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PubMed2004

Expression of the p65 gene in patients with colorectal cancer: comparison with some histological typing, grading and clinical staging.

AIMS: P65 protein/gene is a potential, non-specific tumour marker expressed by different types of neoplasms. In this study p65 gene expression was estimated in a group of colorectal cancers and compared with some histological features, grading and clinical staging of the neoplasms to assess its role as a prognostic marker for colorectal cancer. METHODS: 109 pairs of frozen samples of colorectal carcinomas and adjacent normal colorectal mucosa and four samples of tissue from patients without neoplastic diseases were analysed by means of RT-PCR. RESULTS: Expression of p65 gene was found in 51 out of 109 cases of colorectal cancers. For 19 of them expression of examined gene was observed both in cancer and corresponding healthy mucosa. p65 Gene expression was associated with more advanced tumours (T3, T4; p=0.0003) with metastases to lymph nodes (N1, N2; p=0.0003) and distant metastases (p=0.0005). We did not find association between the age, gender, tumour localization, histological type and p65 gene expression. CONCLUSIONS: p65 Gene expression in primary tumour tissue is associated with poor prognosis for the patients with colorectal cancer in this series.

Aged↗
PubMed2001

Heterogeneity of DNA methylation status analyzed by bisulfite-PCR-SSCP and correlation with clinico-pathological characteristics in colorectal cancer.

Aberrant DNA methylation has been identified as an important mechanism for inactivation of tumor suppressor genes and mismatch repair genes during carcinogenesis. We used bisulfite treatment and the PCR-single strand conformation polymorphism (SSCP) (BiPS) technique to analyze methylation status of the promoter regions of the hMLH1, p16, and HIC1 genes in several cancer cell lines and colorectal cancer tissues. The methylation of the hMLH1, p16 and HIC1 genes was observed in 2, 8, and 13 of 13 cancer cell lines, respectively. The SSCP for p16 and HIC1 in each of the methylation-positive cell lines were similar, indicating relative homogeneity of methylation status and complete methylation in the cell lines. Methylation was observed in 8, 5, and 21 of 25 colorectal cancer tissues for the hMLH1, p16, and HIC1 genes, respectively. The methylated bands revealed by BiPS analysis of the hMLH1 gene were homogeneous, whereas those of the p16 and HIC1 genes were different in each case. The methylation of the promoter region of the HIC1 gene in colorectal cancer was observed most frequently and could serve as a sensitive marker for colorectal cancer. Methylation status of the hMLH1 and p16 gene promoters was correlated with microsatellite instability status, tumor location, and differentiation but not with K-ras mutation or allelic loss of p53.

Adaptor Proteins, Signal Transducing↗
PubMed2005

DMBT1 expression and glycosylation during the adenoma-carcinoma sequence in colorectal cancer.

The gene DMBT1 (deleted in malignant brain tumour-1) has been proposed to play a role in brain and epithelial cancer, but shows unusual features for a classical tumour-suppressor gene. On the one hand, DMBT1 has been linked to mucosal protection, whereas, on the other, it potentially plays a role in epithelial differentiation. Thus its function in a particular tissue is of mechanistic importance for its role in cancer. Because the former function requires secretion to the lumen and the latter function may depend on its presence in the extracellular matrix, we decided to investigate DMBT1 expression, location and its mode of secretion during malignant transformation in colorectal cancer. Using human colorectal PC/AA cell lines and tissue sections from individual patients, we have examined the expression of DMBT1 and its glycosylation in the adenoma-carcinoma sequence leading to the adenocarcinoma phenotype.

Adenocarcinoma↗
PubMed1991

Identification of locus-specific DNA-binding factors for the regulation of HLA class-I genes in human colorectal cancer.

The expression of HLA class-I mRNA in human colorectal cancer cell lines was studied. Locus-specific down-regulation of HLA class-I mRNA could be demonstrated in some of the human colorectal lines. This transcriptional suppression of HLA mRNA, however, was not a result of genetic alterations in the HLA structural genes. The transcription of the HLA class-I genes in the HLA-deficient cell lines could be induced by the addition of human recombinant gamma-IFN. In this report, we have employed these human colorectal cell lines to study locus-specific transcriptional regulation of HLA class-I gene expression. Our results demonstrate that the locus-specific suppression of HLA gene expression in human colorectal cell lines is mediated by the loss of certain DNA-binding transcription factors which act in a locus-specific manner. Our conclusion is further supported by experiments which showed that exogenously introduced HLA-CAT DNA constructs were also regulated in a locus-specific fashion when assayed by in vitro functional assays using these human colorectal cell lines.

