Silencing of CD44 expression in prostate cancer by hypermethylation of the CD44 promoter region

Metastasis suppressor genes in clinical practice: are they druggable?

Since the identification of NM23 (now called NME1) as the first metastasis suppressor gene (MSG), a small number of other gene products and non-coding RNAs have been identified that suppress specific parameters of the metastatic cascade, yet which have little or no ability to regulate primary tumor initiation or maintenance. MSG can regulate various pathways or cell biological functions such as those controlling mitogen-activated protein kinase pathway mediators, cell-cell and cell-extracellular matrix protein adhesion, cytoskeletal architecture, G-protein-coupled receptors, apoptosis, and transcriptional complexes. One defining facet of this gene class is that their expression is typically downregulated, not mutated, in metastasis, such that any effective therapeutic intervention would involve their re-expression. This review will address the therapeutic targeting of MSG, once thought to be a daunting task only facilitated by ectopically re-expressing MSG in metastatic cells in vivo. Examples will be cited of attempts to identify actionable oncogenic pathways that might suppress the formation or progression of metastases through the re-expression of specific metastasis suppressors.

Evaluation of CD44 Expression in Prostatic Adenocarcinoma: An Institutional Study

INTRODUCTION

Prostate adenocarcinoma is the second-most common cause of cancer. Globally, many cancer-related deaths among men were noted due to prostate adenocarcinoma. CD44 plays a key role in mediating cell-to-cell and cell-to-matrix interaction, which further helps to maintain the integrity of tissue and also inhibits tumor metastasis.

MATERIALS AND METHODS

Cross-sectional study was done on chips from transurethral resections of the prostate (TURP) and prostatic core biopsy specimens. All specimens with clinically diagnosed and histopathologically confirmed prostatic adenocarcinoma were included in the study. Prostatic intraepithelial neoplasia (PIN), recurrent cases, and patients who had undergone radiotherapy/ chemotherapy prior to biopsy were excluded from the study. The sample size for the current study was 57 with an 8% prevalence value, 95% confidence interval, and 8% absolute error. Immunoreaction to CD44 antibody is membranous and was evaluated by calculating positively stained cell percentage and staining intensity. These two parameters were added to obtain a final score; a score of 0-3 was considered as negative, and a score of 4-6 was regarded as positive.

RESULTS

A statistically significant difference was only found between Gleason grade (p<0.001), clinical staging (p<0.002), nodal metastasis (p<0.015), and distant metastasis (p<0.020) with CD44 positive expression. The rest of the parameters like PSA (p=0.642) and age (p=0.051) did not correlate with CD44-positive expression. Out of 29 cases with positive CD44 expression, 100% positivity was seen in Gleason's grades 1, 2, and 3. This indicates that CD44 expression showed lesser positivity in poorly differentiated carcinoma. CD44 positivity was seen in 83.3% in the T2 stage. An inverse relationship between tumor staging and CD44 expression was observed with positive CD44 expression in lower tumor staging which implies loss of CD44 expression was associated with greater tumor aggressiveness. Lymph node metastasis cases showed more negative CD44 expression (59.5%) and the same was noted in patients without distant metastasis, that is in 61% of the subjects.  Conclusion: Cells tend to lose the ability of CD44 expression as they progress from well-differentiated adenocarcinoma to poorly differentiated adenocarcinoma. CD44 expression suggests that the tumor is in a well-differentiated and gland-forming state as compared to Gleason's grade. Loss of CD44 expression suggests tumor aggressiveness. Thus, the upregulation of CD44 expression can be considered as a potential target for targeted therapy. As many targeted and gene therapies are in clinical trials, large-scale multicentered studies are needed for a better understanding of the clinical course of the disease.

Macrophages Cytokine Spp1 Increases Growth of Prostate Intraepithelial Neoplasia to Promote Prostate Tumor Progression

Prostate cancer development and progression are associated with increased infiltrating macrophages. Prostate cancer is derived from prostatic intraepithelial neoplasia (PIN) lesions. However, the effects macrophages have on PIN progression remain unclear. Here, we showed that the recruited macrophages adjacent to PIN expressed M2 macrophage markers. In addition, high levels of Spp1 transcripts, also known as osteopontin, were identified in these macrophages. Extraneously added Spp1 accelerated PIN cell proliferation through activation of Akt and JNK in a 3D culture setting. We also showed that PIN cells expressed CD44, integrin αv, integrin β1, and integrin β3, all of which have been previously reported as receptors for Spp1. Finally, blockade of Akt and JNK activation through their specific inhibitor completely abolished macrophage Spp1-induced cell proliferation of PIN. Hence, our data revealed Spp1 as another macrophage cytokine/growth factor and its mediated mechanism to upregulate PIN cell growth, thus promoting prostate cancer development.

Overexpression of CBS/H2S inhibits proliferation and metastasis of colon cancer cells through downregulation of CD44

Background

The role of hydrogen sulfide (H₂S) in cancer biology is controversial, including colorectal cancer. The bell-shaped effect of H₂S refers to pro-cancer action at lower doses and anti-cancer effect at higher concentrations. We hypothesized that overexpression of cystathionine-beta-synthase (CBS)/H₂S exerts an inhibitory effect on colon cancer cell proliferation and metastasis.

Methods

Cell proliferation was assessed by Cell Counting Kit-8 (CCK-8), clone-formation and sphere formation assay. Cell migration was evaluated by transwell migration assay. Intracellular H₂S was detected by H₂S probe. Chromatin immunoprecipitation (ChIP) analysis was carried out to examine DNA–protein interaction. Cell experiments also included western blotting, flow cytometry, immunohistochemistry (IHC) and immunofluorescence analysis. We further conducted in vivo experiments to confirm our conclusions.

Results

Overexpression of CBS and exogenous H₂S inhibited colon cancer cell proliferation and migration in vitro. In addition, overexpression of CBS attenuated tumor growth and liver metastasis in vivo. Furthermore, CD44 and the transcription factor SP-1 was probably involved in the inhibitory effect of CBS/H₂S axis on colon cancer cells.

