OBJECTIVE

A c. -285C>>A single nucleotide polymorphism (SNP) in the promoter region of the E-cadherin (CDH1) gene, which is a tumor suppressor in gastric cancer (GC), has been shown to decrease gene transcription, but GC case-control studies of this SNP have yielded controversial results. A haplotype study in an Italian population showed that haplotypes based on three SNPs, including the c. -285C>>A, are associated with susceptibility to GC. Hence, the purpose of the present study was to carry out a more comprehensive genetic analysis of CDH1 using haplotype-tagging SNPs (htSNPs) in a Japanese case-control study to identify the CDH1 haplotype associated with susceptibility to GC in a Japanese population.

METHODS

First, 11 SNPs in the CDH1 gene were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis in 30 healthy individuals. Haplotype frequencies were estimated with the expectation-maximization algorithm, and 7 common haplotypes of the CDH1 gene whose frequency was at least 3.3% were identified. Next, 5 htSNPs (c. -285C>>A, c.48+6T>>C, c.164 -3159T>>C, c.2076C>>T, and c.2296 -616G>>C) were genotyped in a hospital-based case-control study of 148 GC patients and 292 age- and gender-matched healthy controls, and haplotype frequencies based on the 5 htSNPs were estimated.

RESULTS

Although none of the 5 htSNPs was related to an overall risk of GC, frequencies of the ATCTG and CTTTG haplotypes were significantly higher and lower, respectively, in the GC cases than in the controls (p<0.05).

CONCLUSIONS

These results suggest that the ATCTG and CTTTG CDH1 haplotypes may be associated with an increased risk and decreased risk, respectively, of GC in the Japanese population.

Stable intraepithelial adhesion complexes are essential for the maintenance of epithelial integrity. Alterations in these complexes are key events in the development and progression of many diseases. One of the major proteins involved in maintaining epithelial cell-cell adhesion is the cell-adhesion junction protein E-cadherin, a member of the cadherin family of transmembrane adhesion proteins. E-cadherin is involved in many cellular processes including morphogenesis, adhesion, recognition, communication and oncogenesis. Inactivation of its adhesive properties is often a key step in tumour progression and metastasis, leading to its recent description as a tumour suppressor gene. Mutations of the E-cadherin gene CDH1 in gastric and mammary cancers have been well documented and reports of transcriptional repression during tumour progression are increasing. This review examines the role of posttranslational truncation of E-cadherin in cancer cells focusing on implications for tumour progression. The various proteins involved in the directed cleavage of E-cadherin and consequences of these truncations are discussed.

Progressive p16 methylation has been associated with metastasis and invasive phenotypes in many cancers. Loss of E-cadherin (CDH1) function contributes to breast cancer progression by promoting cell proliferation, invasion and metastasis. Using methylation-specific PCR, aberrant hypermethylation of p16 and CDH1 in tumor and plasma was analyzed and correlated with levels of serum protein markers, carcinoembryonic antigen (CEA) and carcinoma antigen 15-3 (CA15.3), in 36 patients with invasive ductal breast cancer. Aberrant p16 methylation was found in 11% (4/36) of primary tumors and 8% (3/36) of plasma samples. Aberrant CDH1 methylation was detected in 25% (9/36) of primary tumors and 20% (7/36) of plasma samples. p16 and/or CDH1 hypermethylation was found in 31% (11/36) of primary breast carcinomas and 82% (9/11) of breast cancer patients with tumoral methylation showing identical epigenetic changes in plasma. The 25 patients without tumoral methylation did not show epigenetic changes in the plasma. Tumoral p16 methylation was significantly associated with advanced tumor stage (p=0.028; Fisher's exact test), tumor size (p=0.017) and nodal metastasis (p=0.002). However, p16 methylation in plasma was only associated with nodal metastasis (p=0.012). Altogether, aberrant p16 methylation in plasma and elevated serum CEA level were associated with advanced tumor stage (p=0.033), tumor size (p=0.022) and extensive nodal metastasis (p=0.003). With clinical implications, p16 hypermethylation in plasma and/or raised serum CEA levels may prove useful as diagnostic and prognostic markers for breast cancer.

