The Mayo Clinic researchers' findings suggest a promising new treatment target at which drug designers can aim new therapies for prostate cancer, as well as a number of other human cancers in which elevated levels of Skp2 have already been documented. These include cancers of the breast, lymphatic leukemia, small cell lung cancer and certain cancers of the mouth and colorectal cancer.

About Prostate Cancer

Prostate cancer is the second most common cause of cancer in men (skin cancer is first) and the second leading cause of cancer death in American men, exceeded only by lung cancer. In 2005, the American Cancer Society estimates 232,000 new cases will be diagnosed. While one in six men will be diagnosed with prostate cancer in his lifetime, only one in 33 will die of it. Because of the widespread disability and death that prostate cancer causes, finding new strategies to develop better treatments is an important public health goal.

Background Biology

The Mayo Clinic researchers wanted to understand the relationship between a group of proteins known as tumor suppressors that belong to the FOXO1 family, and the Skp2 protein. When tumor suppressors fail, the result is abnormal cell growth that can eventually transform healthy cells into cancerous cells. In particular, the Mayo Clinic team wanted to find out what disables FOXO1 tumor suppressor, and how it works -- in hopes of reversing the process to find a new cancer therapy strategy.

The Experiment

The Mayo Clinic research team knew from previous research:

• FOXO1 possesses tumor suppressor functions. Its tumor suppression works two ways: by curbing cell reproduction and by inducing cells to kill themselves -- especially cancer cells.
• Some tumor suppressors lose their effectiveness through a means known as the "ubiquitin pathway." This pathway is a cel
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