Radhia M’Kacher1,2, Corina Cuceu1, Bruno Colicchio3, Steffen Junker4, François Plassa5, Justyna Mika6, Monika Frenzel1, Mustafa A. L. Jawhari1, William M. Hempel1, Grainne O’Brien7, Luc Morat1, Theodore Girinsky8, Alain Dieterlen3, Joanna Polanska6, Christophe Badie7, Eric Jeandidier9, Patrice Carde10
1 Radiobiology and Oncology Laboratory, CEA, iRCM, 92265 Fontenay aux Roses, France, 2 Cell Environnent DNA damages R&D Oncology section, Paris, France, 3 IRIMAS, Institut de recherche en informatique, mathématiques, automatique et signal, Université de Haute-Alsace, Mulhouse, France, 4 Institute of Biomedicine, University of Aarhus, Denmark, 5 Laboratory of Biochemistry B, Saint Louis Hospital, Paris, France, 6 Faculty of Automatic Control, Electronics and Computer Science, Silesian University of Techology, Gliwice, Poland, 7 Biological Effects Department, Centre for Radiation, Chemical and Environmental Hazards, Public Health England, Didcot OX11 ORQ, UK, 8 Department of Radiation Oncology, Gustave Roussy Cancer Campus, 94805 Villejuif, France, 9 Department of genetic, Groupe hospitalier de la région de Mulhouse Sud-Alsace, Mulhouse, France, 10 Department of Medicine, Gustave Roussy Cancer Campus, 94805 Villejuif, France
Background: Mechanisms underlying genomic instability as well as primary transforming events of Hodgkin lymphoma (HL) are still obscure. Here, we have investigated the putative contributions of microsatellite and chromosomal instability, respectively, to pathogenesis of HL.
Materials and Methods: We have investigated seven HL cell lines (five Nodular Sclerosis (NS): L428, HDLM2, L540, L591 and SUP-HD, two Mixed Cellularity (MC): L1236 and KMH2) and peripheral blood lymphocytes from 123 HL patients (100 SN-HL and 23 MC-HL). Microsatellite instability (MSI) was assessed by PCR. Chromosomal instability and telomere dysfunction were investigated by FISH. DNA repair mechanisms and radiation sensitivity were studied by transcriptome and molecular approaches.
Results: In the cell lines, we observed high MSI in L428 (4/5), KMH2 (3/5), and HDLM2 (3/5), low MSI in L540, L591, and SUP-HD1, and none in L1236. NS-HL cell lines showed telomere shortening, associated with alterations of nuclear shape. Small cells were characterized by telomere loss and deletion, resulting in chromosome fusion, large nucleoplasmic bridges, and breakage/fusion/bridge (B/F/B) cycles, and thus to chromosomal instability. The MC-HL cell lines showed substantial heterogeneity of telomere length. Intra-chromosomal double strand breaks induced dicentric chromosome formation, high levels of micronucleus formation, and small nucleoplasmic bridges. B/F/B cycles induced complex chromosomal rearrangements. Transcriptome analysis confirmed the differences in the DNA repair pathways between the NS and MC cell lines. Finally, a NS-HL cell line exhibited high radiation sensitivity compared to a MC-HL cell line. In accordance with our findings on HL cell lines, we have detected telomere dysfunction also in circulating lymphocytes from NS-HL patients as well as high telomere heterogeneity in MC-HL patients.
Conclusion: In NS-HL mononuclear cells, loss of telomere integrity may present the first step in the ongoing process of chromosomal instability. Perhaps NS-HL is associated with genetic defects in telomere replication and extension. On the basis of our data, MSI was identified as an additional mechanism for genomic instability in HL. MSI could be exploited for developing novel therapies and personalized treatment. MSI-cancers may constitute excellent candidates for immune checkpoint inhibitors.