To that end, we infected the KMT2A-r B-ALL cell lines SEM and RS4,11 (carrying a KMT2A-AF4 fusion), the KMT2A-r AML cell lines MV4,11 (carrying a KMT2A-AF4 fusion), and THP1 (carrying a KMT2A-AF9 fusion) with lentiviral Cas9 and a sgRNA against SPOP (sgRNA-5). The gene discussed is AFF1; the disease is acute myeloid leukemia.