NPM1 and acute myeloid leukemia: Later studies using immunodeficient mice – which are more permissive for engraftment of human cells – showed that human AML-LSCs from most patients reside in the CD34+/CD38- or CD34+/CD38+ population, and in a few AMLs such as NPM1 mutant AML, may also be present in the CD34- population (7, 8).