Retargeting of human natural killer cell line cytolytic activity to CEA-expressing cancer cells results in specific tumor cell destruction

The continuously growing and IL-2-independent natural killer (NK) cell line NK92MI is highly cytotoxic against malignant cells of various origins without affecting normal human cells. These properties suggest that NK92MI may be a good candidate as an immunotherapeutic agent. To further enhance the antitumoral activity of NK92MI cells and expand the range of tumor entities suitable for NK92MI–based therapies, here by transduction with a retroviral vector we have generated genetically modified NK92MI cells expressing a chimeric antigen receptor (CAR) specific for the tumor-associated carcinoembryonic antigen (CEA), which is overexpressed in many tumors of epithelial origin. The CAR consists of the CEA-specific single chain antibody (scFv), a flexible hinge region derived from CD8, and transmembrane and intracellular regions of the CD3ζ chain. Transduced NK92MI-scFv (CEA) -ζ cells express significant levels of the fusion protein on the cell surface as determined by fluorescence-activated cell-scanning (FACS) analysis. In cytotoxicity assays, there was no difference in cytotoxic activity of NK92MI and NK92MI-scFv (CEA) -ζ cells toward CEA-negative targets. However, even at low effector-to-target ratios, NK92MI-scFv (CEA) -ζ cells specifically and efficiently lysed CEA-expressing tumor cell lines that were resistant to cytolytic activity of parental NK92MI cells. These results demonstrate that efficient retargeting of NK92MI cytotoxicity can be achieved and might allow the generation of potent cell-based therapeutics for the treatment of CEA-expressing malignancies.