Prostatic acid phosphatase is expressed in human prostate cancer bone metastases and promotes osteoblast differentiation

Enzymes as indispensable markers in disease diagnosis

Enzymes have been used for disease diagnosis for many decades; however, advancements in technology like ELISA and flow cytometry-based detection have significantly increased their use and have increased the sensitivity of detection. Technological advancements in recombinant enzyme production have increased enzymatic stability, and the use of colorimetric-based and florescence-based assays has led to their increased use as biomarkers for disease detection. Enzymes like acid phosphatase, cathepsin, lactate dehydrogenase, thymidine kinase and creatine kinase are indispensable markers for diagnosing cancer, cardiovascular diseases and others. This minireview summarizes various enzymes used in disease diagnosis, their metabolic role, market value and potential as disease markers across various metabolic and other disorders.

The role of prostate-specific antigen in the osteoblastic bone metastasis of prostate cancer: a literature review

Prostate cancer is the only human malignancy that generates predominantly osteoblastic bone metastases, and osteoblastic bone metastases account for more than 90% of osseous metastases of prostate cancer. Prostate-specific antigen (PSA) plays an important role in the osteoblastic bone metastasis of prostate cancer, which can promote osteomimicry of prostate cancer cells, suppress osteoclast differentiation, and facilitate osteoblast proliferation and activation at metastatic sites. In the meantime, it can activate osteogenic factors, including insulin-like growth factor, transforming growth factor β2 and urokinase-type plasminogen activator, and meanwhile suppress osteolytic factors such as parathyroid hormone-related protein. To recapitulate, PSA plays a significant role in the osteoblastic predominance of prostate cancer bone metastasis and bone remodeling by regulating multiple cells and factors involved in osseous metastasis.

Novel signatures of prostate cancer progression and therapeutic resistance

INTRODUCTION

The extensive heterogeneity of prostate cancer (PCa) and multilayered complexity of progression to castration-resistant prostate cancer (CRPC) have contributed to the challenges of accurately monitoring advanced disease. Profiling of the tumor microenvironment with large-scale transcriptomic studies have identified gene signatures that predict biochemical recurrence, lymph node invasion, metastases, and development of therapeutic resistance through critical determinants driving CRPC.

AREAS COVERED

This review encompasses understanding of the role of different molecular determinants of PCa progression to lethal disease including the phenotypic dynamic of cell plasticity, EMT-MET interconversion, and signaling-pathways driving PCa cells to advance and metastasize. The value of liquid biopsies encompassing circulating tumor cells and extracellular vesicles to detect disease progression and emergence of therapeutic resistance in patients progressing to lethal disease is discussed. Relevant literature was added from PubMed portal.

EXPERT OPINION

Despite progress in the tumor-targeted therapeutics and biomarker discovery, distant metastasis and therapeutic resistance remain the major cause of mortality in patients with advanced CRPC. No single signature can encompass the tremendous phenotypic and genomic heterogeneity of PCa, but rather multi-threaded omics-derived and phenotypic markers tailored and validated into a multimodal signature.

Prostate cancer bone metastases biology and clinical management (Review)

Prostate cancer (PCa) is one of the most prominent causes of cancer-related mortality in the male population. A highly impactful prognostic factor for patients diagnosed with PCa is the presence or absence of bone metastases. The formation of secondary tumours at the bone is the most commonly observed site for the establishment of PCa metastases and is associated with reduced survival of patients in addition to a cohort of life-debilitating symptoms, including mobility issues and chronic pain. Despite the prevalence of this disease presentation and the high medical relevance of bone metastases, the mechanisms underlying the formation of metastases to the bone and the understanding of what drives the osteotropism exhibited by prostate tumours remain to be fully elucidated. This lack of in-depth understanding manifests in limited effective treatment options for patients with advanced metastatic PCa and culminates in the low rate of survival observed for this sub-set of patients. The present review aims to summarise the most recent promising advances in the understanding of how and why prostate tumours metastasise to the bone, with the ultimate aim of highlighting novel treatment and prognostic targets, which may provide the opportunity to improve the diagnosis and treatment of patients with PCa with bone metastases.

