Induction of CD95 ligand and apoptosis by doxorubicin is modulated by the redox state in chemosensitive- and drug-resistant tumor cells

Induction of CD95 ligand (CD95-L) may contribute to drug-induced apoptosis in chemosensitive leukemias and solid tumors, Here we report that induction of CD95-L and apoptosis by doxorubicin in leukemic and neuroblastoma cells is regulated by the redox state and reactive oxygen species (ROS), Preincu bation of chemosensitive cells with antioxidants such as N-acetyl-cysteine (NAC) or glutathione (GSH), significantly reduced doxorubicin-induced apopt osis, hyperexpression of ROS, loss of mitochondrial membrane potential (Del ta Psi(m)) and upregulation of CD95-L expression. Doxorubicin-resistant cel ls exhibited higher levels of GSH in comparison to chemosensitive cells and were deficient in hyperproduction of ROS, loss of Delta Psi(m) and upregul ation of CD95-L in response to cytotoxic drugs, Downregulation of intracell ular GSH concentrations reversed deficient drug-induced hyperproduction of ROS and CD95-L upregulation, In addition, overexpression of Bcl-X-L in CEM cells blocked doxorubicin-triggered ROS and CD95-L expression, These findin gs suggest that induction of CD95-L by cytotoxic drugs is modulated by the cellular redox state and mitochondria derived ROS.