Loss of a single Hic1 allele accelerates polyp formation in Apc(Δ716) mice.

Adenomatous polyposis coli (APC) gene mutations have been implicated in familial and sporadic gastrointestinal (GI) cancers. APC mutations are associated with autosomal dominant inheritance of disease in humans. Similarly, mice that contain a single mutant APC gene encoding a protein truncated at residue 716 (Apc(Δ716)) develop multiple polyps throughout the GI tract as early as 4 weeks after birth. Inactivation of another tumor suppressor gene, Hypermethylated in Cancer 1 (HIC1), often occurs in human colon cancers, among others, via CpG island hypermethylation. Homozygous deletion of Hic1 in mice results in major developmental defects and embryonic lethality. Hic1 heterozygotes have previously been shown to develop tumors of a variety of tissue types. We now report that loss of a single Hic1 allele can promote crypt hyperplasia and neoplasia of the GI tract, and Hic1(+/-), Apc(+/Δ716) double heterozygotes (DH) develop increased numbers of polyps throughout the GI tract at 60 days. Hic1 expression is absent in polyps from DH mice, with concomitant increased expression of two transcriptional repression targets of Hic1, Sirt1 and Sox9. Together, our data suggest that loss of a gene frequently silenced via epigenetic mechanisms, Hic1, can cooperate with loss of a gene mutated in GI cancer, Apc, to promote tumorigenesis in an in vivo model of multiple intestinal neoplasia.

Transcriptional regulation of Wnt inhibitory factor-1 by Miz-1/c-Myc.

The Wnt signaling pathway is capable of self-regulation through positive and negative feedback mechanisms. For example, the oncoprotein c-Myc, which is upregulated by Wnt signaling activity, participates in a positive feedback loop of canonical Wnt signaling through repression of Wnt antagonists DKK1 and SFRP1. In this study, we investigated the mechanism of Wnt inhibitory factor-1 (WIF-1) silencing. Mapping of CpG island methylation of the WIF-1 promoter reveals regional methylation (-295 to -95 bp from the transcription start site) that correlates with transcriptional silencing. We identified Miz-1 as a direct activator of WIF-1 transcriptional activity, which is found at WIF-1 promoter. In addition, we show that c-Myc contributes to WIF-1 transcriptional repression in a Miz-1-dependent manner. Although the transient repression mediated by Miz-1/c-Myc is independent of de novo methylation, the stable repression by this complex is associated with CpG island methylation of the critical -295 to -95-bp region of the WIF-1 promoter. Importantly, Miz-1 and c-Myc are found at WIF-1 promoter in WIF-1 non-expressing cell lines DLD-1 and 209myc. Transient knockdown or somatic knockout of c-Myc in DLD-1 failed to restore WIF-1 expression suggesting that c-Myc is involved in initiating rather than maintaining WIF-1 epigenetic silencing. In a genome-wide screen, DNAJA4, TGFß-induced and TRIM59 were repressed by c-Myc overexpression and DNA promoter hypermethylation. Our data reveal novel insights into c-Myc-mediated DNA methylation-dependent transcriptional silencing, a mechanism that might contribute to the dysregulation of Wnt signaling in cancer.

A potential tumor suppressor role for Hic1 in breast cancer through transcriptional repression of ephrin-A1.

The tumor suppressor gene hypermethylated in cancer 1 (HIC1), which encodes a transcriptional repressor, is epigenetically inactivated in various human cancers. In this study, we show that HIC1 is a direct transcriptional repressor of the gene encoding ephrin-A1, a cell surface ligand implicated in the pathogenesis of epithelial cancers. We also show that mouse embryos lacking both Hic1 alleles manifest developmental defects spatially associated with the misexpression of ephrin-A1, and that overexpression of ephrin-A1 is a feature of tumors arising in Hic1 heterozygous mice in which the remaining wild-type allele is epigenetically silenced. In breast cancer, we find that ephrin-A1 expression is common in vivo, but that in cell culture, expression of the EphA receptors is predominant. Restoration of HIC1 function in breast cancer cells leads to a reduction in tumor growth in vivo, an effect that can be partially rescued by co-overexpression of ephrin-A1. Interestingly, overexpression of ephrin-A1 in vitro triggers downregulation of EphA2 and EphA4 levels, resulting in an expression pattern similar to that seen in vivo. We conclude that Hic1 spatially restricts ephrin-A1 expression in development, and that upregulated expression of ephrin-A1 resulting from epigenetic silencing of HIC1 in cancer cells may be an important mechanism in epithelial malignancy.

