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Abstract

Cytotoxic therapies prime adaptive immune responses to cancer by stimulating the release of tumor-associated antigens. However, the tumor microenvironment into which these antigens are released is typically immunosuppressed, blunting the ability to initiate immune responses. Recently, activation of the DNA sensor molecule STING by cyclic dinucleotides was shown to stimulate infection-related inflammatory pathways in tumors. In this study, we report that the inflammatory pathways activated by STING ligands generate a powerful adjuvant activity for enhancing adaptive immune responses to tumor antigens released by radiotherapy. In a murine model of pancreatic cancer, we showed that combining CT-guided radiotherapy with a novel ligand of murine and human STING could synergize to control local and distant tumors. Mechanistic investigations revealed T-cell-independent and TNFα-dependent hemorrhagic necrosis at early times, followed by later CD8 T-cell-dependent control of residual disease. Clinically, STING was found to be expressed extensively in human pancreatic tumor and stromal cells. Our findings suggest that this novel STING ligand could offer a potent adjuvant for leveraging radiotherapeutic management of pancreatic cancer.  

Author information

Baird JR1, Friedman D1, Cottam B1, Dubensky TW Jr2, Kanne DB2, Bambina S1, Bahjat K1, Crittenden MR3, Gough MJ4.​

1Earle A. Chiles Research Institute, Robert W. Franz Cancer Center, Providence Portland Medical Center, Portland, Oregon.

2Aduro Biotech, Inc., Berkeley, California.

3Earle A. Chiles Research Institute, Robert W. Franz Cancer Center, Providence Portland Medical Center, Portland, Oregon. The Oregon Clinic, Portland, Oregon.

4Earle A. Chiles Research Institute, Robert W. Franz Cancer Center, Providence Portland Medical Center, Portland, Oregon. michael.gough@providence.org.