Cisplatin Sensitivity in Diffuse Large B-cell Lymphoma and the Influence of Mutations in DNA Repair Genes
Author
Pedersen, Ann-Katrine Hyttel Rom
Term
4. term
Publication year
2019
Submitted on
2019-05-31
Pages
65
Abstract
Diffust storcellet B-celle lymfom (DLBCL) er den hyppigste form for non-Hodgkin lymfom, og en betydelig andel af patienterne får tilbagefald, hvor platinbaseret kemoterapi som cisplatin ofte anvendes. Behandlingsresistens er et centralt problem, og DNA-reparationsveje som mismatch repair (MMR) og nucleotide excision repair (NER) er tæt knyttet til cisplatins virkning. Dette speciale undersøgte, om ændringer i DNA-reparation kan forklare forskelle i cisplatinsensitivitet. Mutationer i DNA-reparationsgener blev kortlagt i 14 DLBCL-cellelinjer og i to kliniske kohorter (1.001 de novo DLBCL-patienter samt en lokal kohorte med 28 relaps- og 44 de novo-patienter) ved hjælp af et systematisk vurderingsværktøj. In vitro blev MSH2 målrettet med 17-(Allylamino)-17-demethoxygeldanamycin (17AAG) for at vurdere betydningen af MMR for cisplatinrespons, og DNA-brud blev kvantificeret med Comet Assay. Cellelinjerne blev inddelt i cisplatin-sensitive og -resistente baseret på doserespons. Mutationer i DNA-reparationsgener forekom overvejende i de cisplatin-sensitive cellelinjer og involverede MMR, NER og homolog rekombination. Hæmning af MSH2 med 17AAG nedsatte cisplatinsensitiviteten og reducerede mængden af frie DNA-fragmenter, hvilket peger på, at MSH2-medieret MMR kan bidrage til cisplatinresistens. I de kliniske data sås mutationer i XPF, EXO1 og MSH2, herunder en mindre ophobning i MSH2’s MutS_I-domæne. Samlet peger resultaterne på MMR som en vigtig mediator af cisplatinresistens i DLBCL, men sammenhængen mellem påvirket MSH2 og klinisk resistens bør bekræftes i større relaps-kohorter.
Diffuse large B-cell lymphoma (DLBCL) is the most common non-Hodgkin lymphoma, and a substantial fraction of patients relapse, where platinum-based chemotherapy such as cisplatin is frequently used. Treatment resistance remains a major challenge, and DNA repair pathways including mismatch repair (MMR) and nucleotide excision repair (NER) are closely linked to cisplatin’s action. This thesis investigated whether alterations in DNA repair help explain differences in cisplatin sensitivity. Mutations in DNA repair genes were profiled in 14 DLBCL cell lines and in two clinical cohorts (1,001 de novo DLBCL patients and a local cohort with 28 relapsed and 44 de novo patients) using a systematic assessment approach. In vitro, MSH2 was targeted with 17-(Allylamino)-17-demethoxygeldanamycin (17AAG) to test the role of MMR in cisplatin response, and DNA breaks were quantified with the Comet Assay. Cell lines were classified as cisplatin-sensitive or -resistant based on dose–response. Mutations in DNA repair genes were enriched in cisplatin-sensitive lines and involved MMR, NER, and homologous recombination. Inhibiting MSH2 with 17AAG decreased cisplatin sensitivity and reduced free DNA fragments, implicating MSH2-mediated MMR in cisplatin resistance. In the clinical data, mutations were observed in XPF, EXO1, and MSH2, with a slight accumulation in the MSH2 MutS_I domain. Overall, the findings support MMR as an important mediator of cisplatin resistance in DLBCL, but the link between impaired MSH2 and clinical resistance should be validated in larger cohorts of relapsed patients.
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