Efficient and precise targeting of cancer cells using multiplexed CRISPR/Cas9-nickase and PARP inhibitors

Cancer cell death triggered by DNA damage is the primary therapeutic aim of radiation therapy; however, normal cells are also damaged. Here, we show that RNA-based delivery of only four sgRNAs with Cas9 endonuclease efficiently induces simultaneous DNA double-strand breaks, resulting in efficient cell death in a cell-type-specific manner. To prevent off-target effect caused by Cas9-endonuclease, we used Cas9-nickases to induce DNA single-strand breaks and blocked their repair with PARP inhibitors. When recombinant Cas9-nickase protein and multiple sgRNAs were delivered with PARP inhibitors into culture cells, in vivo xenografts and patient-derived cancer organoids via lipid nanoparticles, cancer cells were unable to tolerate the DNA damages, even in the presence of functional BRCA2 gene. This approach has the potential to expand the use of PARP inhibitors with verified safety, making it a potentially powerful tool for personalized cancer therapy based on the genome.