Epigenetic dysregulation of secreted Frizzled-related proteins in multiple myeloma.

We analysed the clinical impact of epigenetic dysregulation of the Wnt pathway in malignant plasma cell disorders. In multiple myeloma (MM) cell lines, aberrant promoter hypermethylation of the secreted Frizzled-related protein (SFRP) genes was a common event, and hypermethylation of SFRP1,-2 and -5 was associated with transcriptional silencing. Among 76 primary patient samples, the frequency of aberrant methylation was 35.5% for SFRP1, 52.6% for SFRP2, 1.3% for SFRP4 and 6.9% for SFRP5. Hypermethylation of SFRP1 and -2 genes was detected in monoclonal gammopathy of undetermined significance and all MM stages including plasma cell leukaemia (PCL), while SFRP5 methylation was restricted to advanced MM stages and PCL. Our data indicate that epigenetic silencing of Wnt antagonists is an early event in MM pathogenesis and that SFRP5 hypermethylation may play a role in disease progression.

MGMT and MLH1 promoter methylation versus APC, KRAS and BRAF gene mutations in colorectal cancer: indications for distinct pathways and sequence of events.

BACKGROUND: To study how caretaker gene silencing relates to gatekeeper mutations in colorectal cancer (CRC), we investigated whether O6-methylguanine DNA methyltransferase (MGMT) and Human Mut-L Homologue 1 (MLH1) promoter hypermethylation are associated with APC, KRAS and BRAF mutations among 734 CRC patients. METHODS: We compared MGMT hypermethylation with G:C > A:T mutations in APC and KRAS and with the occurrence of such mutations in CpG or non-CpG dinucleotides in APC. We also compared MLH1 hypermethylation with truncating APC mutations and activating KRAS and BRAF mutations. RESULTS: Only 10% of the tumors showed both MGMT and MLH1 hypermethylation. MGMT hypermethylation occurred more frequently in tumors with G:C > A:T KRAS mutations (55%) compared with those without these mutations (38%, P < 0.001). No such difference was observed for G:C > A:T mutations in APC, regardless of whether mutations occurred in CpG or non-CpG dinucleotides. MLH1 hypermethylation was less common in tumors with APC mutations (P = 0.006) or KRAS mutations (P = 0.001), but was positively associated with BRAF mutations (P < 0.001). CONCLUSIONS: MGMT hypermethylation is associated with G:C > A:T mutations in KRAS, but not in APC, suggesting that MGMT hypermethylation may succeed APC mutations but precedes KRAS mutations in colorectal carcinogenesis. MLH1-hypermethylated tumors harbor fewer APC and KRAS mutations and more BRAF mutations, suggesting that they develop distinctly from an MGMT methylator pathway.

Epigenetic inactivation of secreted Frizzled-related proteins in acute myeloid leukaemia.

The Wnt signalling pathway has a key function in stem cell maintenance and differentiation of haematopoietic progenitors. Secreted Frizzled-related protein genes (SFRPs), functioning as Wnt signalling antagonists, have been found to be downregulated by promoter hypermethylation in many tumours. To analyse epigenetic dysregulation of SFRPs in acute myeloid leukaemia (AML), we examined the promoter methylation status of SFRP1, -2, -4 and -5 in AML cell lines by methylation-specific polymerase chain reaction (MSP). Aberrant CpG island methylation was found for all four SFRP genes. By real-time reverse transcription-PCR, corresponding transcriptional silencing for SFRP1 and -2 was demonstrated and treatment of cell lines with 5-aza-2'-deoxycytidine resulted in re-expression. The methylation status of the SFRP genes was analysed in 100 specimens obtained from AML patients at diagnosis. The frequencies of aberrant methylation among the patient samples were 29% for SFRP1, 19% for SFRP2, 0% for SFRP4 and 9% for SFRP5. For SFRP2, a correlation between promoter hypermethylation and transcriptional downregulation was found in primary AML samples. Among AML cases with a favourable karyotype, hypermethylation of SFRP genes was restricted to patients with core binding factor (CBF) leukaemia, and aberrant methylation of the SFRP2 promoter was an adverse risk factor for survival in CBF leukaemia.

p21(WAF1/CIP1) induction by 5-azacytosine nucleosides requires DNA damage.