Conclusions

Overexpression of CBS and exogenous provision of H₂S inhibited colon cancer cell proliferation and migration both in vivo and in vitro. Molecular mechanisms might involve the participation of CD44 and the transcription factor SP-1.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-022-02512-2.

CD44: A Multifunctional Mediator of Cancer Progression

CD44, a non-kinase cell surface transmembrane glycoprotein, has been widely implicated as a cancer stem cell (CSC) marker in several cancers. Cells overexpressing CD44 possess several CSC traits, such as self-renewal and epithelial-mesenchymal transition (EMT) capability, as well as a resistance to chemo- and radiotherapy. The CD44 gene regularly undergoes alternative splicing, resulting in the standard (CD44s) and variant (CD44v) isoforms. The interaction of such isoforms with ligands, particularly hyaluronic acid (HA), osteopontin (OPN) and matrix metalloproteinases (MMPs), drive numerous cancer-associated signalling. However, there are contradictory results regarding whether high or low CD44 expression is associated with worsening clinicopathological features, such as a higher tumour histological grade, advanced tumour stage and poorer survival rates. Nonetheless, high CD44 expression significantly contributes to enhanced tumourigenic mechanisms, such as cell proliferation, metastasis, invasion, migration and stemness; hence, CD44 is an important clinical target. This review summarises current research regarding the different CD44 isoform structures and their roles and functions in supporting tumourigenesis and discusses CD44 expression regulation, CD44-signalling pathways and interactions involved in cancer development. The clinical significance and prognostic value of CD44 and the potential of CD44 as a therapeutic target in cancer are also addressed.

The correlation of epithelial-mesenchymal transition-related gene expression and the clinicopathologic features of colorectal cancer patients in Taiwan

Colorectal cancer (CRC) is the third most commonly diagnosed malignancy and the second leading cause of cancer-related deaths in the world. It has been the most prevalent malignancy in Taiwan for consecutive thirteen years. Despite the diversity of its etiologic and pathophysiologic factors, a biological process named as epithelial-mesenchymal transition (EMT) is indispensable in the progression of epithelial cancer. Our aim is to investigate the correlation between the expression of 8 EMT-related proteins (E-cadherin, β-catenin, claudin-1, CD44, N-cadherin, fibronectin, vimentin, S100A4) and the clinicopathologic features of CRC in Taiwan, along with the DNA CpG epigenetic status of CD44 gene. In immunohistochemical assessment, decreased expression of E-cadherin is statistically associated with the progression of cancer stage, while decreased expression of claudin-1 as well as increased β-catenin nuclear translocation and N-cadherin expression is statistically associated with the progression of histopathologic grade. E-cadherin, nuclear β-catenin and claudin-1 are also associated with other important prognostic factors, including nodal metastasis, tumor deposits, and elevated serum CA 19-9 levels. In addition, the left-sided colon and rectal cancers show increased nuclear translocation of β-catenin compared to the right-sided colon cancers, while the rectal cancers show increased fibronectin expression compared to the right-sided and left-sided colon cancers. Moreover, vimentin is aberrantly expressed in one case of signet-ring cell carcinoma. The DNA methylation levels of CD44 gene promoter between the tumoral and non-tumorous tissues by NGS comparison showed statistical difference on six CpG sites. However, such difference may not be sufficient because these DNA methylation proportions are too low to inactivate CD44 gene. Our results demonstrate the expression of E-cadherin, claudin-1, and nuclear β-catenin is closely related to the clinicopathologic prognostic determinants of CRC in Taiwan. The DNA methylation level of CD44 gene and its protein expression, however, show no correlation with the clinicopathologic features in CRC.

Proteolytic Processing of CD44 and Its Implications in Cancer

CD44 is a transmembrane glycoprotein expressed in several healthy and tumor tissues. Modifications in its structure contribute differently to the activity of this molecule. One modification that has provoked interest is the consecutive cleavage of the CD44 extracellular ectodomain by enzymes that belong mainly to the family of metalloproteases. This process releases biologically active substrates, via alternative splice forms of CD44, that generate CD44v3 or v6 isoforms which participate in the transcriptional regulation of genes and proteins associated to signaling pathways involved in the development of cancer. These include the protooncogene tyrosine-protein kinase Src (c-Src)/signal transducer and activator of transcription 3 (STAT3), the epithelial growth factor receptor, the estrogen receptor, Wnt/βcatenin, or Hippo signaling pathways all of which are associated to cell proliferation, differentiation, or cancer progression. Whereas CD44 still remains as a very useful prognostic cell marker in different pathologies, the main topic is that the generation of CD44 intracellular fragments assists the regulation of transcriptional proteins involved in the cell cycle, cell metabolism, and most importantly, the regulation of some stem cell-associated markers.

Hyaluronan-Metal Gold Nanoparticle Hybrids for Targeted Tumor Cell Therapy

In this study, a novel multifunctional nanoplatform based on core-shell nanoparticles of spherical gold nanoparticles (AuNPs) capped with low and high molecular weight (200 and 700 kDa) hyaluronic acid (HA), was assembled via a green, one-pot redox synthesis method at room temperature. A multitechnique characterization approach by UV-visible spectroscopy, dynamic light scattering and atomic force microscopy pointed to the effective 'surface decoration' of the gold nanoparticles by HA, resulting in different grafting densities of the biopolymer chains at the surface of the metal nanoparticle, which in turn affected the physicochemical properties of the nanoparticles. Specifically, the spectral features of the gold plasmonic peak (and the related calculated optical size), the hydrodynamic diameter and the nanoparticle stability were found to depend on the molecular weight of the HA. The CD44-targeting capability of HA-functionalized gold nanoparticles was tested in terms of antibacterial activity and cytotoxicity. An enhanced inhibitory activity against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus was found, with a HA molecular weight (MW)-dependent trend for the HA-capped AuNPs compared to the bare, glucose-capped AuNPs. Cell viability assays performed on two CD44-positive cell models, namely normal human umbilical vein endothelial (HUVEC) and prostate tumor (PC-3) cells, in comparison with neuroblastoma cells (SH-SY5Y), which do not express the CD44 receptor, demonstrated an increased cytotoxicity in neuroblastoma compared to prostate cancer cells upon the cellular treatments by HA-AuNP compared to the bare AuNP, but a receptor-dependent perturbation effect on cytoskeleton actin and lysosomal organelles, as detected by confocal microscopy. These results highlighted the promising potentialities of the HA-decorated gold nanoparticles for selective cytotoxicity in cancer therapy. Confocal microscopy imaging of the two human tumor cell models demonstrated a membrane-confined uptake of HA-capped AuNP in the cancer cells that express CD44 receptors and the different perturbation effects related to molecular weight of HA wrapping the metallic core of the plasmonic nanoparticles on cellular organelles and membrane mobility.

