Coagulation activation by tissue factor (TF) is implicated in cancer progression, cancer-associated thrombosis and metastasis. The role of direct TF signaling pathways in cancer, however, remains incompletely understood. Here we address how TF contributes to primary tumor growth by using a unique pair of isotype-matched antibodies that inhibit either coagulation (monoclonal antibody [Mab]-5G9) or direct signaling (Mab-10H10). We demonstrate that the inhibitory antibody of direct TF-VIIa signaling not only blocks TF-VIIa mediated activation of PAR2, but also disrupts the interaction of TF with integrins. In epithelial and TF-expressing endothelial cells, association of TF with beta1 integrins is regulated by TF extracellular ligand binding and independent of PAR2 signaling or proteolytic activity of VIIa. In contrast, alpha3beta1 integrin association of TF is constitutive in breast cancer cells and blocked by Mab-10H10 but not by Mab-5G9. Mab-5G9 has antitumor activity in vivo, but we show here that Mab-10H10 is at least as effective in suppressing human xenograft tumors in 2 different models. Breast tumor growth was also attenuated by blocking PAR2 signaling. These results show that tumor cell TF-PAR2 signaling is crucial for tumor growth and suggest that anti-TF strategies can be applied in cancer therapy with minor impairment of TF-dependent hemostatic pathways.

Defining critical points of modulation across heterogeneous clinical syndromes may provide insight into new therapeutic approaches. Coagulation initiated by the cytokine-receptor family member known as tissue factor is a hallmark of systemic inflammatory response syndromes in bacterial sepsis and viral haemorrhagic fevers 1,2 , and anticoagulants can be effective in severe sepsis with disseminated intravascular coagulation 3 . The precise mechanism coupling coagulation and inflammation remains unresolved 4-7 . Here we show that protease-activated receptor 1 (PAR1) signalling sustains a lethal inflammatory response that can be interrupted by inhibition of either thrombin or PAR1 signalling. The sphingosine 1-phosphate (S1P) axis is a downstream component of PAR1 signalling, and by combining chemical and genetic probes for S1P receptor 3 (S1P3) we show a critical role for dendritic cell PAR1-S1P3 cross-talk in regulating amplification of inflammation in sepsis syndrome. Conversely, dendritic cells sustain escalated systemic coagulation and are the primary hub at which coagulation and inflammation intersect within the lymphatic compartment. Loss of dendritic cell PAR1-S1P3 signalling sequesters dendritic cells and inflammation into draining lymph nodes, and attenuates dissemination of interleukin-1b to the lungs. Thus, activation of dendritic cells by coagulation in the lymphatics emerges as a previously unknown mechanism that promotes systemic inflammation and lethality in decompensated innate immune responses.Disseminated intravascular coagulation and systemic inflammation are signs of excessive activation of the innate immune system. Both are attenuated by genetic reduction of tissue factor and its protease ligand coagulation factor VIIa, leading to improved survival in endotoxaemia 6,8 . In a model of severe, but not completely lethal lipopolysaccharide (LPS) challenge 9 , we show that PAR1 deficiency protects mice from lethality (Fig. 1a). PAR1 2/2 mice initially developed elevated inflammation and coagulation markers indistinguishable from the wild type (Fig. 1b, c). Unlike the wild type, PAR1 2/2 mice progressively resolved systemic inflammation beginning at 12 h. To address whether coagulation amplifies inflammation signalling. a, Survival advantage of PAR1 2/2 mice in 90% lethal LPS challenge induced by intraperitoneal injection of 8 mg kg -1 LPS (summary of three independent experiments, n $ 28 per genotype, PAR1 2/2 survival advantage for each individual experiment, P , 0.05). b, Reduced late-stage inflammation in PAR1 2/2 mice documented by IL-6 and IL-1b levels (mean 6 s.d., n 5 18 per group, asterisks indicate groups that are different from the wild type (WT), P , 0.05). c, TAT levels in wild-type and PAR1 2/2 mice, or wild-type mice treated at 10 h with PAR1 antagonist RWJ58259 (P1ant) or the thrombin inhibitor hirudin (Hir). d, Intervention with PAR1 antagonist or hirudin improves survival, similarly to PAR1 deficiency (n 5 8 per group, P , 0.02 relative to wild-type control). e, Intervention with P...

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Integrins are transmembrane heterodimeric proteins sensing the cell microenvironment and modulating numerous signalling pathways. Changes in integrin expression between normal and tumoral cells support involvement of specific integrins in tumor progression and aggressiveness. This review highlights the current knowledge about α5β1 integrin, also called the fibronectin receptor, in solid tumors. We summarize data showing that α5β1 integrin is a pertinent therapeutic target expressed by tumoral neovessels and tumoral cells. Although mainly evaluated in preclinical models, α5β1 integrin merits interest in particular in colon, breast, ovarian, lung and brain tumors where its overexpression is associated with a poor prognosis for patients. Specific α5β1 integrin antagonists will be listed that may represent new potential therapeutic agents to fight defined subpopulations of particularly aggressive tumors.