Discussion
Cell based High Throughput Screening (HTS) is an integral part of drug discovery but the model provided by a monolayer of cells grown on standard tissue culture plastic may not accurately represent the in vivo environment of the target. More predictive drug responses may be obtained by growing cells in a 3D culture environment that provides a more physiologically relevant model. Inert scaffolds integrated into standard microtiter plates provide a platform to bring 3D cell culture into a High Throughput setting as they have the potential to replace a standard tissue culture plate in a screen without altering throughput. This study assesses the impact of this innovative screening technology at this level of drug discovery.
Cell culture plates with Alvetex polystyrene inert 3D scaffold built into standard 384-well dimensions were optimised for HTS using a cell-based assay from a historic oncology primary screen. The assay uses a luciferase reporter cell line generated to measure activity of a transcription factor associated with determining drug response and resistance. Inhibitors of this pathway are identified after compound incubation with cells followed by detection of luciferase activity. Parallel single shot screens of a 7000 compound diversity set drawn from the broader AZ compound library were carried out using Alvetex plates and standard tissue culture plastic plates.
Alvetex plates were found to be compatible with current automation and liquid handling systems and amenable to HTS current practices. The comparative screen resulted in identification of compounds uniquely active (Robust Z score<-5) in 2D (0.45%) and in 3D (0.27%). A reduction in total hit rate was also observed when using the Alvetex 3D plate (0.84% hit rate in 2D vs. 0.66% hit rate in 3D). Additionally, initial gene expression studies suggest alterations in expression of target genes when cells are cultured on Alvetex plates.
Studies including concentration response curves and chemistry analysis of hits help further determine the significance of screening in Alvetex 3D plate vs. Standard 2D tissue culture plastic.
