Genome-wide CRISPR Screen in a Mouse Model of Tumor Growth and Metastasis

• Genome-wide in vivo CRISPR-Cas9 screen in mice reveals genes regulating lung metastasis
• Screen identifies loss-of-function mutations in known tumor suppressors and novel genes
• Candidate metastasis genes are validated using a pooled competition assay
• Effect of mutations on primary tumor growth positively correlates with metastasis

SummaryGenetic screens are powerful tools for identifying genes responsible for diverse phenotypes. Here we describe a genome-wide CRISPR/Cas9-mediated loss-of-function screen in tumor growth and metastasis. We mutagenized a non-metastatic mouse cancer cell line using a genome-scale library with 67,405 single-guide RNAs (sgRNAs). The mutant cell pool rapidly generates metastases when transplanted into immunocompromised mice. Enriched sgRNAs in lung metastases and late-stage primary tumors were found to target a small set of genes, suggesting that specific loss-of-function mutations drive tumor growth and metastasis. Individual sgRNAs and a small pool of 624 sgRNAs targeting the top-scoring genes from the primary screen dramatically accelerate metastasis. In all of these experiments, the effect of mutations on primary tumor growth positively correlates with the development of metastases. Our study demonstrates Cas9-based screening as a robust method to systematically assay gene phenotypes in cancer evolution in vivo.

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