NK cells engineered to express the chimeric receptor scFv(ch14.18)-zeta-specifically lyse GD2 expressing neuroectodermal tumors

Neuroblastoma (NB) and melanoma are neuroectodermal tumors characterized by poor prognosis. The T cell independent antigen ganglioside GD2 is highly expressed on most NB and on 30% of melanomas, which makes it an interesting target for immunotherapeutic approaches. NK cells are able to actively lyse tumors with downregulated MHC class I expression due to their MHC-independent target cell recognition. In order to provide for a specific recognition of GD2 expressing tumor cells, the human NK cell line NK-92 was genetically modified to express a chimeric receptor, consisting of a GD2-specific ch14.18scFv-fragment and the signal transducing zeta-chain of the CD3 complex (NK-92-scFv(ch14.18)-zeta). In order to test specificity and functionality of NK-92-scFv(ch14.18)-zeta, FACS analysis was performed. For this purpose, an anti-idiotypic-antibody (anti-Id-Ab 1A7) was used, which mimics the GD2 epitope and is directed against the binding domain of ch14.18. Furthermore, in vitro cytotoxicity assays with several GD2+ and GD2- NB and melanoma cell lines were performed. FACS analysis using α-Id-Ab 1A7 revealed high expression of the chimeric receptor on NK-92-scFv(ch14.18)-zeta, indicating specificity for GD2. Furthermore, genetically modified NK-92 specifically lysed GD2+ tumor cells at an E:T ratio of 12.5:1, ranging from 41% (M21 cells, GD2+ melanoma) to 43% (SK-N-AS, GD2+ human NB). In contrast to that, cytotoxicity was low against GD2- NB cell line SK-N-SH (13% specific cytotoxicity). Finally, cytotoxicity of the parental NK-92 cell line towards GD2 expressing tumor cells was diminished compared to NK-92-scFv(ch14.18)-zeta.