Procoxacin bidirectionally inhibits osteoblastic and osteoclastic activity in bone and suppresses bone metastasis of prostate cancer

BACKGROUND

Bone is the most common site of metastasis of prostate cancer (PCa). PCa invasion leads to a disruption of osteogenic-osteolytic balance and causes abnormal bone formation. The interaction between PCa and bone stromal cells, especially osteoblasts (OB), is considered essential for the disease progression. However, drugs that effectively block the cancer-bone interaction and regulate the osteogenic-osteolytic balance remain undiscovered.

METHODS

A reporter gene system was constructed to screen compounds that could inhibit PCa-induced OB activation from 631 compounds. Then, the pharmacological effects of a candidate drug, Procoxacin (Pro), on OBs, osteoclasts (OCs) and cancer-bone interaction were studied in cellular models. Intratibial inoculation, micro-CT and histological analysis were used to explore the effect of Pro on osteogenic and osteolytic metastatic lesions. Bioinformatic analysis and experiments including qPCR, western blotting and ELISA assay were used to identify the effector molecules of Pro in the cancer-bone microenvironment. Virtual screening, molecular docking, surface plasmon resonance assay and RNA knockdown were utilized to identify the drug target of Pro. Experiments including co-IP, western blotting and immunofluorescence were performed to reveal the role of Pro binding to its target. Intracardiac inoculation metastasis model and survival analysis were used to investigate the therapeutic effect of Pro on metastatic cancer.

RESULTS

Luciferase reporter gene consisted of Runx2 binding sequence, OSE2, and Alp promotor could sensitively reflect the intensity of PCa-OB interaction. Pro best matched the screening criteria among 631 compounds in drug screening. Further study demonstrated that Pro effectively inhibited the PCa-induced osteoblastic changes without killing OBs or PCa cells and directly killed OCs or suppressed osteoclastic functions at very low concentrations. Mechanism study revealed that Pro broke the feedback loop of TGF-β/C-Raf/MAPK pathway by sandwiching into 14-3-3ζ/C-Raf complex and prevented its disassociation. Pro treatment alleviated both osteogenic and osteolytic lesions in PCa-involved bones and reduced the number of metastases of PCa in vivo.

CONCLUSIONS

In summary, our study provides a drug screening strategy based on the cancer-host microenvironment and demonstrates that Pro effectively inhibits both osteoblastic and osteoclastic lesions in PCa-involved bones, which makes it a promising therapeutic agent for PCa bone metastasis.

Modeling prostate cancer: What does it take to build an ideal tumor model?

Prostate cancer is frequently characterized as a multifocal disease with great intratumoral heterogeneity as well as a high propensity to metastasize to bone. Consequently, modeling prostate tumor has remained a challenging task for researchers in this field. In the past decades, genomic advances have led to the identification of key molecular alterations in prostate cancer. Moreover, resistance towards second-generation androgen-deprivation therapy, namely abiraterone and enzalutamide has unveiled androgen receptor-independent diseases with distinctive histopathological and clinical features. In this review, we have critically evaluated the commonly used preclinical models of prostate cancer with respect to their capability of recapitulating the key genomic alterations, histopathological features and bone metastatic potential of human prostate tumors. In addition, we have also discussed the potential use of the emerging organoid models in prostate cancer research, which possess clear advantages over the commonly used preclinical tumor models. We anticipate that no single model can faithfully recapitulate the complexity of prostate cancer, and thus, propose the use of a cost- and time-efficient integrated tumor modeling approach for future prostate cancer investigations.

Evolving cancer-niche interactions and therapeutic targets during bone metastasis

Many cancer types metastasize to bone. This propensity may be a product of genetic traits of the primary tumour in some cancers. Upon arrival, cancer cells establish interactions with various bone-resident cells during the process of colonization. These interactions, to a large degree, dictate cancer cell fates at multiple steps of the metastatic cascade, from single cells to overt metastases. The bone microenvironment may even influence cancer cells to subsequently spread to multiple other organs. Therefore, it is imperative to spatiotemporally delineate the evolving cancer-bone crosstalk during bone colonization. In this Review, we provide a summary of the bone microenvironment and its impact on bone metastasis. On the basis of the microscopic anatomy, we tentatively define a roadmap of the journey of cancer cells through bone relative to various microenvironment components, including the potential of bone to function as a launch pad for secondary metastasis. Finally, we examine common and distinct features of bone metastasis from various cancer types. Our goal is to stimulate future studies leading to the development of a broader scope of potent therapies.

