Expression of proinflammatory cytokine interleukin-6 in tissue samples of human prostate obtained by needle biopsy

Interleukin-6 (IL-6) has been associated with the development of prostate cancer. The aim of the study was to clarify whether IL-6 expression in prostate tissue could be a useful marker in differentiation of prostate diseases in small foci by pathologist visual scoring. Archival paraffin-embedded specimens of benign prostate hyperplasia (BPH), high-grade prostatic intraepithelial neoplasia (PIN), prostatitis and prostate adenocarcinoma were studied by immunohistochemistry with a mouse monoclonal antibody IL-6 using the streptavidin-biotin method. Significantly, lower IL-6 immunoreactivity was observed in normal epithelial cells (p=0.000) and basal cells (p=0.000) in the samples of prostate adenocarcinoma in comparison to the samples with BPH, PIN and prostatitis. There was no significant difference in IL-6 expression in malignant and premalignant cells (p=0.814) as well as in stromal cells among the four diagnoses (p=0.22). IL-6 was expressed in normal epithelial cells, premalignant epithelial cells and malignant epithelial cells as well as in stromal cells. However, in our research IL-6 was of limited utility as a single marker for differential diagnosis of the prostate diseases in small foci needle biopsy by pathologist visual scoring. The standardization of immunohistochemical (IHC) staining protocol for IL-6 is required to determine IL-6 expression in order to avoid possible misinterpretation of the IHC results.