Decitabine (DAC) and 5-azacitidine have recently been approved for the treatment of myelodysplastic syndrome. The pharmacodynamic effects of DAC and 5-azacitidine outside their known activity as inhibitors of DNA methyltransferases (DNMTs) require further investigation. The purpose of this study was to investigate the effect of DAC on the expression of p21(WAF1/CIP1), a gene with a putative CpG island surrounding its promoter region. Promoter methylation analysis of p21(WAF1/CIP1) in leukemia cells revealed the absence of CpG methylation. However, DAC upregulated p21(WAF1/CIP1) expression in a dose-dependent manner (ED(50)=103.34 nM) and induced G2/M cell cycle arrest in leukemia cells. Sequential application of DAC followed by different histone deacetylase inhibitors induced expression of p21(WAF1/CIP1) synergistically. Upregulation of p21(WAF1/CIP1) paralleled DAC-induced apoptosis (ED(50)=153 nM). Low doses of DAC induced gamma-H2AX expression (ED(50)=16.5 nM) and upregulated p21(WAF1/CIP1) in congenic HCT 116 colon cancer cells in a DNMT-independent and p53-dependent fashion. Inhibition of p53 transactivation by pifithrin-alpha or the kinase activity of ATM by either the specific ATM inhibitor KU-5593 or caffeine abrogated p21(WAF1/CIP1) upregulation, indicating that DAC upregulation of p21(WAF1/CIP1) was p53- and ATM-dependent in leukemia cells. In conclusion, DAC upregulates p21(WAF1/CIP1) in DNMT-independent manner via the DNA damage/ATM/p53 axis.

Optimal primer design using the novel primer design program: MSPprimer provides accurate methylation analysis of the ATM promoter.

Methylation-specific polymerase chain reaction (PCR) (MSP) is frequently used to study gene silencing by promoter hypermethylation. However, non-specific primer design can lead to false-positive detection of methylation. We present a novel, web-based algorithm for the design of primers for bisulfite-PCRs (MSP, sequencing, COBRA and multiplex-MSP), allowing the determination of a specificity score, which is based on the thermodynamic characteristics of the primer 3'-end. PCR amplification with primers not reaching a high specificity score can result in false-positive findings. We used MSPprimer to design MSP primers for analysis of the ATM promoter. In 37 non-small cell lung cancer (NSCLC) samples and 43 breast cancer samples no promoter methylation was detected. Conversely, published MSP primers not reaching the required specificity score led to non-specific amplification of DNA not converted by bisulfite. The result was a false-positive incidence of ATM promoter methylation of 24% in NSCLC and 48% in breast cancers, similar to published studies. This highlights the critical need for specific primer design for MSP. MSPprimer is a convenient tool to achieve this goal, which is available free of charge to the scientific community.

Epigenetic alterations complement mutation of JAK2 tyrosine kinase in patients with BCR/ABL-negative myeloproliferative disorders.

