CAR-NK and CAR-T cells versus CTL: factors limiting the sensitivity and efficiency of engineered cytolytic effectors
Nadia Anikeeva1, Nicholas Mazzanti1, Takami Sato2,3 and Yuri Sykulev1,2,3
Departments of 1Microbiology and Immunology and 2Medical Oncology, 3Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107, USA
Factors limiting highly sensitive and efficient responses of virus- and cancer-specific CTL have been extensively studied. But the sensitivity and effectiveness of T cells transduced with CAR specific for target molecules on cancer cells is less well understood. We endowed NK92 cells and T cells purified from human cord blood with second generation CAR specific for High Molecular Weight Melanoma Associated Antigen (HMW-MMA) and compared the ability of CAR-NK92 and CAR-T cells to kill skin melanoma and uveal melanoma cell lines in in vitro cytolytic assay. We also evaluated the ability of established human virus-specific CTL clones to kill the same target cells presenting cognate pMHC ligands. Skin melanoma cells were more sensitive to specific lysis than uveal melanoma cells. The extent of the specific lysis strongly depended on the level of HMW-MMA expression. CTL clones appeared to be more superior effectors than CAR-NK92 or CAR-T cells as they lysed the melanoma cells that displayed much lower levels of cognate pMHC ligands. CAR-NK92 cells proliferated more vigorously than NK92 cells and maintained the level of CAR expression in culture. In contrast, CAR-CD8+T cells exhibited lower proliferative capacity than the control T cells and were losing cell surface CARs and the ability to specifically lyse melanoma cells with each cycle of stimulation in vitro. We are currently evaluating the extent of TCR vs CAR clustering and co-clustering of CAR with TCR at the cell surface. We are also comparing Ca2+ flux and release of cytolytic granules by CAR-NK92, CAR-CD8 T cells and CTL in response to CAR and TCR stimulation. Differences in these parameters could account for differential sensitivity and efficiency of engineered and natural cytolytic effectors.
Funding: this work was supported by The Dean’s Transformational Science Award
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