Epidermal Growth Factor Receptor and PTEN Modulate Tissue Factor Expression in Glioblastoma through JunD/Activator Protein-1 Transcriptional Activity

Abstract

Hypoxia and necrosis are fundamental features of glioblastoma (GBM) and their emergence is critical for the rapid biological progression of this fatal tumor; yet, underlying mechanisms are poorly understood. We have suggested that vaso-occlusion following intravascular thrombosis could initiate or propagate hypoxia and necrosis in GBM. Tissue factor (TF), the main cellular initiator of coagulation, is overexpressed in GBMs and likely favors a thrombotic microenvironment. Epidermal growth factor receptor (EGFR) amplification and PTEN loss are two common genetic alterations seen in GBM but not in lower-grade astrocytomas that could be responsible for TF up-regulation. The most frequent EGFR mutation in GBM involves deletion of exons 2 to 7, resulting in the expression of a constitutively active receptor, EGFRvIII. Here, we show that overexpression of EGFR or EGFRvIII in human glioma cells causes increased basal TF expression and that stimulation of EGFR by its ligand, EGF, leads to a marked dose-dependent up-regulation of TF. In all cases, increased TF expression led to accelerated plasma coagulation in vitro. EGFR-mediated TF expression depended most strongly on activator protein-1 (AP-1) transcriptional activity and was associated with c-Jun NH 2 -terminal kinase (JNK) and JunD activation. Restoration of PTEN expression in PTEN-deficient GBM cells diminished EGFR-induced TF expression by inhibiting JunD/AP-1 transcriptional activity. PTEN mediated this effect by antagonizing phosphatidylinositol 3-kinase activity, which in turn attenuated both Akt and JNK activities. These mechanisms are likely at work in vivo, as EGFR expression was highly correlated with TF expression in human high-grade astrocytoma specimens. [Cancer Res 2009;69(6):2540-9]

Oncogenes and the coagulation system – forces that modulate dormant and aggressive states in cancer

“…Consistently with this notion the loss of PTEN tumor suppressor resulting in AKT activation was found to drive TF upregulation and procoagulant phenotype in glioma cells especially under hypoxic conditions [62][63][64]. TF is also upregulated by other oncogenic kinases, such as SRC [65] and MET [66].…”

Modulation of the oncogene-dependent tissue factor expression by kinase suppressor of ras 1

“…In cancer cells, the effects of oncogenic EGFR on TF are mediated through an NFκB dependent mechanism [10], as well as by processes involving AP-1 and c-Jun Nterminal kinase (JNK) activation [12]. Since, the TF promoter also contains functional sites for other transcription factors, including SP1 and Egr-1, other pathways may also be involved downstream of EGFR [26].…”

“…Activated K-ras and members of the ErbB family, such as epidermal growth factor receptor (EGFR) and EGFRvIII all upregulate TF on the surface of cancer cells [10][11][12] and trigger the release of TF-containing microvesicles into the circulation of tumour bearing mice [7,10]. These events contribute to tumour formation and angiogenesis by causing changes in the expression of angiogenic factors [7], or through their impact on tumour initiation [10].…”

Hypoxia triggers a proangiogenic pathway involving cancer cell microvesicles and PAR-2–mediated heparin-binding EGF signaling in endothelial cells

“…Experimental models of tumor development, as well as human cancer materials, link TF to the aggressiveness of several malignancies, including gliomas (5)(6)(7). TF induction in cancer cells may be driven by oncogenetic events, e.g., through EGF receptor (EGFR) and its mutant, EGFRvIII, and inactivation of the tumor suppressor PTEN (6,(8)(9)(10). Other reports have suggested that TF may be triggered by hypoxia through the transcription factor Early growth response gene-1 (11).…”