In vivo CRISPR screens identify COPS5 as a regulator of sorafenib resistance  in hepatocellular carcinoma
To identify novel vulnerabilities to sorafenib treatment in hepatocellular carcinoma, an in vivo CRISPR screen was performed. First, a stable Cas9-expressing H22 cell line was established by transfection with lenti-Cas9 viruses, followed by blasticidin selection. Then, we transduced H22-Cas9 with mGeKOv2 library at a low MOI for 24h, after which the transduced cells were screened by puromycin for 7 days. Subsequently, cells were split into four groups at equal densities, two were used for screening in Nude mice and two for screening in BALBc mice. Cells were injected subcutaneously into mice, which were then treated with vehicle and sorafenib for 14 days. After treatment, tumors were harvested and genomic DNA from whole tumor tissue was isolated using a DNA extraction kit. Sequences of sgRNAs were amplified by PCR, and the amplicons were sequenced using next-generation sequencing. Significantly depleted sgRNAs were identified using the MAGeCK algorithm.