Evaluation of IFN-γ effects on apoptosis and gene expression in neuroblastoma—Preclinical studies

Loss of caspase-8 expression and resistance to cytotoxic agents occurs frequently in late stage neuroblastoma (NB). Interferon-γ (IFN-γ) induces caspase-8 in NB cells, sensitizing them to death receptor mediated apoptosis. This study characterizes the kinetics of this phenomenon and examines the effects of IFN-γ on global gene expression to determine whether IFN-γ responses are achievable at physiologically relevant doses and to define the biological effects of this cytokine. Here we examine the IFN-γ responses of 16 NB cell lines. A single <5-min exposure to IFN-γ (0.5 ng/ml) induced caspase-8 expression in all non-expressing cell lines and in 3/6 cell lines which already expressed high caspase-8. This increase in caspase-8 proteins was observed within 16 h and persisted for up to 9 days. Furthermore, IFN-γ pretreatment of NB cells increased doxorubicin-induced apoptosis nearly 3-fold. Microarray analysis was used to identify additional genes involved in proliferation, signaling and apoptosis whose expression was modulated via IFN-γ. Altered expression of these genes should further enhance the responsiveness of NB cells to chemotherapeutics. Thus, the use of IFN-γ to sensitize NB cells to cytotoxic agents represents an attractive therapeutic strategy and warrants further investigation.