Can conventional clinical chemistry tests help doctors in the monitoring of oncology patients?

The use of laboratory assays in the diagnostic care of oncology patients can markedly increase the efficacy of cancer treatments. Many cancer-specific biomarker assays have been developed. However, the use of these has some limitations due to their cost. Moreover, not every diagnostic laboratory can perform a complete set of these assays. On the other hand, the smart use of conventional clinical chemistry tests could improve the management of cancer. They could be especially valuable tools in the long-term care of patients with a verified diagnosis. In this review, we discuss the utilization of the conventional clinical chemistry assays for the diagnosis, monitoring and prognosis of various oncological diseases. The use of conventional blood tests to assess the levels of chemical elements, metabolites and proteins (including enzymatic activity measurements) in the care of oncology patients is discussed. We have shown that some clinical chemistry assays could be used in the management of distinct kinds of cancer.

Classification of Homo sapiens gene behavior using linear discriminant analysis fused with minimum entropy mapping

Classification of Homo sapiens gene behavior employing computational biology is a recent research trend. But monitoring gene activity profile and genetic behavior from the alphabetic DNA sequence using a non-invasive method is a tremendous challenge in functional genomics. The present paper addresses such issue and attempts to differentiate Homo sapiens genes using linear discriminant analysis (LDA) method. Annotated protein coding sequences of Homo sapiens genes, collected from NCBI, are taken as test samples. Minimum entropy-based mapping (MEM) technique assists to extract highest information from the numerical DNA sequences. The proposed LDA technique has successfully classified Homo sapiens genes based on the following features: composition of hydrophilic amino acids, dominance of arginine amino acid, and magnitude and size of individual amino acids. The proposed algorithm is successfully tested on 84 Homo sapiens healthy and cancer genes of the prostate and breast cells. Classification performance of the proposed LDA technique is judged by sensitivity (89.12%), specificity (91.9%), accuracy (90.87%), F1 score (92.03%), Matthews' correlation coefficients (81.04%), and miss rate (9.12%), and it outperforms other four existing classifiers. The results are cross-validated through Rayleigh PDF and mutual information technique. Fisher test, 2-sample T-test, and relative entropy test are considered to verify the efficacy of the present classifier.

Urinary proteomic profiles of prostate cancer with different risk of progression and correlation with histopathological features

Prostate cancer (PCa) is the most common tumor in men with extremely variable outcome, varying from latent or indolent form to very aggressive behavior. High grade tumors, expansions exceeding the prostatic capsule into the surrounding soft tissues and spreading through lymph vascular channels, represent the most consistent unfavorable prognostic factors. However, accuracy in the prediction of the disease progression is sometimes difficult. Along with new molecular diagnostic techniques and more accurate histopathological approaches, proteomic studies challenge to identify potential biomarkers predictive of PCa progression. In our study we analyzed the urinary proteomes of 42 patients affected by PCa through two-dimensional electrophoresis associated with mass spectrometry. Proteomic profiles were correlated to histopathological features including pTNM stage and tumor differentiation in order to provide new promising markers able to define more accurately the PCa aggressiveness and driving new therapeutic approaches.

Diagnostic value of acid phosphatases (ACP) in differentiating reactive mesothelial cells from cancer cells in the body fluid effusions

Background

The cytological diagnosis of a malignant epithelial tumor, i.e., a cancer cell in the body fluid effusions is usually made by cytomorphological examination alone; however, diagnostic challenges can occur when the cancer cells are rare or cytological atypia is minimal. Morphological similarity between the cancer and the reactive mesothelial cell is the most common problem in establishing a clear diagnosis. The aim of this study is to investigate whether the cocktail acid phosphatases (ACP) special staining will be a useful tumor marker in differentiation of the reactive mesothelial cells from the cancer cells in the body fluid effusions.

Methods

The cocktail ACP special staining was performed on 212 body fluid effusion samples, which included 128 pleural effusions, 69 ascites, and 15 pericardial effusions.

Results

The mesothelial cells were cocktail ACP positive in 84 out of 84 benign effusion cases, and the sensitivity and the specificity were 100% for the benign effusions which including pleural effusions, ascites, and pericardial effusions. On the other hand, 122 out of 128 cancer cases were cocktail ACP negative, indicating that the sensitivity of using the cocktail ACP staining to rule out the malignant effusions was 95.3%. Thus, the cocktail ACP staining is an excellent marker with high sensitivity and specificity to distinguish the carcinoma from the reactive mesothelial cells in the body fluid effusions.

