TRIM56 inhibits M1 macrophage polarization and mitigates sepsis-induced acute lung injury via promoting STING ubiquitination-degradation.

RIG-I and STING are critical for mediating the RIG-I and cGAS-STING signaling pathways that guard against viral infection. Here, we report that ubiquitin-specific peptidase 39 (USP39) positively regulates the RIG-I and cGAS-STING pathways to induce antiviral innate immunity in vitro and in vivo. The USP39 deficiency impaired the antiviral immune response of macrophages, leading to low type I IFNs expression, and high RNA and (e.g., VSV, H1N1 PR8) DNA virus (e.g., HSV-1) replication. Moreover, USP39-deficient mice were more sensitive to VSV or HSV-1 infection than control mice. Conversely, USP39 overexpression promoted the antiviral immune response. Mechanistically, we found that USP39 regulates RIG-I protein expression by promoting pre-RIG-I mRNA splicing and maturation. In addition, we also revealed that USP39 interacts with and stabilizes STING protein by deubiquitinating K48-linked polyubiquitin of STING at K288. These data show that USP39 positively regulates RNA and DNA-virus-induced RIG-I and cGAS-STING signaling, respectively, by promoting post-transcriptional control of RIG-I and stabilization of STING. These data provide new insights and potential therapeutic targets to control viral infections.

The cGAS-STING signaling pathway is a crucial component of the innate immune system that detects aberrant cytosolic DNA, such as that derived from viruses or damaged cells, to activate downstream immune responses. Within this pathway, cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) serves as the essential second messenger linking DNA sensing to immune activation. Upon recognition of cytosolic DNA, cGAS synthesizes cGAMP, whose unique "mixed linkage" structure enables efficient binding to and activation of the STING protein on the endoplasmic reticulum, thereby inducing type I interferons and inflammatory cytokines. This review details cGAMP's biosynthesis, structural characteristics, and transport mechanisms, including efflux via ABCC1 and uptake by SLC19A1, underscoring its role as an intercellular "immune messenger." It also explores the dual functions of cGAMP in antiviral and antitumor immunity as well as in autoimmune and aging-related diseases, where it can either enhance immune defense or promote chronic inflammation. Therapeutically, cGAMP has been investigated as a vaccine adjuvant, a target for synthesis or degradation enzymes, and in nanoparticle-based delivery systems. However, challenges regarding its stability, delivery efficiency, and immunotoxicity remain, and future research should focus on real-time monitoring and tissue-specific modulation to advance cGAMP-based precision immunotherapeutics.

Hepatocellular carcinoma (HCC) is characterized by a highly immunosuppressive microenvironment, which contributes to its unfavorable clinical outcomes. Myeloid-derived suppressor cells (MDSCs) play a crucial role in this process. Schisandrin B (SchB) shows anti-tumor potential, but its mechanism in suppressing MDSCs remains unclear. This study investigates how SchB inhibits MDSCs accumulation and enhances anti-PD-1 therapy efficacy in HCC.SchB's efficacy and mechanism were investigated both invitro and invivo. Invitro, MTT, wound healing, EdU, colony formation, flow cytometry, ELISA, western blot, immunofluorescence, Co-IP, molecular dynamics (MD), and CETSA assays were employed to evaluate the therapeutic effects and mechanistic action of SchB on HCC. Invivo, a mouse HCC xenograft model was used to evaluate whether SchB could enhance the anti-tumor effect of PD-1 mAb and the potential mechanism.Mechanistically, SchB suppressed TRIM27 expression, disrupted the interaction between TRIM27 and STING, and enhanced STING/TBK1/IRF3 signaling, thereby suppressing the secretion of IL-6 and GM-CSF as well as the accumulation of MDSCs. SchB could directly bind to TRIM27 and downregulate its expression, thereby enhancing STING protein stability. Invivo, SchB effectively reduced MDSCs accumulation while promoting T cell recruitment, thereby augmenting the antitumor efficacy of PD-1 mAb therapy.SchB up-regulates STING by suppressing TRIM27, inhibits IL-6/GM-CSF secretion, and reduces MDSCs accumulation, indicating that SchB has the potential to be a promising candidate for PD-1 inhibitor therapy in HCC.

The cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway serves as a central innate immune signaling axis in host defense against DNA virus infections, and RNA viruses have also evolved diverse strategies to counteract this pathway. Encephalomyocarditis virus (EMCV), a zoonotic RNA virus, utilizes its 2C protein to antagonize RIG-I-like receptor-mediated type I interferon signaling and induce autophagic degradation of calcium binding and coiled-coil domain 2, thereby evading host antiviral immunity. However, the precise molecular mechanism by which EMCV 2C protein modulates the cGAS-STING pathway remains incompletely understood. Herein, we show that EMCV infection reduces the expression of cGAS and STING proteins, and its 2C protein significantly suppresses the production of IFN-β triggered by poly(dA:dT) or viral infection, as well as the mRNA expression of interferon-stimulated genes. Mechanistically, 2C protein binds to STING via its ATPase domain and facilitates K48-linked polyubiquitination and proteasomal degradation of STING, while dominantly interfering STING translocation to the Golgi apparatus and the formation of STING-TBK1-IRF3 complex, thereby blocking STING-mediated IFN-β signal transduction at multiple levels. This study reveals a novel mechanism by which the EMCV 2C protein suppresses the host antiviral response by targeting STING and promoting its ubiquitination and degradation. This finding deepens understanding of the immune evasion mechanism of EMCV and provides a theoretical foundation for the development of antiviral therapies targeting the 2C protein of picornaviruses.

WCN26-8983 ZAK Regulates STING Protein Homeostasis to Promote Renal Tubular Epithelial Cell Senescence and Drive AKI-to-CKD Progression

The human cytomegalovirus vMIA protein inhibits apoptosis and innate immune signaling in human Mueller cells.

The epigenetic silencing or remarkably diminished expression of STING in cancer cells, along with the structural and functional impairment of the endoplasmic reticulum (ER) and Golgi apparatus, represents a unique mechanism of tumor immune escape and poses an important challenge for STING-targeted therapies. Here, we develop a cell membrane-derived nanodisc system (ND-cGAMP-HP; HP, heparin), which is capable of presenting activated STING proteins in their native form by means of cell membrane-directed display and biological self-assembly techniques. It can directly introduce activated STING protein to tumor cells and circumvent the translocation process between the ER and Golgi apparatus, selectively activating the IFN-I signaling pathway without initiating the inflammation-related pathway NF-κB. ND-cGAMP-HP triggers potent cellular immune responses and remodels the tumor immune microenvironment. Moreover, it augments immune memory by promoting the differentiation of TCF1+ stem cell-like T cells. We thus manifest a strategy based on STING therapy that does not depend on the ER and Golgi apparatus pathways to activate the IFN-I pathway, for cancer immunotherapy.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nonstructural protein 15 (Nsp15) is a conserved uridine-specific endoribonuclease (EndoU) and is implicated in innate immune evasion, yet its precise molecular mechanism remains incompletely understood. Here, we demonstrate that Nsp15 limits antiviral innate immune responses in part by downregulating the cGAS–STING pathway. To investigate how Nsp15 antagonizes host innate immune responses, we engineered recombinant SARS-CoV-2 bearing WT or EndoU-inactive Nsp15 (H234A). Compared with the WT virus, the Nsp15-H234A mutant exhibited a 2-log decrease in peak viral titres in interferon (IFN)-competent A549-ACE2 cells, but not in their STAT1 knockout counterparts. This attenuation was partially reversed by STING knockout or STING inhibitors, highlighting STING’s involvement in Nsp15-driven immune evasion. Transcriptomic analyses revealed the upregulation of IFNs and IFN-stimulated genes in cells infected with the Nsp15-H234A mutant virus. Notably, cGAS and STING transcripts and proteins were suppressed during WT but not mutant virus infections – even in STAT1-deficient cells – suggesting that Nsp15 contributes directly to their downregulation. In vitro, Nsp15 targeted cGAS and STING transcripts in an EndoU activity-dependent manner, thereby reducing cGAS–STING-driven IFN-β and NF-κB reporter activation. Infection of Syrian hamsters confirmed that the Nsp15-H234A mutant virus replicated to lower titres in respiratory tissues and elicited stronger expression of innate immune-related genes. Collectively, these findings define a key strategy by which SARS-CoV-2 Nsp15 subverts the cGAS–STING pathway to facilitate viral replication and immune evasion and underscore Nsp15 EndoU activity as a potential target for future coronavirus antiviral or vaccine design.

