Targeting of GD2-positive tumor cells by human T lymphocytes engineered to express chimeric T-cell receptor genes

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Abstract
Genetic engineering of human T lymphocytes to express tumor antigen‐specific chimeric immune receptors is an attractive means for providing large numbers of effector cells for adoptive immunotherapy while bypassing major mechanisms of tumor escape from immune recognition. We have applied this strategy to the targeting of a GD2‐positive tumor, neuroblastoma, which is the commonest extracranial solid tumor of childhood. Chimeric immune receptors were generated by joining an extracellular antigen‐binding domain derived from either of the 2 ganglioside GD2‐specific antibodies sc7A4 and sc14.G2a to a cytoplasmic signaling domain. The variable domains of hybridoma antibody 14.G2a were cloned and selected using a phage display approach. Upon coincubation with GD2‐expressing tumor cell targets, human T lymphocytes transduced with recombinant retroviruses encoding chimeric receptors based on sc14.G2a, but not sc7A4, secreted significant levels of cytokines in a pattern comparable to the cytokine response obtained by engagement of the CD3 receptor. T cells transduced with the sc14.G2a‐based chimeric T‐cell receptors also displayed specific lysis of GD2‐positive neuroblastoma cells, which was blocked in the presence of monoclonal antibody 14.G2a. In the absence of nonspecific stimulation of transduced cells, their functionality declined over time and antigenic stimulation of the chimeric receptor alone did not induce commitment to proliferation. These results support the feasibility of redirecting human T lymphocytes to a tumor‐associated ganglioside epitope but emphasize that successful chimeric receptor‐mediated adoptive immunotherapy will require additional strategies that overcome functional inactivation of gene‐modified primary T lymphocytes.