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Blood Vessels Enable Tumors

12/22/2003      

MONDAY, Dec. 22 (HealthDayNews) -- Blood vessels near cancer cells appear to help them grow by "telling" them where to go for nutrition and oxygen, say researchers from Duke Comprehensive Cancer Center.

The researchers say blood vessels signal cancer cells, essentially directing them where to get the nourishment they need to grow. According to the study, this can happen even before new blood vessels grow to support the cancer cells.

"We've demonstrated a give-and-take relationship in which cancer cells release signals to nearby blood vessels to stimulate new vessel growth, and in turn, blood vessels release signals that sustain the migrating cancer cells as they try to establish themselves in new tissue," Mark Dewhirst, a cancer biologist at Duke, says in a statement.

Results of the study appear in the Dec. 19 online issue of the Federation of American Societies for Experimental Biology Express.

Scientists had already known that tumors release proteins that cause new blood vessels to grow. What they didn't realize was that cells in the blood vessels were also sending signals to the tumor cells that let the cancer cells know where to grow.

Using cell cultures and animal models, Dewhirst and his colleagues looked at how certain chemical signals affected the growth of cancer cells and blood vessels.

They found that a signal called bFGF didn't affect cancer cells in a test tube. However, that same signal in the human body helps to promote the survival of cancer cells. The researchers further discovered that cancer cells don't even have receptors for bFGF. Without a receptor for this signal, cancer cells can't communicate with it, suggesting this chemical signal must be acting on another part of the body to help sustain cancer growth.

The researchers also did experiments blocking either the protein known as VEGF or a protein receptor called Tie2. Both aid in blood vessel growth. When either wasn't able to express normally, cancer cells couldn't thrive, which suggests this protein and protein receptor aren't just aids in blood vessel growth, but in tumor survival.

"This is a very elegant study," says Dr. Jay Brooks, chief of hematology and oncology at Ochsner Clinic Foundation Hospital in New Orleans. "It shows the relationship of tumor cells and blood vessels and how they interact, and how that promotes the growth and spread of tumors."

Disrupting this process, he says, "will hopefully lead us to ways to prevent cancers from spreading or slow their progress."

He does caution, however, that these experiments are in the very early stages. The goal would be to create a chemical that could disrupt this process, he adds.

In his statement, Dewhirst agrees: "This discovery energizes our efforts to block these signals from being released and to inhibit new blood vessels from forming."

"We're just beginning to see the tip of this in the clinical arena," says Brooks. "It's very complicated trying to figure out ways of disrupting these interactions."

He also notes the current experiments were done in a very controlled atmosphere, unlike what researchers would encounter in the human body.

More information

Visit the National Cancer Institute to learn more about potential causes of cancer and to learn about prevention.

SOURCES: Jay Brooks, M.D., chief, hematology/oncology, Ochsner Clinic Foundation Hospital, New Orleans; Duke Comprehensive Cancer Center press release; Dec. 19, 2003, online issue, Federation of American Societies for Experimental Biology Express

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