Endothelin B receptor gene hypermethylation in prostate adenocarcinoma

Mechanistic Insights into Harmine-Mediated Inhibition of Human DNA Methyltransferases and Prostate Cancer Cell Growth

Mammalian DNA methyltransferases (DNMTs), including DNMT1, DNMT3A, and DNMT3B, are key DNA methylation enzymes and play important roles in gene expression regulation. Dysregulation of DNMTs is linked to various diseases and carcinogenesis, and therefore except for the two approved anticancer azanucleoside drugs, various non-nucleoside DNMT inhibitors have been identified and reported. However, the underlying mechanisms for the inhibitory activity of these non-nucleoside inhibitors still remain largely unknown. Here, we systematically tested and compared the inhibition activities of five non-nucleoside inhibitors toward the three human DNMTs. We found that harmine and nanaomycin A blocked the methyltransferase activity of DNMT3A and DNMT3B more efficiently than resveratrol, EGCG, and RG108. We further determined the crystal structure of harmine in complex with the catalytic domain of the DNMT3B-DNMT3L tetramer revealing that harmine binds at the adenine cavity of the SAM-binding pocket in DNMT3B. Our kinetics assays confirm that harmine competes with SAM to competitively inhibit DNMT3B-3L activity with a Ki of 6.6 μM. Cell-based studies further show that harmine treatment inhibits castration-resistant prostate cancer cell (CRPC) proliferation with an IC50 of ∼14 μM. The CPRC cells treated with harmine resulted in reactivating silenced hypermethylated genes compared to the untreated cells, and harmine cooperated with an androgen antagonist, bicalutamide, to effectively inhibit the proliferation of CRPC cells. Our study thus reveals, for the first time, the inhibitory mechanism of harmine on DNMTs and highlights new strategies for developing novel DNMT inhibitors for cancer treatment.

The value of endothelin receptor type B promoter methylation as a biomarker for the risk assessment and diagnosis of prostate cancer: A meta-analysis

Previous researches have demonstrated that the methylation status of the EDNRB promoter was associated with the prostate cancer (PCa), but these conclusions remained controversial. Thus, the aim of this meta-analysis was to evaluate the association between EDNRB promoter methylation and the PCa. According to the PRISMA statement, the Web of Science, PubMed, EMBASE, and Cochrane Library databases were retrieved. The ORs and 95 % CIs were analyzed to evaluate the associations between EDNRB promoter methylation and the risk and clinical features of PCa. Heterogeneity among the included studies was estimated by I² statistic and Q test. Publication bias and sensitivity analysis were utilized to test the robustness of our outcomes. In addition, the pooled sensitivity and specificity were calculated to assess the diagnostic value of EDNRB methylation for PCa. Ultimately, 11 eligible studies were included. Under the random-effects model, the pooled OR shown that the frequency of EDNRB methylation was substantially higher in cases compared with controls (OR = 5.42, 95 % CI = 1.98-14.88, P = 0.001). The similar results were also found by the data from TCGA database. Subgroup analysis according to the methylation detection method showed that the heterogeneity in quantitative methylation-specific polymerase chain reaction (qMSP) group was insignificant (I² = 0.0 %, P = 0.669). Moreover, the pooled sensitivity for all-inclusive studies was 0.55 (95 % CI: 0.26-0.81), and the pooled specificity was 0.93 (95 % CI: 0.55-0.99). The methylation of EDNRB promoter might increase the risk of PCa. Meanwhile, EDNRB promoter methylation test combined with PSA testing and/or other biomarkers could be promising diagnostic biomarkers for more accurate detection of PCa.

Methylation analysis of EDNRB in human colon tissues of Hirschsprung's disease

PURPOSE

Hirschsprung's disease (HSCR) is characterized by absence of the enteric nervous system in a variable portion of the distal gut. The endothelin receptor type B (EDNRB) gene has been localized to the chromosome 13q22 region and encodes a G-protein coupled receptor, is generally accepted as a crucial gene for HSCR. This study is to identify the epigenetic changes of EDNRB in the pathogenesis of HSCR.

METHODS

We investigated the expression levels of EDNRB in 58 HSCR patients and 25 unrelated controls, using reverse transcriptase polymerase chain reaction (RT-PCR) and western blot assay. Moreover, using the methylation-specific polymerase chain reaction, we examined the methylation status of the promoter region of EDNRB.

RESULTS

Aberrant high expression level of EDNRB was detected in HSCR patients compared with the control group (P = 0.023). Besides, western blot assay confirmed the up-regulation of EDNRB in the post transcription level in the aganglionosis segment of HSCR patients. Furthermore, there was a significantly lower ratio of methylation level of EDNRB in HSCR.

CONCLUSIONS

Our study demonstrates that epigenetic inactivation of the EDNRB gene may play a role in the development of HSCR.

Early progress in epigenetic regulation of endothelin pathway genes

Control of gene transcription is a major regulatory determinant for function of the endothelin pathway. Epigenetic mechanisms act on tissue-specific gene expression during development and in response to physiological stimuli. Most of the limited evidence available on epigenetic regulation of the endothelin pathway focuses on the EDN1 and EDNRB genes. Examination of whole genome databases suggests that both genes are influenced by histone modifications and DNA methylation. This interpretation is supported by studies directed at detecting epigenetic action on the two genes. The clearest illustration of epigenetic factors altering endothelin signalling is DNA methylation-associated EDNRB silencing during tumourigenesis. This review summarizes our current understanding of epigenetic regulation of the endothelin pathway genes. LINKED ARTICLES This article is part of a themed section on Endothelin. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.168.issue-1.

