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.Using Real Time PCR, the COMT V158M polymorphism was examined and its association with disease expression, age of diagnosis of cancer, mutation status and mutation type was assessed in the HNPCC MMR mutation positive and negative groups. This study showed that the V158M polymorphism had no association with disease risk in the HNPCC MMR mutation positive population. However, the polymorphism was significantly associated with endometrial/ovarian cancer risk in HNPCC MMR mutation negative patients (p = 0.002). The heterozygous (Val/Met) genotype was associated with an increased risk of developing endometrial/ovarian cancer whereas the homozygous mutant (Met/Met) showed a decreased risk. The results suggest heterosis, where there is an apparent greater effect of the heterozygous state in this dichotomous trait. In conclusion, this study shows that the COMT V158M polymorphism alters the risk of developing endometrial/ovarian cancer in patients that adhere to the Amsterdam HNPCC criteria but do not have a DNA mismatch repair gene mutation.

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.