Identifying individuals with Lynch syndrome (LS) is highly beneficial. However, it is unclear whether microsatellite instability (MSI) or immunohistochemistry (IHC) should be used as the screening ...test and whether screening should target all patients with colorectal cancer (CRC) or those in high-risk subgroups.
MSI testing and IHC for the four mismatch repair proteins was performed on 500 tumors from unselected patients with CRC. If either MSI or IHC was abnormal, complete mutation analysis for the mismatch repair genes was performed.
Among the 500 patients, 18 patients (3.6%) had LS. All 18 patients detected with LS (100%) had MSI-high tumors; 17 (94%) of 18 patients with LS were correctly predicted by IHC. Of the 18 probands, only eight patients (44%) were diagnosed at age younger than 50 years, and only 13 patients (72%) met the revised Bethesda guidelines. When these results were added to data on 1,066 previously studied patients, the entire study cohort (N = 1,566) showed an overall prevalence of 44 of 1,566 patients (2.8%; 95% CI, 2.1% to 3.8%) for LS. For each proband, on average, three additional family members carried MMR mutations.
One of every 35 patients with CRC has LS, and each has at least three relatives with LS; all of whom can benefit from increased cancer surveillance. For screening, IHC is almost equally sensitive as MSI, but IHC is more readily available and helps to direct gene testing. Limiting tumor analysis to patients who fulfill Bethesda criteria would fail to identify 28% (or one in four) cases of LS.
Background & Aims: Although the clinical phenotype of Lynch syndrome (also known as hereditary nonpolyposis colorectal cancer) has been well described, little is known about disease in PMS2 mutation ...carriers. Now that mutation detection methods can discern mutations in PMS2 from mutations in its pseudogenes, more mutation carriers have been identified. Information about the clinical significance of PMS2 mutations is crucial for appropriate counseling. Here, we report the clinical characteristics of a large series of PMS2 mutation carriers. Methods: We performed PMS2 mutation analysis using long-range polymerase chain reaction and multiplex ligation-dependent probe amplification for 99 probands diagnosed with Lynch syndrome-associated tumors showing isolated loss of PMS2 by immunohistochemistry. Penetrance was calculated using a modified segregation analysis adjusting for ascertainment. Results: Germ-line PMS2 mutations were detected in 62% of probands (n = 55 monoallelic; 6 biallelic). Among families with monoallelic PMS2 mutations, 65.5% met revised Bethesda guidelines. Compared with the general population, in mutation carriers, the incidence of colorectal cancer was 5.2-fold higher, and the incidence of endometrial cancer was 7.5-fold higher. In North America, this translates to a cumulative cancer risk to age 70 years of 15%–20% for colorectal cancer, 15% for endometrial cancer, and 25%–32% for any Lynch syndrome-associated cancer. No elevated risk for non-Lynch syndrome-associated cancers was observed. Conclusions: PMS2 mutations contribute significantly to Lynch syndrome, but the penetrance for monoallelic mutation carriers appears to be lower than that for the other mismatch repair genes. Modified counseling and cancer surveillance guidelines for PMS2 mutation carriers are proposed.
Endometrial cancer is the most common cancer in women with Lynch syndrome. The identification of individuals with Lynch syndrome is desirable because they can benefit from increased cancer ...surveillance. The purpose of this study was to determine the feasibility and desirability of molecular screening for Lynch syndrome in all endometrial cancer patients. Unselected endometrial cancer patients (N = 543) were studied. All tumors underwent microsatellite instability (MSI) testing. Patients with MSI-positive tumors underwent testing for germ line mutations in MLH1, MSH2, MSH6, and PMS2. Of 543 tumors studied, 118 (21.7%) were MSI positive (98 of 118 MSI high and 20 of 118 MSI low). All 118 patients with MSI-positive tumors had mutation testing, and nine of them had deleterious germ line mutations (one MLH1, three MSH2, and five MSH6). In addition, one case with an MSI-negative tumor had abnormal MSH6 immunohistochemical staining and was subsequently found to have a mutation in MSH6. Immunohistochemical staining was consistent with the mutation result in all seven truncating mutation-positive cases but was not consistent in two of the three missense mutation cases. We conclude that in central Ohio, at least 1.8% (95% confidence interval, 0.9-3.5%) of newly diagnosed endometrial cancer patients had Lynch syndrome. Seven of the 10 Lynch syndrome patients did not meet any published criteria for hereditary nonpolyposis colorectal cancer, and six of them were diagnosed at age >50. Studying all endometrial cancer patients for Lynch syndrome using a combination of MSI and immunohistochemistry for molecular prescreening followed by gene sequencing and deletion analysis is feasible and may be desirable.