Histone methyltransferase PRMT6 plays an oncogenic role of in prostate cancer

Prostate cancer (PCa) is a major cause of morbidity and mortality. Until now the specific role of histone methyltransferases (HMTs) deregulated expression/activity in PCa is poorly understood. Herein we aimed to uncover the potential oncogenic role of PRMT6 in prostate carcinogenesis. PRMT6 overexpression was confirmed in PCa, at transcript and protein level. Stable PRMT6 knockdown in PC-3 cells attenuated malignant phenotype, increasing apoptosis and decreasing cell viability, migration and invasion. PRMT6 silencing was associated with decreased H3R2me2a levels and increased MLL and SMYD3 expression. PRMT6 silencing increased p21, p27 and CD44 and decreased MMP-9 expression and was associated with PI3K/AKT/mTOR downregulation and increased AR signaling pathway. In Sh-PRMT6 cells, AR restored expression might re-sensitized cells to androgen deprivation therapy, impacting in clinical management of castration-resistant PCa (CRPC). PRMT6 plays an oncogenic role in PCa and predicts for more clinically aggressive disease, constituting a potential target for patients with CRPC.

Identification of key pathways and genes with aberrant methylation in prostate cancer using bioinformatics analysis

Prostate cancer (PCa), a multifocal clinically heterogeneous disease, is the most commonly diagnosed non-cutaneous neoplasm in men worldwide. The epigenome of PCa is a typical representation of catastrophic model of epigenetic alterations during tumorigenesis and its progression. Alterations in methylation patterns in tumor suppressors, cell cycle, oncogenes and metabolism-related genes are the most commonly observed epigenetic alterations in PCa. In this study, we have developed a computational strategy to identify methylated biomarker signature panels as potential targets of PCa by screening >160 genes reported to be epigenetically dysregulated, and shortlisted 26 differentially methylated genes (DMGs) that significantly contribute to oncogenesis. The gene ontology and functional enrichment analysis were performed, which showed that identified DMGs contribute to cellular and metabolic processes such as cell communication, cell cycle, response to drugs, apoptosis and p53 signaling. The top hub genes AR, CDH13, CDKN2A, DAPK1, GSTP1, CD44 and RASSF1 identified from protein-protein interaction network construction using Search Tool for the Retrieval of Interacting Genes contributed to hormonal response, inflammatory response, cell cycle, reactive oxygen species activity and receptor kinase activity, which are related to hallmarks of cancer as revealed by their functional enrichment analysis by Cytoscape. These genes were further scrutinized for CpG islands, transcription start sites and positions of methylated cytosines to study their methylation profiles. Our analysis revealed high negative correlation values between methylation frequencies and gene expressions of the hub genes, namely, AR, CDH13, CDKN2A, DAPK1, CD44, GSTP1 and RASSF1, which can be used as potential diagnostic biomarkers for PCa.

Epigenetic basis of cancer health disparities: Looking beyond genetic differences

Despite efforts at various levels, racial health disparities still exist in cancer patients. These inequalities in incidence and/or clinical outcome can only be explained by a multitude of factors, with genetic basis being one of them. Several investigations have provided convincing evidence to support epigenetic regulation of cancer-associated genes, which results in the differential transcriptome and proteome, and may be linked to a pre-disposition of individuals of certain race/ethnicity to early or more aggressive cancers. Recent technological advancements and the ability to quickly analyze whole genome have aided in these efforts, and owing to their relatively easy detection, methylation events are much well-characterized, than the acetylation events, across human populations. The early trend of investigating a pre-determined set of genes for differential epigenetic regulation is paving way for more unbiased screening. This review summarizes our current understanding of the epigenetic events that have been tied to the racial differences in cancer incidence and mortality. A better understanding of the epigenetics of racial diversity holds promise for the design and execution of novel strategies targeting the human epigenome for reducing the disparity gaps.

EPMA position paper in cancer: current overview and future perspectives

At present, a radical shift in cancer treatment is occurring in terms of predictive, preventive, and personalized medicine (PPPM). Individual patients will participate in more aspects of their healthcare. During the development of PPPM, many rapid, specific, and sensitive new methods for earlier detection of cancer will result in more efficient management of the patient and hence a better quality of life. Coordination of the various activities among different healthcare professionals in primary, secondary, and tertiary care requires well-defined competencies, implementation of training and educational programs, sharing of data, and harmonized guidelines. In this position paper, the current knowledge to understand cancer predisposition and risk factors, the cellular biology of cancer, predictive markers and treatment outcome, the improvement in technologies in screening and diagnosis, and provision of better drug development solutions are discussed in the context of a better implementation of personalized medicine. Recognition of the major risk factors for cancer initiation is the key for preventive strategies (EPMA J. 4(1):6, 2013). Of interest, cancer predisposing syndromes in particular the monogenic subtypes that lead to cancer progression are well defined and one should focus on implementation strategies to identify individuals at risk to allow preventive measures and early screening/diagnosis. Implementation of such measures is disturbed by improper use of the data, with breach of data protection as one of the risks to be heavily controlled. Population screening requires in depth cost-benefit analysis to justify healthcare costs, and the parameters screened should provide information that allow an actionable and deliverable solution, for better healthcare provision.

