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Generation of Potent T-cell Immunotherapy for Cancer Using DAP12-Based, Multichain, Chimeric Immunoreceptors

Wang and colleagues describe a new multichain, chimeric antigen receptor (CAR) that uses portions of KIR2DS2 to engage DAP12, mimicking natural NK- and T-cell signaling. This new CAR triggers potent T-cell antitumor responses in vivo due to improved retention of CAR surface expression and effector function. Chimeric antigen receptors (CAR) bearing an antigen-binding domain linked in cis to the cytoplasmic domains of CD3ζ and costimulatory receptors have provided a potent method for engineering T-cell cytotoxicity toward B-cell leukemia and lymphoma. However, resistance to immunotherapy due to loss of T-cell effector function remains a significant barrier, especially in solid malignancies. We describe an alternative chimeric immunoreceptor design in which we have fused a single-chain variable fragment for antigen recognition to the transmembrane and cytoplasmic domains of KIR2DS2, a stimulatory killer immunoglobulin-like receptor (KIR). We show that this simple, KIR-based CAR (KIR-CAR) triggers robust antigen-specific proliferation and effector function in vitro when introduced into human T cells with DAP12, an immunotyrosine-based activation motifs-containing adaptor. T cells modified to express a KIR-CAR and DAP12 exhibit superior antitumor activity compared with standard first- and second-generation CD3ζ-based CARs in a xenograft model of mesothelioma highly resistant to immunotherapy. The enhanced antitumor activity is associated with improved retention of chimeric immunoreceptor expression and improved effector function of isolated tumor-infiltrating lymphocytes. These results support the exploration of KIR-CARs for adoptive T-cell immunotherapy, particularly in immunotherapy-resistant solid tumors. Cancer Immunol Res; 3(7); 815–26. ©2015 AACR.