Prostate-specific membrane
antigen (PSMA), a type II transmembrane metallo-
peptidase highly overexpressed in
prostate cancer cells, has been studied as a targeting molecule in
prostate cancer. Recently, PSMA has also been found to be expressed in the neovasculature of multiple nonprostatic solid
tumors. Because of its unique expression pattern limited to
tumor-associated endothelial cells, PSMA may also be an interesting molecule for vascular targeting. In this study, PSMA expression was determined by immunohistochemistry in 119 cases of primary gastric
adenocarcinoma, 130 cases of primary colorectal
adenocarcinoma, and 24
metastasis of colorectal
adenocarcinoma. Expression data were correlated with clinicopathologic information. PSMA expression was detected in
tumor-associated neovasculature of 79 (66%) of 119 gastric and 110 (85%) of 130
colorectal carcinomas. Furthermore, the neovasculatures of 16 (84%) of 19 liver and 4 (80%) of 5 nodal
metastases from
colorectal carcinomas were prostate-specific membrane
antigen positive. There was a trend for high-grade
tumors to higher PSMA expression (Spearman r = 0.18, P = .046) in
colorectal cancers. No association between PSMA expression and overall- or disease-free survival was observed in gastric or
colorectal cancers. This study provides the first in-depth look at PSMA expression in gastric and
colorectal cancer. Because of its highly
tumor-restricted expression and its accessibility to targeted
therapy, PSMA represents a promising therapeutic and diagnostic target in colorectal and
gastric cancer.