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PubMed1996

Genetic heterogeneity and unmapped genes for colorectal cancer.

Colorectal cancer (CRC) has a strong familial component. Candidate genes for colorectal cancer have been identified through mutations in four mismatch repair genes (hMSH2, hMLH1, hPMS1, and hPMS2) and genes that are deleted or mutated in tumors (DCC, APC, and p53). Linkage analysis of candidate loci/regions was performed in 10 kindreds ascertained for common colorectal cancer from the Utah Population Database. Evidence for linkage to candidate genes was assessed using two- or three-point logarithm of the odds ratio scores with markers spanning the region of localization. One kindred is linked to hMSH2 and also fits the criteria for hereditary nonpolyposis colorectal cancer, having early age of onset and high penetrance for CRC. The remaining nine kindreds are unlinked to the candidate genes tested. These kindreds have a later age of onset and a lower penetrance than hereditary nonpolyposis colorectal cancer kindreds. these results indicate that further unmapped susceptibility loci may be responsible for much of the familial aggregation of CRC.

Adult↗

PubMed2001

Frameshift mutations at mononucleotide repeats in RAD50 recombinational DNA repair gene in colorectal cancers with microsatellite instability.

To identify additional genes targeted for microsatellite instability (MSI), we search for human genes which contain mononucleotide repeats in their coding region, selected 7 genes (RAD50, DNA-PKcs, FLASH, Apaf-1, XPG, CtIP, and MLSN1), and analyzed frameshift mutations in them. Here we report that 60% (3 out of 5) of human colorectal cancer cell lines exhibiting a high frequency of MSI (MSI-H) and 46% (6 out of 13) of MSI-H primary colorectal tumors had mutations in the (A)9 repeat of RAD50 recombinational repair gene. In contrast, no frameshift mutations were found in any of the 5 MSI-negative colorectal cancer cell lines, 8 colorectal tumors exhibiting a low frequency of MSI (MSI-L), or 28 MSI-negative colorectal tumors. No mutations were found in the mononucleotide repeats of 6 other genes, even in MSI-H cancers. These results suggest that RAD50 frameshift mutations may play a role in the tumorigenesis of MSI-H colorectal cancers.

Colorectal Neoplasms↗

PubMed2006

Promoter hypomethylation and reactivation of MAGE-A1 and MAGE-A3 genes in colorectal cancer cell lines and cancer tissues.

AIM: To verify the expression and methylation status of the MAGE-A1 and MAGE-A3 genes in colorectal cancer tissues and cancer cell lines. METHODS: We evaluated promoter demethylation status of the MAGE-A1 and MAGE-A3 genes by RT-PCR analysis and methylation-specific PCR (MS-PCR), as well as sequencing analysis, after sodium bisulfite modification in 32 colorectal cancer cell lines and 87 cancer tissues. RESULTS: Of the 32 cell lines, MAGE-A1 and MAGE-A3 expressions were observed in 59% and 66%, respectively. Subsequent to sodium bisulfite modification and MS-PCR analysis, the promoter hypomethylation of MAGE-A1 and MAGE-A3 was confirmed in both at 81% each. Promoter hypomethylation of MAGE-A1 and MAGE-A3 in colorectal cancer tissues was observed in 43% and 77%, respectively. Hypomethylation of MAGE-A1 and MAGE-A3 genes in corresponding normal tissues were observed in 2% and 6%, respectively. CONCLUSION: The promoter hypomethylation of MAGE genes up-regulates its expression in colorectal carcinomas as well as in gastric cancers and might play a significant role in the development and progression of human colorectal carcinomas.

Antigens, Neoplasm↗

PubMed1994

Expression of a homologue of the deleted in colorectal cancer (DCC) gene in the nervous system of developing Xenopus embryos.

