Cancer Cells Lack Protein that Blocks Formation of New Blood Vessels

Cancer researchers have identified a protein (PHD2) that can slow or prevent tumor growth by inhibiting formation of new blood vessels. However, cancer cells have much lower concentrations of this protein than do neighboring normal tissues.

Investigators from Stanford University (Palo Alto, CA; USA) measured PHD2 levels in samples of human breast and colon cancers and compared them with surrounding tissue. They found that in many cancers the tumors had lower-than-normal levels of PHD2. The investigators then inhibited the expression of PHD2 in a variety of human cancer cells, transplanted those cells into mice with compromised immune systems, and examined the resulting tumors.

Results published in the June 2, 2009, issue of the journal Cancer Cell revealed that tumors arising from cells in which PHD2 expression had been blocked grew more quickly, and were more highly vascularized than the unmodified control cells. Molecular analysis showed that blocking PHD2 expression increased the levels of two proteins involved in blood vessel formation: interleukin-8 (IL-8) and angiogenin.

"Prior to this study it was unclear which of the many proteins involved in vessel growth, or angiogenesis, should be targeted,” said senior author Dr. Amato Giaccia, professor of radiation oncology at Stanford University. "But now we know they play a predominant role in tumor growth. PHD2 appears to be acting as a tumor suppressor by negatively controlling blood vessel formation.”

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