We now show that FGFR1 fusion kinase-mediated activation of IRAK1 in SCLL cells leads to increased accumulation of myeloid-derived suppressor cells (MDSCs) in vivo with a concomitant suppression of CD4/CD8 T-cells promoting an immune suppressive microenvironment leading to leukemia development. This evidence concerns the gene FGFR1 and leukemia.