Pilot Projects

Project Title: Sodium Arsenite-Induced Oxidative Stress is Followed by Trail-Mediated Apoptosis in Melanoma Cells

Principal Investigators: Vladimir N. Ivanov, Ph.D. (Center for Radiological Research)

Collaborator: Tom Hei, Ph.D. (CEHNM)
Year: 2005
Award Amount: $25,000

Summary. Previous studies have demonstrated that exposure to sodium arsenite induces oxidative stress that leads to elevated levels of DNA damage and presumably increased cancer risk. But sodium arsenite is also an effective drug for the treatment of acute promyelocytic leukemia with little nonspecific toxicity. AP-1/cJun, NF-kB and STAT3 transcription factors control expression of numerous genes that regulate critical cell functions including proliferation, survival and apoptosis. Sodium arsenite is known to suppress both the IKK-NF-kB and JAK2-STAT3 signaling pathways and to activate the MAPK/JNK-cJun pathways, thereby causing certain cancers to undergo apoptosis. Malignant melanoma is highly refractory to conventional radio- and chemotherapy and a good candidate for treatment with sodium arsenite. Understanding its role controlling gene expression will also lead to better understanding the effects of lower dose environmental exposure.

Results. Strong effects of sodium arsenite treatment on upregulation of TRAIL-mediated apoptosis in human and mouse melanomas were observed. Arsenite treatment upregulated surface levels of death receptors, TRAIL-R1 and TRAIL-R2, through increased translocation of these proteins from the cytoplasm to the cell surface. Furthermore, activation of cJun and suppression of NF-kB by sodium arsenite resulted in upregulation of the endogenous TRAIL- and downregulation of the cFLIP gene expression (which encodes one of the main anti-apoptotic proteins in melanomas) followed by cFLIP protein degradation and, finally, by the acceleration of TRAIL-induced apoptosis.

Direct suppression of cFLIP expression by cFLIP RNAi also accelerated TRAIL-induced apoptosis in these melanomas, while COX-2 suppression substantially increased levels of both TRAIL-induced and arsenite-induced apoptosis. In contrast, overexpression of permanently active AKTmyr inhibited TRAIL-mediated apoptosis via down-regulation of TRAIL-R1 levels. Finally, AKT overactivation increased melanoma survival in cell culture and dramatically accelerated growth of melanoma transplant in vivo, highlighting a role of AKT suppression for effective anti-cancer treatment.

Outcomes/Publications.

Ivanov VN, Hei TK. 2006. Sodium arsenite accelerates TRAIL-mediated apoptosis in melanoma cells through upregulation of TRAIL-R1/R2 surface levels and downregulation of cFLIP expression. Exp Cell Res. 312(20):4120-38.

Ivanov VN, Hei TK. 2006. Dual treatment with COX-2 inhibitor and sodium arsenite leads to induction of surface Fas Ligand expression and Fas-Ligand-mediated apoptosis in human melanoma cells. Exp Cell Res. 312(8):1401-17.

Ivanov VN, Ronai Z, Hei TK. 2006 Jan. Opposite roles of FAP-1 and dynamin in the regulation of Fas (CD95) translocation to the cell surface and susceptibility to Fas ligand-mediated apoptosis. J Biol Chem. 2006 281(3):1840-5.