Prostate cancer (PCa) is the most prevalent cancer in men. Hyperactive STAT3 is thought to be oncogenic in PCa. However, targeting of the IL-6/STAT3 axis in PCa patients has failed to provide therapeutic benefit. Here we show that genetic inactivation of Stat3 or IL-6 signalling in a Pten-deficient PCa mouse model accelerates cancer progression leading to metastasis. Mechanistically, we identify p19^ARF as a direct Stat3 target. Loss of Stat3 signalling disrupts the ARF–Mdm2–p53 tumour suppressor axis bypassing senescence. Strikingly, we also identify STAT3 and CDKN2A mutations in primary human PCa. STAT3 and CDKN2A deletions co-occurred with high frequency in PCa metastases. In accordance, loss of STAT3 and p14^ARF expression in patient tumours correlates with increased risk of disease recurrence and metastatic PCa. Thus, STAT3 and ARF may be prognostic markers to stratify high from low risk PCa patients. Our findings challenge the current discussion on therapeutic benefit or risk of IL-6/STAT3 inhibition.

Background Nephrogenic adenomas are benign, tumor-like lesions within the urothelial mucosa of the urinary tract that are not uncommon in renal-transplant recipients. We investigated the origin of nephrogenic adenomas in renal-transplant recipients. Methods Tissue sections were analyzed by fluorescence in situ hybridization with the use of probes for the X and Y chromosomes, by immunohistochemical methods with the use of antibodies to renal tubular antigens, and by lectin histochemical methods. Forty-six nephrogenic adenomas from 29 patients were analyzed. Results All nephrogenic adenomas in 14 female recipients of transplants from male donors and 10 male recipients of transplants from female donors showed the same sex-chromosome status as the donor kidney, but not the same sex-chromosome status as the recipient's surrounding bladder tissue. The nephrogenic adenomas from all 6 female recipients of transplants from female donors showed female chromosomes, and those from the 16 male recipients of transplants from male donors showed male chromosomes. The presence of aquaporin 1, PAX2, and lectin-binding capacity for peanut agglutinin, Lotus tetragonolobus agglutinin, and Sophora japonica agglutinin in nephrogenic adenomas indicated an origin from renal tubular cells. Conclusions Nephrogenic adenomas in renal-transplant recipients are derived from tubular cells of the renal transplants and are not metaplastic proliferations of the recipient's bladder urothelium.

Neuropathologists use anti-glial fibrillary acidic protein (GFAP) antibodies as specific markers for glial cells, and neurobiologists use GFAP for targeting transgenes to glial cells. Since GFAP has also been detected in non-glial cells, we systematically analyzed GFAP expression in human and murine non-CNS tissues using a panel of anti-GFAP antibodies. In human tissues we confirm previously observed GFAP expression in Schwann cells, myoepithelial cells, and chondrocytes, and show for the first time GFAP expression in fibroblasts of epiglottic and auricular perichondrium, ligamentum flavum, and cardiac valves. In mice we show GFAP expression in Schwann cells, bone marrow stromal cells, chondrocytes, and in fibroblasts of dura mater, skull and spinal perichondrium, and periosteum, connective stroma of oral cavity, dental pulp, and cardiac valves. Anti-GFAP immunoblotting of human non-CNS tissues reveals protein bands with a molecular mass ranging between ≈35 and ≈42 kDa. In GFAP-v-src transgenic mice, whose oncogenic v-src transgene transforms GFAP expressing cells, non-CNS tumors originate from fibroblasts. We conclude that human and murine fibroblasts can express GFAP in vivo. The somatic distribution of GFAP expressing fibroblasts indicates origin from the neural crest. Development of non-CNS tumors from fibroblasts in GFAP-v-src mice functionally confirms GFAP expression in these cells.