FGFR1 and leukemia: Thus there are two potential mechanisms by which FGFR inhibition can attenuate protection of leukemia cells in the marrow microenvironment: (1) FGFR inhibitors block FGF2-mediated paracrine protection at the leukemia cells; and/or (2) FGFR inhibitors interrupt stromal FGF2-FGFR1 autocrine signaling to reduce secretion of protective FGF2-containing exosomes.