BACKGROUND

Gastric cancer has a tendency to present at early age in the Mexican population, and it is frequently associated with a family history. A polymorphism at position -160 at the CDH1 promoter region has been reported to lead to transcriptional downregulation of the gene in vitro, with possible increase in the risk of gastric cancer. We evaluated the role of the -160A allele in the risk of gastric cancer in a young Mexican population.

METHODS

Peripheral blood sample of Mexican patients younger than 45 years old with diagnosis of diffuse gastric cancer were obtained. We performed DNA extraction and analyzed the frequencies of -160 promoter polymorphism of E-cadherin gene by polymerase chain reaction-single strand conformational polymorphism. These frequencies were compared with those of healthy controls. The chi2 test for association was used to test differences of the genotype frequencies between normal controls and patients with gastric cancer. Findings were considered significant at P < .05.

RESULTS

The frequency of the -160 A allele was significantly higher (P = .002) in 39 patients with diffuse gastric cancer compared with 78 matched controls. The odds ratio associated with the A-allele was 1.98 for C/A heterozygotes (95% CI 1.01-3.98) and 6.5 for A/A homozygotes (95% CI 2.1-19.6). We found an increased risk of diffuse gastric cancer according to family history, independent of the expression of the polymorphism.

CONCLUSIONS

The -160 C/A polymorphism of the E-cadherin has a direct effect on the risk of diffuse gastric cancer at young age in Mexican population.

The recently identified centrosome protein Nlp (ninein-like protein) is a key regulator in centrosome maturation, which contributes to chromosome segregation and cytokinesis. However, the mechanism(s) controlling Nlp expression remains largely unknown. Here we have shown that Nlp expression is cell cycle-dependent with a peak at G(2)/M transition in human cells. Nlp is a short-lived protein and degraded by the proteasome via the anaphase-promoting cyclosome complex (APC/c) pathway. It interacts with the APC/c through the APC2 or Cdc27 subunits and is ubiquitinated. Following treatment with proteasome inhibitors, its protein level is elevated. Nlp binds in vivo to the degradation-targeting proteins Cdh1 and Cdc20, and overexpression of Cdh1 and Cdc20 enhances Nlp degradation. Using point mutations of the two putative degradation signals in Nlp, we have found that its degradation requires intact KEN-box and D-box. Interestingly, the Lys-Glu-Asn-D-box-mutated Nlp exhibits a much stronger capability of inducing anchorage-independent growth and multinuclearity compared with the wild type Nlp. Taken together, these findings indicate that Nlp expression is cell cycle-dependent and regulated by APC-mediated protein degradation.

BACKGROUND

The E-cadherin (CDH1) gene has been implicated in prostate cancer (PCA) risk, however, the exact mechanism is unknown. Several polymorphisms, such as the C/A variant -160 base pairs from the transcription start site, in the CDH1 gene promoter region have been associated with cancer risk, mainly in European descent populations.

METHODS

We screened the entire coding region and 3.0 kilobases of the CDH1 promoter for polymorphisms in 48 African Americans using dHPLC. Twenty-one (21) polymorphisms were observed. Four polymorphisms, including -160C/A, were genotyped in a genetic association study using incident PCA cases (N = 427) and unaffected controls (N = 337) of similar age from three different ethnic groups consisting of African Americans, Jamaicans, and European Americans.

RESULTS

We observed a significantly higher frequency of the -160A allele among European American PCA patients (27.5%) compared to the control group (19.7%) (P = 0.04). More importantly, among men of European ancestry under the age of 65 who possess the -160 A allele there was over three times increased risk for prostate cancer (P = 0.05). Also, the AACT haplotype bearing the -160A allele was significantly associated with PCA in European Americans (P = 0.04).

