Affiliations of authors: Department of Urology, Veterans Affairs Medical Center, and University of California San Francisco, San Francisco
Correspondence to: Rajvir Dahiya, PhD, Urology Research Center (112F), Veterans Affairs Medical Center and UCSF, 4150 Clement St., San Francisco, CA 94121 (e-mail: rdahiya{at}urol.ucsf.edu)
![]() |
ABSTRACT |
---|
![]() |
INTRODUCTION |
---|
One type of epigenetic aberration is DNA methylationthe addition of a methyl group to the 5'-carbon of cytosine in CpG sequencescatalyzed by DNA methyltransferases (DNMTs). Methylcytosine residues are often found in short stretches of CpG-rich regions (i.e., CpG islands) that are 0.52 kb long and found in the 5' region of approximately 60% of genes (2). Most CpG islands are unmethylated, with the exception of certain imprinted genes and genes on the inactive X chromosomes of females (3). DNA methylation aberrations can occur as either hypo- or hypermethylation. Both forms can lead to chromosomal instability and transcriptional gene silencing, and both have been implicated in a variety of human malignancies, including prostate cancer (4).
A second type of epigenetic aberration involves chromatin structure. The basic chromatin unit is the nucleosome (5). The N-terminal tails of histones, positioned peripheral to the nucleosome core, are subject to various covalent modifications, such as acetylation, methylation, phosphorylation, and ubiquitination by specific chromatin-modifying enzymes (6). The pattern of these modifications has been referred to as "the histone code," and it acts as a second layer of epigenetic regulation of gene expression affecting chromatin structure and remodeling (7). Acetylation and deacetylation of histone tails are catalyzed by histone acetyltransferases and deacetylases (HDACs), respectively (8). Histone acetyltransferases have been shown to increase the activity of several transcription factors, including nuclear hormone receptors, by inducing histone acetylation, which facilitates promoter access to the transcriptional machinery (9). Conversely, HDACs reduce levels of histone acetylation and are associated with transcriptional repression.
These two epigenetic regulatory mechanisms, DNA methylation and histone modifications, are closely related. Successful epigenetic control of gene expression often requires the cooperation and interaction of both mechanisms, and disruption of either of those processes leads to aberrant gene expression seen in almost all human cancers. Here, we review current knowledge of the epigenetic changes in prostate cancer regarding DNA methylation and histone modifications and discuss the implication for understanding the molecular basis, clinical diagnosis, and treatment of this disease.
![]() |
DNA METHYLATION IN PROSTATE CANCER |
---|
DNA hypermethylation is the most common and best characterized epigenetic abnormality in human malignancies, including prostate cancer. By searching the Medline database using the query "prostate AND methylation" (10), 242 records were returned as of June 20, 2004, of which 52 papers reported more than 30 genes that undergo aberrant hypermethylation in prostate cancer (Table 1). These genes include classic and putative tumor-suppressor genes and genes involved in a number of cellular pathways such as hormonal responses, tumor-cell invasion and/or tumor architecture, cell cycle control, and DNA damage repair. For many of these genes, promoter hypermethylation is often the main mechanism underlying their functional loss in prostate cancer. Inappropriate silencing of these genes can contribute to cancer initiation, progression, invasion, and metastasis. Hypermethylation of these genes in prostate cancer can correlate with pathologic grade or clinical stage and with androgen independence. To assess the overall prevalence of hypermethylation of these genes in prostate cancer, we reviewed available data from the 52 publications and summarized the clinical results in Figure 1. Some frequently hypermethylated genes, such as those involved in hormone responses, cell cycle regulation, cell invasion and architecture, and tumor suppression constitute a potential prostate cancerspecific methylation signature and are discussed below.
|
|
The prostate is an endocrine gland that responds to sex hormones such as androgens, estrogens, and progesterones through their specific receptors. Epigenetic modifications such as DNA methylation and histone acetylation participate in the transcriptional regulation of steroid and thyroid nuclear receptors (11,12).
The androgen receptor (AR) mediates androgen activity, which is essential for the development of both the normal prostate and prostate cancer. Prostate cancer is initially androgen dependent, but can eventually become androgen independent after androgen deprivation therapy. Androgen-independent prostate cancers are characterized by a heterogeneous loss of AR expression (1315). Jarrard et al. (13) first reported aberrant promoter methylation in AR-negative prostate cancer cell lines. Consistent with these results, Izbicka et al. (16) showed that 5,6-dihydro-5'-azacytidine, an inhibitor of cytosine DNA methyltransferase, could restore androgen sensitivity in androgen-insensitive human prostate carcinoma cell lines, which then become sensitive to growth inhibition by antiandrogens. Furthermore, the incidence of methylation-mediated AR inactivation in prostate cancer tissue ranged from 0% to 20% in primary prostate cancers (11,1719) and from 13% to 28% in androgen-independent cancers (17,18).
Genetic alterations, including AR gene mutation (20) and amplification (21) without loss of AR expression, that alter the sensitivity of the AR to androgen are thought to play a key role in the development of androgen-independent advanced prostate cancer. However, as many as 20%30% of androgen-independent cancers do not express AR (22). The loss of AR expression in this subgroup is not associated with AR amplification. AR promoter methylation is more prevalent in androgen-independent prostate cancer than in primary androgen-dependent prostate cancer (17,18), suggesting that epigenetic silencing of AR by DNA hypermethylation could be an alternative mechanism leading to androgen independence in a subset of patients with advanced prostate cancer.
Although estrogens have been historically used for the treatment of prostate cancer, their function in the prostate remains unclear (23). The action of estrogens was thought to be mediated via a blockade of the pituitary-testicular axis (24). However, estrogens have been shown to exert direct effects on prostatic cancer cells via their own receptors (25,26).
The prostate expresses two types of estrogen receptors (ERs): ER (ESR1) and ER
(ESR2) (27). Lost or decreased expression of ESR1 and ESR2 in prostate cancer has been documented (2831). Low ESR1 expression is also associated with poor prognosis for effective endocrine therapy using estrogens (32). The ESR1 gene is frequently methylated in prostate cancer, and the methylation status is associated with tumor progression (33). The ESR2 promoter contains a typical CpG island (34). Subsequent studies from our laboratory (11,35) and others (3638) support the concept that hypermethylation is the main known mechanism responsible for inactivation of ER expression in prostate cancer. It is interesting to note that metastatic prostate cancer cells may regain ESR2 expression (27), which is accompanied by loss of ESR2 promoter methylation (37). This observation provides further evidence that ESR2 inactivation in primary prostate cancer is epigenetic by nature and thus reversible.
Cell Cycle Control Genes
An important characteristic of tumor cells is their increased proliferative ability, which is often associated with impaired regulation of the cell cycle. The cell cycle has multiple checkpoints that are controlled by a number of complex modulation systems, including the retinoblastoma (RB1) protein, cyclins, cyclin-dependent kinases (CDKs), and CDK inhibitors (CDKIs) (39). RB1 was the first tumor suppressor gene to be identified, and its alteration has been observed in many tumor types (40). RB1 inactivation resulting from promoter methylation is a common event in retinoblastomas (41,42) but a rare event in prostate cancer (43). RB1 inactivation in prostate cancer is apparently the result of loss of heterozygosity and mutation (43,44).
CDKIs are negative regulators of cell cycle progression and thus are considered to be potential tumor suppressor genes. Currently, CDKIs are grouped into two families: the INK4 family, which includes CDKN2A (p16), CDKN2B (p15), CDKN2C (p18), and CDKN2D (p19), specifically inhibits cyclin Dassociated kinases (CDKs 4 and 6); and the CIP/KIP (kinase inhibitor protein) family, which includes CDKN1A (p21), CDKN1B (p27), and CDKN1C (p57), inhibits most CDKs (45). Failure of cell cycle arrest secondary to alterations in CDKI expression has been implicated in prostate cancer (46,47). CDKN2A is inactivated by a variety of mechanisms, including deletion, point mutation, and silencing by hypermethylation in a number of cancers, including the prostate (4850). Methylation-mediated inactivation of the CDKN2A gene has been reported in prostate cancer cell lines (51,52) and prostate cancer tissue, with incidence of inactivation ranging from 0% to 16% (5256). Methylation at exon 2 of the CDKN2A gene is more frequent in prostate cancer tissue (66%) than methylation of the promoter region (56); however, exon 2 methylation does not affect gene expression (55,56) making the functional relevance of this epigenetic event unclear. However, because CDKN2A exon 2 is hypermethylated only in cancer tissues, it may serve as a biomarker to detect or confirm a prostate neoplasm. Inactivation of other cell cycle genes such as CDKN2B, CDKN1A, and CDKN1B by hypermethylation is rare in prostate cancer (56,57).
Cell Invasion and Cell Architecture Genes
The cadherincatenin adhesion system is critical to the preservation of normal tissue architecture and is regulated by a family of proteins collectively termed cell adhesion molecules. Decreased expression of E-cadherin (CDH1) and other cell adhesion molecules has been reported to have prognostic significance in various human cancers, including prostate cancer (58,59).
In human prostate tumors, expression of CDH1 is strongly reduced and its promoter is methylated to varying degrees (54,6062). The 5' CpG island of CDH1 is densely methylated in prostate cancer cell lines (63). A study of prostate cancer tissue samples from our own laboratory showed that methylation of the CDH1 promoter, as detected by bisulfite genomic sequencing of 29 CpG sites within the promoter and first exon, occurs in 30% of low-grade and 70% of high-grade prostate cancer samples and is associated with absent or reduced CDH1 protein expression, as detected by immunohistochemical analysis (60). Consistent with our data, Kallakury et al. (61) reported an 80% prevalence of CDH1 methylation in prostate cancer samples analyzed by methylation-specific polymerase chain reaction (PCR). In addition, methylation of the CDH1 promoter is increased in advanced prostate tumors, suggesting that it might be a useful biomarker to assess tumor progression (60).
There are, however, some discrepancies regarding the prevalence of CDH1 methylation in prostate cancer. Woodson et al. (64) reported that methylation of the CDH1 promoter (-159 to -51 region) could not be detected in any of 101 prostate cancer samples using real-time PCR. However, the same group (62) later reported a 22.4% prevalence of CDH1 methylation in prostate cancer using the same assay method but covering a different region (+59 to +140). Thus, different methodologies (methylation-specific polymerase chain reaction versus bisulfite genomic sequencing) and different genomic regions (promoter versus exon) examined may contribute to the observed discrepancies.