The STING pathway plays a central role in immune activation; however, STING protein levels decline during the progression of various cancers, including lung cancer, thereby limiting the efficacy of immunotherapies. Our study uncovers a previously unrecognized mechanism whereby ISGylation stabilizes STING by preventing its autophagic degradation, thereby enhancing its immunostimulatory function. Moreover, we demonstrate USP18 as a negative regulator that removes ISGylation from STING, and identify Tanshinone IIA sulfonate (TST) as a potent USP18 inhibitor that enhances STING ISGylation and stabilizes STING protein levels. When combined with the STING agonist diABZi, TST exhibits a synergistic effect, eliciting a potent antitumor immune response by increased infiltration of NK1.1⁺ cells and pronounced suppression of tumor growth in lung cancer models. These findings underscore the therapeutic potential of targeting STING ISGylation, particularly in patients with low STING expression who often respond poorly to current STING-targeted therapies.

While numerous studies have reported that intratumor bacteria modulate tumor biological characteristics and therapeutic outcomes, the role of intracellular bacteria in gastrointestinal tumor (GIT) progression remains largely unexplored. Here, we show, through bioinformatics prediction and consecutive patient sample validation, that Stenotrophomonas is associated with tumor progression and poor prognosis in GIT. Using various murine tumor models, we find that intracellular Stenotrophomonas promotes GIT progression by decreasing IFNβ secretion and inhibiting MHC-II+ macrophages, thereby impairing the activity of effector CD8+ T cells. Mechanistically, Stenotrophomonas entry into tumor cells induces endoplasmic reticulum stress, degrades STING protein, and downregulates the type I IFN pathway response. Additionally, Stenotrophomonas contributes to resistance to immunotherapy in GIT, which can be reversed by levofloxacin. Our findings indicate that intracellular Stenotrophomonas within tumor cells plays an important role in promoting GIT progression and poor prognosis and could serve as a potential target to improve outcomes for patients with GIT.

Postoperative cognitive dysfunction (POCD) is a clinically significant complication in elderly patients, largely driven by surgery-induced neuroinflammation. The cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway, a crucial regulator of innate immunity, has been implicated in neuroinflammatory activation. This study investigated whether electroacupuncture (EA) improves POCD by modulating this pathway in aged rats. Aged male Sprague-Dawley rats were subjected to sevoflurane anesthesia and splenectomy to establish a POCD model. Animals were divided into sham, POCD, POCD+EA, and POCD+EA+cGAS inhibitor groups. The EA groups received stimulation at Baihui (Governor Vessel 20 (GV20)), Neiguan (Pericardium 6 (PC6)), and Zusanli (Stomach 36 (ST36)) acupoints. Cognitive function was evaluated using the Morris water maze, while hippocampal expression of cGAS-STING pathway components and downstream effectors—interferon regulatory factor 3 (IRF3), nuclear factor kappa B (NF-κB), and interleukin-1 beta (IL-1β)—was assessed by Western blot. Cellular localization was determined by immunofluorescence staining. Compared with the Sham group, rats in the POCD group showed significant impairments in spatial memory, accompanied by upregulated protein expression of cGAS, STING, NF-κB, IRF3, and IL-1β in the hippocampus. Upon pathway activation, cGAS and STING proteins were predominantly co-localized with neurons, and their fluorescence intensity in the hippocampus was markedly increased. These behavioral deficits and molecular alterations were partially reversed in both the POCD+EA and POCD+EA+inhibitor groups. Electroacupuncture alleviates POCD in aged rats by inhibiting hippocampal cGAS-STING pathway activation and reducing neuroinflammation, suggesting a promising non-pharmacological strategy for POCD management.

