Although recent work demonstrated that therapeutic ATRA treatment of BCR-ABL ALL cultured cells significantly decreased their viability if the leukemic blasts also had IKZF1-mutated or Arf nullizygous alleles21, it was not clear whether a deficiency of host vitamin A would have such a detrimental effect on the host survival from BCR-ABL Arf−/− leukemia. The gene discussed is CDKN2A; the disease is leukemia.