Using organoids sourced from mouse intestinal tumors with a mutated APC and mutated Kras background (APCΔ716, Kras +/G12D) (both commonly mutated genes in colorectal cancer), they transduced the organoids with lentiviral vectors containing Cas9 and GFP, followed by lentivirus transduction with viral particles containing pools of tumor suppressor candidate gene gRNAs. The gene discussed is KRAS; the disease is intestinal neoplasm.