title: Ectopic retroviral expression of LMO2, but not IL2Rgamma, blocks human T-cell development from CD34+ cells: implications for leukemogenesis in gene therapy.
abstract: The occurrence of leukemia in a gene therapy trial for SCID-X1 has highlighted insertional mutagenesis as an adverse effect. Although retroviral integration near the T-cell acute lymphoblastic leukemia (T-ALL) oncogene LIM-only protein 2 (LMO2) appears to be a common event, it is unclear why LMO2 was preferentially targeted. We show that of classical T-ALL oncogenes, LMO2 is most highly transcribed in CD34+ progenitor cells. Upon stimulation with growth factors typically used in gene therapy protocols transcription of LMO2, LYL1, TAL1 and TAN1 is most prominent. Therefore, these oncogenes may be susceptible to viral integration. The interleukin-2 receptor gamma chain (IL2Rgamma), which is mutated in SCID-X1, has been proposed as a cooperating oncogene to LMO2. However, we found that overexpressing IL2Rgamma had no effect on T-cell development. In contrast, retroviral overexpression of LMO2 in CD34+ cells caused severe abnormalities in T-cell development, but B-cell and myeloid development remained unaffected. Our data help explain why LMO2 was preferentially targeted over many of the other known T-ALL oncogenes. Furthermore, during T-cell development retrovirus-mediated expression of IL2Rgamma may not be directly oncogenic. Instead, restoration of normal IL7-receptor signaling may allow progression of T-cell development to stages where ectopic LMO2 expression causes aberrant thymocyte growth.
authors.affiliation: Department of Immunology, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: K
authors.initials: K
authors.lastname: Pike-Overzet
authors.forename: D
authors.initials: D
authors.lastname: de Ridder
authors.forename: F
authors.initials: F
authors.lastname: Weerkamp
authors.forename: M R M
authors.initials: MR
authors.lastname: Baert
authors.forename: M M A
authors.initials: MM
authors.lastname: Verstegen
authors.forename: M H
authors.initials: MH
authors.lastname: Brugman
authors.forename: S J
authors.initials: SJ
authors.lastname: Howe
authors.forename: M J T
authors.initials: MJ
authors.lastname: Reinders
authors.forename: A J
authors.initials: AJ
authors.lastname: Thrasher
authors.forename: G
authors.initials: G
authors.lastname: Wagemaker
authors.forename: J J M
authors.initials: JJ
authors.lastname: van Dongen
authors.forename: F J T
authors.initials: FJ
authors.lastname: Staal
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D015703:Antigens, CD / Q000276:immunology; D018952:Antigens, CD34 / Q000276:immunology*; D004268:DNA-Binding Proteins / Q000235:genetics*; D015316:Genetic Therapy / Q000379:methods*; D006133:Growth Substances / Q000494:pharmacology; D006801:Humans; D060588:LIM Domain Proteins; D007938:Leukemia / Q000235:genetics* / Q000628:therapy*; D015459:Leukemia-Lymphoma, Adult T-Cell / Q000235:genetics* / Q000276:immunology / Q000628:therapy; D008667:Metalloproteins / Q000235:genetics*; D016254:Mutagenesis, Insertional; D011518:Proto-Oncogene Proteins; D015375:Receptors, Interleukin-2 / Q000235:genetics*; D012190:Retroviridae; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D015703:Antigens, CD; D018952:Antigens, CD34; D004268:DNA-Binding Proteins; D006133:Growth Substances; D060588:LIM Domain Proteins; C085117:LMO2 protein, human; D008667:Metalloproteins; D011518:Proto-Oncogene Proteins; D015375:Receptors, Interleukin-2