Limiting Thymic Precursor Supply Increases the Risk of Lymphoid Malignancy in Murine X-Linked Severe Combined Immunodeficiency

Samantha L. Ginn, Claus V. Hallwirth, Sophia H.Y. Liao, Erdahl T. Teber, Jonathan W. Arthur, Jianmin Wu, Hong Ching Lee, Szun S. Tay, Min Hu, Roger R. Reddel, Matthew P. McCormack, Adrian J. Thrasher, Marina Cavazzana, Stephen I. Alexander, Ian E. Alexander

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Abstract

In early gene therapy trials for SCID-X1, using γ-retroviral vectors, T cell leukemias developed in a subset of patients secondary to insertional proto-oncogene activation. In contrast, we have reported development of T cell leukemias in SCID-X1 mice following lentivirus-mediated gene therapy independent of insertional mutagenesis. A distinguishing feature in our study was that only a proportion of transplanted γc-deficient progenitors were transduced and therefore competent for reconstitution. We hypothesized that reconstitution of SCID-X1 mice with limiting numbers of hematopoietic progenitors might be a risk factor for lymphoid malignancy. To test this hypothesis, in the absence of transduction, SCID-X1 mice were reconstituted with serially fewer wild-type hematopoietic progenitors. A robust inverse correlation between hematopoietic progenitor cell dose and T-lymphoid malignancy was observed, with earlier disease onset at lower cell doses. Malignancies were of donor origin and carried activating Notch1 mutations. These findings align with emerging evidence that thymocyte self-renewal induced by progenitor deprivation carries an oncogenic risk that is modulated by intra-thymic competition from differentiation-committed cells. Although insertional proto-oncogene activation is required for the development of malignancy in humans, failure of γc-deficient thymocytes to effectively compete with this at-risk cell population may have also contributed to oncogenesis observed in early SCID-X1 trials.

Original languageEnglish
Pages (from-to)1-14
Number of pages14
JournalMolecular Therapy - Nucleic Acids
Volume6
DOIs
Publication statusPublished - 17 Mar 2017

Keywords

  • gene therapy
  • lymphomagenesis
  • primary immune deficiency
  • SCID-X1
  • self-renewal
  • thymus

Cite this

Ginn, S. L., Hallwirth, C. V., Liao, S. H. Y., Teber, E. T., Arthur, J. W., Wu, J., Lee, H. C., Tay, S. S., Hu, M., Reddel, R. R., McCormack, M. P., Thrasher, A. J., Cavazzana, M., Alexander, S. I., & Alexander, I. E. (2017). Limiting Thymic Precursor Supply Increases the Risk of Lymphoid Malignancy in Murine X-Linked Severe Combined Immunodeficiency. Molecular Therapy - Nucleic Acids, 6, 1-14. https://doi.org/10.1016/j.omtn.2016.11.011, https://doi.org/10.1016/j.omtn.2016.11.011