Disease expression in Swiss hereditary non-polyposis colorectal cancer (HNPCC) kindreds

DNA Methylation Identifies Loci Distinguishing Hereditary Nonpolyposis Colorectal Cancer Without Germ-Line MLH1/MSH2 Mutation from Sporadic Colorectal Cancer

Objectives:

Roughly half of hereditary nonpolyposis colorectal cancer (HNPCC) cases are Lynch syndrome and exhibit germ-line mutations in DNA mismatch repair (MMR) genes; the other half are familial colorectal cancer (CRC) type X (FCCTX) and are MMR proficient. About 70% of Lynch syndrome tumors have germ-line MLH1 or MSH2 mutations. The clinical presentation, histopathological features, and carcinogenesis of FCCTX resemble those of sporadic MMR-proficient colorectal tumors. It is of interest to obtain biomarkers that distinguish FCCTX from sporadic microsatellite stable (MSS) CRC, to develop preventive strategies.

Methods:

The tumors and adjacent normal tissues of 40 patients with HNPCC were assayed using the Illumina Infinium HumanMethylation27 (HM27) BeadChip to assess the DNA methylation level at about 27,000 loci. The germ-line mutation status of MLH1 and MSH2 and the microsatellite instability status in these patients were obtained. Genome-wide DNA methylation measurements of three groups of patients with general CRC were downloaded from public domain databases. Probes with DNA methylation levels that differed significantly between patients with sporadic MSS CRC and FCCTX were examined, to explore their potential as biomarkers.

Results:

We found that MSS HNPCC tumors were overwhelmingly hypomethylated compared with those from patient groups with other types of CRC, including germ-line MLH1/MSH2-mutated HNPCC and sporadic MSS CRC. Five gene-marker panels that exhibited a sensitivity of 100% and a specificity higher than 90% in both discovery and validation cohorts were proposed to distinguish MSS HNPCC tumors from sporadic MSS CRC.

Conclusions:

Our results warrant further investigation and validation. The loci identified here may become useful biomarkers for distinguishing between FCCTX and sporadic MSS CRC tumors.

Evidence for breast cancer as an integral part of Lynch syndrome

Lynch syndrome, an autosomal dominant cancer predisposition caused by mutations in DNA mismatch repair (MMR) genes, mainly mainly mutL homolog 1, OMIM 120436 (MLH1) and mutS homolog 2, OMIM 609309 (MSH2), encompasses a tumor spectrum including primarily gastrointestinal, endometrial, and ovarian cancer. This study aimed at clarifying the heavily debated issue of breast cancer being part of Lynch syndrome. Detailed clinical data on cancer occurrence in Swiss female MLH1/MSH2 mutation carriers were gathered, all available breast cancer specimens assessed for molecular evidence for MMR deficiency (i.e., microsatellite instability (MSI), MMR protein expression, and somatic (epi)genetic MMR gene alterations) and compiled with the scarce molecular data available from the literature. Seventy unrelated Swiss Lynch syndrome families were investigated comprising 632 female family members at risk of which 92 were genetically verified mutation carriers (52 MLH1 and 40 MSH2). On contrast to endometrial and ovarian cancer, which occurred significantly more often and at younger age in MLH1/MSH2 mutation carriers (median 50.5 and 49.0 years; P < 0.00001), overall cumulative breast cancer incidence closely mirrored the one in the Swiss population (56.5 years). Six (85.7%) of seven breast cancer specimens available for molecular investigations displayed the hallmarks of MMR deficiency. Combined with data from the literature, MSI was present in 26 (70.3%) of 37 and altered MMR protein expression in 16 (72.7%) of 22 breast cancer specimens from MLH1/MSH2 mutation carriers. These findings, thus, provide strong molecular evidence for a pivotal role of MMR deficiency in breast cancer development in Lynch syndrome.

