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STING-driven interferon signaling triggers metabolic alterations in pancreas cancer cells visualized by [18F]FLT PET imaging

ABSTRACT: Type I interferons (IFNs) are critical effectors of emerging cancer immunotherapies designed to activate pattern recognition receptors (PRRs). A challenge in the clinical translation of these new immuno-modulatory agents is the lack of pharmacodynamic biomarkers indicative of increased intratumoral IFN signaling following PRR activation. Positron emission tomography (PET) imaging enables the visualization of tissue metabolic activity but whether IFN signaling-induced alterations in tumor cell metabolism can be detected using PET has not been investigated. We found that IFN signaling augments pancreatic ductal adenocarcinoma (PDAC) cell nucleotide metabolism via transcriptional induction of metabolism-associated genes including thymidine phosphorylase (TYMP). TYMP catalyzes the first step in the catabolism of thymidine which competitively inhibits intratumoral accumulation of the nucleoside analog PET probe [18F]-fluorothymidine ([18F]FLT). Accordingly, IFN treatment stimulates cancer cell [18F]FLT uptake in the presence of thymidine and this effect is dependent on TYMP expression. In vivo, genetic activation of stimulator of interferon genes (STING), a PRR widely expressed in PDAC, enhances the [18F]FLT avidity of xenograft tumors. Treatment with a small molecule STING agonist triggers IFN signaling-dependent TYMP expression in PDAC cells and enhances both subcutaneous and orthotopic tumor [18F]FLT uptake in vivo following systemic treatment. These findings indicate that [18F]FLT accumulation in tumors is sensitive to IFN signaling and that [18F]FLT PET may serve as a novel pharmacodynamic biomarker for PRR agonist-based immunotherapies in PDAC and possibly other malignancies characterized by elevated STING expression.

ORGANISM(S): Homo sapiens

PROVIDER: GSE178901 | GEO | 2021/08/30

REPOSITORIES: GEO

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Project description:Type I interferon (IFN) response is the most recognized signaling activity of STING, and IFN signaling is commonly believed to be the major (if not the sole) contributor to STING-mediated anti-viral and anti-cancer responses. Here, we genetically mutated mouse Sting serine 365 residue that is critically required for initiating IFN signaling. Sting-S365A mutation in mice precisely ablated IFN-dependent while preserving IFN-independent activities of STING. To our surprise, StingS365A/S365A mice protected against HSV-1 infection remarkably well, similar to wild type mice, while Sting–/– mice succumbed to infection very quickly. This challenges the current prevailing view and suggests that STING controls HSV-1 infection through IFN-independent activities. Transcriptomic analysis of wild type, Sting–/– and StingS365A/S365A macrophages and T cells stimulated with Sting agonist DMXAA revealed widespread IFN-independent activities of STING in both cell types and identified many T cell effector functions that are activated by STING independently of IFN. In mouse tumor models, we found that T cells in the tumor experience substantial cell death that was in part mediated by STING. Adoptively transferred Sting–/– T cells were more resistant to cell death in the tumor leading to more effective tumor control compared to wild type and StingS365A/S365A T cells. Together, our data demonstrate that mammalian STING possesses widespread IFN-independent activities that are functionally important for restricting Type I interferon (IFN) response is the most recognized signaling activity of STING, and IFN signaling is commonly believed to be the major (if not the sole) contributor to STING-mediated anti-viral and anti-cancer responses. Here, we genetically mutated mouse Sting serine 365 residue that is critically required for initiating IFN signaling. Sting-S365A mutation in mice precisely ablated IFN-dependent while preserving IFN-independent activities of STING. To our surprise, StingS365A/S365A mice protected against HSV-1 infection remarkably well, similar to wild type mice, while Sting–/– mice succumbed to infection very quickly. This challenges the current prevailing view and suggests that STING controls HSV-1 infection through IFN-independent activities. Transcriptomic analysis of wild type, Sting–/– and StingS365A/S365A macrophages and T cells stimulated with Sting agonist DMXAA revealed widespread IFN-independent activities of STING in both cell types and identified many T cell effector functions that are activated by STING independently of IFN. In mouse tumor models, we found that T cells in the tumor experience substantial cell death that was in part mediated by STING. Adoptively transferred Sting–/– T cells were more resistant to cell death in the tumor leading to more effective tumor control compared to wild type and StingS365A/S365A T cells. Together, our data demonstrate that mammalian STING possesses widespread IFN-independent activities that are functionally important for restricting HSV-1 infection, tumor immune evasion and likely also adaptive T cell immunity.

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STING-driven interferon signaling triggers metabolic alterations in pancreas cancer cells visualized by [18F]FLT PET imaging

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