title: Overexpression of progelatinase B/proMMP-9 affects migration regulatory pathways and impairs chronic lymphocytic leukemia cell homing to bone marrow and spleen.
abstract: This study addresses the role of (pro)MMP-9 overexpression in CLL cell migration. We have used primary CLL cells and CLL-derived MEC-1 cells transfected with empty (mock cells) or proMMP-9-encoding (MMP-9 cells) lentiviral vectors. The constitutive (pro)MMP-9 expression in mock cells and primary CLL cells was similar, whereas in MMP-9 cells, expression resembled that of CLL cells incubated with proMMP-9. In xenograft models, in NOD/SCID mice, MMP-9-MEC-1 transfectants showed significantly reduced homing to bone marrow and spleen compared with mock cells. Likewise, incubation of primary CLL cells with proMMP-9, before injection into mice, inhibited their homing to these organs. This inhibition was specific, dose-dependent, and observed in all CLL tested, independently of prognostic markers or disease stage. Additionally, the MMP-9 catalytic activity was only partially involved, as the inactive mutant proMMP-9MutE had a partial effect. MMP-9 cells also showed impaired migration in vitro, which was reverted by reducing (pro)MMP-9 expression with siRNAs. CLL migration thus requires optimal (pro)MMP-9 expression levels, below or above which migration is hampered. Biochemical analysis of the (pro)MMP-9 effect indicated that MMP-9 cells or primary CLL cells incubated with proMMP-9 had reduced activation of migration regulatory molecules, including RhoAGTPase, Akt, ERK, and FAK. In contrast, p190RhoGAP (RhoA inhibitor) and PTEN (Akt/ERK/FAK inhibitor) were up-regulated in MMP-9 cells. Reduction of (pro)MMP-9 expression by siRNAs restored RhoA activity and diminished PTEN levels. Our results reveal a novel function for (pro)MMP-9 in modulating signaling pathways leading to CLL cell arrest. Therefore, local high (pro)MMP-9 expression may contribute to malignant cell retention in lymphoid organs and disease progression.
authors.affiliation: *Cellular and Molecular Medicine Department, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain;
authors.forename: Elvira
authors.initials: E
authors.lastname: Bailón
authors.forename: Estefanía
authors.initials: E
authors.lastname: Ugarte-Berzal
authors.forename: Irene
authors.initials: I
authors.lastname: Amigo-Jiménez
authors.forename: Philippe
authors.initials: P
authors.lastname: Van den Steen
authors.forename: Ghislain
authors.initials: G
authors.lastname: Opdenakker
authors.forename: José A
authors.initials: JA
authors.lastname: García-Marco
authors.forename: Angeles
authors.initials: A
authors.lastname: García-Pardo
keywords: CLL; PTEN; RhoA; lymphoid organs