Abstract 1933: Improved DAMP assays for the in vitro assessment of immunogenic cell death

The extracellular levels of damage-associated molecular patterns (DAMPs) released during immunogenic cell death (ICD) are positively correlated with the magnitude and efficacy of the resulting in vivo immune response. Therefore, extracellular ATP (eATP) and high mobility group box 1 (HMGB1) have been identified as key biomarkers for their predictive capacity during in vitro ICD screening activities. Current methods for identifying eATP and HMGB1 inducers are laborious, costly, and hampered by poor throughput. To overcome these challenges, we developed easy-to-use, homogeneous, bioluminescent assays that measure dose-dependent release of these immunostimulatory agents directly in cell culture. The eATP assay utilizes an optimized ATP detection chemistry that can be employed directly to assess live-cell kinetic responses for up to 24 h, with even longer exposures supported by a staggered reagent addition approach. The HMGB1 assay measures the protein9s concentration at exposure endpoint in the same sample well using complementary luciferase fragment-labelled monoclonal antibodies. We tested the utility of the assays using U20S, Jurkat and U937 cells dosed with serial dilutions of known ICD inducers (doxorubicin, idarubicin, mitoxantrone, and bortezomib). The resulting data suggest the potency of eATP and HMGB1 release is dependent upon cell model and agent but can be reproducibly and robustly measured in 96 and 384 well environments. Further, the eATP assay produced remarkable early dose-dependent response resolution whereas the HMGB1 data provided a confirmatory post-mortem ICD parameter. This new ICD biomarker detection workflow may help to efficiently define and rank-order the capacity of new chemical entities to induce apoptosis and immunogenic cell death. Citation Format: Andrew L. Niles, Kevin R. Kupcho, Dan F. Lazar, James J. Cali. Improved DAMP assays for the in vitro assessment of immunogenic cell death [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 1933.