Fluoxetine Regulates Cell Growth Inhibition Of Interferon-Alpha

Fluoxetine, a well-known anti-depression agent, may act as a chemosensitizer to assist and promote cancer therapy. However, how fluoxetine regulates cellular signaling to enhance cellular responses against tumor cell growth remains unclear. In the present study, addition of fluoxetine promoted growth inhibition of interferon-alpha (IFN-alpha) in human bladder carcinoma cells but not in normal uroepithelial cells through lessening the IFN-alpha-induced apoptosis but switching to cause G1 arrest, and maintaining the IFN-amediated reduction in G2/M phase. Activations and signal transducer and transactivator (STAT)-1 and peroxisome proliferator-activated receptor alpha (PPAR-alpha) were involved in this process. Chemical inhibitions of STAT-1 or PPAR-alpha partially rescued bladder carcinoma cells from IFN-amediated growth inhibition via blockades of G1 arrest, cyclin D1 reduction, p53 downregulation and p27 upregulation in the presence of fluoxetine. However, the functions of both proteins were not involved in the control of fluoxetine over apoptosis and maintained the declined G2/M phase of IFN-alpha. These results indicated that activation of PPAR-alpha and STAT-1 participated, at least in part, in growth inhibition of IFN-alpha in the presence of fluoxetine.