Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Smac mimetics and innate immune stimuli synergize to promote tumor death


Smac mimetic compounds (SMC), a class of drugs that sensitize cells to apoptosis by counteracting the activity of inhibitor of apoptosis (IAP) proteins, have proven safe in phase 1 clinical trials in cancer patients. However, because SMCs act by enabling transduction of pro-apoptotic signals, SMC monotherapy may be efficacious only in the subset of patients whose tumors produce large quantities of death-inducing proteins such as inflammatory cytokines. Therefore, we reasoned that SMCs would synergize with agents that stimulate a potent yet safe “cytokine storm.” Here we show that oncolytic viruses and adjuvants such as poly(I:C) and CpG induce bystander death of cancer cells treated with SMCs that is mediated by interferon beta (IFN-β), tumor necrosis factor alpha (TNF-α) and/or TNF-related apoptosis-inducing ligand (TRAIL). This combinatorial treatment resulted in tumor regression and extended survival in two mouse models of cancer. As these and other adjuvants have been proven safe in clinical trials, it may be worthwhile to explore their clinical efficacy in combination with SMCs.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: SMC synergizes with oncolytic rhabdoviruses to induce bystander death of cancer cells.
Figure 2: SMC treatment does not alter the antiviral response of cancer cells.
Figure 3: Roles for type 1 IFN- and NF-κB-dependent proinflammatory cytokines.
Figure 4: Combinatorial SMC and oncolytic virus treatment is efficacious in vivo and depends on cytokine signaling.
Figure 5: Adjuvants synergize with SMC therapy in murine cancer models.


  1. 1

    Fulda, S. & Vucic, D. Targeting IAP proteins for therapeutic intervention in cancer. Nat. Rev. Drug Discov. 11, 109–124 (2012).

    CAS  Article  Google Scholar 

  2. 2

    LaCasse, E.C. Pulling the plug on a cancer cell by eliminating XIAP with AEG35156. Cancer Lett. 332, 215–224 (2013).

    CAS  Article  Google Scholar 

  3. 3

    Dougan, M. et al. IAP inhibitors enhance co-stimulation to promote tumour immunity. J. Exp. Med. 207, 2195–2206 (2010).

    CAS  Article  Google Scholar 

  4. 4

    Vanneman, M. & Dranoff, G. Combining immunotherapy and targeted therapies in cancer treatment. Nat. Rev. Cancer 12, 237–251 (2012).

    CAS  Article  Google Scholar 

  5. 5

    Gyrd-Hansen, M. & Meier, P. IAPs: from caspase inhibitors to modulators of NF-kappaB, inflammation and cancer. Nat. Rev. Cancer 10, 561–574 (2010).

    CAS  Article  Google Scholar 

  6. 6

    Vandenabeele, P. & Bertrand, M.J. The role of the IAP E3 ubiquitin ligases in regulating pattern-recognition receptor signalling. Nat. Rev. Immunol. 12, 833–844 (2012).

    CAS  Article  Google Scholar 

  7. 7

    Varfolomeev, E. et al. Cellular inhibitors of apoptosis are global regulators of NF-kappaB and MAPK activation by members of the TNF family of receptors. Sci. Signal. 5, ra22 (2012).

    Article  Google Scholar 

  8. 8

    Beug, S.T., Cheung, H.H., LaCasse, E.C. & Korneluk, R.G. Modulation of immune signalling by inhibitors of apoptosis. Trends Immunol. 33, 535–545 (2012).

    CAS  Article  Google Scholar 

  9. 9

    Mahoney, D.J. et al. Both cIAP1 and cIAP2 regulate TNFalpha-mediated NF-kappaB activation. Proc. Natl. Acad. Sci. USA 105, 11778–11783 (2008).

    CAS  Article  Google Scholar 

  10. 10

    Li, L. et al. A small molecule Smac mimic potentiates TRAIL- and TNF{alpha}-mediated cell death. Science 305, 1471–1474 (2004).

