OR10
Dual targeting of PD-L1 and ErbB2 by CAR-NK cells enables specific elimination of solid tumor cells and overcomes immune escape via antigen loss
J Eitler(1,2,3) I Ben-Horin(4,5) K Freudenberg(1,2) P Ortiz-Montero(1,2) L R Loureiro(7) W Rackwitz(1,2) S R Künzel(1,2) A Feldmann(7) M Bachmann(7,8,9) W S Wels(4,5,6) T Tonn(1,2,3)
1:Experimental Transfusion Medicine, Faculty of Medicine Carl Gustav Carus, Dresden University of Technology, Dresden, Germany; 2:Institute for Transfusion Medicine Dresden, German Red Cross Blood Donation Service North-East, Dresden, Germany; 3:German Cancer Consortium (DKTK), Partner Site Dresden, Dresden, Germany; 4:Georg-Speyer-Haus, Institute for Tumor Biology and Experimental Therapy, Frankfurt am Main, Germany; 5:Frankfurt Cancer Institute, Goethe University, Frankfurt am Main, Germany; 6:German Cancer Consortium (DKTK), Partner Site Frankfurt/Mainz, Frankfurt am Main, Germany; 7:Department of Radioimmunology, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany; 8:National Center for Tumor Diseases (NCT), University Hospital Carl Gustav Carus, TU Dresden, Dresden, Germany; 9:Tumor Immunology, University Cancer Center (UCC), University Hospital Carl Gustav Carus, TU Dresden, Dresden, Germany
Retargeting natural killer (NK) cells with chimeric antigen receptors (CARs) can be a powerful approach to overcome NK cell resistance of tumor cells. However, for some tumors, targeting a single tumor-associated antigen may be insufficient to trigger effective NK cell activation or may lead to selection of antigen-loss variants and tumor immune escape. To overcome this hurdle, here we generated CAR-NK cells carrying two CARs targeting the tumor-associated antigens PD-L1 and ErbB2 (HER2), respectively. NK-92 cells were transduced with lentiviral CAR constructs, and their cytotoxicity against cancer cell lines of various solid tumor origins was compared to that of parental NK-92 and corresponding single target CAR variants. Dual targeting significantly increased in vitro cytotoxicity against PD-L1 and ErbB2 double-positive tumor cell lines including breast, ovarian, pancreatic, lung and gastric cancer cells compared to single-target CAR variants. These results were also confirmed in 3D spheroid tumor models and in vivo xenografts. No off-target cytotoxicity was observed. At the molecular level, this enhanced cell killing can be explained by the synergistic activation of PLCγ and MAPK pathways. Incubation of cancer cells with IFN-γ further enhanced killing efficacy by upregulating PD-L1 expression. Furthermore, blocking experiments revealed that dual PD-L1/ErbB2-CAR NK-92 cells can overcome immune escape based on the loss or inaccessibility of a single target antigen. In conclusion, we have shown that dual targeting of PD-L1 and ErbB2 enhances the efficacy of CAR-NK cells against otherwise difficult to treat tumors and counteracts potential resistance and immune escape mechanisms of cancer cells.