The deleted in colorectal cancer (DCC) gene has been identified as a candidate tumor suppressor gene on the basis of frequent allelic loss and decreased or absent gene expression in several human cancer types, as well as somatic mutations in the gene in colorectal tumors. We have identified a Xenopus DCC homologue (XDCC alpha) predicted to encode a protein of 1427 amino acids and have characterized XDCC expression in developing embryos and adult tissues. The predicted amino acid sequences of XDCC alpha and human DCC are greater than 80% identical; each has four immunoglobulin-like domains, six fibronectin type III domains, and a cytoplasmic domain of about 325 amino acids. While RNase protection assays and immunoblotting studies failed to detect XDCC alpha expression in embryos prior to developmental stage 15, XDCC alpha expression was present in embryos from stages 19 to 46. Whole mount in situ hybridization studies localized XDCC alpha expression to developing forebrain, midbrain, and hindbrain regions. DCC expression was inhibited by treatments that altered the development of mature neural structures; specifically, uv-ventralized embryos and exogastrulae had reduced DCC expression. These results indicate that XDCC alpha is developmentally regulated and expressed as a consequence of neural induction. Moreover, unlike some well-characterized tumor suppressor genes, such as the p53 and retinoblastoma genes, that are not differentially expressed in developing Xenopus embryos, the DCC gene may have a specific role in the morphogenesis of the brain and perhaps other tissues and organs.

Amino Acid Sequence↗

PubMed2025

Identification of MMP14 and MKLN1 as colorectal cancer susceptibility genes and drug-repositioning candidates from a genome-wide association study.

BACKGROUND: Genome-wide association studies (GWAS) and subsequent functional interpretation have been used to identify susceptible genes and potential drug-repositioning candidates. This study aimed to identify genes associated with colorectal cancer (CRC) and potential drug-repositioning candidates. METHODS: Patients with CRC at Seoul National University Hospital (SNUH, discovery study) and Chonnam National University Hospital (CNUH, replication study) were included as case groups. The Korean Genome and Epidemiology Study (KoGES) participants were included as a control group. Single-nucleotide polymorphisms (SNPs) were extracted from blood-derived DNA (N = 409,063). A SNP-based logistic regression model was applied. Furthermore, post-GWAS analysis was conducted. Drug-repositioning candidates were identified using a pre-trained deep neural network and the druggability assessment tool. RESULTS: In the discovery study, we conducted a 1:3 age- and sex-matched case-control study that included 500 CRC cases (mean age 63.0 ± 7.15 years) and 1,500 healthy controls (mean age 62.9 ± 7.07 years), each group comprising 50% males and 50% females. The replication study enrolled 4,860 patients with CRC and 46,384 healthy controls. The two-stage GWAS revealed statistically significant associations among MKLN1 (rs75170436, 7q32.3, beta (log odds ratio) = - 0.90, Pmeta = 5.90 × 10-13), MMP14 (rs3751489, 14q11.2, beta (log odds ratio) = - 1.91, Pmeta = 2.31 × 10-12). Post-GWAS functional analysis revealed strong associations on two genes highlighting deleterious effects and increased gene expression. Drug-repositioning analysis identified GW0742 (PPARβ/δ agonist) with the highest binding score and druggability score for MMP14 with a reference allele (12.06, 0.85). CONCLUSIONS: Using GWAS, MKLN1 and MMP14 were found to be associated with CRC development and we identified GW0742 (PPARβ/δ agonist) as a potential drug-repositioning candidate for CRC based on MKLN1 and MMP14. These findings improve the understanding of CRC development and provide insights into novel therapeutic targets and candidates for CRC treatment.

Humans↗

PubMed1996

Evaluation of the FHIT gene in colorectal cancers.

A variety of studies suggests that tumor suppressor loci on chromosome 3p are important in various forms of human neoplasia. Recently, a chromosome 3p14.2 gene called FHIT was discovered and proposed as a candidate tumor suppressor gene in colorectal and other cancers. We evaluated the FHIT gene in a panel of colorectal cancer cell lines and xenografts, which allowed a comprehensive mutational analysis. A transcript containing the complete coding sequence was found to be expressed at robust levels in 29 of 31 cancers tested. The complete sequence of the coding region of the gene was determined and found to be normal in all 29 of these cases. These studies suggest either that FHIT is inactivated by an unusual mechanism or that it plays a role in relatively few colorectal tumors.

Acid Anhydride Hydrolases↗

PubMed2004

Chromosome 7q31 allelic imbalance and somatic mutations of RAY1/ST7 gene in colorectal cancer.

