However, by analyzing cancer patients (metastatic melanoma, renal cell carcinoma, refractory Hodgkin’s disease, and refractory AML) subjected to adoptive transfer of human NK cells from haploidentical-related donors, Miller and collaborators demonstrated that transferred NK cells can be expanded in vivo and that expansion is dependent on the more intense cyclophosphamide/fludarabine chemotherapy regimen that induces lymphopenia and high endogenous concentrations of IL-15, which are not observed when lower doses of chemotherapy are administered. The gene discussed is IL15; the disease is acute myeloid leukemia.