gms | German Medical Science

Objective: Natural killer cells (NK) are able to recognize and kill tumor cells with loss of HLA class I expression and concomitant decrease of HLA-E. However, most gliomas still express HLA class I, and NK cell reactivity against HLA I-negative solid tumors is blocked by inhibitory non classical HLA and lack of activating ligands on the surface of tumor cells. Furthermore, immunosuppressive factors released by glioma cells and the tumor stroma impair cytotoxic effector functions of NK cells. To overcome these hurdles we sought to generate and evaluate primary NK cells genetically modified with a chimeric antigen receptor (CAR) for treatment of glioma cells with surface expression of the neo-epitope epidermal growth factor receptor variant III (EGFRvIII).

Methods: Using recombinant DNA technology we generated a lentiviral vector encoding the CAR consisting of the anti-EGFRvIII single chain antibody scFv(MR1.1) and DNAX activation protein of 12kDa (DAP12). This vector and a control vector only encoding DAP12 were used to transduce primary human NK cells, respectively. Expression and effector function of the scFv(MR1.1)-DAP12 CAR was tested in flow cytometry, Western blot, INF-γ ELISA and chromium release assay using EGFRvIII-positive glioma target cells.

Results: Primary NK cells were efficiently transduced to 65% with the chimeric antigen receptor scFv(MR1.1)-DAP12. CAR-modified NK cells showed a selective degranulation, INF-γ release and cytotoxicity when confronted with EGFRvIII-positive glioma cells whereas no NK cell reactivity was induced in DAP12-transduced NK cells or when using EGFRvIII-negative target cells.

Conclusion: Our results suggest that the DAP12-based CAR might be suitable for NK-cell based immunotherapy of gliomas. Further studies in xenograft models and using primary NK cells are warranted to further pursue NK cell-based immunotherapy of gliomas.