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.

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 MWR 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. (c) 2006 Publie par Elsevier SAS.

L’existence d’antécédents familiaux de cancer colorectal (CCR) est, avec l’alimentation, un facteur de risque connu depuis longtemps pour ce cancer. Des études cas-témoins et de cohorte ont montré que le risque était dépendant du degré de parenté avec les malades, du nombre de cas de CCR dans la famille et de l’âge d’apparition du cancer chez les apparentés atteints [1-3]. Une partie de cet excès de cas familiaux peut être expliquée par des formes héréditaires de CCR dont une première description par Warthin [4] a été complétée par Lynch [5], ce syndrome étant actuellement désigné par l’acronyme HNPCC (hereditary non polyposis colorectal cancer) pour le différencier de la polypose adénomateuse familiale. En 1991, un consortium international définit pour ce syndrome des critères diagnostiques, dits d’Amsterdam, dans un but de standardisation : (i) trois apparentés atteints de CCR histologiquement prouvés, un des apparentés devant être lié au premier degré avec les deux autres ; (ii) au moins deux générations successives atteintes ; (iii) un des cancers au moins diagnostiqué avant l’âge de 50 ans ; (iv) polypose familiale exclue [6]. Dès le départ, ces critères ont privilégié la spécificité

Propos. – Le syndrome HNPCC (Hereditary Non Polyposis Colon Cancer) est une prédisposition héréditaire au cancer, dont les critères de reconnaissance reposent sur des informations individuelles et généalogiques (critères d'Amsterdam). Le syndrome HNPCC est lié, dans environ 70 % des cas, à une altération constitutionnelle d'un gène MMR (MisMatch Repair), et les cellules tumorales présentent alors un phénotype particulier appelé MSI (MicroSatellite Instability). Ces formes héréditaires représentent environ 5 % des cancers colorectaux. Les patients atteints de syndrome HNPCC ont un risque élevé de développer des cancers colorectaux et de l'endomètre, et un risque relatif significativement augmenté pour d'autres organes.

The nonsense-mediated decay (NMD) system normally targets mRNAs with premature termination codons (PTCs) for rapid degradation. We investigated for a putative role of NMD in cancers with microsatellite instability (MSI-H cancers), because numerous mutant mRNAs containing PTC are generated in these tumors as a consequence of their mismatch repair deficiency. Using a quantitative RT-PCR approach in a large series of colorectal cancer cell lines, we demonstrate a significantly increased rate of degradation of mutant mRNAs containing a PTC compared with wild-type. A specific siRNA strategy was used to inhibit RENT-1 and/or RENT-2 activity, two major genes in the NMD system. This allowed us to show that increased degradation of PTC-containing mRNAs in MSI-H tumors was partly dependent upon NMD activity. The efficiency of NMD for the degradation of mutant mRNAs from target genes was highly variable in these cancers. NMD degraded some of them (TGFssRII, MSH3, GRK4), although allowing the persistent expression of others (BAX, TCF-4). This is of particular interest within the context of a proposed conservation of biological activity for the corresponding mutated proteins. We thus propose that NMD might play an important role in the selection of target gene mutations with a functional role in MSI-H carcinogenesis.

SummaryPrevious studies have indicated that average telomere length is partly inherited (Slagboom et al., 1994; Rufer et al., 1999) and that there is an inherited telomere pattern in each cell (Graakjaer et al., 2003); (Londoño‐Vallejo et al., 2001). In this study, we quantify the importance of the initially inherited telomere lengths within cells, in relation to other factors that influence telomere length during life. We have estimated the inheritance by measuring telomere length in monozygotic (MZ) twins using Q‐FISH with a telomere specific peptide nucleic acid (PNA)‐probe. Homologous chromosomes were identified using subtelomeric polymorphic markers. We found that identical homologous telomeres from two aged MZ twins show significantly less differences in relative telomere length than when comparing the two homologues within one individual. This result means that towards the end of life, individual telomeres retain the characteristic relative length they had at the outset of life and that any length alteration during the lifespan impacts equally on genetically identical homologues. As the result applies across independent individuals, we conclude that, at least in lymphocytes, epigenetic/environmental effects on relative telomere length are relatively minor during life.

Biallelic NF2 gene inactivation is common in sporadic and in neurofibromatosis type 2 (NF2)-related meningiomas. We show that, beginning at four months of age, thirty percent of mice with arachnoidal cell Cre-mediated excision of Nf2 exon 2 developed a range of meningioma subtypes histologically similar to the human tumors. Additional hemizygosity for p53 did not modify meningioma frequency or progression suggesting that Nf2 and p53 mutations do not synergize in meningeal tumorigenesis. This first mouse model initiated with a genetic lesion found in human meningiomas provides a powerful tool for investigating tumor progression and for the preclinical evaluation of therapeutic interventions.

The subtelomeric domains of chromosomes are probably the most rapidly evolving structures of the human genome. The highly variable distribution of large duplicated subtelomeric segments has indicated that frequent exchanges between nonhomologous chromosomes may have been taking place during recent genome evolution. We have studied the extent and variability of such duplications using in Situ hybridization techniques and a set of well-defined subtelomeric cosmid probes that identify discrete regions within the subtelomeric domain. In addition to reciprocal translocation and illegitimate recombination events that could explain the observed mosaic pattern of subtelomeric regions, it is likely that homology-based recombination mechanisms have also contributed to the spread of distal subtelomeric sequences among particular groups of nonhomologous chromosome arms. The frequency and distribution of large-scale subtelomeric polymorphisms may have direct implications for the design of chromosome-specific probes that are aimed at the identification of cryptic subtelomeric deletions. Furthermore, our results indicate that the relevance of some of the telomere closures proposed within the present Human Genome Sequence draft are restricted to specific allelic variants of unknown frequencies.

The influence of p53 mutations on the response to ionizing radiation and survival was retrospectively evaluated in patients treated with preoperative radiotherapy for rectal carcinoma. From 1989 to 1991, 86 rectal cancer patients treated by preoperative radiotherapy were included in this series. For all patients, endorectal sonography (to define ultrasonography TNM [uTNM]) was performed before treatment; 19 patients were classified as stage I, 27 as stage 2 and 40 as stage 3. Response to radiotherapy (39 Gy in 13 fractions delivered in 17 days) was assessed by comparing the uT and the T obtained by histologic examination of the resected specimen (TNM classification). A rectal cancer biopsy was performed before treatment and enabled the search for p53 mutations by denaturing gradient gel electrophoresis (DGGE) and sequencing. The status of the p53 gene was correlated with the response to radiotherapy and survival. Forty-nine percent of the tumors presented abnormal DGGE profiles. The prevalence of p53 mutations was significantly higher in patients who did not respond to radiotherapy (63%) than in those who did respond (34%) (p < 0.01). Presence of a p53 mutation was associated with significantly shorter 5-year survival compared to patients without mutations (p < 0.02). In a multivariate analysis, p53 mutation status remained a prognostic factor independent of tumor posttreatment staging (p < 0.05). p53 status is an independent prognostic factor of response to radiotherapy and survival in rectal carcinoma.

INTRODUCTIONGermline mutations of theSTK11/LKB1 tumour suppressor gene (19p13.3) are responsible for Peutz-Jeghers syndrome (PJS), a rare genetic disorder, which is dominantly inherited. In addition to the typical hamartomatous gastrointestinal polyps and perioral pigmented lesions, PJS is also associated with the development of tumours in various sites. No specific follow up has yet been evaluated for gene carriers. Furthermore, genetic heterogeneity has been reported, which makes genetic counselling difficult.METHODSWe report here the analysis of the STK11/LKB1 locus in a series of 34 PJS families, combining the search for mutations and rearrangements in the coding sequence, allele specific expression tests, and linkage studies.RESULTSGermline deleterious mutation of the STK11/LKB1 gene were identified in 70% of cases. The hypothesis of a second PJS locus was reinforced and PJS families could be divided into two groups on the basis of the presence or absence of an identifiedSTK11/LKB1 alteration. Analysis of clinical data indicates that the cancer associated risk is markedly different in the two groups. PJS patients with no identifiedSTK11/LKB1 mutation are at major risk for proximal biliary adenocarcinoma, an infrequent tumour in the general population.CONCLUSIONUp to 30% of PJS patients are caused by mutation in an unidentified gene that confers high susceptibility to cancer development.

The neurofibromatosis type 2 (NF2) tumor suppressor protein, known as schwannomin or merlin, is involved in linking membrane proteins to the cytoskeleton. Like the related ERM proteins, schwannomin has long been suspected of exhibiting a complex 3D organization caused by the association of different regions within the protein. Intramolecular interactions characterized to date are linking N-terminal sequences of the protein to C-terminal sequences. Here, we demonstrate, by a biochemical approach, the existence of a structured domain entirely contained within the N-terminal half of schwannomin. This structure, which is resistant to chymotryptic digestion, encompasses the FERM domain (residues 19-314), but excludes the 18 extreme N-terminal residues specific to schwannomin. The structure is disrupted by some, but not all, naturally occurring NF2 mutations. We investigated the significance of this structured domain in schwannomin cellular functions and found that normal schwannomin localization beneath the plasma membrane is directly dependent on proper folding of the N-terminal domain. In addition, folding of the N-terminal domain influences schwannomin interaction with actin through two novel actin-binding sites located in this region. These results suggest that loss of activity of several naturally occurring schwannomin mutants is due to disruption of the fold of the N-terminal domain, leading to loss of both membrane localization and actin association.

A number of human genes containing coding mononucleotide repeat sequences are particularly prone to mutations in tumors with defects in mismatch repair (MMR) genes (MSI-H cancers). In a large series of MSI-H colorectal tumors, we looked for mutations in 25 coding repeats contained in eight genes already known to be mutated in these cancers or in 17 other genes with an expected role in carcinogenesis. Mutations were found in 19 of the 25 candidate genes. Using a maximum likelihood statistical method, they were separated into two different groups that differed significantly in their mutation frequencies, and were likely to represent mutations that do or do not provide selective pressures during MSI-H tumoral progression, respectively. Three new target genes were found (GRB-14, RHAMM, RAD50). Our results provide evidence that MSI-H tumoral progression involves the cumulative mutations of a large number of genes. For each MSI-H tumor we calculated indexes representing the number of mutations found in genes of these groups. We also evaluated a shortening index at both the Bat-25 and Bat-26 non-coding mononucleotide tracts that are known to be almost always unstable in MSI-H cancers. A significant correlation was observed between instability at both coding and non-coding repeats, suggesting that Bat-25 and Bat-26 could be used as simple phenotypical markers of the tumoral evolution. A preferential order of mutations was deduced. During this process, hMSH3 alterations, a target gene encoding for a MMR protein, was found to play an important role by increasing the instability phenomenon characterizing these cancers.

SCHIP1 has been identified as a protein able to associate specifically in vitro and in vivo with the schwannomin (or merlin) protein (Goutebroze et al., 2000), which is the tumor suppressor deficient in neurofibromatosis type 2 (NF2) (Rouleau et al., 1993). NF2 is an autosomal dominant inherited disease that predisposes to the development of multiple nervous system tumors, mainly vestibular schwannomas and meningiomas (Evans et al., 1992). Bi-allelic inactivation of the NF2 gene (22q12) is observed in tumors of NF2 patients, and in sporadically occurring schwannomas and meningiomas (Merel et al., 1995). The NF2 gene is also frequently mutated in primary malignant mesotheliomas (Deguen et al., 1998), which are mesodermally derived tumors induced by exposure to asbestos (Murthy and Testa, 1999). Materials and methods

BACKGROUND & AIMS To evaluate how characterization of genetic alterations can help in the elucidation of liver carcinogenesis pathways, 137 tumors were analyzed. METHODS High-density allelotype, p53, Axin1, and beta-catenin gene mutations were determined. Alterations were analyzed according to clinical parameters. RESULTS Tumors could be divided into 2 groups according to chromosome stability status. In the first group, demonstrating a chromosome stability, beta-catenin mutation associated with chromosome 8p losses were frequently found as the single genetic alterations. beta-catenin mutations were associated with large tumor size and with negative hepatitis B virus status. In the second group, demonstrating a chromosome instability, the most frequent allelic losses were on chromosome 1p, 4q, 6q, 9p, 13q, 16p, 16q, and 17p; Axin1 and p53 were frequently mutated. All of these alterations, except losses on 6q and 9p, were associated with hepatitis B virus infection. P53 mutations, 17p, 13q losses, and a high value of the fractional allelic loss index were associated with poor differentiated tumors, independently of risk factors. Finally, in the whole series, chromosome 9p and 6q losses were associated with poor prognosis. CONCLUSIONS Two main pathways defined by genetic alterations show different risk factors and clinical characteristics. Furthermore, loss of chromosome 9p or 6q is an independent prognostic indicator.

GASTROENTEROLOGY 2001;121:1026-1027

Telomeres are important structures for DNA replication and chromosome stability during cell growth. Telomere length has been correlated with the division potential of human cells and has been found to decrease with age in healthy individuals. Nevertheless, telomere lengths within the same cell are heterogeneous and certain chromosome arms typically have either short or long telomeres. Both the origin and the physiological consequences of this heterogeneity in telomere length remain unknown. In this study we used quantitative telomeric FISH combined with a method to identify the parental origin of chromosomes to show that significant differences in relative telomere intensities are frequently observed between chromosomal homologs in short-term stimulated cultures of peripheral blood lymphocytes. These differences appear to be stable for at least 4 months in vivo, but disappear after prolonged proliferation in vitro. The telomere length differences are also stable during in vitro growth of telomerase-negative fibroblast cells but can be abolished by exogenous telomerase expression in these cells. These findings suggest the existence of a mechanism maintaining differences in telomere length between chromosome homologs that is independent of telomere length itself.

GASTROENTEROLOGY 2001;121:1026-1027

The human T cell transcription factor-4 (hTCF-4) interacts functionally with beta-catenin in the Wnt signaling pathway, which regulates many developmental processes. Moreover, inappropriate reactivation of this pathway attributable to APC or beta-catenin mutations has been described in colorectal cancers. Because only the human TCF-4 cDNA sequence was known, we determined its genomic structure. A total of 17 exons, of which 5 were alternative, were identified. Moreover, four alternative splice sites were observed either experimentally or in silico by a BLAST approach in expressed sequence tag databases. The alternative use of three consecutive exons localized in the 3' part of the hTCF-4 gene changes the reading frames used in the last exon, leading to the synthesis of a number of hTCF-4 isoforms with short, medium, or long-size COOH-terminal ends. We next screened the entire hTCF-4 gene for mutations in a series of 24 colorectal cancer cell lines by denaturing gradient gel electrophoresis and/or direct sequencing. Besides an already described deletion of an A in an (A)9 coding repeat in four cases, we found DNA variants in eight cases for a total of 12 variants, of which 8 were coding. These include one frameshift mutation in the beta-catenin binding domain (exon 1), and one missense mutation in exon 4. In the remaining six cases, nonsense or frameshift mutations were localized in the 3' part of the gene. These latter alterations have as a common consequence to decrease the proportion of the long COOH-terminal hTCF-4 isoform, which contains two binding domains for c-terminal binding protein, a protein implicated in the repression of the TCF family transcriptional activity. Thus, loss of the TCF-4 capacity to interact with COOH-terminal binding protein could be an important event during colorectal carcinogenesis by modifying Wnt signaling.

genesisVolume 26, Issue 2 p. 127-129 ArticleFree Access Targeted expression of Cre recombinase to myelinating cells of the central nervous system in transgenic mice Michiko Niwa-Kawakita, Michiko Niwa-Kawakita INSERM U434, Fondation Jean Dausset-CEPH, Paris, FranceSearch for more papers by this authorVincent Abramowski, Vincent Abramowski INSERM U434, Fondation Jean Dausset-CEPH, Paris, FranceSearch for more papers by this authorMichel Kalamarides, Michel Kalamarides INSERM U434, Fondation Jean Dausset-CEPH, Paris, FranceSearch for more papers by this authorGilles Thomas, Gilles Thomas INSERM U434, Fondation Jean Dausset-CEPH, Paris, FranceSearch for more papers by this authorMarco Giovannini, Corresponding Author Marco Giovannini [email protected] INSERM U434, Fondation Jean Dausset-CEPH, Paris, FranceINSERM U434, Fondation Jean Dausset-CEPH, 27 rue Juliette Dodu, 75010 Paris, FranceSearch for more papers by this author Michiko Niwa-Kawakita, Michiko Niwa-Kawakita INSERM U434, Fondation Jean Dausset-CEPH, Paris, FranceSearch for more papers by this authorVincent Abramowski, Vincent Abramowski INSERM U434, Fondation Jean Dausset-CEPH, Paris, FranceSearch for more papers by this authorMichel Kalamarides, Michel Kalamarides INSERM U434, Fondation Jean Dausset-CEPH, Paris, FranceSearch for more papers by this authorGilles Thomas, Gilles Thomas INSERM U434, Fondation Jean Dausset-CEPH, Paris, FranceSearch for more papers by this authorMarco Giovannini, Corresponding Author Marco Giovannini [email protected] INSERM U434, Fondation Jean Dausset-CEPH, Paris, FranceINSERM U434, Fondation Jean Dausset-CEPH, 27 rue Juliette Dodu, 75010 Paris, FranceSearch for more papers by this author First published: 23 February 2000 https://doi.org/10.1002/(SICI)1526-968X(200002)26:2<127::AID-GENE8>3.0.CO;2-HCitations: 14AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat No abstract is available for this article. LITERATURE CITED Akagi K, Sandig V, Vooijs M, Van der Valk M, Giovannini M, Strauss M, Berns A. 1997. Cre-mediated somatic site-specific recombination in mice. Nucleic Acids Res 25: 1766–1773. 10.1093/nar/25.9.1766 CASPubMedWeb of Science®Google Scholar Goujet-Zalc C, Babinet C, Monge M, Timsit S, Cabon F, Gansmuller A, Miura M, Sanchez M, Pournin S, Mikoshiba K, Zalc B. 1993. The proximal region of the MBP gene promoter is sufficient to induce oligodendroglial-specific expression in transgenic mice. Eur J Neurosci 5: 624–632. 10.1111/j.1460-9568.1993.tb00528.x CASPubMedWeb of Science®Google Scholar Gow A, Friedrich VL Jr., Lazzarini RA. 1992. Myelin basic protein gene contains separate enhancers for oligodendrocyte and Schwann cell expression. J Cell Biol 119: 605–616. 10.1083/jcb.119.3.605 CASPubMedWeb of Science®Google Scholar Hogan B, Beddington R, Costantini F, Lacy E. 1994. Manipulating the mouse embryo: a laboratory manual. Plainview, NY: Cold Spring Harbor Laboratory Press, 497 p. Web of Science®Google Scholar Miura M, Tamura T, Aoyama A, Mikoshiba K. 1989. The promoter elements of the mouse myelin basic protein gene function efficiently in NG108-15 neuronal/glial cells. Gene 75: 31–38. 10.1016/0378-1119(89)90380-6 CASPubMedWeb of Science®Google Scholar O'Gorman S, Dagenais NA, Qian M, Marchuk Y. 1997. Protamine-Cre recombinase transgenes efficiently recombine target sequences in the male germ line of mice, but not in embryonic stem cells. Proc Natl Acad Sci USA 94: 14602–14607. 10.1073/pnas.94.26.14602 CASPubMedWeb of Science®Google Scholar Turnley AM, Morahan G, Okano H, Bernard O, Mikoshiba K, Allison J, Bartlett PF, Miller JF. 1991. Dysmyelination in transgenic mice resulting from expression of class I histocompatibility molecules in oligodendrocytes. Nature 353: 566–569. 10.1038/353566a0 CASPubMedWeb of Science®Google Scholar Yoshioka T, Feigenbaum L, Jay G. 1991. Transgenic mouse model for central nervous system demyelination. Mol Cell Biol 11: 5479–5486. 10.1128/MCB.11.11.5479 CASPubMedWeb of Science®Google Scholar Citing Literature Volume26, Issue2Special Issue:Tissue Specific Expression of Cre Recombinase in MiceFebruary 2000Pages 127-129 ReferencesRelatedInformation