Adenocarcinoma↗
PubMed2006

Mutations within Wnt pathway genes in sporadic colorectal cancers and cell lines.

Wnt signaling pathway activation via mutation of genetic components, commonly adenomatous polyposis coli (APC), has a major role in colorectal cancer (CRC). Most components have not been assessed for mutation in sporadic CRC. We have analyzed AXIN2, CK1alpha, DKK1, GSK-3beta, SOX17, LRP6 and PPP2R1B, beta-catenin and APC in a collection of sporadic CRCs (n = 47) and CRC cell lines (CLs; n = 26). The CRC set was enriched for microsatellite unstable cancers (MSI+, 30%, 14/47). Somatic mutation was not found in CK1alpha, DKK1, LRP6, beta-catenin or GSK-3beta; but heterozygous frame-shift mutations, and an in-frame deletion mutation were detected in exon 7 of AXIN2 (CRCs, 11%, 5/47; CLs, 8%, 2/26). Our data refute a previous suggestion that a CRC-related mutational hot-spot occurred in the Huntington elongation A subunit TOR (HEAT) repeat 2 of PPP2R1B; this "hotspot" is, more likely, a rare germline polymorphism. An early investigation proposing a high mutational frequency in HEAT repeat 13 was not substantiated. A heterozygous SOX17 mutation (L194P) was also found in a cell line. APC gene mutations were identified in 64% (30/47) of cancers and 7% of these (2/30) had an additional mutation in another Wnt gene. Overall, 70% (33/47) of CRCs had a somatic mutation in a Wnt pathway gene. The number of tumors containing such a mutation was not significantly higher in MSI+ (57%, 8/14) compared to MSI- (76%, 25/33) cancers (p = 0.3, Fisher's exact test); APC mutation was significantly increased in the MSI- subgroup (p = 0.02, Fisher's exact test). Further, mutational screening of other Wnt pathway genes is warranted.

Base Sequence↗
PubMed1999

Expression of B7 costimulation molecules by colorectal cancer cells reducestumorigenicity and induces anti-tumor immunity.

AIM:To study the tumorigenicity of colorectal cancer cells transfected with B7 gene and the anti-tumor immunity induced by B7 gene modified colorectal cancer cells.METHODS:B7 gene was transfected into mouse colon cancer cell line CMT93.The transfectants were selected in DMEM containing 800mg/L G418, and B7 molecules were detected by immunohistochemistry.Experiments in vivo include: (1)5X10(6) B7(+) CMT93 cells were inoculated into the back of C57BL/6 mice subcutanously to determine their tumorigenicity (n = 4). As control, wild type CMT93 cells were inoculated the same as the experimental group (n= 3). (2) The mice primed by B7(+) CMT93 cells whose tumors vanished were rechallenged with wild type CMT93 to observe the immune protection of these mice against the wild type CMT93 (n = 4). Non-primed 4 native mice inoculated with wild type CMT93 were used as control.With in vivo cytotoxicity assay, the mice were immunized with B7 (+) CMT93 or the wild type CMT93 by intraperitoneal injection (n = 4X2). The spleen cells and the abdominal cavity infiltrating lymphocytes were obtained and cultured for two days. Cytotoxicity of these cells against the B7 gene modified or wild type CMT93 was detected by MTT assay.RESULTS:B7 high expression clones were obtained after the transfection of the B7 gene into CMT93 cells by electroporation. Immunohistochemistry results showed mainly membrance staining and partly cytoplasm staining in B7 gene transfected CMT93 cells. in vivo experiments: (1)After the inoculation of the B7(+) CMT93 cells in the back of C57BL/6 mice, they lost their tumorigenicity greatly (P < 0.01). All the small tumors growing in the early period in the experimental group vanished in one month, and the tumors in control group grew progressively. (2) No tumors were found in all 4 mice primed by B7(+) CMT93 cells after they were rechallenged with wild type CMT93. In the control group all mice had grown tumors (P < 0.05). In vitro cytotoxicity assay, the CTLs induced by B7(+) CMT93 had a higher cytotoxity against the wild type CMT93 than that induced by wild type CMT93 (P < 0.05), and the cytotoxity of CTLs induced by B7(+) CMT93 against B7(+) CMT93 cells was higher than that against wild type CMT93 cells (P < 0.05).CONCLUSION:The results suggest that the expression of costimulation B7 molecules by colorectal cancer cells can decrease their tumorigenicity greatly, and the B7 molecule can augment the activation of the CTLs against colorectal cancer, and it plays an important role in CTL effector function as well.

