prostate cancer cells as a model system we found that in addition to the well described and anticipated up‐regulation of the heat shock family of proteins, there is a significant down‐regulation of certain members of the “cold shock” family of proteins such as, RNA binding motif protein 3 (RBM3) and cold inducible RNA binding protein (CIRBP). siRNA‐mediated down‐regulation of the cold shock protein (CSP) encoding mRNAs dramatically attenuates cell survival in the absence of any heat application. Furthermore, we also demonstrate that knocking down the CSPs can enhance the therapeutic response of prostate cancer cells to chemotherapy. Our findings suggest that down‐regulating CSPs in cancer cells may “mimic” the stress response the cells experience when exposed to heat treatment rendering them more susceptible to therapy. Thus, the pharmacological modulation of RBM3 and CIRBP may represent novel therapeutic approaches for prostate cancer. J. Cell. Biochem. 107: 179–188, 2009.

Nuclear structural proteins as biomarkers of cancer

The regulation of cell processes is integrally connected to cellular and extracellular structure. Studies over the past three decades have demonstrated the complex interactions of cell structure and function. The relationship of cellular structure and function has perhaps been most studied in the transformed cell. The hallmark of transformation is alterations in the shape of the cell and the nucleus. Many of the cellular alterations observed in the cancer process are structural, including changes in extracellular matrix‐cytoskeletal interactions, cytoskeletal elements, as well as nuclear structure. This review focuses on the structural components of the nucleus, the nuclear matrix, and their role in the cancer process and the use of these structural components of the nucleus, the nuclear matrix, and their role in the cancer process and the use of these structural components as cancer specific biomarkers. J. Cell. Biochem. Suppls. 32/33:183–191, 1999.

Initial Analyses of Colon Cancer–Specific Antigen (CCSA)-3 and CCSA-4 as Colorectal Cancer–Associated Serum Markers

Colon cancer-specific antigen (CCSA)-3 and CCSA-4 are novel colon cancer markers identified by focused proteomic analysis of nuclear structural proteins. The goal of these studies was to evaluate serum-based CCSA-3 and CCSA-4 in the detection of individuals with preneoplastic and neoplastic lesions using ELISAs. Serum samples from 107 subjects undergoing colonoscopy, 28 subjects with colorectal cancer, and 125 subjects with benign disease or other types of cancer were evaluated. Individuals who underwent colonoscopy were classified into mutually exclusive categories, including normal colon, hyperplastic polyp, nonadvanced adenoma, and advanced adenoma. Sensitivity and specificity for both CCSA-3 and CCSA-4 were evaluated using receiver operating characteristic (ROC) curves. At a cutoff of 2 microg/mL for CCSA-3 and 0.3 microg/mL for CCSA-4, each marker detected all 28 colorectal cancers, for a sensitivity of 100% (lower 95% confidence bound, 89.8%). The sensitivity for detection of the combined end point of colorectal cancer and advanced adenoma for CCSA-3 was 89.1% [95% confidence interval (95% CI), 76.4-96.4%] and for CCSA-4 was 84.8% (95% CI, 71.1-93.7%) and 91.3% (95% CI, 79.2-97.6%) for either marker positive. The specificity in individuals with normal, hyperplastic polyps, or nonadvanced adenomas was 82.0% (95% CI, 72.4-89.4%) and 91.0% (95% CI, 83.0-96.0%) for CCSA-3 and CCSA-4, respectively. ROC curves for CCSA-3 and CCSA-4 reveal an area under the curve of 0.94 (95% CI, 0.90-0.98%). In these initial analyses, CCSA-3 and CCSA-4 show promise as potential serum markers for detection of colorectal cancer and advanced adenomas.

Monocyte chemotactic protein-1 (MCP-1/CCL2) is associated with prostatic growth dysregulation and benign prostatic hyperplasia

Chronic inflammation is commonly observed in benign prostate hyperplasia (BPH), and prostate tissue often contains increased inflammatory infiltrates, including T cells and macrophages. Cytokines are not only key mediators of inflammation but may also play important roles in the initiation and progression of BPH.

Cancer/Testis antigens as potential predictors of biochemical recurrence of prostate cancer following radical prostatectomy

BackgroundThe Cancer/Testis Antigens (CTAs) are an important group of proteins that are typically restricted to the testis in the normal adult but are aberrantly expressed in several types of cancers. As a result of their restricted expression patterns, the CTAs could serve as unique biomarkers for cancer diagnosis/prognosis. The aim of this study was to identify promising CTAs that are associated with prostate cancer (PCa) recurrence following radical prostatectomy (RP).MethodsThe expression of 5 CTAs was measured by quantitative multiplex real-time PCR using prostate tissue samples obtained from 72 patients with apparently clinically localized PCa with a median of two years follow-up (range, 1 to 14 years).ResultsThe expression of CTAs namely, CEP55, NUF2, PBK and TTK were significantly higher while PAGE4 was significantly lower in patients with recurrent disease. All CTAs with the exception of TTK were significantly correlated with the prostatectomy Gleason score, but none were correlated with age, stage, or preoperative PSA levels. In univariate proportional hazards models, CEP55 (HR = 3.59, 95% CI: 1.50-8.60), p = 0.004; NUF2 (HR = 2.28, 95% CI: 1.11-4.67), p = 0.024; and PAGE4 (HR = 0.44, 95% CI: 0.21-0.93), p = 0.031 were significantly associated with the risk of PCa recurrence. However, the results were no longer significant after adjustment for prostatectomy Gleason score.ConclusionsTo our knowledge, this is the first study to identify CTAs as biomarkers that can differentiate patients with recurrent and non-recurrent disease following RP and underscores its potential impact on PCa prognosis and treatment.