ErbB oncogenes drive the progression of several human cancers. Our study shows that in human carcinoma (A431) and glioma (U373) cells, the oncogenic forms of epidermal growth factor receptor (EGFR; including EGFRvIII) trigger the up-regulation of tissue factor (TF), the transmembrane protein responsible for initiating blood coagulation and signaling through interaction with coagulation factor VIIa. We show that A431 cancer cells in culture exhibit a uniform TF expression profile; however, these same cells in vivo exhibit a heterogeneous TF expression and show signs of E-cadherin inactivation, which is coupled with multilineage (epithelial and mesenchymal) differentiation. Blockade of E-cadherin in vitro, leads to the acquisition of spindle morphology and de novo expression of vimentin, features consistent with epithelial-to-mesenchymal transition. These changes were associated with an increase in EGFR-dependent TF expression, and with enhanced stimulation of vascular endothelial growth factor production, particularly following cancer cell treatment with coagulation factor VIIa. In vivo, cells undergoing epithelial-to-mesenchymal transition exhibited an increased metastatic potential. Furthermore, injections of the TF-blocking antibody (CNTO 859) delayed the initiation of A431 tumors in immunodeficient mice, and reduced tumor growth, vascularization, and vascular endothelial growth factor expression. Collectively, our data suggest that TF is regulated by both oncogenic and differentiation pathways, and that it functions in tumor initiation, tumor growth, angiogenesis, and metastasis. Thus, TF could serve as a therapeutic target in EGFR-dependent malignancies.
Background: Cross-talk of oncogenic and differentiation pathways in cancer coagulopathy is poorly understood. Results: EGFR activation and blockade of E-cadherin in cancer cell lines induce mesenchymal phenotype and tissue factor (TF) shedding, as exosomes, capable of transferring procoagulant activity to endothelium. Conclusion: Mesenchymal and procoagulant phenotypes are linked in cancer. Significance: Epithelial-to-mesenchymal transition (EMT) may influence tumor-vascular interactions via TF-containing exosomes.
Tissue factor (TF), the primary cellular initiator of blood coagulation, is also involved in cancer-related processes such as hypercoagulability (Trousseau syndrome), tumor growth, angiogenesis, and metastasis. Indeed, elevated TF expression by cancer cells and their associated endothelial cells has been reported frequently. Oncogenic events in cancer cells (e.g., expression of mutant K- ras, EGFR, PTEN or p53) lead to an increase in TF levels and activity, and thereby promote tumor aggressiveness, angiogenesis, and hypercoagulability. Like TF, thrombin receptor (protease-activated receptor-1) is also upregulated in cancer cells expressing oncogenic K -ras. Pharmacological antagonists of some of these transforming genes (e.g., epidermal growth factor receptor inhibitors) could diminish TF expression, both locally and systemically, and hence these targeted agents could be viewed as potential indirect and cancer-specific anticoagulants, in addition to their direct antitumor effects. We postulate that levels of circulating TF may be useful in monitoring the biological activity of these agents. Although TF is essential for vascular development, its expression by tumor-associated endothelium appears to play a subtle and seemingly dispensable role. Thus, TF is a pivotal element of the tumor-vascular interface, is involved in many cancer-related processes, and may well constitute a promising new target for anticancer combination therapies in some disease settings.
Significance Our study shows that the clotting protein tissue factor (TF) controls the state of tumor dormancy and does so in conjunction with recruitment of inflammatory cells and blood vessels. We show that indolent glioma cells remain harmless in mice unless rendered TF positive. Our work also demonstrates the ability of TF to indirectly influence the DNA of cancer cells by facilitating gene mutations and silencing. This ability is important because injury, cardiovascular disease, or other conditions may activate the clotting system and contribute to the awakening of occult cancer cells. This understanding also may suggest a prophylactic use of blood thinners in cases where dormant cancer cells and clotting are suspected to coexist (e.g., after surgery).
Objective-The role of host-derived tissue factor (TF) in tumor growth, angiogenesis, and metastasis has hitherto been unclear and was investigated in this study. Methods and Results-We compared tumor growth, vascularity, and responses to cyclophosphamide (CTX) of tumors in wild-type (wt) mice, or in animals with TF levels reduced by 99% (low-TF mice). Global growth rate of 3 different types of transplantable tumors (LLC, B16F1, and ES teratoma) or metastasis were unchanged in low-TF mice. However, several unexpected tumor/context-specific alterations were observed in these mice, including: (1) reduced tumor blood vessel size in B16F1 tumors; (2) larger spleen size and greater tolerance to CTX toxicity in the LLC model; (3) aborted tumor growth after inoculation of TF-deficient tumor cells (ES TF Ϫ/Ϫ ) in low-TF mice. TF-deficient tumor cells grew readily in mice with normal TF levels and attracted exclusively host-related blood vessels (without vasculogenic mimicry). We postulate that this complementarity may result from tumor-vascular transfer of TF-containing microvesicles, as we observed such transfer using human cancer cells (A431) and mouse endothelial cells, both in vitro and in vivo.
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