KMT2A and leukemia: It is suggested that the intracellular KMT2A proto-oncogene in patients with MLLrs promotes the differentiation of leukemia cells to one lineage, while the leukemia cells tend to differentiate to another lineage; lineage transformation occurs when the treatment affects the expression level of the KMT2A proto-oncogene.53 Some patients with lineage conversion have multiple lineage switches during the course of the disease, which may also be related to the fluctuating expression levels of proto-oncogenes.5,8,36,49,54,55