A protein called PHD2 may play a role in the growth of tumors, US researchers said in a new study.

PHD2, which regulates blood vessel growth, is often found at lower-than-normal levels in tumors, said researchers at Stanford University School of Medicine in Californiasay.

The researchers came to the conclusion after analyzing levels of the protein in tumor samples and healthy tissue, according to the study published in the June issue of Cancer Cell.

The finding may help scientists find ways to slow tumor growth.

When the expression of PHD2 was blocked, human cancer cells grew more quickly when implanted into mice and there was an increase in the number of blood vessels feeding the tumors, the researchers said.

To grow and spread, tumors require a good supply of blood.

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," said Amato Giaccia, a professor of radiation oncology.

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

(Xinhua News Agency June 6, 2009)