Conclusions

Our finding provided a new tool for cytopathologists in diagnosing the body fluid effusion that could impact clinical decision making.

Mechanisms of Osteoblastic Bone Metastasis in Prostate Cancer: Role of Prostatic Acid Phosphatase

Prostate cancer (PCa) preferentially metastasizes to bone, leading to complications including severe pain, fractures, spinal cord compression, bone marrow suppression, and a mortality of ∼70%. In spite of recent advances in chemo-, hormonal, and radiation therapies, bone-metastatic, castrate-resistant PCa is incurable. PCa is somewhat unique among the solid tumors in its tendency to produce osteoblastic lesions composed of hypermineralized bone with multiple layers of poorly organized type I collagen fibrils that have reduced mechanical strength. Many of the signaling pathways that control normal bone homeostasis are at play in pathologic PCa bone metastases, including the receptor activator of nuclear factor-κB/receptor activator of nuclear factor-κB ligand/osteoprotegerin system. A number of PCa-derived soluble factors have been shown to induce the dysfunctional osteoblastic phenotype. However, therapies directed at these osteoblastic-stimulating proteins have yielded disappointing clinical results to date. One of the soluble factors expressed by PCa cells, particularly in bone metastases, is prostatic acid phosphatase (PAP). Human PAP is a prostate epithelium-specific secretory protein that was the first tumor marker ever described. Biologically, PAP exhibits both phosphatase activity and ecto-5′-nucleotidase activity, generating extracellular phosphate and adenosine as the final products. Accumulating evidence indicates that PAP plays a causal role in the osteoblastic phenotype and aberrant bone mineralization seen in bone-metastatic, castrate-resistant PCa. Targeting PAP may represent a therapeutic approach to improve morbidity and mortality from PCa osteoblastic bone metastases.

Prostatic Acid Phosphatase (PAP) Predicts Prostate Cancer Progress in a Population-Based Study: The Renewal of PAP?

Objective

To characterize the disease progression and median survival of patients with prostate cancer (PCa) according to the prostatic-specific acid phosphatase (PAP) analysis in a population-based study from the Surveillance, Epidemiology, and End Results (SEER) database.

Materials and Methods

Prostate cancer patients with completed PAP results were identified using the SEER database of the National Cancer Institute. The Mann-Whitney Sum test was utilized to compare the statistical significance for measurement data and ranked data. Data were stratified by ages, races, TNM Classification of Malignant Tumors (TNM), pathological grades, number of tumors, PAP, and survival duration. Multivariable logistic analysis was performed to identify predictors of the presence of invasion and metastases. Cox regression was analyzed for the factors associated with all-cause mortality and prostate cancer-specific mortality. Moreover, survival curve was used to detect the survival months. The unknown data were excluded from these tests.

Results

In total, there are 5184 PAP+ patients and 3161 PAP- patients involved. The Mann-Whitney Sum test showed that slightly greater tumor size (P = 0.03), elevated lymphatic (P = 0.005) and distant (P < 0.001) metastasis rate, higher pathological grade (P < 0.001), localized tumor number (P < 0.001), and shortened survival months (P < 0.001) were observed in the PAP+ group compared with the PAP- group. In the multivariable logistic regression, invasion and metastasis Hazard Ratio (HR) were elevated significantly (P < 0.001) in the PAP+ individuals. In the survival analysis, PAP- patients experienced the prolonged median survival. In the postsurgical patients, the survival months were still longer in PAP+ patients compared with the negative ones (P < 0.001), though surgery prolonged the survival months of both groups. Survival months stratified by localized, invasion, and metastasis situations were analyzed. In the three stratified subgroups, the survival duration is significantly decreased in the PAP+ individuals in the localized PCa group (P < 0.001) and the metastasis group (P = 0.013).

Conclusions

The findings of this study provide population-based estimates of the PCa progress and prognosis for patients with different PAP results, which may suggest a renewed period for the PAP.