Differential diagnostic and functional role of the multi-marker phenotype CDX2/CK20/CK7 in colorectal cancer stratified by mismatch repair status

The differentiation of colorectal cancer from primary tumors at other sites can be challenging. Often a panel of immunohistochemical protein markers is needed to distinguish between these entities. Protein expression differs significantly in colorectal cancer depending on mismatch repair status and is also heterogeneous among mismatch repair-proficient or -deficient tumors. The aim of this study was to systematically analyze the diagnostic and prognostic role of the commonly used multi-marker phenotype CK20/CK7/CDX2 on a large series of colorectal cancers stratified by mismatch repair status. The immunohistochemical analysis of CK20, CK7 and CDX2 was performed on 1197 mismatch repair-proficient and 223 mismatch repair-deficient colorectal cancers using a tissue microarray. Multi-marker combinations of CK20/CK7/CDX2 were explored. Univariate and multivariable analysis of the markers was evaluated for their association with several clinico-pathological end points namely T stage, N stage, tumor grade, vascular invasion, intratumoral lymphocytes and survival. Multi-marker phenotypes with CK20 and CDX2 negativity were more frequently found in mismatch repair-deficient than in mismatch repair-proficient colorectal cancer (19.3 vs 7.5% and 21.6 vs 6.7%, respectively; P<0.001). In both colorectal cancer subsets loss of CK20 was associated with higher tumor grade (P<0.001) and with presence of intratumoral lymphocytes (P<0.001 and P=0.02, respectively). In the proficient mismatch repair subset CK20 overexpression was an independent adverse prognostic factor (P=0.041) and CDX2 underexpression was linked to tumor progression. Loss of CDX2 and CK20 is more frequently encountered in mismatch repair-deficient colorectal cancer, which should be taken into consideration to differentiate between primary and metastatic colorectal cancer in daily practice. Although associated with lower tumor grade, CK20 overexpression is an independent adverse prognostic factor in mismatch repair-proficient colorectal cancer.

Gene-related cancer spectrum in families with hereditary non-polyposis colorectal cancer (HNPCC)

The family histories of 130 individuals with documented hereditary non-polyposis colorectal cancer (HNPCC) (caused by mutations in mismatch-repair (MMR) genes MSH2 (n = 64), MLH1 (n = 62) or MSH6 (n = 4)) were obtained, and incidence of cancers in those families was compared to that in the general population. There were a total of 982 cancers in 723 individuals. Colorectal cancer (CRC) was the commonest type (64% and 55% in individuals from families with germline MLH1 and MSH2 mutations respectively). Median age at diagnosis of first CRC in MSH6 mutation families was 59 years compared to 45 years in both MLH1 and MSH2 mutation families. The relative risk (RR) of endometrial cancer was 55 in MSH2 mutation families, compared with 27 in MLH1 mutation families, and 37 in MSH6 mutation families; median age at diagnosis 49 years. Even within MSH2 families, endometrial cancer tended to cluster, with 28 of the 58 cases coming from families with three or more cases (P < 0.001). Absolute risk of endometrial cancer in MLH1 families was still greater than any other cancer (other than CRC). 5% of cancers in both MLH1 and MSH2 mutation families were gastric (RR = 12); 53% of these were diagnosed before 50 years. Seven cases of small intestinal cancer occurred in MSH2 and MLH1 mutation families (RR = 26). There were 13 cases of cancer of the ureter; all were in MSH2 families. These cancers tended to cluster within families (P < 0.001); three of seven families with urothelial cancer had such cases in two or more individuals; two others had kidney cancer. Nineteen of 27 ovarian cancers (70%) were in MSH2 mutation families and 70% of these were diagnosed before age 50 years. There were 9 cases of sebaceous skin cancer, 3 in two MLH1 and 6 in four MSH2 mutation families. Of 22 pancreatic cancers, 14 were known to be diagnosed before 60 years. Breast cancer RR was 1.7 overall. The type of mutation (truncating or other type, and site of mutation) showed no obvious correlation with the presence or absence of extra-colonic cancers in families.

Rationale for, and approach to, studying modifiers of risk in persons with a genetic predisposition to colorectal cancer

We address the issue of modifiers of risk for persons who are, on average, at high risk of colorectal cancer due to carrying germline genetic mutations. We discuss how to estimate risk and assess modifiers using data from mutation-carrying families. A critical analytical issue is the adjustment for how families have been sampled (ascertainment). Only a few published studies have made appropriate adjustments and have mostly reported lifetime risks of less than 50%. Incomplete penetrance and differences in risk by subcategories are consistent with the existence of genetic and/or environmental risk -modifiers. Data from large cohorts of carriers are required to study such modifiers with precision.