CONCLUSIONS

Our data indicate that CDH1 likely is a low-penetrant PCA susceptibility gene, however, population differences in linkage disequilibrium within the CDH1 gene region may influence the effect of susceptibility alleles such as -160A.

Axon growth is an essential event during brain development and is extremely limited due to extrinsic and intrinsic inhibition in the adult brain. The E3 ubiquitin ligase Cdh1-anaphase promoting complex (APC) has emerged as an important intrinsic suppressor of axon growth. In this study, we identify in rodents the E3 ligase Smurf1 as a novel substrate of Cdh1-APC and that Cdh1 targets Smurf1 for degradation in a destruction box-dependent manner. We find that Smurf1 acts downstream of Cdh1-APC in axon growth and that the turnover of RhoA by Smurf1 is important in this process. In addition, we demonstrate that acute knockdown of Smurf1 in vivo in the developing cerebellar cortex results in impaired axonal growth and migration. Finally, we show that a stabilized form of Smurf1 overrides the inhibition of axon growth by myelin. Taken together, we uncovered a Cdh1-APC/Smurf1/RhoA pathway that mediates axonal growth suppression in the developing mammalian brain.

BACKGROUND

Promoter hypermethylation is an alternative mechanism of gene silencing in cancers including gastric carcinoma (GC). Its affects genes with crucial functions as tumor suppressor.

METHODS

DNA methylation in the promoter of P16INK4a, DAPK, retinoic acid receptor β (RARβ2), RASSF1A, and CDH1 genes was investigated in 79 Tunisian patients with GC using methylation-specific PCR.

RESULTS

The methylation frequencies vary from 31.6% for P16INK4a to 65.8% for RARβ2. Hypermethylation of DAPK and CDH1 was associated with tumor grade and age (P = 0.04 and 0.034) respectively, while hypermethylation of RASSF1A correlated with TNM stage (P = 0.027). The distribution of the methylated DNA at P16INK4a, DAPK, and CDH1 promoters were different in the intestinal and diffuse histotypes of GC according to TNM. Moreover, the survival rate of patients with P16INK4a methylated status was shorter than that of patients with the unmethylated status (P log rank = 0.009). On the other hand, the hypermethylation of RARβ2 correlated with COX-2 expression (P = 0.001).

CONCLUSIONS

We showed that methylation of P16INK4a is predictive of poor prognosis and could be a useful marker. Moreover, the association between RARβ2 methylation and COX-2 expression suggests a functional link between these two proteins in gastric carcinogenesis.

Liver kinase B1 (LKB1), also known as serine/threonine kinase 11 (STK11), has been identified as a tumor suppressor in many cancers including breast. Low LKB1 expression has been associated with poor prognosis of breast cancer patients, and we report here a significant association between loss of LKB1 expression and reduced patient survival specifically in the basal subtype of breast cancer. Owing to the aggressive nature of the basal subtype as evidenced by high incidences of metastasis, the purpose of this study was to determine if LKB1 expression could regulate the invasive and metastatic properties of this specific breast cancer subtype. Induction of LKB1 expression in basal-like breast cancer (BLBC)/triple-negative breast cancer cell lines, MDA-MB-231 and BT-549, inhibited invasiveness in vitro and lung metastatic burden in an orthotopic xenograft model. Further analysis of BLBC cells overexpressing LKB1 by unbiased whole transcriptomics (RNA-sequencing) revealed striking regulation of metastasis-associated pathways, including cell adhesion, extracellular matrix remodeling, and epithelial-to-mesenchymal transition (EMT). In addition, LKB1 overexpression inhibited EMT-associated genes (CDH2, Vimentin, Twist) and induced the epithelial cell marker CDH1, indicating reversal of the EMT phenotype in the MDA-MB-231 cells. We further demonstrated marked inhibition of matrix metalloproteinase 1 expression and activity via regulation of c-Jun through inhibition of p38 signaling in LKB1-expressing cells. Taken together, these data support future development of LKB1 inducing therapeutics for the suppression of invasion and metastasis of BLBC.

