As a role of MMP-9 (and the ECM-degrading enzyme heparanase), derived from the BMM, had not previously been implicated in B-ALL, we transplanted wild type BM transduced with retrovirus expressing the oncogene BCR-ABL1, which is associated with 3% of pediatric B-ALL and 25% of adult B-ALL, into heparanase- or MMP-9-deficient or control recipient mice. The gene discussed is HPSE; the disease is precursor B-cell acute lymphoblastic leukemia.