Therapeutic Activation of the cGAS-STING Pathway: Emerging Strategies for Antitumor Immunotherapy and Antiviral Defense
Key Insights
The cGAS-STING pathway (search) is a central cytosolic DNA-sensing mechanism that bridges innate and adaptive immunity, making it a promising target for cancer immunotherapy and antiviral defense.
Diverse activation strategies including metal ions (Mn²⁺), synthetic STING (search) agonists (CDNs, non-nucleotide agonists like MSA-2), endogenous DNA, and exogenous DNA are being developed to overcome delivery and bioavailability challenges.
Combining cGAS (search)-STING (search) activation with ROS-based therapies (PDT, SDT, RT, CDT), immune checkpoint blockade, CRISPR/Cas systems, and CAR-T therapy demonstrates synergistic antitumor efficacy in preclinical models.
The cyclic GMP-AMP synthase–stimulator of interferon genes (cGAS (search)-STING (search)) pathway has emerged as a central cytosolic DNA-sensing mechanism that plays a critical role in innate immunity and has become a key focus in antitumor immunotherapy and antiviral defense. As a fundamental pathway linking cytosolic DNA sensing to innate immune activation, cGAS-STING detects double-stranded DNA (dsDNA) from viral infections or tumor genomic instability and triggers type I interferon (IFN-I) responses, thereby bridging innate and adaptive immunity. This review integrates mechanistic, preclinical, and clinical evidence to delineate the roles of cGAS-STING as both a prognostic biomarker and a therapeutic target.
Mechanisms of the cGAS-STING Pathway (search)
cGAS (search) functions as a cytosolic dsDNA sensor activated in a sequence-independent manner. Under physiological conditions, host DNA is largely confined to the nucleus, and cytosolic dsDNA—originating from pathogens, necrotic cells, or damaged mitochondrial DNA (mtDNA)—is recognized as a danger signal. cGAS activation depends on dsDNA length and concentration, with longer DNA fragments requiring lower concentrations for activation. Upon DNA recognition, cGAS catalyzes the synthesis of cyclic GMP-AMP (cGAMP), which activates STING (search). Activated STING translocates from the endoplasmic reticulum (ER) to the Golgi via the ER–Golgi intermediate compartment (ERGIC), where it recruits TANK-binding kinase 1 (TBK1) and forms a signaling complex. This leads to activation of interferon regulatory factor 3 (IRF3) and nuclear factor κB (NF-κB), ultimately inducing IFN-I production and downstream immune responses.
Beyond the canonical pathway, non-canonical STING (search) signaling initiated by persistent endogenous DNA stress—including oncogene-driven replication stress, chromosomal instability (CIN), and micronucleus formation—can bias STING activation toward NF-κB-dominant inflammatory outputs rather than interferon-dominant immunity. This chronic signaling can drive immune exhaustion, tolerogenic myeloid reprogramming, and even promote epithelial–mesenchymal transition (EMT) and metastatic colonization.
Strategies to Activate the cGAS-STING Pathway (search)
Multiple classes of activators have been developed to efficiently activate the cGAS-STING pathway (search), each with distinct advantages and limitations.
Metal ions, particularly manganese (Mn²⁺) (search), significantly enhance the sensitivity of the cGAS-STING pathway (search) to dsDNA. Mn²⁺ binding to cytosolic cGAS (search) increases its dsDNA sensitivity and enzymatic activity, leading to increased cGAMP production even at low dsDNA concentrations. Although Mn²⁺ is not a direct agonist of STING (search), it has emerged as a promising adjuvant for cGAS-STING-based tumor immunotherapy. The combination of Mn²⁺ with anti-PD-1 (search) boosted anticancer efficacy in various tumor models. Additionally, zinc ions (Zn²⁺) released from bovine serum albumin-coated zinc sulfide nanoclusters (BSA@ZnS) in the tumor microenvironment activate the STING pathway and promote ROS generation, resulting in tumor cell death.
STING (search) agonists, particularly cyclic dinucleotides (CDNs) such as cGAMP, have demonstrated potential for enhancing anticancer activity. However, their therapeutic efficiency is limited by inefficient targeted delivery, low cytosolic transport efficiency, rapid clearance, and enzymatic degradation by ENPP1. To overcome these barriers, nanoparticles and cGAMP surrogates are being developed. Daniel Shae et al. developed STING-activating nanoparticles to enhance CDN delivery and amplify STING signal transduction in the TME and lymph nodes. James Moon's group developed "metalloimmunotherapy," wherein self-assembled nanomedicine incorporating Mn²⁺ and CDNs enhanced cellular uptake and strongly activated the cGAS-STING pathway (search), converting "cold tumors" to "hot tumors."
