Molecular markers of prostate cancer

Identification of SPP1 as an Extracellular Matrix Signature for Metastatic Castration-Resistant Prostate Cancer

Resistance to androgen deprivation therapy (ADT) is the main challenge for advanced fatal prostate cancer (PCa), which can gradually develop into metastatic castration-resistant prostate cancer (mCRPC). However, the pathologic mechanisms of mCRPC are still far from clear. Given the high incidence and mortality related to mCRPC, understanding the causes and pathogenesis of this condition as well as identifying potential biomarkers are of great importance. In the research reported here, we integrated several gene expression profiles from hormone sensitive prostate cancer (HSPC) and mCRPC datasets to identify differentially expressed genes (DEGs), key biological pathways, and cellular components. We found that extracellular matrix (ECM) genes were significantly enriched, and further filtered them using Pearson correlation analysis and stepwise regression to find ECM signatures to differentiate between the HSPC and mCRPC phenotypes. Six ECM signatures were input into K-nearest neighbor, logistic regression, naive Bayes, and random forest classifiers models. Random forest algorithm with the six-gene prognostic signatures showed best performance, which had high sensitivity and specificity for HSPC and mCRPC classification and further the six ECM signatures were validated in organoid models. Among the six ECM genes, SPP1 was identified as the key hub signature for PCa metastasis and drug resistance development; we found that both protein and mRNA expression levels of SPP1 were remarkably up-regulated in mCRPC compared with HSPC in organoid models and could regulate the androgen receptor signaling pathway. Therefore, SPP1 is a potential novel biomarker and therapeutic target for mCRPC. Further understanding of the role of SPP1 in mCRPC development may help to explore effectively therapeutic approaches for the prevention and intervention of drug resistance and metastasis.

Using a glucose meter to quantitatively detect disease biomarkers through a universal nanozyme integrated lateral fluidic sensing platform

Along with the advance in medical research, more biomarkers emerge as useful indicators for both disease and health index. However, majority of them have no practical or economic testing methods available yet, or rely on high-costing methods such as Enzyme-Linked Immuno-Sorbent Assay (ELISA), High-Performance Liquid Chromatography (HPLC), Mass Spectrum, and immunohistochemistry (IHC). In this article, we develop a universal nanozyme integrated testing platform for biological molecules that incorporates the electrochemical measurement of glucose with lateral flow immunostrip (LFS) for target analytes. This design involves the quantitative conversion of analytes into invertase and then glucose, which can be measured by an extremely affordable meter. The feasibility of this design was validated using 8-hydroxy-2'-deoxyguanosine (8-OHdG) and prostate specific antigen (PSA) as representatives for small molecules and moderate to large proteins respectively. Our approach yields results comparable to commercial diagnostic ELISA kits at a substantially reduced cost and reaction time. Specifically, the design has a detection limit of 0.23 ng mL^-1 for 8-OHdG and 1.26 ng mL^-1 for PSA, and a detection range of 0.1-100 ng mL^-1 for 8-OHdG and 1-100 ng mL^-1 for PSA. By combining the accessibility of well-established glucose testing and LFS, our design can serve as a point of care testing method that can be fully integrated into the personal lifestyle without requiring professional assistance.

Targeting PSMA with a Cu-64 Labeled Phosphoramidate Inhibitor for PET/CT Imaging of Variant PSMA-Expressing Xenografts in Mouse Models of Prostate Cancer

PURPOSE

Prostate-specific membrane antigen (PSMA) is highly up-regulated in prostate tumor cells, providing an ideal target for imaging applications of prostate cancer. CTT-1297 (IC50 = 27 nM) is an irreversible phosphoramidate inhibitor of PSMA that has been conjugated to the CB-TE1K1P chelator for incorporation of Cu-64. The resulting positron emission tomography (PET) agent, [(64)Cu]ABN-1, was evaluated for selective uptake both in vitro and in vivo in PSMA-positive cells of varying expression levels. The focus of this study was to assess the ability of [(64)Cu]ABN-1 to detect and distinguish varying levels of PSMA in a panel of prostate tumor-bearing mouse models.

PROCEDURES

CTT-1297 was conjugated to the CB-TE1K1P chelator using click chemistry and radiolabeled with Cu-64. Internalization and binding affinity of [(64)Cu]ABN-1 was evaluated in the following cell lines having varying levels of PSMA expression: LNCaP late-passage > LNCaP early passage ≈ C4-2B > CWR22rv1 and PSMA-negative PC-3 cells. PET/X-ray computed tomography imaging was performed in NCr nude mice with subcutaneous tumors of the variant PSMA-expressing cell lines.

RESULTS

[(64)Cu]ABN-1 demonstrated excellent uptake in PSMA-positive cells in vitro, with ∼80 % internalization at 4 h for each PSMA-positive cell line with uptake (fmol/mg) correlating to PSMA expression levels. The imaging data indicated significant tumor uptake in all models. The biodistribution for late-passage LNCaP (highest PSMA expression) demonstrated the highest specific uptake of [(64)Cu]ABN-1 with tumor-to-muscle and tumor-to-blood ratios of 30 ± 11 and 21 ± 7, respectively, at 24 h post-injection. [(64)Cu]ABN-1 cleared through all tissues except for PSMA-positive kidneys.

CONCLUSION

[(64)Cu]ABN-1 demonstrated selective uptake in PSMA-positive cells and tumors, which correlated to the level of PSMA expression. The data reported herein suggest that [(64)Cu]ABN-1 will selectively target and image variant PSMA expression and in the future will serve as a non-invasive method to follow the progression of prostate cancer in men.

miR-618 Inhibits Prostate Cancer Migration and Invasion by Targeting FOXP2

miRNAs play critical role in the development and progression of prostate cancer. Here we studied the role of miR-618 in prostate cancer migration and invasion. miR-618 was downregulated in metastatic androgen-independent prostate cancer (AIPC), patients with low miR-618 had poor outcome. Overexpression of miR-618 inhibited migration and invasion and induced mesenchymal to epithelial transition (MET). Conversely, knockdown of miR-618 promoted migration and invasion and induced epithelial to mesenchymal transition (EMT). FOXP2 was the direct target of miR-618, and promoted TGF-β expression, inhibition of TGF-β reversed the effect of miR-618 knockdown. We further analyzed the correlation between miR-618 expression and FOXP2 in human prostate cancer tissues, and found there was a negative correlation between miR-618 expression and FOXP2 levels. In conclusion, we found miR-618 inhibited prostate cancer migration and invasion by targeting FOXP2 and inhibiting TGF-β.

