We demonstrated that the interaction between mutant NPM1 and the nuclear exporter Exportin-1 (XPO1) causes the aberrant cytoplasmic delocalization of mutant NPM1 and is responsible for the high expression of HOX genes in NPM1-mutated AML, since relocalization of the NPM1 mutant by XPO1 inhibitors causes early downregulation of HOX genes that is followed by cell differentiation and growth arrest [2, 5]. The gene discussed is NPM1; the disease is acute myeloid leukemia.