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A systematic search by Southern blot analysis in a cohort of 439 hereditary nonpolyposis colorectal cancer (HNPCC) families for genomic rearrangements in the main mismatch repair (MMR) genes, namely, MSH2, MLH1, MSH6, and PMS2, identified 48 genomic rearrangements causative of this inherited predisposition to colorectal cancer in 68 unrelated kindreds. Twenty-nine of the 48 rearrangements were found in MSH2, 13 in MLH1, 2 in MSH6, and 4 in PMS2. The vast majority were deletions, although one previously described large inversion, an intronic insertion, and a more complex rearrangement also were found. Twenty-four deletion breakpoints have been identified and sequenced in order to determine the underlying recombination mechanisms. Most fall within repetitive sequences, mainly Alu repeats, in agreement with the differential distribution of deletions between the MSH2 and MLH1 genes: the higher number and density of Alu repeats in MSH2 corresponded with a higher incidence of genomic rearrangement at this disease locus when compared with other MMR genes. Long interspersed nuclear element (LINE) repeats, relatively abundant in, for example, MLH1, did not seem to contribute to the genesis of the deletions, presumably because of their older evolutionary age and divergence among individual repeat units when compared with short interspersed nuclear element (SINE) repeats, including Alu repeats. Moreover, Southern blot analysis of the introns and the genomic regions flanking the MMR genes allowed us to detect 6 novel genomic rearrangements that left the coding region of the disease-causing gene intact. These rearrangements comprised 4 deletions upstream of the coding region of MSH2 (3 cases) and MSH6 (1 case), a 2-kb insertion in intron 7 of PMS2, and a small (459-bp) deletion in intron 13 of MLH1. The characterization of these genomic rearrangements underlines the importance of genomic deletions in the etiology of HNPCC and will facilitate the development of PCR-based tests for their detection in diagnostic laboratories.

Purpose TGFBR1☆6A is a tumor susceptibility gene that increases breast, colon, and ovarian cancer risk. Fourteen percent of the general population carries TGFBR1☆6A, and TGFBR1☆6A homozygotes have a greater than 100% increased colon cancer risk compared with noncarriers. Low-penetrance genes such as TGFBR1☆6A may account for a sizable proportion of familial colorectal cancer occurrences. To test this hypothesis, we determined whether TGFBR1☆6A contributes to a proportion of mismatch repair (MMR) gene mutation–negative hereditary nonpolyposis colorectal cancer (HNPCC) patients. Patients and Methods A case-case study was performed of 208 index patients with HNPCC meeting the Amsterdam criteria. Patients were examined for mutations and genomic rearrangements in the MLH1, MSH2, and MSH6 genes and genotyped for TGFBR1☆6A. Tumor microsatellite instability status was available for 95 patients. Results A total of 144 patients (69.2%) carried a deleterious mutation and were classified as positive for MMR gene mutation; 64 patients (30.8%) had no evidence of mutations and were classified as MMR negative. TGFBR1☆6A allelic frequency was significantly higher among MMR-negative patients (0.195) than among MMR-positive patients (0.104; P = .011). The proportion of TGFBR1☆6A homozygotes was nine-fold higher among MMR-negative (6.3%) than among MMR-positive patients (0.7%; P = .032). The highest TGFBR1☆6A allelic frequency was found among MMR-negative patients with tumors exhibiting no microsatellite instability (0.211), and the lowest frequency was found among MMR-positive patients with tumors exhibiting microsatellite instability (0.121); the difference was not statistically significant (P = .17). Conclusion TGFBR1☆6A may be causally responsible for a proportion of HNPCC occurrences.

Contains fulltext : 48879.pdf (Publisher’s version ) (Closed access) OBJECTIVE: To investigate the contribution of MYH associated polyposis coli (MAP) among polyposis families in the Netherlands, and the prevalence of colonic and extracolonic manifestations in MAP patients. METHODS: 170 patients with polyposis coli, who previously tested negative for APC mutations, were screened by denaturing gradient gel electrophoresis and direct sequencing to identify MYH germline mutations. RESULTS: Homozygous and compound heterozygous MYH mutations were identified in 40 patients (24%). No difference was found in the percentage of biallelic mutation carriers between patients with 10-99 polyps or 100-1000 polyps (29% in both groups). Colorectal cancer was found in 26 of the 40 patients with MAP (65%) within the age range 21 to 67 years (median 45). Complete endoscopic reports were available for 16 MAP patients and revealed five cases with gastro-duodenal polyps (31%), one of whom also presented with a duodenal carcinoma. Breast cancer occurred in 18% of female MAP patients, significantly more than expected from national statistics (standardised morbidity ratio = 3.75). CONCLUSIONS: Polyp numbers in MAP patients were equally associated with the attenuated and classical polyposis coli phenotypes. Two thirds of the MAP patients had colorectal cancer, 95% of whom were older than 35 years, and one third of a subset of patients had upper gastrointestinal lesions. Endoscopic screening of the whole intestine should be carried out every two years for all MAP patients, starting from age 25-30 years. The frequent occurrence of additional extraintestinal manifestations, such as breast cancer among female MAP patients, should be thoroughly investigated.

TGFBR1*6A is a common polymorphism of the type I transforming growth factor beta receptor (TGFBR1). Epidemiological studies suggest that TGFBR1*6A may act as a tumor susceptibility allele. How TGFBR1*6A contributes to cancer development is largely unknown.To determine whether TGFBR1*6A is somatically acquired by primary tumors and metastases during cancer development and whether the 3-amino acid deletion that differentiates TGFBR1*6A from TGFBR1 is part of the mature receptor or part of the signal sequence and to investigate TGFBR1*6A signaling in cancer cells.Tumor and germline tissues from 531 patients with a diagnosis of head and neck, colorectal, or breast cancer recruited from 3 centers in the United States and from 1 center in Spain from June 1, 1994, through June 30, 2004. In vitro translation assays, MCF-7 breast cancer cells stably transfected with TGFBR1*6A, TGFBR1, or the vector alone, DLD-1 colorectal cancer cells that endogenously carry TGFBR1*6A, and SW48 colorectal cancer cells that do not carry TGFBR1*6A.TGFBR1*6A somatic acquisition in cancer. Determination of the amino terminus of the mature TGFBR1*6A and TGFBR1 receptors. Determination of TGF-beta-dependent cell proliferation.TGFBR1*6A was somatically acquired in 13 of 44 (29.5%) colorectal cancer metastases, in 4 of 157 (2.5%) of colorectal tumors, in 4 of 226 (1.8%) head and neck primary tumors, and in none of the 104 patients with breast cancer. TGFBR1*6A somatic acquisition is not associated with loss of heterozygosity, microsatellite instability, or a mutator phenotype. The signal sequences of TGFBR1 and TGFBR1*6A are cleaved at the same site resulting in identical mature receptors. TGFBR1*6A may switch TGF-beta growth inhibitory signals into growth stimulatory signals in MCF-7 breast cancer cells and in DLD-1 colorectal cancer cells.TGFBR1*6A is somatically acquired in 29.5% of liver metastases from colorectal cancer and may bestow cancer cells with a growth advantage in the presence of TGF-beta. The functional consequences of this conversion appear to be mediated by the TGFBR1*6A signal sequence rather than by the mature receptor. The results highlight a new facet of TGF-beta signaling in cancer and suggest that TGFBR1*6A may represent a potential therapeutic target in cancer.

