The expression of thrombospondin‐1 in benign prostatic hyperplasia and prostatic intraepithelial neoplasia is decreased in prostate cancer

OBJECTIVE To evaluate the immunohistochemical expression of thrombospondin (TSP), a potent inhibitor of angiogenesis, in human benign prostatic hyperplasia (BPH) and prostate cancer. MATERIALS AND METHODS The expression of TSP‐1, TSP‐2 and CD36 receptor was assessed in 73 tissue specimens using immunohistochemistry; specimens were from 32 patients with BPH, seven with prostatic intraepithelial neoplasia (PIN) and 34 with cancer. RESULTS Immunohistochemistry showed that all 39 patients with BPH and PIN had TSP‐1‐positive glands. In contrast, none of the 34 patients with cancer had positive TSP‐1 staining in the cancer tissue. All 73 patients were positive for TSP receptor CD36 and negative for TSP‐2. CONCLUSIONS TSP is expressed in BPH, down‐regulated in PIN and absent in prostate cancer tissue. This may indicate that TSP is important in prostate cancer progression. Further studies are needed to understand the significance of these findings for the malignant transformation of the prostate gland.