Chronic exposure to microcystin-leucine-arginine promoted proliferation of prostate epithelial cells resulting in benign prostatic hyperplasia

Microcystin-leucine-arginine (MC-LR), as a most common and deleterious variant among all structural analogues of Microcystins (MCs), can cause male reproductive dysfunction. However, its toxic effects on prostate in adult mice have not been invested in detail. In this study, we observed that MC-LR could enter prostate tissues and induce focal hyperplasia and prostate inflammation. Moreover, increased levels of prostate specific antigen (PSA) and prostate acid phosphatase (PAP) in serum of mice following chronic exposure to MC-LR were detected. We also examined increased expression of forkhead box protein M1 (FOXM1) and PSA in human prostate epithelial cells (RWPE-1) treated with MC-LR at low levels, and FOXM1 could regulate PSA expression. Furthermore, MC-LR also induced expression of CyclinD1 via FOXM1/Wnt/β-catenin signaling pathways in RWPE-1 cells, promoting proliferation of prostate epithelial cells, resulting in prostatic hyperplasia in vivo. As a foreign substance, MC-LR also induced immune reaction in RWPE-1 cells mediated by NF-κB pathway, promoting production of pro-inflammatory cytokines and chemokines. Collectively, these findings demonstrated that MC-LR may induce prostatic hyperplasia and prostatitis in mice following chronic low-dose exposure to MC-LR. This work may provide new perspectives in developing new diagnosis and treatment strategies for MC-LR-induced prostatic toxicity.

Cancer-secreted hsa-miR-940 induces an osteoblastic phenotype in the bone metastatic microenvironment via targeting ARHGAP1 and FAM134A

Prostate cancer is one of most common cancers in men worldwide, and osteoblastic bone metastasis is frequently observed in prostate cancer patients. However, the mechanisms responsible for the predominantly osteoblastic phenotype have not been fully elucidated. Cancer-secreted microRNAs (miRNAs) were recently shown to be significant in the modification of the tumor microenvironment. Here, hsa-miR-940, which was highly secreted by prostate cancer cells, promoted osteogenic differentiation of human mesenchymal stem cells in vitro, and induced extensive osteoblastic lesions in the bone metastatic microenvironment in vivo. Our study provides a demonstration that osteoblastic bone metastasis can be induced by miRNAs secreted by cancer cells in the bone microenvironment.

Bone metastatic lesions are classified as osteoblastic or osteolytic lesions. Prostate and breast cancer patients frequently exhibit osteoblastic-type and osteolytic-type bone metastasis, respectively. In metastatic lesions, tumor cells interact with many different cell types, including osteoblasts, osteoclasts, and mesenchymal stem cells, resulting in an osteoblastic or osteolytic phenotype. However, the mechanisms responsible for the modification of bone remodeling have not been fully elucidated. MicroRNAs (miRNAs) are transferred between cells via exosomes and serve as intercellular communication tools, and numerous studies have demonstrated that cancer-secreted miRNAs are capable of modifying the tumor microenvironment. Thus, cancer-secreted miRNAs can induce an osteoblastic or osteolytic phenotype in the bone metastatic microenvironment. In this study, we performed a comprehensive expression analysis of exosomal miRNAs secreted by several human cancer cell lines and identified eight types of human miRNAs that were highly expressed in exosomes from osteoblastic phenotype-inducing prostate cancer cell lines. One of these miRNAs, hsa-miR-940, significantly promoted the osteogenic differentiation of human mesenchymal stem cells in vitro by targeting ARHGAP1 and FAM134A. Interestingly, although MDA-MB-231 breast cancer cells are commonly known as an osteolytic phenotype-inducing cancer cell line, the implantation of miR-940–overexpressing MDA-MB-231 cells induced extensive osteoblastic lesions in the resulting tumors by facilitating the osteogenic differentiation of host mesenchymal cells. Our results suggest that the phenotypes of bone metastases can be induced by miRNAs secreted by cancer cells in the bone microenvironment.

Hypercalcaemia and hypocalcaemia: finding the balance

Calcium metabolism in cancer and hypercalcaemia of malignancy

The balance between bone formation and resorption may be disrupted in patients with cancer, leading either to increased bone resorption, calcium release, and possibly hypercalcaemia, or to increased bone formation, sequestration of calcium, and possibly hypocalcaemia. In adults, hypercalcaemia of malignancy is most common in patients with tumours that produce factors that induce osteoclast activation and enhance bone resorption. Impaired renal function and increased renal tubular calcium resorption may further affect calcium levels.

