CRISPR/Cas9 system has been widely applied in exploring the molecular mechanism of tumorigenesis, generating the models for cancer research and identifying the targets for cancer treatment, etc. A genome-wide CRISPR screen shows that loss-of-function mutations of some genes including NF2, PTEN, CDKN2A, TRIM72, FGA, miR-152, miR-345, and so on are able to drive tumor growth and metastasis in a mouse model (24). The gene discussed is FGA; the disease is cancer.