RESUMO
Hereditary defects in several genes have been shown to disturb the normal immune response to EBV and to give rise to severe EBV-induced lymphoproliferation in the recent years. Nevertheless, in many patients, the molecular basis of fatal EBV infection still remains unclear. The Fanconi anemia-associated protein 24 (FAAP24) plays a dual role in DNA repair. By association with FANCM as component of the FA core complex, it recruits the FA core complex to damaged DNA. Additionally, FAAP24 has been shown to evoke ATR-mediated checkpoint responses independently of the FA core complex. By whole exome sequencing, we identified a homozygous missense mutation in the FAAP24 gene (cC635T, pT212M) in two siblings of a consanguineous Turkish family who died from an EBV-associated lymphoproliferative disease after infection with a variant EBV strain, expressing a previously unknown EBNA2 allele.In order to analyze the functionality of the variant FAAP24 allele, we used herpes virus saimiri-transformed patient T cells to test endogenous cellular FAAP24 functions that are known to be important in DNA damage control. We saw an impaired FANCD2 monoubiquitination as well as delayed checkpoint responses, especially affecting CHK1 phosphorylation in patient samples in comparison to healthy controls. The phenotype of this FAAP24 mutation might have been further accelerated by an EBV strain that harbors an EBNA2 allele with enhanced activities compared to the prototype laboratory strain B95.8. This is the first report of an FAAP24 loss of function mutation found in human patients with EBV-associated lymphoproliferation.
Assuntos
Proteínas de Ligação a DNA/genética , Transtornos Linfoproliferativos/diagnóstico , Transtornos Linfoproliferativos/genética , Mutação , Irmãos , Substituição de Aminoácidos , Ciclo Celular , Códon , Consanguinidade , Dano ao DNA , Reparo do DNA , Proteínas de Ligação a DNA/metabolismo , Proteína do Grupo de Complementação D2 da Anemia de Fanconi/metabolismo , Proteínas de Grupos de Complementação da Anemia de Fanconi , Evolução Fatal , Feminino , Genótipo , Homozigoto , Humanos , Contagem de Linfócitos , Transtornos Linfoproliferativos/virologia , Masculino , Linhagem , Fenótipo , Receptores de Antígenos de Linfócitos T/metabolismo , Transdução de Sinais , Troca de Cromátide Irmã , Linfócitos T/imunologia , Linfócitos T/metabolismo , Ubiquitinação , Sequenciamento do ExomaAssuntos
Reparo do DNA , Mononucleose Infecciosa/genética , Proteína Rad52 de Recombinação e Reparo de DNA/genética , Imunodeficiência Combinada Severa/genética , Adolescente , Ciclo Celular/efeitos dos fármacos , Quebras de DNA de Cadeia Dupla , Fibroblastos/efeitos dos fármacos , Fibroblastos/imunologia , Fibroblastos/patologia , Herpesvirus Humano 4/patogenicidade , Herpesvirus Humano 4/fisiologia , Humanos , Mononucleose Infecciosa/imunologia , Mononucleose Infecciosa/patologia , Masculino , Mitomicina/farmacologia , Modelos Moleculares , Conformação Proteica em alfa-Hélice , Conformação Proteica em Folha beta , Proteína Rad52 de Recombinação e Reparo de DNA/química , Proteína Rad52 de Recombinação e Reparo de DNA/imunologia , Imunodeficiência Combinada Severa/imunologia , Imunodeficiência Combinada Severa/patologiaRESUMO
ETV6-RUNX1 is associated with the most common subtype of childhood leukemia. As few ETV6-RUNX1 carriers develop precursor B-cell acute lymphocytic leukemia (pB-ALL), the underlying genetic basis for development of full-blown leukemia remains to be identified, but the appearance of leukemia cases in time-space clusters keeps infection as a potential causal factor. Here, we present in vivo genetic evidence mechanistically connecting preleukemic ETV6-RUNX1 expression in hematopoetic stem cells/precursor cells (HSC/PC) and postnatal infections for human-like pB-ALL. In our model, ETV6-RUNX1 conferred a low risk of developing pB-ALL after exposure to common pathogens, corroborating the low incidence observed in humans. Murine preleukemic ETV6-RUNX1 pro/preB cells showed high Rag1/2 expression, known for human ETV6-RUNX1 pB-ALL. Murine and human ETV6-RUNX1 pB-ALL revealed recurrent genomic alterations, with a relevant proportion affecting genes of the lysine demethylase (KDM) family. KDM5C loss of function resulted in increased levels of H3K4me3, which coprecipitated with RAG2 in a human cell line model, laying the molecular basis for recombination activity. We conclude that alterations of KDM family members represent a disease-driving mechanism and an explanation for RAG off-target cleavage observed in humans. Our results explain the genetic basis for clonal evolution of an ETV6-RUNX1 preleukemic clone to pB-ALL after infection exposure and offer the possibility of novel therapeutic approaches. Cancer Res; 77(16); 4365-77. ©2017 AACR.
Assuntos
Subunidade alfa 2 de Fator de Ligação ao Core/metabolismo , Histona Desmetilases/metabolismo , Proteínas de Fusão Oncogênica/metabolismo , Leucemia-Linfoma Linfoblástico de Células Precursoras B/metabolismo , Leucemia-Linfoma Linfoblástico de Células Precursoras B/microbiologia , Animais , Subunidade alfa 2 de Fator de Ligação ao Core/biossíntese , Subunidade alfa 2 de Fator de Ligação ao Core/genética , Modelos Animais de Doenças , Células-Tronco Hematopoéticas , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos CBA , Camundongos Transgênicos , Proteínas de Fusão Oncogênica/biossíntese , Proteínas de Fusão Oncogênica/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras B/genéticaRESUMO
Histone deacetylase (HDAC) inhibitors such as suberoylanilide hydroxamic acid (SAHA) are not commonly used in clinical practice for treatment of B-cell lymphomas, although a subset of patients with refractory or relapsed B-cell lymphoma achieved partial or complete remissions. Therefore, the purpose of this study was to identify molecular features that predict the response of B-cell lymphomas to SAHA treatment. We designed an integrative approach combining drug efficacy testing with exome and captured target analysis (DETECT). In this study, we tested SAHA sensitivity in 26 B-cell lymphoma cell lines and determined SAHA-interacting proteins in SAHA resistant and sensitive cell lines employing a SAHA capture compound (CC) and mass spectrometry (CCMS). In addition, we performed exome mutation analysis. Candidate validation was done by expression analysis and knock-out experiments. An integrated network analysis revealed that the Src tyrosine kinase Gardner-Rasheed feline sarcoma viral (v-fgr) oncogene homolog (FGR) is associated with SAHA resistance. FGR was specifically captured by the SAHA-CC in resistant cells. In line with this observation, we found that FGR expression was significantly higher in SAHA resistant cell lines. As functional proof, CRISPR/Cas9 mediated FGR knock-out in resistant cells increased SAHA sensitivity. In silico analysis of B-cell lymphoma samples (n = 1200) showed a wide range of FGR expression indicating that FGR expression might help to stratify patients, which clinically benefit from SAHA therapy. In conclusion, our comprehensive analysis of SAHA-interacting proteins highlights FGR as a factor involved in SAHA resistance in B-cell lymphoma.