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PubMed2006

Immunohistochemistry detects mismatch repair gene defects in colorectal cancer.

OBJECTIVE: The clinical management of colorectal malignancies that arise via the mismatch repair gene pathway may differ from those that arise from the more common loss of heterozygosity pathway. They respond differently to chemotherapy, have a different prognosis and are associated with a raised incidence of metachronous lesions if a germline mutation is present. Established methods of detecting mismatch repair gene defects require the testing for microsatellite instability. This is expensive and requires specialized molecular biological resources and staff. An immunohistochemical method is attractive because it is far cheaper, and can be performed by most anatomical pathology laboratories. The aim of this study was to determine the incidence of mismatch repair gene defects using immunohistochemistry in a group of patients who were aged < or = 45 years at the time of diagnosis of colorectal cancer and to compare the patient survival and pathological features of tumours with and without mismatch repair gene defects. METHODS: One hundred and four patients with colorectal cancer, diagnosed at 45 years or younger between January 1983 and December 2001, who had been managed at Groote Schuur Hospital, were identified from clinical records. Demographic and clinical data was collected from the clinical notes. The pathological reports were reviewed and the original histopathological slides retrieved. New tissue sections were cut from the original paraffin embedded tissue blocks to obtain both normal colonic mucosa and tumour on the same slide. There was insufficient tissue available or poor staining in 11 patients so 93 were available for the study. RESULTS: The mismatch repair status was detected by antibodies to hMLH1 and hMSH2 gene product using a standard immunohistochemical technique. Fifty-six (60%) of 93 tumours demonstrated normal expression of both hMLH1 and hMSH2 protein. Twenty-five (27%) tumours did not express hMLH1 and 12 (13%) hMSH2 proteins. Comparison of the histopathological features revealed that a greater proportion of tumours with absence of either the hMLH1 or hMSH2 product were right sided, mucinous and poorly differentiated when compared to those that expressed the gene product. There was no detectable difference in overall survival or in survival of patients with Duke's C carcinoma when the groups were separated by the presence or absence of gene product. CONCLUSIONS: This study found that 40% of patients who were < or = 45 years of age at the time of diagnosis of colorectal cancer seen at Groote Schuur Hospital have tumours which are related to the absence of expression of either hMLH1 or hMSH2 genes.

Adaptor Proteins, Signal Transducing↗

PubMed2004

Use of DNA from human stools to detect aberrant CpG island methylation of genes implicated in colorectal cancer.

Hypermethylation of cytosine residues in the CpG islands of tumor suppressor genes is a key mechanism of colorectal carcinogenesis. Detection and quantification of CpG island methylation in human DNA isolated from stools might provide a novel strategy for the detection and investigation of colorectal neoplasia. To explore the feasibility of this approach, colorectal biopsies and fecal samples were obtained from 32 patients attending for colonoscopy or surgery, who were found to have adenomatous polyps, colorectal cancer, or no evidence of neoplasia. A further 18 fecal samples were obtained from healthy volunteers, with no bowel symptoms. Isolated DNA was modified with sodium bisulfite and analyzed by methylation-specific PCR and combined bisulfite restriction analysis for CpG island methylation of ESR1, MGMT, HPP1, p16(INK4a), APC, and MLH1. CpG island methylation was readily detectable in both mucosal and fecal DNA with methylation-specific PCR. Using combined bisulfite restriction analysis, it was established that, in volunteers from whom biopsies were available, the levels of methylation at two CpG sites within ESR1 assayed using fecal DNA were significantly correlated with methylation in DNA from colorectal mucosa. Thus, noninvasive techniques can be used to obtain quantitative information about the level of CpG island methylation in human colorectal mucosa. The methods described here could be applied to a much expanded range of genes and may be valuable both for screening purposes and to provide greater insight into the functional consequences of epigenetic changes in the colorectal mucosa of free-living individuals.

Adenomatous Polyps↗

PubMed1997

Analysis of p53 gene deletions in colorectal cancers using fluorescence in situ hybridization.

