Demystifying the cGAS-STING pathway: precision regulation in the tumor immune microenvironment

Abstract

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway serves as an immune sentinel for cytosolic DNA, recognizing double-stranded DNA (dsDNA) derived from abnormally localized nuclear DNA or mitochondrial DNA (mtDNA), and plays a pivotal role in innate immune responses and tumor immune surveillance. Conventional antitumor therapies induce genomic instability and mitochondrial stress, leading to the release of nuclear DNA and mtDNA into the cytosol, thereby activating the cGAS-STING pathway. This activation triggers the production of type I interferons (IFN-I) and pro-inflammatory cytokines, which reshape the tumor immune microenvironment (TIME). However, the complexity of TIME reveals a "double-edged sword" effect of cGAS-STING signaling: while it activates antitumor immune responses, it also promotes immune escape and metastasis through the regulation of immunosuppressive cells and stromal components. This review comprehensively delineates the differential regulatory mechanisms of the pathway within TIME constituents, highlighting its multifaceted roles in tumor immunity. Furthermore, it reviews recent advances and challenges in targeting the cGAS-STING pathway for cancer immunotherapy, with the aim of advancing cGAS-STING signaling modulation as a key therapeutic strategy to reprogram TIME and overcome immunosuppression in antitumor treatment.

Keywords: Agonists; Combination therapy; Immune cells; Tumor immune microenvironment; cGAS-STING pathway; “Double-edged sword” effect.

Fig. 1

Schematic diagram of the cGAS-STING signaling pathway mechanism. The cGAS-STING pathway serves as the central regulatory network for cytoplasmic DNA-triggered immune responses. The cytosolic DNA sensor cGAS recognizes aberrant dsDNA, such as nuclear or mitochondrial DNA leakage caused by DNA viral infection, genomic instability, or radiotherapy-/chemotherapy-induced damage. This recognition induces conformational changes and activates cGAS. Activated cGAS synthesizes the second messenger molecule cGAMP from ATP and GTP. cGAMP binds to STING on the ER, triggering its conformational rearrangement and subsequent translocation from the ER to the Golgi apparatus. Following palmitoylation at the Golgi, STING recruits TBK1. TBK1 phosphorylates the C-terminal domain of STING and facilitates the recruitment of IRF3. Phosphorylated IRF3 dimerizes, translocates to the nucleus, and initiates the transcription of IFN-I, thereby activating downstream immune responses. Concurrently, the STING-TBK1 signaling axis activates IRF3 and NF-κB, respectively, to induce the expression of IFN-I and pro-inflammatory factors. Subsequently, IFN-I synergistically enhances immune responses through downstream signaling pathways. This cascade enhances immune processes such as antigen presentation, T cell activation, NK cell cytotoxicity, and antibody production. By bridging innate immunity and adaptive immunity, the cGAS-STING pathway reshapes the TIME into an immunostimulatory niche, offering a promising therapeutic target for cancer immunotherapy

Fig. 2

Mechanisms and Roles of cGAS-STING Pathway in Regulating DC Subpopulations for Antitumor Immunity. This figure illustrates the activation mechanisms of the cGAS-STING signaling pathway in different DC subpopulations (pDCs, cDC₁, and cDC₂) and its impact on tumor immunity. After tumor-derived DNA enters the cytoplasm of DCs, it activates the cGAS-STING pathway, inducing the production of IFN-I, which in turn promotes the maturation of DC subpopulations and T cell activation. Specifically, pDCs sense tumor-derived DNA through the intracellular cGAS-STING pathway, inducing the production of IFN-I and subsequently activating downstream immune responses. However, in the TIME, the STING signaling pathway in pDCs may be inhibited, leading to immune evasion. cDC₁ is a key cell type for initiating CD8⁺ T cell activation. The nanoparticle STING agonist PolySTING can specifically activate the STING-IFN-I signaling axis in cDC₁, enhancing its ability to cross-present antigens and driving CD8⁺ T cell-mediated antitumor immune responses. Additionally, IFN-I secreted by a subset of activated CD4⁺ T cells can enhance the activation capacity of cDC₁ towards CD8⁺ T cells. cDC₂ plays a central role in initiating the naïve CD4⁺ T cell immune response. The combination of the STING agonist ADU-S100 with anti-TIM-3 immune checkpoint blockade therapy can promote cDC₂ maturation and functional optimization, leading to enhanced CD4⁺ T cell activation and tumor infiltration

Fig. 3

Mechanism and effects of the cGAS-STING pathway in regulating antitumor immunity across T cell subsets. In CD8⁺ T cells, cGAS-STING activation enhances tumor infiltration by inducing IFN-I secretion and sustains stem-like properties through transcriptional factor TCF1 upregulation, thereby promoting the durable antitumor activity of CAR-T cells. Concurrently, IFN-I signaling inhibits the Akt pathway to drive their differentiation into cytotoxic effector cells. CD4⁺ T cells, as pivotal early responders, establish a pro-inflammatory microenvironment via IL-2 and IFN-γ secretion. Through the STING-IFN-β axis, they engage in bidirectional crosstalk with cDC₁, enhancing antigen presentation and priming CD8⁺ T cell activation.The cGAS-STING pathway also precisely regulates γδ T cells: In early tumors, cGAMP promotes the production of IFN-γ through the phosphorylation of Eomes, while in the immune microenvironment of advanced tumors, TGF-β inhibits the expression of STING protein in γδ T cells through epigenetic mechanisms, leading to functional exhaustion of γδ T cells. In treg cells, cGAS-STING activation disrupts immunosuppressive functions by downregulating IL-10 and TGF-β1 production, upregulating tumor MHC-I expression, and reversing immune tolerance. Moreover, STING-based vaccines further amplify T cell-mediated immunity by suppressing treg differentiation

