Abstract
Tissue factor (TF) is a transmembrane glycoprotein that initiates blood coagulation when complexed with factor VIIa (FVIIa). TF is constitutively expressed by a variety of tumor cells. Recently, TF has been shown to induce cellular signaling and promote tumor growth, angiogenesis, and metastasis. We showed previously that formation of TF-FVIIa-Factor Xa (FXa) complex induces cellular signaling in the Adr-MCF-7 cell line, a multidrug-resistant subline of the human breast cancer cell line, MCF-7 (
Jiang et al. J. Thromb Haemost 2: 2004; 93–101
). This cell line has high endogenous expression of TF. Treatment of the Adr-MCF-7 cells with the combination of FVIIa (10 nM) and FX (150 nM) induces phosphorylation of p44/42 mitogen-activated protein kinase (MAPK) and protein kinase B (PKB), whereas no increase in the basal level of phosphorylation of these proteins occurs with treatment of the cells with FVIIa (10 nM) alone. In the present study, we investigated whether TF-FVIIa-induced signaling might alter apoptosis in human breast cancer cells. Apoptosis of the Adr-MCF-7 cells was induced by serum starvation for 5–7 days. Treatment of the cells with the combination of FVIIa (10 nM) and FX (150 nM), reduced apoptosis of the cells by nearly 50% compared with untreated, control cells using an ELISA that detects histone-DNA fragments. In contrast, FVIIa (10 nM) alone did not significantly prevent apoptosis. Pre-treatment of the Adr-MCF-7 cells with hirudin did not inhibit the anti-apoptotic effect of the combination of FVIIa and FX, whereas this effect could be completely blocked by either U0126 (10 μM), which inhibits p44/42 MAPK phosphorylation, or LY294002 (50 μM), which inhibits PKB phosphorylation. In addition, treatment of the Adr-MCF cells with the combination of FVIIa and FX led to a 50% increase in the level of the anti-apoptotic protein, survivin, compared with untreated cells by Western blot analysis. Results from this study indicate that formation of TF-FVIIa-FXa complex prevents apoptosis of breast cancer cells by a thrombin-independent pathway. Moreover, the anti-apoptotic effect of this signaling pathway involves both phosphorylation of p44/42 MAPK and PKB and might be mediated in part by an increase in cell survivin levels.Author notes
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2005, The American Society of Hematology
2004