To examine the relationship between the incidence of p53 gene deletion in each nucleus and the clinicopathological features in colorectal cancers, we performed a cytogenetic study using fluorescence in situ hybridization (FISH). FISH was performed on 5 adenomas and 38 colorectal cancers that had been resected surgically. The nucleus, in which the copy number of the p53 signal was lower than that of chromosome 17, was determined as a deletion of the p53 gene. The mean frequency of the deletion of p53 in adenomas and cancers were 7.8% +/- 3.0% and 57.0% +/- 19.0%, respectively. Numerical aberrations of chromosome 17 or a deletion of p53 were also detected in DNA diploidy. The mean frequency of the deletion of p53 in 32 cases with aneusomy of chromosome 17 (65.7% +/- 14.5%) was significantly higher than that in cases of disomy (51.1% +/- 19.3%, P < 0.05). Even though this frequency was high in the early stage, it was not associated with any specific histopathological features. This frequency was also higher in double primary cancers (70.4% +/- 16.7%) compared with single colorectal cancers (53.4% +/- 18.1%) (P < 0.05). Using FISH, our results demonstrated that the clonal deletion of the p53 locus is an early genetic event of colorectal cancers and that a high incidence of p53 deletion may influence the occurrence of double primary cancers.

Adenoma↗

PubMed1996

[APC mutation analysis in sporadic colorectal cancer].

APC gene, responsible for familial adenomatous polyposiscoli, is one of the tumor suppressor genes involved in tumorigenesis of sporadic colorectal cancer. Because the majority of APC mutations are located in the 5' end of exon 15 and 95% of them generate stop codon, a coupled in vitro transcription and translation system (IVSP) was used to detect somatic APC mutation of exon 15 in sporadic colorectal cancer. Forty-nine mutated sporadic cases containing 59 truncated bands (9 cases with 2 bands) were identified. The results of the study showed: 1. APC frameshift mutations were more frequent than point mutations (60% vs 40%). Most of the frameshift mutations (32/35) were deletion or insertion of 1-2 bp, whereas 16 of all 23 point mutations presented C-to-T transitions. Mutations (57/59) were mostly but unevenly distributed in segment 2 and 3 of exon 15, while in segment 3, 69% (45/59) of all the mutations were predominantly located in mutation cluster region (codon 1286-1531). In seven of the 9 cases with 2 mutations their close proximity with each other is suggestive of the possibility of mutations at 2 independent alleles. The similarities between APC somatic and germline mutations suggest that APC gene might well have some common functions during the tumorigenesis of sporadic and hereditary coloretal cancer.

Colonic Neoplasms↗

PubMed2006

Effects of down-regulating the Id genes in human colorectal cancer cells on early steps of haematogenous metastasis.

Id genes (inhibitor of DNA binding/differentiation) play important roles in tumour growth. We have previously described crucial roles of Id gene over-expression in endothelial cells for tumour angiogenesis. Here, we have evaluated direct effects of Id gene down-regulation on tumour cells, namely on cell proliferation, motility, and adhesion to lung microvasculature during haematogenous metastasis. For this purpose, Id genes were stably down-regulated by RNA interference in human colorectal cancer cells. These cells showed delayed proliferation, inhibited motility and decreased expression of integrin alpha6 and consequently reduced adhesion to lung microvasculature in mice. Static adhesion assays and laminar flow assays revealed decreased laminin binding capacity of these cells, and blocking experiments confirmed that it could be attributed to decreased expression of integrin alpha6. The present results indicate important roles of Id genes in tumour cells during early steps of haematogenous metastasis and suggest dual effects from their therapeutic inhibition.

Animals↗

PubMed2002

[Expression of Fas genes transduced into colorectal cancer cells].