Contains fulltext : 57394.pdf (Publisher’s version ) (Closed access) The morphological features of neoplastic cells, combined with a stromal reaction, determine the presence of cancer at the microscopic level. Malignant tumours arise through a series of genetic alterations, but these do not entirely explain invasive and metastatic behaviour and correlate only weakly with morphological changes. In order to understand the relationship between the morphology of cancer tissue, gene expression, and clinical behaviour, a study of radiation-induced mucinous rectal carcinoma was performed. Short-term radiotherapy of rectal carcinoma results in an increased incidence of mucinous carcinoma. A cohort of rectal carcinomas (n = 1304), from patients who participated in a randomized radiotherapy trial, was evaluated for the presence and amount of a mucinous component. The results were compared with data from the pre-irradiation biopsies and revealed the presence of two distinct classes of mucinous carcinoma in the radiotherapy group, namely pre-existing (un-induced; n = 24) and induced mucinous carcinoma (n = 29). Clinical data, pathological parameters, and immunohistochemical data from these patients and their tumours showed that induced mucinous carcinomas were more comparable to typical adenocarcinomas than to pre-existing mucinous carcinomas. The prognosis of patients with induced mucinous carcinoma was significantly better than that of patients with pre-existing mucinous carcinomas (91.2% versus 39.3% recurrence-free interval at 2 years, p = 0.02). Gene expression profiles of the different groups of mucinous carcinomas and adenocarcinomas were analysed using Affymetrix Human Cancer Chips. Surprisingly, despite the difference in prognosis, the expression profile of radiation-induced mucinous carcinomas was very closely related to that of their un-induced counterparts. It is shown in the present study that radiation therapy of rectal cancer leads within a few days to substantial changes in both morphology and expression profile. However, the morphology of the pre-therapy biopsy predicts patient survival far better than post-therapy expression profiles. It is concluded that tumour morphology equates to expression profile, but that external factors might influence both, leading to sub-optimal prognostication.

It is well established that concentration gradients of signaling molecules (the so-called "morphogens") organize and pattern tissues in developing animals. In particular, studies in Drosophila and different vertebrates have shown that gradients of the Wnt, Hedgehog (Hh) and transforming growth factor-beta (TGF-β) families of morphogens play critical roles in limb patterning. Morphogens are often expressed in organizing centres and can act over a long range to coordinate the patterning of an entire field of cells. These observations imply that exposure to different concentrations of these diffusible factors may trigger differential cellular responses. In order to study these dosage-dependent Wnt/β-catenin signaling effects, we have generated several hypomorphic mutant alleles at the mouse Apc locus and studied their cellular and phenotypic outcomes in stem cell renewal and differentiation, and in tumorigenesis. The results clearly show that Apc mutations differentially affect the capacity of stem cells to differentiate in a dosage-dependent fashion. Likewise, different Apc mutations (and the corresponding Wnt signaling dosages) confer different degrees of susceptibility to tumorigenesis in the corresponding mouse models. These results have implications for the understanding of the molecular and cellular basis of tumor initiation by defects in the Wnt pathway. We propose a model in which adult somatic stem cell compartments are characterized by tissue-specific β-catenin threshold levels for cell proliferation, differentiation and apoptosis. Different APC mutations will result in different levels of β-catenin signaling, thus conferring different degrees of tumor susceptibility in different tissues. Hence, β-catenin dosage - dependent effects may not only explain how a single pathway is involved in the development and homeostasis of different tissues, but also its pleiotrophic role in tumorigenesis.

Hereditary nonpolyposis colorectal cancer (HNPCC), also known as Lynch syndrome, is caused by mutations in the mismatch repair genes and confers an extraordinarily high risk of colorectal, endometrial, and other cancers. However, while carriers of these mutations should be identified, counseled, and offered clinical surveillance, at present the mutations are not tested for in mutation analyses.To describe the prevalence of a large genomic deletion encompassing exons 1 to 6 of the MSH2 gene that is widespread in the US population as a result of a founder effect.Ongoing genealogical and historical study conducted to assess the origin and spread of an MSH2 mutation previously identified in 9 apparently unrelated families with putative HNPCC and living in widely different geographic locations in the United States.Classification of family members as carriers or noncarriers of the MSH2 mutation; spread of the mutation across the continental United States.To date, 566 family members of the 9 probands have been identified to be at risk and counseled; 137 of these have been tested, and 61 carry the founder mutation. Three families have been genealogically shown to descend from a German immigrant family that arrived and first settled in Pennsylvania in the early 1700s. Movements of branches of the family from Pennsylvania through North Carolina, Alabama, Kentucky, Missouri, Iowa, Nebraska, Utah, Texas, and California have been documented, and carriers of the mutation have already been diagnosed in 14 states. In contrast, the deletion was not found among 407 European and Australian families with HNPCC.The postulated high frequency and continent-wide geographic distribution of a cancer-predisposing founder mutation of the MSH2 gene in a large, outbred (as opposed to genetically isolated) population, and the ease with which the mutation can be detected, suggest that the routine testing of individuals at risk for HNPCC in the United States should include an assay for this mutation until more is learned about its occurrence.

