MMP9 and precursor B-cell acute lymphoblastic leukemia: While the knockdown of Tnfα in leukemia cells in our study prolonged the survival of mice with B-ALL by a concomitant reduction in MMP-9 production by the BMM (Fig. S8E), the impairment of autocrine, leukemia-promoting secretion of Tnfα, as shown in CML [46], may be contributory.