Potential Limitations of the NSG Humanized Mouse as a Model System to Optimize Engineered Human T cell Therapy for Cancer

Abstract

The genetic modification of peripheral blood lymphocytes using retroviral vectors to redirect T cells against tumor cells has been recently used as a means to generate large numbers of antigen-specific T cells for adoptive cell therapy protocols. However, commonly used retroviral vector-based genetic modification requires T cells to be driven into cell division; this potent mitogenic stimulus is associated with the development of an effector phenotype that may adversely impact upon the long-term engraftment potential and subsequent antitumor effects of T cells. To investigate whether the cytokines used during culture impact upon the engraftment potential of gene-modified T cells, a humanized model employing T cells engrafted with a MART-1-specific T cell receptor adoptively transferred into NOD/Shi-scid IL-2rγ(-/-) (NSG) immune-deficient mice bearing established melanoma tumors was used to compare the effects of the common γ chain cytokines IL-2, IL-7, and IL-15 upon gene-modified T cell activity. MART-1-specific T cells cultured in IL-7 and IL-15 demonstrated greater relative in vitro proliferation and viability of T cells compared with the extensively used IL-2. Moreover, the IL-15 culture prolonged the survival of animals bearing melanoma tumors after adoptive transfer. However, the combination of IL-7 and IL-15 produced T cells with improved engraftment potential compared with IL-15 alone; however, a high rate of xenogeneic graft-versus-host disease prevented the identification of a clear improvement in antitumor effect of these T cells. These results clearly demonstrate modulation of gene-modified T cell engraftment in the NSG mouse, which supports the future testing of the combination of IL-7 and IL-15 in adoptive cell therapy protocols; however, this improved engraftment is also associated with the long-term maintenance of xenoreactive T cells, which limits the ultimate usefulness of the NSG mouse model in this situation.

Exploiting Cytokines in Adoptive T-Cell Therapy of Cancer

“…IL-15 also supports the proliferation of human memory T cells and when compared with IL-2, it was found to be equally effective in promoting tumor-reactive T-cell expansion and cytotoxic abilities, and superior in preserving cell viability [23,29,30]. IL-21 is a pleiotropic cytokine mainly produced by CD4 + T cells (follicular helper cells and Th-17 cells) and natural killer T cells (NKT), as well as to a minor extent by CD8 + T cells (recently reviewed in [31]).…”

“…IL-7 and IL-15 did synergistically support the expansion of T CM cells [38], in some instances instructed the generation of T SCM [6,13] and resulted in superior engraftment and effector function in vivo [30]. Most recently the combination of IL-7 and IL-15 has been used in place of IL-2 during in vitro expansion protocols in a Phase I/IIa clinical trial [39].…”

Adoptive T-Cell Therapy for Cancer in the United Kingdom: A Review of Activity for the British Society of Gene and Cell Therapy Annual Meeting 2015

“…However, the Gilham/Hawkins group at the University of Manchester is actively investigating CAR T-cell-mediated toxicity and, in particular, attempting to understand chronic toxicity associated with certain CD19-specific second-generation CARs in syngeneic lymphoma model systems 62 while also working upon improving the in vitro culture conditions used to generate engineered T-cells to improve in vivo functionality. 63 Additionally, the recent arrival of Prof. Mark Exley to Manchester is stimulating work to investigate the efficacy and potency of CARs in iNKT cells. 6 Within the London area, there is a considerable level of preclinical activity in the TCR/CAR field.…”

CAR T-cell Therapy: Toxicity and The Relevance of Preclinical Models

“…More recently, the availability of the highly immune-compromised NOG/NSG mouse (NOD/SCID IL-2Rγ -/-) has allowed efficient human T-cell engraftment. However, engrafted T cells can drive a xeno-graft versus host disease (xGVHD) which occurs around 50 days after adoptive T-cell transfer at doses above 10 9 cells/kg [22]. The occurrence of xGVHD is associated with transduced cell persistence and this is affected by the cytokine conditions used to culture the cells prior to injection into mice.…”

“…The occurrence of xGVHD is associated with transduced cell persistence and this is affected by the cytokine conditions used to culture the cells prior to injection into mice. Consequently, this limits the ability to investigate the long-term effects of CAR T cells in this model [22][23][24].…”