Promoter hypermethylation in primary squamous cell carcinoma of the oral cavity and oropharynx: a study of a Brazilian cohort

Epigenetic silencing of cancer-related genes plays an important role in oral/oropharyngeal squamous cell carcinoma (OSCC). We evaluated promoter hypermethylation of 4 cancer-related genes in OSCCs of a Brazilian cohort and determined its relationship with exposure to alcohol, tobacco, HPV infection and clinicopathological parameters. CDKN2A (cyclin-dependent kinase inhibitor 2A or p16), SFN (stratifin or 14-3-3 σ), EDNRB (endothelin receptor B) and RUNX3 (runt-related transcript factor-3) had their methylation patterns evaluated by MSP analysis in OSCC tumors (n = 45). HPV detection was carried out by PCR/RFLP. Aberrant methylation was detected in 44/45 (97.8 %) OSCC; 24.4 % at CDKN2A, 77.8 % at EDNRB, 17.8 % at RUNX3 and 97.8 % at SFN gene. There was no significant association between methylation patterns and clinical parameters. HPV (subtype 16) was detected in 3 out of 45 patients (6 %). Our findings indicate that HPV infection is uncommon and methylation is frequent in Brazilian OSCCs, however, EDNRB and SFN gene methylation are not suitable OSCC biomarkers due to indistinct methylation in tumoral and normal samples. In contrast, CDKN2A and RUNX3 genes could be considered differentially methylated genes and potential tumor markers in OSCCs.

DNA methylation in promoter region as biomarkers in prostate cancer

The prostate gland is the most common site of cancer and the second leading cause of cancer death in American men. Recent emerging molecular biological technologies help us to know that epigenetic alterations such as DNA methylation within the regulatory (promoter) regions of genes are associated with transcriptional silencing in cancer. Promoter hypermethylation of critical pathway genes could be potential biomarkers and therapeutic targets for prostate cancer. In this chapter, we updated current information on methylated genes associated with the development and progression of prostate cancer. Over 40 genes have been investigated for methylation in promoter region in prostate cancer. These methylated genes are involved in critical pathways, such as DNA repair, metabolism, and invasion/metastasis. The role of hypermethylated genes in regulation of critical pathways in prostate cancer is discussed. These findings may provide new information of the pathogenesis, the exciting potential to be predictive and to provide personalized treatment of prostate cancer. Indeed, some epigenetic alterations in prostate tumors are being translated into clinical practice for therapeutic use.

Role of the endothelin axis and its antagonists in the treatment of cancer

The endothelins (ET) are a group of proteins that act through G-protein coupled receptors. Endothelin-1 (ET-1) was initially identified as a potent vasoconstrictor and dysregulation of the ET axis contributes to pathological processes responsible for cardiovascular disease states. More recently, the ET axis, in particular ET-1 acting through the endothelin A receptor (ET(A) ), has been implicated in the development of several cancers through activation of pathways involved in cell proliferation, migration, invasion, epithelial-mesenchymal transition, osteogenesis and angiogenesis. The endothelin B receptor (ET(B) ) may counter tumour progression by promoting apoptosis and clearing ET-1; however, it has recently been implicated in the development of some tumour types including melanomas and oligodendrogliomas. Here, we review emerging preclinical and clinical data outlining the role of the ET axis in cancer, and its antagonism as an attractive and challenging approach to improve clinical cancer management. Clinical data of ET(A) antagonists in patients with prostate cancer are encouraging and provide promise for new ET(A) antagonist-based treatment strategies. Given the unexpected opportunities to affect pleiotrophic tumorigenic signals by targeting ET(A)-mediated pathways in a number of cancers, the evaluation of ET-targeted therapy in cancer warrants further investigation.

Re-expression of the methylated EDNRB gene in oral squamous cell carcinoma attenuates cancer-induced pain

Endothelin-1 is a vasoactive peptide that activates both the endothelin A (ET(A)) and endothelin B (ET(B)) receptors, and is secreted in high concentrations in many different cancer environments. Although ET(A) receptor activation has an established nociceptive effect in cancer models, the role of ET(B) receptors on cancer pain is controversial. EDNRB, the gene encoding the ET(B) receptor, has been shown to be hypermethylated and transcriptionally silenced in many different cancers. In this study we demonstrate that EDNRB is heavily methylated in human oral squamous cell carcinoma lesions, which are painful, but not methylated in human oral dysplasia lesions, which are typically not painful. ET(B) mRNA expression is reduced in the human oral squamous cell carcinoma lesions as a consequence of EDNRB hypermethylation. Using a mouse cancer pain model, we show that ET(B) receptor re-expression attenuates cancer-induced pain. These findings identify EDNRB methylation as a novel regulatory mechanism in cancer-induced pain and suggest that demethylation therapy targeted at the cancer microenvironment has the potential to thwart pain-producing mechanisms at the source, thus freeing patients of systemic analgesic toxicity.