CD44 is an integral membrane protein that is involved in matrix adhesion and signal transduction. In prostate cancer, loss of CD44 protein expression is associated with methylation of its gene promoter (6469). CD44 expression and promoter methylation are associated with prostate cancer stage and patient prognosis (68,70). Other genes involved in the cadherincatenin adhesion system have also shown methylation-mediated inactivation in prostate cancer, including H-cadherin (CDH13) (71), adenomatous polyposis coli (APC) (71), caveolin-1 (CAV1) (72), laminin 3 (LAMA3), laminin
3 (LAMB3), and laminin
2 (LAMC2) (73) (Table 1).
DNA Damage Repair Genes
DNA repair is a correcting mechanism that maintains genome integrity during replication or after DNA damage. Cells defective in components of DNA repair pathways exhibit higher rates of spontaneous DNA mutations, which can lead to cancer (74). Hypermethylation of two genes involved in DNA damage repair, the detoxifier gene glutathione S-transferase Pi (GSTP1) and the DNA alkyl-repair gene O6-methylguanine DNA methyltransferase (MGMT), has been reported in prostate cancer. The glutathione S-transferase Pi gene belongs to a supergene family of glutathione S-transferases (GSTs) that play an important role in the detoxification of electrophilic compounds (such as carcinogens and cytotoxic drugs) by glutathione conjugation (75). GSTP1 inactivation may lead to increased cell vulnerability to oxidative DNA damage and to the accumulation of DNA base adducts, which can precede other relevant genetic alterations in carcinogenesis (76).
In prostate cancer, methylation of the GSTP1 gene promoter is the most frequently detected epigenetic alteration, with a frequency ranging from 70% to 100% in prostate cancer DNA specimens (7779). Notably, GSTP1 methylation is also detected in 50%70% of prostatic intraepithelial neoplasia (80,81), a precursor lesion of prostate cancer (82). Hypermethylation of the GSTP1 gene has also been detected in nonmalignant prostate tissue, but at a much lower level and frequency than in malignant tissue (19,81,83). The cancerspecific hypermethylation of the GSTP1 gene in prostate cancer cell lines and tissues provides a good model for the study of molecular mechanisms underlying methylation-mediated gene silencing and may also serve as a potential tumor biomarker for clinical detection of prostate cancer.
MGMT is a DNA repair protein that removes mutagenic and cytotoxic alkyl adducts from genomic DNA. Tumors that lack MGMT expression have a higher incidence of point mutations in the genes encoding p53 and K-ras, which may influence cancer progression (84). In addition, MGMT-deficient tumors exhibit high sensitivity to the effects of chemotherapeutic alkylating agents. Results from studies evaluating MGMT promoter methylation in prostate cancer have been equivocal, with moderate to high levels of methylation detected in some studies (54,56) but not others (19,71). Further work will be necessary to resolve this discrepancy.
Putative Tumor Suppressor Genes
Functional losses of classic tumor suppressor genes, such as the retinoblastoma-1 gene (85), the mismatch repair gene MLH1 (86), and the von HippelLindau gene (87), through DNA hypermethylation are rare in prostate cancer, although common in other types of cancer. However, some putative tumor suppressor genes have been reported to be silenced by DNA hypermethylation in prostate cancer, most notably, the Ras association domain family 1 gene (RASSF1A).
RASSF1A, located at 3p21.3, encodes a protein similar to the RAS effector proteins. The biologic activity of RASSF1 is largely unknown. Both in vitro and in vivo studies show that overexpression of RASSF1 in cancer cells leads to cell cycle arrest (88), reduced colony formation, and inhibition of tumor growth in nude mice (89). Thus, a tumor suppressor role has been proposed for RASSF1 (90,91). In prostate cancer, RASSF1 promoter methylation is a common event, occurring in 54%96% of tumor samples (54,57,62,71,90,91). RASSF1 promoter methylation is detected in some nonmalignant prostate tissue samples (71) but not in many others (54,57,62). A large percentage (64%) of prostatic intraepithelial neoplasia samples exhibit RASSF1 promoter hypermethylation (54). Increased RASSFI promoter methylation is also associated with advanced tumors (i.e., those with high Gleason scores) (54,71,90). These findings indicate that RASSF1 promoter methylation occurs in early prostate cancer development, increases as the cancer progresses, and is a potential tumor biomarker for prostate cancer diagnosis and risk assessment.
Additional genes with putative tumor suppressor function undergoing epigenetic inactivation by hypermethylation in prostate cancer include KAI1 (a prostate-specific tumor metastasis suppressor gene) (92), inhibin- (a member of the transforming growth factor
family of growth and differentiation factors) (93), and DAB2IP, a novel GTPase-activating protein for modulating the Ras-mediated signal pathway (94). It is unknown, however, whether hypermethylation of these genes plays a role in prostate carcinogenesis or has a role as a biomarker for prostate cancer diagnosis.
![]() |
HYPOMETHYLATION |
---|
There are two types of hypomethylation: global or genomic hypomethylation, which refers to an overall decrease of 5-methylcytosine content in the genome; and localized or gene-specific hypomethylation, which refers to a decrease in cytosine methylation relative to the "normal" methylation level. The latter process affects specific regions of the genome, such as the promoter regions of proto-oncogenes or normally highly methylated sequences such as repetitive sequences and oncogenes (96). Both global hypomethylation and gene-specific hypomethylation have been implicated in human cancer.
Global Hypomethylation
Net decreases in the content of methylcytosines in cancer often exceed the localized increases in DNA methylation associated with carcinogenesis (97,98). For example, in colon adenocarcinomas, the genomic 5-methylcytosine content is reduced by an average of 10% (99). Global DNA hypomethylation has also been found in the premalignant or early stages of some neoplasms (99,100) and is implicated as an important factor for tumor progression (77,101). It is unclear whether this epigenetic alteration is a cause or consequence of tumorigenesis. To add to the complexity, hypomethylation induced by disrupting DNMT1 has been found to either inhibit (102) or promote (103) tumor growth. In a murine model of intestinal neoplasia, mice carrying a germ-line mutation in the APC gene (APCMin/+) crossed with mice heterozygous for the DNMT1 mutation had substantially fewer tumors than Min mice with wild-type DNMT1 (102,104). By contrast, genomic hypomethylation has been associated with the induction of T-cell lymphomas in mice carrying a hypomorphic DNMT1 allele, which reduces DNMT1 expression to 10% of wild-type levels and results in substantial genome-wide hypomethylation in all tissues. Whether hypomethylation promotes or inhibits tumor progression might be related to differences in model systems or tissue specificity (105).
The initial findings regarding DNA methylation in the prostate came from studies by Bedford and van Helden (106) more than a decade ago. They observed that the overall 5-methylcytosine content in DNA from prostates with benign prostatic hyperplasia and metastatic tumors was significantly lower than that in DNA from nonmetastatic prostate tumors. Further studies found that global hypomethylation is associated with clinical stage (77) and metastatic state (107) of prostate cancer.
Gene-Specific Hypomethylation
Genes from cancer cells but not from normal cells are substantially hypomethylated (108). Moreover, compared with adjacent normal tissues, cancer tissues contain two hypomethylated ras oncogenes, c-Ha-ras and c-Ki-ras (109). Other examples of hypomethylated genes include the c-jun and c-MYC proto-oncogenes in liver cancer (110,111) and the pS2 gene in breast cancer (112).
Hypomethylation of a locus transcriptionally controlled by methylation may enhance transcription of associated genes (110). In the prostate, the PLAU gene is highly expressed in most prostate cancer tissues (113) and invasive prostate cancer cell lines (114). The PLAU gene encodes urokinase plasminogen activator, a multifunctional protein that can promote tumor invasion and metastasis in several malignancies including prostate cancer. Helenius et al. (114) have attributed PLAU overexpression to gene amplification, as evidenced by the two- to threefold increase in the number of copies of the gene in PC3 cells. DNA methylation may also play a role in the regulation of the PLAU gene in prostate cancer (115), with hypomethylation of the PLAU promoter being associated with its increased expression in hormone-independent prostate cancer cells, higher invasive capacity in vitro, and increased tumorigenesis in vivo (115). However, in normal prostate epithelial cells and in hormone-dependent LNCaP cells, the PLAU promoter is methylated, resulting in lower expression of the gene (115).
Other hypomethylated genes in prostate cancer include CAGE, a novel cancer/testis antigen gene (116), and heparanase. Hypomethylation of CAGE, which occurs at a frequency of approximately 40% in prostate cancers, is responsible for its exclusive expression in cancer tissues (117). Heparanase, an endo--D-glucuronidase, is highly expressed in prostate cancers. Data from our laboratory (Ogishima T, Shiina H, Igawa M, Breault JE, Terashima M, Honda S, et al., unpublished data) shows substantial hypomethylation of the heparanase gene in prostate cancer compared with benign prostatic hyperplasia samples.
There is little information regarding the paradoxical coexistence of global and regional hypo- and hypermethylation in cancer, in which DNA methyltransferase activity is generally high (33,118,119). DNA methylation has been considered as a mechanism by which tissue-specific expression of genes is regulated (120). Therefore, the gene-specific hypomethylation observed in some cancers may result from disrupted transcriptional inhibition of normally silenced tumor-promoting genes. Additionally, gene-specific hypomethylation may be associated with global hypomethylation (121) but not with gene-specific hypermethylation (122). Thus, hypo- and hypermethylation may contribute individually to the process of carcinogenesis (122).
![]() |
HISTONE MODIFICATIONS |
---|
Several genes of biologic significance to prostate cancer are potentially regulated by histone modification. One such gene, coxsackie and adenovirus receptor (CAR), is the primary receptor for group C adenoviruses and is important for adenovirus attachment to the cell membrane. Efficient adenovirus infection in gene therapy requires adequate expression of CAR in target cells. Decreased CAR gene expression has been detected in prostate cancer and is associated with an increased Gleason score (125). In urogenital cancer cells, including the prostate cancer cell line PC-3, activation of the CAR gene is modulated by histone acetylation and can be induced by depsipeptide, an HDAC inhibitor (126). Exposing cancer cells to low concentrations of depsipeptide has the functional consequence of preferentially increasing the efficiency of adenoviral transgene expression (127).
Another gene regulated by histone modification is the vitamin D receptor, via which 1,25-(OH)2-vitamin D3 acts to exert cell cycle regulatory antiproliferative effects in a variety of tumor cells, including those of the prostate (128131). However, prostate cancer cells display a range of sensitivities to the antiproliferative effects of 1,25-(OH)2-vitamin D3 (132,133) for reasons that are unclear. Prostate cancer cells that are insensitive to 1,25-(OH)2-vitamin D3 have increased levels of nuclear receptor corepressor SMRT (silencing mediator of retinoid and thyroid), which could result in increased deacetylase activity and decreased transcriptional activity of the vitamin D receptor (134). In addition, combined treatment of prostate cancer cell lines with the HDAC inhibitor trichostatin A (TSA) and 1,25-(OH)2-vitamin D3 synergistically inhibits cell proliferation (134). This finding may be useful in the clinical setting, in which use of 1,25-(OH)2-vitamin D3 and its analogs in combination with HDAC inhibitors could activate the vitamin D receptor while minimizing unwanted side effects associated with 1,25-(OH)2-vitamin D3, such as hypocalcemia.
