title: XK469, a topo IIbeta inhibitor, induces apoptosis in Waldenstrom's macroglobulinemia through multiple pathways.
abstract: We have previously reported that XK469 inhibited topoisomerase (topo) IIbeta, in Waldenstrom's macroglobulinemia cell line (WSU-WM) however the inhibition alone is not sufficient to induce apoptosis. In this study, the apoptotic potential of XK469 and its mechanism in WSU-WM cell line was investigated. Exposure of WSU-WM cells to XK469 caused a decrease in viable cell number in a dose-dependent manner. In addition, XK469 caused the activation of caspase 3 resulting in subsequent cleavage of PARP. These events were preceded by the release of cytochrome c from the mitochondria to the cytosol. Simultaneous exposure of cells to cyclosporin A prevented the release of cytochrome c to cytosol and reduced the loss of viability. XK469 caused the activation of p53 with up-regulation of p53-dependent proteins such as Bax, p21, Gadd 45 and cyclin B1 in association with G2M arrest. The addition of ubiquitin carboxyl terminal hydrolase (UCH-L1) inhibitor (NaBH4) inhibited up-regulation of p53 and p53 related molecules by XK469 and reduced the loss of viability. Pre-incubation with NOK-1, a monoclonal antibody that prevents Fas-Fas ligand interaction and is inhibitory to Fas signaling interfered with XK469 induced activation of caspase 8 and also reduced the loss of viability. Simultaneous exposure of all three inhibitors (cyclosporin A, NaBH4 and NOK-1) abrogated the toxicity of XK469 by 95%. These data define multiple sequences of biochemical events that mediate cell death induced by XK469. Our study suggests a complex mechanistic cascade of XK469-mediated apoptosis that involves Fas signaling pathway, ubiquitination, p53 activation and cytochrome c release.
authors: Division of Hematology and Oncology, Department of Internal Medicine, Karmanos Cancer Institute at Wayne State University School of Medicine, Detroit, MI 48201, USA.
authors: Edith
authors: E
authors: Mensah-Osman
authors: Ayad
authors: A
authors: Al-Katib
authors: Mahmoud
authors: M
authors: Dandashi
authors: Ramzi
authors: R
authors: Mohammad
mesh_terms: D017209:Apoptosis; D015153:Blotting, Western; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle; D045744:Cell Line, Tumor; D002470:Cell Survival; D016572:Cyclosporine / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004249:DNA Damage; D004250:DNA Topoisomerases, Type II; D004268:DNA-Binding Proteins; D003720:Densitometry; D004305:Dose-Response Relationship, Drug; D003576:Electron Transport Complex IV / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D053222:Fas Ligand Protein; D005470:Fluorometry; D006801:Humans; D008024:Ligands; D008562:Membrane Glycoproteins; D008928:Mitochondria / Q000378:metabolism; D008954:Models, Biological; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011810:Quinoxalines / Q000494:pharmacology*; D015398:Signal Transduction; D013997:Time Factors; D059005:Topoisomerase II Inhibitors; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D015854:Up-Regulation; D008258:Waldenstrom Macroglobulinemia / Q000378:metabolism* / Q000473:pathology
chemical_list: D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008024:Ligands; D008562:Membrane Glycoproteins; D011810:Quinoxalines; D059005:Topoisomerase II Inhibitors; D016159:Tumor Suppressor Protein p53; C118180:XK 469; D016572:Cyclosporine; D045304:Cytochromes c; D003576:Electron Transport Complex IV; D011065:Poly(ADP-ribose) Polymerases; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D004250:DNA Topoisomerases, Type II