Purpose: The Arg/Pro polymorphism in codon 72 of p53 was recently associated with age of onset of colorectal cancer in Lynch syndrome. A novel polymorphism in the promoter region
of MDM2 was ...associated with age of cancer onset in Li-Fraumeni syndrome. We studied the influence of both polymorphisms on age of
onset in Lynch syndrome and of the p53 polymorphism also in sporadic colorectal cancer.
Experimental Design: We genotyped p53 codon 72 in 193 individuals with Lynch syndrome mutations, 93 patients with sporadic microsatellite unstable colorectal cancer,
and 93 patients with sporadic microsatellite stable colorectal cancer from Finland and 323 Finnish controls. We genotyped
30 colorectal cancer patients with Lynch syndrome mutations from Ohio and 118 U.S. controls. We genotyped SNP309 of MDM2 in the Lynch syndrome groups. We used χ 2 test, Kaplan-Meier statistics, and Cox regression model to analyze the data.
Results: Allele frequencies of both polymorphisms were similar in subjects and controls from both populations and showed Hardy-Weinberg
equilibrium. Neither polymorphism was associated with age of colorectal cancer onset in any of the subject groups.
Conclusions: This study failed to show any role of the p53 polymorphism on age of colorectal cancer onset in Lynch syndrome and sporadic colorectal cancer. The polymorphism in the
MDM2 promoter had no affect on age of onset in Lynch syndrome. Accurate information about age of onset is important in clinical
practice, especially in high-risk conditions. As association studies are vulnerable to biologically insignificant variation,
both positive and negative findings need to be reported to enable unbiased assessment of the significance of putative risk
variants.
Mutations within the DNA mismatch repair gene, “postmeiotic segregation increased 2” (PMS2), have been associated with a predisposition to hereditary nonpolyposis colorectal cancer (HNPCC; Lynch ...syndrome). The presence of a large family of highly homologous PMS2 pseudogenes has made previous attempts to sequence PMS2 very difficult. Here, we describe a novel method that utilizes long‐range PCR as a way to preferentially amplify PMS2 and not the pseudogenes. A second, exon‐specific, amplification from diluted long‐range products enables us to obtain a clean sequence that shows no evidence of pseudogene contamination. This method has been used to screen a cohort of patients whose tumors were negative for the PMS2 protein by immunohistochemistry and had not shown any mutations within the MLH1 gene. Sequencing of the PMS2 gene from 30 colorectal and 11 endometrial cancer patients identified 10 novel sequence changes as well as 17 sequence changes that had previously been identified. In total, putative pathologic mutations were detected in 11 of the 41 families. Among these were five novel mutations, c.705+1G>T, c.736_741del6ins11, c.862_863del, c.1688G>T, and c.2007–1G>A. We conclude that PMS2 mutation detection in selected Lynch syndrome and Lynch syndrome‐like patients is both feasible and desirable. Hum Mutat 27(5), 490–495, 2006. Published 2006 Wiley‐Liss, Inc.
Hypermethylation of the MLH1 promoter is present in most sporadic colorectal cancers and leads to the abrogation of MLH1 transcription. The significance of the hypermethylation of the promoter that ...can be detected in rare foci of cells in the normal colonic epithelium adjacent to the carcinoma is unclear. The purpose of this study was to determine the distribution of hypermethylation of the MLH1 promoter DNA with MLH1 RNA expression by RT in situ PCR and MLH1 protein expression by immunohistochemistry in normal colonic tissues. Hypermethylation of the MLH1 promoter DNA was not evident in sections of normal colon from 10 people with no history of colon cancer. MLH1 RNA and protein were detected diffusely throughout the colonic epithelium in these 10 controls. In comparison, hypermethylation of either of 2 regions of the promoter was evident in the normal mucosa from cases adjacent to adenocarcinoma of the colon. In situ analysis of the DNA methylation showed that there were rare foci that involved small groups of cells, typically toward the middle and surface area of a given crypt. In these areas, small foci of colonic epithelial cells, typically in groups of 5 to 10, were found to lack MLH1 RNA and protein in adjacent serial sections, consistent with silencing of the gene by hypermethylation that may play a role in the origin of these neoplasms. It is concluded that the rare foci of hypermethylation of the MLH1 promoter in normal colon epithelium from people with colorectal cancer is associated with silencing of the gene that may play a role in the early evolution of these neoplasms. A combination of methylation-specific in situ PCR with in situ RNA and protein analysis can assist in documenting rare foci of promoter hypermethylation-induced gene silencing.
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