Expression profile of standard and variants forms of CD44 related to prostate cancer behavior

CD44 is a transmembrane glycoprotein and is regarded as a potential marker in various tumors. The aim of our study was to analyze the expression of the standard form of CD44 (CD44s) and its isoforms in localized prostate cancer (PCa), and to correlate these data with the classical prognostic factors and biochemical recurrence.Ninety-four surgical specimens were analyzed in this study. The expression levels of CD44s and all its 9 variants were analyzed by quantitative real time PCR (qRT-PCR). The control group consisted of 14 specimens from patients with benign prostatic hyperplasia. We correlated all the expression profiles with biochemical recurrence, as defined by a PSA >0.4 ng/mL in a mean follow-up period of 53.3 months. In PCa, CD44s was underexpressed and all the other isoforms were overexpressed. The mean expression level of most variants was higher in patients who had not recurred, and a higher expression of CD44v2 independently correlated with a better recurrence-free survival rate (p=0.045). This variant was also underexpressed in metastatic PCa cell lines. There was no correlation between the expression levels of any of the CD44 isoforms and the classical prognostic factors.We here demonstrated that PCa cases are characterized by a change in the expression of CD44, with a loss of CD44s and an overexpression of all the other CD44 variants. However, during cancer progression we found a loss of expression of all CD44 variants, and a correlation between higher expression of CD44v2 and a better recurrence-free survival rate. The understanding of the CD44 expression patterns in PCa could contribute to its use as a new prognostic marker.

Aberrant DNA methylation and prostate cancer

Prostate cancer (PCa) is the most prevalent cancer, a significant contributor to morbidity and a leading cause of cancer-related death in men in Western industrialized countries. In contrast to genetic changes that vary among individual cases, somatic epigenetic alterations are early and highly consistent events. Epigenetics encompasses several different phenomena, such as DNA methylation, histone modifications, RNA interference, and genomic imprinting. Epigenetic processes regulate gene expression and can change malignancy-associated phenotypes such as growth, migration, invasion, or angiogenesis. Methylations of certain genes are associated with PCa progression. Compared to normal prostate tissues, several hypermethylated genes have also been identified in benign prostate hyperplasia, which suggests a role for aberrant methylation in this growth dysfunction. Global and gene-specific DNA methylation could be affected by environmental and dietary factors. Among other epigenetic changes, aberrant DNA methylation might have a great potential as diagnostic or prognostic marker for PCa and could be tested in tumor tissues and various body fluids (e.g., serum, urine). The DNA methylation markers are simple in nature, have high sensitivity, and could be detected either quantitatively or qualitatively. Availability of genome-wide screening methodologies also allows the identification of epigenetic signatures in high throughput population studies. Unlike irreversible genetic changes, epigenetic alterations are reversible and could be used for PCa targeted therapies.

Epigenetic regulation of prostate cancer

Prostate cancer is a commonly diagnosed cancer in men and a leading cause of cancer deaths. Whilst the underlying mechanisms leading to prostate cancer are still to be determined, it is evident that both genetic and epigenetic changes contribute to the development and progression of this disease. Epigenetic changes involving DNA hypo- and hypermethylation, altered histone modifications and more recently changes in microRNA expression have been detected at a range of genes associated with prostate cancer. Furthermore, there is evidence that particular epigenetic changes are associated with different stages of the disease. Whilst early detection can lead to effective treatment, and androgen deprivation therapy has a high response rate, many tumours develop towards hormone-refractory prostate cancer, for which there is no successful treatment. Reliable markers for early detection and more effective treatment strategies are, therefore, needed. Consequently, there is a considerable interest in the potential of epigenetic changes as markers or targets for therapy in prostate cancer. Epigenetic modifiers that demethylate DNA and inhibit histone deacetylases have recently been explored to reactivate silenced gene expression in cancer. However, further understanding of the mechanisms and the effects of chromatin modulation in prostate cancer are required. In this review, we examine the current literature on epigenetic changes associated with prostate cancer and discuss the potential use of epigenetic modifiers for treatment of this disease.

Metastasis suppressors in human benign prostate, intraepithelial neoplasia, and invasive cancer: their prospects as therapeutic agents

Despite advances in diagnosis and treatment of prostate cancer, development of metastases remains a major clinical challenge. Research efforts are dedicated to overcome this problem by understanding the molecular basis of the transition from benign cells to prostatic intraepithelial neoplasia (PIN), localized carcinoma, and metastatic cancer. Identification of proteins that inhibit dissemination of cancer cells will provide new perspectives to define novel therapeutics. Development of antimetastatic drugs that trigger or mimic the effect of metastasis suppressors represents new therapeutic approaches to improve patient survival. This review focuses on different biochemical and cellular functions of metastasis suppressors known to play a role in prostate carcinogenesis and progression. Ten putative metastasis suppressors implicated in prostate cancer are discussed. CD44s is decreased in both PIN and cancer; Drg-1, E-cadherin, KAI-1, RKIP, and SSeCKS show similar expression between benign epithelia and PIN, but are downregulated in invasive cancer; whereas, maspin, MKK4, Nm23 and PTEN are upregulated in PIN and downregulated in cancer. Moreover, the potential role of microRNA in prostate cancer progression, the understanding of the cellular distribution and localization of metastasis suppressors, their mechanism of action, their effect on prostate invasion and metastasis, and their potential use as therapeutics are addressed.

Global reactivation of epigenetically silenced genes in prostate cancer

Transcriptional silencing associated with aberrant promoter hypermethylation is a common mechanism of inactivation of tumor suppressor genes in cancer cells. To globally profile the genes silenced by hypermethylation in prostate cancer, we screened a whole genome expression microarray for genes reactivated in the LNCaP, DU-145, PC-3, and MDA2b prostate tumor cell lines after treatment with the demethylating drug 5-aza-2-deoxycytidine and the histone deacetylation-inhibiting drug trichostatin A. A total of 2,997 genes showed at least 2-fold upregulation of expression after drug treatment in at least one prostate tumor cell line. For validation, we examined the first 45 genes, ranked by upregulation of expression, which had a typical CpG island and were known to be expressed in the normal cell counterpart. Two important findings were, first, that several genes known to be frequently hypermethylated in prostate cancer were apparent, and, second, that validation studies revealed eight novel genes hypermethylated in the prostate tumor cell lines, four of which were unmethylated in normal prostate cells and hypermethylated in primary prostate tumors (SLC15A3, 66%; KRT7, 54%; TACSTD2, 17%; GADD45b, 3%). Thus, we established the utility of our screen for genes hypermethylated in prostate cancer cells. One of the novel genes was TACSTD2/TROP2, a marker of human prostate basal cells with stem cell characteristics. TACSTD2 was unmethylated in prostatic intraepithelial neoplasia and may have utility in emerging methylation-based prostate cancer tests. Further study of the hypermethylome will provide insight into the biology of the disease and facilitate translational studies in prostate cancer.

