PSA as an Endogenous Anti-Angiogenic Factor in Breast Cancer

Abstract : PSA, which is used as a diagnostic marker for prostate cancer, is also expressed at low levels by female breast tissue. PSA secretion by human breast tumors has been found to be associated with an improved prognosis. In addition, a correlation has been found between breast tumors with a high number and density of microvessels and metatastic disease. This information along with the demonstration that PSA can prevent endothelial cell proliferation and migration led us to hypothesize that PSA might be serving as an anti-angiogenic factor. Determining whether mouse or human tumors transfected to express PSA grew at a different rate than parental tumors tested this. The tumors were mouse tumors expressing PSA were found to grow at a slightly slower rate. The tumors were also examined for the number and density of blood vessels by staining tissue sections for the endothelial cell marker, CD31. Although the morphology of the vessels in the PSA expressing tumors differed from the parental tumors, the tumors did not appear to be markedly more hypoxic. It is possible that the PSA must be activated before it can affect angiogenesis within the growing tumors.