Cross-talk of Integrin α3β1 and Tissue Factor in Cell Migration

Abstract

In cancer and angiogenesis, coagulation-independent roles of tissue factor (TF) in cell migration are incompletely understood. Immobilized anti-TF extracellular domain antibodies induce cell spreading, but this phenomenon is epitope specific and is not induced by anti-TF 5G9. Spreading on anti-TF is ␤1 integrin-dependent, indicating functional interactions of the TF extracellular domain 5G9 epitope (a presumed integrin-binding site) and integrins. Recombinant TF extracellular domain supports adhesion of cells expressing ␣v␤3 or certain ␤1 integrin heterodimers (␣3␤1, ␣4␤1, ␣5␤1, ␣6␤1, ␣9␤1) and adhesion is blocked by specific anti-integrin antibodies or mutations in the integrin ligand-binding site. Although several studies have linked TF to cell migration, we here demonstrate that TF specifically regulates ␣3␤1-dependent migration on laminin 5. Expression of TF suppresses ␣3␤1-dependent migration, but only when the TF cytoplasmic domain is not phosphorylated. Suppression of migration can be reversed by 5G9, presumably by disrupting integrin interaction, or by the protease ligand VIIa, known to induce PAR-2-dependent phosphorylation of TF. In both cases, release of ␣3␤1 inhibition is prevented by mutation of critical phosphorylation sites in the TF cytoplasmic domain. Thus, TF influences integrin-mediated migration through cooperative intra-and extracellular interactions and phosphorylation regulates TF's function in cell motility. INTRODUCTIONTissue factor (TF) is the cell surface receptor for the serine protease coagulation factor VIIa (VIIa; Ruf and Edgington, 1994). The complex of TF-VIIa activates the coagulation cascade, leading to thrombin generation, fibrin formation, and platelet activation. Local fibrin deposition is frequently observed in malignancy and TF plays an important role in cancer invasion and metastasis (Dvorak et al., 1992;Shoji et al., 1998). TF supports metastatic tumor dissemination (Mueller et al., 1992) by fibrin-dependent pathways (Palumbo et al., 2000), by aiding thrombin-dependent tumor cell survival (Fischer et al., 1995;Ruf and Mueller, 1996;Zain et al., 2000), and through signaling that involves the short TF cytoplasmic domain (Bromberg et al., 1995;Mueller and Ruf, 1998). TF is also found at the leading edge of invasive tumors (Fischer et al., 1999) and in angiogenic endothelial cells (Contrino et al., 1996). In vitro studies documented a close association of TF with cytoskeletal structures (Carson et al., 1994;Ott et al., 1998;Mü ller et al., 1999) and indicated potential roles in regulating cell motility, such as reverse endothelial cell migration of monocytes (Randolph et al., 1998), enhanced chemotactic fibroblast migration (Siegbahn et al., 2000), and tumor cell adhesion and migration on extracellular ligands for TF (Ott et al., 1998;Fischer et al., 1999). In TF cytoplasmic domain-deleted mice, we have recently provided evidence that the TF cytoplasmic domain can negatively regulate angiogenesis and endothelial sprouting (Belting et al., 2004). However, the molecular intera...

Tissue factor as an effector of angiogenesis and tumor progression in hematological malignancies

“…5 Concomitantly, fresh leukemia samples also expressed the VEGF receptor KDR, thus indicating, as above suggested, the possibility of an autocrine pathway in which the tumor cells may stimulate their own growth after VEGF exposure. 37,38 In addition, almost all the blast samples showing increased TF and VEGF levels also exhibited enhanced ERK phosphorylation in agreement with previous studies, which demonstrated that some transcription factors regulating TF can also induce VEGF transcription. 5 Accordingly, MAPK seems to be a common pathway that regulates, independently, VEGF and TF expression and, at the same time, is involved in the control of TF or VEGF expression induced by each other.…”

“…Thus, TF-VIIa signaling may simultaneously counteract integrin suppression by phosphorylating the TF cytoplasmic domain and locally triggering proinvasive PAR2 activation. 37 Finally, thrombin generation downstream of TF also plays a central role in the metastatic process, and thrombin's effects on tumor cells are generally assumed to be mediated by PAR1. Expression of PAR1 in tumor cells has been associated with increased tumor invasiveness and metastasis.…”

“…6 Indeed, upregulation of VEGF and angiogenesis has been recently demonstrated in acute leukemia patients. 37,38 Both TF and VEGF can be induced by constitutive activation of oncogenic proteins such as Raf, MEK or PI3K, acting at various levels of the Ras signaling pathway. 60 In that way, a recent study has investigated in a subset of acute leukemia samples the expression and activation status of TF, VEGF and two intracellular proteins involved in their regulation: the extracellular-regulated kinase (ERK1/2) and the NFkB (Barbarroja et al Pathophysiol Haemost Thromb 2004: 33; abstract).…”

Alternatively spliced tissue factor induces angiogenesis through integrin ligation

“…Moreover, TF affects tumor angiogenesis in colorectal cancer and breast cancer models, through TF:VIIadependent protease-activated receptor-2 (PAR-2) activation (9)(10)(11), resulting in expression of VEGF, IL-8, MMP-7, and CXCL-1 (10)(11)(12)(13). In addition, TF binds ␣3␤1 and ␣6␤1 integrins, and disruption of this complex downregulates pro-angiogenic signaling and suppresses tumor growth in vivo (11,14).…”

Cryptic messages: Is noncoagulant tissue factor reserved for cell signaling?

“…Is PDI able to bridge the interaction between TF and PAR2, or is there a direct TF:PAR2 interaction? Ruf and colleagues (14,15) have suggested another regulatory switch whereby TF cytoplasmic tail phosphorylation promotes PAR2 signaling and simultaneously releases TF from a complex with integrins. How does PDI and TF disulfide switching fit with this model?…”