Journal Article↗
PubMed1999

Higher frequency of Smad4 gene mutation in human colorectal cancer with distant metastasis.

We have previously detected an increased frequency of loss of heterozygosity (LOH) on chromosome 18q during progression of colorectal carcinomas. To clarify the target of 18qLOH, mutation of Smad4 and Smad2 genes was analysed in 176 colorectal tumors with different stages, including liver metastasis, from 111 sporadic, 52 familial adenomatous polyposis (FAP) and nine hereditary nonpolyposis colorectal cancer (HNPCC) patients. Mutation of other Smad gene families in the TGF-beta signaling pathway was also examined. Twenty-one Smad4 mutations and one Smad2 mutation were detected, whereas mutation of Smad3, 6 and 7 genes was not detected. Smad4 mutations included seven frameshift, one inframe deletion, four nonsense and nine missense mutations, 95% of which resulted in alteration of Smad4 protein regions included in homo-oligomer and hetero-oligomer formation. Frequencies of tumors with Smad4 mutation were 0/40 (0%) in adenoma, 4/39 (10%) in intramucosal carcinoma, 3/44 (7%) in primary invasive carcinoma without distant metastasis, 6/17 (35%) in primary invasive carcinoma with distant metastasis, and 11/36 (31%) in distant metastasis (metastatic/non-metastatic: P=0.006 approximately 0.01). Loss of the other allele was observed in 19 of 20 (95%) invasive and metastasized carcinomas with Smad4 mutations. In four cases both primary and metastasized carcinomas in the same patients showed the same mutations. The present results suggest that Smad4 gene is one of true targets of 18qLOH, and that its inactivation is involved in advanced stages, such as distant metastasis, in human colorectal carcinogenesis.

Colorectal Neoplasms↗
PubMed2005

Web-based data warehouse on gene expression in human colorectal cancer.

Based on biomedical literature databases, we tried a first step for constructing a gene expression "data warehouse" specific to human colorectal cancer (CRC). Results of genome-wide transcriptomic research were available from 12 studies, using various technologies, namely, SAGE, cDNA and oligonucleotide arrays, and adaptor-tagged amplification. Three studies analyzed CRC cell lines and nine studies of human samples. The total number of patients was 144. Out of 982 up- or down-regulated genes, 863 (88%) were found to be differentially expressed in a single study, 88 in two studies, 22 in three studies, 7 in four studies, and only 2 genes in six studies. Eight large-scale proteomics studies were published in CRC, using 2-D-, SDS- or free-flow electrophoresis, involving only 11 patients. Out of 408 differentially expressed proteins, 339 (83%) were found to be differentially expressed only in a single study, 16 in three studies, 10 in four studies, 3 in five, and 1 in eight studies. Confirmation at proteome level of results obtained with large-scale transcriptomics studies was possible in 25%. This proportion was higher (67%) for reproducing proteome results using transcriptomics technologies. Obviously, reproducibility and overlapping between published gene expression results at proteome and transcriptome level are low in human CRC. Thus, the development of standardized processes for collecting samples, storing, retrieving, and querying gene expression data obtained with different technologies is of central importance in translational research.

Colorectal Neoplasms↗
PubMed2006

Epigenetic remodeling in colorectal cancer results in coordinate gene suppression across an entire chromosome band.

