Of 20 bladder cancer cell lines, 9 were enriched for APOBEC mutagenesis, and had frequent mutations in TP53 (89%) and ARID1A (33%), while 11 cell lines were not enriched for APOBEC mutagenesis and had frequent mutations in FGFR3 (27%) and NRAS (27%) (Figure 3F). The gene discussed is ARID1A; the disease is urinary bladder cancer.