Comparative genomic hybridization by means of BAC microarrays (array CGH) allows high-resolution profiling of copy-number aberrations in tumor DNA. However, specific genetic lesions associated with small but clinically relevant tumor areas may pass undetected due to intra-tumor heterogeneity and/or the presence of contaminating normal cells. Here, we show that the combination of laser capture microdissection, phi29 DNA polymerase-mediated isothermal genomic DNA amplification, and array CGH allows genomic profiling of very limited numbers of cells. Moreover, by means of simple statistical models, we were able to bypass the exclusion of amplification distortions and variability prone areas, and to detect tumor-specific chromosomal gains and losses. We applied this new combined experimental and analytical approach to the genomic profiling of colorectal adenomatous polyps and demonstrated our ability to accurately detect single copy gains and losses affecting either whole chromosomes or small genomic regions from as little as 2 ng of DNA or 1000 microdissected cells.

Background & Aims: Hereditary nonpolyposis colorectal carcinoma (HNPCC) is caused by a mutated mismatch repair (MMR) gene. The aim of our study was to determine the cumulative risk of developing cancer in a large series of MSH6 mutation carriers. Methods: Mutation analysis was performed in 20 families with a germline mutation in MSH6. We compared the cancer risks between MSH6 and MLH1/MSH2 mutation carriers. Microsatellite instability (MSI) analysis and immunohistochemistry (IHC) were performed in the available tumors. Results: A total of 146 MSH6 mutation carriers were identified. In these carriers, the cumulative risk for colorectal carcinoma was 69% for men, 30% for women, and 71% for endometrial carcinoma at 70 years of age. The risk for all HNPCC-related tumors was significantly lower in MSH6 than in MLH1 or MSH2 mutation carriers (P = 0.002). In female MSH6 mutation carriers, the risk for colorectal cancer was significantly lower (P = 0.0049) and the risk for endometrial cancer significantly higher (P = 0.02) than in MLH1 and MSH2 mutation carriers. In male carriers, the risk for colorectal cancer was lower in MSH6 mutation carriers, but the difference was not significant (P = 0.0854). MSI analysis in colorectal tumors had a sensitivity of 86% in predicting a MMR defect. IHC in all tumors had a sensitivity of 90% in predicting a mutation in MSH6. Conclusions: We recommend starting colonoscopic surveillance in female MSH6 mutation carriers from age 30 years. Prophylactic hysterectomy might be considered in carriers older than 50 years. MSI and IHC analysis are sensitive tools to identify families eligible for MSH6 mutation analysis.

Human mesenchymal stem cells (hMSCs) from the bone marrow represent a potential source of pluripotent cells for autologous bone tissue engineering. We previously discovered that over activation of the Wnt signal transduction pathway by either lithium or Wnt3A stimulates hMSC proliferation while retaining pluripotency. Release of Wnt3A or lithium from porous calcium phosphate scaffolds, which we use for bone tissue engineering, could provide a mitogenic stimulus to implanted hMSCs. To define the proper release profile, we first assessed the effect of Wnt over activation on osteogenic differentiation of hMSCs. Here, we report that both lithium and Wnt3A strongly inhibit dexamethasone-induced expression of the osteogenic marker alkaline phosphatase (ALP). Moreover, lithium partly inhibited mineralization of hMSCs whereas Wnt3A completely blocked it. Time course analysis during osteogenic differentiation revealed that 4 days of Wnt3A exposure before the onset of mineralization is sufficient to block mineralization completely. Gene expression profiling in Wnt3A and lithium-exposed hMSCs showed that many osteogenic and chondrogenic markers, normally expressed in proliferating hMSCs, are downregulated upon Wnt stimulation. We conclude that Wnt signaling inhibits dexamethasone-induced osteogenesis in hMSCs. In future studies, we will try to limit release of lithium or Wnt3A from calcium phosphate scaffolds to the proliferative phase of osteogenesis.

Contains fulltext : 49223.pdf (Publisher’s version ) (Closed access) PURPOSE: Radiotherapy is a very effective adjuvant treatment for rectal cancer with little side effects. Its killing effect on tumor cells seems to be more profound than the effect on normal tissue. The molecular events caused by irradiation are mainly analyzed in in vitro and animal models; investigations on human material are rare. In the current study, we analyzed the effects of irradiation on gene expression in normal and tumor tissue of rectal cancer patients. METHODS AND MATERIALS: Normal and carcinoma tissue of patients from a randomized clinical trial of the benefits of preoperative radiotherapy were analyzed using the Affymetrix Human Cancer Gene Chip. Preoperative radiotherapy was given within 5 days prior to surgery. Results for normal tissue and tumor were compared to investigate the radiation-related differences between normal and tumor cells. We clustered the differentially expressed genes based on their functional annotation. Results were compared with immunohistochemical and literature data. RESULTS: The majority of the investigated cancer-related genes remained unchanged by irradiation (92% in tumor tissue and 93% in normal tissue). The differentially expressed genes varied between tumor and normal tissue except for maspin and IL-8. Both in tumor and normal tissue, differentially expressed genes were present related to cell signaling and cycle control, apoptosis and cell survival and tissue response and repair. However, the spectrum of affected genes was totally different. CONCLUSION: Pre-existing differences in gene expression between normal tissue and tumor tissue might explain the differences in their responses to radiation. This change in response may explain the clinical beneficial effect of radiotherapy on tumor cells (low local recurrence rate) and the less severe effects on normal tissue (minor side effects).

Aggressive fibromatosis (desmoid tumor) is a locally invasive soft tissue neoplasm associated with mutations resulting in beta-catenin-mediated transcriptional activation. This tumor is composed of cells with histological and molecular characteristics common to proliferating mesenchymal cells of dermal wounds. Using immunohistochemistry and RT-PCR, we show that Rhamm, a protein with an important role in wound healing and neoplastic progression, is also expressed at high levels in aggressive fibromatosis. A mouse harboring a targeted deletion in Rhamm was generated, resulting in viable Rhamm-/- animals. Rhamm-/- mice were crossed with Apc/Apc1638N mice, which harbor a targeted mutation in the Apc gene predisposing animals to gastrointestinal and aggressive fibromatosis tumors. Rhamm deficiency significantly decreased the number of aggressive fibromatosis tumors formed, but did not alter the number of gastrointestinal polyps. Cell culture studies show that Rhamm regulates cell proliferation in both fibroblasts and fibromatosis cells under conditions of low density, but not high density. These results suggest that Rhamm regulates proliferation of cells with sparse cell-cell contacts, such as occurs in aggressive fibromatosis; provides the first genetic evidence implicating Rhamm in tumor pathology; and suggest Rhamm blockade as a potential therapeutic target for this otherwise difficult-to-treat neoplasm.

Context : In hereditary cancer syndrome families with an identified cancer associated mutation, mutation testing changes the carrier risk status of the tested person and may change the carrier risk status of relatives. Objective : This study aimed to describe the change in the distribution of carrier risk status resulting from testing in hereditary breast-ovarian cancer (HBOC) and hereditary non-polyposis colorectal cancer (HNPCC) families. Design : This was an observational cohort study. Patients : The cohort included members of 75 HBOC and 47 HNPCC families. Of the 10 910 cohort members, 1408 were tested for a mutation and learned their test results. Outcome measure : Carrier risk for all cohort members was assessed before and after mutation testing. Results : There was a change in carrier risk status in 2906 subjects after testing of 1408 family members. The most common type of carrier risk change, from at risk to non-carrier status, accounted for 77% of the risk changes; 12% were a change to known carrier status from a lower risk. Sixty percent of persons with a carrier risk status change were not themselves tested; their risk status changed because of a relative’s test result. Conclusions : Carrier risk status changes from uncertainty to certainty (that is, to carrier or to non-carrier) account for 89% of risk changes resulting from testing. These risk changes affect cancer prevention recommendations, most commonly reducing their burden. Current practices do not ensure that untested family members are informed about changes in their carrier risk status which result from mutation testing of their relatives.

At present, limiting factors in the use of tissue microarrays (TMAs) for high-throughput analysis relate to the visual evaluation of the staining patterns of each of the individual cores in the array and to the subsequent input of the results into a database. Such a database is essential to correlate the data with tumor type and outcome, and to evaluate the performance against other markers achieved in separate experiments. So far, these steps are mostly performed by hand, and consequently are time-consuming and potentially prone to bias and errors, respectively. This paper describes the use of a high-resolution flat-bed scanner for digitization of TMAs with a resolution of about 5 x 5 micro m(2). The arrays are acquired, the positions of the tissue cores are automatically determined, and measurement data including the images of the individual cores are archived. The program provides digital zooming of arrays for interactive verification of the results and rapid linkage of individual core images to data sets of other markers derived from the same array. Performance of the system was compared to manual classification for a representative set of arrays containing colorectal tumors stained with different markers.

Serrated adenomas, hyperplastic polyps, and admixed hyperplastic/adenomatous polyps form a distinct group of colorectal tumors, the molecular genetic basis of which is still poorly understood. We describe a novel mouse model for serrated adenomas and mixed polyposis, here referred to as Sad (serrated adenomas), caused by a spontaneously risen splice site mutation in the murine Smad4 gene. The Sad chromosomal region was identified by genetic linkage and loss of heterozygosity (LOH) analysis. Subsequently, several candidate genes were investigated by expression and mutation analysis. By use of genetic linkage and LOH analysis, we mapped the Sad candidate to mouse chromosome 18, 44 – 48 cM, syntenic to human chromosome band 18q21. Within this chromosomal interval, the Smad2, Smad4, and Smad7 genes were analyzed for the presence of a disease-causing mutation in affected animals. A single nucleotide (nt) deletion was identified in the intron 5/exon 6 splice acceptor site of the Smad4 gene. The single base deletion results in a frameshift and an early termination codon through activation of a cryptic splice site 4 nt downstream in exon 6. The resulting mRNA is unstable, and the Sad mutation is thus likely to represent a null allele. Identification of a Smad4 mutation in the Sad mouse model provides further support for the involvement of the Smad genes, and thus the TGFB pathway, in the serrated/hyperplastic route to colorectal cancer. © 2003 Wiley-Liss, Inc.

Mutations in the currently known mismatch repair genes cannot explain all cases of hereditary nonpolyposis colorectal cancer (HNPCC), and novel predisposing genes are actively sought. Recently, mutations in the DNA repair gene EXO1 have been implicated in HNPCC. One truncating and several missense changes were observed in familial colorectal cancer (CRC) cases but not in controls. We evaluated a series of European CRC patients and population controls to clarify whether EXO1 variants may indeed predispose to familial CRC. Several variants observed in patients were also observed in controls with similar frequencies, including the truncating variant proposed previously to be a disease-causing mutation. Thus, little evidence was obtained to support a major causative role of EXO1 in HNPCC, although we cannot exclude a role for EXO1 as a low penetrance cancer susceptibility or modifying gene.

The recognized urologic tumor spectrum in hereditary non-polyposis colon cancer includes ureteral and renal pelvis malignancies. Here, we report a family in which the proband, who had three metachronous adenocarcinomas of the colon and rectum (at ages 54, 57, and 60), presented with an adenocarcinoma of the prostate at age 61. Immunohistochemical (IHC) staining of colonic, rectal, and prostatic tumor tissues demonstrated lack of expression of both MSH2 and MSH6. Accordingly, microsatellite instability (MSI) was found in the rectal, colonic, and prostatic tumors. The kindred complies with the Amsterdam criteria for HNPCC, as five members over three generations had colorectal cancer. Molecular investigations were initiated when the proband's son presented with an adenocarcinoma of the colon at age 35. Southern blotting analysis of genomic DNA led to identification of a novel genomic deletion encompassing exon 5 of the MSH2 gene. Although prostate cancer has occasionally been described in HNPCC families, to the best of our knowledge, this is the first report where the MSI and IHC analysis of the prostatic adenomcarcinoma clearly link its aetiology to the germline mismatch repair mutation. Hence, prostate cancer should be included in the HNPCC tumor spectrum.

The two most common inherited forms of colorectal cancer are familial adenomatous polyposis and hereditary non-polyposis colorectal cancer. Simultaneous inheritance of both an APC gene mutation and a mismatch repair gene (for example, MLH1) mutation has never been described. In the present case report, we report rapidly progressive adenomatous polyposis in a 10 year old boy with a germline frame shift mutation in the APC gene and a germline splice site mutation in the MLH1 gene. Immunohistochemical investigations showed abnormal expression of beta-catenin in early adenomas with low grade dysplasia, attributed to the APC gene mutation. Subsequent loss of function of the MLH1 gene, as shown by absent immunostaining of its protein in adenomas with high grade dysplasia, may well have caused the rapid progression to high grade dysplasia in many of the adenomas.

Genomic deletions of the MSH2 gene are a frequent cause of hereditary nonpolyposis colorectal cancer (HNPCC), a common hereditary predisposition to the development of tumors in several organs including the gastrointestinal and urinary tracts and endometrium. The mutation spectrum at the MSH2 gene is extremely heterogeneous because it includes nonsense and missense point mutations, small insertions and deletions leading to frameshifts, and larger genomic deletions, the latter representing approximately 25% of the total mutation burden. Here, we report the identification and molecular characterization of the first paracentric inversion of the MSH2 locus known to cause HNPCC. Southern blot analysis and inverse PCR showed that the centromeric and telomeric breakpoints of the paracentric inversion map within intron 7 and to a contig 10 Mb 3' of MSH2, respectively. Pathogenicity of the paracentric inversion was demonstrated by conversion analysis. The patient's lymphocytes were employed to generate somatic cell hybrids to analyze the expression of the inverted MSH2 allele in an Msh2-deficient rodent cellular background. The inversion was shown to abolish MSH2 expression by both northern and western analysis. This study confirms that Southern blot analysis still represents a useful and informative tool to screen for and identify complex genomic rearrangements in HNPCC. Moreover, monoallelic expression analysis represents an attractive approach to demonstrate pathogenicity of unusual mutations in autosomal dominant hereditary conditions.

Mutations in the adenomatous polyposis coli (APC) gene are not only responsible for familial adenomatous polyposis (FAP), but also play a rate-limiting role in the majority of sporadic colorectal cancers. Colorectal tumours are known to arise through a gradual series of histological changes, the so-called 'adenoma-carcinoma' sequence, each accompanied by a genetic alteration in a specific oncogene or tumour suppressor gene. Loss of APC function triggers this chain of molecular and histological changes. In general, an intestinal cell needs to comply with two essential requirements to develop into a cancer: it must acquire selective advantage to allow for the initial clonal expansion, and genetic instability to allow for multiple hits at other genes responsible for tumour progression and malignant transformation. Inactivation of APC seems to fulfill both requirements. In this short review, I will discuss the role played by APC in providing, when mutated, selective advantage, through constitutional activation of the Wnt signal transduction pathway, and chromosomal instability to the nascent intestinal tumor cell.

IMPORTANCE Use of aspirin (which inhibits platelet function) after a colon cancer diagnosis is associated with improved overall survival. Identifying predictive biomarkers of this effect could individualize therapy and decrease toxic effects. OBJECTIVE To demonstrate that survival benefit associated with low-dose aspirin use after a diagnosis of colorectal cancer might depend on HLA class I antigen expression. DESIGN, SETTING, AND PARTICIPANTS A cohort study with tumor blocks from 999 patients with colon cancer (surgically resected between 2002 and 2008), analyzed for HLA class I antigen and prostaglandin endoperoxide synthase 2 (PTGS2) expression using a tissue microarray. Mutation analysis of PIK3CA was also performed. Data on aspirin use after diagnosis were obtained from a prescription database. Parametric survival models with exponential (Poisson) distribution were used to model the survival. MAIN OUTCOMES AND MEASURES Overall survival. RESULTS The overall survival benefit associated with aspirin use after a diagnosis of colon cancer had an adjusted rate ratio (RR) of 0.53 (95% CI, 0.38-0.74; P < .001) when tumors expressed HLA class I antigen compared with an RR of 1.03 (0.66-1.61; P = .91) when HLA antigen expression was lost. The benefit of aspirin was similar for tumors with strong PTGS2 expression (0.68; 0.48-0.97; P = .03), weak PTGS2 expression (0.59; 0.38-0.97; P = .02), and wild-type PIK3CA tumors (0.55; 0.40-0.75; P < .001). No association was observed with mutated PIK3CA tumors (0.73; 0.33-1.63; P = .44). CONCLUSIONS AND RELEVANCE Contrary to the original hypothesis, aspirin use after colon cancer diagnosis was associated with improved survival if tumors expressed HLA class I antigen. Increased PTGS2 expression or the presence of mutated PIK3CA did not predict benefit from aspirin. HLA class I antigen might serve as a predictive biomarker for adjuvant aspirin therapy in colon cancer.

Beta-catenin has a dual role in the cell. At the membrane, it connects E-cadherin to the actin cytoskeleton, while in the nucleus, it controls gene expression in concert with Tcf-like transcription factors. Nuclear translocation of beta-catenin is induced by the Wnt signal transduction pathway. Control of this process is essential since elevated beta-catenin levels interfere with differentiation and development, and can initiate cancer in many tissues. An important role for beta-catenin during hair follicle related development and tumorigenesis has recently been established, though little is known of its endogenous expression during the development of these structures. Here, we have investigated the expression of beta-catenin in relation to markers for proliferation, differentiation and Wnt signaling during the development of three hair follicle related structures, i.e. whiskers, normal body hair and the preputial gland, and a hair follicle-derived tumor, the epidermal cyst. We observed nuclear accumulation of beta-catenin, the hallmark of Wnt signaling, in the upper matrix, the dermal papilla, the developing ringwulst of the whisker and in the tumor, though it was never in association with proliferation or terminal differentiation. Co-localization of nuclear beta-catenin with Tcf-3/4 was found only in the dermal papilla and the developing ringwulst of the whisker, but not in the upper matrix or in the tumor. These results further elucidate the role of the Wnt signal transduction pathway during hair follicle related development and tumorigenesis and illustrate the dynamic role of beta-catenin in signal transduction and cell-adhesion.

Colorectal cancer arises through a gradual series of histological changes, each of which is accompanied by a specific genetic alteration. In general, an intestinal cell needs to comply with two essential requirements to develop into a cancer: it must acquire selective advantage to allow for the initial clonal expansion, and genetic instability to allow for multiple hits in other genes that are responsible for tumour progression and malignant transformation. Inactivation of APC - the gene responsible for most cases of colorectal cancer - might fulfil both requirements.

Mutation searching was performed in the hMSH2 and hMLH1 genes in 20 Portuguese families representing 124 registered affected individuals. Of the 20, 16 fulfilled the classic 'Amsterdam' criteria for HNPCC, whereas the remaining four families satisfied a modified set of criteria. These criteria required a CRC diagnosed before age 50 years and cancers diagnosed in two other relatives within the HNPCC spectrum. A multi-method approach was performed using the protein truncation test (PTT), single strand conformation polymorphism (SSCP) with two different sets of conditions, heteroduplex analysis (HA) and denaturing gradient gel electrophoresis (DGGE). Putative phenotype-genotype correlations were also explored. Ten different germline mutations were identified. Six of these were found in hMLH1 in seven families and four in hMSH2 in four families. SSCP and DGGE had the highest diagnostic yields with the percentage of variants detected above 67% and together HA and PTT had the lowest. No single technique detected all variants. Trends for the absence of extracolonic manifestations were observed in families carrying hMLH1 germline mutations (four of seven in hMLH1 vs one of four in hMSH2). Most of the families with rectal cancer were associated with hMLH1 (six of seven in hMLH1 vs two of four in hMSH2). A multi-technique approach is necessary to identify a high percentage of germline mutations. Seven novel mutations were found in this Portuguese population.

The APC gene, originally identified as the gene for familial adenomatous polyposis (FAP), is now considered as the true "gatekeeper" of colonic epithelial proliferation. Its main tumor suppressing activity seems to reside in the capacity to properly regulate intracellular beta-catenin signaling. Most somatic APC mutations are detected between codons 1286 and 1513, the mutation cluster region (MCR). This clustering can be explained either by the presence of mutation-prone sequences within the MCR, or by the selective advantage provided by the resulting truncated polypeptides. Here, a Msh2-deficient mouse model (Msh2(delta 7N) ) was generated and bred with Apc(1638N) and Apc(Min) that allowed the comparison of the somatic mutation spectra along the Apc gene in the different allelic combinations. Mutations identified in Msh2(delta 7N/delta 7N) tumors are predominantly dinucleotide deletions at simple sequence repeats leading to truncated Apc polypeptides that partially retain the 20 a.a. beta-catenin downregulating motifs. In contrast, the somatic mutations identified in the wild type Apc allele of Msh2(delta 7N/delta 7N) /Apc(+/1638N) and Msh2(delta 7N/delta 7N) /Apc(+/Min) tumors are clustered more to the 5' end, thereby completely inactivating the beta-catenin downregulating activity of APC. These results indicate that somatic Apc mutations are selected during intestinal tumorigenesis and that inactivation of the beta-catenin downregulating function of APC is likely to represent the main selective factor.

Background & Aims: Inactivation of the adenomatous polyposis coli ( APC ) gene is observed at early stages of intestinal tumor formation, whereas loss of E-cadherin is usually associated with tumor progression. Because both proteins compete for the binding to β-catenin, an essential component of the Wnt signaling pathway, reduction of E-cadherin levels in an Apc mouse model could influence both tumor initiation and progression. In addition, loss or haploinsufficiency of E-cadherin may affect tumorigenesis by altering its cell-adhesive and associated functions. Methods: Apc1638N mice were bred with animals carrying a targeted E-cadherin knockout mutation. Results: Double heterozygous animals showed a significant 9-fold and 5-fold increase of intestinal and gastric tumor numbers, respectively, compared with Apc 1638N animals. The intestinal tumors of both groups showed no significant differences in grading and staging. Loss of heterozygosity analysis at the Apc and E-cadherin loci in both intestinal and gastric Apc +/1638N / E-cad +/− tumors revealed loss of the wild-type Apc allele in most cases, whereas the wild-type E-cadherin allele was always retained. This was supported by a positive, although reduced, staining for E-cadherin of intestinal tumor sections. Conclusions: Introduction of the E-cadherin mutation in Apc 1638N animals enhances Apc -driven tumor initiation without clearly affecting tumor progression. GASTROENTEROLOGY 2000;119:1045-1053

The effect of the genetic background on the tumor spectrum of Apc1638N, a mouse model for attenuated familial adenomatous polyposis (FAP), has been investigated in X-irradiated and untreated F1 hybrids between C57BL/6JIco- Apc1638N (B6) and A/JCrIBR (A/J), BALB/cByJIco (C) or C3H/HeOuJIco (C3). Similar to the Apc(Min) model, the Apc1638N intestinal tumor multiplicity seems to be modulated by Mom1. Moreover, several additional (X-ray- responsive) modifier loci appear also to affect the Apc1638N intestinal tumor number. The genetic background did not significantly influence the number of spontaneous desmoids and cutaneous cysts in Apc1638N. In general, X- irradiation increased the desmoid multiplicity in Apc1638N females but had no effect in males. The opposite was noted for the cyst multiplicity after X- rays. Surprisingly, X-irradiated CB6F1-Apc1638N females were highly susceptible to the development of ovarian tumors, which displayed clear loss of the wild-type Apc allele.

Background Germ-line mutations in DNA mismatch-repair genes (MSH2, MLH1, PIMS1, PMS2, and MSH6) cause susceptibility to hereditary nonpolyposis colorectal cancer. We assessed the prevalence of MSH2 and MLH1 mutations in families suspected of having hereditary nonpolyposis colorectal cancer and evaluated whether clinical findings can predict the outcome of genetic testing. Methods We used denaturing gradient gel electrophoresis to identify MSH2 and MLH1 mutations in 184 kindreds with familiar clustering of colorectal cancer or other cancers associated with hereditary nonpolyposis colorectal cancer. Information on the site of cancer, the age at diagnosis, and the number of affected family members was obtained from all families. Results Mutations of MSH2 or MLH1 were found in 47 of the 184 kindreds (26 percent). Clinical factors associated with these mutations were early age at diagnosis of colorectal cancer, the occurrence in the kindred of endometrial cancer or tumors of the small intestine, a higher number of family members with colorectal or endometrial cancer, the presence of multiple colorectal cancers or both colorectal and endometrial cancers in a single family member, and fulfillment of the Amsterdam criteria for the diagnosis of hereditary nonpolyposis colorectal cancer (at least three family members in two or more successive generations must have colorectal cancer, one of whom is a first-degree relative of the other two; cancer must be diagnosed before the age of 50 in at least one family member; and familial adenomatous polyposis must be ruled out). Multivariate analysis showed that a younger age at diagnosis of colorectal cancer, fulfillment of the Amsterdam criteria, and the presence of endometrial cancer in the kindred were independent predictors of germ-line mutations of MSH2 or MLH1. These results were used to devise a logistic model for estimating the likelihood of a mutation in MSH2 and MLH1. Conclusions Assessment of clinical findings can improve the rate of detection of mutations of DNA mismatch-repair genes in families suspected of having hereditary nonpolyposis colorectal cancer. (N Engl J Med 1998;339:511-8.) (C)1998, Massachusetts Medical Society.

Background & Aims: Germline mutations in the adenomatous polyposis coli ( APC ) gene are responsible for familial adenomatous polyposis (FAP), an autosomal dominant predisposition to the formation of multiple colorectal adenomas. Moreover, patients with FAP are at high risk of developing several extracolonic manifestations, including desmoids, cutaneous cysts, and tumors of the upper gastrointestinal tract. Although by definition desmoids are nonmalignant, because of their aggressive invasion of local structures, they represent one of the major causes of morbidity and mortality among patients with FAP. Methods: This study describes the histopathologic and molecular characterization of Apc 1638N, a mouse model for the broad spectrum of extracolonic manifestations characteristic of FAP. Results: Heterozygous Apc + /Apc 1638N animals develop fully penetrant and multifocal cutaneous follicular cysts and desmoid tumors in addition to attenuated polyposis of the upper gastrointestinal tract. Moreover, breeding of Apc + /Apc 1638N mice in a p53 -deficient background results in a dramatic sevenfold increase of the desmoid multiplicity. Conclusions: Because of the attenuated nature of their intestinal phenotype, these mice survive longer than other murine models for Apc -driven tumorigenesis. Therefore, Apc 1638N represents an ideal laboratory tool to test various therapeutic intervention strategies for the management of intestinal as well as extraintestinal tumors. GASTROENTEROLOGY 1998;114:275-283

SummaryHereditary nonpolyposis colorectal cancer (HNPCC) is a common autosomal dominant cancer-susceptibility condition characterized by early onset colorectal cancer. Germ-line mutations in one of four DNA mismatch repair (MMR) genes, hMSH2, hMLH1, hPMS1, or hPMS2, are known to cause HNPCC. Although many mutations in these genes have been found in HNPCC kindreds complying with the so-called Amsterdam criteria, little is known about the involvement of these genes in families not satisfying these criteria but showing clear-cut familial clustering of colorectal cancer and other cancers. Here, we applied denaturing gradient-gel electrophoresis to screen for hMSH2 and hMLH1 mutations in two sets of HNPCC families, one set comprising families strictly complying with the Amsterdam criteria and another set in which at least one of the criteria was not satisfied. Interestingly, hMSH2 and hMLH1 mutations were found in 49% of the kindreds fully complying with the Amsterdam criteria, whereas a disease-causing mutation could be identified in only 8% of the families in which the criteria were not satisfied fully. In correspondence with these findings, 4 of 6 colorectal tumors from patients belonging to kindreds meeting the criteria showed microsat-ellite instability, whereas only 3 of 11 tumors from the other set of families demonstrated this instability. Although the number of tumors included in the study admittedly is small, the frequencies of mutations in the MMR genes show obvious differences between the two clinical sets of families. These results also emphasize the practical importance of the Amsterdam criteria, which provide a valid clinical subdivision between families, on the basis of their chance of carrying an hMSH2 or an hMLH1 mutation, and which bear important consequences for genetic testing and counseling and for the management of colorectal cancer families.

Transgenic Apc1638N mice, heterozygous for a targeted frameshift mutation at codon 1638 of the endogenous adenomatous polyposis coli (APC) gene, are predisposed to develop multiple adenomas and adenocarcinomas along the intestinal tract and to a number of extra-intestinal lesions including, among others, mammary tumors. We have studied these mice in a short-term carcinogenicity test with 2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (PhIP), a potent murine small intestinal mutagen and lymphomagen. Upon dietary administration of 0.03% PhIP in a short-term (6 months) study, a significantly increased number of small intestinal tumors as well as an increased number of aberrant crypt foci (ACF) were observed in male Apc+/Apc1638N mice compared with untreated transgenic mice. No differences in intestinal and mammary tumor multiplicity were observed between treated and control Apc+/Apc1638N females.

Familial adenomatous polyposis (FAP) is an inherited predisposition to colorectal cancer characterized by the development of numerous adenomatous polyps predominantly in the colorectal region. Germline mutations in the adenomatous polyposis coli (APC) gene are responsible for most cases of FAP. Mutations at the 5' end of APC are known to be associated with a relatively mild form of the disease, called attenuated adenomatous polyposis coli (AAPC). We identified a frameshift mutation in the 3' part of exon 15, resulting in a stop codon at 1862, in a large Dutch kindred with AAPC. Western blot analysis of lymphoblastoid cell lines derived from affected family members from this kindred, as well as from a previously reported Swiss family carrying a frameshift mutation at codon 1987 and displaying a similar attenuated phenotype, showed only the wild-type APC protein. Our study indicates that chain-terminating mutations located in the 3' part of APC do not result in detectable truncated polypeptides and we hypothesize that this is likely to be the basis for the observed AAPC phenotype.

BACKGROUND & AIMS: Hereditary nonpolyposis colorectal cancer is characterized by early-onset colorectal cancer and the occurrence of various other cancers. The recent isolation of four mismatch repair genes responsible for hereditary nonpolyposis colorectal cancer allows for the identification of carriers within affected families. The purpose of this study was to assess the age-specific cancer risk in a large series of gene carriers. METHODS: Thirty-four families were studied by mutation analysis. In 19 of these families, pathogenic mutations were found at hMSH2 or hMLH1. Of 382 relatives, 124 had a mutation in hMLH1 and 86 in hMSH2. RESULTS: The lifetime risk of colorectal cancer was the same in both groups of gene carriers (80%). The risk of endometrial cancer was greater in hMSH2 gene carriers compared with hMLH1 gene carriers (61% vs. 42%), but the difference was not statistically significant. A very high relative risk of cancer of the small bowel (relative risk of >100) was observed in carriers of either gene. Only the carriers of hMSH2 mutations had a significantly increased relative risk of cancer of the urinary tract (kidney and ureter) (relative risk of 75.3), stomach (relative risk of 19.3), and ovaries (relative risk of 8.0). CONCLUSIONS: This study provides estimates of cancer risk that may contribute to the appropriate management of gene carriers within families with hereditary nonpolyposis colorectal cancer. (Gastroenterology 1996 Apr;110(4):1020-7)

The identification and characterization of single nucleotide variations in DNA still represents a common technical obstacle in the detection of DNA damage as well as in the genetic analysis of inherited disorders. The introduction of the polymerase chain reaction (PCR) (Saiki et al., 1988) has greatly facilitated this technical problem:the in vitro production of large amounts of the DNA target makes the application of tedious molecular cloning steps obsolete, and allows the direct determination of the nucleotide sequence of the amplified fragment. However, when approaching the analysis of a large DNA segment, it is often desirable to first perform a screening of overlapping PCR-amplified fragments to establish where the putative nucleotide variant is located. To this aim, several protocols are available based on some physical features of DNA or on the activity of different chemical agents or enzymes capable of recognizing mismatches in double-stranded molecules. Of these protocols, denaturing gradient gel electrophoresis (DGGE) allows the identification of point mutations which alter the melting behavior of the DNA fragment to be analyzed (Fischer and Lerman, 1979, 1983; Myers et al., 1985a).

Germ-line mutations in the adenomatous polyposis coli (APC) gene are responsible for familial adenomatous polyposis (FAP). Genotype-phenotype correlation studies in patients with FAP have demonstrated associations of certain variants of the disease with mutations at specific sites within the APC gene. In a large FAP family, we identified a frameshift mutation located in the alternatively spliced region of exon 9. Phenotypic studies of affected family members showed that the clinical course of FAP was delayed, with gastrointestinal symptoms and death from colorectal carcinoma occurring on average 25 and 20 years later than usual, respectively. The numbers of colorectal adenomas differed markedly among affected individuals and the location of colorectal cancer lay frequently in the proximal colon. Our findings suggest that the exon 9 mutation identified in the pedigree is associated with late onset of FAP. The atypical phenotype may be explained by the site of the mutation in the APC gene. Analysis of the APC protein product indicated that the exon 9 mutation did not result in a detectable truncated APC protein. Given the location of the mutation within an alternatively spliced exon of APC, it is conceivable that normal APC proteins are produced from the mutant allele by alternative splicing.

Germ-line mutations in the human adenomatous polyposis coli (APC) gene result in familial adenomatous polyposis, an autosomal dominant disorder characterized by the early onset of multiple adenomatous polyps in the large bowel with a high likelihood of developing colorectal carcinomas. To understand the role of APC in intestinal tumor formation, we have introduced a chain-termination mutation in the 15th exon of the mouse Apc gene and employed it to modify the endogenous gene by homologous recombination in embryonic stem cells. Mice which are heterozygous for the Apc gene modification progressively develop intestinal tumors in a manner that is similar to that observed in patients with familial adenomatous polyposis and in mice which carry a mutation called multiple intestinal neoplasia (Min). Our results indicate that the Apc gene modification is a critical event in the initiation of intestinal tumor formation and results in an autosomal dominant predisposition toward development of spontaneous colonic and intestinal tumors in mice.

The locus responsible for the childhood-onset proximal spinal muscular atrophies (SMA) has recently been mapped to an area of 2-3 Mb in the region q12-q13.3 of chromosome 5. We have used a series of radiation hybrids (RHs) containing distinct parts of the SMA region as defined by reference markers. A cosmid library was constructed from one RH. Thirteen clones were isolated and five of these were mapped within the SMA region. Both RH mapping and fluorescence in situ hybridization analysis showed that two clones map in the region between loci D5S125 and D5S351. One of the cosmids contains expressed sequences. Polymorphic dinucleotide repeats were identified in both clones and used for segregation analysis of key recombinant SMA families. One recombination between the SMA locus and the new marker 9Ic (D5S685) indicates that 9Ic is probably the closest distal marker. The absence of recombination between the SMA locus and marker Fc (D5S684) suggests that Fc is located close to the disease gene. These new loci should refine linkage analysis in SMA family studies and may facilitate the isolation of the disease gene.

The molecular analysis of genetic diseases relies on several technical approaches which allow genetic and physical mapping, characterization of the gene structure, expression studies, and identification of disease-causing mutations. Denaturing gradient gel electrophoresis (DGGE) allows the rapid screening for single base changes in enzymatically amplified DNA. The technique is based on the migration of double-stranded DNA molecules through polyacrylamide gels containing linearly increasing concentrations of a denaturing agent. In this review DGGE and the several modifications of the original protocol are presented. Moreover, its applications in human molecular genetics are summarized together with a preliminary comparison with other mutation detection technologies such as chemical cleavage, RNase protection, and single-strand conformation polymorphism.

Background: Wnt/beta-catenin signaling plays a regulatory role in uterine development and function. To study this role of Wnt/beta-catenin signaling during embryogenesis in more detail, we employed an AmhR2 promoter-driven C-recombinase (Jamin et al., 2002) to conditionally inactivate the Apc gene in mesenchymal cells surrounding the müllerian duct. As a consequence of Apc inactivation, defects in the destruction complex are expected to result in the intracellular accumulation of beta-catenin and the subsequent constitutive activation of canonical Wnt signaling. Methods: [Apc15Lox/15lox;AmhR2-Cre] conditional Apc knockout mice were generated. Cre expression and AmhR2 promotor activity was verified by staining for beta-galactosidase activity in [AmhR2-LacZ] and [AmhR2-Cre;ROSA26-LacZlox] reporter mice. Furthermore, recombination of the Apc gene was verified for different laser micro-dissected regions of the uterus, from 8-week-old mice, by PCR. Uterine defects were examined by immunohistochemical staining for various uterine markers. Results: It was observed that the Cre-mediated Apc gene deletion mainly took place in the myometrial layers of the uterus. Recombination in the stroma and epithelium of the lumen and glands was low. Microscopically, the affected mice showed a significant reduction in the number of glands and a somewhat disorganized stroma. The main defects, however, were observed in the myometrial layer of the uterus, where clear disorganization of muscle fibres and in 50% of cases visible loss of musculature was apparent. As a consequence of these defects, the mice displayed reduced litter sizes and some mice were incapable of normal delivery. Conclusion: AmhR2-Cre driven embryonic knock-down of Apc results in a defect of the myometrial layer of the uterus. Effects on the endometrium were observed to be less profound. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4208.