The TMEM173/STING protein is linked to therapeutic resistance in preclinical models of HNSCC (Head and neck squamous cell carcinoma). To evaluate STING as a biomarker, quantitative immunofluorescence (QIF) was performed on a tissue microarray (TMA) cohort of primary HNSCC (n = 72). Cytokeratin and 4,6-diamidino-2-phenylindole (DAPI) staining were used to differentiate between tumor or stromal compartments, and patient groups were dichotomized based on STING QIF scores. HNSCCs display variable STING protein levels in both tumor cell and stromal compartments. STING QIF score in tumor cells is associated with p16 positivity, with similar nonsignificant trends observed for stromal QIF values. In cohort 1, elevated STING levels in either tumor cells (P = .029) or stroma (P = .023) significantly improved DFS. These findings were validated in a second oropharyngeal HNSCC TMA cohort (n = 92) where borderline or significant differences in DFS were observed for elevated STING in tumor cells (P = .066) or the stroma (P = .028). A more detailed breakdown of failure patterns in cohort 2 revealed that elevated STING in tumor (P = .015) or stroma (P = .054) predicts local-regional control, and a trend for reduced distant failure was also observed for elevated stromal STING (P = .067). Local-regional recurrence was rare in HPV+ tumors and occurred only with low STING expression. In multivariate analysis, p16 was a significant predictor for local control, whereas elevated STING was of borderline significance (P = .051). These results suggest that STING protein levels in the tumor cell are a biomarker for predicting HNSCC local control after radiation therapy, and elevated STING in tumor stroma may be associated with a reduced risk of distant failure.

The cGAS-STING pathway has established itself as a critical innate immune pathway that has the ability to significantly affect tumor initiation and progression. The expression, methylation, immunological functions, and prognostic importance of cGAS-STING pathway-related genes in cervical squamous cancer (CESC) patients have not yet been thoroughly elucidated. First, we explored the expression of cGAS and STING in cervical carcinoma samples from TCGA by comparing the mRNA and protein levels of cGAS and STING in both TCGA cervical tumor patient samples and cervical tumor cell lines. Second, we examined the CD4+T and CD8+T cell infiltration in STING high and low samples and made Kaplan-Meier prognosis analysis of STING protein expression. Third, to verify the findings in TCGA public datasets, we retrospectively selected 40 cervical squamous carcinoma patients and 10 normal cervical tissues and evaluated cGAS and STING protein expression using immunohistochemistry (IHC). All patients have detailed clinical information, which includes age, FIGO stage, menstruation status, follow-up time, histology, tumor diameter, and serum tumor markers. In both cervical tumor patient samples and cell lines, we observed that cGAS is increased, whereas STING is decreased in tumors, which leads to decreased CD4+T and CD8+T cell infiltration and poor prognosis. Furthermore, the cGAS mRNA transcript showed a gradual increase and STING mRNA showed a decrease according to the tumor stage, tumor grade, metastasis status, and histology types. We confirmed the expression of cGAS and STING proteins in clinical cervical tumor samples using IHC. Mechanically, cGAS and STING showed different DNA methylation patterns, which might contribute to the differences in cGAS and STING mRNA and protein levels. Our work identified different expressions and methylation patterns of cGAS and STING in cervical cancer and their correlation with immune T cell infiltration and prognosis. More mechanistic study is needed to understand the cGAS-STING pathway in cervical squamous tumor.