Proteomics and peptidomics: moving toward precision medicine in urological malignancies

Urological malignancies are a major cause of morbidity and mortality worldwide. Advances in early detection, diagnosis, prognosis and prediction of treatment response can significantly improve patient care. Proteomic and peptidomic profiling studies are at the center of kidney, prostate and bladder cancer biomarker discovery and have shown great promise for improved clinical assessment. Mass spectrometry (MS) is the most widely employed method for proteomic and peptidomic analyses. A number of MS platforms have been developed to facilitate accurate identification of clinically relevant markers in various complex biological samples including tissue, urine and blood. Furthermore, protein profiling studies have been instrumental in the successful introduction of several diagnostic multimarker tests into the clinic. In this review, we will provide a brief overview of high-throughput technologies for protein and peptide based biomarker discovery. We will also examine the current state of kidney, prostate and bladder cancer biomarker research as well as review the journey toward successful clinical implementation.

The use of matrix coating assisted by an electric field (MCAEF) to enhance mass spectrometric imaging of human prostate cancer biomarkers

In this work, we combined a newly developed matrix coating technique - matrix coating assisted by an electric field (MCAEF) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) to enhance the imaging of peptides and proteins in tissue specimens of human prostate cancer. MCAEF increased the signal-to-noise ratios of the detected proteins by a factor of 2 to 5, and 232 signals were detected within the m/z 3500-37500 mass range on a time-of-flight mass spectrometer and with the sinapinic acid MALDI matrix. Among these species, three proteins (S100-A9, S100-A10, and S100-A12) were only observed in the cancerous cell region and 14 proteins, including a fragment of mitogen-activated protein kinase/extracellular signal-regulated kinase kinase kinase 2, a fragment of cAMP-regulated phosphoprotein 19, 3 apolipoproteins (C-I, A-I, and A-II), 2 S100 proteins (A6 and A8), β-microseminoprotein, tumor protein D52, α-1-acid glycoprotein 1, heat shock protein β-1, prostate-specific antigen, and 2 unidentified large peptides at m/z 5002.2 and 6704.2, showed significantly differential distributions at the p < 0.05 (t-test) level between the cancerous and the noncancerous regions of the tissue. Among these 17 species, the distributions of apolipoprotein C-I, S100-A6, and S100-A8 were verified by immunohistological staining. In summary, this study resulted in the imaging of the largest group of proteins in prostate cancer tissues by MALDI-MS reported thus far, and is the first to show a correlation between S100 proteins and prostate cancer in a MS imaging study. The successful imaging of the three proteins only found in the cancerous tissues, as well as those showing differential expressions demonstrated the potential of MCAEF-MALDI/MS for the in situ detection of potential cancer biomarkers. Copyright © 2015 John Wiley & Sons, Ltd.

Prognostic role of microRNA-145 in prostate cancer: A systems review and meta-analysis

Background

Many studies have shown that microRNAs (miRNAs) exhibit altered expression in various cancers and may play an important role as prognostic biomarkers. The present meta-analysis was undertaken to summarize recent studies of the use of microRNA-145 (miR-145) in the assessment of prostate cancer and to analyze the prognostic role of miR-145 for disease-free survival (DFS) outcome.

Methods

The present meta-analysis was performed by searching PubMed with the use of multiple search strategies. Data were extracted from studies examining DFS in patients with prostate cancer who showed lower expression of miR-145. Pooled hazard ratios of miR-145 and 95% confidence intervals were calculated. Four studies with a total of 211 patients were included in this meta-analysis.

Results

For overall DFS, the pooled hazard ratio of lower miR-145 expression in prostate cancer was 0.74 (95% confidence interval: 0.23–2.34, P = 0.001). Thus, lower miR-145 expression was found to significantly predict poorer outcomes.

Conclusions

The present findings suggest that downregulation of the expression of miR-145 might predict poor prognosis in patients with prostate cancer.

DNA methylation status is more reliable than gene expression at detecting cancer in prostate biopsy

Background:

We analysed critically the potential usefulness of RNA- and DNA-based biomarkers in supporting conventional histological diagnostic tests for prostate carcinoma (PCa) detection.

Methods:

Microarray profiling of gene expression and DNA methylation was performed on 16 benign prostatic hyperplasia (BPH) and 32 cancerous and non-cancerous prostate samples extracted by radical prostatectomy. The predictive value of the selected biomarkers was validated by qPCR-based methods using tissue samples extracted from the 58 prostates and, separately, using 227 prostate core biopsies.

Results:

HOXC6, AMACR and PCA3 expression showed the best discrimination between PCa and BPH. All three genes were previously reported as the most promising mRNA-based markers for distinguishing cancerous lesions from benign prostate lesions; however, none were sufficiently sensitive and specific to meet the criteria for a PCa diagnostic biomarker. By contrast, DNA methylation levels of the APC, TACC2, RARB, DGKZ and HES5 promoter regions achieved high discriminating sensitivity and specificity, with area under the curve (AUCs) reaching 0.95−1.0. Only a small overlap was detected between the DNA methylation levels of PCa-positive and PCa-negative needle biopsies, with AUCs ranging between 0.854 and 0.899.

Conclusions:

DNA methylation-based biomarkers reflect the prostate malignancy and might be useful in supporting clinical decisions for suspected PCa following an initial negative prostate biopsy.

Novel tools for prostate cancer prognosis, diagnosis, and follow-up

Prostate-specific antigen (PSA) is the main diagnostic tool when it comes to prostate cancer but it possesses serious limitations. Therefore, there is an urgent need for more sensitive and specific biomarkers for prostate cancer prognosis and patient follow-up. Recent advances led to the discovery of many novel diagnostic/prognostic techniques and provided us with many worthwhile candidates. This paper briefly reviews the most promising biomarkers with respect to their implementation in screening, early detection, diagnostic confirmation, prognosis, and prediction of therapeutic response or monitoring disease and recurrence; and their use as possible therapeutic targets. This review also examines the possible future directions in the field of prostate cancer marker research.

