PSA and Cancer: A Paradox?

Prostate cancer can be detected early, thanks to digital rectal exams and serum measurements of prostate-specific antigen (PSA). Although the role of PSA in cancer is poorly understood, high PSA levels are usually interpreted as bad news about cancer progression. But now scientists at EntreMed, a biotechnology company in Rockville, Md., offer a more optimistic interpretation--one that may explain some paradoxical observations about PSA and cancer.

Tumor-secreted proteins called tumor angiogenesis factors cause blood vessels from surrounding tissues to grow into tumors. This process, tumor angiogenesis, gives tumors blood needed for accelerated growth. EntreMed has found that PSA inhibits tumor angiogenesis.¹ This may explain in part why prostate cancer usually progresses slowly. The discovery also implies that PSA may have a future as a cancer drug.

PSA is not specific to the prostate or to men. EntreMed found a hint that PSA had antiangiogenesis activity in a report^2...