An acquired autoactivating mutation with a V617F amino-acid substitution in the JAK2 tyrosine kinase is frequently found in BCR/ABL-negative myeloproliferative disorders (MPD). Hypermethylation of CpG islands within gene promoter regions is associated with transcriptional inactivation and represents an important mechanism of gene silencing in the pathogenesis of hematopoietic malignancies. In this study, we determined the DNA methylation status of 13 cancer-related genes in the context of JAK2 mutations in 39 patients with MPD. Genes analyzed for hypermethylation were SOCS-1, SHP-1, E-cadherin, MGMT, TIMP-2, TIMP-3, p15, p16, p73, DAPK1, RASSF1A, RARbeta2 and hMLH1. We found at least one hypermethylated gene in 15/39 MPD patient specimens, and in 6/39 samples aberrant methylation of the negative cytokine regulator SOCS-1 was present. The JAK2V617F mutation was found in 21/39 patients as determined by allele-specific polymerase chain reaction. Hypermethylation of SOCS-1 was observed in 3/21 patients with an autoactivating JAK2 mutation and in 3/18 patients with wild-type JAK2. Our results suggest that epigenetic inactivation of SOCS-1 may be a complementary mechanism to the JAK2V617F mutation in the pathogenesis of MPD that leads to dysregulation of JAK-STAT signal transduction and thus contributes to growth factor hypersensitivity.

RASSF1A methylation and K-ras and B-raf mutations and recurrent endometrial cancer.

BACKGROUND: Aberrations in mediators of Ras signaling may increase the risk of developing recurrent endometrial carcinoma. PATIENTS AND METHODS: Primary tumors of patients with (n = 44) and without (n = 44) recurrent stage I endometrioid endometrial carcinoma were compared regarding the presence of K-ras mutations (codons 12 and 13), B-raf mutations (V599), and RASSF1A gene promoter methylation. RESULTS: K-ras mutations were present in 18% of the patients independent of recurrent disease. No B-raf mutations were found. RASSF1A methylation was demonstrated in 85% of endometrial carcinomas, independent of recurrence. The presence of K-ras mutations and RASSF1A promoter methylation were not related, either directly or inversely. Analysis in premenopausal endometrial carcinomas demonstrated K-ras mutations in 40%, no B-raf mutations, and RASSF1A promoter methylation in 70% of the cases. RASSF1A methylation was also observed in samples of cyclic (n = 14), hyperplastic (n = 8), and atrophic (n = 13) endometrial tissues in 21%, 50% and 38%, respectively. CONCLUSIONS: RASSF1A methylation was observed in a high frequency in endometrioid endometrial carcinoma whereas K-ras and B-raf mutations were observed in a low frequency. No association was observed with the development of recurrent disease. High-frequency RASSF1A methylation in premenopausal carcinomas and an increased frequency in endometrial hyperplasia indicate that this may be an early event in endometrial carcinogenesis.

Identification of mutations that disrupt phosphorylation-dependent nuclear export of cyclin D1.

Although cyclin D1 is overexpressed in a significant number of human cancers, overexpression alone is insufficient to promote tumorigenesis. In vitro studies have revealed that inhibition of cyclin D1 nuclear export unmasks its neoplastic potential. Cyclin D1 nuclear export depends upon phosphorylation of a C-terminal residue, threonine 286, (Thr-286) which in turn promotes association with the nuclear exportin, CRM1. Mutation of Thr-286 to a non-phosphorylatable residue results in a constitutively nuclear cyclin D1 protein with significantly increased oncogenic potential. To determine whether cyclin D1 is subject to mutations that inhibit its nuclear export in human cancer, we have sequenced exon 5 of cyclin D1 in primary esophageal carcinoma samples and in cell lines derived from esophageal cancer. Our work reveals that cyclin D1 is subject to mutations in primary human cancer. The mutations identified specifically disrupt phosphorylation of cyclin D1 at Thr-286, thereby enforcing nuclear accumulation of cyclin D1. Through characterization of these mutants, we also define an acidic residue within the C-terminus of cyclin D1 that is necessary for recognition and phosphorylation of cyclin D1 by glycogen synthase kinase-3 beta. Finally, through construction of compound mutants, we demonstrate that cell transformation by the cancer-derived cyclin D1 alleles correlates with their ability to associate with and activate CDK4. Our data reveal that cyclin D1 is subject to mutations in primary human cancer that specifically disrupt phosphorylation-dependent nuclear export of cyclin D1 and suggest that such mutations contribute to the genesis and progression of neoplastic growth.

Epigenetic changes in cancer and preneoplasia.