Cyclic dinucleotide (CDN) signaling plays a pivotal role in bacterial physiology and host–pathogen interactions. Mycobacterium tuberculosis (Mtb) releases a cyclic dinucleotide phosphodiesterase (CdnP) in the macrophages, which hydrolyzes Mtb-derived 3′3′-c-di-AMP and 3′3′-c-di-GMP, and a host-derived 2′3′-cGAMP STING agonist, to evade the host's innate immune response mediated by the STING protein. Therefore, by inhibiting CdnP released into host cells, the STING pathway can be potentiated, leading to improved bacterial clearance, which represents a potential novel approach for anti-tuberculosis (anti-TB) therapy. Here we report ES-2′3′-cAAMP, an analog of the host-derived STING agonist 2′3′-cGAMP, in which the phosphodiester bond is modified and the base is replaced, binds to CdnP with a micromolar binding affinity and competes with CdnP's substrates – 3′3′-c-di-AMP and 3′3′-c-di-GMP – binding to CdnP. Significantly, CdnP's phosphodiesterase catalytic activity is inhibited by ES-2′3′-cAAMP. Furthermore, the CdnP–ES-2′3′-cAAMP complex structure reported here is the first structure of the CdnP complexed with CDN, revealing the unique pose of ES-2′3′-cAAMP in the catalytic pocket of CdnP that is inaccessible to catalytic residues and Mn2+ ions for its hydrolysis, and in parallel blocks the binding of the natural substrates of CdnP that explains the structural basis of CdnP's catalytic activity inhibition by the inhibitor. Additionally, 2′3′-cGAMP in the STING receptor and ES-2′3′-cAAMP in the CdnP adopted an identical horseshoe conformation, suggesting that ES-2′3′-cAAMP, or an analogue thereof, can bind to and stimulate STING, thus acting as a synthetic STING agonist. These combined structural and biochemical findings provide new mechanistic insights into the inhibition of Mtb CdnP and offer a novel approach to host-directed anti-TB therapies that aim to enhance the host's own immune responses rather than directly killing the pathogen, which may help to mitigate the problem of antibiotic resistance.

It is well established that tumor-associated macrophages (TAMs) are crucial to the development of tumors. Here, we looked into how SHP2 and M2/M1 macrophages affected gastric cancer. Bulk RNA-seq analysis was conducted using the GSE118916 dataset from the GEO database to screen for differentially expressed genes, and GO, KEGG enrichment analysis, and immune cell infiltration correlation analysis were performed. We also used PMA to differentiate THP-1 cells (M0 macrophages). To simulate the association between gastric adenocarcinoma and TAMS, M0 macrophages were co-cultured with AGS (human gastric adenocarcinoma cells). To mimic the advanced stage of gastric adenocarcinoma the co-cultured cells were cultured in 1% O2 low serum and low sugar. SHP2 overexpression, SHP2 knockdown, and SP1 inhibitor BDR4 inhibitor JQ-1 were used to examine the effects of SHP2, SP1, and BRD4 on macrophage polarization and cancer cell death, migration, and invasion. Bulk RNA-seq analysis revealed that differentially expressed genes in gastric cancer were mainly enriched in extracellular matrix organization and adhesion-related pathways. Macrophages showed significant positive correlation with activated dendritic cells in the immune infiltration analysis. SHP2 overexpression inhibited the expression of p-P38, p-ERK1/2, p-SP1, BRD4, FOXM1, STING, NRLP3, and inflammation- and ROS-related cytokines IL-1β, TNFα, and MDA, and SOD, and the expression of M2 polarization-associated proteins, Arg-1 and Cathepsin K. The aforementioned proteins' expression was greatly enhanced by SHP2. the aforementioned proteins' expression. P-SP1 was significantly inhibited under the action of SP1 inhibitor, in addition, STING, NRLP3 and ROS-related proteins IL-1β, TNFα and MDA, SOD expression, M2 polarization-related proteins Arg-1, Cathepsin K. The expression of the aforementioned proteins was markedly decreased by the combination of SP1 inhibitor and BRD4 inhibitor. Additionally, there was an increase in cancer cell invasion, migration, and death. SHP2 in TAMs promotes gastric adenocarcinoma survival by inhibiting P38/ erk1 /SP1/BRD4/STING-induced inflammation and ROS.

