A cancer is most deadly when it spreads to multiple organs, a process called metastasis. But doctors who find a malignant tumor that seems to be limited to one organ cannot simply cut it out because doing so often means secondary tumors start to grow rapidly. In studies with mice, David Waisman, Ph.D., a professor at the University of Calgary, showed that the p22 protein prevents secondary tumors from growing after the primary tumor is removed. He believes it acts by inhibiting blood vessel growth, which is essential for tumor development.
We might be able to use p22 as a drug itself. Or we could design drugs based on it that would be even more potent, said Waisman. Although several drugs to limit metastasis are already on the market, none are ideal, he added, and p22 offers several advantages.
The molecule is unlikely to cause an immune response because it is a fragment of plasminogen, a protein found in the blood under normal conditions. P22 itself may be found in healthy people, although that possibility is as yet unproven.
Or, doctors could take advantage of the fact that p22 targets only those cells that help tumors grow. If we could figure out a way to tether a cytotoxiccell-killingagent to p22, we would have a very efficient method of stopping tumors, said Waisman. The small size of p22 means it would probably be cleared from the bloodstream quickly, reducing the chance of side effects, he added.
So far, p22 has not been tested on people and any treatments would not be available for years.
Waismans group studied more than 50 mice. The scientists induced cancer in the m
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Contact: Sharon Worthy
s_worthy@acs.org
202-872-4371
American Chemical Society
14-Nov-2001