Methylation analysis of cancer-related genes in non-neoplastic cells from patients with oral squamous cell carcinoma

Early detection of Oral Squamous Cell Carcinoma (OSCC) is important to reduce mortality rates and to help provide successful cancer treatment. Hypermethylation of CpG islands is a common epigenetic mechanism that leads to gene silencing in tumors and could be a useful biomarker in OSCC. Abnormal DNA hypermethylation can occur very early in cancer development and may be induced by exposure to environmental carcinogens. We set out to investigate the methylation status of cancer-related genes in normal oral exfoliated cells from OSCC patients and healthy volunteers, as well as possible associations with alcohol/tobacco exposure or specific tumor characteristics. The methylation status of CDKN2A (cyclin-dependent kinase inhibitor 2A or p16), SFN (stratifin or 14-3-3 σ), EDNRB (endothelin receptor B) and RUNX3 (runt-related transcript factor-3) was evaluated by MSP (Methylation-Specific Polymerase Chain Reaction) analysis in non-neoplastic oral epithelial cells from OSCC patients (n = 70) and cancer-free subjects (n = 41). Hypermethylation was observed in CDKN2A, EDNRB and SFN genes, whereas no methylation was found in the RUNX3 gene. CDKN2A hypermethylation occurred only in the OSCC group (5.7%) while SFN and EDNRB hypermethylation occurred in both groups. There was no association between hypermethylation and smoking, drinking habits or specific tumor characteristics.

Quantitative analysis of promoter methylation of the EDNRB gene in gastric cancer

Hypermethylation has been shown in the promoter region of the endothelin receptor B (EDNRB) gene in several human tumors. However, its role in gastric cancer formation is still unclear. In this study, the methylation status of the EDNRB gene in paired gastric cancer tissues and adjacent normal tissues from 96 patients was detected quantitatively using pyrosequencing. The results showed the methylation of promoter of EDNRB gene in gastric cancer (50.42 ± 9.03%) was significantly higher than in adjacent normal tissues (6.47 ± 2.98%) (P < 0.01). Among 96 tumor tissues, promoter hypermethylation of the EDNRB gene was correlated with tumor infiltration (T1: 47.4 ± 7.31% T2:48.2 ± 9.17% T3:52.9 ± 6.48% T4:53.2 ± 10.45%), lymph node metastasis (N0:45.4 ± 6.99% N1:49.0 ± 9.10% N2:52.0 ± 8.40% N3:53.7 ± 9.92%), and distant metastasis (M0:48.9 ± 6.99% M1:53.9 ± 11.98%) (P < 0.05), but it was not associated with other clinicopathological characteristics. In addition, the treatment of the human gastric cancer cell line, SGC-7901, with demethylation agent can restore the expression of EDNRB. Our results suggest that promoter hypermethylation of EDNRB gene is highly prevalent in gastric cancer, which may play a role in the pathogenesis of gastric cancer. Futhermore, hypermethylation of EDNRB gene was remarkably related to infiltration and metastasis of gastric cancer and may attribute to the tumor progression.

Promoter hypermethylation in prostate cancer

BACKGROUND

The prostate gland is the most common site of cancer and the second leading cause of cancer mortality in American men. It is well known that epigenetic alterations such as DNA methylation within the regulatory (promoter) regions of genes are associated with transcriptional silencing in cancer. Promoter hypermethylation of critical pathway genes could be potential biomarkers and therapeutic targets for prostate cancer.

METHODS

This review discusses current information on methylated genes associated with prostate cancer development and progression.

RESULTS

Over 30 genes have been investigated for promoter methylation in prostate cancer. These methylated genes are involved in critical pathways, such as DNA repair, metabolism, and invasion/metastasis. The role of hypermethylated genes in regulation of critical pathways in prostate cancer is reviewed.

CONCLUSIONS

These findings may provide new information of the pathogenesis of prostate cancer. Certain epigenetic alterations in prostate tumors are being translated into clinical practice for therapeutic use.

Treatment with 5-Aza-2'-deoxycytidine induces promoter demethylation of the EDNRB gene and inhibits cell proliferation in human gastric carcinoma cell line SGC-7901

AIM: To investigate the effects of 5-Aza-2'-deoxycytidine on promoter hypermethylation of the EDNRB gene and cell proliferation in human gastric carcinoma cell line SGC-7901.

METHODS: After SGC-7901 cells were treated with different concentrations (1, 2, 5, 10 μmol/L) of 5-Aza-2'-deoxycytidine, the promoter methylation status of the EDNRB gene in SGC-7901 cells was analyzed using methylation-specific polymerase chain reaction (MSP); the expression of EDNRB gene in SGC-7901 cells was detected by reverse transcription polymerase chain reaction (RT-PCR); cell proliferation was measured by MTT assay; and cell cycle distribution and apoptosis were analyzed by flow cytometry.

RESULTS: Before treatment with 5-Aza-2'-deoxycytidine, promoter hypermethylation of the EDNRB gene was detected in SGC-7901 cells. Accordingly, the expression of EDNRB mRNA was not detected in SGC-7901 cells. After treatment of cells with 5-Aza-2'-deoxycytidine for four days, promoter demethylation of the EDNRB gene was induced and EDNRB mRNA expression was detected. Treatment with 5-Aza-2'-deoxycytidine restrained the proliferation of SGC-7901 cells in a time- and dose-dependent manner. Treatment with 5-Aza-CdR induced cell cycle arrest in S phase. The apoptosis rate was significantly higher in SGC-7901 cells treated with 5 or 10 μmol/L 5-Aza-CdR than in control cells (7.13% ± 0.87%, 13.34% ± 1.12% vs 3.69% ± 0.52%, both P < 0. 05).

CONCLUSION: 5-Aza-2'-deoxycytidine can effectively induce promoter demethylation of the EDNRB gene, activate EDNRB gene expression, and inhibit cell growth in human gastric carcinoma cell line SGC-7901.