Switch/sucrose nonfermentable (SWI/SNF) complex mutations have been reported in Kirsten rat sarcoma viral oncogene homologue (KRAS)-mutant non-small cell lung cancer (NSCLC), but the influence on immune checkpoint blockade (ICB) outcomes is debated and needs to be investigated further. Genomic pathogenic alterations (GPAs) in SWI/SNF genes were identified via OncoKB, COSMIC and PolyPhen-2. NSCLC patients (NSCLCs) were classified according to alterations in six SWI/SNF genes (ARID1A, ARID1B, ARID2, PBRM1, SMARCA4 and SMARCB1). Cell lines used for differentially expressed gene analyses were subjected to RNA sequencing (RNA-seq) and Western blotting to validate protein expression levels. Protein expression in tumour specimens was detected by immunohistochemistry (IHC). In 2660 NSCLCs, 15.0% (401/2660) had SWI/SNF GPAs. A total of 23.1% (69/299) of the EGFRwtALKwt NSCLCs and 27.8% (25/90) of the STK11wtKEAP1wtKRASmut NSCLCs who received ICB had SWI/SNF GPAs. Among all the ICB-treated NSCLCs, progression-free survival (PFS) was not significantly different between SWI/SNF-wild type (wt) and SWI/SNF-mutant (mut) NSCLCs. However, GPAs in the SWI/SNF complex in KRAS-mut ICB-treated NSCLCs were associated with poorer clinical outcomes. Patients with ARID1A/ARID1B/ARID2/PBRM1 mutations had a significantly shorter PFS (2.7 vs. 6.5m, HR = 2.44 [95% CI 1.31-4.54], P = 0.004) than did those with SWI/SNF-wt. Among STK11wtKEAP1wtKRASmut NSCLCs, all SWI/SNF-mut (4.9 vs. 9.1m, HR = 2.03 [95% CI 1.07-3.86], P = 0.029) and ARID1A/ARID1B/ARID2/PBRM1-mut (3.2 vs. 9.1m, HR = 2.68 [95% CI 1.33-5.41], P = 0.004) NSCLCs had significantly shortened PFS, and ARID1A/ARID1B/ARID2-mut NSCLCs also tended to have a shorter overall survival (OS) (12.2 vs. 29.9m, HR = 2.20 [95% CI 0.98-4.91], P = 0.052). Furthermore, RNA-seq and Western blot analyses confirmed that the deletion of SWI/SNF genes resulted in downregulated STING expression in NSCLC cell lines. And IHC analysis of patient tumour samples confirmed that the loss of SWI/SNF protein expression was associated with decreased STING protein levels. Notably, downregulated STING protein expression was observed in KRAS-mut NSCLC patients who did not benefit from ICB treatment. In KRAS-mut NSCLCs with or without STK11/KEAP1 mutations, the GPAs in the DNA-binding genes ARID1A/ARID2 affected the outcomes of immunotherapy, possibly through the downregulation of STING expression.

