An optimized retinoic acid-inducible gene I agonist M8 induces immunogenic cell death markers in human cancer cells and dendritic cell activation

Luciano Castiello, Alessandra Zevini, Elisabetta Vulpis, Michela Muscolini, Matteo Ferrari, Enrico Palermo, Giovanna Peruzzi, Christian Krapp, Martin Jakobsen, David Olagnier, Alessandra Zingoni, Angela Santoni, John Hiscott

Research output: Contribution to journalArticlepeer-review


RIG-I is a cytosolic RNA sensor that recognizes short 5' triphosphate RNA, commonly generated during virus infection. Upon activation, RIG-I initiates antiviral immunity, and in some circumstances, induces cell death. Because of this dual capacity, RIG-I has emerged as a promising target for cancer immunotherapy. Previously, a sequence-optimized RIG-I agonist (termed M8) was generated and shown to stimulate a robust immune response capable of blocking viral infection and to function as an adjuvant in vaccination strategies. Here, we investigated the potential of M8 as an anti-cancer agent by analyzing its ability to induce cell death and activate the immune response. In multiple cancer cell lines, M8 treatment strongly activated caspase 3-dependent apoptosis, that relied on an intrinsic NOXA and PUMA-driven pathway that was dependent on IFN-I signaling. Additionally, cell death induced by M8 was characterized by the expression of markers of immunogenic cell death-related damage-associated molecular patterns (ICD-DAMP)-calreticulin, HMGB1 and ATP-and high levels of ICD-related cytokines CXCL10, IFNβ, CCL2 and CXCL1. Moreover, M8 increased the levels of HLA-ABC expression on the tumor cell surface, as well as up-regulation of genes involved in antigen processing and presentation. M8 induction of the RIG-I pathway in cancer cells favored dendritic cell phagocytosis and induction of co-stimulatory molecules CD80 and CD86, together with increased expression of IL12 and CXCL10. Altogether, these results highlight the potential of M8 in cancer immunotherapy, with the capacity to induce ICD-DAMP on tumor cells and activate immunostimulatory signals that synergize with current therapies.

Original languageEnglish
Pages (from-to)1479-1492
Number of pages14
JournalCancer Immunology and Immunotherapy
Issue number9
Publication statusPublished - Sep 2019


  • Alarmins/immunology
  • Antigen Presentation/drug effects
  • Antineoplastic Agents/pharmacology
  • Apoptosis/drug effects
  • Apoptosis Regulatory Proteins/metabolism
  • Calreticulin/metabolism
  • Caspase 3/metabolism
  • Cell Differentiation
  • Cell Line, Tumor
  • DEAD Box Protein 58/antagonists & inhibitors
  • Dendritic Cells/immunology
  • HMGB1 Protein/metabolism
  • Humans
  • Immunization
  • Interferons/metabolism
  • Melanoma/drug therapy
  • Molecular Targeted Therapy
  • Nelfinavir/analogs & derivatives
  • Proto-Oncogene Proteins/metabolism
  • Proto-Oncogene Proteins c-bcl-2/metabolism
  • Signal Transduction


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