IL-8 mRNA expression by in situ hybridisation in human pituitary adenomas

Several cytokines have been shown to be expressed in normal and adenomatous pituitary tissue. Recently, interleukin-8 (IL-8) mRNA was identified by re verse transcription (RT)-PCR in each of a series of 17 pituitary tumours ex amined. We have investigated further the presence of IL-8 mRNA, using ii? s itu hybridisation in two normal human anterior pituitary specimens and 25 h uman pituitary adenomas. IL-8 mRNA was not identified in either of the two normal pituitary specimens. Only three of the 25 adenomas were positive for IL-8 mRNA. In these three tumours, which included two null cell adenomas a nd one gonadotrophinoma, the majority of tumour cells (>90%) were positive for IL-8 mRNA. The remaining 22 adenomas were completely negative. There wa s no difference in tumour size or type between the IL-8 positive and the IL -8 negative tumours, and immunocytochemistry for von Willebrandt factor sho wed that the two groups were also similar in their degree of vascularisatio n. In conclusion, IL-8 mRNA was found in 12% of pituitary adenomas studied and was histologically identified within the tumour cells. In situ hybridisati on is a more appropriate technique for assessing cytokine mRNA production b y human pituitary tumours because RT-PCR may be too sensitive, identifying very small, possibly pathologically insignificant, quantities of mRNA that could be produced by supporting cells such as fibroblasts, endothelial cell s or macrophages.