ST7 is a putative tumor suppressor gene on chromosome 7q31. However, the role of ST7 as a tumor suppressor is uncertain as somatic mutations have been difficult to demonstrate. In order to investigate the genetic role of RAY1/ST7 in tumorigenesis, we have screened 135 colorectal cancers for loss of heterozygosity (LOH) at chromosome 7q31. The entire RAY1/ST7 gene, including intron/exon boundaries and alternate 5' and 3' sequences of 15/124 (12%) informative cancers with LOH were characterized. No somatic mutations of the RAY1/ST7 gene were observed. Our results do not support a role for RAY1/ST7 as a colorectal cancer tumor suppressor gene.

Adenocarcinoma↗

PubMed2001

Mutations, methylation and expression of CDKN2a/p16 gene in colorectal cancer and normal colonic mucosa.

The status of CDKN2a gene, coding for p16 and p19ARF proteins, was examined in 55 colorectal cancers. Polymerase chain reaction (PCR), single stranded conformational polymorphism and sequencing revealed 1 case of CDKN2a mutation. Methylation-specific PCR detected p16 locus methylation in 37 (73%) of 51 normal samples and 29 (53%) of 55 cancers (P=0.035). p16 transcript absence (assessed by reverse transcription-polymerase chain reaction) was noted in 10 (45%) of 22 normal samples and four (14%) of 29 cancers (P=0.012) and correlated with gene methylation (P=0.036). The decreasing frequency of p16 silencing in cancer comparing to normal mucosa does not support the postulated role of p16 in colorectal carcinogenesis.

Carrier Proteins↗

PubMed1997

Alternative splicing of the FHIT gene in colorectal cancers.

In the present study, we examined the status of the FHIT gene in 112 colorectal cancer and 137 colorectal adenoma specimens. In a total of 5 specimens (4 colorectal cancers and 1 colorectal adenoma), a common smaller product was detected in addition to the normal size product. This smaller product had lost exon 4, the 5' noncoding region of the FHIT gene, owing to alternative splicing. Moreover, all of the 5 tumors with alternative splicing were located lower on the rectum than the anterior peritoneal reflection.

Acid Anhydride Hydrolases↗

PubMed2001

Differential expression of the chromosome 11 mucin genes in colorectal cancer.

The four secretory mucin genes clustered on chromosome 11, MUC2, MUC5AC, MUC5B and MUC6, were screened in 37 patients with cancers in the left hemi-colon or rectum and 10 normal rectal controls. The mucin genes were detected by in situ hybridization using oligonucleotide probes to the variable number tandem repeat (VNTR) sequences, while the proteins were stained with non-VNTR (MUC2, MUC5AC and MUC5B) or VNTR (MUC6) antibodies. Low levels of MUC2 mRNA were detected in non-mucinous adenocarcinomas (5/27) while a higher proportion of mucinous carcinomas (4/9) was positive. All 25 cases of adjacent normal tissue expressed MUC2 mRNA. No transcripts for MUC5AC, MUC5B or MUC 6 were detected in any of these specimens. MUC2 protein product was detected immunohistochemically in 34/36 carcinoma specimens, with no change from normal controls. There was de novo expression of MUC5AC in 23/36 carcinomas. No MUC5B or MUC6 protein was detected. No difference in MUC2 and MUC5AC protein was found between mucinous and non-mucinous carcinomas. The level of MUC2 was increased in moderately differentiated cancers compared with normal controls and decreased in the poorly differentiated group. Decreased MUC2 was found in poorly differentiated compared with moderately differentiated tumours. More MUC5AC protein was detected in well and moderately differentiated tumours than in poorly differentiated tumours and in all tumours relative to controls. The pattern of MUC2 staining in cancers was different from control tissue, with strong staining in the perinuclear region and none in goblet cell vesicles. MUC5AC staining was mainly detected in the cytoplasm. Poor detection of MUC2 and MUC5AC mRNA and associated strong staining for the total protein suggests altered biosynthesis and processing, leading to the characteristic subcellular distribution. Hence, change in the synthesis of MUC2 and the de novo appearance of MUC5AC in colorectal carcinomas may be significant events in the adenoma-carcinoma sequence, with possible implications for tumour prognosis.

Adenocarcinoma↗

PubMed2005

Epigenetics, mismatch repair genes and colorectal cancer.

