Alterations in the expression of inhibitors of apoptosis during differentiation of prostate epithelial cells.

ABSTRACT

OBJECTIVE: To investigate alterations in the apoptotic phenotype, specifically the inhibitors of apoptosis (IAP) family, in prostate epithelial cells after differentiation from an apoptotic-resistant basal cell to an apoptotic-susceptible secretory cell. MATERIALS AND METHODS: Cells of the immortalized human prostate epithelial line HPr-1AR were cultured with and with no 5alpha-dihydrotestosterone (DHT) to drive differentiation. Western blotting and reverse transcription-polymerase chain reaction (RT-PCR) were used to determine changes in differentiation markers such as cytokeratins (CK) 14 and 18, and in XIAP, cIAP-1 and cIAP-2. Flow cytometry was used to assess viability and apoptosis, by propidium iodide DNA staining of the cells during differentiation. RESULTS: Morphological changes and the increased CK-18 and decreased CK-14 expression confirmed differentiation of cells towards a secretory phenotype. Real-time PCR and Western blotting confirmed the expression of the IAPs in the HPr-1AR cells. There was a time-dependent decrease in the mRNA expression of XIAP, cIAP-1 and cIAP-2 after treatment with DHT. Differentiation also resulted in decreased cIAP-1 and XIAP protein expression, but cIAP-2 remained unchanged. Spontaneous apoptosis was significantly increased during cellular differentiation. CONCLUSION: We show for the first time that differentiation of HPr-1AR prostate epithelial cells results in the development of a transient end-stage cell that might be explained by the loss of the IAP family of proteins.