Interestingly, starting with the same patient but using different mouse recipients, i.e. NSG mice producing human interleukin 3, stem cell factor and GM-CSF previously described as better recipients for human AML [22], the same authors observed the reproducible selection of different subclones, indicating the important role of the mouse microenvironment in the selection process, at least for myeloid leukemia [21]. Here, CSF2 is linked to acute myeloid leukemia.