These chromosome translocations are believed to occur following DNA DSBs induced by poisoned TOP2 activity [3, 8, 9, 10] and are crucial early events in the development of these therapy‐related leukaemias; the resulting fusion genes, for example MLL‐AF9, are able to induce leukaemia in animal models [11, 12]. Here, KMT2A is linked to leukemia.