Promoter- and cell-specific epigenetic regulation of CD44, Cyclin D2, GLIPR1 and PTEN by methyl-CpG binding proteins and histone modifications

Background

The aim of the current study was to analyze the involvement of methyl-CpG binding proteins (MBDs) and histone modifications on the regulation of CD44, Cyclin D2, GLIPR1 and PTEN in different cellular contexts such as the prostate cancer cells DU145 and LNCaP, and the breast cancer cells MCF-7. Since global chromatin changes have been shown to occur in tumours and regions of tumour-associated genes are affected by epigenetic modifications, these may constitute important regulatory mechanisms for the pathogenesis of malignant transformation.

Methods

In DU145, LNCaP and MCF-7 cells mRNA expression levels of CD44, Cyclin D2, GLIPR1 and PTEN were determined by quantitative RT-PCR at the basal status as well as after treatment with demethylating agent 5-aza-2'-deoxycytidine and/or histone deacetylase inhibitor Trichostatin A. Furthermore, genomic DNA was bisulfite-converted and sequenced. Chromatin immunoprecipitation was performed with the stimulated and unstimulated cells using antibodies for MBD1, MBD2 and MeCP2 as well as 17 different histone antibodies.

Results

Comparison of the different promoters showed that MeCP2 and MBD2a repressed promoter-specifically Cyclin D2 in all cell lines, whereas in MCF-7 cells MeCP2 repressed cell-specifically all methylated promoters. Chromatin immunoprecipitation showed that all methylated promoters associated with at least one MBD. Treatment of the cells by the demethylating agent 5-aza-2'-deoxycytidine (5-aza-CdR) caused dissociation of the MBDs from the promoters. Only MBD1v1 bound and repressed methylation-independently all promoters. Real-time amplification of DNA immunoprecipitated by 17 different antibodies showed a preferential enrichment for methylated lysine of histone H3 (H3K4me1, H3K4me2 and H3K4me3) at the particular promoters. Notably, the silent promoters were associated with unmodified histones which were acetylated following treatment by 5-aza-CdR.

Conclusions

This study is one of the first to reveal the histone code and MBD profile at the promoters of CD44, Cyclin D2, GLIPR1 and PTEN in different tumour cells and associated changes after stimulation with methylation inhibitor 5-aza-CdR.

Evaluation of the frequency of putative prostate cancer stem cells in primary and metastatic prostate cancer

BACKGROUND

Tumour cells with a stem cell-like phenotype have recently been identified in prostate tumors and it has been suggested that this population may be responsible for the diversity of cell types within tumors and also for the initiation of metastases. These cells carry a number of defined markers: they are cd133 and cd44+ve and express high levels of alpha2beta1 integrin. In this study we have, for the first time, assessed matched primary and bone marrow biopsies from prostate cancer patients for the distribution of cells carrying these and a number of other putative stem cell markers.

METHODS

Eleven matched (primary and bone metastasis) specimens from prostate cancer patients were assessed for the presence of cd133, cd44, alpha2beta1 integrin, CXCR4, c-met, alpha6 integrin, and nestin using immunohistochemistry and stain intensity and distribution scored.

RESULTS

In the bone metastases, tumor cells staining positively for cd133 were detected at low frequency in approximately 50% of samples. Staining for nestin was confined to endothelium. Positive staining of tumor cells for the other antigens was present at variable frequency in >70% of metastases with the exception of CXCR4 which was absent from all but 2 specimens. Where positive staining of tumor cells was present in the metastasis, cells staining for each antigen were present in the matched primary with the exception of cd44 which was absent in all but 2/11 matched primary tissues.

CONCLUSIONS

In established metastases no single or combination of marker expression profiles identify the established metastatic phenotype, although cd44 expression was shown to be more frequent in metastases that in primary cancers.

Epigenetics of prostate cancer: beyond DNA methylation

Epigenetic mechanisms permit the stable inheritance of cellular properties without changes in DNA sequence or amount. In prostate carcinoma, epigenetic mechanisms are essential for development and progression, complementing, amplifying and diversifying genetic alterations. DNA hypermethylation affects at least 30 individual genes, while repetitive sequences including retrotransposons and selected genes become hypomethylated. Hypermethylation of several genes occurs in a coordinate manner early in carcinogenesis and can be exploited for cancer detection, whereas hypomethylation and further hypermethylation events are associated with progression. DNA methylation alterations interact with changes in chromatin proteins. Prominent alterations at this level include altered patterns of histone modification, increased expression of the EZH2 polycomb histone methyltransferase, and changes in transcriptional corepressors and coactivators. These changes may make prostate carcinoma particularly susceptible to drugs targeting chromatin and DNA modifications. They relate to crucial alterations in a network of transcription factors comprising ETS family proteins, the androgen receptor, NKX3.1, KLF, and HOXB13 homeobox proteins. This network controls differentiation and proliferation of prostate epithelial cells integrating signals from hormones, growth factors and cell adhesion proteins that are likewise distorted in prostate cancer. As a consequence, prostate carcinoma cells appear to be locked into an aberrant state, characterized by continued proliferation of largely differentiated cells. Accordingly, stem cell characteristics of prostate cancer cells appear to be secondarily acquired. The aberrant differentiation state of prostate carcinoma cells also results in distorted mutual interactions between epithelial and stromal cells in the tumor that promote tumor growth, invasion, and metastasis.

