Researchers at the University of Pennsylvania School of Medicine have determined the precise molecular details of how Erbitux, a recently approved colorectal cancer drug, binds to its target on cancer cells. Knowing this chemical configuration will lead to better drug design for this family of cancer medications.
Colorectal cancer is one of the most frequently diagnosed cancers in men and women, as well as the second-leading cause of cancer-related death, according to the Centers for Disease Control and Prevention. Erbitux works by binding to a protein on the surface of cancer cells, thereby halting excessive cell growth that leads to tumors. Kate Ferguson, PhD, Assistant Professor of Physiology, and colleagues, describe their findings in the April cover article of Cancer Cell.
“By having determined the structure of Erbitux bound to its cellular target receptor, we get new insight into how the drug blocks the receptor’s cell growth-promoting activities, and can use this to guide future drug design,” says Ferguson.
As is characteristic of many epithelial cancers - such as cancers of the head and neck, breast, ovary, lung, and pancreas - the surface of cancer cells possess abnormally high levels of epidermal growth factor receptor (EGFR), the protein that interacts with Erbitux. (Click on thumbnail to view full-size image). These receptors are made up of three parts: one outside the cell; another passing through the cell membrane; and the third inside the cell. In a cancer cell, an extracellular hormone binds to the outer piece of EGFR, and causes the inside part to kick off a series of reactions that signal the cancerous cell to replicate and divide.
Ferguson and colleagues determined that Erbitux works to halt cell proliferation by blocking EGFR’s molecular doorway, disallowing hormones to bind and signal tumor growth. X-ray crystallography provided a snapshot of the interaction between Erbitux and the extracellular component of the cancer cell’s receptors.