We report a new mechanism in carcinogenesis involving coordinate long-range epigenetic gene silencing. Epigenetic silencing in cancer has always been envisaged as a local event silencing discrete genes. However, in this study of silencing in colorectal cancer, we found common repression of the entire 4-Mb band of chromosome 2q.14.2, associated with global methylation of histone H3 Lys9. DNA hypermethylation within the repressed genomic neighborhood was localized to three separate enriched CpG island 'suburbs', with the largest hypermethylated suburb spanning 1 Mb. These data change our understanding of epigenetic gene silencing in cancer cells: namely, epigenetic silencing can span large regions of the chromosome, and both DNA-methylated and neighboring unmethylated genes can be coordinately suppressed by global changes in histone modification. We propose that loss of gene expression can occur through long-range epigenetic silencing, with similar implications as loss of heterozygosity in cancer.

Chromatin↗
PubMedDate not supplied

Genomic PCR-SSCP analysis of the metastasis associated NM23-H1 (NME1) gene: a study on colorectal cancer.

To facilitate further mutational analysis of NM13-H1, a human metastasis suppressor gene, we have established its genomic organization. NM23-H1 is composed of five exons, spanning a genomic DNA fragment of 10 kb. Using oligonucleotide primers flanking each exon, PCR-SSCP analysis was performed on genomic DNAs of healthy individuals. A common polymorphism, a C to T transition, was detected 30 nucleotides upstream from the 5' splice site flanking exon 1. As NM23-H1 allele loss and altered expression have been reported in colorectal cancer, genomic DNAs of 20 colorectal tumors were analyzed for the presence of gene-specific mutations by PCR-SSCP: no abnormal sequences were detected within the coding and splice site regions of the NM23-H1 gene. This finding suggests that NM23-H1 mutations are rare events in human colorectal cancer.

Base Sequence↗
PubMed1999

Genetic testing and counseling for hereditary forms of colorectal cancer.

The discovery of genes responsible for inherited forms of colorectal cancer have the potential to improve cancer risk assessment and counseling. Germline mutations (nonsense, frameshift) of APC are associated with familial adenomatous polyposis, an autosomal dominant syndrome, clinically characterized by young onset, hundreds of adenomatous polyps in the colon, and increased risk for extracolonic tumors. Mutations in APC are also associated with forms of attenuated familial adenomatous polyposis. Germline mutations in five mismatch repair related genes (hMSH2, hMLH1, hMSH6, hPMS1, and hPMS2) cause hereditary nonpolyposis colorectal cancer and are associated with increased risk of somatic genetic alterations and high DNA microsatellite instability. Hereditary nonpolyposis colorectal cancer is characterized by young onset colorectal cancer, proximal colon location, and increased risk of extracolonic cancers. A missense mutation in APC (I1307K) is associated with some familial colorectal cancer in Ashkenazic Jews. For persons at risk for hereditary forms of colorectal cancer, testing algorithms and gene test interpretations depend on identification of the pedigree germline gene mutation. Careful evaluation of the kindred for characteristic aggregation of tumor types among affected individuals and the availability of affected persons for testing are important issues in implementing genetic testing and follow-up management. Case reports illustrate the importance of genetic counseling as a component of cancer genetic risk assessment. The genetic counseling process includes exploration of patient risk perception, sources of anxiety related to cancer risk, patient education (specific cancer-related issues, prevention/intervention options), discussion of possible gene test options, test limitations, and consequences of various gene test outcomes.

Adenomatous Polyposis Coli↗
PubMed1999

The effect of dietary folate on Apc and p53 mutations in the dimethylhydrazine rat model of colorectal cancer.

