Abstract 4648: Using the IntelliCyt iQue Screener to simultaneously profile antibody dependent cell cytotoxicity and cytokine release of therapeutic antibodies
Authors: O'Rourke John 
Published: August 2018

Therapeutic antibodies can mediate cancer cell killing through a variety of mechanisms including antibody dependent cell-mediated cytotoxicity (ADCC), antibody dependent cellular phagocytosis (ADCP) and complement dependent killing (CDC). ADCC is induced through the binding of the antibody Fc region to Fc receptors (FcRs) expressed on effector cells of the immune system. Granule exocytosis of perforin, granzyme B, the induction of Fas ligand (FasL) expression on immune cells and the release of cytokines are major mechanisms involved in targeted cancer cell killing.

Traditional approaches to screen for antibody Fc effector functions focus on ADCC using a homogenous live/dead readout, which greatly limits the contextual and correlative value of the screening data. To overcome this limitation, a multiplex screening assay profiling ADCC using multiple cell death endpoints, and quantitating secreted proteins /cytokines was developed and analyzed using Intellicyt's iQue Screener PLUS and integrated ForeCyt software. The iQue Screener Plus is a high throughput flow cytometry platform featuring 3 lasers with 13 fluorescent channels and can sample a 384-well plate in 20 minutes.

As a proof of concept, a small set of therapeutic antibodies directed against the same tumor antigen were used to induce immune cell-mediated killing of tumor cells using different effector to target cell ratios and a range of antibody concentrations. To demonstrate antibody specificity, antigen positive target cells, negative control target cells and effector immune cells were barcoded with different encoding dyes and included in the same well. At specific times, a small aliquot from each well was transferred to a new assay plate to run a multiplexed cell/bead mixture assay by the addition of a cocktail of fluorescent immunophenotyping antibodies, fluorescent dyes measuring unique apoptosis parameters, and a panel of QBeads for secreted protein detection. The samples were assayed on the IntelliCyt iQue Screener PLUS with simultaneous data analysis including multi-plate analysis for cell killing kinetics. Positive/negative target cells and immune cells were digitally segregated by differently encoded fluorescence. Time-dependent cell killing of antigen positive target cells were observed using the apoptosis markers mitochondria depolarization staining and cell membrane integrity, whereas little killing was measured in antigen negative cells. The antibody set showed a range of ADCC mediated killing and granule exocytosis/ cytokine release suggesting differences in Fc effector functions. These results highlight the streamlined workflow on IntelliCyt iQue Screener PLUS platform to profile therapeutic antibodies in a functional ADCC/cytokine release assay predicting their clinical efficacy.

Citation Format: John O'Rourke. Using the IntelliCyt iQue Screener to simultaneously profile antibody dependent cell cytotoxicity and cytokine release of therapeutic antibodies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4648.