In prostate and other epithelial cancers, E-cadherin (CDH1) is downregulated inappropriately by DNA methylation to promote an invasive phenotype. Though cancer frequently involves a reawakening of developmental signaling pathways, whether DNA methylation of Cdh1 occurs during organogenesis has not been determined. Here we show that DNA methylation of Cdh1 mediates outgrowth of developing prostate ducts. During the three-day gestational window leading up to and including prostate ductal initiation, Cdh1 promoter methylation increases and its mRNA and protein abundance decreases in epithelium giving rise to prostatic buds. DNA methylation is required for prostate specification, ductal outgrowth, and branching morphogenesis. All three endpoints are impaired by a DNA methylation inhibitor, which also decreases Cdh1 promoter methylation and increases Cdh1 mRNA and protein abundance. A CDH1 function-blocking antibody restores prostatic identity, bud outgrowth, and potentiates epithelial differentiation in the presence of the DNA methylation inhibitor. This is the first study to mechanistically link acquired changes in DNA methylation to the normal process of prostate organogenesis. We propose a novel mechanism whereby Cdh1 promoter methylation restricts Cdh1 abundance in developing prostate epithelium to create a permissive environment for prostatic bud outgrowth. Thus, DNA methylation primes the prostate primordium to respond to developmental cues mediating outgrowth, differentiation and maturation of the ductal network.

DNA methylation is one of the major epigenetic changes in human cancers, leading to silencing of tumor suppressor genes, with a pathogenetic role in tumor development and progression in myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). Methylation of key promoter regions, induced by cytotoxic therapy together with complex genetic changes, is important in the biology of therapy-related myeloid neoplasms (t-MN). We were interested in the characterization of the methylation pattern of AML and MDS de novo and therapy-related. We studied 385 patients (179 females, 206 males), of a median age of 66 years (range 16-98 years). There were 105 MDS, 208 de novo AML and 72 t-MN (45 MDS and 27 AML). Using a methylation-specific PCR, we studied the promoter methylation status of E-cadherin (CDH1), TSP1 and DAP-Kinase 1. These genes have been shown to be involved in the malignant transformation, interfering with angiogenesis, interaction with micro-environment, apoptosis and xenobiotic detoxification. We found no associations between promoter hypermethylation and gender or age at the time of initial diagnosis. In patients with MDS, there were no associations between hypermethylation and clinical characteristics, including IPSS score, WHO classification and cytogenetics. DAPK1 was more frequently methylated in t-MDS/AML when compared to de novo MDS and AML (39% vs 15.3% and 24.4%, p=0.0001), while methylation of CDH1 was similar in t-MDS/AML and AML (51% and 53.4%), but less frequent in de novo MDS (29%) (p=0.003). In the t-MDS/AML group, we found that the methylation pattern appeared to be related to the primary tumor, with DAPK1 more frequently methylated in patients with a previous lymphoproliferative disease (75% vs 32%, p=0.006). On the other hand, methylation of CDH1 was associated to radiotherapy for the primary malignancy (84.5% vs 38%, p=0.003). TSP1 hypermethylation was rare and not characteristic of t-MDS/AML. In 177 patients studied for concurrent methylation of several promoters, t-MN and AML de novo were significantly more frequently hypermethylated in 2 or more promoter regions than de novo MDS (20% vs 12.4%, p<0.001). Chemotherapy and individual genetic predisposition have a role in t-MDS/AML development, the identification of specific epigenetic modifications may explain complexity and genomic instability of these diseases and give the basis for targeted-therapy. The significant association with previous malignancy subtypes may underlie a likely susceptibility to methylation of specific targets and a role for constitutional epimutations as predisposing factors for the development of therapy-related myeloid neoplasm.

