FN1 and acute lymphoblastic leukemia: The higher levels of fibronectin in the BMM and higher MMP-9 levels in the plasma of BM aspirates of healthy individuals and CML compared with B-ALL patients may seem contradictory, but may be explained by the increased production of MMP-9 by myeloid cells [18], the production of fibronectin by CML cells [51], or by other compensatory factors.