Marker of aggressive prostate cancer identified

Researchers at the Mayo Clinic in Rochester, Minnesota, have identified a protein “biomarker” of aggressive prostate cancer. The protein, known as B7-H3, plays a role in the functioning of the immune system.

Based on their studies to date, Dr. Timothy J. Roth and associates believe that B7-H3 is a promising marker that may eventually help doctors better diagnose prostate cancer and assess prognosis. It may also represent a good target for new prostate cancer drugs.

In the journal Cancer Research, Roth and colleagues report that normal prostate cells express low levels of B7-H3, but levels of the protein are increased in prostate cancer cells, particularly prostate cancer cells with aggressive features.

Roth’s team tested preserved prostate tissue from 338 men with prostate cancer who had their prostates removed between 1995 and 1998. All of the prostate tumors had evidence of B7-H3. B7-H3 was also found in normal prostate tissue, but in lower amounts than that seen in tumor tissue.

B7-H3 expression was “typically low” within normal prostate glands, the team reports, but was aberrantly expressed in prostate tumors.

The level of B7-H3 was significantly associated with larger tumors and tumors that had spread beyond the prostate, the authors report. In analyses adjusted for factors that might influence prognosis, B7-H3 remained a statistically significant predictor of prostate cancer progression.

During follow up, patients with high levels of B7-H3 were significantly more likely to progress than patients with low levels of B7-H3 in their tumors. Furthermore, survival at 5 years after surgery without tumor progression was roughly 92 percent in patients with low levels of B7-H3, 86 percent in those with moderate levels and 55 percent in those with high B7-H3 levels.

SOURCE: Cancer Research, August 15, 2007.

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