1. EGFR regulation under conditions of hypoxia: We have been able to demonstrate that hypoxia induces the expression of EGFRvIII, which significantly improves the clonogenic survival of tumor cells during hypoxia with a strong proliferative response. Thus, EGFRvIII improves the hypoxia tolerance of tumor cells, which indicates a possible selection of EGFRvIII expressing cells under hypoxic conditions. This might contribute to the radioresistant phenotype of hypoxic tumor zones.
2. EGFR responses to RT: The aim is to characterize the role of EGFR and EGFRvIII in the molecular and cellular response to RT. We have found that although EGFRvIII is unresponsive to EGFR ligands, its kinase activity is stimulated by RT. We are analysing the relevant phenotypic changes of different tumour cells following vIII activation, including changes in proliferation, cell survival, and angiogenesis. Our work indicates substantial differences between the EGFR- and EGFRvIII- radiation induced signalling pathways, thus suggesting unique cellular consequences of EGFRvIII expression.
3. EGFR family as biomarkers for RT response in prostate cancer: We are currently analysing the predictive role of EGFR/ EGFRvIII, the MAPK and PI3K pathway in prostate cancer patients treated with RT. For this, we developed a tissue microarray containing paraffin-embedded biopsies of more than hundred prostate cancer patients. The development of phospho-specific antibodies enables us to detect activated signalling molecules. In addition, we will perform hierarchical clustering to investigate an approach to stratifying patients for targeted kinase inhibitor therapy. The detailed investigation of EGFRvIII expression will, in addition, further help us to better understand and to define its role in RT
4. Imaging of EGFR in vitro and in vivo: Recently, we also began to image the EGFR expression with the help of labelled Cetuximab, a specific antibody for EGFR in vitro and in vivo. We found, that Cetuximab also binds to EGFRvIII with as a consequence subsequent internalization. Possible functional consequences for EGFRvIII are being investigated.
Funding
Dutch Cancer Society (KWF); 443.000 Euro; Principle Investigator: Guido Lammering; Title: The role of a variant form of EGFR in radiation responses of human malignant tumors; Period 2006 - 2010
Figure 1: Hypoxia induces the expression of EGFRvIII, but not EGFR. Within 24 hours of anoxia (0% oxygen), the expression levels of EGFRvIII increase by at least 4 fold.
Figure 2: Expression of EGFRvIII increases hypoxia tolerance. Over a period of 96 hours of anoxia, the survival of cells expressing EGFRvIII increases by at least 5 fold compared to controls.
Figure 3: The clinically used antibody against EGFR, called Cetuximab binds to EGFR and EGFRvIII causing internalization, as shown by confocal microscopy of fluorescent-green-labelled Cetuximab. A431 cells express the wild-type EGFR, while U373vIII expresses only the EGFRvIII protein.
Research group
Dr. Guido Lammering, project leader
Co-Principal Investigators
Prof.dr. Bradly G. Wouters
Prof.dr. Philippe Lambin
Co-investigators
Post-doctoral fellows
Dr. Roland Chiu
Dr. Jan Theys
Dr. Marianne Koritzinsky
PhD students
Hugo Aerts
Younan Li
Ludwig Dubois
Technicians
Natasja Lieuwes
Barry Jutten
Students
Ruud Straathoef