High-sensitivity microsatellite instability assessment for the detection of mismatch repair defects in normal tissue of biallelic germline mismatch repair mutation carriers

Fátima Marín1, Maribel González-Acosta1, Benjamin Puliafito1, Núria Bonifaci1, Julia Canet1, Anna Fernández1, Matilde Navarro1, Héctor Salvador2, Francesc Balaguer3, Silvia Iglesias1, Àngela Velasco4, Èlia Grau1, Victor Moreno5,6, Luis Ignacio Gonzalez-Granado7, Pilar Guerra-García8, Rosa Ayala9, Benoît Florkin10, Christian P. Kratz11, Tim Ripperger12, Thorsten Rosenbaum13, Danuta Januszkiewicz-Lewandowska14, Amedeo A. Azizi15, Iman Ragab16, Michaela Nathrath17,18, Hans-Jürgen Pander19, Stephan Lobitz20, Manon Suerink21, Karin Dahan22, Thomas Imschweiler23, Ugur Demirsoy24, Joan Brunet1,4, Conxi Lázaro1, Daniel Rueda25, Katharina Wimmer26, Marta Pineda1, Gabriel Capellá1

1Hereditary Cancer Program, Catalan Institute of Oncology, ICO-IDIBELL, Hospitalet de Llobregat, Barcelona, Spain. 2Pediatric Oncology Unit, Hospital Sant Joan de Déu, Esplugues, Barcelona, Spain. 3Department of Gastroenterology, Hospital Clínic, Centro de Investigación Biomédica en Red en Enfermedades Hepáticas y Digestivas (CIBERehd),IDIBAPS, Barcelona, Spain. 4Hereditary Cancer Program, Catalan Institute of Oncology, ICO-IDIBGI, Girona, Spain. 5Cancer Prevention and Control Program, Catalan Institute of Oncology (ICO), IDIBELL, CIBERESP, Barcelona, Spain. 6Department of Clinical Sciences, Faculty of Medicine, University of Barcelona, Barcelona, Spain. 7Immunodeficiencies Unit, Department of Pediatrics, Doce de Octubre University Hospital, i+12 Research Institute; Complutense University of Madrid, Madrid, Spain. 8Hematology and Oncology Unit, Department of Pediatrics, Doce de Octubre University Hospital, Madrid, Spain. 9Department of Hematology, Doce de Octubre University Hospital, i+12 Research Institute, Madrid, Spain. 10University Department of Pediatrics, CHR Citadelle, Liège, Belgium. 11Department of Pediatric Hematology and Oncology, Hannover Medical School, Hannover, Germany. 12Department of Human Genetics, Hannover Medical School, Hannover, Germany. 13Department of Pediatrics, Sana Kliniken Duisburg, Duisburg, Germany. 14Department of Pediatric Oncology, Hematology and Transplantation, Poznań University of Medical Sciences, Poznań, Poland. 15Department of Pediatrics and Adolescent Medicine, Medical University of Vienna, Vienna, Austria. 16Pediatrics Department, Hematology-Oncology Unit, Faculty of Medicine, Ain Shams University, Cairo, Egypt. 17Pediatric Hematology and Oncology, Klinikum Kassel, Kassel, Germany. 18Pediatric Oncology Center, Department of Pediatrics, Technische Universität München, Munich, Germany. 19Institut für Klinische Genetik, Olgahospital, Stuttgart, Germany. 200Kliniken der Stadt Köln gGmbH, Children’s Hospital Amsterdamer Strasse, Department of Pediatric Oncology/Pediatric Hematology, Köln, Germany. 21Department of Clinical Genetics, Leiden University Medical Center, Leiden, Netherlands. 22Centre de génétique humaine, Institut de pathologie et génétique (IPG, Gosselies, Belgium. 23Pediatric Oncology, Helios-Klinikum, Krefeld, Germany. 24Department of Pediatric Oncology, Kocaeli University, Kocaeli, Turkey. 25Hereditary Cancer Laboratory, Doce de Octubre University Hospital, i+12 Research Institute, Madrid, Spain. 26Division of Human Genetics, Medical University Innsbruck, Innsbruck, Austria

Abstract

Introduction: Lynch syndrome (LS) and Constitutional Mismatch Repair Deficiency (CMMRD) are hereditary cancer syndromes associated with mismatch repair (MMR) deficiency. Tumors show microsatellite instability (MSI), also reported at low levels in non-neoplastic tissues. Our aim was to evaluate the performance of high-sensitivity MSI (hs-MSI) assessment for the identification of LS and CMMRD in non-neoplastic tissues.

Methods: Blood DNA samples from 131 individuals were grouped into three cohorts: baseline (22 controls), training (11 CMMRD, 48 LS, and 15 controls) and validation (18 CMMRD and 18 controls). Custom NGS panel and bioinformatics pipeline were used to detect insertions and deletions in microsatellite markers. An hs-MSI score was calculated representing the percentage of unstable markers.

Results: The hs-MSI score was significantly higher in CMMRD blood samples when compared to controls in the training cohort (p<0.001). This finding was confirmed in the validation set, reaching 100% specificity and sensitivity. Higher hs-MSI scores were detected in biallelic MSH2 carriers (n=5) compared to MSH6 carriers (n=15). The hs-MSI analysis did not detect a difference between LS and control blood samples (p=0.564).

Conclusions: The hs-MSI approach is a valuable tool for CMMRD diagnosis, especially in suspected patients harbouring MMR VUS or non-detected biallelic germline mutations.

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