Natural protein helps prevent cancers from spreading to other organs

November 14, 2001

A small protein released by cancer cells can inhibit the growth of secondary tumors in mice and could be used to design new types of anti-cancer drugs, according to Canadian researchers. The finding was published in the Oct. 30 edition of Biochemistry, a peer-reviewed journal of the American Chemical Society, the world's largest scientific society.

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 cytotoxic"--cell-killing--"agent 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.

Waisman's group studied more than 50 mice. The scientists induced cancer in the mice's necks, then removed the tumors two weeks later, using the methods a surgeon would use to remove a tumor from a human. Half the mice then received daily p22 injections; half received a placebo. Two weeks later, the scientists weighed the mice's lungs. The placebo group's lungs weighed more than three times as much as the p22 group's. The extra weight was due to cancerous growths, they said.

The researchers showed that p22 is a natural compound released by cancerous cells themselves to control blood vessel growth. Cancer cells must force new blood vessels to grow so they can obtain the nutrients necessary to continue rapidly dividing. Without a direct blood supply, a colony of cancerous cells cannot develop into a deadly tumor.

The p22 protein kills the cells that line the walls of growing blood vessels, thereby preventing new vessels from developing. Waisman hypothesizes that p22 is part of a sensitive growth control system. "If a tumor releases compounds to both promote and inhibit endothelial cell growth, it has much more control over blood vessel growth than if it released only growth factors alone," he explained.

Waisman believes that p22's small size means scientists will be able to determine its molecular structure. "With a small molecule, we can see it, see where it goes. Does it bind to a receptor? How can it specifically attack only capillary endothelial cells and no others? The real excitement is that we're getting really close to figuring out how this works," said Waisman.
The research was funded by the Canadian Institutes of Health Research.

The online version of the research paper cited above was initially published Oct. 13 on the journal's Web site. Journalists can arrange access to this site by sending an e-mail to or calling the contact person for this release.

David M. Waisman, Ph.D., is a professor in the departments of biochemistry & molecular biology, and oncology at the University of Calgary.

American Chemical Society

Related Cancer Articles from Brightsurf:

New blood cancer treatment works by selectively interfering with cancer cell signalling
University of Alberta scientists have identified the mechanism of action behind a new type of precision cancer drug for blood cancers that is set for human trials, according to research published in Nature Communications.

UCI researchers uncover cancer cell vulnerabilities; may lead to better cancer therapies
A new University of California, Irvine-led study reveals a protein responsible for genetic changes resulting in a variety of cancers, may also be the key to more effective, targeted cancer therapy.

Breast cancer treatment costs highest among young women with metastic cancer
In a fight for their lives, young women, age 18-44, spend double the amount of older women to survive metastatic breast cancer, according to a large statewide study by the University of North Carolina at Chapel Hill.

Cancer mortality continues steady decline, driven by progress against lung cancer
The cancer death rate declined by 29% from 1991 to 2017, including a 2.2% drop from 2016 to 2017, the largest single-year drop in cancer mortality ever reported.

Stress in cervical cancer patients associated with higher risk of cancer-specific mortality
Psychological stress was associated with a higher risk of cancer-specific mortality in women diagnosed with cervical cancer.

Cancer-sniffing dogs 97% accurate in identifying lung cancer, according to study in JAOA
The next step will be to further fractionate the samples based on chemical and physical properties, presenting them back to the dogs until the specific biomarkers for each cancer are identified.

Moffitt Cancer Center researchers identify one way T cell function may fail in cancer
Moffitt Cancer Center researchers have discovered a mechanism by which one type of immune cell, CD8+ T cells, can become dysfunctional, impeding its ability to seek and kill cancer cells.

More cancer survivors, fewer cancer specialists point to challenge in meeting care needs
An aging population, a growing number of cancer survivors, and a projected shortage of cancer care providers will result in a challenge in delivering the care for cancer survivors in the United States if systemic changes are not made.

New cancer vaccine platform a potential tool for efficacious targeted cancer therapy
Researchers at the University of Helsinki have discovered a solution in the form of a cancer vaccine platform for improving the efficacy of oncolytic viruses used in cancer treatment.

American Cancer Society outlines blueprint for cancer control in the 21st century
The American Cancer Society is outlining its vision for cancer control in the decades ahead in a series of articles that forms the basis of a national cancer control plan.

Read More: Cancer News and Cancer Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to