    CAS  Article  Google Scholar 

  11. 11

    Varfolomeev, E. et al. IAP antagonists induce autoubiquitination of c-IAPs, NF-kappaB activation, and TNFalpha-dependent apoptosis. Cell 131, 669–681 (2007).

    CAS  Article  Google Scholar 

  12. 12

    Vince, J.E. et al. IAP antagonists target cIAP1 to induce TNFalpha-dependent apoptosis. Cell 131, 682–693 (2007).

    CAS  Article  Google Scholar 

  13. 13

    Petersen, S.L. et al. Autocrine TNFalpha signalling renders human cancer cells susceptible to Smac-mimetic-induced apoptosis. Cancer Cell 12, 445–456 (2007).

    CAS  Article  Google Scholar 

  14. 14

    Gaither, A. et al. A Smac mimetic rescue screen reveals roles for inhibitor of apoptosis proteins in tumour necrosis factor-alpha signalling. Cancer Res. 67, 11493–11498 (2007).

    CAS  Article  Google Scholar 

  15. 15

    Cheung, H.H., Mahoney, D.J., Lacasse, E.C. & Korneluk, R.G. Down-regulation of c-FLIP Enhances death of cancer cells by smac mimetic compound. Cancer Res. 69, 7729–7738 (2009).

    CAS  Article  Google Scholar 

  16. 16

    Cheung, H.H. et al. Smac mimetic compounds potentiate interleukin-1 beta-mediated cell death. J. Biol. Chem. 285, 40612–40623 (2010).

    CAS  Article  Google Scholar 

  17. 17

    Kawai, T. & Akira, S. The role of pattern-recognition receptors in innate immunity: update on Toll-like receptors. Nat. Immunol. 11, 373–384 (2010).

    CAS  Article  Google Scholar 

  18. 18

    Chen, G., Shaw, M.H., Kim, Y.G. & Nunez, G. NOD-like receptors: role in innate immunity and inflammatory disease. Annu. Rev. Pathol. 4, 365–398 (2009).

    CAS  Article  Google Scholar 

  19. 19

    McFadden, G., Mohamed, M.R., Rahman, M.M. & Bartee, E. Cytokine determinants of viral tropism. Nat. Rev. Immunol. 9, 645–655 (2009).

    CAS  Article  Google Scholar 

  20. 20

    Russell, S.J., Peng, K.W. & Bell, J.C. Oncolytic virotherapy. Nat. Biotechnol. 30, 658–670 (2012).

    CAS  Article  Google Scholar 

  21. 21

    Houghton, P.J. et al. Initial testing (stage 1) of LCL161, a SMAC mimetic, by the Pediatric Preclinical Testing Program. Pediatr. Blood Cancer 58, 636–639 (2012).

    Article  Google Scholar 

  22. 22

    Chen, K.F. et al. Inhibition of Bcl-2 improves effect of LCL161, a SMAC mimetic, in hepatocellular carcinoma cells. Biochem. Pharmacol. 84, 268–277 (2012).

    CAS  Article  Google Scholar 

  23. 23

    Dhuria, S. et al. Time-dependent inhibition and induction of human cytochrome P4503A4/5 by an Oral IAP Antagonist, LCL161, in vitro and in vivo in healthy subjects. J. Clin. Pharmacol. 53, 642–653 (2013).

    CAS  Article  Google Scholar 

  24. 24

    Breitbach, C.J. et al. Targeted inflammation during oncolytic virus therapy severely compromises tumour blood flow. Mol. Ther. 15, 1686–1693 (2007).

    CAS  Article  Google Scholar 

  25. 25

    Vaha-Koskela, M.J. et al. Resistance to two heterologous neurotropic oncolytic viruses, Semliki Forest virus and vaccinia virus, in experimental glioma. J. Virol. 87, 2363–2366 (2013).

    CAS  Article  Google Scholar 

  26. 26

    Le Boeuf, F. et al. Model-based rational design of an oncolytic virus with improved therapeutic potential. Nat. Commun. 4, 1974 (2013).