Differentially expressed androgen-regulated genes in androgen-sensitive tissues reveal potential biomarkers of early prostate cancer

Background

Several data favor androgen receptor implication in prostate cancer initiation through the induction of several gene activation programs. The aim of the study is to identify potential biomarkers for early diagnosis of prostate cancer (PCa) among androgen-regulated genes (ARG) and to evaluate comparative expression of these genes in normal prostate and normal prostate-related androgen-sensitive tissues that do not (or rarely) give rise to cancer.

Methods

ARG were selected in non-neoplastic adult human prostatic epithelial RWPE-1 cells stably expressing an exogenous human androgen receptor, using RNA-microarrays and validation by qRT-PCR. Expression of 48 preselected genes was quantified in tissue samples (seminal vesicles, prostate transitional zones and prostate cancers, benign prostatic hypertrophy obtained from surgical specimens) using TaqMan® low-density arrays. The diagnostic performances of these potential biomarkers were compared to that of genes known to be associated with PCa (i.e. PCA3 and DLX1).

Results and Discussion

By crossing expression studies in 26 matched PCa and normal prostate transitional zone samples, and 35 matched seminal vesicle and PCa samples, 14 genes were identified. Similarly, 9 genes were overexpressed in 15 benign prostatic hypertrophy samples, as compared to PCa samples. Overall, we selected 8 genes of interest to evaluate their diagnostic performances in comparison with that of PCA3 and DLX1. Among them, 3 genes: CRYAB, KCNMA1 and SDPR, were overexpressed in all 3 reference non-cancerous tissues. The areas under ROC curves of these genes reached those of PCA3 (0.91) and DLX1 (0.94).

Conclusions

We identified ARG with reduced expression in PCa and with significant diagnostic values for discriminating between cancerous and non-cancerous prostatic tissues, similar that of PCA3. Given their expression pattern, they could be considered as potentially protective against prostate cancer. Moreover, they could be complementary to known genes overexpressed in PCa and included along with them in multiplex diagnostic tools.

Biomarkers for anti-angiogenic therapy in cancer

Angiogenesis, the development of new vessels from existing vasculature, plays a central role in tumor growth, survival, and progression. On the molecular level it is controlled by a number of pro- and anti-angiogenic cytokines, among which the vascular endothelial growth factors (VEGFs), together with their related VEGF-receptors, have an exceptional position. Therefore, the blockade of VEGF signaling in order to inhibit angiogenesis was deemed an attractive approach for cancer therapy and drugs interfering with the VEGF-ligands, the VEGF receptors, and the intracellular VEGF-mediated signal transduction were developed. Although promising in pre-clinical trials, VEGF-inhibition proved to be problematic in the clinical context. One major drawback was the generally high variability in patient response to anti-angiogenic drugs and the rapid development of therapy resistance, so that, in total, only moderate effects on progression-free and overall survival were observed. Biomarkers predicting the response to VEGF-inhibition might attenuate this problem and help to further individualize drug and dosage determination. Although up to now no definitive biomarker has been identified for this purpose, several candidates are currently under investigation. This review aims to give an overview of the recent developments in this field, focusing on the most prevalent tumor species.

PSMA-targeted SPECT agents: mode of binding effect on in vitro performance

BACKGROUND

The enzyme-biomarker prostate-specific membrane antigen (PSMA) is an active target for imaging and therapeutic applications for prostate cancer. The internalization of PSMA has been shown to vary with inhibitors' mode of binding: irreversible, slowly reversible, and reversible.

METHODS

In the present study, PSMA-targeted clickable derivatives of an irreversible phosphoramidate inhibitor DBCO-PEG(4) -CTT-54 (IC(50) = 1.0 nM) and a slowly reversible phosphate inhibitor, DBCO-PEG(4) -CTT-54.2 (IC(50) = 6.6 nM) were clicked to (99m) Tc(CO)(3) -DPA-azide to assemble a PSMA-targeted SPECT agent. The selectivity, percent uptake, and internalization of these PSMA-targeted SPECT agents were evaluated in PSMA-positive and PSMA-negative cells.

RESULTS

In vitro studies demonstrated that PSMA-targeted SPECT agents exhibited selective cellular uptake in the PSMA-positive LNCaP cells compared to PSMA-negative PC3 cells. More importantly, it was found that (99m) Tc(CO)(3) -DPA-DBCO-PEG(4) -CTT-54 based on an irreversible PSMA inhibitor core, exhibited greater uptake and internalization than (99m) Tc(CO)(3) -DPA-DBCO-PEG(4) -CTT-54.2 constructed from a slowly reversible PSMA inhibitor core.

CONCLUSIONS

We have demonstrated that a PSMA-targeted SPECT agent can be assembled efficiently using copper-less click chemistry. In addition, we demonstrated that mode of binding has an effect on internalization and percent uptake of PSMA-targeted SPECT agents; with the irreversible targeting agent demonstrating superior uptake and internalization in PSMA+ cells. The approach demonstrated in this work now supports a modular approach for the assembly of PSMA-targeted imaging and therapeutic agents.

CD24 is an effector of HIF-1-driven primary tumor growth and metastasis

Hypoxia drives malignant progression in part by promoting accumulation of the oncogenic transcription factor hypoxia inducible factor-1α (HIF-1α) in tumor cells. Tumor aggressiveness also relates to elevation of the cancer stem cell-associated membrane protein CD24, which has been causally implicated in tumor formation and metastasis in experimental models. Here, we link these two elements by showing that hypoxia induces CD24 expression through a functional hypoxia responsive element in the CD24 promoter. HIF-1α overexpression induced CD24 mRNA and protein under normoxic conditions, with this effect traced to a recruitment of endogenous HIF-1α to the CD24 promoter. Short hairpin RNA-mediated attenuation of HIF-1α or CD24 expression reduced cancer cell survival in vitro and in vivo at the levels of primary and metastatic tumor growth. CD24 overexpression in HIF-1α-depleted cancer cells rescued this decrease, whereas HIF-1α overexpression in CD24-depleted cells did not. Analysis of clinical tumor specimens revealed a correlation between HIF-1α and CD24 levels and an association of their coexpression to decreased patient survival. Our results establish a mechanistic linkage between 2 critically important molecules in cancer, identifying CD24 as a critical HIF-1α transcriptional target and biologic effector, strengthening the rationale to target CD24 for cancer therapy.