Histones can also be modified through methylation of lysine and arginine residues (135). Methylation of H3 at lysine 4 is associated with inactive transcription of the prostate-specific antigen (PSA) gene in the prostate cancer cell line LNCaP, and AR-mediated transcription of the PSA gene was accompanied by rapid decreases in di- and trimethylated H3 at lysine 4 (136).
![]() |
INTERACTION BETWEEN DNA METHYLATION AND HISTONE MODIFICATION |
---|
DNA methylation may interact with histone methylation to modulate chromatin structure and regulate gene transcription (141,142). MeCP2, which binds to methylated CpG dinucleotides, not only recruits HDAC activity, which results in chromatin remodeling, but also facilitates methylation of H3 lysine 9 and thereby reinforces an inactive chromatin state (142). In Neurospora, histone methylation directs DNA methylation mediated by the adaptor protein, heterochromatin protein HP1 (143). This mechanism could also be operational in mammals, in which a direct interaction between DNMTs and histone methyltransferase has been observed (141,144). It is unclear which methylation event happens first; the available data support both possibilities (145,146). However, in LNCaP prostate cancer cells, transcriptional shutdown of the GSTP1 gene requires several sequential changes involving DNA methylation as the initial event, followed by histone deacetylation, and then histone methylation (147).
![]() |
EPIGENETIC CHANGES AS PROSTATE CANCER BIOMARKERS |
---|
Because GSTP1 is the most frequently methylated gene in prostate cancer, attempts have been made to detect prostate cancer by identifying methylated GSTP1 CpG islands in clinical samples, including plasma and serum (156,157), prostate secretions (158,159), voided urine (156,160162), and prostate biopsy specimens (163,164). Goessl et al. (161) examined DNA methylation of the GSTP1 gene in urine after prostatic massage and detected prostate cancer with a specificity of 98% and an overall sensitivity of 73%. In a similar study using urine samples collected after biopsy (162), the specificity was only 67% and the sensitivity only 58%. Specificity and sensitivity were even lower if simple voided urine was used as the DNA source (160).
In a recent study, Harden et al. (165) compared the results of a blinded histologic review of sextant biopsy samples from 72 excised prostates with the relative methylation levels of GSTP1 (i.e., a relative methylation level is the ratio of GSTP1 to the level a reference gene, MYOD1). They found that histologic analysis alone detected prostate carcinoma with a sensitivity of 64% and a specificity of 100%, whereas the combination of histologic analysis and GSTP1 methylation at an assay threshold (i.e., a cut-off level for the GSTP1/MYOD1 ratio) of greater than 10 detected prostate carcinoma with a sensitivity of 75% and a specificity of 100%.
GSTP1 methylation can also be used to detect occult prostate cancer cells in lymph nodes. Kollermann et al. (166) found evidence of GSTP1 hypermethylation in 90% of lymph nodes from prostate cancer patients but in only 11.1% of lymph nodes from a noncancer cohort, suggesting that detection of GSTP1 methylation could have a role in molecular staging of prostate cancer. CD44 may have a similar role. However, although CD44 hypermethylation is readily detectable in the serum of prostate cancer patients, there is a lack of specificity for the disease because CD44 is also found in normal epithelial specimens (67).
Using the methylation status of a single gene as a biomarker of prostate cancer has limitations, including insufficient sensitivity, lack of specificity in differentiating prostate cancer from nonmalignant disease and from cancers originating from other organs, and poor risk assessment. An examination of the methylation pattern of multiple genes may overcome these limitations and offer better diagnostic and prognostic possibilities than that of a single gene. By profiling the methylation pattern of multiple genes in prostate tissue, several recent studies (54,57) have shown improved sensitivity and specificity in detecting prostate cancer. For example, examining the methylation of GSTP1, APC, RASSF1, and MDR1 can distinguish primary prostate cancer from benign prostate tissues, with sensitivities of 97%100% and specificities of 92%100% (57). Similar methylation patterns were observed in studies conducted with Korean prostate cancer patients (54) and Western patients (57). The prevalence of hypermethylation for three of four genes (GSTP1, RASSF1A, APC, and MGMT) studied in both populations was similar (54,57), indicating the existence of a unique prostate cancer-specific methylation fingerprint that is not defined by race/ethnicity.
For methylation profiling of multiple genes to be a clinically practical tumor marker, these results need to be validated in clinical specimens of prostate cancer patients. In addition, although most current studies focus on candidate gene approaches, there is an urgent need to perform genome-wide screening of unknown methylated loci in prostate cancer and add these loci to the pool of known methylated genes for methylation profiling. Microchips spotted with five to 10 genes representing the best prostate cancer methylation fingerprints may make the rapid, accurate diagnosis and risk assessment of patients with prostate cancer possible.
Another potentially useful application of methylation profiles is in the molecular classification of prostate cancer. The current prostate cancer classification system depends largely on histopathologic observations that are unable to predict whether a latent tumor will progress to a clinically relevant tumor or whether it will respond to androgen ablation treatment. Classification based on methylation profiles alone or in combination with pathologic diagnosis could be useful in predicting the behavior of a tumor. Attempts have been made to use both quantitative methylation analysis of the GSTP1 gene and a histologic review in the diagnosis of prostatic sextant biopsies. Using these techniques, improved sensitivity and specificity were noted (164).
![]() |
EPIGENETIC MODULATORS FOR PROSTATE CANCER TREATMENT |
---|
Unlike genetic alterations such as mutations, epigenetic changes such as DNA methylation are potentially reversible. This property makes epigenetic changes an attractive target for cancer therapy (97). 5-Azacytidine and 5-aza-deoxycytidine (decitabine), nucleoside analog inhibitors of DNMTs, have been widely used in in vitro cell culture systems to reverse abnormal DNA hypermethylation and restore silenced gene expression. However, only limited success has been achieved in clinical trials with these drugs (167,168). In a phase II study conducted by Thibault et al. (168), 14 men with progressive, metastatic prostate cancer that recurred after total androgen blockade and flutamide withdrawal were treated with decitabine, but only 2 of 12 patients evaluated for response had stable disease, with delayed time to progression. The authors concluded that decitabine is a well-tolerated regimen with modest clinical activity against hormone-independent prostate cancer.
Because nucleoside analog inhibitors of DNMTs have many potential side effects, such as myelotoxicity (169), mutagenesis (170), and tumorigenesis (171), non-nucleoside analog DNA methyltransferase inhibitors are an attractive alternative for possible clinical use. Lin et al. (172) reported that procainamide, a widely used antiarrhythmia drug and a known non-nucleoside inhibitor of DNMTs, reversed GSTP1 CpG island hypermethylation and restored GSTP1 expression in LNCaP cells grown in vitro or in vivo as xenograft tumors in athymic nude mice. Procainamide also restored expression of several other genes silenced by promoter methylation (173,174). The demethylating effect of procainamide is thought to occur through inhibition of DNMT-catalyzed transfer of methyl groups from S-adenosylmethionine to DNA (175). It is likely that additional compounds with a weak demethylating effect such as those existing in various dietary plants will be identified (176).
Although demethylating agents may protect against some cancers (102), they may also promote genomic instability and increase the risk of cancer in other tissues (103). Indeed, hypomethylation can have hazardous effects such as promoting carcinogenesis as demonstrated in certain model systems (103). Therefore, caution should be used in selecting the type of cancer patient for clinical trials involving DNA methyltransferase inhibitors. It is also important to note that the effects of DNMT inhibitors and even the effects of knocking down DNMT1 per se may be independent of the mechanisms of epigenetic reactivation such as DNA demethylation and histone hypermethylation (177). Therefore, it is possible that many of the antiproliferative effects seen in either normal or cancer cells may be attributed to methylation-independent roles of DNMT1 rather than the loss of DNA methylation.
Reversal of Hypomethylation for the Suppression of Overexpressed Genes
Gene transcription from a transfected plasmid DNA can be suppressed by in vitro DNA methylation of the upstream promoter by using SssI methylase (178,179). Recently, a new class of oligonucleotide termed methylated sense oligonucleotide has been used to manipulate sequence-specific DNA methylation in vitro and in vivo (37,180). This technique uses a synthetic oligonucleotide in which the cytosine residues are replaced by 5'-methylcytosine. Binding of the methylated sense oligonucleotide to one strand of the DNA forms a hemimethylated DNA intermediate that has a "replication fork"like structure and is a preferred substrate of DNMTs. The latter DNMTs would methylate the second strand and spread the methylation around the targeted site (180).
Unlike DNMT inhibitors, this innovative approach changes only the epigenetics in a gene-specific manner and could be potentially powerful in suppressing hypomethylated and thus overexpressed tumor-promoting genes by introducing de novo methylation in their promoter. In this regard, introduction of a methylated sense oligonucleotide that targets the ESR2 gene promoter into PC-3 prostate cancer cells results in sequence-specific methylation and the suppression of ESR2 gene expression, which is overexpressed in metastatic prostate cancer because of a hypomethylated promoter (36). In an in vivo study of mice with implanted hepatocellular carcinoma, injection of a methylated sense oligonucleotide targeting the insulin-like growth factor 2 gene led to improved survival (180). However, before this technique can be tested as a human therapy, its efficacy in achieving sustained inhibition of gene expression needs to be compared with that of other posttranscriptional and posttranslation gene silencing approaches such as RNA interference.
HDAC Inhibitors for Activating Transcriptionally Silenced Genes
HDAC complexes enzymatically remove the acetyl group from lysine residues of the amino-terminal tails of histones maintaining chromatin in a transcriptionally inactive state (181). This transcriptional blockade can be overcome by agents that inhibit HDACs (8). A variety of agents, many of which are natural products, exhibit HDAC inhibitory activity and therefore may have antitumor activity. Commonly used HDAC inhibitors include TSA (182), sodium butyrate (182), depsipeptide (FR901228 and FK228) (183), valproic acid (184), MS-275 (185), suberoylanilide hydroxamic acid (SAHA) (186), pyroxamide (186), and phenylbutyrate (187). Some of these agents such as depsipeptide are in clinical trials. A comprehensive review of various HDAC inhibitors in cancer treatment has been published recently (188).