Receptor-associated protein 80 (RAP80) is a component of the BRCA1-A complex that recruits BRCA1 to DNA damage sites in the DNA damage-induced ubiquitin signaling pathway. RAP80-depleted cells showed defective G(2)-M phase checkpoint control. In this study, we show that RAP80 protein levels fluctuate during the cell cycle. Its expression level peaked in the G(2) phase and declined during mitosis and progression into the G(1) phase. Also, RAP80 is polyubiquitinated and degraded by the anaphase-promoting complex (APC/C)(Cdc20) or (APC/C)(Cdh1). Consistent with this, knockdown of Cdc20 or Cdh1 expression by transfecting with small interfering RNAs blocked RAP80 degradation during mitosis or the G(1) phase, respectively. A conserved destruction box (D box) in RAP80 affected its stability and ubiquitination, which was dependent on APC/cyclosome(Cdc20) (C(Cdc20)) or APC/cyclosome(Cdh1) (C(Cdh1)). In addition, overexpression of RAP80 destruction box1 deletion mutant attenuated mitotic progression. Thus, APC/C(Cdc20) or APC/C(Cdh1) complexes regulate RAP80 stability during mitosis to the G(1) phase, and these events are critical for a novel function of RAP80 in mitotic progression.

Anaphase-promoting complex/cyclosome (APC/C), an E3 ubiquitin ligase incorporated with Cdh1 and/or Cdc20 recognizes and interacts with specific substrates, and faithfully orchestrates the proper cell cycle events by targeting proteins for proteasomal degradation. Experimental identification of APC/C substrates is largely dependent on the discovery of APC/C recognition motifs, e.g., the D-box and KEN-box. Although a number of either stringent or loosely defined motifs proposed, these motif patterns are only of limited use due to their insufficient powers of prediction. We report the development of a novel GPS-ARM software package which is useful for the prediction of D-boxes and KEN-boxes in proteins. Using experimentally identified D-boxes and KEN-boxes as the training data sets, a previously developed GPS (Group-based Prediction System) algorithm was adopted. By extensive evaluation and comparison, the GPS-ARM performance was found to be much better than the one using simple motifs. With this powerful tool, we predicted 4,841 potential D-boxes in 3,832 proteins and 1,632 potential KEN-boxes in 1,403 proteins from H. sapiens, while further statistical analysis suggested that both the D-box and KEN-box proteins are involved in a broad spectrum of biological processes beyond the cell cycle. In addition, with the co-localization information, we predicted hundreds of mitosis-specific APC/C substrates with high confidence. As the first computational tool for the prediction of APC/C-mediated degradation, GPS-ARM is a useful tool for information to be used in further experimental investigations. The GPS-ARM is freely accessible for academic researchers at: http://arm.biocuckoo.org.

The anaphase-promoting complex (APC) is a central regulator of the eukaryotic cell cycle and functions as an E3 ubiquitin protein ligase to catalyze the ubiquitination of a number of cell cycle regulatory proteins. The APC contains at least 13 subunits in addition to two activator subunits, Cdc20 and Cdh1, that associate with the APC in a cell cycle-dependent manner. This chapter describes methods for preparation and assay of the APC from Saccharomyces cerevisiae. Highly active APC is purified from cells expressing Cdc16 fused with a tandem affinity purification (TAP) tag. Enzymatically active APC is achieved upon addition of recombinant Cdc20 or Cdh1 together with E1, Ubc4, ATP, and ubiquitin. Activity assays toward several endogenous substrates, including Clb2 and Pds1, are described. In addition, methods for observation of APC-coactivator and APC-substrate complexes by native gel electrophoresis are described.

The aim of this study was to verify genetic and epigenetic alterations in gastric cancer patients from Pará state, northern Brazil.

METHODS

Exon 11 of KIT and two promoter polymorphisms (-160 C/A and -347 G/GA) of the E-cadherin gene (CDH1), and their correlation with the promoter methylation status were analyzed.

RESULTS

No genetic alterations in KIT were found. Promoter polymorphisms revealed an increased probability of developing gastric cancer, especially of the diffuse-type, in patients carrying -160 A and -347 GA alleles. Analyses of CDH1 methylation suggested a significant difference between hypermethylated and non-hypermethylated samples, with a positive association between the -160 A allele and hypermethylation.

