Epidermal Growth Factor Receptor Signaling and Response of Cancer Cells to Ionizing Radiation

The epidermal growth factor receptor (EGFR) is now recog-nized as an important target for therapeutic interventions in many types of cancer. Because of the prognostic significance of EGFR expression in cancer and the laboratory data that provide direct evidence for aberrant EGFR signaling in cancer cells, this growth factor receptor is being targeted clinically with the use of both antibody- and small molecule-based approaches (1). In this issue of the Journal, Lammering et al. (2) extend their previous observations on the usefulness of targeting the EGFR to improve the therapeutic efficacy of ionizing radiation. Previously, these investigators demonstrated that exposure of EGFR-positive hu-man breast cancer cells to therapeutically relevant doses of ion-izing radiation in vitro could increase the level of activation of the receptor, which resulted in increased mitogen-activated pro-tein (MAP) kinase signaling (3,4). This phenomenon may un