Recent studies have identified an increasing number of genes that are inactivated by promoter region methylation in cancer. Some of these genes were initially identified as altered genetically in cancer, but in other tumors they are silenced in association with promoter region CpG island methylation. New approaches for screening the genome add to this list of candidate tumor suppressor genes, and many genes regulated key pathways in cancer, including cell cycle control, DNA repair, and apoptosis. Transcription factors may also be silenced by promoter region methylation, affecting the expression of many downstream target genes and globally altering the cancer phenotype. Determining loss of expression is important in assigning functional importance to promoter region methylation for any gene. Individual cancers have alterations in many different genes, affecting many of these important pathways and contributing to the cancer phenotype. The number of genes targeted for promoter region methylation increases during neoplastic progression. These studies suggest that the epigenetic change of promoter region methylation plays a critical role in neoplastic transformation and progression.

DNA methylation changes in multiple myeloma.

Using a candidate gene approach, we analyzed the methylation status of the promoter-associated CpG islands of 11 well-characterized tumor suppressor genes by methylation-specific polymerase chain reaction in five multiple myeloma (MM) cell lines and 56 patients with malignant plasma cell disorders. The frequency of aberrant methylation among the patient samples was 46.4% for SOCS-1, 35.7% for p16, 21.4% for E-cadherin, 12.5% for DAP kinase and p73, 1.8% for p15, MGMT as well as RARbeta, and 0% for TIMP-3, RASSF1A and hMLH1. We found at least one hypermethylated gene in 80.4% of the primary patient samples, while 33.9% harbored two or more hypermethylated genes. For the first time, we show that p73 may be hypermethylated in MM and thus be involved in the pathogenesis of plasma cell disorders. Hypermethylation of p16 at diagnosis was associated with a poorer prognosis. In patients with plasma cell leukemia, we found frequent simultaneous hypermethylation of p16, E-cadherin and DAP kinase. We conclude that aberrant methylation of tumor suppressor genes is a common event in malignant plasma cell disorders and that there is a correlation between methylation patterns and clinical characteristics in MM patients.

DNA methylation patterns in hereditary human cancers mimic sporadic tumorigenesis.

Cancer cells have aberrant patterns of DNA methylation including hypermethylation of gene promoter CpG islands and global demethylation of the genome. Genes that cause familial cancer, as well as other genes, can be silenced by promoter hypermethylation in sporadic tumors, but the methylation of these genes in tumors from kindreds with inherited cancer syndromes has not been well characterized. Here, we examine CpG island methylation of 10 genes (hMLH1, BRCA1, APC, LKB1, CDH1, p16(INK4a), p14(ARF), MGMT, GSTP1 and RARbeta2) and 5-methylcytosine DNA content, in inherited (n = 342) and non-inherited (n = 215) breast and colorectal cancers. Our results show that singly retained alleles of germline mutated genes are never hypermethylated in inherited tumors. However, this epigenetic change is a frequent second "hit", associated with the wild-type copy of these genes in inherited tumors where both alleles are retained. Global hypomethylation was similar between sporadic and hereditary cases, but distinct differences existed in patterns of methylation at non-familial genes. This study demonstrates that hereditary cancers "mimic" the DNA methylation patterns present in the sporadic tumors.

Synergistic activation of functional estrogen receptor (ER)-alpha by DNA methyltransferase and histone deacetylase inhibition in human ER-alpha-negative breast cancer cells.

Formation of transcriptional repression complexes such as DNA methyltransferase (DNMT) 1/histone deacetylase (HDAC) or methyl-CpG binding protein/HDAC is emerging as an important mechanism in silencing a variety of methylated tissue-specific and imprinted genes. Our previous studies showed that treatment of estrogen receptor (ER)-alpha-negative human breast cancer cells with the DNMT inhibitor 5-aza-2'-deoxycytidine (5-aza-dC) led to ER mRNA and protein re-expression. Also, the HDAC inhibitor trichostatin A (TSA) could induce ER transcript about 5-fold. Here we show that 5-aza-dC alone induced ER transcript about 30-40-fold, and the addition of TSA elevated ER mRNA expression about 10-fold more in the human ER-negative breast cancer cell lines MDA-MB-231 and MDA-MB-435. Overall, the combination of 5-aza-dC and TSA induced a 300-400-fold increase in ER transcript. Restoration of estrogen responsiveness was demonstrated by the ability of the induced ER protein to elicit estrogen response element-regulated reporter activity from an exogenous plasmid as well as induce expression of the ER target gene, progesterone receptor. The synergistic activation of ER occurs concomitantly with markedly reduced soluble DNMT1 expression and activity, partial demethylation of the ER CpG island, and increased acetylation of histones H(3) and H(4). These data suggest that the activities of both DNMT1 and HDAC are key regulators of methylation-mediated ER gene silencing.