Non-nucleotide STING (search) agonists, such as diABZIs and MSA-2, exhibit higher efficiency and stronger biological activity than CDNs. MSA-2 has been proven to elicit a stronger immune stimulatory response. Chen et al. developed esterase-activatable prodrugs on the surface of MSA-2 incorporated into liposomal vesicles, enhancing targeted drug delivery and antitumor efficacy. Notably, DMXAA robustly activates murine STING but does not activate human STING, highlighting a species-selective limitation for clinical translation.
Endogenous DNA strategies leverage DNA damage-inducing chemotherapeutic agents. Doxorubicin (Dox) induces DNA damage in tumor cells, promoting cytosolic dsDNA release that activates STING (search). Platinum drugs form Pt-DNA complexes leading to DNA synthesis obstruction and STING pathway activation. Camptothecin (CPT) and cisplatin prodrugs similarly induce DNA damage and trigger antitumor immune responses. Mitochondrial DNA leakage, induced by agents such as Raddeanin A or mitochondria-targeting strategies, also activates the cGAS-STING pathway (search).
Exogenous DNA approaches include dsDNA-modified gold nanoparticles (Au-dsDNA) as STING (search) activators, tetrahedral DNA nanostructures (TDN) that efficiently activate the STING pathway, and DNAzymes—catalytic single-stranded DNA fragments with RNA-cleavage activity—that induce mtDNA release and activate innate immunity.
Combination with Antitumor Modalities
ROS-based antitumor therapies induce DNA damage and reprogram the TME, resulting in enhanced cGAS-STING pathway (search) activation. Photodynamic therapy (PDT) utilizes photosensitizers to convert molecular oxygen into ROS, causing mitochondrial damage and mtDNA release. Sonodynamic therapy (SDT) employs ultrasound to induce ROS generation, with MoOX nanoparticles stimulating DC maturation and activating the cGAS-STING pathway. Radiotherapy (RT) generates ROS that induces DNA damage, leading to dsDNA release and STING (search) pathway activation. Chemodynamic therapy (CDT) leverages Mn²⁺-mediated Fenton-type reactions to generate ROS and activate the cGAS-STING pathway.
Non-ROS-based therapies include photothermal therapy (PTT), which combines photothermal agents with STING (search) pathway-mediated immunotherapy for synergistic antitumor activity. Immune checkpoint blockade (ICB) therapy combined with cGAS (search)-STING activation elicits potent antitumor immunity, with nanovaccines composed of cGAMP and monophosphorylated lipid A (MPLA) enhancing responsiveness to anti-PD-1 (search) therapy. CRISPR/Cas systems enable precise editing of targets such as protein tyrosine phosphatase N2 (PTPN2) or PD-L1 (search), stimulating the cGAS-STING pathway (search) and boosting innate antitumor immunity. In CAR-T therapy, STING agonists enhance the formation of stem-like central memory CD8+ T cells and improve CAR-T cell efficacy. Optimized electroporation buffers that reduce cGAS–STING surveillance enable production of CAR-T cells with up to 20-fold higher yields and greater antitumor activity.
Antiviral Defense Applications
STING (search) agonists have emerged as a promising strategy for combating viral infections. Fan et al. reported an effective mRNA nanovaccine against SARS-CoV-2 (search), with Mn²⁺ serving as a STING activator encapsulated in ionizable lipid nanoparticles. Zhang et al. engineered STING agonist-armed lipid nanoparticles (SAL12-LNPs) that co-deliver SARS-CoV-2 Spike mRNA and a non-nucleotide STING agonist for synergistic antiviral immunization.
For influenza (search) viruses, single-component self-assembling protein nanoparticles (SApNPs) displaying M2e as a pan-influenza A vaccine loaded with STING (search) agonists induced robust and durable T-cell responses. A nanoSTING platform demonstrated broad-spectrum activity, with a single intranasal dose protecting against SARS-CoV-2 (search) variants and influenza strains, including oseltamivir-resistant viruses. Polymeric cGAMP microparticles conferred sustained protection against lethal influenza infection for up to a year in ferrets.
Clinical Translation and Challenges
Currently, most STING (search) agonists remain in preclinical or early clinical stages. While STING agonists enhance tumor immunotherapy and viral infection responses, their clinical use is hindered by high cost, poor delivery, and low efficacy. Critical challenges include optimizing delivery mechanisms, improving molecular stability, and refining dosing regimens. The dual role of cGAS (search)-STING signaling—where acute activation promotes antitumor immunity but chronic activation drives immune exhaustion, stromal remodeling, and tumor promotion—must be carefully managed.
Future priorities include development of more potent, selective STING (search) agonists with optimized pharmacokinetics and reduced systemic inflammatory toxicity, and rational combination strategies pairing cGAS (search)-STING activation with immune checkpoint blockade (anti-PD-1 (search)/PD-L1 (search), anti-CTLA-4) or ROS-based therapies that increase cytosolic DNA and tumor immunogenicity. These directions are likely to broaden the clinical utility of cGAS-STING-targeted therapies and improve patient outcomes.