Neuroinflammation is closely linked to the pathogenesis of Alzheimer's disease (AD) and the associated deficits in learning and memory. Microglial activation serves as a central mediator of this inflammatory response. While previous studies have shown that aerobic exercise exerts protective effects by suppressing microglial activation and attenuating neuroinflammation, the underlying mechanisms remain largely unclear. Notably, INPP5D, an immunoregulatory factor predominantly expressed in microglia, is closely associated with aberrant microglial activation and cognitive decline in AD. Elucidating the role of INPP5D in microglial regulation and anti-inflammatory processes during aerobic exercise may uncover novel therapeutic targets for early cognitive impairments in AD. Male 5 ×FAD mice underwent treadmill training to evaluate the effects of aerobic exercise. Before training, recombinant adeno-associated virus (rAAV) encoding INPP5D was injected into the hippocampus to induce overexpression. Treadmill exercise commenced 21 days post-injection, once viral expression was established. Viral expression was confirmed via immunofluorescence staining and Western blot analysis. Cognitive function was assessed using the novel object recognition test and the Morris water maze (MWM). Hippocampal Aβ deposition was examined through immunohistochemical staining. Levels of neuroinflammatory markers in the hippocampus and serum were quantified using enzyme-linked immunosorbent assay (ELISA). Microglial activation was evaluated by immunofluorescence staining. The interaction between INPP5D and TREM2, as well as TREM2 expression, was analyzed using co-immunoprecipitation and Western blotting. Additionally, the expression of cGAS and STING proteins was determined by Western blotting. Aerobic exercise improved learning and memory impairments in 5 ×FAD mice through the regulation of INPP5D, leading to reduced Aβ deposition in the hippocampus and attenuation of neuroinflammation in both the hippocampus and serum. It also modulated microglial activation in the hippocampus. Moreover, aerobic exercise upregulated TREM2 expression by regulating INPP5D and suppressed activation of the cGAS-STING inflammatory pathway. This study demonstrates that aerobic exercise alleviates neuroinflammation and improves early learning and memory impairments in AD by modulating microglial activity through INPP5D. These findings offer new insights into the underlying mechanisms by which aerobic exercise mitigates neuroinflammation in AD, highlighting its therapeutic potential.

Association of YY1 with STING activation and the inflammatory response during early muscle injury repair.

Objective: To explore the effects of quercetin on autophagy and proliferation in HBV-positive liver cancer HCCLM3 cells based on STING signaling and its underlying mechanism. Methods: HCCLM3 cells were treated with quercetin (50 μmol/L or 100 μmol/L), designated as the 50 μmol/L group and 100 μmol/L group, respectively. The inhibitory effect of quercetin on HCCLM3 cells was detected using the CCK-8 method. A scratch assay was conducted to assess the impact of quercetin on the migration ability of HCCLM3 cells. A CCK8 and ROS kit was used to detect the effect of quercetin on the levels of reactive oxygen species in HCCLM3 cells. Western blotting was employed to measure the effect of quercetin on the expression of STING signaling and autophagy-related proteins in HCCLM3 cells. RNA interference technology was used to assess the effects of STING signaling inhibition on the expression of autophagy-related proteins and reactive oxygen species levels in HCCLM3 cells. The combined effects of STING activators and quercetin on HCCLM3 cell proliferation and autophagy were evaluated. The t-test was used to detect data differences between two groups, while ANOVA was employed for comparisons among multiple groups, followed by the SNK-q test for further pairwise comparisons. Results: Compared with the control group, quercetin (50 μmol/L and 100 μmol/L groups) significantly inhibited HCCLM3 cell survival activity in a dose-dependent manner (control group: 100%; 50 μmol/L group: 75.25%; 100 μmol/L group: 50.36%, P<0.01 ). Quercetin inhibited HCCLM3 cell migration in a dose-dependent manner (>2 h, control group: 187.16 μm; 50 μmol/L group: 145.22 μm; 100 μmol/L group: 88.21 μm, P<0.01), which significantly increased intracellular reactive oxygen species (ROS) levels in HCCLM3 cells (control group: 1.00; 50 μmol/L group: 1.565; 100 μmol/L group: 2.175, P<0.01). The phosphorylation level of STING was significantly increased (P<0.01), and the expression of autophagy-related protein microtubule-related protein 1A/1B light chain 3 (LC3) protein was significantly promoted (P<0.01). Compared with the quercetin group, the cell viability of the small interfering-STING+quercetin group was increased (quercetin group: 56.3%; small interfering-STING+quercetin group: 85.7%, P<0.05), while the expression of autophagy-related protein LC3 was decreased. Compared with the quercetin group, the cell viability of the quercetin+STING activator group was further decreased (quercetin group: 56.7%; quercetin+STING activator group: 35.4%, P<0.01), and the expression levels of STING and autophagy protein LC3 were significantly increased (P<0.05). Conclusions: STING signaling-regulated cell autophagy mediates the inhibitory effect of quercetin on the proliferation of HCCLM3 cells, and this effect is enhanced after administration of the STING agonist.