Fig. 4

The cGAS-STING pathway regulates TAM polarization and anti-tumor immune effect. Within the TIME, M₁ TAMs, induced by IFN-γ or LPS, exhibit pro-inflammatory and tumoricidal properties. cGAS-STING activation drives M₁ polarization via the STING-IRF3-STAT1 axis, promoting T cell infiltration and enhancing anti-tumor immunity, albeit with a potential trade-off of inducing PD-L1 expression to foster immune suppression. For instance, in hepatocellular carcinoma, cGAS-STING activation enhances anti-PD-1 therapy efficacy, while in models of radiation-induced lung injury, STING-mediated upregulation of CCL2 recruits M₁ TAMs. In contrast, M₂ TAMs induced by IL-4/IL-13, secrete IL-10 and TGF-β, express high levels of CD206, and promote immune evasion. Moreover, STING agonists or nanoparticle-based drug delivery systems can reverse M₂ polarization, reprogramming these cells into an M₁-like phenotype to amplify anti-tumor effects. In glioblastoma and colorectal cancer liver metastasis models, STING activation suppresses M₂ functionality and reduces metastatic potential through IFN-I secretion or the IRG1-TFEB axis, respectively

Fig. 5

The cGAS-STING interaction network with other immune cells and its regulatory role in tumor immunity. In NK cells, activation of the cGAS-STING pathway (such as via eEF2K inhibition-induced DNA damage) drives the secretion of chemokines such as IL-2 and CXCL9, enhancing NK cell recruitment to tumors and cytotoxic activity. Intrinsic STING signaling in NK cells further suppresses tumor metastasis through autonomous IFN-γ production and synergistic cooperation with CD8⁺ T cells. For MDSCs, STING activation disrupts their differentiation and immunosuppressive functions by suppressing STAT3 signaling (such as via reduced IL-6/GM-CSF production). B cells exhibit dual regulation: The STING agonist cGAMP induces apoptosis of malignant B cells and activates T cell responses. However, excessive STING activation may trigger Breg amplification and inhibit NK cell cytotoxicity via IL-35

Fig. 6

Interactions and regulatory mechanisms between the cGAS-STING pathway and other components within the TIME. The interaction between the cGAS-STING pathway and IL-6 forms an immunosuppressive network: STING activation promotes IL-6 expression via the NF-κB-STAT3 axis. IL-6 subsequently enhances tumor cell survival, PD-L1 upregulation, and therapeutic resistance, while concurrently inhibiting the anti-tumor effects mediated by the IRF3/IFN-β pathway, thus acting as an “immune brake”. Furthermore, cGAS-STING signaling, mediated by IFN-I, regulates the spatiotemporal expression of CXCL9/10, reshaping the immune microenvironment to enhance T cell infiltration and effector functions. Targeted interventions within this network (such as combining STING agonists with IL-6 inhibitors or PD-1 blockade) can overcome immunosuppression and synergistically enhance anti-tumor efficacy. The diagram integrates key nodes, including costimulatory factors and immune checkpoints, illustrating the translational significance of IL-6 and IFN-I functioning respectively as bidirectional switches for “immune suppression” and “immune activation”

Fig. 7

Synergistic Mechanisms and Translational Potential of cGAS-STING Pathway Combined with Other Therapies. (A) Combination with Conventional Therapies: Radiotherapy and chemotherapy enhance antitumor immunity by indirectly activating the cGAS-STING pathway via DNA damage induction. For instance, radiotherapy combined with STING agonists promotes IFN-I secretion and T cell responses, suppresses metastasis, and mitigates adverse effects; Chemotherapeutic agents (e.g., cisplatin, 5-FU) synergize with STING activation to improve antigen presentation efficiency. (B) Combination with Cancer Vaccines: STING agonists serve as vaccine adjuvants by activating dual innate and adaptive immune responses, reshaping the TIME, enhancing vaccine-primed T cell infiltration, and overcoming resistance to PD-1 inhibitors. (C) Combination with ICIs: cGAS-STING signaling converts “cold tumors” into “hot tumors” by upregulating CXCL9/10 and PD-L1 expression, thereby promoting T cell infiltration and synergizing with PD-1/CTLA-4 inhibitors to amplify therapeutic efficacy. (D) Combination with CAR-T cell Therapy: STING activation recruits CAR-T cells to tumors via CXCL9/10 secretion, reverses the immunosuppressive microenvironment, and enhances CAR-T cell expansion and cytotoxicity