A number of in vitro studies have used the antiproliferative effects of various HDAC inhibitors in cultured human prostate cancer cells. All of the agents tested have inhibitory activity against prostate cancer cell growth (186,187), but the underlying mechanism varies widely. For example, sodium butyrate and TSA synergize with 1,25-(OH)2-vitamin D3 to inhibit the growth of LNCaP, PC-3, and DU-145 prostate cancer cells by inducing apoptosis (12). Valproic acid induces prostate cancer cell apoptosis by increasing the expression of several pro-apoptotic genes (184). Although the study did not address whether there were locus-specific histone acetylation changes, a marked global decrease in nuclear HDAC activity was noticed in valproic acidtreated cells (184). Other growth inhibitory mechanisms have also been identified, such as increasing expression of the cell cycle regulator CDKN1A (186,189), decreasing telomerase activity (182), and suppressing angiogenic factors, such as vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (183). The observed decrease in histone deacetylating activity induced by HDAC inhibitors is mainly related to the induction of gene transcription. In several instances, however, HDAC inhibitors may actually decrease expression of hyperacetylated genes (182,183). In particular, depsipeptide inhibits PC-3 cell growth by suppressing the expression of VEGF mRNA even though it induces accumulation of acetylated histones in chromatin associated with the VEGF gene promoter (183). It is unclear why accumulation of acetylated histones in the VEGF gene promoter causes transcriptional inhibition of the associated gene.
Several HDAC inhibitors have also been tested in animal models of prostate cancer and have had promising antitumor activity (183,186,190,191). SAHA, at a dose without detectable toxicity, reduced tumor growth by 97% in mice transplanted with CWR222 human prostate tumors (190). Similarly, depsipeptide, sodium butyrate, and tributyrin slowed prostate cancer tumor growth by 50%98%, depending on the cell line used for establishing xenografts in mice (189,191).
Combined Action of DNA Methyltransferase Inhibitors and HDAC Inhibitors
It is unlikely that a single agent has the potential to reverse epigenetic silencing of genes once and for all without inducing adverse effects related to cytotoxicity or undesired epigenetic effects. Emerging evidence supports the concept that epigenetic silencing of genes involves multiple mechanisms including DNA methylation, histone methylation and acetylation, and chromatin remodeling and requires their sequential action (147). Several studies have shown that the combination of HDAC and DNMT inhibitors can generate additive or synergistic effects on apoptosis, differentiation, and/or cell growth arrest in cancer cells (192194). HDAC inhibitors such as TSA can potentiate the induction of tumor suppressor genes by DNA-demethylating agents in cancer cells (194). To maximally achieve gene reactivation, it may be necessary to simultaneously block the processes essential to both the formation and maintenance of the transcriptionally repressive chromatin associated with such genes (94).
![]() |
CONCLUSIONS AND FUTURE DIRECTIONS |
---|
Ample evidence suggests that DNA methylation detection can serve as a promising tumor biomarker. However in the prostate, only the GSTP1 gene shows sufficient specificity and sensitivity in detecting prostate cancer to warrant further testing as a tumor marker in patients body fluids such as serum, urine, and ejaculate. Further work should also focus on identifying new aberrantly methylated genes using high-throughput screening such as CpG island microarray assays as the first step toward tumor marker validation. Furthermore, a prostate cancer methylation fingerprint comprising multiple genes may be more accurate than that of individual genes in the early detection and risk assessment of prostate cancer and molecular diagnosis of resected specimens.
Before we fully understand the cause and consequence of global hypomethylation in prostate cancer, therapeutics targeting DNMTs in cancer should be used with caution. Ideal treatments are those that can selectively activate a group of methylated genes without inducing undesired demethylation to the rest of the genome. Given the close relationship between DNA methylation and histone deacetylation in epigenetic inactivation, a combination of DNMT inhibitors and histone deacetylation inhibitors may be an attractive strategy for the treatment of prostate cancer patients.
![]() |
NOTES |
---|
We thank Dr. Roger Erickson for his editorial assistance.
![]() |
REFERENCES |
---|
1 Wolffe AP, Matzke MA. Epigenetics: regulation through repression. Science 1999;286:4816.
2 Gardiner-Garden M, Frommer M. CpG islands in vertebrate genomes. J Mol Biol 1987;196:26182.[ISI][Medline]
3 Bird AP. CpG-rich islands and the function of DNA methylation. Nature 1986;321:20913.[ISI][Medline]
4 Baylin SB, Makos M, Wu JJ, Yen RW, de Bustros A, Vertino P, et al. Abnormal patterns of DNA methylation in human neoplasia: potential consequences for tumor progression. Cancer Cells 1991;3:38390.[ISI][Medline]
5 Felsenfeld G, Groudine M. Controlling the double helix. Nature 2003;421:44853.[CrossRef][ISI][Medline]
6 Zhang Y, Reinberg D. Transcription regulation by histone methylation: interplay between different covalent modifications of the core histone tails. Genes Dev 2001;15:234360.
7 Jenuwein T, Allis CD. Translating the histone code. Science 2001;293:107480.
8 Marks PA, Rifkind RA, Richon VM, Breslow R. Inhibitors of histone deacetylase are potentially effective anticancer agents. Clin Cancer Res 2001;7:75960.
9 Xu W, Cho H, Evans RM. Acetylation and methylation in nuclear receptor gene activation. Methods Enzymol 2003;364:20523.[ISI][Medline]
10 Li LC, Zhao H, Shiina H, Kane CJ, Dahiya R. PGDB: a curated and integrated database of genes related to the prostate. Nucleic Acids Res 2003;31:2913.
11 Sasaki M, Tanaka Y, Perinchery G, Dharia A, Kotcherguina I, Fujimoto S, et al. Methylation and inactivation of estrogen, progesterone, and androgen receptors in prostate cancer. J Natl Cancer Inst 2002;94:38490.
12 Rashid SF, Moore JS, Walker E, Driver PM, Engel J, Edwards CE, et al. Synergistic growth inhibition of prostate cancer cells by 1 ,25 dihydroxyvitamin D3 and its 19-nor-hexafluoride analogs in combination with either sodium butyrate or trichostatin A. Oncogene 2001;20:186072.[CrossRef][ISI][Medline]
13 Jarrard DF, Kinoshita H, Shi Y, Sandefur C, Hoff D, Meisner LF, et al. Methylation of the androgen receptor promoter CpG island is associated with loss of androgen receptor expression in prostate cancer cells. Cancer Res 1998;58:53104.[Abstract]
14 Suzuki H, Ito H. Role of androgen receptor in prostate cancer. Asian J Androl 1999;1:815.[Medline]
15 Chlenski A, Nakashiro K, Ketels KV, Korovaitseva GI, Oyasu R. Androgen receptor expression in androgen-independent prostate cancer cell lines. Prostate 2001;47:6675.[CrossRef][ISI][Medline]
16 Izbicka E, MacDonald JR, Davidson K, Lawrence RA, Gomez L, Von Hoff DD. 5,6 Dihydro-5'-azacytidine (DHAC) restores androgen responsiveness in androgen-insensitive prostate cancer cells. Anticancer Res 1999;19:128591.[ISI][Medline]
17 Kinoshita H, Shi Y, Sandefur C, Meisner LF, Chang C, Choon A, et al. Methylation of the androgen receptor minimal promoter silences transcription in human prostate cancer. Cancer Res 2000;60:362330.
18 Nakayama T, Watanabe M, Suzuki H, Toyota M, Sekita N, Hirokawa Y, et al. Epigenetic regulation of androgen receptor gene expression in human prostate cancers. Lab Invest 2000;80:178996.[ISI][Medline]
19 Yamanaka M, Watanabe M, Yamada Y, Takagi A, Murata T, Takahashi H, et al. Altered methylation of multiple genes in carcinogenesis of the prostate. Int J Cancer 2003;106:3827.[CrossRef][ISI][Medline]
20 Newmark JR, Hardy DO, Tonb DC, Carter BS, Epstein JI, Isaacs WB, et al. Androgen receptor gene mutations in human prostate cancer. Proc Natl Acad Sci U S A 1992;89:631923.
21 Visakorpi T, Hyytinen E, Koivisto P, Tanner M, Keinanen R, Palmberg C, et al. In vivo amplification of the androgen receptor gene and progression of human prostate cancer. Nat Genet 1995;9:4016.[ISI][Medline]
22 Hobisch A, Culig Z, Radmayr C, Bartsch G, Klocker H, Hittmair A. Androgen receptor status of lymph node metastases from prostate cancer. Prostate 1996;28:12935.[CrossRef][ISI][Medline]
23 Huggins C. Two principles in endocrine therapy of cancers: hormone deprival and hormone interference. Cancer Res 1965;25:11637.[ISI][Medline]
24 Paulson DF. Management of metastatic prostatic cancer. Urology 1985;25(2 suppl):4952.[CrossRef]
25 Castagnetta LA, Carruba G. Human prostate cancer: a direct role for oestrogens. Ciba Found Symp 1995;191:26986; discussion 2869.[ISI][Medline]
26 Jarred RA, McPherson SJ, Bianco JJ, Couse JF, Korach KS, Risbridger GP. Prostate phenotypes in estrogen-modulated transgenic mice. Trends Endocrinol Metab 2002;13:1638.[CrossRef][ISI][Medline]
27 Leav I, Lau KM, Adams JY, McNeal JE, Taplin ME, Wang J, et al. Comparative studies of the estrogen receptors and
and the androgen receptor in normal human prostate glands, dysplasia, and in primary and metastatic carcinoma. [comment in: Am J Pathol 2001; 159:136]. Am J Pathol 2001;159:7992.
28 Brolin J, Skoog L, Ekman P. Immunohistochemistry and biochemistry in detection of androgen, progesterone, and estrogen receptors in benign and malignant human prostatic tissue. Prostate 1992;20:28195.[ISI][Medline]
29 Hobisch A, Hittmair A, Daxenbichler G, Wille S, Radmayr C, Hobisch-Hagen P, et al. Metastatic lesions from prostate cancer do not express oestrogen and progesterone receptors [see comments]. J Pathol 1997;182:35661.[CrossRef][ISI][Medline]
30 Horvath LG, Henshall SM, Lee CS, Head DR, Quinn DI, Makela S, et al. Frequent loss of estrogen receptor- expression in prostate cancer. Cancer Res 2001;61:53315.
31 Pasquali D, Rossi V, Esposito D, Abbondanza C, Puca GA, Bellastella A, et al. Loss of estrogen receptor beta expression in malignant human prostate cells in primary cultures and in prostate cancer tissues. J Clin Endocrinol Metab 2001;86:20515.
