Prostate-specific membrane antigen: Much more than a prostate cancer marker

Prostate cancer continues to be the most common cancer and second leading c ause of cancer-related death among men. The use of markers, particularly se rum-based prostate specific antigen (PSA), has contributed to the rapid ris e in diagnosed cases in the late 1980s and early 1990s, but new diagnostic and possible therapeutic markers are needed and are currently being evaluat ed. One of these, prostate-specific membrane antigen (PSMA), is an approxim ately 100-kDa type II transmembrane protein originally thought to be highly selectively expressed in all types of prostatic tissue, with expression be ing upregulated in androgen-depleted or androgen-independent states. The ra dioimmunoconjugate form of the anti-PSMA monoclonal antibody (mAb) 7E11 is currently being used to diagnose prostate cancer metastasis and recurrence. In addition, Phase I and II trials have started utilizing PSMA in differen t therapeutic ways, with promising results. Recent exciting work has demons trated PSMA expression in endothelial cells of vessels restricted to the tu mor-associated neo-vasculature. This finding expands the possible beneficia l uses of PSMA, as new anti-PSMA mAbs continue to be developed.