Selective reactivation of STING signaling to target Merkel cell carcinoma

Wei Liu, Gloria B. Kim, Nathan A. Krump, Yuqi Zhou, James L. Riley, Jianxin You

Research output: Contribution to journalArticlepeer-review


Merkel cell carcinoma (MCC) is a lethal skin cancer that metastasizes rapidly. Few effective treatments are available for patients with metastatic MCC. Poor intratumoral T cell infiltration and activation are major barriers that prevent MCC eradication by the immune system. However, the mechanisms that drive the immunologically restrictive tumor microenvironment remain poorly understood. In this study, we discovered that the innate immune regulator stimulator of IFN genes (STING) is completely silenced in MCCs. To reactivate STING in MCC, we developed an application of a human STING mutant, STINGS162A/G230I/Q266I, which we found to be readily stimulated by a mouse STING agonist, DMXAA. This STING molecule was efficiently delivered to MCC cells via an AAV vector. Introducing STINGS162A/G230I/Q266I expression and stimulating its activity by DMXAA in MCC cells reactivates their antitumor inflammatory cytokine/ chemokine production. In response to MCC cells with restored STING, cocultured T cells expressing MCPyV-specific T cell receptors (TCRs) showincreased cytokine production, migration toward tumor cells, and tumor cell killing. Our study therefore suggests that STING deficiency contributes to the immune suppressive nature of MCCs. More importantly, DMXAA stimulation of STINGS162A/G230I/Q266I causes robust cell death in MCCs as well as several other STING silenced cancers. Because tumor antigens and DNA released by dying cancer cells have the potential to amplify innate immune response and activate antitumor adaptive responses, our finding indicates that targeted delivery and activation of STINGS162A/G230I/Q266I in tumor cells holds great therapeutic promise for the treatment of MCC and many other STING-deficient cancers.

Original languageEnglish (US)
Pages (from-to)13730-13739
Number of pages10
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number24
StatePublished - Jun 16 2020


  • Antitumor immune response
  • Gene therapy
  • Merkel cell carcinoma

ASJC Scopus subject areas

  • General


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