Survey of differentially methylated promoters in prostate cancer cell lines

DNA methylation and copy number in the genomes of three immortalized prostate epithelial and five cancer cell lines (LNCaP, PC3, PC3M, PC3M-Pro4, and PC3M-LN4) were compared using a microarray-based technique. Genomic DNA is cut with a methylation-sensitive enzyme HpaII, followed by linker ligation, polymerase chain reaction (PCR) amplification, labeling, and hybridization to an array of promoter sequences. Only those parts of the genomic DNA that have unmethylated restriction sites within a few hundred base pairs generate PCR products detectable on an array. Of 2732 promoter sequences on a test array, 504 (18.5%) showed differential hybridization between immortalized prostate epithelial and cancer cell lines. Among candidate hypermethylated genes in cancer-derived lines, there were eight (CD44, CDKN1A, ESR1, PLAU, RARB, SFN, TNFRSF6, and TSPY) previously observed in prostate cancer and 13 previously known methylation targets in other cancers (ARHI, bcl-2, BRCA1, CDKN2C, GADD45A, MTAP, PGR, SLC26A4, SPARC, SYK, TJP2, UCHL1, and WIT-1). The majority of genes that appear to be both differentially methylated and differentially regulated between prostate epithelial and cancer cell lines are novel methylation targets, including PAK6, RAD50, TLX3, PIR51, MAP2K5, INSR, FBN1, and GG2-1, representing a rich new source of candidate genes used to study the role of DNA methylation in prostate tumors.

SWI/SNF chromatin-remodeling factors induce changes in DNA methylation to promote transcriptional activation

Brahma (Brm) and brahma-related gene-1 (Brg1) are mammalian homologues of SWI/SNF chromatin-remodeling factor subunits that can regulate both transcriptional activation and repression. Both Brg1 and Brm are mutated or deleted in numerous cancer cell lines, leading to the altered expression of genes that influence cell proliferation and metastasis. Here, we find that the promoters of two such genes, CD44 and E-cadherin, are hypermethylated in cells that have lost Brg1 or Brm. In two carcinoma cell lines that lack functional Brg1 and Brm, CD44 and E-cadherin expression are induced by the demethylating agent 5-aza-2'-deoxycytidine. Transfection with either Brg1 or Brm also induces CD44 and E-cadherin transcription and protein expression in these cells, as well as loss of methylation at sequences in the promoters of both genes. Chromatin immunoprecipitation assays show that Brg1 and Brm associate with these regions of the CD44 and E-cadherin promoters, suggesting that SWI/SNF protein complexes may directly influence the loss of DNA methylation. In vivo, Brm-deficient mice also show methylation and silencing of the CD44 promoter. Collectively, these data implicate loss of SWI/SNF-mediated transcriptional activation as a novel mechanism to increase DNA methylation in cancer cells and provide insight into the mechanisms underlying aberrant gene induction and repression during tumor progression.

Molecular biomarker in prostate cancer: the role of CpG island hypermethylation

CpG island hypermethylation may be one of the earliest somatic genome alterations to occur during the development of multiple cancers. Recently, aberrant methylation patterns for different tumors have been reported. We present a comprehensive review of the literature describing the role of CpG island hypermethylation of DNA from prostatic tissue and bodily fluids from men with prostate cancer. We reviewed the literature to evaluate CpG island hypermethylation in tissue and bodily fluids of men with primary and metastatic prostate cancer. Additionally, we reviewed the literature with respect to CpG island hypermethylation patterns in other urological malignancies. Using modern analytic methods, CpG island hypermethylation detection can be achieved. In men with prostate cancer, correlations between specific gene regulatory region hypermethylation analyses and Gleason score, pathologic stage and tumor recurrence have been demonstrated. CpG island hypermethylation may serve as a useful molecular biomarker for the detection and diagnosis of patients with prostate cancer.

Epigenetic changes in prostate cancer: implication for diagnosis and treatment

Prostate cancer is the most common noncutaneous malignancy and the second leading cause of cancer death among men in the United States. DNA methylation and histone modifications are important epigenetic mechanisms of gene regulation and play essential roles both independently and cooperatively in tumor initiation and progression. Aberrant epigenetic events such as DNA hypo- and hypermethylation and altered histone acetylation have both been observed in prostate cancer, in which they affect a large number of genes. Although the list of aberrantly epigenetically regulated genes continues to grow, only a few genes have, so far, given promising results as potential tumor biomarkers for early diagnosis and risk assessment of prostate cancer. Thus, large-scale screening of aberrant epigenetic events such as DNA hypermethylation is needed to identify prostate cancer-specific epigenetic fingerprints. The reversibility of epigenetic aberrations has made them attractive targets for cancer treatment with modulators that demethylate DNA and inhibit histone deacetylases, leading to reactivation of silenced genes. More studies into the mechanism and consequence of demethylation are required before the cancer epigenome can be safely manipulated with therapeutics as a treatment modality. In this review, we examine the current literature on epigenetic changes in prostate cancer and discuss the clinical potential of cancer epigenetics for the diagnosis and treatment of this disease.

DNA methylation in prostate cancer

Prostate cancer is the most common malignancy and the second leading cause of cancer death among men in the United States. There are three well-established risk factors for prostate cancer: age, race and family history. The molecular bases for these risk factors are unclear; however, they may be influenced by epigenetic events. Epigenetic events covalently modify chromatin and alter gene expression. Methylation of cytosine residues within CpG islands on gene promoters is a primary epigenetic event that acts to suppress gene expression. In tumorigenesis, the normal functioning of the epigenetic-regulatory system is disrupted leading to inappropriate CpG island hypermethylation and aberrant expression of a battery of genes involved in critical cellular processes. Cancer-dependent epigenetic regulation of genes involved in DNA damage repair, hormone response, cell cycle control and tumor-cell adhesion/metastasis can contribute significantly to tumor initiation, progression and metastasis and, thereby, increase prostate cancer susceptibility and risk. In this review, we will discuss current research on genes that are hypermethylated in human prostate cancer. We will also discuss the potential involvement of DNA methylation in age-related, race-related and hereditary prostate cancer, and the potential use of hypermethylated genes as biomarkers to detect prostate cancer and assess its risk.

Molecular biology of prostate cancer

Development of any cancer reflects a progressive accumulation of alterations in various genes. Oncogenes, tumour suppressor genes, DNA repair genes and metastasis suppressor genes have been investigated in prostate cancer. Here, we review current understanding of the molecular biology of prostate cancer. Detailed understanding of the molecular basis of prostate cancer will provide insights into the aetiology and prognosis of the disease, and suggest avenues for therapeutic intervention in the future.