Promoter hypermethylation in Indian primary oral squamous cell carcinoma

We evaluated promoter hypermethylation of a panel of tumor suppressor genes as a means to detect epigenetic alterations in oral squamous cell carcinomas (OSCC) of Indian-origin and compare with North-American head and neck squamous cell carcinomas (HNSCC). Quantitative-methylation-specific PCR was used to investigate the promoter methylation status of DCC, EDNRB, p16(INK4a) and KIF1A in 92 OSCC, and compared to 48 paired normal tissues and 30 saliva and sera samples from healthy control subjects. Aberrant methylation of at-least one of these genes was detected in 74/92 (80.4%) OSCC; 72.8% at EDNRB, 71.7% at KIF1A, 47.8% at p16(INK4a) and 58.7% at DCC; and in 5 of 48 (10.4%) normal oral tissues. None of the saliva and sera samples from controls exhibited DNA methylation in these four target genes. Thirty-two of 72 node positive cases harbored p16(INK4a) and DCC hypermethylation (p = 0.005). Thus, promoter hypermethylation in genes analyzed herein is a common event in Indian OSCC and may represent promising markers for the molecular staging of OSCC patients. We found higher frequency of p16(INK4a) methylation (47.8%) in this Indian cohort in comparison with a North-American cohort (37.5%). In conclusion, aberrant methylation of EDNRB, KIF1A, DCC and p16(INK4a) genes is a common event in Indian OSCC, suggesting that epigenetic alterations of these genes warrant validation in larger studies for their potential use as biomarkers.

Mechanism of cancer pain

Ongoing and breakthrough pain is a primary concern for the cancer patient. Although the etiology of cancer pain remains unclear, animal models of cancer pain have allowed investigators to unravel some of the cancer-induced neuropathologic processes that occur in the region of tumor growth and in the dorsal horn of the spinal cord. Within the cancer microenvironment, cancer and immune cells produce and secrete mediators that activate and sensitize primary afferent nociceptors. Pursuant to these peripheral changes, nociceptive secondary neurons in spinal cord exhibit increased spontaneous activity and enhanced responsiveness to three modes of noxious stimulation: heat, cold, and mechanical stimuli. As our understanding of the peripheral and central mechanisms that underlie cancer pain improves, targeted analgesics for the cancer patient will likely follow.

Endothelin receptor type B gene promoter hypermethylation in salivary rinses is independently associated with risk of oral cavity cancer and premalignancy

Endothelin receptor type B (EDNRB) and kinesin family member 1A (KIF1A) are candidate tumor suppressor genes that are inactivated in cancers. In this study, we evaluated the promoter hypermethylation of EDNRB and KIF1A and their potential use for risk classification in prospectively collected salivary rinses from patients with premalignant/malignant oral cavity lesions. Quantitative methylation-specific PCR was performed to analyze the methylation status of EDNRB and KIF1A in salivary rinses of 191 patients. We proceeded to determine the association of methylation status with histologic diagnosis and estimate classification accuracy. On univariate analysis, diagnosis of dysplasia/cancer was associated with age and KIF1A or EDNRB methylation. Methylation of EDNRB highly correlated with that of KIF1A (P < 0.0001). On multivariable modeling, histologic diagnosis was independently associated with EDNRB (P = 0.0003) or KIF1A (P = 0.027) methylation. A subset of patients analyzed (n = 161) without prior biopsy-proven malignancy received clinical risk classification based on examination. On univariate analysis, EDNRB and risk classification were associated with diagnosis of dysplasia/cancer and remained significant on multivariate analysis (EDNRB: P = 0.047, risk classification: P = 0.008). Clinical risk classification identified dysplasia/cancer with a sensitivity of 71% and a specificity of 58%. The sensitivity of clinical risk classification combined with EDNRB methylation improved to 75%. EDNRB methylation in salivary rinses was independently associated with histologic diagnosis of premalignancy and malignancy and may have potential in classifying patients at risk for oral premalignant and malignant lesions in settings without access to a skilled dental practitioner. This may also potentially identify patients with premalignant and malignant lesions that do not meet the criteria for high clinical risk based on skilled dental examination.

Promoter methylation in prostate cancer and its application for the early detection of prostate cancer using serum and urine samples

Prostate cancer is the second most common cancer and the second leading cause of cancer death in men. However, prostate cancer can be effectively treated and cured, if it is diagnosed in its early stages when the tumor is still confined to the prostate. Combined with the digital rectal examination, the PSA test has been widely used to detect prostate cancer. But, the PSA screening method for early detection of prostate cancer is not reliable due to the high prevalence of false positive and false negative results. Epigenetic alterations including hypermethylation of gene promoters are believed to be the early events in neoplastic progression and thus these methylated genes can serve as biomarkers for the detection of cancer from clinical specimens. This review discusses DNA methylation of several gene promoters during prostate carcinogenesis and evaluates the usefulness of monitoring methylated DNA sequences, such as GSTP1, RASSF1A, RARβ2 and galectin-3, for early detection of prostate cancer in tissue biopsies, serum and urine.