A phosphoramidate-based prostate-specific membrane antigen-targeted SPECT agent

BACKGROUND

Prostate-specific membrane antigen (PSMA) remains an active target for imaging and therapeutic applications for prostate cancer.

METHODS

In the present study, an irreversible phosphoramidate inhibitor, CTT-54 (IC50 = 14 nM), has been modified to deliver 99mTc-(CO)3-DTPA as a SPECT imaging payload to PSMA+ cells in vivo and in vitro. Percent uptake, competitive binding, and internalization will evaluate the imaging agent in vitro. Preliminary biodistribution and imaging will be utilized for in vivo evaluation.

RESULTS

In vitro studies demonstrate that the radiotracer 99mTc-(CO)3-DTPA-CTT-54 exhibits increasing cellular uptake in the PSMA+ LNCaP cells over time. More importantly, it was found that 99mTc-(CO)3-DTPA-CTT-54 is rapidly internalized into LNCaP cells, presumably through the PSMA enzyme-inhibitor complex. In a pilot biodistribution study, increasing accumulation of the radiotracer in LNCaP xenografts was observed from 2 to 4 hr and significant clearance from non-target tissues.

CONCLUSIONS

While DTPA may not represent the ideal chelate structure for 99mTc(CO)3, the data provides proof-of-concept support for the development of a next-generation phosphoramidate-based PSMA inhibitor-conjugates for use as SPECT imaging agents.

A new frontier in personalized cancer therapy: mapping molecular changes

Mutations in the genome of a normal cell can affect the function of its many genes and pathways. These alterations could eventually transform the cell from a normal to a malignant state by allowing an uncontrolled proliferation of the cell and formation of a cancer tumor. Each tumor in an individual patient can have hundreds of mutated genes and perturbed pathways. Cancers clinically presenting as the same type or subtype could potentially be very different at the molecular level and thus behave differently in response to therapy. The challenge is to distinguish the key mutations driving the cancer from the background of mutational noise and find ways to effectively target them. The promise is that such a molecular approach to classifying cancer will lead to better diagnostic, prognostic and personalized treatment strategies. This article provides an overview of advances in the molecular characterization of cancers and their applications in therapy.

Systematic review of performance of non-invasive biomarkers in the evaluation of non-alcoholic fatty liver disease

This systematic review evaluates the many studies carried out to discover and evaluate non-invasive markers of non-alcoholic fatty liver disease (NAFLD). Many different strategies and methods have been used in this task, from the discovery of new markers by global 'shotgun' studies to hypothesis-driven approaches, to the development of algorithm tests based on routinely available clinical and biochemical parameters. We examined the various different approaches, summarising the findings in an attempt to give an overview of the field of non-invasive markers in NAFLD, encompassing markers of steatosis, necro-inflammation and fibrosis. The body of literature surrounding this topic is complex and varied, encompassing not only different methodologies but also different patient characteristics, different disease definitions, as well as different end points. This reflects the heterogeneity of NAFLD, which, however, introduces considerably difficulty when trying to draw a conclusion between studies. We have divided this review into three main chapters based on the characteristics of the studies. The Genomics/Proteomics chapter reviews studies using a non-hypothesis-driven approach to biomarker discovery. Thereafter, we evaluate studies of association - studies that target-specific markers, comparing levels between disease and control groups. Finally, we examine the algorithm tests - mathematical systems developed on the basis of previously described markers and assessed, usually, by receiver operator curve analysis. While radiological examination and investigations offer important diagnostic information, such studies are not discussed in this review - the body of literature surrounding blood and anthropological markers is complex and varied, demanding close attention.

Protein expression profiles distinguish between experimental invasive pulmonary aspergillosis and Pseudomonas pneumonia

We hypothesized that invasive pulmonary aspergillosis (IPA) may generate a distinctive proteomic signature in plasma and bronchoalveolar lavage (BAL). Proteins in plasma and BAL from two neutropenic rabbit models of IPA and Pseudomonas pneumonia were analyzed by SELDI-TOF MS. Hierarchical clustering analysis of plasma time course spectra demonstrated two clusters of peaks that were differentially regulated between IPA and Pseudomonas pneumonia (57 and 34 peaks, respectively, p<0.001). PCA of plasma proteins demonstrated a time-dependent separation of the two infections. A random forest analysis that ranked the top 30 spectral points distinguished between late Aspergillus and Pseudomonas pneumonias with 100% sensitivity and specificity. Based on spectral data analysis, three proteins were identified using SDS-PAGE and LC/MS and quantified using reverse phase arrays. Differences in the temporal sequence of plasma haptoglobin (p<0.001), apolipoprotein A1 (p<0.001) and transthyretin (p<0.038) were observed between IPA and Pseudomonas pneumonia, as was C-reactive protein (p<0.001). In summary, proteomic analysis of plasma and BAL proteins of experimental Aspergillus and Pseudomonas pneumonias demonstrates unique protein profiles with principal components and spectral regions that are shared in early infection and diverge at later stages of infection. Haptoglobin, apolipoprotein A1, transthyretin, and C-reactive protein are differentially expressed in these infections suggesting important contributions to host defense against IPA.

Mouse models of prostate cancer

The development and optimization of high-throughput screening methods has identified a multitude of genetic changes associated with human disease. The use of immunodeficient and genetically engineered mouse models that mimic the human disease has been crucial in validating the importance of these genetic pathways in prostate cancer. These models provide a platform for finding novel therapies to treat human patients afflicted with prostate cancer as well as those who have debilitating bone metastases. In this paper, we focus on the historical development and phenotypic descriptions of mouse models used to study prostate cancer. We also comment on how closely each model recapitulates human prostate cancer.

Flow cytometric detection of prostate tumor cells using chemoaffinity labels

BACKGROUND

The enzyme-biomarker prostate-specific membrane antigen (PSMA) is an emerging target for imaging and therapeutic applications for prostate cancer. However, the use of PSMA for detecting circulating prostate tumor cells remains under-explored. The present study focuses on the specific labeling of PSMA+ prostate cancer cells with a fluorescent PSMA inhibitor and the quantitation of PSMA+ cells in blood by flow cytometry (FC) using a gating strategy to separate labeled PSMA+ cells from peripheral blood mononuclear cells.