CD44 loss in gastric stromal tumors as a prognostic marker

BACKGROUND

The adhesion molecule CD44 (CD44s; CD44H) and its isoforms (CD44v3-6 and v9) are preferentially expressed by different cell types. These transmembrane glycoproteins are involved in cell-cell and cell-matrix interactions and in cell trafficking and, thus, may play a role in tumor metastasis and/or local invasion. The expression pattern of CD44s and variant isoforms, particularly CD44v6 and CD44v9, of some neoplasms, including soft tissue tumors, correlates with clinical course and outcome. The clinical behavior of gastrointestinal stromal tumors (GIST) is site specific; however, other reliable predictors of clinical outcome have not been identified. Thus, the prognostic value of CD44s and isoform expression in GIST were evaluated by immunohistochemistry of tissue microarrays.

DESIGN

Paraffin-embedded formalin-fixed tissue cores (129: 103 GIST and 26 normal stomach smooth muscle) from 33 patients with clinical outcome data were collected and used for the construction of the tissue microarrays. One to five tissue cores from each patient specimen were evaluated (mean = 3 tissue cores/patient). Array slides were stained with anti-CD44s (CD44H) and with antibodies to v3, v4, v5, v6, and v9 isomers. CD44s and isoform expression and staining intensity were scored semiquantitatively without knowledge of patient identity or outcome: 0 = no; 1 = weak; 2 = moderate; 3 = moderate to strong; 4 = strong. The scores of multiple cores from the same GIST were averaged; the nonneoplastic smooth muscle was similarly graded. CD44s and isoform expression and intensity were compared with outcome.

RESULTS

The 33 patients with gastric GIST, 0.8 to 30 cm in size, were followed for 1 to 111 months with a median follow-up of 7 months (mean 17.5 months). The overall median survival was 25 months. Nine of the 33 (27%) patients had metastases, 9 (27%) had recurrent disease, and 9 (27%) died of disease (9-111 months; mean 39 months; median 23 months). All 18 patients with GIST CD44s expression > 2+ were alive at last follow-up (1-62 months; median 3.5 months; mean 11 months). More than half (53%) of patients with GIST CD44s expression < or = 2+ died (9-111 months; median 23 months; mean 38 months); the median follow-up of the surviving patients with CD44 expression < or = 2 was 5 months (2-22 months; mean 6.5 months; log rank P = 0.07). The majority of tumors were variably positive CD44v3 and CD44v4, but there was minimal staining (number of cases and/or expression level) with antibodies directed against the v5, v6, and v9 isomers.

CONCLUSION

These preliminary results suggest that although gastric GISTs variably express CD44s and variants, only the expression of CD44s correlates with clinical outcome with loss of CD44s positivity correlating with poor clinical outcome.

Human prostate cancer risk factors

Prostate cancer has the highest prevalence of any nonskin cancer in the human body, with similar likelihood of neoplastic foci found within the prostates of men around the world regardless of diet, occupation, lifestyle, or other factors. Essentially all men with circulating androgens will develop microscopic prostate cancer if they live long enough. This review is a contemporary and comprehensive, literature-based analysis of the putative risk factors for human prostate cancer, and the results were presented at a multidisciplinary consensus conference held in Crystal City, Virginia, in the fall of 2002. The objectives were to evaluate known environmental factors and mechanisms of prostatic carcinogenesis and to identify existing data gaps and future research needs. The review is divided into four sections, including 1) epidemiology (endogenous factors [family history, hormones, race, aging and oxidative stress] and exogenous factors [diet, environmental agents, occupation and other factors, including lifestyle factors]); 2) animal and cell culture models for prediction of human risk (rodent models, transgenic models, mouse reconstitution models, severe combined immunodeficiency syndrome mouse models, canine models, xenograft models, and cell culture models); 3) biomarkers in prostate cancer, most of which have been tested only as predictive factors for patient outcome after treatment rather than as risk factors; and 4) genotoxic and nongenotoxic mechanisms of carcinogenesis. The authors conclude that most of the data regarding risk relies, of necessity, on epidemiologic studies, but animal and cell culture models offer promise in confirming some important findings. The current understanding of biomarkers of disease and risk factors is limited. An understanding of the risk factors for prostate cancer has practical importance for public health research and policy, genetic and nutritional education and chemoprevention, and prevention strategies.

Molecular markers to identify patients at risk for recurrence after primary treatment for prostate cancer

Accurate prognostication is a prerequisite for accurate therapeutics and management of prostate cancer because indolent tumors may require no intervention, whereas aggressive tumors lead to patient mortality. There is a critical need to define these subgroups of patients with prostate cancer differing in clinical outcome. Prognostic nomograms based on clinical data provide useful predictions of clinical states and outcomes, but they need further refinements to improve accuracy and universality. Genomic and proteomic analyses have provided many novel markers that may help define prognostic parameters based on the underlying biology of prostate cancer progression at the molecular level. These molecular markers are likely to augment traditional prognostic modalities by providing a set of molecularly defined and quantifiable variables. Encompassing the genome, transcriptome, and proteome of prostate cancer will likely provide "molecular signatures" that will bridge prognostication, prediction, and treatment in a single continuum.

The role of the CD44/ezrin complex in cancer metastasis

CD44 is a cell adhesion molecule that was traditionally known as 'homing receptor'. This molecule is known to interact with the ezrin family (ERM family) members and form a complex that plays diverse roles within both normal and abnormal cells, particularly cancer cells. CD44 and ezrin and their respective complex have properties suggesting that they may be important in the process of tumour-endothelium interactions, cell migrations, cell adhesion, tumour progression and metastasis. This article reviews the role of CD44, ezrin family and the CD44/ezrin complex in cancer cells and their clinical impact in patients with cancer.