Treatment of hypercalcaemia of malignancy

Inhibitors of bone resorption, first the bisphosphonates and, later, denosumab, have been shown to be effective in hypercalcaemia treatment. Bisphosphonates (which are administered intravenously) are approved for hypercalcaemia of malignancy and are the current mainstay of treatment, whereas denosumab (which is administered subcutaneously) may offer an option for patients who do not respond to bisphosphonates or suffer from renal insufficiency.

Hypocalcaemia: treatment and prevention

Hypocalcaemia is most common in patients with prostate cancer and osteoblastic bone metastases, but can occur in patients with a variety of tumour types who are receiving inhibitors of bone resorption. While patients often respond to calcium and vitamin D supplementation, prevention should be the aim; at-risk patients should be identified before starting treatment with inhibitors of bone resorption, be closely monitored during at least the first few months of treatment, and receive concomitant calcium and vitamin D supplementation unless hypercalcaemia is present.

Conclusion

Both hypercalcaemia and hypocalcaemia can be serious if left untreated. It is therefore important that patients with cancer are closely monitored and receive adequate prevention and treatment measures to maintain normal blood calcium levels.

Prostatic Acid Phosphatase Alters the RANKL/OPG System and Induces Osteoblastic Prostate Cancer Bone Metastases

Prostate cancer (PCa) is unique in its tendency to produce osteoblastic (OB) bone metastases. There are no existing therapies that specifically target the OB phase that affects 90% of men with bone metastatic disease. Prostatic acid phosphatase (PAP) is secreted by PCa cells in OB metastases and increases OB growth, differentiation, and bone mineralization. The purpose of this study was to investigate whether PAP effects on OB bone metastases are mediated by autocrine and/or paracrine alterations in the receptor activator of nuclear factor κ-B (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) system. To investigate whether PAP modulated these factors and altered the bone reaction, we knocked down PAP expression in VCaP cells and stably overexpressed PAP in PC3M cells, both derived from human PCa bone metastases. We show that knockdown of PAP in VCaP cells decreased OPG while increasing RANK/RANKL expression. Forced overexpression of PAP in PC3M cells had the inverse effect, increasing OPG while decreasing RANK/RANKL expression. Coculture of PCa cells with MC3T3 preosteoblasts also revealed a role for secretory PAP in OB-PCa cross talk. Reduced PAP expression in VCaP cells decreased MC3T3 proliferation and differentiation and reduced their OPG expression. PAP overexpression in PC3M cells altered the bone phenotype creating OB rather than osteolytic lesions in vivo using an intratibial model. These findings demonstrate that PAP secreted by PCa cells in OB bone metastases increases OPG and plays a critical role in the vicious cross talk between cancer and bone cells. These data suggest that inhibition of secretory PAP may be an effective strategy for PCa OB bone lesions.

Bioinformatics analysis of differentially expressed proteins in prostate cancer based on proteomics data

We mined the literature for proteomics data to examine the occurrence and metastasis of prostate cancer (PCa) through a bioinformatics analysis. We divided the differentially expressed proteins (DEPs) into two groups: the group consisting of PCa and benign tissues (P&b) and the group presenting both high and low PCa metastatic tendencies (H&L). In the P&b group, we found 320 DEPs, 20 of which were reported more than three times, and DES was the most commonly reported. Among these DEPs, the expression levels of FGG, GSN, SERPINC1, TPM1, and TUBB4B have not yet been correlated with PCa. In the H&L group, we identified 353 DEPs, 13 of which were reported more than three times. Among these DEPs, MDH2 and MYH9 have not yet been correlated with PCa metastasis. We further confirmed that DES was differentially expressed between 30 cancer and 30 benign tissues. In addition, DEPs associated with protein transport, regulation of actin cytoskeleton, and the extracellular matrix (ECM)–receptor interaction pathway were prevalent in the H&L group and have not yet been studied in detail in this context. Proteins related to homeostasis, the wound-healing response, focal adhesions, and the complement and coagulation pathways were overrepresented in both groups. Our findings suggest that the repeatedly reported DEPs in the two groups may function as potential biomarkers for detecting PCa and predicting its aggressiveness. Furthermore, the implicated biological processes and signaling pathways may help elucidate the molecular mechanisms of PCa carcinogenesis and metastasis and provide new targets for clinical treatment.