32 Konishi N, Nakaoka S, Hiasa Y, Kitahori Y, Ohshima M, Samma S, et al. Immunohistochemical evaluation of estrogen receptor status in benign prostatic hypertrophy and in prostate carcinoma and the relationship to efficacy of endocrine therapy. Oncology 1993;50:25963.[ISI][Medline]
33 Li LC, Chui R, Nakajima K, Oh BR, Au HC, Dahiya R. Frequent methylation of estrogen receptor in prostate cancer: correlation with tumor progression. Cancer Res 2000;60:7026.
34 Li LC, Yeh CC, Nojima D, Dahiya R. Cloning and characterization of human estrogen receptor promoter. Biochem Biophys Res Commun 2000;275:6829.[CrossRef][ISI][Medline]
35 Nojima D, Li LC, Dharia A, Perinchery G, Ribeiro-Filho L, Yen TS, et al. CpG hypermethylation of the promoter region inactivates the estrogen receptor- gene in patients with prostate carcinoma. Cancer 2001;92:207683.[CrossRef][ISI][Medline]
36 Lau KM, LaSpina M, Long J, Ho SM. Expression of estrogen receptor (ER)- and ER-
in normal and malignant prostatic epithelial cells: regulation by methylation and involvement in growth regulation. Cancer Res 2000;60:317582.
37 Zhu X, Leav I, Leung YK, Wu M, Liu Q, Gao Y, et al. Dynamic regulation of estrogen receptor- expression by DNA methylation during prostate cancer development and metastasis. Am J Pathol 2004;164:200312.
38 Zhang J, Liu L, Pfeifer GP. Methylation of the retinoid response gene TIG1 in prostate cancer correlates with methylation of the retinoic acid receptor gene. Oncogene 2004;23:22419.[CrossRef][ISI][Medline]
39 Fernandez PL, Jares P, Rey MJ, Campo E, Cardesa A. Cell cycle regulators and their abnormalities in breast cancer. Mol Pathol 1998;51:3059.[Abstract]
40 Lee WH, Bookstein R, Hong F, Young LJ, Shew JY, Lee EY. Human retinoblastoma susceptibility gene: cloning, identification, and sequence. Science 1987;235:13949.[ISI][Medline]
41 Sakai T, Toguchida J, Ohtani N, Yandell DW, Rapaport JM, Dryja TP. Allele-specific hypermethylation of the retinoblastoma tumor-suppressor gene. Am J Hum Genet 1991;48:8808.[ISI][Medline]
42 Stirzaker C, Millar DS, Paul CL, Warnecke PM, Harrison J, Vincent PC, et al. Extensive DNA methylation spanning the Rb promoter in retinoblastoma tumors. Cancer Res 1997;57:222937.[Abstract]
43 Konishi N, Nakamura M, Kishi M, Nishimine M, Ishida E, Shimada K. Heterogeneous methylation and deletion patterns of the INK4a/ARF locus within prostate carcinomas. Am J Pathol 2002;160:120714.
44 Kubota Y, Fujinami K, Uemura H, Dobashi Y, Miyamoto H, Iwasaki Y, et al. Retinoblastoma gene mutations in primary human prostate cancer. Prostate 1995;27:31420.[ISI][Medline]
45 Sherr CJ, Roberts JM. Inhibitors of mammalian G1 cyclin-dependent kinases. Genes Dev 1995;9:114963.[CrossRef][ISI][Medline]
46 Aaltomaa S, Lipponen P, Eskelinen M, Ala-Opas M, Kosma VM. Prognostic value and expression of p21(waf1/cip1) protein in prostate cancer. Prostate 1999;39:815.[CrossRef][ISI][Medline]
47 Cote RJ, Shi Y, Groshen S, Feng AC, Cordon-Cardo C, Skinner D, et al. Association of p27Kip1 levels with recurrence and survival in patients with stage C prostate carcinoma. J Natl Cancer Inst 1998;90:91620.
48 Cairns P, Polascik TJ, Eby Y, Tokino K, Califano J, Merlo A, et al. Frequency of homozygous deletion at p16/CDKN2 in primary human tumours. Nat Genet 1995;11:2102.[ISI][Medline]
49 Koh J, Enders GH, Dynlacht BD, Harlow E. Tumour-derived p16 alleles encoding proteins defective in cell-cycle inhibition. Nature 1995;375:50610.[CrossRef][ISI][Medline]
50 Otterson GA, Khleif SN, Chen W, Coxon AB, Kaye FJ. CDKN2 gene silencing in lung cancer by DNA hypermethylation and kinetics of p16INK4 protein induction by 5-aza 2'deoxycytidine. Oncogene 1995;11:12116.[ISI][Medline]
51 Herman JG, Merlo A, Mao L, Lapidus RG, Issa JP, Davidson NE, et al. Inactivation of the CDKN2/p16/MTS1 gene is frequently associated with aberrant DNA methylation in all common human cancers. Cancer Res 1995;55:452530.[Abstract]
52 Jarrard DF, Bova GS, Ewing CM, Pin SS, Nguyen SH, Baylin SB, et al. Deletional, mutational, and methylation analyses of CDKN2 (p16/MTS1) in primary and metastatic prostate cancer. Genes Chromosomes Cancer 1997;19:906.[CrossRef][ISI][Medline]
53 Gu K, Mes-Masson AM, Gauthier J, Saad F. Analysis of the p16 tumor suppressor gene in early-stage prostate cancer. Mol Carcinog 1998;21:16470.[CrossRef][ISI][Medline]
54 Kang GH, Lee S, Lee HJ, Hwang KS. Aberrant CpG island hypermethylation of multiple genes in prostate cancer and prostatic intraepithelial neoplasia. J Pathol 2004;202:23340.[CrossRef][ISI][Medline]
55 Nguyen TT, Nguyen CT, Gonzales FA, Nichols PW, Yu MC, Jones PA. Analysis of cyclin-dependent kinase inhibitor expression and methylation patterns in human prostate cancers. Prostate 2000;43:23342.[CrossRef][ISI][Medline]
56 Konishi N, Nakamura M, Kishi M, Nishimine M, Ishida E, Shimada K. DNA hypermethylation status of multiple genes in prostate adenocarcinomas. Jpn J Cancer Res 2002;93:76773.[ISI][Medline]
57 Yegnasubramanian S, Kowalski J, Gonzalgo ML, Zahurak M, Piantadosi S, Walsh PC, et al. Hypermethylation of CpG islands in primary and metastatic human prostate cancer. Cancer Res 2004;64:197586.
58 Ross JS, Figge HL, Bui HX, del Rosario AD, Fisher HA, Nazeer T, et al. E-cadherin expression in prostatic carcinoma biopsies: correlation with tumor grade, DNA content, pathologic stage, and clinical outcome. Mod Pathol 1994;7:83541.[ISI][Medline]
59 Richmond PJ, Karayiannakis AJ, Nagafuchi A, Kaisary AV, Pignatelli M. Aberrant E-cadherin and -catenin expression in prostate cancer: correlation with patient survival. Cancer Res 1997;57:318993.[Abstract]
60 Li LC, Zhao H, Nakajima K, Oh BR, Filho LA, Carroll P, et al. Methylation of the E-cadherin gene promoter correlates with progression of prostate cancer. J Urol 2001;166:7059.[ISI][Medline]
61 Kallakury BV, Sheehan CE, Winn-Deen E, Oliver J, Fisher HA, Kaufman RP, Jr., et al. Decreased expression of catenins ( and
), p120 CTN, and E-cadherin cell adhesion proteins and E-cadherin gene promoter methylation in prostatic adenocarcinomas. Cancer 2001;92:278695.[CrossRef][ISI][Medline]
62 Woodson K, Hanson J, Tangrea J. A survey of gene-specific methylation in human prostate cancer among black and white men. Cancer Lett 2004;205:1818.[CrossRef][ISI][Medline]
63 Graff JR, Herman JG, Lapidus RG, Chopra H, Xu R, Jarrard DF, et al. E-cadherin expression is silenced by DNA hypermethylation in human breast and prostate carcinomas. Cancer Res 1995;55:51959.[Abstract]
64 Woodson K, Hayes R, Wideroff L, Villaruz L, Tangrea J. Hypermethylation of GSTP1, CD44, and E-cadherin genes in prostate cancer among US blacks and whites. Prostate 2003;55:199205.[CrossRef][ISI][Medline]
65 Verkaik NS, Trapman J, Romijn JC, Van der Kwast TH, Van Steenbrugge GJ. Down-regulation of CD44 expression in human prostatic carcinoma cell lines is correlated with DNA hypermethylation. Int J Cancer 1999;80:43943.[ISI][Medline]
66 Verkaik NS, van Steenbrugge GJ, van Weerden WM, Bussemakers MJ, van der Kwast TH. Silencing of CD44 expression in prostate cancer by hypermethylation of the CD44 promoter region. Lab Invest 2000;80:12918.[ISI][Medline]
67 Vis AN, Oomen M, Schroder FH, van der Kwast TH. Feasibility of assessment of promoter methylation of the CD44 gene in serum of prostate cancer patients. Mol Urol 2001;5:199203.[CrossRef][ISI][Medline]
68 Kito H, Suzuki H, Ichikawa T, Sekita N, Kamiya N, Akakura K, et al. Hypermethylation of the CD44 gene is associated with progression and metastasis of human prostate cancer. Prostate 2001;49:1105.[CrossRef][ISI][Medline]
69 Lou W, Krill D, Dhir R, Becich MJ, Dong JT, Frierson HF Jr, et al. Methylation of the CD44 metastasis suppressor gene in human prostate cancer. Cancer Res 1999;59:232931.
70 Noordzij MA, van Steenbrugge GJ, Verkaik NS, Schroder FH, van der Kwast TH. The prognostic value of CD44 isoforms in prostate cancer patients treated by radical prostatectomy. Clin Cancer Res 1997;3:80515.[Abstract]
71 Maruyama R, Toyooka S, Toyooka KO, Virmani AK, Zochbauer-Muller S, Farinas AJ, et al. Aberrant promoter methylation profile of prostate cancers and its relationship to clinicopathological features. Clin Cancer Res 2002;8:5149.
72 Cui J, Rohr LR, Swanson G, Speights VO, Maxwell T, Brothman AR. Hypermethylation of the caveolin-1 gene promoter in prostate cancer. Prostate 2001;46:24956.[CrossRef][ISI][Medline]
73 Sathyanarayana UG, Padar A, Suzuki M, Maruyama R, Shigematsu H, Hsieh JT, et al. Aberrant promoter methylation of laminin-5-encoding genes in prostate cancers and its relationship to clinicopathological features. Clin Cancer Res 2003;9:6395400.
