Jouriial zyxwvutsrqpo oj Neuroeizdocvinolog, 1995, Vol. 7, 467-474 zyxwvutsr S-I zyxwv 00 Antigen-Positive Folliculostellate Cells are not the Source of IL-6 Gene Expression in Human Pituitary Adenomas Yoichi Ueta", Andrew Levy, Hardial S. Chowdrey? and Stafford L. Lightman Department of Medicine, University of Bristol, Bristol Royal Infirmary, Lower Maudlin Street, Bristol BS2 8HW, UK Key words: interleukin-6, human pituitary adenomas Abstract We have investigated the expression of IL-6 in a random selection of 27 human pituitary adenomas, comprising 8 somatotroph, 5 corticotroph, 3 mammotroph and 11 endocrinologically inactive adenomas, using a 35S-labelled 1.1 kb riboprobe complementary to human IL-6. Positive and negative IL-6 transcript controls were generated from the IL-6-secreting human bladder carcinoma cell line T24/83. Tissue from a malignant melanoma was used as a positive S-1 00 immunocytochemical control tissue. Of the 27 human pituitary adenomas examined by zyxwvutsrqpon in situ hybridization, 7 zyxwvutsr (26%) contained IL-6 transcripts: these were 3 of 5 corticotroph adenomas, 2 of 8 somatotrophinomas and 2 of 11 endocrinologically inactive adenomas. In each case, IL-6 transcript-positive cells constituted less than 1 of the total pituitary tissue mass examined. Alternate wax embedded 3 pm thick sections from 5 of the 7 IL-6 transcript positive tumours were examined immunocytochemically for S-1 00 antigen, or by in situ hybridization for IL-6 transcripts. lmmunocytochemistry for S-1 00 antigen was completely negative in 3 of the 5 tumours and in the remaining 2, there was no evidence of IL-6 transcripts and S-1 00 antigen co-localization in any of the sections examined. This suggests that in pituitary adenomas, cells other than classical folliculostellate cells are responsible for IL-6 production. Interleukin zyxwvutsrq 6 (IL-6) is thought to be an important cytokine in the endocrine system (1, 2) and the release of IL-6 from rat anterior pituitary cells (3) and cultured human pituitary adenoma cells (4) has been widely reported. Several recent studies have also demonstrated that human pituitary adenomas sometimes contain IL-6 transcripts (5, 6) or IL-6 protein (7). Although folliculostellate cells are thought to be the major source of IL-6 synthesis in normal rat (8) and mouse (9) anterior pituitary, the identity of cells expressing IL-6 in human pituitary adenomas has not been clarified. We therefore investigated the expression of IL-6 in human pituitary adenomas and attempted to correlate IL-6 expression with S-100 immunostaining, as the latter is a marker of folliculostellate cells. Positive and negative IL-6 transcript- containing controls were generated from the IL-6 secreting human bladder carcinoma cell line T24/83 (10). Results Pituitary adenomas were classified clinically as somatotroph, corticotroph, mammotroph or endocrinologically inactive. The clinical diagnoses were confirmed by routine immunohistochem- istry and by i17 situ hybridization for growth hormone (GH), prolactin (PRL) and proopiomelanocortin (POMC) (Table 1 ). Tsanscriptionai controls Five days after the T24/83 cells were plated on gelatin-coated slides, IL-6 transcripts were detected under control condition using the antisense. but not the sense IL-6 riboprobe (Fig. I). Pre-incubation in bacterial lipopolysaccharide rapidly induced IL-6 expression in T24/83 cells within 30 min, reaching a peak at 60 min. Once again, no hybridization was detected with the sense probe. Induction of IL-6 expression was completely blocked by preincubation of cells with the transcription blocker, actinomycin D (5 pg/ml) (Fig. 2). E,xpres.cion of' TL-6 17y hurnan pituitary adenomas Of the 27 human pituitary adenomas examined, 7 contained scattered cells or cell clusters expressing IL-6. These were 3 of 5 corticotroph, 2 of S somatotroph, and 2 of 11 endocrinologically inactive adenomas. In 2 adenomas, a relatively sparse subpopul- ation of IL-6 transcript-positive cells were scattered throughout (Figs 3 and 4). Correspondci?c~r to: Yoichi Ueta, Department of Physiology. School of Medicine, University of Occupational and Environmental Health. Iscigaoka 1- 1. Yahatanishi-ku, Kitakyushu, 807 Japan. *Prc.sent udc/re.w: Department of Physiology, School of Medicine. Univcrsity of Occupational and Environmental Health. Iseigaoka 1 -I, Yahatanishi- ku. Kitakyushu. 807 Japan. ?Prc,.~ent addrc.s.s: School of Biological and Chcmical Sciences, University of Greenwich. Woolwich, London SEI 8 6TE. UK. C 1995 Blackwcll Sciencc Ltd