Cetuximab does not sensitize squamous cell carcinoma cell lines to ionizing radiation in vitro.

CETUXIMAB DOES NOT SENSITIZE SQUAMOUS CELL CARCINOMA CELL LINES TO IONIZING RADIATION IN VITRO. Corey Porter and Peter Kulesza, Department of Anatomic Pathology, University of Alabama at Birmingham, Birmingham, AL 35294. Zhi-Qiang Huang and Jeffery Sellers, Comprehensive Cancer Center. University of Alabama at Birmingham, Birmingham. AL 35294.

Purpose: Epidermal Growth Factor Receptor (EGFR) stimulates proliferation, and been shown to be overexpressed in many cancers. Radiation, the typical treatment for cancer, has been shown to induce phosphorylation of EGFR initiating downstream signaling. The chimeric monoclonal antibody Cetuximab (C225) blocks EGFR signaling, which prompted its use in combination with radiation. The potential of this approach has been shown at UAB by treating patients with squamous head and neck carcinoma with cetuximab, in addition to radiation. This resulted in prolongation of survival on average from 24 months to 56 months on average. However, the question of which individual patients will (or not) benefit from such therapy remains unanswered. Our main objective was to develop an assay which could differentiate on a molecular level between cell lines which can be sensitized to radiation by addition of cetuximab. Methods: The six cancer cell lines A431, Fadu, Sec-1. Hep-2, Hn19, and Ca127 were selected based on similar baseline sensitivity to radiation, but differential response to cetuximab. Cetuximab treatment was initiated 48 hours prior to radiation. Clonogenic assays were utilized to assess response. Results: Cetuximab plus radiation did not show significantly greater inhibition of cell growth than radiation alone. Conclusion: The addition of cetuximab does not seem to sensitize cell lines to radiation in vivo. More tests need to be done to determine why.