METHODS

Suspensions of PSMA+ (LNCaP) and PSMA- (DU145) cells were incubated with the fluorescent PSMA inhibitor FAMX-CTT-54. Incubation parameters (time, temperature, and label concentration) were varied to optimize cell labeling. A gating protocol based on double fluorescent labeling of CD45 and PSMA was developed for the quantitiation of LNCaP cells in the presence of white blood cells from bovine blood. Nonfluorescent beads were added to the labeled cell mixture and served as internal standard for precise cellular quantification of LNCaP cells by flow cytometry.

RESULTS

The fluorescent PSMA inhibitor FAMX-CTT-54 was specific for PSMA+ cells. The minimum time and concentration of FAMX-CTT-54 for effective labeling of PSMA+ cell suspensions at 37°C was 7.5 min and 35 nM, respectively; no labeling was observed on PSMA- cells. Co-incubation or pre-incubation of PSMA+ cells with the unlabeled PSMA inhibitor CTT-54 resulted in a concentration-dependent reduction in fluorescent labeling with FAMX-CTT-54 thereby confirming that the labeling was specific for PSMA. In blood samples in which LNCaP cells were added, an average of five cells were detected in a 115 µl sample of the most dilute sample examined (29 cells/ml); three cells were expected theoretically. The greater loss of labeling of PSMA+ cells with FAMX-CTT-54 when pre-incubated with CTT-54 is consistent with the irreversible mode of binding of CTT-54 to PSMA and subsequent internalization of the PSMA-inhibitor complex.

CONCLUSIONS

The results suggest that fluorescent PSMA inhibitors can be utilized to effectively detect and quantify PSMA+ cells by FC. These results support the use of such compounds in the application of FC to detect, quantify, and characterize circulating prostate tumor cells.

Targeting RSK2 in human malignancies

IMPORTANCE OF THE FIELD

p90 ribosomal S6 kinase 2 (RSK2) belongs to a Ser/Thr kinase family containing four members, RSK1 - 4, which play an essential role in a number of cellular functions including cell cycle, survival and proliferation. Recent advances reveal a crucial role of RSK2 in oncogenesis and tumor progression, making RSK2 an attractive therapeutic target for cancer treatment.

AREA COVERED IN THIS REVIEW

Recent findings identifying the role of RSK2 in human cancers, including hematopoietic malignancies and solid tumors. Therapeutic implications of targeting RSK2 are also discussed with regard to clinical circumstance.

WHAT THE READER WILL GAIN

A better understanding of molecular mechanisms underlying RSK2 activation and its contribution to human cancers and also insight into the development of novel targeted cancer therapy.

TAKE HOME MESSAGE

The significance of RSK2 in cancer cell survival, proliferation, invasion and tumor metastasis varies amongst human malignancies and depends on the signaling properties of the oncogenes and cellular microenvironment of the transformed cells. Thus, further exploitation of RSK2 signaling and its dynamic interaction with other crucial oncogenic and pro-metastatic pathways in different human malignancies is needed for more effective therapeutic interventions.

Profiling protein markers associated with lymph node metastasis in prostate cancer by DIGE-based proteomics analysis

Current predictive tools and imaging modalities are not accurate enough for preoperative diagnosis of lymph node metastatic prostate cancer (LNM PCa). Proteomic analysis is introduced to screen potential biomarkers for early detection of LNM PCa. In our initial study, protein samples from localized and LNM PCa as well as benign prostatic hyperplasia tissues were analyzed using two-dimensional fluorescence difference in gel electrophoresis (2-D DIGE) coupled with MALDI-TOF/TOF MS. We identified 58 proteins that were differentially expressed in the LNM PCa group relative to the localized PCa group. Six of these proteins, e-FABP5, MCCC2, PPA2, Ezrin, SLP2, and SM22, are functionally relevant to cancer metastasis. Expression of these proteins was therefore further validated in tissue samples from the original cohort and also from a larger, independent cohort of patients using real time PCR, Western blotting, and immunohistochemistry staining. In addition, the serum levels of e-FABP5 were also examined by ELISA. Relative to localized PCa tissues, LNM PCa tissues had increased expression of e-FABP5, MCCC2, PPA2, Ezrin, and SLP2 and decreased expression of SM22. Patients with LNM PCa had significantly higher levels of serum e-FABP5. This study presents evidence that increased expression of e-FABP5, MCCC2, PPA2, Ezrin, and SLP2 and decreased expression of SM22 are useful diagnostic markers for the existence of LNM PCa.

Discovery of prostate cancer biomarkers by microarray gene expression profiling

Prostate cancer is the most commonly diagnosed malignancy in males in the Western world. This review focuses on advances in biomarker discovery for prostate cancer by microarray profiling of mRNA and microRNA expression. Novel biomarkers are strongly needed to enable more accurate detection of prostate cancer, improve prediction of tumor aggressiveness and facilitate discovery of new therapeutic targets for tailored medicine. Promising molecular markers identified from gene expression profiling studies include AMACR, EZH2, TMPRSS2-ERG, miR-221 and miR-141, which are described in more detail. In addition, a compilation of prognostic gene expression signatures for prediction of prostate cancer patient outcome is provided, and their possible clinical utility is discussed. Furthermore, limitations in the application of microarray-based expression profiling for identification of prostate cancer biomarkers are addressed.

Expression analysis and study of the KLK15 mRNA splice variants in prostate cancer and benign prostatic hyperplasia

Prostate cancer is the most commonly diagnosed malignancy in male populations in the Western world. The KLK15 gene, the newest member of the kallikrein family, is expressed in the prostate gland. The purpose of this study is the expression analysis and the clinical evaluation of the KLK15 mRNA spliced variants in prostate cancer (CaP) and benign prostatic hyperplasia (BPH) patients. Total RNA was isolated from 104 CaP and BPH tissue specimens. After testing the quality of the RNA, cDNA was produced by reverse transcription, and PCR was performed for the amplification of the KLK15 mRNA transcripts. GAPDH and HPRT genes were used as endogenous controls Our data revealed that mRNA spliced variants of KLK15 were differentially expressed in prostate tissue specimens. Analysis of data showed a statistically significant (P < 0.001) increase in the frequency of overexpression of KLK15 transcripts encoding for both the active isoform and for the isoform 3 in CaP compared to BPH samples. Furthermore, KLK15 transcripts were found to be highly expressed in more aggressive tumors (P = 0.017). These results suggest that KLK15 expression analysis could be employed as a valuable tool for the discrimination between BPH and CaP tissue specimens and as an unfavorable prognostic marker for prostate cancer.

