Immunohistochemical localization of interleukin-6 and its receptor in benign, premalignant and malignant prostate tissue

Interleukin-6 (IL-6) is a pleiotropic cytokine that interacts with its rece ptor in prostate cells, thus regulating proliferative response and differen tiation. It also activates the human androgen receptor in prostate cancer c ell lines. In order to assess the significance of these findings in vivo, t he expression of key elements of the IL-6 signalling pathway, IL-6 and its receptor, was investigated in tissue samples obtained on radical prostatect omy from prostate cancer patients, IL-6 immunohistochemistry was performed on 17 frozen prostate cancer specimens. IL-6 receptor immunostaining was ev aluated in 21 paraffin-embedded prostate tumour specimens. In both groups, adjacent areas of high-grade prostatic intraepithelial neoplasia and benign tissue were also investigated. In benign prostatic epithelium, IL-6 was lo calized predominantly in basal cells, whereas in prostate cancer tissues mo re IL-6-positive glandular cells were identified. No IL-6 expression was de tected in stromal cells on immunohistochemistry, although IL-6 protein was measured in the supernatants obtained from cultured stromal cells by ELISA. IL-6 receptor was expressed in benign prostatic tissue in both epithelial and stromal cells. Furthermore, IL-6 receptor expression was observed in al l tumour specimens investigated and the majority of Gleason patterns analys ed had more than 50% of cells showing a positive reaction. IL-6 and IL-6 re ceptor expression patterns in high-grade prostatic intraepithelial neoplasi a lesions were similar to those observed in tumour tissues, Taken together, the results of the present study imply that there are paracrine and autocr ine IL-6 loops in benign and neoplastic prostate. Copyright (C) 2000 John W iley & Sons, Ltd.