Detection of known missense mutation of hMLH1 in a hereditary non-polyposis colorectal cancer family using DNA extracts from mouthwash samples.

A significant proportion of hereditary non-polyposis colorectal cancer, which has a high risk of synchronous and/or metachronous multiple primary tumors of the colon (Lynch I) or other organs (Lynch II) at a young patient age, is caused by the inheritance of germline mutations in at least 4 genes such as hMSH2, hMLH1, hPMS1, and hPMS2. Accordingly, gene analysis by a noninvasive method would be clinically useful. We examined 20 of the 148 members of the largest hereditary non-polyposis colorectal cancer pedigree in Japan. The proband of this pedigree was known to have a missense mutation of the hMLH1 gene, and further analysis showed that 4 other persons with carcinoma had the same genotype. Genomic DNA was extracted from mouthwash precipitates. The site of mutation was detected by 3 polymerase chain reaction (PCR)-related techniques (PCR-restriction fragment length polymorphism, allele-specific PCR, and/or PCR-direct sequencing). To confirm the accuracy of this method, we also analyzed the DNA extracted from blood-cell samples in 14 subjects. Six of the 20 subjects were possible carriers, but every individual except the proband was free from tumors. In the 14 subjects tested, the results obtained from mouthwash samples agreed with those from blood-cell samples. Our results suggest that the extraction of DNA from mouthwash samples is a convenient, noninvasive, and effective method of identifying possible carriers among family members of persons with hereditary non-polyposis colorectal cancer. [ABSTRACT FROM AUTHOR]