title: IFN-gamma inhibition of TRAIL-induced IAP-2 upregulation, a possible mechanism of IFN-gamma-enhanced TRAIL-induced apoptosis.
abstract: Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a type II transmembrane cytokine molecule of TNF family and a potent inducer of apoptosis. The anticancer activities of TNF family members are often modulated by interferon (IFN)-gamma. Thus, we investigated whether IFN-gamma enhances TRAIL-induced apoptosis. We exposed HeLa cells to IFN-gamma for 12 h and then treated with recombinant TRAIL protein. No apoptosis was induced in cells pretreated with IFN-gamma, and TRAIL induced 25% cell death after 3 h treatment. In HeLa cells pretreated with IFN-gamma, TRAIL induced cell death to more than 70% at 3 h, indicating that IFN-gamma pretreatment sensitized HeLa cells to TRAIL-induced apoptosis. We investigated molecules that might be regulated by IFN-gamma pretreatment that would affect TRAIL-induced apoptosis. Western blotting analyses demonstrated that TRAIL treatment increased the level of IAP-2 protein and IFN-gamma pretreatment inhibited the upregulation of IAP-2 protein by TRAIL protein. Our data indicate that TRAIL can signal to activate both apoptosis induction and antiapoptotic mechanism, at least, through IAP-2 simultaneously. IFN-gamma or TRAIL treatment alone did not change expression of other pro- or antiapoptotic proteins such as DR4, DR5, FADD, Bax, IAP-1, XIAP, Bcl-2, and Bcl-XL. Our findings suggest that IFN-gamma may sensitize HeLa cells to TRAIL-induced apoptosis by preventing TRAIL-induced IAP-2 upregulation, and IFN-gamma may play a role in anticancer therapy of TRAIL protein through such mechanism.
authors.affiliation: Department of Surgery, University of Pittsburgh School of Medicine, BSTW1513, Pittsburgh, Pennsylvania 15261, USA.
authors.forename: Sang-Youel
authors.initials: SY
authors.lastname: Park
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Billiar
authors.forename: Dai-Wu
authors.initials: DW
authors.lastname: Seol
mesh_terms: D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D015153:Blotting, Western; D004357:Drug Synergism; D006367:HeLa Cells; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins; D007371:Interferon-gamma / Q000494:pharmacology*; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D011506:Proteins / Q000378:metabolism*; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D015854:Up-Regulation
chemical_list: D051017:Apoptosis Regulatory Proteins; D051034:Inhibitor of Apoptosis Proteins; D008562:Membrane Glycoproteins; D011506:Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma