By Maxine Fisher, PhD

The epidermal growth factor (EGF) receptor was discovered over 20 years ago and has been studied extensively. EGF receptors poke through the surface of cells like pins in a pincushion. The part of the EGF receptor facing outside the cell (the head of the pin) recognizes and binds to growth signals. The inside-facing part is the “business end” of the EGF receptor‚ which becomes activated by these signals‚ setting off the cellular events that promote cancer growth. In normal cells‚ a limited number of EGF receptors dot the cell surface. In many types of tumor cells (including lung‚ breast‚ prostate‚ ovary‚ gastrointestinal tract‚ and brain)‚ around 100 times the normal number of EGF receptors are found on the cell surface.

A number of anticancer therapy strategies specifically target either the inside- or outside-facing portion of the EGF receptor and prevent it from playing its part in the growth and spread of cancer cells.

A number of drugs targeting the EGF receptor are being developed‚ including ZD1839 (Iressa®) and OSI-774 (Tarceva™)‚ which are taken by mouth. Two other monoclonal antibodies‚ Erbitux and ABX-EGF are also in clinical trials. These drugs have shown promise in the treatment of lung cancer‚ colon cancer‚ and other tumors. Iressa and Tarceva both prevent EGF receptor activation from within the cell. ABX-EGF and Erbitux stop normal growth signals from binding the EGF receptorœs outside-facing part. Either way‚ the stimulation of tumor growth is stopped using these targeted drug therapies.