The recent discovery of hypermethylation of the promoter of genes is a powerful epigenetic mechanism for the inactivation of tumour suppressor genes in colorectal and other cancers. Approximately 95% of hereditary non-polyposis colorectal cancers (HNPCCs) and 15% of sporadic colorectal cancers (CRCs) are replication error positive (RER(+)). Although DNA mutations are found in mismatch repair genes in the majority of HNPCC CRC, mutations are rare in sporadic RER(+) CRCs. We have shown that the principal cause of an RER(+) phenotype is hypermethylation of the promoter of hMLH1, resulting in the absence of hMLH1 protein. In contrast to sporadic RER(+) CRCs, we found that hypermethylation of hMLH1 does not occur in HNPCC CRC, suggesting the possibility of further differences between the two types of RER(+) tumours in the adenoma to carcinoma pathway. Other known tumour suppressor genes with few or no mutations may be candidates for epigenetic changes. One such gene is E-cadherin, and we described the first mutations of this gene in CRCs. Half of all CRCs were found to be hypermethylated in the Ecadherin promoter and this correlated with reduced E-cadherin expression. Epigenetic changes occur in CRCs and arise in different frequencies in separate genes. Hypermethylation of the promoter may be reversed and gene function restored to a cell, thus partially undoing the cancer phenotype.

Adaptor Proteins, Signal Transducing↗

PubMed2003

Evaluation of K-RAS gene in colorectal cancer.

The aim of the study was to assess the prevalence of K-RAS gene mutations in colorectal cancer and their role in diagnosis and prognosis. The study involved 36 patients with colorectal cancer at different stages of the disease progression and with different histopathologic grading. Mutations of codon 12 of K-RAS gene investigated using PCR-RFLP technique were found in 15 patients (41.67%). Although no statistically significant correlation was observed between the disease progression, histopathologic findings, gender and age, we suppose that assessment of K-RAS gene mutations might be of clinical value in the prognosis of colorectal cancer.

Adult↗

PubMed2005

[Screening of differentially expressed genes in colorectal cancer using human whole genomic oligonucleotide microarrays].

OBJECTIVE: To screen the differentially expressed genes in human colorectal cancer (CRC) tissue. METHODS: Affymetrix oligonucleotide microarrays HG-U133 representing 32,264 human genes including 19,308 known genes and 12,956 expressed sequence tags (ESTs) were used to detect the gene expressions of CRC tissue paired with normal mucosa tissue. The microarray findings were confirmed by real-time quantitative reverse transcriptase-polymerase chain reaction (FQ-PCR). The gene expression profiles were analyzed by intersection and complement, rank sum test and t test. RESULTS: Totally 3,125 genes and ESTs expressed differentially were detected in normal and cancer tissues, consisting of 974 up-regulated and 2,151 down-regulated genes with 247 ESTs present in CRC tissue and absent in normal mucosa and 162 ESTs absent in CRC tissue but present in normal mucosa. A percent of 80.1% of the differentially expressed genes were not reported in the literatures. CONCLUSION: The strategy of data mining provides a foundation for filtering molecular markers and interpreting molecular carcinogenesis of CRC.

Colorectal Neoplasms↗

PubMed1992

Dominant genes for colorectal cancer are not rare.

The genetic basis for colorectal cancer was investigated by complex segregation analysis of a published series of consecutive pedigrees ascertained through patients undergoing treatment for colorectal cancer. Analysis favoured a dominant gene or genes with a frequency of 0.006 with a lifetime penetrance of 0.63. These genes account for 81% of colorectal cancer in patients under 35, however, by 65 about 85% are phenocopies.

Adult↗

PubMedDate not supplied

Mutations of rabphillin-3A-like gene in colorectal cancers.

The chromosome region 17p shows frequently allele losses/mutations in colorectal cancers, and such frequent genetic alterations are a hallmark of the presence of tumor-suppressor gene. The RPH3AL, which is located at 17p13, has been identified from a candidate 17p13 medulloblastoma tumor suppressor locus. The aim of this study was to determine whether it is also altered in colorectal cancers. Mutational analyses of the RPH3AL gene were performed on DNA samples from 50 primary colorectal cancer specimens using polymerase chain reaction-single strand conformation polymorphism, and DNA sequencing. Six missense mutations producing amino acid substitution in coding region of the RPH3AL gene were detected in 50 primary colorectal cancer patients. The RPH3AL gene may play a role as a tumor-suppressor gene in fraction of colorectal cancers, but a minority show RPH3AL gene mutations. Somatic RPH3AL mutations were identified, providing support for an authentic role as tumor-suppressor gene in colorectal cancer, but only in a minority of cases.