Hypermethylation-mediated regulation of CD44 gene expression in human neuroblastoma

The CD44 adhesion receptor is silenced in highly malignant neuroblastomas (NBs) with MYCN amplification. Because its functional expression is associated with decreased tumorigenic properties, CD44 behaves as a tumor suppressor gene in NB and other cancers. Given that the precise mechanisms responsible for CD44 silencing are not elucidated, we investigated whether CD44 expression could be regulated by DNA hypermethylation. The methylation status of CD44 gene promoter and exon 1 regions was analyzed in 12 NB cell lines and 21 clinical samples after bisulfite genomic modification, followed by PCR and single-strand conformation polymorphism analysis and genomic sequencing. The results showed that almost all CD44-negative cell lines displayed hypermethylation in both regions, whereas all CD44-expressing cell lines were unmethylated. These observations correlated with the ability to restore CD44 mRNA and protein expression by treatment of CD44-negative cells with the 5-aza-2'-deoxycytidine demethylating agent. In contrast, no CD44 gene hypermethylation could be detected in 21 NB clinical samples of different stages, irrespective of CD44 expression. Although our results suggest that aberrant methylation of promoter and exon 1 regions is involved in CD44 silencing in NB cell lines, they also indicate that methylation of unidentified regulatory sequences or methylation-independent mechanisms also control the expression of CD44 in primary NB tumors and cell lines. We therefore conclude that CD44 silencing is controlled by complex and tumor cell-specific processes, including gene hypermethylation. Further investigation of other mechanisms and genes involved in CD44 regulation will be needed before demethylation-mediated reactivation of the CD44 gene can be considered as therapeutic strategy for neuroblastoma and perhaps other related cancers.

CD44 in cancer

CD44 is a multistructural and multifunctional cell surface molecule involved in cell proliferation, cell differentiation, cell migration, angiogenesis, presentation of cytokines, chemokines, and growth factors to the corresponding receptors, and docking of proteases at the cell membrane, as well as in signaling for cell survival. All these biological properties are essential to the physiological activities of normal cells, but they are also associated with the pathologic activities of cancer cells. Experiments in animals have shown that targeting of CD44 by antibodies, antisense,and CD44-soluble proteins markedly reduces the malignant activities of various neoplasms, stressing the therapeutic potential of anti-CD44 agents. Furthermore, because alternative splicing and posttranslational modifications generate many different CD44 sequences, including, perhaps, tumor-specific sequences, the production of anti-CD44 tumor-specific agents may be a realistic therapeutic approach. However, in many cancers (renal cancer and non-Hodgkin's lymphomas are exceptions), a high level of CD44 expression is not always associated with an unfavorable outcome. On the contrary, in some neoplams CD44 upregulation is associated with a favorable outcome. Even worse, in many cases different research grows analyzing the same neoplastic disease reached contradictory conclusions regarding the correlation between CD44 expression and disease prognosis, possibly due to differences in methodology. These problems must be resolved before applying anti-CD44 therapy to human cancers.

Morphologic and molecular prognostic markers in prostate cancer

In this review, a series of traditional morphology-based measurements, relatively well-documented ancillary biomarkers, and emerging molecular assays are evaluated for their relative ability to predict prognosis in prostate cancer. Prognostic factors that have achieved widespread use and are classified as category I by the College of American Pathologists' Solid Tumor Prognostic Factor Consensus Conference are compared with newer tests that are beginning to be used in clinical practice (category II) and emerging molecular-based assays that have yet to be widely validated in the published literature or in clinical trials (category III).

Feasibility of assessment of promoter methylation of the CD44 gene in serum of prostate cancer patients

BACKGROUND AND PURPOSE

CD44 is an important metastasis-suppressor gene in prostate cancer. Downregulation of the CD44 gene is attributed to transcription repression by methylation of CpG islands in the promoter region. The feasibility of CD44 promoter methylation measurement as a diagnostic tool was assessed in the serum of patients with cancer of the prostate (CAP).

MATERIALS AND METHODS

Seven serum samples of patients with CAP were investigated for CD44 promoter methylation by methylation-specific PCR. Three patients had proven metastatic disease, and four were free of metastases. Tissues from a variety of normal epithelia were assessed as well.

RESULTS

Methylation of the CD44 promoter was readily detectable in all serum samples, although no distinction could be made between patients with and those without metastatic disease on the basis of the signal intensity of methylation-specific PCR products. Remarkably, tissue specimens from different normal epithelia, especially those of the colon and rectum, repeatedly showed aberrant methylation of the promoter region of CD44.

CONCLUSIONS

In the serum of CAP patients, assessment of the methylation status of CpG islands in the promoter region of the CD44 gene is feasible using methylation-specific PCR. However, because of physiologic promoter methylation in normal tissues, including the colorectal mucosa, assessment of methylation of tumor-derived DNA in the serum of cancer patients lacks tissue specificity and seems not to be applicable in clinical settings.

Hypermethylation of the CD44 gene is associated with progression and metastasis of human prostate cancer

BACKGROUND

CD44 is a metastasis suppressor gene for prostate cancer and the down-regulation of CD44 and its variants is associated with the progression of prostate cancer. Also, hypermethylation of the CpG islands of the CD44 gene is closely associated with transcriptional inactivation, resulting in the decreased expression of CD44. To clarify the exact role of methylation status of CpG islands of CD44 gene in the progression and metastasis of prostate cancer, we investigated the methylation status of this gene in primary and metastatic human prostate tumors obtained from surgery or autopsy.

METHODS

We examined 97 samples from 40 Japanese patients with adenocarcinoma of the prostate. Tumor tissues were obtained from radical prostatectomy specimens from eight patients with stage B, 12 patients with stage C and three patients with stage D1 and at autopsy from 17 hormone-refractory metastatic cases, who had initially responded to the therapy and thereafter relapsed. Distant metastatic tissues were also obtained at autopsy (i.e., liver, lung, kidney, mammary gland, and pelvic lymph nodes) from 10 of 17 hormone-refractory cases. We analyzed the hypermethylation status of CD44 promotor region by PCR using genomic DNAs digested with the m(5)C-sensitive restriction enzyme HpaII.

RESULTS

The correlation between the methylation status of CD44 gene and the stage progression of prostate cancer was statistically significant (P = 0.0438). In two of 10 hormone-refractory cases, a comparison of the methylation status of the CD44 gene in metastases to that in primary tumors revealed interfocal heterogeneity of CD44 methylation status.

CONCLUSIONS

These results indicate an important role of CD44 methylation in the progression and metastasis of prostate cancer, although the amount of methylational heterogeneity is substantial among metastatic sites within the same patient.