Three-way combinatorial CRISPR screen for analyzing interactions among druggable targets

We present a CRISPR-based multi-gene knockout screening system and new toolkits for extensible assembly of barcoded high-order combinatorial guide RNA libraries en masse. We apply this system for systematically identifying not only pairwise but also three-way synergistic therapeutic target combinations, and successfully validated double and triple combination regimens for suppression on cancer cell growth and protection against Parkinson's disease-associated toxicity. This system overcomes the practical challenges to experiment on a large number of high-order genetic and drug combinations, and is applicable for uncovering the rare synergistic interactions between druggable targets. Overall design: Performed combinatorial CRISPR-mediated gene knockout screens in ovarian cancer and Parkinson's disease cell models.