Adaptor Proteins, Signal Transducing↗

PubMed2002

Polymorphisms of the human UDP-glucuronosyltransferase (UGT) 1A7 gene in colorectal cancer.

BACKGROUND: Genetic polymorphisms in the human UDP-glucuronosyltransferase-1A7 (UGT1A7) gene are detected and significantly correlated with sporadic colorectal carcinoma. UGT1A7, which has recently been demonstrated to glucuronidate environmental carcinogens, is now implicated as a cancer risk gene. A silent mutation at codon 11 and missense mutations at codons 129, 131, and 208 lead to the description of three polymorphic alleles designated UGT1A7*2, UGT1A7*3, and UGT1A7*4. METHODS: UGT1A7 polymorphisms were analysed by polymerase chain reaction amplification and sequencing, as well as temperature gradient gel electrophoresis in 210 healthy blood donors and 78 subjects with colorectal cancer. RESULTS: Homozygous wild-type UGT1A7 alleles were present in 20% of normal controls but were only detected in 9% of patients with colorectal carcinoma (odds ratio (OR) 0.39 (95% confidence interval (CI) 0.17-0.92); p=0.03). Analysis of individual polymorphic alleles identified a highly significant association between the presence of UGT1A7*3 alleles and colorectal cancer (OR 2.75 (95% CI 1.6 - 4.71); p<0.001). Recombinant expression of UGT1A7 polymorphic cDNA in eukaryotic cell culture showed reduced carcinogen glucuronidation activity in comparison with wild-type UGT1A7. UGT1A7 may therefore represent a modifier gene in colorectal carcinogenesis. CONCLUSION: We have identified a potential novel risk factor in sporadic colorectal cancer which may contribute to the identification of risk groups and to the elucidation of factors involved in colon carcinogenesis.

Adult↗

PubMed2002

The APC gene in colorectal cancer.

Mutations in the adenomatous polyposis coli (APC) gene are not only responsible for familial adenomatous polyposis (FAP), but also play a rate-limiting role in the majority of sporadic colorectal cancers. Colorectal tumours are known to arise through a gradual series of histological changes, the so-called 'adenoma-carcinoma' sequence, each accompanied by a genetic alteration in a specific oncogene or tumour suppressor gene. Loss of APC function triggers this chain of molecular and histological changes. In general, an intestinal cell needs to comply with two essential requirements to develop into a cancer: it must acquire selective advantage to allow for the initial clonal expansion, and genetic instability to allow for multiple hits at other genes responsible for tumour progression and malignant transformation. Inactivation of APC seems to fulfill both requirements. In this short review, I will discuss the role played by APC in providing, when mutated, selective advantage, through constitutional activation of the Wnt signal transduction pathway, and chromosomal instability to the nascent intestinal tumor cell.

Chromosome Aberrations↗

PubMed2003

[The expression and imprinting status of insulin-like growth factor 2 gene in colorectal cancer].

OBJECTIVE: To study the imprinting status and expression level of insulin-like growth factor 2 (IGF2) gene in colorectal cancer and to provide a clue for the mechanism of carcinogenesis of colorectal cancer. METHODS: The expression levels of IGF2 in the paired colorectal cancer and adjacent normal tissue were examined and compared by use of semi-quantitative reverse transcription-polymerase chain reaction. The imprinting status of IGF2 was detected by restriction fragment length polymorphism. The relationships between the expression level of IGF2, its imprinting status, and the carcinogenesis of colorectal cancer were analyzed. RESULTS: IGF2 was overexpressed in 82.4% (28/34) of colorectal cancer tissues which was significantly higher than those of the matched normal tissues (P<0.01, t=3.01). 87.5% (14/16) of colorectal cancer showed loss of imprinting(LOI), while 71.4%(10/14) of normal tissues also displayed LOI of IGF2. CONCLUSION: Overexpression of IGF2 was found to play an important role in carcinogenesis of colorectal cancer. LOI of IGF2 may be a prophase manifestation of colorectal cancer.

Colorectal Neoplasms↗