Comprehensive Analysis of Drug Response using the FLICK Assay

For understanding drug efficacy, a critical need is to characterize the extent of drug-induced cell death. Efforts to quantify the level of drug-induced cell death are challenged by the existence of more than a dozen molecularly distinct forms of regulated death, each with its own activation timing and biochemical hallmark features. Furthermore, for some necrotic death subtypes, hallmark features are only observed transiently and are rapidly lost due to cell rupture. Thus, even when using a combination of death pathway-specific assays, it is challenging to accurately quantify the total amount of cell death or the relative contributions of each death subtype. Another issue is that many death-specific assays ignore how drugs affect cell proliferation, making it challenging to interpret if a drug-treated population is expanding or shrinking. The FLICK assay allows for quantification of the total level of cell death following stimulation in a manner that is specific to death but also largely agnostic to the type(s) of death activated. Additionally, the FLICK assay retains information about the total population size and cell proliferation rate. In this manuscript, we describe the basic use of the FLICK assay, how to troubleshoot this assay when using different types of biological material, and how to use the FLICK assay to quantify the contributions of each type of cell death to an observed drug response.