Abstract 1306: Primary NK cells and luciferase expressing reporter cell lines for use in developing ADCC assays for immuno-oncology drug screening

Abstract

Abstract Immuno-oncology is one of the fastest growing fields in oncology, and cancer immunotherapy in recent years represents a milestone in the treatment of cancer. Natural killer (NK) cells are potent innate effectors capable of targeting and killing virally infected and malignant cells. The use of monoclonal antibodies (mAbs) targeting tumor antigens triggers antibody-dependent cellular cytotoxicity (ADCC) by NK cells, which has shown prominent clinical efficacy in clearing tumors in cancer patients. Therefore, the development of tumor cell targeting mAbs and biologics dictate a clear need for human cell-based models to evaluate antibody efficacy. In this study, human PBMCs and purified NK cells from healthy donors are used to develop an ADCC assay. The NK cells purified from PBMCs are >90% CD45+ CD56+, express high levels of CD16, and NK activation markers such NKG2A, KIR2DL1, NKp44 upon activation. The activated NK cells exhibit both strong direct and antibody-dependent cytotoxicity. Genotyping for FcγRIIIa receptor F and V variant is also performed for cells isolated from different donors, which is the genetic polymorphism that affects ADCC response. In addition, we employ a portfolio of luciferase reporter tumor cell lines to evaluate NK cell direct killing and ADCC targeted killing. These include K562, Wil2S, BT474, A431, A375 parental, and CRISPR edited A375 KRAS mutant cell lines engineered to express luc2 reporter. The commonly targeted cell surface markers, such as CD20, Her2, and EGFR, are highly expressed within this panel of target tumor cell lines. We validate the ADCC assay system through testing the efficacy for some of the well-known mAb biologics such as anti-CD20, anti-HER2, and anti-EGFR. After co-culture of activated primary NK cells with luciferase reporter target cell lines and the addition of dilutions of ADCC and isotype control antibodies, we are able to show target cell specific and dose-dependent killing effects. The luciferase reporter provides great convenience in measuring target cell killing without having to use radioactive 51Cr release assay or pre-label the cells with calcein. This data demonstrates the utility of primary NK cells along with a portfolio of well characterized luciferase reporter tumor cell line to develop “custom” designed ADCC assays for studying NK cell immune response and screening for biological drugs for cancer immunotherapy. Citation Format: Haiyun Liu, Brian Della Fera, John Foulke, Luping Chen, Fang Tian. Primary NK cells and luciferase expressing reporter cell lines for use in developing ADCC assays for immuno-oncology drug screening [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1306.