CONCLUSIONS

Our results suggest that -160 A and -347 GA polymorphisms may increase the chance of developing gastric cancer in the studied population and that -160 A polymorphism seems to be related to the hypermethylation pattern of the promoter region of CDH1.

Aberrant methylation in promoter-associated CpG islands has been recognized as a major mechanism for tumor suppressor gene silencing in several malignancies. We determined the methylation status of nine tumor suppressor genes in 68 newly diagnosed MM patients by methylation-specific PCR. The frequency of promoter hypermethylation for individual genes was: CDH1, 50%; p16 INK4a, 42.8%; p15 INK4b, 16.2%; SHP1, 14.7%; ER and BNIP3, 13.2%; RAR beta, 11.8%; DAPK 5.9%; and MGMT 0%. Overall, 79% of patients presented at least one hypermethylated gene. By univariate analysis, hypermethylation of DAPK (P < 0.001) and RAR beta (P = 0.01) genes were identified as adverse prognostic features. Median OS of patients with hypermethylation in DAPK (4 months) and RAR beta (34 months) was significantly lower than in patients without hypermethylation (median survival not reached), with values of P < 0.001 and P = 0.01, respectively. Our data suggest that DAPK and RAR beta hypermethylation are adverse prognostic factors in MM. The relevance of these findings as poor prognosis indicators requires confirmation in a larger sample with longer follow-ups.

OBJECTIVE

To investigate the clinical value of CDH1 methylation in preoperative peritoneal washes (PPW) from gastric cancer patients.

METHODS

CDH1 methylation was detected by real-time methylation specific-PCR in tumor tissues and corresponding PPW from 92 gastric cancer patients, gastric mucosa from 40 chronic gastritis patients and 48 normal persons.

RESULTS

CDH1 methylation was found in 75 of 92 (81.5%) gastric cancer tissues, which significantly correlated with size, growth pattern, differentiation, lymphatic invasion, venous invasion, invasion depth, lymph node metastasis, distant metastasis, and TNM stage of tumor (all P < 0.05), but its relationship to age, gender, tumor site, and H. pylori infection was not found (all P>> 0.05). The percentage of CDH1 methylation in PPW was 48.9%, of which the Aζ value of ROC curve was 0.8 compared to that in gastric cancer tissues. Kaplan-Meier analysis showed that there was a significant difference in disease-free survival (DFS) between the patients with or without methylated CDH1 in their PPW (χ(2) = 109.64, P < 0.000). Cox regression analysis revealed CDH1 methylation in PPW was an independent risk factor for gastric cancer patients, with a remarkable decrease in DFS after postoperative 30 months.

CONCLUSIONS

Methylated CDH1 in PPW predicts poor prognosis for gastric cancer patients.

Transcriptional silencing by CpG island hypermethylation plays a critical role in endometrial carcinogenesis. In a collection of benign, premalignant and malignant endometrial lesions, a methylation profile of a complete gene panel, such steroid receptors (ERα, PR), DNA mismatch repair (hMLH1), tumor-suppressor genes (CDKN2A/P16 and CDH1/E-CADHERIN) and WNT pathway inhibitors (SFRP1, SFRP2, SFRP4, SFRP5) was investigated in order to demonstrate their pathogenetic role in endometrial lesions. Our results indicate that gene hypermethylation may be an early event in endometrial endometrioid tumorigenesis. Particularly, ERα, PR, hMLH1, CDKN2A/P16, SFRP1, SFRP2 and SFRP5 revealed a promoter methylation status in endometrioid carcinoma, whereas SFRP4 showed demethylation in cancer. P53 immunostaining showed weak-focal protein expression level both in hyperplasic lesions and in endometrioid cancer. Non-endometrioid cancers showed very low levels of epigenetic methylations, but strong P53 protein positivity. Fisher exact test revealed a statistically significant association between hMLH1, CDKN2A/P16 and SFRP1 genes methylation and endometrioid carcinomas and between hMLH1 gene methylation and peritumoral endometrium (p < 0.05). Our data confirm that the methylation profile of the peritumoral endometrium is different from the altered molecular background of benign endometrial polyps and hyperplasias. Therefore, our findings suggest that the methylation of hMLH1, CDKN2A/P16 and SFRP1 may clearly distinguish between benign and malignant lesions. Finally, this study assessed that the use of an epigenetic fingerprint may improve the current diagnostic tools for a better clinical management of endometrial lesions.