    Article  Google Scholar 

  27. 27

    Kawai, T. & Akira, S. Innate immune recognition of viral infection. Nat. Immunol. 7, 131–137 (2006).

    CAS  Article  Google Scholar 

  28. 28

    Kirshner, J.R., Karpova, A.Y., Kops, M. & Howley, P.M. Identification of TRAIL as an interferon regulatory factor 3 transcriptional target. J. Virol. 79, 9320–9324 (2005).

    CAS  Article  Google Scholar 

  29. 29

    Bose, S., Kar, N., Maitra, R., DiDonato, J.A. & Banerjee, A.K. Temporal activation of NF-kappaB regulates an interferon-independent innate antiviral response against cytoplasmic RNA viruses. Proc. Natl. Acad. Sci. USA 100, 10890–10895 (2003).

    CAS  Article  Google Scholar 

  30. 30

    Rosenfeld, M.R. et al. A multi-institution phase II study of poly-ICLC and radiotherapy with concurrent and adjuvant temozolomide in adults with newly diagnosed glioblastoma. Neuro-oncol. 12, 1071–1077 (2010).

    CAS  Article  Google Scholar 

  31. 31

    Butowski, N. et al. A phase II clinical trial of poly-ICLC with radiation for adult patients with newly diagnosed supratentorial glioblastoma: a North American Brain Tumour Consortium (NABTC01–05). J. Neurooncol. 91, 175–182 (2009).

    CAS  Article  Google Scholar 

  32. 32

    Butowski, N. et al. A North American brain tumour consortium phase II study of poly-ICLC for adult patients with recurrent anaplastic gliomas. J. Neurooncol. 91, 183–189 (2009).

    CAS  Article  Google Scholar 

  33. 33

    Krieg, A.M. CpG still rocks! Update on an accidental drug. Nucleic Acid Ther. 22, 77–89 (2012).

    CAS  Article  Google Scholar 

  34. 34

    Erickson, R.I. et al. Toxicity profile of small-molecule IAP antagonist GDC-0152 is linked to TNF-alpha pharmacology. Toxicol. Sci. 131, 247–258 (2013).

    CAS  Article  Google Scholar 

  35. 35

    Wong, H. et al. Dogs are more sensitive to antagonists of inhibitor of apoptosis proteins than rats and humans: a translational toxicokinetic/toxicodynamic analysis. Toxicol. Sci. 130, 205–213 (2012).

    CAS  Article  Google Scholar 

  36. 36

    Cantaert, T., Baeten, D., Tak, P.P. & van Baarsen, L.G. Type I IFN and TNFalpha cross-regulation in immune-mediated inflammatory disease: basic concepts and clinical relevance. Arthritis Res. Ther. 12, 219 (2010).

    Article  Google Scholar 

  37. 37

    Yarilina, A. & Ivashkiv, L.B. Type I interferon: a new player in TNF signalling. Curr. Dir. Autoimmun. 11, 94–104 (2010).

    CAS  Article  Google Scholar 

  38. 38

    Lu, J. et al. Therapeutic potential and molecular mechanism of a novel, potent, nonpeptide, smac mimetic SM-164 in combination with TRAIL for cancer treatment. Mol. Cancer Ther. 10, 902–914 (2011).

    CAS  Article  Google Scholar 

  39. 39

    Sun, H. et al. Design, synthesis, and characterization of a potent, nonpeptide, cell-permeable, bivalent Smac mimetic that concurrently targets both the BIR2 and BIR3 domains in XIAP. J. Am. Chem. Soc. 129, 15279–15294 (2007).

    CAS  Article  Google Scholar 

  40. 40

    Bertrand, M.J. et al. cIAP1 and cIAP2 facilitate cancer cell survival by functioning as E3 ligases that promote RIP1 ubiquitination. Mol. Cell 30, 689–700 (2008).

    CAS  Article  Google Scholar 

  41. 41

    Enwere, E.K. et al. TWEAK and cIAP1 regulate myoblast fusion through the noncanonical NF-kappaB signalling pathway. Sci. Signal. 5, ra75 (2012).

