June 5 (HealthDay News) -- A protein called PHD2 that regulates blood vessel growth is often found at lower-than-normal levels in tumors, say researchers who analyzed levels of the protein in tumor samples and healthy tissue.

When they blocked the expression of PHD2, researchers at Stanford University School of Medicine in California found that human cancer cells grew more quickly when implanted into mice and there was an increase in the number of blood vessels feeding the tumors. To grow and spread, tumors require a good supply of blood, the study authors noted in a Stanford news release.

Further investigation revealed that blocking PHD2 expression increased levels of two other proteins -- IL-8 and angiogenin -- that play an important role in blood vessel formation. Blocking the activity of these proteins may slow tumor growth, the researchers said.

"Prior to this study, it was unclear which of the many proteins involved in vessel growth, or angiogenesis, should be targeted. But now we know they play a predominant role in tumor growth," Amato Giaccia, a professor of radiation oncology, said in the release.

The findings are published in the June 2 issue of Cancer Cell.

In the next phase of their research, Giaccia and colleagues will study whether mice that lack PHD2 expression develop more aggressive tumors, and whether blocking IL-8 or angiogenin slows tumor growth.

SOURCE: Stanford University School of Medicine, news release, June 1, 2009