CD40 is not detected on human prostate cancer cells by immunohistologic techniques

Objectives. The CD40 antigen is expressed by antigen-presenting cells, many kinds of epithelium, and carcinomas. As signaling through CD40 modulates t he differentiation state of CD40-expressing cells, we wanted to investigate whether benign or malignant prostate epithelium expressed CD40. Methods. Twenty-two paraffin-embedded and 10 snap-frozen human prostate tis sue samples were analyzed by immunohistologic methods, using the basal cell -specific markers, high molecular weight cytokeratin (HMWCK) and keratin-14 (K14), and the luminal cell marker, low molecular weight cytokeratin (LMWC K), together with CD40. Fresh prostate tissue was cultured in vitro and ana lyzed by immunocytofluorescence. Results. The pattern of CD40 expression was continuous on basal epithelial cells of normal and hyperplastic prostate glands but discontinuous in gland s that featured prostatic intraepithelial neoplasia. Coexpression of CD40 w ith the basal cell-specific cytokeratins, HMWCK and K14, was confirmed by d ouble labeling. In contrast, glandular epithelial cells in prostate adenoca rcinoma did not express CD40 or these cytokeratins. A luminal cell phenotyp e defined as CAM5.2-positive and HMWCK-negative K14-negative was identified among primary epithelial cells cultured in vitro. Most of the cultured cel ls (more than 99%) were also CD40-negative. Conclusions. Together, our results support the hypothesis that CD40 express ion correlates with the basal cell phenotype, which is lost upon malignant transformation of the prostate, Hence, CD40 may be useful diagnostically to distinguish benign from malignant prostate lesions in biopsy material. URO LOGY 57: 573-578, 2001. (C) 2001, Elsevier Science Inc.