DNA methylation changes in prostate cancer: current developments and future clinical implementation

Promoter hypermethylation is associated with the loss of expression of tumor-suppressor genes in cancer. Currently, several genome-wide technologies are available and have been utilized to examine the extent of DNA methylation in discovery-based studies involving several physiological and disease states. Although early in the process, aberrant DNA methylation is gaining strength in the fields of cancer risk assessment, diagnosis and therapy monitoring in different cancer types. There is a need to improve existing methods for early diagnosis of prostate cancer and to identify men at risk for developing aggressive disease. Because of the ubiquity of DNA methylation changes and the ability to detect methylated DNA in several body fluids (e.g., blood and urine), this specifically altered DNA may serve, on one hand, as a possible new screening marker for prostate cancer and, on the other hand, as a tool for therapy monitoring in patients having had neoplastic disease of the prostate. Since many prostate cancer patients present with advanced disease and some present with nonspecific elevation of prostate-specific antigen without prostate cancer, early detection with high specificity and sensitivity is considered to be one of the most important approaches to reduce mortality and unwanted tension of the men with high prostate-specific antigen. Therefore, an effective screening test would have substantial clinical benefits. Furthermore, methylation markers of risk of progression of disease in patients having prostate cancer permits immediate commencement of specific treatment regimens and probably longer survival and better quality of life. This review illustrates the current benefits and limitations of potentially useful prostate cancer methylation markers that have considerable existing data and touches upon other future markers as well as the field of methylation in prostate cancer.

CpG island hypermethylation at multiple gene sites in diagnosis and prognosis of prostate cancer

OBJECTIVES

CpG island hypermethylation causes gene silencing and could be decisive in prostate carcinogenesis and progression. We investigated its role at multiple gene sites during prostate carcinogenesis.

METHODS

A quantitative, methylation-specific polymerase chain reaction was used to analyze the hypermethylation patterns at nine gene loci (Annexin2, APC, EDNRB, GSTP1, PTGS2, MDR1, RARbeta, Reprimo, and TIG1) in 80 patients with prostate cancer (PCa) and 26 patients with benign prostatic hyperplasia (BPH).

RESULTS

Hypermethylation was more frequent in PCa than in BPH tissues (EDNRB, 100% versus 88%; TIG1, 96% versus 12%; RARbeta, 95% versus 35%; GSTP1, 93% versus 15%; APC, 80% versus 50%; MDR1, 80% versus 31%; PTGS2, 68% versus 15%; Reprimo, 59% versus 19%; and Annexin2, 4% versus 0%). TIG1 and GSTP1 hypermethylation distinguished between PCa and BPH with a specificity of greater than 85% and sensitivity of greater than 93%. Hypermethylation at a single gene locus did not correlate with any clinicopathologic variables. In contrast, hypermethylation at two genes (eg, APC and TIG1, APC and GSTP1, APC and PTGS2, APC or MDR, GSTP1 or PTGS2) correlated significantly with the pathologic stage and/or Gleason score (P = 0.033 to 0.045). Hypermethylation at APC and Reprimo, as well as DNA hypermethylation at more than five genes, correlated significantly with the rate of prostate-specific antigen recurrence after radical prostatectomy (P = 0.0078 and P = 0.0074, respectively).

CONCLUSIONS

Our results have confirmed that the hypermethylation patterns are helpful in the diagnosis and prognosis of PCa. Increases in CpG island hypermethylation at multiple gene sites occur during PCa progression and indicate early biochemical recurrence after radical prostatectomy.

Epigenetic and genetic alterations of the EDNRB gene in nasopharyngeal carcinoma

BACKGROUND

Loss of heterozygosity (LOH) at 13q22 is a common event in nasopharyngeal carcinoma (NPC). EDNRB gene located at 13q22 has been demonstrated to be hypermethylated in some kinds of tumors. In the current study, we focused on the epigenetic and genetic alterations of EDNRB in NPC.

METHODS

The mRNA expression of EDNRB was detected by semiquantitative RT-PCR and real-time quantitative PCR in 49 NPC and 12 chronic nasopharyngitis biopsies. The methylation and LOH status of EDNRB were examined by methylation-specific polymerase chain reaction, microsatellite PCR and sequencing. We also examined the mRNA expression of EDNRB in four NPC cell lines after 5-aza-2'-deoxycytidine treatment.

RESULTS

EDNRB was downregulated in primary NPC tissues and NPC cell lines, and a relatively higher methylation level of EDNRB was found in NPC biopsies (84%) compared to that in chronic nasopharyngitis biopsies (42%). Treatment of NPC cell lines with 5-aza-2'-deoxycytidine activated EDNRB expression. LOH of EDNRB gene was also found at two microsatellite sites with ratios of 6.25 and 16.67% in NPC.

CONCLUSION

Our results suggested that EDNRB expression may be affected by aberrant promoter methylation and gene deletion and may play a role in the development of NPC.

Prostate cancer epigenetics: a review on gene regulation

Prostate cancer is the most common cancer in men in western countries, and its incidence is increasing steadily worldwide. Molecular changes including both genetic and epigenetic events underlying the development and progression of this disease are still not well understood. Epigenetic events are involved in gene regulation and occur through different mechanisms such as DNA methylation and histone modifications. Both DNA methylation and histone modifications affect gene regulation and play important roles either independently or by interaction in tumor initiation and progression. This review will discuss the genes associated with epigenetic alterations in prostate cancer progression: their regulation and importance as possible markers for the disease.

Immunohistochemical Expression of Endothelin-1 and Endothelin-A and Endothelin-B Receptors in High-Grade Prostatic Intraepithelial Neoplasia and Prostate Cancer

OBJECTIVES

To analyze the expression of endothelin-1 (ET-1), endothelin-A receptor (ET-A-R), and endothelin-B receptor (ET-B-R) in incidental prostate cancer in cystoprostatectomies (CyPs), clinically detected hormonally untreated and hormonally treated prostate cancer in radical prostatectomies (RPs), and hormone-independent prostate cancer in transurethral resections of the prostate (TURPs). High-grade prostatic intraepithelial neoplasia (HGPIN) was also investigated.

