Fig 4. Combined inhibition of MET and FGFR1 blocks compensatory upregulation of HGF, leading to sustained inhibition of MET in KG-1 cells and to near-complete regression of AML in vivo.
(a) Bioluminescence measurements of leukemic mice engrafted with luciferase-modified KG-1 cells and treated with vehicle control (black), 50 mg−1 kg−1 crizotinib alone (orange), 25 mg−1 kg−1 PD173074 (blue), or a combination of crizotinib and PD173074 by daily oral gavage (green). Values are means and standard deviations of each treatment group (n = 9). * p < 0.05 versus each remaining group. (b) Bioluminescent photographs of representative mice from each treatment group (blue-to-red color gradient represents increasing bioluminescence intensities). (c,d) Scatter plots of the fraction of human CD45+ KG-1 cells in the peripheral blood (c) and bone marrow (d) of mice after 10 days of treatment, demonstrating near-complete elimination of human AML cells in mice treated with the combination of crizotinib and PD173074. Boxes denote means and standard deviation for each group (n = 9). * p < 0.05 versus vehicle control group. (e,f) Abundance of HGF (e) and phospho-MET (f) in human CD45-selected KG-1 cells isolated from the bone marrow of mice after 10 days of treatment as indicated, demonstrating blockade of compensatory HGF upregulation in response to crizotinib treatment by the combined inhibition of MET and FGFR1, and sustained inhibition of MET activation.