To study their differentiation capacity the cells were seeded subconfluently into 6-well plates and subsequently treated according to various published protocols [2, 3 (link)]. In one protocol, EGFR inhibition and PPARγ activation were achieved by treatment with 1 μM PD153035 (Merck, Germany) and 1 μM Troglitazone (Cayman, USA) in CnT-Prime Epithelial Culture Medium (ready to use and supplemented with EGF, CELLnTEC) or in KFSM medium without supplemented EGF (Life Technologies, Germany) for seven days, during which the medium was changed twice. For some experiments 5% FBS (Biochrom, Germany) was added to cells in CnT-Prime Medium. For a second, calcium-based protocol near-confluent cultures were maintained in CnT-Prime Medium supplemented with CaCl2 to a final concentration of 2 mM, with additional 5% FBS in some experiments, for a period of 10–14 days. The medium was changed every 3 days.
For comparison, primary cultures of normal urothelial cells (NHUC) were established from healthy ureters removed during tumor nephrectomy. These samples were collected with informed consent of the patients and their use was approved by the Ethics Committee of the Medical Faculty of the Heinrich-Heine-University, study number 1788. The cells were cultured as published previously [8 (link)] in KFSM medium supplemented with 5 ng/ml EGF and 50 μg/ml bovine pituitary extract (Life Technologies).
TERT-NHUC cells, kindly provided by Prof. M.A. Knowles, University of Leeds, UK, were cultured as previously described [9 (link)].