The OH-BBN-induced bladder tumors in mice express basal subtype cell markers (i.e., Cd44, Cdh3, Krt5, and Krt14) with highly frequent mutations (70 to 90%) of Trp53 and H3K4 methyltransferase family members, including lysine methyltransferase 2C (Kmt2c) and Kmt2d, which closely mimic the basal/squamous type of human muscle-invasive bladder cancer, both molecularly and pathologically [7,8,9]. The gene discussed is KMT2D; the disease is urinary bladder neoplasm.