Visualizing the Dynamics of EGFR Activity and Antiglioma Therapies In vivo

Abstract

Many altered pathways in cancer cells depend on growth factor receptors. In primary malignant gliomas, the amplification/ alteration of the epidermal growth factor receptor (EGFR) has been shown to play a significant role in enhancing glioma burden. In an effort to dissect the role of EGFR expression in glioma progression in vivo and evaluate targeted therapies for gliomas, we have genetically engineered glioma cells to visualize the dynamics of EGFR and targeted therapies in real time in vivo. Using engineered lentiviral vectors bearing fusions between EGFR and its exon 2 to 7 deleted variant (EGFRvIII) with green fluorescent protein (GFP) and Renilla luciferase (Rluc), we show that there is a direct correlation between EGFR expression and glioma cell proliferation in the initial stages of glioma progression. To monitor and evaluate EGFR-targeted therapies, we have engineered (a) short hairpin RNAs (shRNA) and (b) clinically used monoclonal antibody, cetuximab. Using EGFR-GFP-Rluc/firefly luciferase (Fluc)-DsRed2 glioma model, we show that both shRNAs and cetuximab result in a considerable reduction in glioma cell proliferation in culture and glioma burden in vivo that can be monitored in real time at a cellular resolution. This study serves as a template to follow the role of growth factor receptor expression in tumor progression and to image therapeutic efficacy of targeted therapies in cancer. [Cancer Res 2007;67(15):7335-42]

Bone morphogenetic protein signaling enhances invasion and bone metastasis of breast cancer cells through Smad pathway

“…To study whether Smad-dependent transcriptional pathways were active in the bone metastasis, we used a functional imaging system using a xenograft model. Dual-color bioluminescence imaging is useful for monitoring two molecular events in the same living animal (Arwert et al, 2007). Using this system, we showed that TGF-b and BMP induced the Smaddependent transcriptional pathways to become active in highly bone metastatic MDA-231-D human breast cancer cells that were growing as bone metastases.…”

Epidermal Growth Factor Receptor Expression Identifies Functionally and Molecularly Distinct Tumor-Initiating Cells in Human Glioblastoma Multiforme and Is Required for Gliomagenesis

“…Likewise, EGFR gene amplification is positively correlated with molecularly defined GBM subclasses, characterized by active proliferation and poor prognosis (21). Valuable preclinical information has also been obtained by modulating EGFR expression in standard serum-cultured glioma cell lines (22)(23)(24)(25) and by using these in vitro cultures for testing different therapeutic approaches (26).…”

Modeling the effect of chemotaxis on glioblastoma tumor progression

“…13 The MAPK signaling pathway can be triggered by several different growth factors, including TGFa, that bind to the epidermal growth factor receptor (EGFR), 14 which is amplified (in 40% of cases) or over expressed (in 50% of cases) in gliomas. 15,16 At the tumor level, the progression of the tumor is determined by the spatiotemporal distribution of nutrients and signaling cues. Nutrients and bloodborn growth factors (i.e., TGFa) that trigger the activation of the MAPK signaling pathway are supplied by the vasculature.…”