We developed an short-term in vitro cell co-culture assay to determine the influence of the age of stroma cells on the expansion of AML-ETO+ myeloproliferation-initiating LSK cells in vitro[26], [35] to determine whether this 2D in vitro co-culture assay might be able to re-capitulate the increase in AML-ETO+ LSK cells in an aged microenvironment, which would then allow to further determine cellular and molecular mechanisms. This evidence concerns the gene RUNX1T1 and acute myeloid leukemia.