Prostate-specific membrane antigen expression in regeneration and repair
Prostate-specific membrane antigen is a type II transmembrane glycoprotein, expressed in benign and neoplastic prostatic tissue as well as endothelial cells of neovasculature from a variety of tumors. The expression of prostate-specific membrane antigen in nonneoplastic neovasculature has not been well studied. Therefore, we studied nonneoplastic reparative and regenerative human tissues, as well as preneoplastic tissue, to determine the presence of prostate-specific membrane antigen-expressing neovasculature. Formalin-fixed paraffin-embedded tissue from keloids, granulation tissue from heart valves and pleura, proliferative and secretory endometrium, and Barrett's mucosa with and without dysplasia were stained for the expression of prostate-specific membrane antigen (3E6). Vessels of proliferative, mid-secretory, and late secretory endometrium were consistently strongly positive for prostate-specific membrane antigen expression in all ten cases of each type (100%). Vessels associated with granulation tissue from pleural peels and heart valves were positive in 10 of 12 cases (83%) and 7 of 10 cases (70%), respectively. Keloids had prostate-specific membrane antigen-expressing endothelial cells in 6 of 15 cases (40%). Prostate-specific membrane antigen was not expressed by vessels associated with Barrett's mucosa with low-grade dysplasia (12 foci), high-grade dysplasia (24 foci), or no dysplasia (18 foci). A variety of nonneoplastic neovasculature expresses prostate-specific membrane antigen, including vessels in proliferative endometrium, granulation tissue, and some scars. This is the first study showing that prostate-specific membrane antigen is expressed in neovasculature from physiologic regenerative and reparative conditions. The folate hydrolase activity of prostate-specific membrane antigen may facilitate vasculogenesis and angiogenesis by increasing local availability of folic acid. These findings will enhance our overall understanding of blood vessel development and will enable us to better understand the effects of anti-prostate-specific membrane antigen therapies, which are already being explored in clinical trials.