[Identification and management of HNPCC syndrome (hereditary non polyposis colon cancer), hereditary predisposition to colorectal and endometrial adenocarcinomas]

BACKGROUND

The HNPCC syndrome (hereditary nonpolyposis colon cancer) is an inherited condition defined by clinical and genealogical information, known as Amsterdam criteria. In about 70% of cases, HNPCC syndrome is caused by germline mutations in MMR genes, leading to microsatellite instability of tumor DNA (MSI phenotype). Patients affected by the disease are at high risk for colorectal and endometrial carcinomas, but also for small intestine, urothelial, ovary, stomach and biliary tract carcinomas. HNPCC syndrome is responsible for 5% of colorectal cancers. Identification and management of this disease are part of a multidisciplinary procedure.

METHODS

Twelve experts have been mandated by the French Health Ministry to analyze and synthesize their consensus position, and the resulting document has been reviewed by an additional group of 4 independent experts.

MAIN RECOMMENDATIONS

The lack of sensitivity of Amsterdam criteria in recognizing patients carrying a MMR germline mutation led to an enlargement of these criteria for the recruitment of possible HNPCC patients, and to a 2-steps strategy, asking first for a tumor characterization according to MSI phenotype, especially in case of early-onset sporadic cases. The identification of germline MMR mutations has no major consequence on the cancer treatments, but influences markedly the long-term follow-up and the management of at-risk relatives. Gene carriers will enter a follow-up program regarding their colorectal and endometrial cancer risks, but other organs being at low lifetime risk, no specific surveillance will be proposed.

Le syndrome HNPCC (hereditary non polyposis colon cancer) : identification et prise en charge

BACKGROUND

The hereditary non-polyposis colon cancer (HNPCC) syndrome is an inherited condition defined by clinical and genealogical information, known as Amsterdam criteria. In about 70% of cases, HNPCC syndrome is caused by germline mutations in MMR genes, leading to microsatellite instability of tumor DNA (MSI phenotype). Patients affected by the disease are at high risk for colorectal and endometrial carcinomas, but also for other organs tumors. HNPCC syndrome is responsible for 5% of colorectal cancers.

MAJOR ASPECTS

The lack of sensitivity of Amsterdam criteria in recognizing patients carrying a MMR germline mutation led to an enlargement of these criteria for the recruitment of possible HNPCC patients, and to a two-steps strategy, asking first for a tumor characterization according to MSI phenotype, especially in case of early-onset sporadic cases.

FURTHER DEVELOPMENTS

The identification of germline MMR mutations has no major consequence on the cancer treatments, but influences markedly the long-term follow-up and the management of at-risk relatives. Gene carriers will enter a follow-up program regarding their colorectal and endometrial cancer risks; other organs being at low lifetime risk, no specific surveillance will be proposed.

Germline E-cadherin mutations in hereditary diffuse gastric cancer: assessment of 42 new families and review of genetic screening criteria

BACKGROUND

Mutations in the E-cadherin (CDH1) gene are a well documented cause of hereditary diffuse gastric cancer (HDGC). Development of evidence based guidelines for CDH1 screening for HDGC have been complicated by its rarity, variable penetrance, and lack of founder mutations.

METHODS

Forty three new gastric cancer (GC) families were ascertained from multiple sources. In 42 of these families at least one gastric cancer was pathologically confirmed to be a diffuse gastric cancer (DGC); the other family had intestinal type gastric cancers. Screening of the entire coding region of the CDH1 gene and all intron/exon boundaries was performed by bi-directional sequencing.

RESULTS

Novel mutations were found in 13 of the 42 DGC families (31% overall). Twelve of these mutations occur among the 25 families with multiple cases of gastric cancer and with pathologic confirmation of diffuse gastric cancer phenotype in at least one individual under the age of 50 years. The mutations found include small insertions and deletions, splice site mutations, and three non-conservative amino acid substitutions (A298T, W409R, and R732Q). All three missense mutations conferred loss of E-cadherin function in in vitro assays. Multiple cases of breast cancers including pathologically confirmed lobular breast cancers were observed both in mutation positive and negative families.

CONCLUSION

Germline truncating CDH1 mutations are found in 48% of families with multiple cases of gastric cancer and at least one documented case of DGC in an individual under 50 years of age. We recommend that these criteria be used for selecting families for CDH1 mutational analysis.

