Leukaemia stem cells (LSCs), which are responsible for the occurrence and progression of leukaemia in MLLr-AML, are maintained by the formation of MLL-fusion supercomplex with the SEC (super elongation complex) and DOT1L (disruptor of telomeric silencing one like) at the HOXA (homeobox A) gene locus [3, 4]. The gene discussed is KMT2A; the disease is leukemia.