A previous study using a MLL-AF9 AML model also supports the conclusion that telomerase activity is not mandatory for leukemia initiation, but its deficiency negatively affects the self-renewal capacity and frequency of functional LSC and reduces the leukemia burden; LSC lacking telomerase activity showed chromosomal instability, increased apoptosis and induction of the p53 pathway [197]. This evidence concerns the gene KMT2A and leukemia.