IGF1 and acute myeloid leukemia: Primary human AML cells express insulin and IGF receptors,23 and a recent article described associations between pretreatment serum levels of various IGF binding proteins and between the serum fraction of bound IGF and a favorable prognosis with increased survival.24 Systemic insulin/IGF levels thus seem important for the effect of insulin/IGF1 in the AML cell microenvironment, and experimental studies further suggest that both insulin25,26 and IGF27 have growth-enhancing and/or antiapoptotic effects in primary human AML cells.