The E-cadherin (CDH1) gene has been associated with prostate carcinogenesis. The C/A polymorphism--160 base pairs relative to the transcription start site has been shown to decrease gene transcription. We analyzed the association between this polymorphism and the risk of sporadic, familial (2 close relatives) and hereditary (3 or more close relatives) prostate cancer. We combined data from 3 population-based epidemiologic studies in Sweden encompassing altogether 1,036 prostate cancer cases and 669 controls that were genotyped for the short nucleotide polymorphism. Odds ratios with 95% confidence intervals were estimated through unconditional logistic regression. We found no significant association between the A-allele and sporadic (OR = 1.0; 95% CI = 0.8-1.2) or familial (OR = 1.4; 95% CI = 0.9-2.2) prostate cancer. In contrast, risk of hereditary cancer was increased among heterozygote CA carriers (OR = 1.7; 95% CI = 1.0-2.7) and particularly among homozygote AA carriers (OR = 2.6; 95% CI = 1.4-4.9). Our data indicate that the -160 single nucleotide polymorphism in CDH1 is a low-penetrant prostate cancer susceptibility gene that might explain a proportion of familial and notably hereditary prostate cancer.

OBJECTIVE

The predictive value of free cancer cells in the peritoneal fluid of patients with colorectal cancer (CRC) remain to be elucidated. The aim of this study was to determine the prognostic relevance of the methylation of tumor-related genes detected in the peritoneal lavage fluid (PLF) of patients undergoing a resection for CRC.

METHODS

The promoter methylation pattern of four target genes, CDH1, CDKN2A (p16), MGMT, and APC, was examined in 51 primary CRC and corresponding matched PLF DNA. The relative methylation levels of these genes in primary CRC tissue and paired PLF were assessed by quantitative methylation-specific polymerase chain reaction (QMSP).

RESULTS

An aberrant methylation of at least one gene was found in 45 of 51 (88%) primary tumors. In matched PLF specimens, the frequencies of aberrant promoter methylation detected for each marker were 16% for CDH1, 2% for p16, 4% for MGMT and 24% for APC. Patients with PLF demonstrating the methylation of more than one of these four target genes demonstrated significantly shorter relapse-free survival.

CONCLUSIONS

These findings suggest that disseminated tumor cells in PLF detected by QMSP may correlate with the postoperative clinical course of patients undergoing curative surgery for CRC.

We have combined data from case control studies designed to test the hypothesis that the c-160a promotor polymorphism in the gene coding for the cell adhesion molecule E-cadherin (CDH1) is associated with stomach cancer. A total of 899 individuals (433 patients and 466 controls) were analyzed. The genotype frequencies did not differ significantly between cases and controls, and the genotype-specific risks were not significantly different from unity, with an odds ratio for heterozygotes compared with the common homozygote of 1.3 (95% CI 0.98-1.8) and 1.2 (0.68-2.0) for rare homozygotes compared with common homozygotes. We found no evidence for differences in risk for the intestinal- and diffuse-type histopathologic subgroups.

Disseminated melanoma is an aggressive disease with fatal outcome. Better understanding of the underlying biology is needed to find effective treatment. We applied microarray-based comparative genomic hybridization, gene expression and CpG island methylation analysis of primary tumors and multiple metastases from five melanoma patients with the aim of analyzing the molecular patterns of melanoma progression. Epigenetic profiling showed that the multiple metastases after a single primary melanoma share similar methylation patterns for many genes, although differences in methylation between the lesions were evident for several genes, example, PTEN, TFAP2C, and RARB. In addition, DNA copy number and global gene expression profiles of tumors from individual patients were highly similar, confirming common origin of metastases. Some of the identified genomic aberrations, for example, gain of chromosome 6p and loss of chromosomes 6q and 10, persisted during progression, indicating early changes highly important for melanoma development. Homozygous deletions at 3p26.1 and 6q23.2-q23.3 appeared in two consecutive metastases originating from the same primary tumor, respectively, in a mutually exclusive manner that provides evidence for two genetically different subclones. However, in another case, the similarity of the copy number aberrations in subsequent metastatic lesions suggests sequential metastatic development through the clonal evolution. These data are further corroborated by a switch in CDH1 and CDH2 expression between metastases from the same patient. In conclusion, our results provide evidence for different models of metastatic progression in melanoma.

Metaphase of mitosis is brought about in all eukaryotes by activation of cylin-dependent kinase (Cdk1), whereas exit from mitosis requires down-regulation of Cdk1 activity and dephosphorylation of its target proteins. In budding yeast, the completion of mitotic exit requires the release and activation of the Cdc14 protein-phosphatase, which is kept inactive in the nucleolus during most of the cell cycle. Activation of Cdc14 is controlled by two regulatory networks called FEAR (Cdc fourteen early anaphase release) and MEN (mitotic exit network). We have shown recently that the anaphase promoting protease (separase) is essential for Cdc14 activation, thereby it makes mitotic exit dependent on execution of anaphase. Based on this finding, we have proposed a new model for mitotic exit in budding yeast. Here we explain the essence of the model by phaseplane analysis, which reveals two underlying bistable switches in the regulatory network. One bistable switch is caused by mutual activation (positive feedback) between Cdc14 activating MEN and Cdc14 itself. The mitosis-inducing Cdk1 activity inhibits the activation of this positive feedback loop and thereby controlling this switch. The other irreversible switch is generated by a double-negative feedback (mutual antagonism) between mitosis inducing Cdk1 activity and its degradation machinery (APC(Cdh1)). The Cdc14 phosphatase helps turning this switch in favor of APC(Cdh1) side. Both of these bistable switches have characteristic thresholds, the first one for Cdk1 activity, while the second for Cdc14 activity. We show that the physiological behaviors of certain cell cycle mutants are suggestive for those Cdk1 and Cdc14 thresholds. The two bistable switches turn on in a well-defined order. In this paper, we explain how the activation of Cdc20 (which causes the activation of separase and a decrease of Cdk1 kinase activity) provides an initial trigger for the activation of the MEN-Cdc14 positive feedback loops, which in turn, flips the second irreversible Cdk-APC(Cdh1) switch on the APC(Cdh1) side).

Proteins associated with the centrosome play key roles in mitotic progression in mammalian cells. The activity of Cdk1-opposing phosphatases at the centrosome must be inhibited during early mitosis to prevent premature dephosphorylation of Cdh1-an activator of the ubiquitin ligase anaphase-promoting complex/cyclosome-and the consequent premature degradation of mitotic activators. In this paper, we show that reversible oxidative inactivation of centrosome-bound protein phosphatases such as Cdc14B by H2O2 is likely responsible for this inhibition. The intracellular concentration of H2O2 increases as the cell cycle progresses. Whereas the centrosome is shielded from H2O2 through its association with the H2O2-eliminating enzyme peroxiredoxin I (PrxI) during interphase, the centrosome-associated PrxI is selectively inactivated through phosphorylation by Cdk1 during early mitosis, thereby exposing the centrosome to H2O2 and facilitating inactivation of centrosome-bound phosphatases. Dephosphorylation of PrxI by okadaic acid-sensitive phosphatases during late mitosis again shields the centrosome from H2O2 and thereby allows the reactivation of Cdk1-opposing phosphatases at the organelle.