Now, a new study by scientists at the University of Michigan Comprehensive Cancer Center reveals one crucial key to that deadly process.

In the June 18 issue of the Journal of the National Cancer Institute, the U-M team reports strong evidence that a protein called RKIP, for Raf kinase inhibitor protein, governs the ability of prostate cancer cells to leave their original location and enter nearby blood vessels which then act as superhighways to the rest of the body.

The findings, made using a broad range of techniques, show that RKIP is vital to this process, called vascular invasion. Such invasion is the first in a cascade of events leading to metastasis. Tumors that produce a normal amount of RKIP appear unable to make the jump to the vascular system, the researchers report. But if a tumor cell lacks RKIP, metastasis can take place.

"The gene encoding RKIP appears to be a novel metastasis suppressor gene, involved in blocking the cell-signaling processes that allow cancer cells to enter the bloodstream," says senior author Evan Keller, DVM, Ph.D., an associate professor of Comparative Medicine and Pathology at the U-M Medical School. "If there is RKIP expression in a tumor, this first important step appears to be less likely."

Because the researchers made part of their discovery using tissue samples from patients treated for metastatic prostate cancer at the U-M Cancer Center, they believe the laboratory findings are especially relevant to "real life" cases of cancer.

They also feel that RKIP could be involved in other forms of cancer. "Understanding the basic biology means we may eventually be able to help patients with
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Contact: Kara Gavin
kegavin@umich.edu
734-764-2220
University of Michigan Health System
17-Jun-2003