METHODS

Nineteen CyPs and 44 RPs (25 untreated, 19 treated) with pT2a Gleason score 6 cancer and HGPIN were examined. The study included 9 TURPs with hormone-independent cancer and 8 normal cases from CyPs without prostate cancer and HGPIN. ET-1, ET-A-R, ET-B-R, and the proliferation marker Ki67 were investigated immunohistochemically.

RESULTS

The mean proportion of prostate cancer cells with strong ET-1, ET-A-R, and ET-B-R expression in CyPs was lower (18.5%, 28.0%, and 14.7%, respectively) than in the untreated group (40.7%, 39.7%, and 25.1%) and higher than in treated group (5.0%, 13.9%, and 11.3%). The highest values were in the hormone-independent cancer group (53.9%, 48.9%, 33.3%). The trend in the proportion of HGPIN cells overexpressing ET-1, ET-A-R, and ET-B-R was similar to that in the cancer groups. The values in HGPIN lesions were always slightly greater than those in the cancers. Ki67 expression in HGPIN and prostate cancer in CyPs was lower than in RPs and TURPs.

CONCLUSIONS

Our study showed for the first time that ET-1, ET-A-R, and ET-B-R expression is not limited to the late prostate cancer phases. It is also seen in HGPIN as well as in prostate cancers considered to be clinically insignificant, such as those seen in CyP specimens. Although the series of cases in each group was small, our data may have clinical significance.

Altered endothelin receptor subtypes in colorectal cancer

BACKGROUND

The vasoactive peptide endothelin-1 (ET-1) acts via two endothelin receptor subtypes, ETA (ETAR) and ETB (ETBR). ET-1 and ETAR are overexpressed in colorectal cancer tissues. In vitro, ET-1 acting via ETAR, is a mitogen for colorectal cancer cells. To identify other potential stimulatory loops, we investigated the distribution and cell-specific localization of both ETAR and ETBR in tissue sections from patients with colorectal cancer.

METHODS

Frozen sections from specimens of colorectal cancer (n=9) and normal colon (n=9) were cut and subjected to either (i) autoradiography or (ii) a combination of cell type-specific immunohistochemistry, using antibodies against fibroblasts (AS02), endothelial cells (CD31) or nerve fibres (NF200) and in-vitro receptor microautoradiography, using ETAR-specific and ETBR-specific radioligands.

RESULTS

ETARs were upregulated in all cell types, apart from nerve, in cancer compared with normal colon (1:1.59 normal to cancer). Specifically, ETAR binding was highest in cancer-associated blood vessels and fibroblasts and to a lesser extent in epithelial cancer cells. In contrast, ETBRs were the predominant receptors in normal colon (1:0.59 normal to cancer) and were markedly down-regulated in cancer-associated blood vessels, fibroblasts and to a lesser extent in epithelial cells. Nerve colocalization was demonstrated, but remained unchanged for all tissues.

CONCLUSION

The shift in ET receptor binding observed in epithelial cancer cells and cancer-associated fibroblasts and endothelial cells may favour ET-1 signals contributing to colorectal cancer growth and neovascularization via ETAR. This may provide the basis for therapeutic use of specific ETAR antagonists as adjuvant treatment of colorectal cancer.

Molecular markers for prostate cancer

Serum PSA testing has been used for over 20 years as an aid in the diagnosis and management of prostate cancer. Although highly sensitive, it suffers from a lack of specificity, showing elevated serum levels in a variety of other conditions including prostatitis, benign prostate hyperplasia, and non-cancerous neoplasia. During this period, numerous serum protein analytes have been investigated as alternative and/or supplemental tests for PSA, however in general these analytes have likewise suffered from a lack of specificity, often showing serum elevations in other clinical presentations. More recently, molecular assays targeting prostate disease at the DNA or RNA level have been investigated for potential diagnostic and prognostic utility. With the aid of modern genomics technologies, a variety of molecular biomarkers have been discovered that show potential for specific correlation with prostate cancer. Much of this discovery has been retrospective, using microdissected tissue from prostatectomy. The goal of current research is to apply genomic assays to noninvasive specimens such as blood and urine. Progress in this area is the subject of this review.

The application of epigenetic modifiers on the treatment of prostate and bladder cancer

Prostate cancer and transitional cell carcinoma (TCC) of bladder are the 2 most common malignancies in the male adult urogenital system. Epigenetic gene silencing, particularly tumor suppressor genes, has become a new area of cancer research. Agents such as deoxyribonucleic acid methyltransferase inhibitors or histone deacetylase inhibitors are epigenetic modifiers that can restore gene expression and alter the malignant phenotype of cancer. They provide a new therapeutic avenue for prostate cancer and TCC. It is also likely that combination regimens using epigenetic modifiers with other classes of agents may have higher therapeutic efficacy for prostate cancer and TCC, especially metastatic and/or refractory cases. We review current knowledge of epigenetic event in prostate cancer and TCC, and discuss the possible clinical implications for these 2 diseases.

