Missense Mutations in Cancer Predisposing Genes: Can We Make Sense of Them?

In the analysis of genes associated with predispositions to malignancy the causative status of mutations can be made relatively easily where it is obvious that there is a clear disruption in the coding sequence of the gene. Difficulties arise, however, if missense mutations are identified, as these are not easily categorised into genetic variants that are not associated with disease risk or into clearly causative changes that impart a significant risk of disease

Deletion Mutations in an Australian Series of HNPCC Patients

Hereditary non polyposis colorectal cancer (HNPCC) is characterized by the presence of early onset colorectal cancer and other epithelial malignancies. The genetic basis of HNPCC is a deficiency in DNA mismatch repair, which manifests itself as DNA microsatellite instability in tumours. There are four genes involved in DNA mismatch repair that have been linked to HNPCC; these include hMSH2, hMLH1, hMSH6 and hPMS2. Of these four genes hMLH1 and hMSH2 account for the majority of families diagnosed with the disease. Notwithstanding, up to 40 percent of families do not appear to harbour a change in either hMSH2 or hMLH1 that can be detected using standard screening procedures such as direct DNA sequencing or a variety of methods all based on a heteroduplex analysis

Whole genome amplification and its impact on CGH array profiles

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Frequency of the Common MYH Mutations (G382D and Y165C) in MMR Mutation Positive and Negative HNPCC Patients

Recently mutations in the MYH gene have been associated with a milder form of adenomatous polyposis which is characterized by a variable level of colonic polyps ranging from a few to several hundred. In the context of HNPCC it is not unusual to identify patients with a smattering of polyps. The MYH gene product is involved in DNA repair and indeed the hMSH2/hMSH6 complex (both genes being essential elements of the DNA mismatch repair pathway) is required to stimulate MYH activity. We reasoned that because of the clinical similarity of a subset of HNPCC patients to those described with MYH mutations and the role of the hMSH2/hMSH6 complex in the activation of MYH protein that MYH mutations may account for a small proportion of HNPCC patients. In a study of 442 HNPCC patients we identified MYH mutations at the same frequency as that expected in the general population. Nevertheless, two HNPCC families were identified harbouring biallelic changes in MYH

The Association of the COMT V158M Polymorphism with Endometrial/Ovarian Cancer in HNPCC Families Adhering to the Amsterdam Criteria

Catechol-O-methyltransferase (COMT) is vital for the conjugation of catechol estrogens that are produced during oestrogen metabolism. The efficiency of this process varies due to a polymorphism in COMT, which changes valine to methionine (V158M). The Met genotypes slow the metabolism of catechol oestrogens, which are agents that are capable of causing DNA damage through the formation of DNA adducts and reactive oxygen species (ROS) production. The slower metabolism of catechol oestrogens results in there being a higher circulating concentration of these oeastrogens and consequently greater probability of DNA damage. To determine whether metabolic inefficiencies of oeastrogen metabolism are associated with the development of malignancy in hereditary non-polyposis colorectal cancer (HNPCC), we studied the V158M polymorphism in COMT in a large cohort of 498 HNPCC patients from Australia and Poland that were either mutation positive (n = 331) or negative (n = 167) for mismatch repair (MMR) gene mutations (hMLH1 or hMSH2). HNPCC is a familial predisposition to colorectal cancer (CRC) and extracolonic cancers that include endometrial cancer

Germline Missense Changes in the APC Gene and Their Relationship to Disease

Familial adenomatous polyposis (FAP) is characterized by the presence of hundreds to thousands of adenomas that carpet the entire colon and rectum. Nonsense and frameshift mutations in the adenomatous polyposis coli (APC) gene account for the majority of mutations identified to date and predispose primarily to the typical disease phenotype. Some APC mutations are associated with a milder form of the disease known as attenuated FAP. Virtually all mutations that have been described in the APC gene result in the formation of a premature stop codon and very little is known about missense mutations apart from a common Ashkenazi Jewish mutation (1307 K) and a British E1317Q missense change. The incidence of missense mutations in the APC gene has been underreported since the APC gene lends itself to analysis using an artificial transcription and translation assay known as the Protein Truncation Test (PTT) or the In Vitro Synthetic Protein assay (IVSP)

A Comparison Between Denaturing Gradient Gel Electrophoresis and Denaturing High Performance Liquid Chromatography in Detecting Mutations in Genes Associated with Hereditary Non-Polyposis Colorectal Cancer (HNPCC) and the Identification of 9 New Mutations Previously Unidentified by DGGE

Denaturing high performance liquid chromatography is a relatively new method by which heteroduplex structures formed during the PCR amplification of heterozygote samples can be rapidly identified. The use of this technology for mutation detection in hereditary non-polyposis colorectal cancer (HNPCC) has the potential to appreciably shorten the time it takes to analyze genes associated with this disorder. Prior to acceptance of this method for screening genes associated with HNPCC, assessment of the reliability of this method should be performed. In this report we have compared mutation and polymorphism detection by denaturing gradient gel electrophoresis (DGGE) with denaturing high performance liquid chromatography (DHPLC) in a set of 130 families. All mutations/polymorphisms representing base substitutions, deletions, insertions and a 23 base pair inversion were detected by DHPLC whereas DGGE failed to identify four single base substitutions and a single base pair deletion. In addition, we show that DHPLC has been used for the identification of 5 different mutations in exon 7 of hMSH2 that could not be detected by DGGE