Dietary inadequacy of folate enhances and folate supplementation suppresses colorectal carcinogenesis in the dimethylhydrazine rat model. Folate is an essential factor for DNA methylation and the de novo biosynthesis of nucleotides, aberrations of which play important roles in mutagenesis. This study investigated whether the mutational hot spots of the Apc and p53 genes for human colorectal cancer are mutated in dimethylhydrazine-induced colorectal neoplasms and whether dietary folate can modulate mutations in these regions. Rats were fed diets containing 0, 2 (basal requirement), 8 or 40 mg folate/kg diet. Five weeks after diet initiation, dimethylhydrazine was injected weekly for 15 weeks. Mutations were determined by direct sequencing in 11 low and seven high grade dysplasias and 13 invasive adenocarcinomas. A total of six Apc mutations were found in four dysplastic and carcinomatous lesions: two in two low grade dysplasias, two in one high grade dysplasia and two in one adenocarcinoma. All mutations were single base substitutions, four of which were A:T-->G:C transitions. Five of the six mutations were located upstream from the region corresponding to the human APC mutation cluster region. Dietary folate had no effect on the frequency and type of Apc mutations. No mutations were detected in exons 5-9 of the p53 gene in neoplastic lesions. These data suggest that in the dimethylhydrazine rat model of colorectal cancer, the Apc gene is mutated in early stages, albeit to a lesser degree than observed in human colorectal cancer, whereas the mutational hot spot of the p53 gene for human colorectal cancer is not commonly mutated. Although the low frequency of Apc mutations and the small number of neoplasms studied in this study might have precluded our ability to observe modulatory effects of folate, dietary folate appears to have no significant effect on Apc and p53 mutations.

Animals↗
PubMed2004

PTEN mutations are common in sporadic microsatellite stable colorectal cancer.

The tumour suppressor gene PTEN, located at chromosome sub-band 10q23.3, encodes a dual-specificity phosphatase that negatively regulates the phosphatidylinositol 3'-kinase (PI3 K)/Akt-dependent cellular survival pathway. PTEN is frequently inactivated in many tumour types including glioblastoma, prostate and endometrial cancers. While initial studies reported that PTEN gene mutations were rare in colorectal cancer, more recent reports have shown an approximate 18% incidence of somatic PTEN mutations in colorectal tumours exhibiting microsatellite instability (MSI+). To verify the role of this gene in colorectal tumorigenesis, we analysed paired normal and tumour DNA from 41 unselected primary sporadic colorectal cancers for PTEN inactivation by mutation and/or allelic loss. We now report PTEN gene mutations in 19.5% (8/41) of tumours and allele loss, including all or part of the PTEN gene, in a further 17% (7/41) of the cases. Both PTEN alleles were affected in over half (9/15) of these cases showing PTEN genetic abnormalities. Using immunohistochemistry, we have further shown that all tumours harbouring PTEN alterations have either reduced or absent PTEN expression and this correlated strongly with later clinical stage of tumour at presentation (P=0.02). In contrast to previous reports, all but one of the tumours with PTEN gene mutations were microsatellite stable (MSI-), suggesting that PTEN is involved in a distinct pathway of colorectal tumorigenesis that is separate from the pathway of mismatch repair deficiency. This work therefore establishes the importance of PTEN in primary sporadic colorectal cancer.

Alleles↗
PubMed1997

Carcinoma-associated expression of core 2 beta-1,6-N-acetylglucosaminyltransferase gene in human colorectal cancer: role of O-glycans in tumor progression.

Recently, it was demonstrated that an increased level of NeuNAc alpha2-3Gal beta1-4(Fuc alpha1-3)GlcNAc beta-R (sialyl Le(x)) and NeuNAc alpha2-3Gal beta1-3(Fuc alpha1-4)GlcNAc beta-R (sialyl Le(a)) expression on the surface of colorectal cancer cells is positively correlated with progression of the disease. It has not been determined, however, which type of glycans, N- or O-glycans, is more closely associated with progression when cancer cells express those oligosaccharides. To address this problem, we have examined expression of sialyl Le(a) and sialyl Le(x), those oligosaccharides in O-glycans, and core 2 beta-1,6-N-acetylglucosaminyltransferase (C2GnT) transcripts in colorectal cancer specimens from 46 patients and compared those results with clinicopathological variables. C2GnT is a glycosyltransferase that is responsible for the core 2 branch, which is critical for biosynthesis of sialyl Le(a) and sialyl Le(x) in O-glycans. Sialyl Le(a) and sialyl Le(x) were determined by immunohistochemistry, and C2GnT transcripts were detected by reverse transcription-PCR. Sialyl Le(a) or sialyl Le(x) in O-glycans was assessed by combining immunohistochemistry for sialyl Le(a) or sialyl Le(x) with reverse transcription-PCR for C2GnT. Sialyl Le(a), detected on cancer cells in 74% of patients, was well correlated with lymph node metastasis, whereas sialyl Le(a) and sialyl Le(x) in O-glycans, which were specifically detected in cancer tissues of 50 and 61% of patients, respectively, were closely associated with lymphatic and venous invasion. In addition, C2GnT, which was specifically detected in cancer tissues of 63% of patients, was closely correlated with the vessel invasion, as well as depth of tumor invasion. These results strongly suggest that sialyl Le(a) and sialyl Le(x) in O-glycans and C2GnT, expressed in cancer cells, may play important roles in tumor progression through vessel or direct invasion.