74 Schofield MJ, Hsieh P. DNA mismatch repair: molecular mechanisms and biological function. Annu Rev Microbiol 2003;57:579608.[CrossRef][ISI][Medline]
75 Henderson CJ, McLaren AW, Moffat GJ, Bacon EJ, Wolf CR. Pi-class glutathione S-transferase: regulation and function. Chem Biol Interact 1998;111112:6982.
76 Nelson CP, Kidd LC, Sauvageot J, Isaacs WB, De Marzo AM, Groopman JD, et al. Protection against 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine cytotoxicity and DNA adduct formation in human prostate by glutathione S-transferase P1. Cancer Res 2001;61:1039.
77 Santourlidis S, Florl A, Ackermann R, Wirtz HC, Schulz WA. High frequency of alterations in DNA methylation in adenocarcinoma of the prostate. Prostate 1999;39:16674.[CrossRef][ISI][Medline]
78 Lee WH, Isaacs WB, Bova GS, Nelson WG. CG island methylation changes near the GSTP1 gene in prostatic carcinoma cells detected using the polymerase chain reaction: a new prostate cancer biomarker. Cancer Epidemiol Biomarkers Prev 1997;6:44350.[Abstract]
79 Lee WH, Morton RA, Epstein JI, Brooks JD, Campbell PA, Bova GS, et al. Cytidine methylation of regulatory sequences near the pi-class glutathione S-transferase gene accompanies human prostatic carcinogenesis. Proc Natl Acad Sci U S A 1994;91:117337.
80 Brooks JD, Weinstein M, Lin X, Sun Y, Pin SS, Bova GS, et al. CG island methylation changes near the GSTP1 gene in prostatic intraepithelial neoplasia. Cancer Epidemiol Biomarkers Prev 1998;7:5316.[Abstract]
81 Jeronimo C, Usadel H, Henrique R, Oliveira J, Lopes C, Nelson WG, et al. Quantitation of GSTP1 methylation in non-neoplastic prostatic tissue and organ-confined prostate adenocarcinoma. J Natl Cancer Inst 2001;93:174752.
82 Goeman L, Joniau S, Ponette D, Van Der Aa F, Roskams T, Oyen R, et al. Is low-grade prostatic intraepithelial neoplasia a risk factor for cancer? Prostate Cancer Prostatic Dis 2003;6:30510.[CrossRef][ISI][Medline]
83 Jeronimo C, Varzim G, Henrique R, Oliveira J, Bento MJ, Silva C, et al. I105V polymorphism and promoter methylation of the GSTP1 gene in prostate adenocarcinoma. Cancer Epidemiol Biomarkers Prev 2002;11:44550.
84 Esteller M, Herman JG. Generating mutations but providing chemosensitivity: the role of O6-methylguanine DNA methyltransferase in human cancer. Oncogene 2004;23:18.[CrossRef][ISI][Medline]
85 Greger V, Debus N, Lohmann D, Hopping W, Passarge E, Horsthemke B. Frequency and parental origin of hypermethylated RB1 alleles in retinoblastoma. Hum Genet 1994;94:4916.[ISI][Medline]
86 Veigl ML, Kasturi L, Olechnowicz J, Ma AH, Lutterbaugh JD, Periyasamy S, et al. Biallelic inactivation of hMLH1 by epigenetic gene silencing, a novel mechanism causing human MSI cancers. Proc Natl Acad Sci U S A 1998;95:8698702.
87 Herman JG, Latif F, Weng Y, Lerman MI, Zbar B, Liu S, et al. Silencing of the VHL tumor-suppressor gene by DNA methylation in renal carcinoma. Proc Natl Acad Sci U S A 1994;91:97004.[Abstract]
88 Song MS, Song SJ, Ayad NG, Chang JS, Lee JH, Hong HK, et al. The tumour suppressor RASSF1A regulates mitosis by inhibiting the APC-Cdc20 complex. Nat Cell Biol 2004;6:12937.[CrossRef][ISI][Medline]
89 Burbee DG, Forgacs E, Zochbauer-Muller S, Shivakumar L, Fong K, Gao B, et al. Epigenetic inactivation of RASSF1A in lung and breast cancers and malignant phenotype suppression. J Natl Cancer Inst 2001;93:6919.
90 Liu L, Yoon JH, Dammann R, Pfeifer GP. Frequent hypermethylation of the RASSF1A gene in prostate cancer. Oncogene 2002;21:683540.[CrossRef][ISI][Medline]
91 Kuzmin I, Gillespie JW, Protopopov A, Geil L, Dreijerink K, Yang Y, et al. The RASSF1A tumor suppressor gene is inactivated in prostate tumors and suppresses growth of prostate carcinoma cells. Cancer Res 2002;62:3498502.
92 Sekita N, Suzuki H, Ichikawa T, Kito H, Akakura K, Igarashi T, et al. Epigenetic regulation of the KAI1 metastasis suppressor gene in human prostate cancer cell lines. Jpn J Cancer Res 2001;92:94751.[ISI][Medline]
93 Schmitt JF, Millar DS, Pedersen JS, Clark SL, Venter DJ, Frydenberg M, et al. Hypermethylation of the inhibin -subunit gene in prostate carcinoma. Mol Endocrinol 2002;16:21320.
94 Chen H, Toyooka S, Gazdar AF, Hsieh JT. Epigenetic regulation of a novel tumor suppressor gene (hDAB2IP) in prostate cancer cell lines. J Biol Chem 2003;278:312130.
95 Urnov FD. Methylation and the genome: the power of a small amendment. J Nutr 2002;132:2450S6S.
96 Dunn BK. Hypomethylation: one side of a larger picture. Ann N Y Acad Sci 2003;983:2842.
97 Baylin SB, Belinsky SA, Herman JG. Aberrant methylation of gene promoters in cancerconcepts, misconcepts, and promise. J Natl Cancer Inst 2000;92:14601.
98 Robertson KD. DNA methylation, methyltransferases, and cancer. Oncogene 2001;20:313955.[CrossRef][ISI][Medline]
99 Feinberg AP, Gehrke CW, Kuo KC, Ehrlich M. Reduced genomic 5-methylcytosine content in human colonic neoplasia. Cancer Res 1988;48:115961.[Abstract]
100 Cravo M, Pinto R, Fidalgo P, Chaves P, Gloria L, Nobre-Leitao C, et al. Global DNA hypomethylation occurs in the early stages of intestinal type gastric carcinoma. Gut 1996;39:4348.[Abstract]
101 Soares J, Pinto AE, Cunha CV, Andre S, Barao I, Sousa JM, et al. Global DNA hypomethylation in breast carcinoma: correlation with prognostic factors and tumor progression. Cancer 1999;85:1128.[CrossRef][ISI][Medline]
102 Laird PW, Jackson-Grusby L, Fazeli A, Dickinson SL, Jung WE, Li E, et al. Suppression of intestinal neoplasia by DNA hypomethylation. Cell 1995;81:197205.[CrossRef][ISI][Medline]
103 Gaudet F, Hodgson JG, Eden A, Jackson-Grusby L, Dausman J, Gray JW, et al. Induction of tumors in mice by genomic hypomethylation. Science 2003;300:48992.
104 Cormier RT, Dove WF. Dnmt1N/+ reduces the net growth rate and multiplicity of intestinal adenomas in C57BL/6-multiple intestinal neoplasia (Min)/+ mice independently of p53 but demonstrates strong synergy with the modifier of Min 1(AKR) resistance allele. Cancer Res 2000;60:396570.
105 Lengauer C. Cancer. An unstable liaison. Science 2003;300:4423.
106 Bedford MT, van Helden PD. Hypomethylation of DNA in pathological conditions of the human prostate. Cancer Res 1987;47:52746.[Abstract]
107 Schulz WA, Elo JP, Florl AR, Pennanen S, Santourlidis S, Engers R, et al. Genomewide DNA hypomethylation is associated with alterations on chromosome 8 in prostate carcinoma. Genes Chromosomes Cancer 2002;35:5865.[CrossRef][ISI][Medline]
108 Feinberg AP, Vogelstein B. Hypomethylation distinguishes genes of some human cancers from their normal counterparts. Nature 1983;301:8992.[ISI][Medline]
109 Feinberg AP, Vogelstein B. Hypomethylation of ras oncogenes in primary human cancers. Biochem Biophys Res Commun 1983;111:4754.[ISI][Medline]
110 Tao L, Yang S, Xie M, Kramer PM, Pereira MA. Hypomethylation and overexpression of c-jun and c-myc protooncogenes and increased DNA methyltransferase activity in dichloroacetic and trichloroacetic acid-promoted mouse liver tumors. Cancer Lett 2000;158:18593.[CrossRef][ISI][Medline]
111 Tsujiuchi T, Tsutsumi M, Sasaki Y, Takahama M, Konishi Y. Hypomethylation of CpG sites and c-myc gene overexpression in hepatocellular carcinomas, but not hyperplastic nodules, induced by a choline-deficient L-amino acid-defined diet in rats. Jpn J Cancer Res 1999;90:90913.[ISI][Medline]
112 Fruhwald MC, Plass C. Global and gene-specific methylation patterns in cancer: aspects of tumor biology and clinical potential. Mol Genet Metab 2002;75:116.[CrossRef][ISI][Medline]
113 Van Veldhuizen PJ, Sadasivan R, Cherian R, Wyatt A. Urokinase-type plasminogen activator expression in human prostate carcinomas. Am J Med Sci 1996;312:811.[CrossRef][ISI][Medline]
114 Helenius MA, Saramaki OR, Linja MJ, Tammela TL, Visakorpi T. Amplification of urokinase gene in prostate cancer. Cancer Res 2001;61:53404.
115 Pakneshan P, Xing RH, Rabbani SA. Methylation status of uPA promoter as a molecular mechanism regulating prostate cancer invasion and growth in vitro and in vivo. Faseb J 2003;17:10818.
116 Cho B, Lim Y, Lee DY, Park SY, Lee H, Kim WH, et al. Identification and characterization of a novel cancer/testis antigen gene CAGE. Biochem Biophys Res Commun 2002;292:71526.[CrossRef][ISI][Medline]
117 Cho B, Lee H, Jeong S, Bang YJ, Lee HJ, Hwang KS, et al. Promoter hypomethylation of a novel cancer/testis antigen gene CAGE is correlated with its aberrant expression and is seen in premalignant stage of gastric carcinoma. Biochem Biophys Res Commun 2003;307:5263.[CrossRef][ISI][Medline]
118 Robertson KD, Uzvolgyi E, Liang G, Talmadge C, Sumegi J, Gonzales FA, et al. The human DNA methyltransferases (DNMTs) 1, 3a and 3b: coordinate mRNA expression in normal tissues and overexpression in tumors. Nucleic Acids Res 1999;27:22918.