OBJECTIVE: To construct colorectal cancer cells expressing exogenous Fas gene and observe the expression level of its mRNA and protein before and after transduction. METHODS: Fas cDNA was inserted into the multiple cloning site of the expression vector pBK-CMV with molecular cloning technique, and the resultant recombinant plasmid was transduced into colorectal cancer LoVo cells via lipofectamine. G418 was utilized to screen the positive clones containing the recombinant plasmid, where Fas mRNA and protein expression was determined with Western blotting and dot blotting. RESULTS: pBK-CMV Fas cDNA plasmid was successfully constructed. The transduced colorectal cancer cells were screened by G418 and a resistant cell line (LoVo Fas cells) was obtained. Fas expression was detected in both transduced and non-transducted cell lines, but the expression level of both Fas mRNA and protein was much higher in the former, which showed lowered proliferation rate and lengthened doubling time and logarithm growth period than the non-transducted cells, but the difference was not significant. Treatment of the transduced cells with Fas antibody produced significant difference (P<0.05), manifested by apparently inhibited cell growth. CONCLUSIONS: LoVo cells normally has only very low expression level of Fas gene, while transduction with pBK-Fas cDNA can enhance the efficiency of Fas mRNA and protein expressions. Fas antibody significantly inhibits the growth and proliferation of in vitro cultured Fas-expressing LoVo cells.

Colorectal Neoplasms↗

PubMed2003

Regional delivery and selective expression of a high-activity yeast cytosine deaminase in an intrahepatic colon cancer model.

A major potential limitation to the success of enzyme prodrug gene therapy is the toxicity that could result from gene expression in normal tissues. In this study, we investigated the use of an enhanced human carcinoembryonic antigen (CEA) promoter for yeast cytosine deaminase (yCD), which converts 5-fluorocytosine to 5-fluorouracil, to increase targeting while maintaining activity both in cell culture and in nude rats bearing intrahepatic xenografts. We found that an enhanced CEA-yCD adenoviral vector can achieve significantly greater yCD expression in CEA-expressing colon carcinoma cell lines (LoVo, HT29, and CaCo2) compared with a nonspecific Rous sarcoma virus-yCD virus. In contrast, infection with CEA-yCD led to lower or equivalent yCD expression in normal hepatocytes or fibroblasts compared with that produced by the RSV-yCD. Adenovirus administered in the portal vein or the hepatic artery of nude rats bearing intrahepatic LoVo colon carcinomas could mediate beta-galactosidase expression equally in liver and tumors under the control of cytomegalovirus, a nonspecific promoter. However, infusion of CEA-yCD virus markedly increased yCD expression in tumors over normal liver (>4-fold) measured both by levels of mRNA and yCD activity. Moreover, the efficiency of 5-fluorocytosine conversion into 5-fluorouracil in tumors was significantly higher than that in normal liver ( approximately 3-fold) in rats receiving portal venous viral infusion of CEA-yCD and subsequent 5FC treatment. Thus, an enhanced CEA promoter can preferentially stimulate yCD gene expression in CEA-expressing cells in vivo. Such tumor-specific expression should prove useful in colorectal cancer gene therapy to achieve selective prodrug conversion in tumors.

Adenoviridae↗

PubMed2004

[Thymidylate synthase and dihydropyrimidine dehydrogenase gene expressions in colorectal cancer using the Danenberg tumor profile method].

Thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD) have been identified as a predictor of response to 5-fluorouracil (5-FU). Danenberg et al. developed a technology to evaluate gene expressions in formalin-fixed paraffin-embedded (FFPE) specimens (DTP; Danenberg tumor profile). In this study, TS and DPD gene expressions were measured in 47 primary colorectal cancer tumors and 12 metastatic tumors using FFPE specimens. In primary tumors, expression of TS genes in cancerous tissues was statistically higher than in stromal tissues, while DPD gene expressions in stromal tissues were higher than those in cancerous tissues. The median TS mRNA level was 0.86 in hepatic metastasis and 1.95 in lymph node metastasis. The median DPD mRNA level was 0.86 in hepatic metastasis and 1.96 in lymph node metastasis. Both gene expressions differed among primary tumors and metastatic tumors, especially in metastatic sites. DTP might be useful to evaluate the 2 gene expressions in colorectal cancer. Further studies would be needed to clarify the mechanisms of difference of gene expressions in cancerous and stromal tissues, or in primary tumors and metastatic tumors.