    Article  Google Scholar 

  42. 42

    Stojdl, D.F. et al. VSV strains with defects in their ability to shutdown innate immunity are potent systemic anti-cancer agents. Cancer Cell 4, 263–275 (2003).

    CAS  Article  Google Scholar 

  43. 43

    Brun, J. et al. Identification of genetically modified Maraba virus as an oncolytic rhabdovirus. Mol. Ther. 18, 1440–1449 (2010).

    CAS  Article  Google Scholar 

  44. 44

    Le Boeuf, F. et al. Synergistic interaction between oncolytic viruses augments tumour killing. Mol. Ther. 18, 888–895 (2010).

    CAS  Article  Google Scholar 

  45. 45

    Lun, X. et al. Efficacy and safety/toxicity study of recombinant vaccinia virus JX-594 in two immunocompetent animal models of glioma. Mol. Ther. 18, 1927–1936 (2010).

    CAS  Article  Google Scholar 

  46. 46

    Mikus, J. & Steverding, D. A simple colorimetric method to screen drug cytotoxicity against Leishmania using the dye Alamar Blue. Parasitol. Int. 48, 265–269 (2000).

    CAS  Article  Google Scholar 

  47. 47

    Chou, T.C. & Talaly, P. A simple generalized equation for the analysis of multiple inhibitions of Michaelis-Menten kinetic systems. J. Biol. Chem. 252, 6438–6442 (1977).

    CAS  PubMed  Google Scholar 

Download references


We thank D. Porter, B. Firestone, L. Zawel and J.S. Cameron of Novartis for providing LCL161. We thank S. Wang (University of Michigan) for providing SM-122 and SM-164. We thank R. Al-awar and her medicinal chemistry team at the Ontario Institute for Cancer Research (OICR) for providing OICR720. We thank S. Pichette for her assistance with the creation of VSVΔ51-TNF-α. This work is supported by grants awarded to R.G.K. by the Canadian Institutes of Health Research (CIHR, MOP #86627), the Ottawa Regional Cancer Foundation (ORCF), the Ottawa Kiwanis Medical Foundation, the Children's Hospital of Eastern Ontario (CHEO) Foundation, and The Lotte & John Hecht Memorial Foundation Innovation Grant of the Canadian Cancer Society. J.C.B. is supported by OICR and The Terry Fox Foundation. F.L.B. was supported by an industrial fellowship from CIHR. D.J.M. is the recipient of a New Investigator Award from the Alliance for Cancer Gene Therapy (USA). R.G.K. is a Fellow of the Royal Society of Canada and a distinguished professor of the University of Ottawa. We thank D. Stojdl (Children's Hospital of Eastern Ontario Research Institute) for SNB75.

Author information




S.T.B., E.C.L., V.A.T., F.L.B., D.J.M. and R.G.K. designed the experiments. S.T.B., H.H.C., J.P.N., N.E., M.S.-J., J.H., C.E.B., V.A.T., F.L., C.I., H.D. and J.B. conducted experiments. S.T.B., E.C.L., V.A.T., J.C.B., D.J.M. and R.G.K. wrote the manuscript.

Corresponding author

Correspondence to Robert G Korneluk.

Ethics declarations

Competing interests

R.G.K. is a scientific founder and shareholder of Aegera Therapeutics (Pharmascience Inc., Montreal, Canada) which has an SMC under clinical development. J.C.B. is the Chief Scientific Officer and a shareholder of Jennerex (Ottawa, Canada and San Francisco, USA), which has a Vaccinia-based oncolytic virus under clinical development.

Supplementary information

Supplementary Text and Figures

Supplementary Figures 1–19 and Supplementary Tables 1 and 2 (PDF 3891 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Beug, S., Tang, V., LaCasse, E. et al. Smac mimetics and innate immune stimuli synergize to promote tumor death. Nat Biotechnol 32, 182–190 (2014).

Download citation

Further reading


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing