P15: Diagnosis of Constitutional Mismatch Repair-Deficiency

Chrystelle Colas1,2,3,4, Sahra Bodo1,2, Olivier Buhard1,2, Ada Collura1,2, Julie Tinat5, Noémie Lavoine6, Florence Coulet3, Marie-Pierre Buisine7,8, Denisa Ilencikova9, Clara Ruiz-Ponte10, Miriam Kinzel11, Sophie Grandjouan12, Hilde Brems13, Sophie Lejeune14, Qing Wang15, Olivier Caron16, Odile Cabaret17, Magali Svrcek1,2,3, Béatrice Parfait18, Alain Verloes1,19, Ulrich J. Knappe20, Florent Soubrier3, Isabelle Mortemousque21, Alexander Leis22, Thierry Frébourg5, Jean-François Fléjou1,2,3, Natacha Entz-Werle23, David Malka16, Odile Cohen-Haguenauer24, Yael Goldberg25, Anne-Marie Gerdes26, Faten Fedhila27, Michèle Mathieu-Dramard28, Richard Hamelin1,2, Badre Wafaa29, Marion Gauthier-Villars30, Franck Bourdeaut31,32, Eamonn Sheridan32, Hans Vasen33, Laurence Brugières34, Katharina Wimmer35, Martine Muleris1,2,Alex Duval1,2

1 -INSERM UMR_S 938 Centre de Recherche Saint-Antoine, Equipe Instabilité des Microsatellites et Cancer, équipe labellisée par la Ligue Nationle contre le Cancer, Paris, France. 2 -UPMC Univ Paris, Paris, France. 3 – AP-HP, Département de génétique, UF d’Oncogénétique et d’Angiogénétique, GH Pitié-Salpétrière, Paris, France. 4 – réseau PRED-IdF, Paris, France. 5 – Département de génétique, Hôpital universitaire, Rouen, France. 6 – Department of Children and Adolescents Oncology, Gustave Roussy Cancer Institute, Villejuif, France. 7 – Institut de Biochimie et Biologie moléculaire, Oncologie et Génétique Moléculaires, CHRU Lille, Lille, France. 8 – INSERM UMR837 et Université Lille, Lille, France. 9 – 2nd Pediatric Department, Children’s University Hospital, Comenius University, Bratislava, Slovakia. 10 – Fundación Pública Galega de Medicina Xenómica (FPGMX) SERGAS, Grupo de Medicina Xenómica, IDIS, Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERer), Santiago de Compostela, Spain. 11 – Praxis für Medizinische Genetik, Berlin, Germany. 12 – CHU Cochin, faculté René Descartes Paris-V, Paris, France. 13 – Department of Human Genetics, KU Leuven, Leuven, Belgium. 14 – CHRU Lille, Service de génétique clinique, Lille, France. 15 – Plateforme de Génétique constitutionnelle HCL-CLB, Laboratoire de recherche translationnelle, Centre Léon Bérard, Lyon, France. 16 Department of Medical Oncology, Gustave Roussy Cancer Institute, Villejuif, France. 17 – Service de Génétique, Département de Biologie et Pathologie Médicales, Institut Gustave Roussy, Villejuif,France. 18 – INSERM UMR745 Université Paris Descartes, Faculté des Sciences Pharmaceutiques et Biologiques, Paris, France. 19 – INSERM UMR 1141 PROTECT, Hôpital Robert Debré, Paris, France. 20 – Department of Neurosurgery, Johannes Wesling Klinikum, Minden, Germany. 21 – CHRU de Tours, Service de Génétique, Tours, France. 22 – French Medical Institute for Children, Kabul, Afghanistan. 23 – Pédiatrie Onco-Hématologie Pédiatrie CHRU Hautepierre UdS EA, Strasbourg, France. 24 – Service d’Oncologie Médicale, Hôpital Saint-Louis, Paris, France. 25 – Sharett Institute of Oncology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel. 26 – Department of Clinical Genetics, Copenhagen University Hospital Rigshospital, Copenhagen, Denmark. 27 – Service de médecine infantile, hôpital d’enfants de Tunis, Tunis, Tunisia. 28 – Unit of medical Genetics, Amiens University Hospital, Amiens, France. 29 – Department of Hepato-Gastro-Enterology, Ibn Rochd, Hospital University Center, Casablanca, Morocco. 30 – Service de Génétique, Institut Curie, Paris, France. 31 – Department of Pediatric Oncology and INSERM U830, Institut Curie, Paris, France. 32 – Department of Molecular Medicine, University of Leeds, Leeds, United Kingdom. 33 – Department of Gastroenterology and Hepatology, Leiden University Medical Centre, Leiden, The Netherlands. 34 – Department of Children and Adolescents Oncology, Gustave Roussy Cancer Institute, Villejuif, France. 35 – Division of Human Genetics, Medical University Innsbruck, Innsbruck, Austria on behalf of the European Consortium “Care for CMMRD”

Aim

Bi-allelic germline mutations in mismatch repair (MMR) genes cause constitutional MMR deficiency (CMMRD) characterized by early-onset colorectal cancers, lymphomas or leukemias, and brain tumours. There is no satisfactory method for diagnosis because screening for mutations in MMR genes is often non-informative. MMR-deficient cancer cells are resistant to genotoxic agents and have microsatellite instability (MSI). We investigated whether these features could be used to identify patients with CMMRD.

Method

We examined MSI by PCR analysis and tolerance to methylating or thiopurine agents  in lymphoblastoid cells (LCs) from 3 patients with CMMRD and 5 individuals with MMR-proficient LCs. Then we defined experimental parameters that allowed discrimination of a series of 14 patients with CMMRD from 52 controls. We then used the same parameters to assess 23 patients with clinical but not genetic features of CMMRD.

Results

Among 23 patients suspected of having CMMRD, 6 had MSI and tolerance to methylation (CMMRD highly probable), 15 had neither MSI nor tolerance to methylation (unlikely to have CMMRD), and 2 were considered doubtful.

Conclusion

We identified parameters, based on MSI and LC tolerance to methylation, that detected patients with CMMRD vs controls with 100% sensitivity and specificity. These features could be used in diagnosis of patients.

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