119 Nakagawa T, Kanai Y, Saito Y, Kitamura T, Kakizoe T, Hirohashi S. Increased DNA methyltransferase 1 protein expression in human transitional cell carcinoma of the bladder. J Urol 2003;170:24636.[CrossRef][ISI][Medline]
120 Ehrlich M. Expression of various genes is controlled by DNA methylation during mammalian development. J Cell Biochem 2003;88:899910.[CrossRef][ISI][Medline]
121 Kaneda A, Tsukamoto T, Takamura-Enya T, Watanabe N, Kaminishi M, Sugimura T, et al. Frequent hypomethylation in multiple promoter CpG islands is associated with global hypomethylation, but not with frequent promoter hypermethylation. Cancer Sci 2004;95:5864.[ISI][Medline]
122 Bariol C, Suter C, Cheong K, Ku SL, Meagher A, Hawkins N, et al. The relationship between hypomethylation and CpG island methylation in colorectal neoplasia. Am J Pathol 2003;162:136171.
123 Tsubaki J, Hwa V, Twigg SM, Rosenfeld RG. Differential activation of the IGF binding protein-3 promoter by butyrate in prostate cancer cells. Endocrinology 2002;143:177888.
124 Huang H, Reed CP, Zhang JS, Shridhar V, Wang L, Smith DI. Carboxypeptidase A3 (CPA3): a novel gene highly induced by histone deacetylase inhibitors during differentiation of prostate epithelial cancer cells. Cancer Res 1999;59:29818.
125 Rauen KA, Sudilovsky D, Le JL, Chew KL, Hann B, Weinberg V, et al. Expression of the coxsackie adenovirus receptor in normal prostate and in primary and metastatic prostate carcinoma: potential relevance to gene therapy. Cancer Res 2002;62:38128.
126 Pong RC, Lai YJ, Chen H, Okegawa T, Frenkel E, Sagalowsky A, et al. Epigenetic regulation of coxsackie and adenovirus receptor (CAR) gene promoter in urogenital cancer cells. Cancer Res 2003;63:86806.
127 Goldsmith ME, Kitazono M, Fok P, Aikou T, Bates S, Fojo T. The histone deacetylase inhibitor FK228 preferentially enhances adenovirus transgene expression in malignant cells. Clin Cancer Res 2003;9:5394401.
128 Yang ES, Burnstein KL. Vitamin D inhibits G1 to S progression in LNCaP prostate cancer cells through p27Kip1 stabilization and Cdk2 mislocalization to the cytoplasm. J Biol Chem 2003;278:468628.
129 Moffatt KA, Johannes WU, Miller GJ. 1Alpha,25dihydroxyvitamin D3 and platinum drugs act synergistically to inhibit the growth of prostate cancer cell lines. Clin Cancer Res 1999;5:695703.
130 Ikeda N, Uemura H, Ishiguro H, Hori M, Hosaka M, Kyo S, et al. Combination treatment with 1alpha,25-dihydroxyvitamin D3 and 9-cis-retinoic acid directly inhibits human telomerase reverse transcriptase transcription in prostate cancer cells. Mol Cancer Ther 2003;2:73946.
131 Zhao XY, Peehl DM, Navone NM, Feldman D. 1alpha,25-dihydroxyvitamin D3 inhibits prostate cancer cell growth by androgen-dependent and androgen-independent mechanisms. Endocrinology 2000;141:254856.
132 Zhuang SH, Burnstein KL. Antiproliferative effect of 1alpha,25-dihydroxyvitamin D3 in human prostate cancer cell line LNCaP involves reduction of cyclin-dependent kinase 2 activity and persistent G1 accumulation. Endocrinology 1998;139:1197207.
133 Ly LH, Zhao XY, Holloway L, Feldman D. Liarozole acts synergistically with 1alpha,25-dihydroxyvitamin D3 to inhibit growth of DU 145 human prostate cancer cells by blocking 24-hydroxylase activity. Endocrinology 1999;140:20716.
134 Banwell CM, Singh R, Stewart PM, Uskokovic MR, Campbell MJ. Antiproliferative signalling by 1,25(OH)2D3 in prostate and breast cancer is suppressed by a mechanism involving histone deacetylation. Recent Results Cancer Res 2003;164:8398.[Medline]
135 Strahl BD, Ohba R, Cook RG, Allis CD. Methylation of histone H3 at lysine 4 is highly conserved and correlates with transcriptionally active nuclei in Tetrahymena. Proc Natl Acad Sci U S A 1999;96:1496772.
136 Kim J, Jia L, Tilley WD, Coetzee GA. Dynamic methylation of histone H3 at lysine 4 in transcriptional regulation by the androgen receptor. Nucleic Acids Res 2003;31:67417.
137 Antequera F, Bird A. CpG islands as genomic footprints of promoters that are associated with replication origins. Curr Biol 1999;9:R6617.[CrossRef][ISI][Medline]
138 Fuks F, Burgers WA, Godin N, Kasai M, Kouzarides T. Dnmt3a binds deacetylases and is recruited by a sequence-specific repressor to silence transcription. Embo J 2001;20:253644.
139 Robertson KD, Ait-Si-Ali S, Yokochi T, Wade PA, Jones PL, Wolffe AP. DNMT1 forms a complex with Rb, E2F1 and HDAC1 and represses transcription from E2F-responsive promoters. Nat Genet 2000;25:33842.[CrossRef][ISI][Medline]
140 Nakayama T, Watanabe M, Yamanaka M, Hirokawa Y, Suzuki H, Ito H, et al. The role of epigenetic modifications in retinoic acid receptor 2 gene expression in human prostate cancers. Lab Invest 2001;81:104957.[ISI][Medline]
141 Fuks F, Hurd PJ, Deplus R, Kouzarides T. The DNA methyltransferases associate with HP1 and the SUV39H1 histone methyltransferase. Nucleic Acids Res 2003;31:230512.
142 Fuks F, Hurd PJ, Wolf D, Nan X, Bird AP, Kouzarides T. The methyl-CpG-binding protein MeCP2 links DNA methylation to histone methylation. J Biol Chem 2003;278:403540.
143 Freitag M, Hickey PC, Khlafallah TK, Read ND, Selker EU. HP1 is essential for DNA methylation in neurospora. Mol Cell 2004;13:42734.[CrossRef][ISI][Medline]
144 Lehnertz B, Ueda Y, Derijck AA, Braunschweig U, Perez-Burgos L, Kubicek S, et al. Suv39h-mediated histone H3 lysine 9 methylation directs DNA methylation to major satellite repeats at pericentric heterochromatin. Curr Biol 2003;13:1192200.[CrossRef][ISI][Medline]
145 Kondo Y, Shen L, Issa JP. Critical role of histone methylation in tumor suppressor gene silencing in colorectal cancer. Mol Cell Biol 2003;23:20615.
146 Bachman KE, Park BH, Rhee I, Rajagopalan H, Herman JG, Baylin SB, et al. Histone modifications and silencing prior to DNA methylation of a tumor suppressor gene. Cancer Cell 2003;3:8995.[ISI][Medline]
147 Stirzaker C, Song JZ, Davidson B, Clark SJ. Transcriptional gene silencing promotes DNA hypermethylation through a sequential change in chromatin modifications in cancer cells. Cancer Res 2004;64:38717.
148 Ransohoff DF. Cancer. Developing molecular biomarkers for cancer. Science 2003;299:167980.
149 Herman JG, Baylin SB. Gene silencing in cancer in association with promoter hypermethylation. N Engl J Med 2003;349:204254.
150 Herman JG, Graff JR, Myohanen S, Nelkin BD, Baylin SB. Methylation-specific PCR: a novel PCR assay for methylation status of CpG islands. Proc Natl Acad Sci U S A 1996;93:98216.
151 Clark SJ, Harrison J, Paul CL, Frommer M. High sensitivity mapping of methylated cytosines. Nucleic Acids Res 1994;22:29907.[Abstract]
152 Costello JF, Plass C, Cavenee WK. Aberrant methylation of genes in low-grade astrocytomas. Brain Tumor Pathol 2000;17:4956.[Medline]
153 Battagli C, Uzzo RG, Dulaimi E, Ibanez de Caceres I, Krassenstein R, Al-Saleem T, et al. Promoter hypermethylation of tumor suppressor genes in urine from kidney cancer patients. Cancer Res 2003;63:86959.
154 Ricciardiello L, Goel A, Mantovani V, Fiorini T, Fossi S, Chang DK, et al. Frequent loss of hMLH1 by promoter hypermethylation leads to microsatellite instability in adenomatous polyps of patients with a single first-degree member affected by colon cancer. Cancer Res 2003;63:78792.
155 Kawakami K, Brabender J, Lord RV, Groshen S, Greenwald BD, Krasna MJ, et al. Hypermethylated APC DNA in plasma and prognosis of patients with esophageal adenocarcinoma. J Natl Cancer Inst 2000;92:180511.
156 Goessl C, Krause H, Muller M, Heicappell R, Schrader M, Sachsinger J, et al. Fluorescent methylation-specific polymerase chain reaction for DNA- based detection of prostate cancer in bodily fluids. Cancer Res 2000;60:59415.
157 Jeronimo C, Usadel H, Henrique R, Silva C, Oliveira J, Lopes C, et al. Quantitative GSTP1 hypermethylation in bodily fluids of patients with prostate cancer. Urology 2002;60:11315.[CrossRef][ISI][Medline]
158 Suh CI, Shanafelt T, May DJ, Shroyer KR, Bobak JB, Crawford ED, et al. Comparison of telomerase activity and GSTP1 promoter methylation in ejaculate as potential screening tests for prostate cancer. Mol Cell Probes 2000;14:2117.[CrossRef][ISI][Medline]
159 Gonzalgo ML, Nakayama M, Lee SM, De Marzo AM, Nelson WG. Detection of GSTP1 methylation in prostatic secretions using combinatorial MSP analysis. Urology 2004;63:4148.[CrossRef][ISI][Medline]
160 Cairns P, Esteller M, Herman JG, Schoenberg M, Jeronimo C, Sanchez-Cespedes M, et al. Molecular detection of prostate cancer in urine by GSTP1 hypermethylation. Clin Cancer Res 2001;7:272730.
161 Goessl C, Muller M, Heicappell R, Krause H, Straub B, Schrader M, et al. DNA-based detection of prostate cancer in urine after prostatic massage. Urology 2001;58:3358.[CrossRef][ISI][Medline]
162 Gonzalgo ML, Pavlovich CP, Lee SM, Nelson WG. Prostate cancer detection by GSTP1 methylation analysis of postbiopsy urine specimens. Clin Cancer Res 2003;9:26737.