Endothelin-1 inhibits apoptosis in prostate cancer

Endothelin-1 (ET-1), produced by the prostate epithelia, likely plays an important role in the progression of prostate cancer. ET-1 can bind two receptor subtypes; generally, binding of the endothelin receptor A (ET(A)) induces a survival pathway, whereas binding of the endothelin receptor B (ET(B)) mediates clearance of circulating ET-1 as well as promotes apoptosis. In prostate carcinoma, hypermethylation of the ET(B) promoter results in repression of ET(B) expression, thereby eliminating the negative growth response that ET-1 binding elicits through this receptor. Therefore, activation of ET(A) exclusively provides a pathway for survival advantage. Our current studies examine the mechanisms by which activation of the ET(A) may allow growth/survival. ET-1 treatment of prostate tumor cells significantly decreased paclitaxel-induced apoptosis through activation of the ET(A) subtype. The anti-apoptotic effects of ET-1 are mediated, at least in part, through the Bcl-2 family. Although no significant changes in Bcl-2 expression occurred with ET-1 treatment, the pro-apoptotic family members Bad, Bax, and Bak all decreased significantly. Further analysis of the survival pathway demonstrated that phosphorylation of Akt occurs with ET-1 treatment in a time- and dose-dependent manner through phosphatidyinositol 3-kinase activation. These data support the combination of ET(A) antagonists and apoptosis-inducing therapies for prostate cancer treatment.

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.

Angiogenesis-targeted therapies in prostate cancer

Most patients with metastatic prostate cancer will respond initially to ablation of gonadal androgen production. Eventually, all patients will develop progressive disease despite continued androgen suppression, a condition called androgen-independent or hormone-refractory prostate cancer. Hormone-refractory prostate cancer is characterized by virulent biologic and clinical behavior. Recently, docetaxel-based chemotherapy has been shown to improve survival and quality of life in this disease when compared with mitoxantrone-based therapy. However, results remain suboptimal. Recently, there have been remarkable advances in the delineation of the mechanisms of cancer growth, metastasis, and the intricate interactions between tumor cells and the surrounding normal tissues. The accumulated evidence has confirmed the importance of angiogenesis in these processes and validated the theory that inhibition of neovascularization is a promising therapeutic anticancer strategy. Currently, dozens of compounds that interfere with different steps of the angiogenic cascade are in preclinical and clinical development. Some of these agents have exhibited promising antitumor activity in hormone-refractory prostate cancer. This review summarizes the molecular mechanisms implicating angiogenesis in the development and progression of advanced-stage prostate cancer, as well as the drug development efforts that are targeting this process.

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.

The clinical application of targeting cancer through histone acetylation and hypomethylation

Methods of gene inactivation include genetic events such as mutations or deletions. Epigenetic changes, heritable traits that are mediated by changes in DNA other than nucleotide sequences, play an important role in gene expression. Two epigenetic events that have been associated with transcriptional silencing include methylation of CpG islands located in gene promoter regions of cancer cells and changes in chromatin conformation involving histone acetylation. Recent evidence demonstrates that these processes form layers of epigenetic silencing. Reversal of these epigenetic processes and up-regulation of genes important to prevent or reverse the malignant phenotype has therefore become a new therapeutic target in cancer treatment.

Endothelin receptor antagonists

Hormone refractory prostate cancer remains true to its middle name: it is largely refractory to attempts to delay its progression. New targets and new therapies are demanded. Through a review of the available literature on endothelin and several preclinical observations, the endothelin axis has emerged as one such target. In phase II and III clinical trials of atrasentan, a potent and selective endothelin receptor A subtype (ET(A)) antagonist, disease progression was delayed in some men. This well tolerated, oral agent may help convert advanced prostate cancer to a more chronic disease. This review will discuss the endothelin axis, preclinical rationale and some of the available clinical trial data on this promising new approach.

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 Detection of Prostate Cancer: A Role for GSTP1 Hypermethylation

OBJECTIVE

Prostate cancer is a leading cause of cancer-related mortality and morbidity in Western world. Curative treatment is feasible provided the disease is diagnosed in its earliest stages, but current screening methodologies are characterized by low specificity. DNA-based markers are a class of new and promising tools for cancer detection. Promoter hypermethylation is a common epigenetic alteration affecting cancer-related genes.

METHODS

We critically reviewed the most relevant reports on prostate cancer detection using DNA methylation analysis in prostate tissue and body fluids.

RESULTS

The epigenetic silencing of the glutathione-S-transferase P1 (GSTP1) gene is the most common (>90%) genetic alteration so far reported in prostate cancer. Methylation-specific PCR (MSP) methods allowed for the successful detection of GSTP1 methylation in body fluids (serum, plasma, urine, and ejaculates) from prostate cancer patients. In addition, the development of highly specific quantitative MSP assays augmented standard histopathology for the diagnosis of prostate cancer in tissue biopsies, accurately distinguishing benign from malignant prostate lesions.

CONCLUSIONS

Further advances in the epigenetic characterization of prostate cancer are likely to yield powerful tools for patient diagnosis and management.

Heterogeneous gene methylation patterns among pre-invasive and cancerous lesions of the prostate: a histopathologic study of whole mount prostate specimens

BACKGROUND

Gene methylation may contribute to prostate carcinogenesis through the silencing of gene transcription. We report on the methylation status of several genes shown to be silenced at different stages of progression using whole mount prostate specimens and laser capture microdissection. This is the first study to evaluate gene methylation patterns across multiple pre-cancerous and invasive cancer foci from the same prostate gland.

METHODS

Real-time PCR was used to evaluate methylation of five genes (GSTP1, RASSF1A, RAR beta 2, CD44, and EDNRB) across normal epithelium, high-grade prostatic intraepithelial neoplasia (HGPIN), and multiple tumor foci from each of 11 prostate cancer patients.