Differential protein expressions in renal cell carcinoma: new biomarker discovery by mass spectrometry

Renal cell carcinoma (RCC) is the most common neoplasm in the adult kidney. Unfortunately, there are currently no biomarkers for the diagnosis of RCC. In addition to early detection, biomarkers have a potential use for prognosis, for monitoring recurrence after treatment, and as predictive markers for treatment efficiency. In this study, we identified proteins that are dysregulated in RCC, utilizing a quantitative mass spectrometry analysis. We compared the protein expression of kidney cancer tissues to their normal counterparts from the same patient using LC-MS/MS. iTRAQ labeling permitted simultaneous quantitative analysis of four samples (cancer, normal, and two controls) by separately tagging the peptides in these samples with four cleavable mass-tags (114, 115, 116, and 117 Da). The samples were then pooled, and the tagged peptides resolved first by strong cation exchange chromatography and then by nanobore reverse phase chromatography coupled online to nanoelectrospray MS/MS. We identified a total of 937 proteins in two runs. There was a statistically significant positive correlation of the proteins identified in both runs (r(p) = 0.695, p < 0.001). Using a cutoff value of 0.67 fold for underexpression and 1.5 fold for overexpression, we identified 168 underexpressed proteins and 156 proteins that were overexpressed in RCC compared to normal tissues. These dysregulated proteins in RCC were statistically significantly different from those of transitional cell carcinoma and end-stage glomerulonephritis. We performed an in silico validation of our results using different tools and databases including Serial Analysis of Gene Expression (SAGE), UniGene EST ProfileViewer, Cancer Genome Anatomy Project, and Gene Ontology consortium analysis.

Molecular biomarkers in prostate cancer

BACKGROUND

After more than two decades of clinical use, serum prostate-specific antigen (PSA) has increased the early diagnosis of prostate cancer, detecting the disease even when small volumes are present. Although stage migration of prostate cancer has occurred, PSA has well-known limitations, despite attempts at refinement and modification, such as the use of PSA velocity, which have been used to improve it. New biomarkers for prostate cancer have been discovered, with promising early results.

OBJECTIVE/METHODS

This article reviews the ubiquitous current literature on biomarkers in prostate cancer. A search using MEDLINE and EMBASE databases was performed and those articles reporting biomarkers in prostate cancer with clinically significant findings in terms of detection were analyzed. Immunohistochemical markers were not considered for this review.

RESULTS/CONCLUSION

Despite many markers being promising, no single marker has satisfied the criteria as a perfect candidate. Limited clinical use of IL-6, TGF-β1 and PCA3 has commenced, and further widespread availability of these tests is expected in the coming years. The future lies in artificial neural networks and panels of markers instead of individual assays. Although PSA has some well-known limitations, it is at present the best marker available for prostate cancer when used in conjunction with nomograms or risk calculators.

Activation of the osteopontin/matrix metalloproteinase-9 pathway correlates with prostate cancer progression

PURPOSE

Prostate cancer remains the second most frequent cause of tumor-related deaths in the Western world. Additional markers for the identification of prostate cancer development and progression are needed. Osteopontin (OPN), which activates matrix metalloproteinases (MMP), is considered a prognostic biomarker in several cancers. "In silico" and experimental approaches were used to determine whether OPN-mediated MMP activation may be a signal of prostate cancer progression.

EXPERIMENTAL DESIGN

Pearson correlation coefficients were computed for each OPN/MMP pair across seven publicly available prostate cancer gene expression data sets. Using Gene Set Enrichment Analysis, 101 cancer-related gene sets were analyzed for association with OPN and MMP-9 expression. OPN, MMP-9, MMP-2 tissue inhibitor of metalloproteinase-1 plasma levels, and MMP gelatinase activity were measured by ELISA and zymography in 96 and 92 patients with prostate cancer and benign prostatic hyperplasia, respectively, and 125 age-matched healthy men.

RESULTS

Computational analyses identified a significant correlation only between MMP-9 and OPN, and showed significant enrichment scores in "cell proliferation", "genes constituting the phosphoinositide-3-kinase predictor", "proliferation signature", and "tumor metastasis" gene sets in association with both OPN and MMP-9. Plasma analyses revealed a significant increase in OPN and MMP-9 levels and activity in patients with prostate cancer in association with clinical variables (prostate-specific antigen > 4 ng/mL and Gleason score > 7). Significant correlation between OPN and MMP-9 levels were also observed. Mean plasma levels of OPN and MMP-9 decreased in patients with prostate cancer within 6 months after prostatectomy.

CONCLUSIONS

The concordant computational and experimental data indicate that the extent of OPN pathway activation correlates with prostate cancer progression.

The role of metallothionein in oncogenesis and cancer prognosis

The antiapoptotic, antioxidant, proliferative, and angiogenic effects of metallothionein (MT)-I+II has resulted in increased focus on their role in oncogenesis, tumor progression, therapy response, and patient prognosis. Studies have reported increased expression of MT-I+II mRNA and protein in various human cancers; such as breast, kidney, lung, nasopharynx, ovary, prostate, salivary gland, testes, urinary bladder, cervical, endometrial, skin carcinoma, melanoma, acute lymphoblastic leukemia (ALL), and pancreatic cancers, where MT-I+II expression is sometimes correlated to higher tumor grade/stage, chemotherapy/radiation resistance, and poor prognosis. However, MT-I+II are downregulated in other types of tumors (e.g. hepatocellular, gastric, colorectal, central nervous system (CNS), and thyroid cancers) where MT-I+II is either inversely correlated or unrelated to mortality. Large discrepancies exist between different tumor types, and no distinct and reliable association exists between MT-I+II expression in tumor tissues and prognosis and therapy resistance. Furthermore, a parallel has been drawn between MT-I+II expression as a potential marker for prognosis, and MT-I+II's role as oncogenic factors, without any direct evidence supporting such a parallel. This review aims at discussing the role of MT-I+II both as a prognostic marker for survival and therapy response, as well as for the hypothesized role of MT-I+II as causal oncogenes.