163 Goessl C, Muller M, Heicappell R, Krause H, Schostak M, Straub B, et al. Methylation-specific PCR for detection of neoplastic DNA in biopsy washings. J Pathol 2002;196:3314.[CrossRef][ISI][Medline]
164 Harden SV, Sanderson H, Goodman SN, Partin AA, Walsh PC, Epstein JI, et al. Quantitative GSTP1 methylation and the detection of prostate adenocarcinoma in sextant biopsies. J Natl Cancer Inst 2003;95:16347.
165 Harden SV, Guo Z, Epstein JI, Sidransky D. Quantitative GSTP1 methylation clearly distinguishes benign prostatic tissue and limited prostate adenocarcinoma. J Urol 2003;169:113842.[ISI][Medline]
166 Kollermann J, Muller M, Goessl C, Krause H, Helpap B, Pantel K, et al. Methylation-specific PCR for DNA-based detection of occult tumor cells in lymph nodes of prostate cancer patients. Eur Urol 2003;44:5338.[CrossRef][ISI][Medline]
167 Goffin J, Eisenhauer E. DNA methyltransferase inhibitorsstate of the art. Ann Oncol 2002;13:1699716.
168 Thibault A, Figg WD, Bergan RC, Lush RM, Myers CE, Tompkins A, et al. A phase II study of 5-aza-2'deoxycytidine (decitabine) in hormone independent metastatic (D2) prostate cancer. Tumori 1998;84:879.[ISI][Medline]
169 Jones PA, Taylor SM. Cellular differentiation, cytidine analogs and DNA methylation. Cell 1980;20:8593.[CrossRef][ISI][Medline]
170 Jackson-Grusby L, Laird PW, Magge SN, Moeller BJ, Jaenisch R. Mutagenicity of 5-aza-2'-deoxycytidine is mediated by the mammalian DNA methyltransferase. Proc Natl Acad Sci U S A 1997;94:46815.
171 Walker C, Nettesheim P. In vitro transformation of primary rat tracheal epithelial cells by 5-azacytidine. Cancer Res 1986;46:64337.[Abstract]
172 Lin X, Asgari K, Putzi MJ, Gage WR, Yu X, Cornblatt BS, et al. Reversal of GSTP1 CpG island hypermethylation and reactivation of pi-class glutathione S-transferase (GSTP1) expression in human prostate cancer cells by treatment with procainamide. Cancer Res 2001;61:86116.
173 Lu Q, Kaplan M, Ray D, Zacharek S, Gutsch D, Richardson B. Demethylation of ITGAL (CD11a) regulatory sequences in systemic lupus erythematosus. Arthritis Rheum 2002;46:128291.[CrossRef][ISI][Medline]
174 Segura-Pacheco B, Trejo-Becerril C, Perez-Cardenas E, Taja-Chayeb L, Mariscal I, Chavez A, et al. Reactivation of tumor suppressor genes by the cardiovascular drugs hydralazine and procainamide and their potential use in cancer therapy. Clin Cancer Res 2003;9:1596603.
175 Scheinbart LS, Johnson MA, Gross LA, Edelstein SR, Richardson BC. Procainamide inhibits DNA methyltransferase in a human T cell line. J Rheumatol 1991;18:5304.[ISI][Medline]
176 Fang MZ, Wang Y, Ai N, Hou Z, Sun Y, Lu H, et al. Tea polyphenol (-)-epigallocatechin-3-gallate inhibits DNA methyltransferase and reactivates methylation-silenced genes in cancer cell lines. Cancer Res 2003;63:756370.
177 Milutinovic S, Brown SE, Zhuang Q, Szyf M. DNMT1 knock down induces gene expression by a mechanism independent of the two epigenetic silencing mechanisms: DNA methylation and histone deacetylation. J Biol Chem 2004;279:2791527.
178 Borde-Chiche P, Diedericha M, Morceau F, Puga A, Wellman M, Dicato M. Regulation of transcription of the glutathione S-transferase P1 gene by methylation of the minimal promoter in human leukemia cells. Biochem Pharmacol 2001;61:60512.[CrossRef][ISI][Medline]
179 Levine A, Cantoni GL, Razin A. Inhibition of promoter activity by methylation: possible involvement of protein mediators. Proc Natl Acad Sci U S A 1991;88:65158.
180 Yao X, Hu JF, Daniels M, Shiran H, Zhou X, Yan H, et al. A methylated oligonucleotide inhibits IGF2 expression and enhances survival in a model of hepatocellular carcinoma. J Clin Invest 2003;111:26573.
181 Gray SG, Ekstrom TJ. The human histone deacetylase family. Exp Cell Res 2001;262:7583.[CrossRef][ISI][Medline]
182 Suenaga M, Soda H, Oka M, Yamaguchi A, Nakatomi K, Shiozawa K, et al. Histone deacetylase inhibitors suppress telomerase reverse transcriptase mRNA expression in prostate cancer cells. Int J Cancer 2002;97:6215.[ISI][Medline]
183 Sasakawa Y, Naoe Y, Noto T, Inoue T, Sasakawa T, Matsuo M, et al. Antitumor efficacy of FK228, a novel histone deacetylase inhibitor, depends on the effect on expression of angiogenesis factors. Biochem Pharmacol 2003;66:897906.[CrossRef][ISI][Medline]
184 Thelen P, Schweyer S, Hemmerlein B, Wuttke W, Seseke F, Ringert RH. Expressional changes after histone deacetylase inhibition by valproic acid in LNCaP human prostate cancer cells. Int J Oncol 2004;24:2531.[ISI][Medline]
185 Camphausen K, Burgan W, Cerra M, Oswald KA, Trepel JB, Lee MJ, et al. Enhanced radiation-induced cell killing and prolongation of gammaH2AX foci expression by the histone deacetylase inhibitor MS-275. Cancer Res 2004;64:31621.
186 Butler LM, Webb Y, Agus DB, Higgins B, Tolentino TR, Kutko MC, et al. Inhibition of transformed cell growth and induction of cellular differentiation by pyroxamide, an inhibitor of histone deacetylase. Clin Cancer Res 2001;7:96270.
187 Dyer ES, Paulsen MT, Markwart SM, Goh M, Livant DL, Ljungman M. Phenylbutyrate inhibits the invasive properties of prostate and breast cancer cell lines in the sea urchin embryo basement membrane invasion assay. Int J Cancer 2002;101:4969.[CrossRef][ISI][Medline]
188 Vigushin DM, Coombes RC. Histone deacetylase inhibitors in cancer treatment. Anticancer Drugs 2002;13:113.[CrossRef][ISI][Medline]
189 Sasakawa Y, Naoe Y, Inoue T, Sasakawa T, Matsuo M, Manda T, et al. Effects of FK228, a novel histone deacetylase inhibitor, on tumor growth and expression of p21 and c-myc genes in vivo. Cancer Lett 2003;195:1618.[ISI][Medline]
190 Butler LM, Agus DB, Scher HI, Higgins B, Rose A, Cordon-Cardo C, et al. Suberoylanilide hydroxamic acid, an inhibitor of histone deacetylase, suppresses the growth of prostate cancer cells in vitro and in vivo. Cancer Res 2000;60:516570.
191 Kuefer R, Hofer MD, Altug V, Zorn C, Genze F, Kunzi-Rapp K, et al. Sodium butyrate and tributyrin induce in vivo growth inhibition and apoptosis in human prostate cancer. Br J Cancer 2004;90:53541.[CrossRef][ISI][Medline]
192 Ghoshal K, Datta J, Majumder S, Bai S, Dong X, Parthun M, et al. Inhibitors of histone deacetylase and DNA methyltransferase synergistically activate the methylated metallothionein I promoter by activating the transcription factor MTF-1 and forming an open chromatin structure. Mol Cell Biol 2002;22:830219.
193 Weiser TS, Guo ZS, Ohnmacht GA, Parkhurst ML, Tong-On P, Marincola FM, et al. Sequential 5-aza-2'-deoxycytidine-depsipeptide FR901228 treatment induces apoptosis preferentially in cancer cells and facilitates their recognition by cytolytic T lymphocytes specific for NY-ESO-1. J Immunother 2001;24:15161.[CrossRef][ISI]
194 Cameron EE, Bachman KE, Myohanen S, Herman JG, Baylin SB. Synergy of demethylation and histone deacetylase inhibition in the re-expression of genes silenced in cancer. Nat Genet 1999;21:1037.[CrossRef][ISI][Medline]
195 Zhang J, Liu L, Pfeifer GP. Methylation of the retinoid response gene TIG1 in prostate cancer correlates with methylation of the retinoic acid receptor gene. Oncogene 2003;23:22419.[CrossRef][ISI]
196 Padar A, Sathyanarayana UG, Suzuki M, Maruyama R, Hsieh JT, Frenkel EP, et al. Inactivation of cyclin D2 gene in prostate cancers by aberrant promoter methylation. Clin Cancer Res 2003;9:47304.
197 Singal R, van Wert J, Bashambu M. Cytosine methylation represses glutathione S-transferase P1 (GSTP1) gene expression in human prostate cancer cells. Cancer Res 2001;61:48206.
198 Zhou M, Tokumaru Y, Sidransky D, Epstein JI. Quantitative GSTP1 methylation levels correlate with Gleason grade and tumor volume in prostate needle biopsies. J Urol 2004;171:21958.[CrossRef][ISI][Medline]
199 Woodson K, Gillespie J, Hanson J, Emmert-Buck M, Phillips JM, Linehan WM, et al. Heterogeneous gene methylation patterns among pre-invasive and cancerous lesions of the prostate: a histopathologic study of whole mount prostate specimens. Prostate 2004;60:2531.[CrossRef][ISI][Medline]
200 Jeronimo C, Henrique R, Campos PF, Oliveira J, Caballero OL, Lopes C, et al. Endothelin B receptor gene hypermethylation in prostate adenocarcinoma. J Clin Pathol 2003;56:525.
201 Nelson JB, Lee WH, Nguyen SH, Jarrard DF, Brooks JD, Magnuson SR, et al. Methylation of the 5' CpG island of the endothelin B receptor gene is common in human prostate cancer. Cancer Res 1997;57:357.[Abstract]
202 Wu M, Ho SM. PMP24, a gene identified by MSRF, undergoes DNA hypermethylation-associated gene silencing during cancer progression in an LNCaP model. Oncogene 2004;23:2509.[CrossRef][ISI][Medline]
Manuscript received June 30, 2004; revised August 31, 2004; accepted November 19, 2004.
This article has been cited by other articles in HighWire Press-hosted journals:
![]() |
||||
|
Oxford University Press Privacy Policy and Legal Statement |