De novo constitutional MLH1 epimutations confer early-onset colorectal cancer in two new sporadic Lynch syndrome cases, with derivation of the epimutation on the paternal allele in one.

Lynch syndrome is an autosomal dominant cancer predisposition syndrome classically caused by germline mutations of the mismatch repair genes, MLH1, MSH2, MSH6 and PMS2. Constitutional epimutations of the MLH1 gene, characterized by soma-wide methylation of a single allele of the promoter and allelic transcriptional silencing, have been identified in a subset of Lynch syndrome cases lacking a sequence mutation in MLH1. We report two individuals with no family history of colorectal cancer who developed that disease at age 18 and 20 years. In both cases, cancer had arisen because of the de novo occurrence of a constitutional MLH1 epimutation and somatic loss-of-heterozygosity of the functional allele in the tumors. We show for the first time that the epimutation in one case arose on the paternally inherited allele. Analysis of 13 tumors from seven individuals with constitutional MLH1 epimutations showed eight tumors had lost the second MLH1 allele, two tumors had a novel pathogenic missense mutation and three had retained heterozygosity. Only 1 of 12 tumors demonstrated the BRAF V600E mutation and 3 of 11 tumors harbored a mutation in KRAS. The finding that epimutations can originate on the paternal allele provides important new insights into the mechanism of origin of epimutations. It is clear that the second hit in MLH1 epimutation-associated tumors typically has a genetic not epigenetic basis. Individuals with mismatch repair-deficient cancers without the BRAF V600E mutation are candidates for germline screening for sequence or methylation changes in MLH1.

Successful strategies for increasing African American participation in cancer genetic studies: hopeful signs for equalizing the benefits of genetic medicine.

OBJECTIVE: To determine whether prior success in recruiting African Americans to an in-house cancer genetics registry could be duplicated when recruiting to a national registry requiring a significantly increased level of commitment. Additionally, to determine which recruitment sources and practices yielded the highest number of African American participants. METHODS: A retrospective analysis of recruitment sources, practices, and results for recruitment to the Cancer Genetics Network (CGN; a national research registry), from 2000 to 2005 was conducted. These results were compared to previous experience in recruiting African Americans to the Family Cancer Registry (FCR; an in-house registry) during the period 1992-2005. RESULTS: In the 1st year of recruitment to the CGN, African Americans accounted for 24% of those consenting to participate in the CGN registry from our center. This compares to an average annual rate of 27% for the FCR during the years 1998-2005, and a rate of less than 1% from 1992 to 1998. By 2005, African Americans accounted for 27% of CGN participants recruited through the University of Texas Southwestern Medical Center, one of eighteen participating institutions in the CGN. Hospital-based resources such as cancer treatment clinics and tumor registries yielded the highest percentage of African American participants (66.5%), and self-referral yielded the lowest (0%). Seventy-seven percent of African Americans were actively sought out and recruited from treatment clinics, whereas the vast majority of Caucasian participants were recruited passively during the course of genetic counseling sessions that were scheduled for reasons unrelated to participation in cancer research. There were no known instances of African Americans contacting CGN staff after reading printed recruitment materials or internet advertisements. CONCLUSIONS: The increased level of commitment required of CGN participants did not deter African Americans from participating in cancer genetics research. Recruitment strategies responsible for dramatically increasing recruitment rates to the FCR from 1998 to 2000 were equally effective when used for recruitment to the CGN. The most effective recruitment sources were high-yield venues such as cancer treatment clinics and tumor registries, and active recruitment methods yielded the highest number of African American participants. Advertising through internet announcements and printed recruitment materials did not appear to be effective.