Tumour spectrum of non-polyposis colorectal cancer (Lynch syndrome) on the island of Tenerife and influence of insularity on the clinical manifestations

Colorectal cancer is a complex disease from a genetic point of view because both genetic and environmental factors interact in its development. Only familial adenomatous polyposis (FAP) follows mendelian genetics, in that mutations of the APC gene lead to development of the tumours. Lynch syndrome is the most frequent form of hereditary colorectal cancer and appears to be associated with other types of extracolonic cancers. The genetic basis has been established as a defect in DNA mismatch repair genes, and there is genetic heterogeneity due to the involvement of several genes in this system. Germinal mutations in these genes predispose to appearance of the syndrome. The aim of this study is to describe the tumoral spectrum of 10 families, comprising a total of 488 individuals, from the island of Tenerife (Canary Islands) and to assess whether the geographical isolation of this population has changed any features of the tumoral spectrum of the syndrome in comparison with studies that cover larger geographical areas with more genetic exchange. From our results we can conclude that the genetic drift and consanguinity in this population with a demographic history of isolation did not significantly alter the tumoral spectrum of the syndrome. Our data confirm that families affected by Lynch syndrome are a high-risk population and should be closely monitored, since their careful supervision has been shown to be useful in preventing cancer. We also emphasize the importance of developing a complete family history that permits these families to be identified together with a mutational screening of DNA mismatch repair genes (mainly MLH1 and MSH2 genes) with the aim of a possible identification of members of a family that should be carefully monitored (the carriers of germline mutations in these genes), whereas the remaining members, originally, are no more at risk than the general population.

A polymorphism in the ATM gene modulates the penetrance of hereditary non-polyposis colorectal cancer

Germ-line mutations in MLH1 and MSH2 genes predispose to hereditary non-polyposis colorectal cancer (HNPCC) syndrome, but they do not predict a specific phenotype of the disease. We speculated that the ataxia-telangiectasia mutated gene (ATM) was a candidate gene to modulate the phenotypic expression of HNPCC, as heterozygous individuals for germ-line ATM mutations have been considered at higher risk of developing epithelial malignancies. The frequency of the ATM D1853N polymorphism was evaluated in 167 individuals from 20 HNPCC families in which MLH1 or MSH2 germ-line mutations co-segregated with the disease. Among the 67 MLH1 or MSH2 mutation carriers, the ATM 1853N variant was associated with a significantly higher incidence of colorectal and other HNPCC-related cancers, when compared with individuals carrying the ATM 1853D variant [12/13 (92%) vs. 31/54 (57.5%); p = 0.02]. MLH1 and MSH2 mutation carriers who concomitantly carried the ATM 1853N variant, had an 8 times increased risk of developing colorectal and other HNPCC-related cancers (OR: 8.9; p = 0.02), when compared with MLH1 or MSH2 mutation carriers with the ATM 1853D variant. Our results suggest that the ATM D1853N polymorphism modulates the penetrance of MLH1 and MSH2 germ-line mutations.

Genetic susceptibility to non-polyposis colorectal cancer

Familial colorectal cancer (CRC) is a major public health problem by virtue of its relatively high frequency. Some 15-20% of all CRCs are familial. Among these, familial adenomatous polyposis (FAP), caused by germline mutations in the APC gene, accounts for less than 1%. Hereditary non-polyposis colorectal cancer (HNPCC), also called Lynch syndrome, accounts for approximately 5-8% of all CRC patients. Among these, some 3% are mutation positive, that is, caused by germline mutations in the DNA mismatch repair genes that have so far been implicated (MLH1, MSH2, MSH6, PMS1, and PMS2). Most of the remaining patients belonging to HNPCC or HNPCC-like families are still molecularly unexplained. Among the remaining familial CRCs, a large proportion is probably caused by gene mutations and polymorphisms of low penetrance, of which the I1307K polymorphism in the APC gene is a prime example. Molecular genetic findings have enabled hereditary CRC to be divided into two groups: (1) tumours that show microsatellite instability (MSI), occur more frequently in the right colon, have diploid DNA, harbour characteristic mutations such as transforming growth factor beta type II receptor and BAX, and behave indolently, of which HNPCC is an example; and (2) tumours with chromosomal instability (CIN), which tend to be left sided, show aneuploid DNA, harbour characteristic mutations such as K-ras, APC, and p53, and behave aggressively, of which FAP is an example. This review focuses most heavily on the clinical features, pathology, molecular genetics, surveillance, and management including prophylactic surgery in HNPCC. Because of the difficulty in diagnosing HNPCC, a detailed differential diagnosis of the several hereditary CRC variants is provided. The extant genetic and phenotypic heterogeneity in CRC leads to the conclusion that it is no longer appropriate to discuss the genetics of CRC without defining the specific hereditary CRC syndrome of concern. Therefore, it is important to ascertain cancer of all anatomical sites, as well as non-cancer phenotypic stigmata (such as the perioral and mucosal pigmentations in Peutz-Jeghers syndrome), when taking a family cancer history.