Identification and characterization of small-molecule inhibitors of hepsin

Hepsin is a type II transmembrane serine protease overexpressed in the majority of human prostate cancers. We recently demonstrated that hepsin promotes prostate cancer progression and metastasis and thus represents a potential therapeutic target. Here we report the identification of novel small-molecule inhibitors of hepsin catalytic activity. We utilized purified human hepsin for high-throughput screening of established drug and chemical diversity libraries and identified sixteen inhibitory compounds with IC(50) values against hepsin ranging from 0.23-2.31 microM and relative selectivity of up to 86-fold or greater. Two compounds are orally administered drugs established for human use. Four compounds attenuated hepsin-dependent pericellular serine protease activity in a dose dependent manner with limited or no cytotoxicity to a range of cell types. These compounds may be used as leads to develop even more potent and specific inhibitors of hepsin to prevent prostate cancer progression and metastasis.

MicroRNA profile analysis of human prostate cancers

We examined the microRNA (miRNA) expression profile of 40 prostatectomy specimens from stage T2a/b, early relapse and non-relapse cancer patients, to better understand the relationship between miRNA dysregulation and prostate oncogenesis. Paired analysis was carried out with microdissected, malignant and non-involved areas of each specimen, using high-throughput liquid-phase hybridization (mirMASA) reactions and 114 miRNA probes. Five miRNAs (miR-23b, -100, -145, -221 and -222) were significantly downregulated in malignant tissues, according to significance analysis of microarrays and paired t-test with Bonferroni correction. Lowered expression of miR-23b, -145, -221 and -222 in malignant tissues was validated by quantitative reverse transcription (qRT)-PCR analyses. Ectopic expression of these miRNAs significantly reduced LNCaP cancer cell growth, suggesting growth modulatory roles for these miRNAs. Patient subset analysis showed that those with post-surgery elevation of prostate-specific antigen (chemical relapse) displayed a distinct expression profile of 16 miRNAs, as compared with patients with non-relapse disease. A trend of increased expression (>40%) of miR-135b and miR-194 was observed by qRT-PCR confirmatory analysis of 11 patients from each clinical subset. These findings indicate that an altered miRNA expression signature accompanied the prostate oncogenic process. Additional, aberrant miRNA expression features may reflect a tendency for early disease relapse. Growth inhibition through the reconstitution of miRNAs is potentially applicable for experimental therapy of prostate cancer, pending molecular validation of targeted genes.

Expression and secretion of N-acylethanolamine-hydrolysing acid amidase in human prostate cancer cells

N-acylethanolamines (NAEs) are a class of bioactive lipid molecules in animal tissues, including the endocannabinoid anandamide and the anti-inflammatory substance N-palmitoylethanolamine. Enzymatic hydrolysis of NAEs is considered to be an important step to regulate their endogenous levels. Lysosomal NAE-hydrolysing acid amidase (NAAA) as well as fatty acid amide hydrolase (FAAH) is responsible for this reaction. Here, we report relatively high expression of NAAA in human prostate cancer cells (PC-3, DU-145 and LNCaP) and prostate epithelial cells (PrEC), with the highest mRNA level in LNCaP cells. FAAH and the NAE-forming enzyme N-acylphosphatidylethanolamine-hydrolysing phospholipase D (NAPE-PLD) were also detected in these cells. NAAA activity in LNCaP cells could be distinguished from coexisting FAAH activity, based on their different pH dependency profiles and specific inhibition of FAAH activity by URB597. These results showed that both the enzymes were functionally active. We also found that NAAA was partly secreted from LNCaP cells, which underlined possible usefulness of this enzyme as a biomarker of prostate cancer.

A sensitive array-based assay for identifying multiple TMPRSS2:ERG fusion gene variants

Studies of gene fusions in solid tumors are not as extensive as in hematological malignancies due to several technical and analytical problems associated with tumor heterogeneity. Nevertheless, there is a growing interest in the role of fusion genes in common epithelial tumors after the discovery of recurrent TMPRSS2:ETS fusions in prostate cancer. Among all of the reported fusion partners in the ETS gene family, TMPRSS2:ERG is the most prevalent one. Here, we present a simple and sensitive microarray-based assay that is able to simultaneously determine multiple fusion variants with a single RT-PCR in impure RNA specimens. The assay detected TMPRSS2:ERG fusion transcripts with a detection sensitivity of <10 cells in the presence of more than 3000 times excess normal RNA, and in primary prostate tumors having no >1% of cancer cells. The ability to detect multiple transcript variants in a single assay is critically dependent on both the primer and probe designs. The assay should facilitate clinical and basic studies for fusion gene screening in clinical specimens, as it can be readily adapted to include multiple gene loci.

Computational prediction of human proteins that can be secreted into the bloodstream

We present a novel computational method for predicting which proteins from highly and abnormally expressed genes in diseased human tissues, such as cancers, can be secreted into the bloodstream, suggesting possible marker proteins for follow-up serum proteomic studies. A main challenging issue in tackling this problem is that our understanding about the downstream localization after proteins are secreted outside the cells is very limited and not sufficient to provide useful hints about secretion to the bloodstream. To bypass this difficulty, we have taken a data mining approach by first collecting, through extensive literature searches, human proteins that are known to be secreted into the bloodstream due to various pathological conditions as detected by previous proteomic studies, and then asking the question: 'what do these secreted proteins have in common in terms of their physical and chemical properties, amino acid sequence and structural features that can be used to predict them?' We have identified a list of features, such as signal peptides, transmembrane domains, glycosylation sites, disordered regions, secondary structural content, hydrophobicity and polarity measures that show relevance to protein secretion. Using these features, we have trained a support vector machine-based classifier to predict protein secretion to the bloodstream. On a large test set containing 98 secretory proteins and 6601 non-secretory proteins of human, our classifier achieved approximately 90% prediction sensitivity and approximately 98% prediction specificity. Several additional datasets are used to further assess the performance of our classifier. On a set of 122 proteins that were found to be of abnormally high abundance in human blood due to various cancers, our program predicted 62 as blood-secreted proteins. By applying our program to abnormally highly expressed genes in gastric cancer and lung cancer tissues detected through microarray gene expression studies, we predicted 13 and 31 as blood secreted, respectively, suggesting that they could serve as potential biomarkers for these two cancers, respectively. Our study demonstrated that our method can provide highly useful information to link genomic and proteomic studies for disease biomarker discovery. Our software can be accessed at http://csbl1.bmb.uga.edu/cgi-bin/Secretion/secretion.cgi.

