Abstract 5294: Increased angiogenesis resulting from TIMP-1 inhibition of TSP-1 is mediated by PI3kinase and FAK interactions

Abstract

Abstract Tissue Inhibitor of Matrix Metalloprotease -1 (TIMP-1), one of the four natural inhibitors of matrix metalloproteinases was initially identified for its Erythroid Potentiating Activity. Since then, it has been shown to independently induce cell proliferation and inhibit apoptosis in a number of cell types. TIMP-1 has also been shown to promote, but also more often to inhibit angiogenesis. Previously, we have shown that TIMP-1 overexpression in a lung adenocarcinoma cell line (H2009) resulted in more aggressive and vascular tumors in nude mice and increased capillary network formation and tumorigenicity in vitro. An angiogenesis pathway-specific gene array had identified a 3-fold reduction in thrombospondin 1 (TSP-1) levels in the TIMP-1 overexpressing clone HB-1. TSP-1 siRNA clone exhibited a similar increase in in vitro angiogenesis assays. In the present study, we have sought to identify the signaling pathway involved whereby TIMP-1 inhibits TSP-1. To this end, we have used specific inhibitors to inhibit TIMP1 initiated signaling pathways. MAP kinase, PI3/Akt inhibitors were used, either singly or in combination with Focal Adhesion kinase (FAK) inhibitor. Our results indicate a synergistic interaction between PI3/Akt pathway and FAK signaling, which restores TSP-1 levels by approximately 3-fold relative to control. Gelatin zymography of serum-free conditioned media (SFCM) revealed a reduction in proMMP-9 level in the HB-1 clone versus H2009. Additionally MMP9 specific ELISA reveals a two-fold reduction in MMP9 levels. This is in tune with the role of TSP-1 as an inhibitor of MMP-9 activation such that decreased TSP-1 level results in increased activation of MMP-9 with a concomitant reduction in the extracellular level of proMMP-9. Thus our findings define interaction of TIMP-1 via PI3kinase and FAK signaling. resulting in TSP-1 decrease and subsequent downstream promotion of angiogenesis with increased tumor kinetics. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5294. doi:1538-7445.AM2012-5294