Prostate-Specific Membrane Antigen (PSMA) expression in breast cancer and its metastases

Background: Prostate-specific membrane antigen (PSMA) is a type II transmembrane glycoprotein with folate hydrolase and neurocarboxypeptidase activity. PSMA has been shown to be consistently expressed in prostatic carcinoma as well as benign prostatic tissue. In addition, PSMA is selectively expressed in the neovasculator of multiple non-prostatic solid tumours including breast cancers. Inducible PSMA specific expression on angiogenic vasculator suggests that PSMA participates in neovessel growth in developing tumours. Treatment of solid tumours with anti-angiogenic agents has become an established paradigm in cancer therapy. Our study aims at detecting protein expression level of PSMA in breast cancer patients with or without metastases.

Materials and methods: 30 patients who had undergone surgical resection of their breast cancers were identified. Representative formalin-fixed paraffin-embedded tumour blocks from these specimens were obtained from the department of pathology of University of Saarland. Immunohistochemical staining for PSMA and CD31 was performed on parallel representative tumour sections in each case.

Results and conclusion: Our results show that PSMA seems to be expressed in tumour cells and in the neovasculature of breast cancer tumours. This expression is higher in patients with lymph node metastases and even higher in distant metastases. The distant metastases themselves showed the highest expression of PSMA.

These data suggest that PSMA might be involved in the pathogenesis of breast cancer and its metastasis. In addition, PSMA may be an ideal target for diagnostic purposes as well as targeted therapies against metastatic breast cancer. We are going to pursue our study with more cases.