Narrator: This is Science Today. A crucial piece of the pathway leading to colon cancer has been identified. Frank McCormick, director of the University of California, San Francisco's Cancer Research Institute, found that a protein called beta catenin, which has long been associated with colon cancer, directly activates a growth control protein known as cyclin D1.

McCormick: The way it works is, high levels of beta catenin accumulate in colon cancer cells. That protein interacts with a transcription factor and the transcription factor then turns on production of new cyclin D1 message and then that leads to new cyclin D1 protein. So there's the whole chain - right from the regulator to the control point to the target gene.

Narrator: Researchers are hoping to inhibit this process by developing ways to target cyclin D1 and prevent abnormal cell growth.

McCormick: We need to be sure this is a true target of this pathway that's relevant in the disease of cancer - not just in cells in culture. So we need to do more validation that cyclin D1 is really responsible for the disease. So, there's some more experimental work to be done there.

Narrator: For Science Today, I'm Larissa Branin.