Frequent hypermethylation of the 5' CpG island of E-cadherin in esophageal adenocarcinoma.

PURPOSE: E-cadherin, a M(r) 120,000 transmembrane glycoprotein, mediates calcium-dependent intercellular adhesion that is essential for normal tissue homeostasis. Loss of E-cadherin occurs in a variety of epithelial tumors and is correlated with invasion and metastasis. In esophageal adenocarcinoma, reduction of E-cadherin expression has been demonstrated previously, but mutations of the gene (CDH1) are rare. EXPERIMENTAL DESIGN: In this study, we used a nested PCR approach to examine the methylation status of the 5' CpG island of E-cadherin in esophageal specimens obtained from individuals with and without a history of esophageal cancer. RESULTS: In four individuals without esophageal cancer, E-cadherin was completely unmethylated in normal squamous cell-lined esophageal mucosa. In contrast, in patients with esophageal adenocarcinoma, E-cadherin was methylated in 26 of 31 (84%) tumor specimens. In the majority of cases, matched normal tissue (esophagus or stomach) from each patient was completely unmethylated. By immunostaining, methylated tumor samples demonstrated heterogeneously decreased membranous E-cadherin staining. CONCLUSIONS: These data suggest that epigenetic silencing via aberrant methylation of the E-cadherin promoter is a common cause of inactivation of this gene in esophageal adenocarcinoma.

Methylation of the E-cadherin gene in bladder neoplasia and in normal urothelial epithelium from elderly individuals.

Decreased expression of the epithelial cell adhesion protein E-Cadherin occurs in several forms of human epithelial-derived cancers, including bladder cancers. We investigated the possibility that aberrant methylation of the CpG island flanking the 5' transcriptional start site of the e-cadherin gene is responsible for the decreased expression of this gene in bladder cancer, similar to the relationship previously seen between e-cadherin methylation and gene expression in other types of human cancers. Using methylation-specific polymerase chain reaction, we found methylation of this CpG island in 20 of 47 cases (43%) of bladder neoplasms ranging from low-grade papillary neoplasms to advanced, invasive cancers. When methylation status was compared to immunochemical staining for E-Cadherin, we found significantly diminished levels of E-Cadherin expression in 14 of 15 cases (93%) with methylation of the gene. We also found decreased expression of E-Cadherin, although to a somewhat lesser extent, in a high percentage (77%) of the cases without methylation of the gene. Although these data suggest a relationship between e-cadherin CpG island methylation and decreased gene expression, it evident that other mechanisms also contribute to decreased expression of this gene in bladder neoplasia. Remarkably, we also found low levels of e-cadherin methylation in urothelial cells from three of nine (33%) histologically normal bladders, with all three of the normal bladder samples with methylated e-cadherin being from individuals older than 70 years of age. Thus, methylation of the e-cadherin CpG island may occur normally in this tissue with aging as well as in low-grade papillary neoplasms, and is not specific to cancer in the bladder. This finding of methylation in normal urothelial cells from elderly individuals is provocative with respect to a possible link between aging and increased risk for bladder cancer, but it suggests limitations on the usefulness of using methylation of e-cadherin as a molecular marker for detection of bladder cancer.

Loss of chromosome arms 3p and 9p and inactivation of P16 (INK4a) in normal epithelium of patients with primary lung cancer.

