exudates and Colorectal-Neoplasms--Hereditary-Nonpolyposis

Topics: Adenosine Triphosphatases; Colorectal Neoplasms, Hereditary Nonpolyposis; DNA Mismatch Repair; DNA Repair Enzymes; DNA-Binding Proteins; Germ-Line Mutation; Humans; Malaysia; Mismatch Repair Endonuclease PMS2

Colorectal cancer (CRC) exists in a more common sporadic form and less common hereditary forms, associated with the Lynch syndrome, familial adenomatous polyposis (FAP) and other rare syndromes. Sporadic CRC is believed to arise as a result of close interaction between environmental factors, including dietary and lifestyle habits, and genetic predisposition factors. In contrast, hereditary forms such as those related to the Lynch syndrome result from inheritance of germline mutations of mismatch repair (MMR) genes. However, in certain cases, the influence of low penetrance alleles in familial colorectal cancer susceptibility is also undeniable.. To investigate the genotype frequencies of MLH1 promoter polymorphism -93G>A and to determine whether it could play any role in modulating familial and sporadic CRC susceptibility risk.. A case-control study comprising of 104 histopathologically confirmed CRC patients as cases (52 sporadic CRC and 52 Lynch syndrome patients) and 104 normal healthy individuals as controls was undertaken. DNA was extracted from peripheral blood and the polymorphism was genotyped employing PCR-RFLP methods. The genotypes were categorized into homozygous wild type, heterozygous and homozygous variants. The risk association between these polymorphisms and CRC susceptibility risk was calculated using binary logistic regression analysis and deriving odds ratios (ORs).. When risk association was investigated for all CRC patients as a single group, the heterozygous (G/A) genotype showed a significantly higher risk for CRC susceptibility with an OR of 2.273, (95%CI: 1.133-4.558 and p-value=0.021). When analyzed specifically for the 2 types of CRC, the heterozygous (G/A) genotype showed significantly higher risk for sporadic CRC susceptibility with and OR of 3.714, (95%CI: 1.416-9.740 and p-value=0.008). Despite high OR value was observed for Lynch syndrome (OR: 1.600, 95%CI: 0.715-3.581), the risk was not statistically significant (P=0.253).. Our results suggest an influence of MLH1 promoter polymorphism -93G>A in modulating susceptibility risk in Malaysian CRC patients, especially those with sporadic disease.

Topics: Adaptor Proteins, Signal Transducing; Case-Control Studies; Colorectal Neoplasms, Hereditary Nonpolyposis; Female; Gene Frequency; Genetic Predisposition to Disease; Genotype; Humans; Malaysia; Male; Middle Aged; MutL Protein Homolog 1; Nuclear Proteins; Polymorphism, Single Nucleotide; Promoter Regions, Genetic; Risk; Risk Assessment

To investigate the protein expression profile of mismatch repair (MMR) genes in suspected cases of Lynch syndrome and to characterize the associated germline mutations.. Immunohistochemical analysis of tumor samples was performed to determine the protein expression profile of MMR protein. Germline mutation screening was carried out on peripheral blood samples. The entire exon regions of MLH1 and MSH2 genes were amplified by polymerase chain reaction, screened by denaturing high performance liquid chromatography (dHPLC) and analyzed by DNA sequencing to characterize the germline mutations.. Three out of 34 tissue samples (8.8%) and four out of 34 tissue samples (11.8%) showed loss of nuclear staining by immunohistochemistry, indicating the absence of MLH1 and MSH2 protein expression in carcinoma cells, respectively. dHPLC analysis followed by DNA sequencing showed these samples to have germline mutations of MSH2 gene. However, no deleterious mutations were identified in any of the 19 exons or coding regions of MLH1 gene, but we were able to identify MLH1 promoter polymorphism, -93G > A (rs1800734), in 21 out of 34 patients (61.8%). We identified one novel mutation, transversion mutation c.2005G > C, which resulted in a missense mutation (Gly669Arg), a transversion mutation in exon 1, c.142G > T, which resulted in a nonsense mutation (Glu48Stop) and splice-site mutation, c.2006-6T > C, which was adjacent to exon 13 of MSH2 gene.. Germline mutations were identified in four Malaysian Lynch syndrome patients. Immunohistochemical analysis of tumor tissue proved to be a good pre-screening test before proceeding to germline mutation analysis of DNA MMR genes.

Topics: Adaptor Proteins, Signal Transducing; Base Sequence; Colorectal Neoplasms; Colorectal Neoplasms, Hereditary Nonpolyposis; DNA Mismatch Repair; DNA Mutational Analysis; Genetic Predisposition to Disease; Germ-Line Mutation; Humans; Malaysia; MutL Protein Homolog 1; MutS Homolog 2 Protein; Nuclear Proteins; Polymorphism, Genetic; Promoter Regions, Genetic

DNA mismatch repair gene (MMR) abnormalities are seen in 95 per cent of hereditary nonpolyposis colorectal cancer (HNPCC) and 10-15 per cent of sporadic colorectal cancers. There are no data on MMR abnormalities in Malaysian colorectal cancer patients. This study was aimed to determine the frequency of abnormal MMR gene protein expression in colorectal carcinoma in Northern Peninsular Malaysia using immunohistochemistry.. Clinicopathological information was obtained from 148 patients' records who underwent bowel resection for colorectal cancer (CRC) at the three hospitals in Malaysia. Immunohistochemistry for MLH1, MSH2, MSH6 and PMS2 proteins were performed on paraffin embedded tissue containing carcinoma.. A total of 148 subjects and 150 colorectal carcinomas of sporadic and hereditary types were assessed. Three patients had synchronous tumours. Twenty eight cancers (18.6%) from 26 subjects (17.6%) had absent immunohistochemical expression of any one of the MMR gene proteins. This comprised absent MLH1 only - 3 cancers, absent MSH2 only - 3, absent MSH6 only - 2, absent PMS2 only - 3, absent MLH1 and PMS2 - 14, absent MSH2 and MSH6 - 2 and absent MLH1, MSH6 and PMS2 - 1. There was significant association between abnormal MMR gene protein expression and proximal colon cancers, mucinous, signet ring and poorly differentiated morphology.. Cancers with abnormal MMR gene expression were associated with microsatellite instability-high (MSI-H) phenotype. About 15 per cent demonstrated absent MSH2, MSH6 and PMS2 protein expression in isolation or in combination with other MMR genes, which often predicts a germline mutation, synonymous with a diagnosis of HNPCC. This appears to be high frequency compared to reported data.

Topics: Adaptor Proteins, Signal Transducing; Adenosine Triphosphatases; Adult; Aged; Aged, 80 and over; Colorectal Neoplasms; Colorectal Neoplasms, Hereditary Nonpolyposis; DNA Mismatch Repair; DNA Repair Enzymes; DNA-Binding Proteins; Female; Gene Expression; Germ-Line Mutation; Humans; Immunohistochemistry; Malaysia; Male; Microsatellite Instability; Middle Aged; Mismatch Repair Endonuclease PMS2; MutL Protein Homolog 1; MutS DNA Mismatch-Binding Protein; MutS Homolog 2 Protein; Nuclear Proteins; Retrospective Studies