title: Smac mimetics increase cancer cell response to chemotherapeutics in a TNF-α-dependent manner.
abstract: Second mitochondria-derived activator of caspase (Smac) is a mitochondrial protein released into the cytosol during apoptosis. Smac mimetics have recently been touted as a novel therapeutic to induce apoptosis in cancer cells. The ability of Smac mimetics to induce apoptosis in vitro has been shown to be dependent upon both XIAP neutralization and cancer cell autocrine tumor necrosis factor-α (TNF-α) production. In this study we provide new evidence for the utility of Smac mimetics in combination with conventional chemotherapy agents to exacerbate caspase activation and induce cancer cell death. Furthermore, we find that the combination effect is because of a multifaceted mechanism involving both inhibition of cell proliferation by the chemotherapy agents and an enhanced autocrine TNF-α feedback loop by the Smac mimetic/chemotherapy agent combination. Surprisingly, although genotoxic agents typically induce apoptosis through the mitochondrial intrinsic pathway, we show that this synergism is mediated through a TNF-α/RIP1-dependent pathway, leading to activation of the extrinsic apoptotic pathway. Finally, we report that autocrine TNF-α contributes to Smac mimetic-induced tumor regression as a single agent or in combination with chemotherapeutics in xenograft mouse models. Collectively, we provide mechanistic and applicable data to support translational studies in the use of a Smac mimetic/chemotherapy antineoplasm modality.
authors.affiliation: Joyant Pharmaceuticals Inc., Dallas, TX 75207, USA.
authors.forename: B L
authors.initials: BL
authors.lastname: Probst
authors.forename: L
authors.initials: L
authors.lastname: Liu
authors.forename: V
authors.initials: V
authors.lastname: Ramesh
authors.forename: L
authors.initials: L
authors.lastname: Li
authors.forename: H
authors.initials: H
authors.lastname: Sun
authors.forename: J D
authors.initials: JD
authors.lastname: Minna
authors.forename: L
authors.initials: L
authors.lastname: Wang
mesh_terms: D062365:Aminobenzoates / Q000737:chemistry / Q000627:therapeutic use*; D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D004357:Drug Synergism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry; D008175:Lung Neoplasms / Q000188:drug therapy; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000737:chemistry; D009842:Oligopeptides / Q000737:chemistry / Q000627:therapeutic use*; D014183:Transplantation, Heterologous; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism*; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism
chemical_list: D062365:Aminobenzoates; D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; C412403:DIABLO protein, human; D047908:Intracellular Signaling Peptides and Proteins; C554674:JP 1400; D024101:Mitochondrial Proteins; D009842:Oligopeptides; D014409:Tumor Necrosis Factor-alpha; D051636:X-Linked Inhibitor of Apoptosis Protein; D053148:Caspase 3