Retroviral Insertional Mutagenesis Can Contribute to Immortalization of Mature T Lymphocytes

Abstract

Several cases of T-cell leukemia caused by gammaretroviral insertional mutagenesis in children treated for x-linked severe combined immunodeficiency (SCID) by transplantation of autologous gene-modified stem cells were reported. In a comparative analysis, we recently showed that mature T cells, on the contrary, are highly resistant to transformation by gammaretroviral gene transfer. In the present study, we observed immortalization of a single T-cell clone in vitro after gammaretroviral transduction of the T-cell protooncogene LMO2. This clone was CD4/CD8 double-negative, but expressed a single rearranged T-cell receptor. The clone was able to overgrow nonmanipulated competitor T-cell populations in vitro, but no tumor formation was observed after transplantation into Rag-1 deficient recipients. The retroviral integration site (RIS) was found to be near the IL2RA and IL15RA genes. As a consequence, both receptors were constitutively upregulated on the RNA and protein level and the immortalized cell clone was highly IL-2 dependent. Ectopic expression of both, the IL2RA chain and LMO2, induced long-term growth in cultured primary T cells. This study demonstrates that insertional mutagenesis can contribute to immortalization of mature T cells, although this is a rare event. Furthermore, the results show that signaling of the IL-2 receptor and the protooncogene LMO2 can act synergistically in maligniant transformation of mature T lymphocytes.

Identification of Chimeric Antigen Receptors That Mediate Constitutive or Inducible Proliferation of T Cells

“…As a potentially more sensitive assay to detect cellular transformation, NSG (NOD-SCID-γc −/− ) mice were used, as previous studies have shown that adoptively transferred transformed and malignant T cells can form tumors in immunodeficient mice (37). Groups of mice were infused with fully activated T cells or with continuous CAR T cells and proliferation assessed by quantification of T cells in the mice and effector function assessed by the induction of xenogeneic graft versus host disease in the mice.…”

OX40 costimulation by a chimeric antigen receptor abrogates CD28 and IL-2 induced IL-10 secretion by redirected CD4+T cells

“…Retroviral integration potentially can induce T cell acute lymphoblastic leukemia due to LMO2 overexpression in patients with X-linked severe combined immunodeficiency who received hematopoietic stem cells engineered to constitutively express the common γ-chain receptor 33 . In contrast to retroviral modification of hematopoietic stem cells, engineering mature T cells in experimental models did not or very rarely result in malignant transformation 34 , 35 …”

Adoptive Immunotherapy for Cancer or Viruses

“…Unlike HSCs, T lymphocytes are less susceptible to transformation (101). Although insertional mutagenesis can contribute to immortalization of retrovirally transduced mature T cells in vitro, it is a rare event, and occurs in the setting of a synergistic effect between activation of a proto-oncogene, such as LMO2, and robust signaling through T cell homeostatic cytokines, such as IL-2 or IL-15 (102, 103). Whether a T cell stimulating signal generated by a transduced TCR or CAR can synergize with activation of a proto-oncogene caused by retroviral insertional mutagenesis to mediate transformation of the transduced T cells remains to be elucidated.…”