Mouse models for studying prostate cancer bone metastasis

Once tumor cells metastasize to the bone, the prognosis for prostate cancer patients is generally very poor. The mechanisms involved in bone metastasis, however, remain elusive, because of lack of relevant animal models. In this manuscript, we describe step-by-step protocols for the xenograft mouse models that are currently used for studying prostate cancer bone metastasis. The different routes of tumor inoculation (intraosseous, intracardiac, intravenous and orthotopic) presented are useful for exploring the biology of bone metastasis.

Informative gene selection and the direct classification of tumors based on relative simplicity

BACKGROUND

Selecting a parsimonious set of informative genes to build highly generalized performance classifier is the most important task for the analysis of tumor microarray expression data. Many existing gene pair evaluation methods cannot highlight diverse patterns of gene pairs only used one strategy of vertical comparison and horizontal comparison, while individual-gene-ranking method ignores redundancy and synergy among genes.

RESULTS

Here we proposed a novel score measure named relative simplicity (RS). We evaluated gene pairs according to integrating vertical comparison with horizontal comparison, finally built RS-based direct classifier (RS-based DC) based on a set of informative genes capable of binary discrimination with a paired votes strategy. Nine multi-class gene expression datasets involving human cancers were used to validate the performance of new method. Compared with the nine reference models, RS-based DC received the highest average independent test accuracy (91.40%), the best generalization performance and the smallest informative average gene number (20.56). Compared with the four reference feature selection methods, RS also received the highest average test accuracy in three classifiers (Naïve Bayes, k-Nearest Neighbor and Support Vector Machine), and only RS can improve the performance of SVM.

CONCLUSIONS

Diverse patterns of gene pairs could be highlighted more fully while integrating vertical comparison with horizontal comparison strategy. DC core classifier can effectively control over-fitting. RS-based feature selection method combined with DC classifier can lead to more robust selection of informative genes and classification accuracy.

Comparison of different prostatic markers in lymph node and distant metastases of prostate cancer

Prostate cancer is mostly diagnosed at an early stage; however, some tumors are diagnosed in a metastatic stage as cancer of unknown primary origin. In order to allow specific treatment in the case of prostate cancer presenting as cancer of unknown primary origin, it is important to determine the tumor origin. Prostate-specific antigen is used as a diagnostic marker for prostate cancer but the expression declines with progression to castration-resistant prostate cancer. Aim of this study was to identify the most informative marker constellation, which is able to detect metastatic prostate cancer at high sensitivity. The widely used prostate cancer markers such as prostate-specific antigen, prostate-specific acid phosphatase, androgen receptor, prostate-specific membrane antigen, prostein, and ETS-related gene were investigated for their sensitivity to detect prostatic origin of metastases. Expression of prostate-specific antigen, prostate-specific acid phosphatase, androgen receptor, prostate-specific membrane antigen, prostein, and ETS-related gene was determined on archived tissue specimens consisting of benign prostatic tissue (n=9), primary prostate cancer (n=79), lymph node metastases (n=58), and distant metastases (n=39) using immunohistochemistry. The staining intensity was categorized as negative (0), weak (1), moderate (2), and strong (3). All markers except ETS-related gene were able to detect at least 70% of lymph node metastases and distant metastases, with prostate-specific antigen, androgen receptor, and prostate-specific membrane antigen having the highest sensitivity (97%, 91%, and 94%, respectively). A further increase of the sensitivity up to 98% and 100% could be achieved by the combination of prostate-specific antigen, prostate-specific membrane antigen, or androgen receptor for lymph node metastases and for distant metastases, respectively. The same sensitivity could be reached by combining prostate-specific membrane antigen and prostein. Our data show that a combined staining of at least two prostate markers should be utilized to identify metastases as originating from prostate cancer.