Influence of selection criteria on mutation detection in patients with hereditary nonpolyposis colorectal cancer

BACKGROUND

Hereditary nonpolyposis colorectal cancer (HNPCC) is linked genetically to mutations in DNA mismatch repair (MMR) genes. Because a deficiency in MMR does not predict a specific phenotype, the original selection criteria may be too restrictive in identifying additional families. The current study was performed to determine whether a relaxation of the Amsterdam criteria (AC) could be applied to identify more families associated with DNA MMR.

METHODS

Twenty-eight unrelated Swiss families (15 complying with the AC and 13 fulfilling extended criteria [EC] to include other tumors of the HNPCC spectrum as well) were screened for mutations in the MMR genes hMSH2 and hMLH1, using single-stranded conformation polymorphism and direct DNA sequencing. Microsatellite instability (MSI) was determined in 14 families. A comparison was made between the phenotypic characteristics of the mutation positive and mutation negative families.

RESULTS

Ten AC families (67%) harbored germline mutations in hMLH1 (6 kindreds) or hMSH2 (4 kindreds). In none of the EC kindreds could an unambiguous disease-causing mutation be identified. Seven of eight AC families were found to display MSI whereas all colorectal carcinomas (CRC) in eight EC kindreds were MSI stable. CRC patients from mutation positive families had an earlier age at diagnosis (44 years vs. 49 years) and appeared to have a better survival (11.1 years vs. 7.7 years).

CONCLUSIONS

Extending the AC to include extracolonic tumors of the HNPCC spectrum results in a very low mutation detection rate for hMSH2 and hMLH1. The EC families appear to represent an alternative genetic entity not necessarily related to DNA MMR gene mutations because they do not display MSI.

Microsatellite instability and mutation of DNA mismatch repair genes in gliomas

Microsatellite instability (MSI) has been identified in various human cancers, particularly those associated with the hereditary nonpolyposis colorectal cancer syndrome. Although gliomas have been reported in a few hereditary nonpolyposis colorectal cancer syndrome kindred, data on the incidence of MSI in gliomas are conflicting, and the nature of the mismatch repair (MMR) defect is not known. We established the incidence of MSI and the underlying MMR gene mutation in 22 patients ages 45 years or less with sporadic high-grade gliomas (17 glioblastomas, 3 anaplastic astrocytomas, and 2 mixed gliomas, grade III). Using five microsatellite loci, four patients (18%) had high level MSI, with at least 40% unstable loci. Germline MMR gene mutation was detected in all four patients, with inactivation of the second allele of the corresponding MMR gene or loss of protein expression in the tumor tissue. Frameshift mutation in the mononucleotide tract of insulin-like growth factor type II receptor was found in one high-level MSI glioma, but none was found in the transforming growth factor beta type II receptor and the Bax genes. There was no family history of cancer in three of the patients, and although one patient did have a family history of colorectal carcinoma, the case did not satisfy the Amsterdam criteria for hereditary nonpolyposis colorectal cancer syndrome. Three patients developed metachronous colorectal adenocarcinomas, fitting the criteria of Turcot's syndrome. Thus, MSI and germline MMR gene mutation is present in a subset of young glioma patients, and these patients and their family members are at risk of developing other hereditary nonpolyposis colorectal cancer syndrome-related tumors, in particular colorectal carcinomas. These results have important implications in the genetic testing and management of young patients with glioma and their families.