Colorectal Neoplasms↗

PubMed2003

Apolipoprotein E gene polymorphism and colorectal cancer: gender-specific modulation of risk and prognosis.

Apolipoprotein E ( ApoE ) gene polymorphism is a major factor in lipid metabolism. It has been suggested that this polymorphism can modulate colorectal tumour risk. We tested this hypothesis for colorectal cancer (CRC). ApoE genotype was determined in 206 patients with CRC and 353 healthy controls from the East Anglia region of the U.K. Compared with individuals possessing the most common epsilon 3/epsilon 3 genotype, those with the epsilon 2/epsilon 3 genotype had an increased risk of colon cancer [odds ratio (OR) = 1.91; 95% confidence interval 1.05-3.45]. However, this association was strongly affected by gender. Separate analysis of male and female subjects revealed a highly significant association in men (OR = 2.71; 95% confidence interval 1.30-5.65), but no association in women (OR = 1.01; 95% confidence interval 0.37-2.77). Likewise, the proportion of male patients with more advanced tumours (Dukes' C&D) was significantly increased among those with the ApoE epsilon 2/epsilon 3 genotype (OR = 4.16; 95% confidence interval 1.36-12.75). No significant effect of the presence of the epsilon 4 allele on CRC risk was found; however, there were no epsilon 4/epsilon 4 homozygotes among patients with proximal colon cancers. The ApoE epsilon 3/epsilon 3 majority genotype appeared to be associated with the lowest risk of CRC. These results suggest that ApoE genotype can influence both CRC risk and prognosis of the existing disease in a gender-dependent manner.

Aged↗

PubMed2002

DNA methylation down-regulates CDX1 gene expression in colorectal cancer cell lines.

CDX1 is a homeobox protein that inhibits proliferation of intestinal epithelial cells and regulates intestine-specific genes involved in differentiation. CDX1 expression is developmentally and spatially regulated, and its expression is aberrantly down-regulated in colorectal cancers and colon cancer-derived cell lines. However, very little is known about the molecular mechanism underlying the regulation of CDX1 gene expression. In this study, we characterized the CDX1 gene structure and identified that its gene promoter contained a typical CpG island with a CpG observed/expected ratio of 0.80, suggesting that the CDX1 gene is a target of aberrant methylation. Alterations of DNA methylation in the CDX1 gene promoter were investigated in a series of colorectal cancer cell lines. Combined Bisulfite Restriction Analysis (COBRA) and bisulfite sequencing analysis revealed that the CDX1 promoter is methylated in CDX1 non-expressing colorectal cancer cell lines but not in human normal colon tissue and T84 cells, which express CDX1. Treatment with 5'-aza-2'-deoxycytidine (5-azaC), a DNA methyltransferase inhibitor, induced CDX1 expression in the colorectal cancer cell lines. Furthermore, de novo methylation was determined by establishing stably transfected clones of the CDX1 promoter in SW480 cells and demethylation by 5-azaC-activated reporter gene expression. These results indicate that aberrant methylation of the CpG island in the CDX1 promoter is one of the mechanisms that mediate CDX1 down-regulation in colorectal cancer cell lines.

Animals↗

PubMed1995

The genetics of breast and ovarian cancer.

