NKG2D CAR T‐cell therapy inhibits the growth of NKG2D ligand heterogeneous tumors

Abstract

Tumor heterogeneity presents a substantial barrier to increasing clinical responses mediated by targeted therapies. Broadening the immune response elicited by treatments that target a single antigen is necessary for the elimination of tumor variants that fail to express the targeted antigen. In this study, it is shown that adoptive transfer of T cells bearing a chimeric antigen receptor (CAR) inhibited the growth of target-expressing and –deficient tumor cells within ovarian and lymphoma tumors. Mice bearing the ID8 ovarian or RMA lymphoma tumors were treated with T cells transduced with a NKG2D-based CAR (chNKG2D). NKG2D CAR T cell therapy protected mice from heterogeneous RMA tumors. Moreover, adoptive transfer of chNKG2D T cells mediated tumor protection against highly heterogeneous ovarian tumors in which 50%, 20%, or only 7% of tumor cells expressed significant amounts of NKG2D ligands. CAR T cells did not mediate an in vivo response against tumor cells that did not express sufficient amounts of NKG2D ligands, and the number of ligand-expressing tumor cells correlated with therapeutic efficacy. In addition, tumor-free surviving mice were protected against a tumor re-challenge with NKG2D ligand-negative ovarian tumor cells. These data indicate that NKG2D CAR T cell treatment can be an effective therapy against heterogeneous tumors and induce tumor-specific immunity against ligand-deficient tumor cells.

T Cells Engineered With Chimeric Antigen Receptors Targeting NKG2D Ligands Display Lethal Toxicity in Mice

“…While NKG2D is an activating receptor on natural killer (NK) cells, it functions primarily as a costimulatory receptor on activated CD8+ T cells [5][6][7][12][13][14][15] . In both murine and human T cells, signaling through the NKG2D receptor is mediated through an adaptor protein, DAP10 8,13 .…”

“…One method of generating CARs fuses native proteins, which naturally ligate proteins on the surface of tumor cells, with the intracellular signaling domains required to induce T cell activation. Ligands for the natural killer group 2 member D (NKG2D) receptor are numerous and are frequently upregulated on many cancer types [5][6][7] .…”

Tumor Regression and Delayed Onset Toxicity Following B7-H4 CAR T Cell Therapy

“…The differences in kinetics seen in our study may have occurred for several reasons including differences in CAR T-cell dose, preconditioning regimes, distribution of target antigen in normal tissue, and murine strain variability. 51 Additionally, several groups have observed safe therapeutic targeting of fibroblast activating protein in murine models, 52,53 suggesting that differences in the therapy could allow for safe targeting by CAR T cells. Future studies with regulatable B7-H4 CARs could evaluate T-cell trafficking, kinetics, and impact on tissue utilizing withdrawal of B7-H4 CAR treatment prior to induction of lethal toxicity.…”

“…Fully human anti-B7-H4 scFv sequences 14,53 were amplified via polymerase chain reaction from plasmids containing each soluble scFv sequence using the following primers:…”

Immunotherapy for Ovarian Cancer

“…CAR T cells express tumor-antigen specific antibody fragments on their surface, fused to intracellular activation proteins ( e.g., CD3ζ, 4-1BB, OX40) and recognize antigen independent of MHC. A preclinical study showed NKG2D-specific CAR T cells provide protection and establish memory against distinct OC tumors where only 7% cells express NKG2D [106] . Despite inducing complete remissions in leukemia patients, the efficacy of CAR T cells in solid tumors has been more limited due to inefficient tumor homing.…”