The accumulation of genetic alterations in the respiratory epithelium may give rise to cancer and often is accompanied by a series of histologic alterations over a period of several years. Recent studies have identified some molecular alterations in histologically normal-appearing epithelium among patients with lung cancer. To extend these observations, we investigated clonal genetic alterations by using fluorescence in situ hybridization (FISH) analysis and immunohistochemistry in 69 biopsy samples of histologically normal-appearing bronchial epithelium from 22 patients with or without lung cancer. Thirty-seven biopsy specimens from 13 patients were examined for loss of 3p14, and 48 biopsy specimens from 18 patients were examined for loss at 9p21 by FISH. P16(INK4a) expression was analyzed in 54 biopsy samples from 19 patients. In at least one biopsy specimen from five of the 13 patients with primary lung cancer, FISH or immunohistochemistry detected loss of the 3p14 or 9p21 region. In contrast, no alterations were detected for the same regions in the nine patients without primary lung cancer. Our results support the concept that the normal epithelial surface of large bronchi of patients with lung cancer has molecular changes suggestive of the outgrowth of numerous clonal foci.

Molecular detection of prostate cancer in urine by GSTP1 hypermethylation.

Novel approaches for the early detection and management of prostate cancer are urgently needed. Clonal genetic alterations have been used as targets for the detection of neoplastic cells in bodily fluids from many cancer types. A similar strategy for molecular diagnosis of prostate cancer requires a common and/or early genetic alteration as a specific target for neoplastic prostate cells. Hypermethylation of regulatory sequences at the glutathione S-transferase pi (GSTP1) gene locus is found in the majority (>90%) of primary prostate carcinomas, but not in normal prostatic tissue or other normal tissues. We hypothesized that urine from prostate cancer patients might contain shed neoplastic cells or debris amenable to DNA analysis. Matched specimens of primary tumor, peripheral blood lymphocytes (normal control), and simple voided urine were collected from 28 patients with prostate cancer of a clinical stage amenable to cure. Genomic DNA was isolated from the samples, and the methylation status of GSTP1 was examined in a blinded manner using methylation-specific PCR. Decoding of the results revealed that 22 of 28 (79%) prostate tumors were positive for GSTP1 methylation. In 6 of 22 (27%) cases, the corresponding urine-sediment DNA was positive for GSTP1 methylation, indicating the presence of neoplastic DNA in the urine. Furthermore, there was no case where urine-sediment DNA harbored methylation when the corresponding tumor was negative. Although we only detected GSTP1 methylation in under one-third of voided urine samples, we have demonstrated that molecular diagnosis of prostate neoplasia in urine is feasible. Larger studies focusing on carcinoma size, location in the prostate, and urine collection techniques, as well as more sensitive technology, may lead to the useful application of GSTP1 hypermethylation in prostate cancer diagnosis and management.

Alterations of p14ARF, p53, and p73 genes involved in the E2F-1-mediated apoptotic pathways in non-small cell lung carcinoma.

Overexpression of E2F-1 induces apoptosis by both a p14ARF-p53- and a p73-mediated pathway. p14ARF is the alternate tumor suppressor product of the INK4a/ARF locus that is inactivated frequently in lung carcinogenesis. Because p14ARF stabilizes p53, it has been proposed that the loss of p14ARF is functionally equivalent to a p53 mutation. We have tested this hypothesis by examining the genomic status of the unique exon 1beta of p14ARF in 53 human cell lines and 86 primary non-small cell lung carcinomas and correlated this with previously characterized alterations of p53. Homozygous deletions of p14ARF were detected in 12 of 53 (23%) cell lines and 16 of 86 (19%) primary tumors. A single cell line, but no primary tumors, harbored an intragenic mutation. The deletion of p14ARF was inversely correlated with the loss of p53 in the majority of cell lines (P = 0.02), but this relationship was not maintained among primary tumors (P = 0.5). E2F-1 can also induce p73 via a p53-independent apoptotic pathway. Although we did not observe inactivation of p73 by either mutation or DNA methylation, haploinsufficiency of p73 correlated positively with either p14ARF or p53 mutation or both (P = 0.01) in primary non-small cell lung carcinomas. These data are consistent with the current model of p14ARF and p53 interaction as a complex network rather than a simple linear pathway and indicate a possible role for an E2F-1-mediated failsafe, p53-independent, apoptotic pathway involving p73 in human lung carcinogenesis.