A number of genes are known to be involved in inherited susceptibility to breast and/or ovarian cancer. In the context of high-risk families the most important genes are BRCA1 on chromosome 17q, which is associated with a high penetrance of both breast and ovarian cancer, and BRCA2 on chromosome 13q, which causes a high risk of breast cancer but a lower risk of ovarian cancer. Other high-risk cancer genes that confer increased risks of breast or ovarian cancer in addition to other cancers include the hereditary non-polyposis colorectal cancer genes and the TP53 gene, which causes breast cancer as part of the Li-Fraumeni syndrome. The predisposing mutations in these genes are relatively rare in the population. More common genes which are associated with an increased, but lower, risk of breast cancer are the ataxiatelangiectasia gene and the HRAS1 gene. This paper reviews recent progress in mapping and cloning of these susceptibility genes, and provides estimates of the cancer risks associated with each gene and the frequency of predisposing mutations.

Ataxia Telangiectasia↗

PubMed1992

[Tumor suppressor genes associated with development of human renal cell carcinoma].

Several rodent studies based on molecular biology have suggested that accumulation of genetic alterations in cancer-associated genes is required to convert a normal cell into a malignant cell. Activation of oncogenes and inactivation of tumor suppressor genes appear to be involved in carcinogenesis. In renal cell carcinomas, we have recently implied that the presence of tumor suppressor genes at chromosome 3p13-14.3 and 21.3, the regions where are also commonly deleted in adenocarcinoma of the lung; at chromosome 5q21, the region where the MCC (mutated in colorectal cancer) gene and APC (adenomatous polyposis coli) gene are located; at chromosome 6q27; and at 10q 21-23. We have also indicated that genes on 3p is probably important for development of RCCs and genes on 5q, 6q, and 10q may be associated with progression of RCCs.

Carcinoma, Renal Cell↗

PubMed1993

Mapping of multiple intestinal neoplasia (Min) to proximal chromosome 18 of the mouse.

The Min (multiple intestinal neoplasia) mutation of the mouse has been mapped by analyzing the inheritance of restriction fragment length polymorphisms and simple sequence length polymorphisms in progeny from two intraspecific crosses segregating for the Min mutation. Min, a mutant allele of Apc, the mouse homolog of the human APC (adenomatous polyposis coli) gene, maps to proximal chromosome 18. The synteny between Apc and Mcc, the mouse homolog of the human MCC (mutated in colorectal cancer) gene, is conserved between mouse and human, although the gene order in the Apc to Mcc interval is different from that in the APC to MCC interval.

Adenoma↗

PubMedDate not supplied

Hypermethylation of the Myf-3 gene in human colorectal cancer.

Abnormal methylation of DNA is one of the earliest detectable changes in human tumors. We investigated hypermethylation of the Myf-3 gene, the human homolog of the mouse myogenic gene Myo-D1, in colorectal adenomas and adenocarcinomas. Histologically normal gut mucosa from colorectal cancer patients showed moderately higher levels of methylation than in other normal tissues. Varying degrees of Myf-3 hypermethylation were found in all five adenomas and eight adenocarcinomas examined. Carcinomas arising from within adenomas generally showed a decrease in both the heterogeneity and intensity of Myf-3 methylation. Regional hypermethylation of this gene therefore appears to be an early event in human colorectal neoplasia.

Colorectal Neoplasms↗

PubMed1995

Hereditary nonpolyposis colorectal cancer: the syndrome, the genes, and historical perspectives.

Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal dominant disorder characterized by the occurrence within a family of multiple cases of colorectal cancer in the absence of gastrointestinal polyposis. The prevalence of this syndrome is not yet clear, but it may account for 1%-5% of all colorectal cancers. Prior to the identification of the genetic basis of this syndrome, the disease was recognized by the familial aggregation of colorectal cancers that had an early age of onset, an excess of proximally located, and often multiple, primary tumors, and an excess occurrence of cancers in certain other organs. The recent description of an abnormality called "microsatellite instability," present in almost all cancers from HNPCC patients and in about 12%-15% of sporadic cases, led to a series of discoveries that linked this type of genomic instability to a defect in the DNA mismatch repair (MMR) system. Independent investigators have identified four HNPCC genes: hMSH2 (a homologue of the prokaryotic DNA MMR gene MutS) and hMLH1, hPMS1, and hPMS2 (all homologues of the prokaryotic DNA MMR gene MutL). Mutations in each of the four genes have been found in the germline cells of HNPCC families. A major target for research in this area is the development of clinically practical screening tests for the genetic carrier state of HNPCC.