A behavioral study of healthy and cancer genes by modeling electrical network

In recent years, gene network modeling is gaining popularity in genomics to monitor the activity profile of genes. More specifically, the objective of the network modeling concept is to study the genetic behavior associated with disease. Previous researchers have designed network model at nucleotide level which produces more complexity for designing circuits mostly in case of gene expression studies. Whereas the authors have designed the present network model, based on amino acid level which is simpler as well as more appropriate for prediction of the genetic abnormality. In the present concept, SISO continuous and discrete system models of genes are realized using Foster network. The model is designed based on hydropathy index value of amino acids to study the biological system behavior. The time and phase response in continuous (s) domain and pole-zero distribution in discrete (z) domain are used as measurement metric in the present study. The simulated responses of the system show genetic instability for cancer genes which truly reflects the medical reports. The proposed modeling concept can be used, to accurately identify or separate out the diseased genes from healthy genes.

p62/SQSTM1 is required for cell survival of apoptosis-resistant bone metastatic prostate cancer cell lines

BACKGROUND

Bone marrow stromal cell (BMSC) paracrine factor(s) can induce apoptosis in bone metastatic prostate cancer (PCa) cell lines. However, the PCa cells that escape BMSC-induced apoptosis can upregulate cytoprotective autophagy.

METHODS

C4-2, C4-2B, MDA PCa 2a, MDA PCa 2b, VCaP, PC3, or DU145 PCa cell lines were grown in BMSC conditioned medium and analyzed for mRNA and/or protein accumulation of p62 (also known as sequestome-1/SQSTM1), Microtubule-associated protein 1 light chain 3B (LC3B), or lysosomal-associated membrane protein 1 (LAMP1) using quantitative polymerase chain reaction (QPCR), Western blot, or immunofluorescence. Small interfering RNA (siRNA) was used to determine if p62 is necessary PCa cell survival.

RESULTS

BMSC paracrine signaling upregulated p62 mRNA and protein in a subset of the PCa cell lines. The PCa cell lines that were insensitive to BMSC-induced apoptosis and autophagy induction had elevated basal p62 mRNA and protein. In the BMSC-insensitive PCa cell lines, siRNA knockdown of p62 was cytotoxic and immunostaining showed peri-nuclear clustering of autolysosomes. However, in the BMSC-sensitive PCa cell lines, p62 siRNA knockdown was not appreciably cytotoxic and did not affect autolysosome subcellular localization.

CONCLUSIONS

A pattern emerges wherein the BMSC-sensitive PCa cell lines are known to be osteoblastic and express the androgen receptor, while the BMSC-insensitive PCa cell lines are characteristically osteolytic and do not express the androgen receptor. Furthermore, BMSC-insensitive PCa may have evolved a dependency on p62 for cell survival that could be exploited to target and kill these apoptosis-resistant PCa cells in the bone.

Prostate cancer derived prostatic acid phosphatase promotes an osteoblastic response in the bone microenvironment

Approximately 90 % of patients who die of prostate cancer (PCa) have bone metastases, often promoting osteoblastic lesions. We observed that 88 % of castration-resistant PCa (CRPC) bone metastases express prostatic acid phosphatase (PAP), a soluble secreted protein expressed by prostate epithelial cells in predominately osteoblastic (n = 18) or osteolytic (n = 15) lesions. Additionally, conditioned media (CM) of an osteoblastic PCa xenograft LuCaP 23.1 contained significant levels of PAP and promoted mineralization in mouse and human calvaria-derived cells (MC3T3-E1 and HCO). To demonstrate that PAP promotes mineralization, we stimulated MC3T3-E1 cells with PAP and observed increased mineralization, which could be blocked with the specific PAP inhibitor, phosphonic acid. Furthermore, the mineralization promoted by LuCaP 23.1 CM was also blocked by phosphonic acid, suggesting PAP is responsible for the mineralization promoting activity of LuCaP 23.1. In addition, gene expression arrays comparing osteoblastic to osteolytic CRPC (n = 14) identified betacellulin (BTC) as a gene upregulated during the osteoblastic response in osteoblasts during new bone formation. Moreover, BTC levels were increased in bone marrow stromal cells in response to LuCaP 23.1 CM in vitro. Because new bone formation does occur in osteoblastic and can occur in osteolytic CRPC bone metastases, we confirmed by immunohistochemistry (n = 36) that BTC was highly expressed in osteoblasts involved in new bone formation occurring in both osteoblastic and osteolytic sites. These studies suggest a role for PAP in promoting the osteoblastic reaction in CRPC bone metastases and identify BTC as a novel downstream protein expressed in osteoblasts during new bone formation.