SMAC Mimetic Birinapant plus Radiation Eradicates Human Head and Neck Cancers with Genomic Amplifications of Cell Death Genes FADD and BIRC2

Cancer Res. 2016 Sep 15;76(18):5442-5454. doi: 10.1158/0008-5472.CAN-15-3317. Epub 2016 Jul 28.


Comparison of tumors from The Cancer Genome Atlas (TCGA) reveals that head and neck squamous cell carcinomas (HNSCC) harbor the most frequent genomic amplifications of Fas-associated death domain (FADD), with or without Baculovirus inhibitor of apoptosis repeat containing BIRC2 (cIAP1), affecting about 30% of patients in association with worse prognosis. Here, we identified HNSCC cell lines harboring FADD/BIRC2 amplifications and overexpression by exome sequencing, RT-PCR, and Western blotting. In vitro, FADD or BIRC2 siRNA knockdown inhibited HNSCC displaying amplification and increased expression of these genes, supporting their functional importance in promoting proliferation. Birinapant, a novel SMAC mimetic, sensitized multiple HNSCC lines to cell death by agonists TNFα or TRAIL and inhibited cIAP1>XIAP>IAP2. Combination of birinapant and TNFα induced sub-G0 DNA fragmentation in sensitive lines and birinapant alone also induced significant G2-M cell-cycle arrest and cell death in UM-SCC-46 cells. Gene transfer and expression of FADD sensitized resistant UM-SCC-38 cells lacking FADD amplification to birinapant and TNFα, supporting a role for FADD in sensitization to IAP inhibitor and death ligands. HNSCC varied in mechanisms of cell death, as indicated by reversal by inhibitors or protein markers of caspase-dependent apoptosis and/or RIPK1/MLKL-mediated necroptosis. In vivo, birinapant inhibited tumor growth and enhanced radiation-induced TNFα, tumor responses, and host survival in UM-SCC-46 and -11B xenograft models displaying amplification and overexpression of FADD+/- BIRC2 These findings suggest that combination of SMAC mimetics such as birinapant plus radiation may be particularly active in HNSCC, which harbor frequent FADD/BIRC2 genomic alterations. Cancer Res; 76(18); 5442-54. ©2016 AACR.

MeSH terms

  • Animals
  • Antineoplastic Agents / administration & dosage*
  • Blotting, Western
  • Carcinoma, Squamous Cell / genetics*
  • Carcinoma, Squamous Cell / pathology
  • Cell Line, Tumor
  • Chemoradiotherapy / methods*
  • Dipeptides / administration & dosage*
  • Fas-Associated Death Domain Protein / genetics*
  • Female
  • Gene Amplification
  • Gene Knockdown Techniques
  • Head and Neck Neoplasms / genetics*
  • Head and Neck Neoplasms / pathology
  • Humans
  • Immunohistochemistry
  • Indoles / administration & dosage*
  • Inhibitor of Apoptosis Proteins / genetics*
  • Mice
  • Mice, Inbred BALB C
  • Mice, SCID
  • Real-Time Polymerase Chain Reaction
  • Squamous Cell Carcinoma of Head and Neck
  • TNF-Related Apoptosis-Inducing Ligand / administration & dosage
  • Tumor Necrosis Factor-alpha / administration & dosage
  • Ubiquitin-Protein Ligases / genetics*
  • Xenograft Model Antitumor Assays


  • Antineoplastic Agents
  • Dipeptides
  • FADD protein, human
  • Fas-Associated Death Domain Protein
  • Indoles
  • Inhibitor of Apoptosis Proteins
  • TNF-Related Apoptosis-Inducing Ligand
  • Tumor Necrosis Factor-alpha
  • birinapant
  • BIRC2 protein, human
  • Ubiquitin-Protein Ligases