Adult↗
PubMed2002

Indomethacin induces differential expression of beta-catenin, gamma-catenin and T-cell factor target genes in human colorectal cancer cells.

Indomethacin-induced G(1) arrest and apoptosis of human colorectal cancer (CRC) cells is associated with a dose-dependent decrease in beta-catenin protein levels. Beta-catenin plays a pivotal role in the WNT signalling pathway and its expression is frequently dysregulated at early stages of colorectal carcinogenesis. The objective of this study was to investigate the effect of indomethacin on catenin expression and downstream WNT signalling events in human CRC cells. Beta-catenin, gamma-catenin and T-cell factor (TCF) target gene (cyclin D1, c-MYC and PPARdelta) expression was studied following indomethacin treatment of SW480 and HCT116 cells. Cyclin D1 was used as a model TCF target gene for analysis of beta-catenin-TCF-4 DNA binding and trans-activation. Indomethacin treatment was associated with a specific decrease in beta-catenin (but not gamma-catenin) expression. Resulting TCF target gene expression was gene specific (cyclin D1, decreased; c-MYC, increased; PPARdelta, no significant change). Cyclin D1 promoter analysis revealed that indomethacin disrupted formation of a beta-catenin-TCF-4-DNA complex. Indomethacin-induced G(1) arrest and apoptosis is associated with specific beta-catenin down-regulation in human CRC cells in vitro. Differential expression of TCF target genes following indomethacin treatment implies complex effects on multiple genes which play an important role in colorectal carcinogenesis.

Acetylcysteine↗
PubMed2006

Rac1, but not Rac1B, stimulates RelB-mediated gene transcription in colorectal cancer cells.

Increased NF-kappaB-mediated transcription has been extensively linked to tumorigenesis and can be stimulated by deregulated Rac1 signaling. For example, the overexpression of Rac1b, a highly activated splicing variant of Rac1 with increased expression in colorectal tumors, stimulates NF-kappaB-mediated G1/S progression and cell survival, and was shown to promote cell transformation and epithelial-mesenchymal transition. Here we show evidence of further complexity between Rac1b and Rac1 signaling toward NF-kappaB in colorectal cells. Consistent with data from other cell types we demonstrate that both Rac1 and Rac1b stimulate transcriptional activation from reporter genes driven by NF-kappaB motifs or the cyclin D1 promoter in an IkappaBalpha- and reactive oxygen species-dependent manner. However, we found that in colorectal cells Rac1, but not Rac1b, induces nuclear translocation of RelB and p52, activates transcription from a RelB-specific reporter, and can be isolated in a complex with endogenous RelB and its inhibitor NF-kappaB2/p100. In addition, Rac1 colocalizes at the plasma membrane with RelB, p100, and cullin-1, a core subunit of the E3 ubiquitin ligase that marks p100 for proteolytic processing to p52. Interestingly, this Rac1-specific pathway is not mediated via the production of reactive oxygen species. These data provide evidence that both Rac1 and Rac1b activate the canonical RelA-IkappaBalpha pathway, whereas Rac1 further stimulates NF-kappaB by inducing the RelB-NF-kappaB2/p100 pathway. The RelB pathway was reported to down-regulate canonical NF-kappaB activation during the inflammatory response, suggesting that increased levels of Rac1b in colorectal tumors may promote tumorigenesis by stimulating canonical NF-kappaB signaling while circumventing a negative feedback from the RelB pathway.

Cell Cycle Proteins↗
PubMedDate not supplied

Prevalence of ras gene mutations in human colorectal cancers.

A combination of DNA hybridization analyses and tissue sectioning techniques demonstrate that ras gene mutations occur in over a third of human colorectal cancers, that most of the mutations are at codon 12 of the c-Ki-ras gene and that the mutations usually precede the development of malignancy.

Adenoma↗