Colorectal Neoplasms, Hereditary Nonpolyposis↗

PubMed2002

A genomic screen for genes upregulated by demethylation and histone deacetylase inhibition in human colorectal cancer.

Aberrant hypermethylation of gene promoters is a major mechanism associated with inactivation of tumor-suppressor genes in cancer. We previously showed this transcriptional silencing to be mediated by both methylation and histone deacetylase activity, with methylation being dominant. Here, we have used cDNA microarray analysis to screen for genes that are epigenetically silenced in human colorectal cancer. By screening over 10,000 genes, we show that our approach can identify a substantial number of genes with promoter hypermethylation in a given cancer; these are distinct from genes with unmethylated promoters, for which increased expression is produced by histone deacetylase inhibition alone. Many of the hypermethylated genes we identified have high potential for roles in tumorigenesis by virtue of their predicted function and chromosome position. We also identified a group of genes that are preferentially hypermethylated in colorectal cancer and gastric cancer. One of these genes, SFRP1, belongs to a gene family; we show that hypermethylation of four genes in this family occurs very frequently in colorectal cancer, providing for (i) a unique potential mechanism for loss of tumor-suppressor gene function and (ii) construction of a molecular marker panel that could detect virtually all colorectal cancer.

Colorectal Neoplasms↗

PubMed2006

Polymorphism of CD14 gene but not the mutation of TLR4 gene is associated with colorectal cancer in Chinese patients.

OBJECTIVES: Toll-like receptor 4 and CD14 are components of the lipopolysaccharide receptor complex. Our study aimed to investigate an association between TLR4 Asp299Gly and CD14-260 polymorphisms in Chinese patients with colorectal cancer. METHOD: By a method of polymerase chain reaction-based restriction fragment length polymorphism (PCR-RFLP), we genotyped TLR4 Asp299Gly and CD14-260 polymorphisms in 110 unrelated patients with colorectal cancer and 160 healthy controls from the Chinese Han population. RESULTS: We found significant differences in CD14 genotypes between healthy controls and patients with colorectal cancer. The frequency of the C/C genotype in healthy controls (15.6%) was significantly lower than in the group of colorectal cancer patients (32%). The frequency of the C/T genotype in healthy controls (48.1%) was significantly higher than that in the group of colorectal cancer patients (31%). No TLR4 Asp299Gly mutation was detected in any patients or healthy controls in the Chinese Han population. CONCLUSIONS: These findings indicated that the polymorphism of CD14 but not TLR4 Asp299Gly mutation was associated with Chinese patients with colorectal cancer, and the CD14 gene may contribute to the predisposition to colorectal cancer. Screening for the CD14 C-260T genotype is likely to be a useful tool for risk assessment or prognostication for colorectal cancer in the Chinese Han population.

Adult↗

PubMed2002

Antigen levels of the urokinase-type plasminogen activator and its gene polymorphisms in colorectal cancer.

We analysed the distribution of genotypes of two polymorphisms in the urokinase-type plasminogen activator (uPA) gene: C-->T substitution in exon 6 and T-->C substitution in intron 7 in 52 subjects with colorectal cancer. Genotypes were determined in tumour tissue and distant mucosa samples by allele-specific polymerase chain reaction. The antigen levels of uPA in cancer tissue were higher than in distant mucosa as measured by enzyme-linked immunosorbent assay. The level of uPA antigens in cancer samples with the C/C genotype of C-->T polymorphism in exon 6 was higher than in samples with C/T and T/T genotypes. No differences in the level of uPA antigens between the alleles of the intron 7 T-->C polymorphism were found. As uPA can be involved in cancer invasion and metastasis, C/C genotype in exon 6 of uPA gene can be further considered as being related to colorectal cancer progression.

Aged↗