Translating insights from the cancer genome into clinical practice

Cancer cells have diverse biological capabilities that are conferred by numerous genetic aberrations and epigenetic modifications. Today's powerful technologies are enabling these changes to the genome to be catalogued in detail. Tomorrow is likely to bring a complete atlas of the reversible and irreversible alterations that occur in individual cancers. The challenge now is to work out which molecular abnormalities contribute to cancer and which are simply 'noise' at the genomic and epigenomic levels. Distinguishing between these will aid in understanding how the aberrations in a cancer cell collaborate to drive pathophysiology. Past successes in converting information from genomic discoveries into clinical tools provide valuable lessons to guide the translation of emerging insights from the genome into clinical end points that can affect the practice of cancer medicine.

The pathogenesis of prostate cancer: from molecular to metabolic alterations

Prostate cancer (PCa) is a heterogeneous disease with regard to molecular alterations and clinical course. The investigation of genetic alterations associated with PCa pathogenesis is highly challenging. Genome-wide analyses and epidemiological studies have identified only a handful of candidate genes possibly associated with hereditary or sporadic PCa. Cancer cells often rely for survival on common biochemical pathways such as enhanced anaerobic glycolysis and lipogenesis. The lipogenic enzyme fatty acid synthase seems to play a crucial part in PCa by conferring growth and survival advantages to cancer cells. We summarize the current understanding of the molecular events in PCa, and highlight the importance of altered lipid metabolism in the development and progression of prostate malignancy.

PCA3 molecular urine assay correlates with prostate cancer tumor volume: implication in selecting candidates for active surveillance

PURPOSE

Prostate cancer gene 3 (PCA3) has shown promise as a molecular marker in prostate cancer detection. We assessed the association of urinary PCA3 score with prostatectomy tumor volume and other clinical and pathological features.

MATERIALS AND METHODS

Urine specimens were collected after digital rectal examination from 59 men scheduled for prostate biopsy and 83 men scheduled for radical prostatectomy. Prostatectomy findings were evaluable for 96 men. PCA3 and prostate specific antigen mRNAs were quantified with Gen-Probe DTS 400 System. The PCA3 score was defined as the ratio of PCA3 mRNA/prostate specific antigen mRNA x10(3).

RESULTS

The PCA3 score in men with negative biopsies (30) and positive biopsies (29) were significantly different (median 21.1 and 31.0, respectively, p = 0.029). The PCA3 score was significantly correlated with total tumor volume in prostatectomy specimens (r = 0.269, p = 0.008), and was also associated with prostatectomy Gleason score (6 vs 7 or greater, p = 0.005) but not with other clinical and pathological features. The PCA3 score was significantly different when comparing low volume/low grade cancer (dominant tumor volume less than 0.5 cc, Gleason score 6) and significant cancer (p = 0.007). On multivariate analysis PCA3 was the best predictor of total tumor volume in prostatectomy (p = 0.001). Receiver operating characteristic curve analysis showed that the PCA3 score could discriminate low volume cancer (total tumor volume less than 0.5 cc) well with area under the curve of 0.757.

CONCLUSIONS

The PCA3 score appears to stratify men based on prostatectomy tumor volume and Gleason score, and may have clinical applicability in selecting men who have low volume/low grade cancer.

A nanoparticle label/immunochromatographic electrochemical biosensor for rapid and sensitive detection of prostate-specific antigen

We present a nanoparticle (NP) label/immunochromatographic electrochemical biosensor (IEB) for rapid and sensitive detection of prostate-specific antigen (PSA) in human serum. This IEB integrates the immunochromatographic strip with the electrochemical detector for transducing quantitative signals. The NP label, made of CdSe@ZnS, serves as a signal-amplifier vehicle. A sandwich immunoreaction was performed on the immunochromatographic strip. The captured NP labels in the test zone were determined by highly sensitive stripping voltammetric measurement of the dissolved metallic component (cadmium) with a disposable-screen-printed electrode, which is embedded underneath the membrane of the test zone. Several experimental parameters (e.g., immunoreaction time, the amount of anti-PSA-NP conjugations applied) and electrochemical detection conditions (e.g., preconcentration potential and time) were optimized using this biosensor for PSA detection. The analytical performance of this biosensor was evaluated with serum PSA samples according to the "figure-of-merits" (e.g., dynamic range, reproducibility, and detection limit). The results were validated with enzyme-linked immunosorbent assay (ELISA) and showed high consistency. It is found that this biosensor is very sensitive with the detection limit of 0.02ngmL(-1) PSA and is quite reproducible (with a relative standard deviation (R.S.D.) of 6.4%). This method is rapid, clinically practical, and less expensive than other diagnostic tools for PSA; therefore, this IEB coupled with a portable electrochemical analyzer shows great promise for simple, sensitive, quantitative point-of-care testing of disease-related protein biomarkers.

Inducible FGFR-1 activation leads to irreversible prostate adenocarcinoma and an epithelial-to-mesenchymal transition

Fibroblast Growth Factor Receptor-1 (FGFR1) is commonly overexpressed in advanced prostate cancer (PCa). To investigate causality, we utilized an inducible FGFR1 (iFGFR1) prostate mouse model. Activation of iFGFR1 with chemical inducers of dimerization (CID) led to highly synchronous, step-wise progression to adenocarcinoma that is linked to an epithelial-to-mesenchymal transition (EMT). iFGFR1 inactivation by CID withdrawal led to full reversion of prostatic intraepithelial neoplasia, whereas PCa lesions became iFGFR1-independent. Gene expression profiling at distinct stages of tumor progression revealed an increase in EMT-associated Sox9 and changes in the Wnt signaling pathway, including Fzd4, which was validated in human PCa. The iFGFR1 model clearly implicates FGFR1 in PCa progression and demonstrates how CID-inducible models can help evaluate candidate molecules in tumor progression and maintenance.

The ongoing evolution of proteomics in malignancy

The complementary fields of genomics and proteomics offer insights into the molecular mechanisms of diseases. While genomics seeks to define our genetic substrate, proteomics explores the structure and function of proteins, which are the end effectors of our genes. Proteomics has been revolutionized in the past decade by the application of techniques such as protein arrays, two-dimensional gel electrophoresis, and mass spectrometry. These techniques have tremendous potential for biomarker development, target validation, diagnosis, prognosis, and optimization of treatment in medical care, especially in the field of clinical oncology. We will discuss innovations in proteomic technologies and highlight their prospective applications to patient care.