RESULTS

Gene methylation was not found in normal epithelium. To our knowledge, this is the first report of RASSF1A and RAR beta 2 methylation in HGPIN lesions (30% prevalence for each gene). In addition, RASSF1A, RAR beta 2, and GSTP1 methylation was highly prevalent in tumor foci (>75% for all three genes). Methylation of CD44 and EDNRB was observed in 41 and 38% of tumors but was not present in HGPIN.

CONCLUSIONS

These data suggest that genes may be methylated at different points in the histopathologic progression of prostate cancer and these differences can be found in various histologic foci from the same gland.

Hypermethylation of CpG islands in primary and metastatic human prostate cancer

Aberrant DNA methylation patterns may be the earliest somatic genome changes in prostate cancer. Using real-time methylation-specific PCR, we assessed the extent of hypermethylation at 16 CpG islands in DNA from seven prostate cancer cell lines (LNCaP, PC-3, DU-145, LAPC-4, CWR22Rv1, VCaP, and C42B), normal prostate epithelial cells, normal prostate stromal cells, 73 primary prostate cancers, 91 metastatic prostate cancers, and 25 noncancerous prostate tissues. We found that CpG islands at GSTP1, APC, RASSF1a, PTGS2, and MDR1 were hypermethylated in >85% of prostate cancers and cancer cell lines but not in normal prostate cells and tissues; CpG islands at EDNRB, ESR1, CDKN2a, and hMLH1 exhibited low to moderate rates of hypermethylation in prostate cancer tissues and cancer cell lines but were entirely unmethylated in normal tissues; and CpG islands at DAPK1, TIMP3, MGMT, CDKN2b, p14/ARF, and CDH1 were not abnormally hypermethylated in prostate cancers. Receiver operator characteristic curve analyses suggested that CpG island hypermethylation changes at GSTP1, APC, RASSF1a, PTGS2, and MDR1 in various combinations can distinguish primary prostate cancer from benign prostate tissues with sensitivities of 97.3-100% and specificities of 92-100%. Hypermethylation of the CpG island at EDNRB was correlated with the grade and stage of the primary prostate cancers. PTGS2 CpG island hypermethylation portended an increased risk of recurrence. Furthermore, CpG island hypermethylation patterns in prostate cancer metastases were very similar to the primary prostate cancers and tended to show greater differences between cases than between anatomical sites of metastasis.

A survey of gene-specific methylation in human prostate cancer among black and white men

Gene methylation is an important molecular event in prostate carcinogenesis that may have diagnostic and prognostic significance. We evaluated the methylation status of eight genes implicated in prostate carcinogenesis. DNA was extracted from archived paraffin-embedded tumor blocks from 90 prostate cancer patients. Gene methylation status of eight genes (GSTP1, RASSF1A, RARbeta2, CD44, EDNRB, E-cadherin, Annexin-2, and Caveolin-1) was determined using real-time methylation-sensitive PCR techniques. Differences in gene methylation among race, tumor grade and disease stage were evaluated by chi-square test. Of the eight genes, GSTP1, RASSF1A, and RARbeta2 methylation was highly prevalent across tumors (>60% for all three genes) whereas CD44, E-cadherin and EDNRB methylation was less prevalent (33, 24 and 29%, respectively). Annexin-2 and Caveolin-1 were not methylated in any of the tumors examined. Methylation of RARbeta2, CD44 and E-cadherin was correlated with tumor grade but not stage. Interestingly, methylation of EDNRB, a gene involved in angiogenesis, was correlated with stage of disease but not tumor grade. With the possible exception of CD44, we did not observe differences in gene methylation between racial categories for the genes under study. In summary, our data suggest that evaluation of the methylation of a panel of genes may have diagnostic and prognostic utility in prostate cancer.

The future in advanced prostate cancer: take your partners or is the last dance for me?

Recent therapeutic initiatives have improved quality of life and survival for patients with advanced prostate cancer. This review focuses predominantly on prostate cancer that has become refractory to standard androgen ablation treatment. Planned trials will answer further questions on the optimal use and sequencing of currently available hormonal agents, cytotoxic therapies, and radiolabeled nucleotides. Future therapeutic advances are likely to come in 2 areas: targeted therapies and response prediction. Molecular targeted agents will be most useful in combination with each other or with established systemic therapies. The selection of combinations will require the application of paradigms targeting key biochemical pathways and specific microenvironments in prostate cancer. Response prediction for individual patients may be assisted by either pretreatment or sequential molecular profiling, or sequential imaging, or biochemical studies that predicate outcome prior to or soon after treatment has been initiated. To bring these advances to the metastatic prostate cancer patient, a series of well-designed clinical trials is needed that integrates the lessons learned through laboratory, translational, and clinical studies in recent years.

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.

Prostate cancer biomarkers: a current perspective

Genomic- and proteomic-based studies have led to the identification of a large number of candidate biomarkers, as well as signature patterns of multiple markers for prostate cancer diagnosis, disease progression and prediction of survival. While these candidates include the usual suspects, including oncogenes, proliferation markers and cytoskeletal proteins, there are many additional unexpected molecules such as those involved in processes such as transcriptional repression and fatty acid metabolism. Patterns of expression serving as useful biomarkers is a new and, as yet, clinically untested concept which promises to permit a consideration of the complex milieu of cancer. Exciting as these developments are, clinical application will have to await careful validation of these candidates by independent biochemical approaches over large and diverse samples.