DNA damage induces STING mediated IL-6-STAT3 survival pathway in triple-negative breast cancer cells and decreased survival of breast cancer patients

Investigating the impact of STING pathway activation on breast cancer treatment outcomes: development and validation of a prognostic model

Introduction

Breast cancer (BRCA) is a significant cause of cancer-associated mortality across the globe. Current therapeutic approaches face challenges such as drug resistance and metastasis. Immune signaling is triggered by chromosomal instability (CIN) generates misplaced DNA structures that activate the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway, triggering. Studies have linked STING activation to BRCA treatment.

Methods

The bulk RNA-seq data for patients with BRCA were collected from the TCGA-BRCA cohort, GSE20685, and GSE96058 cohorts. STING pathway-related genes (SRGs) were obtained from the Reactome database. Differentially expressed genes were analyzed using the limma package. Immune cell infiltration was analyzed using the IOBR package. Gene Ontology biological processes, Kyoto Encyclopedia of Genes and Genomes pathways, and cancer hallmark pathways were analyzed using the MSigDB database. Prognostic models were prepared using the least absolute shrinkage and selection operator and multiple-factor Cox regression analysis. Single-cell analysis was performed using the Seurat and SCP pipeline.

Results

The expression patterns and clinical relevance of SRGs were analyzed in patients with BRCA. Transcriptional differences in the SRGs were observed between normal and tumorous tissues, with global down-regulated STING1 and up-regulated TBK1 in BRCA tissue. Tumor tissues were classified through consensus clustering analysis into two distinct groups, with differences in clinical characteristics and immune infiltration. A prognostic model related to the differences in STING pathway activity-high prognostic stratification potency-was developed and validated. Correlation analysis revealed suppressed overall immune activation in patients with BRCA having higher risk scores. Gemcitabine had a more favorable outcome in the low-risk group. The activity of the prognostic model at the single-cell level was confirmed through single-cell analysis, particularly in CD8 T cells and intratumor natural killer cells.

Conclusion

A STING pathway-related prognostic model developed and validated and the model could accurately predict BRCA patient outcomes. These findings have important implications for the personalized treatment and management of patients with BRCA.

MARCH1 negatively regulates TBK1-mTOR signaling pathway by ubiquitinating TBK1

BACKGROUND

TBK1 positively regulates the growth factor-mediated mTOR signaling pathway by phosphorylating mTOR. However, it remains unclear how the TBK1-mTOR signaling pathway is regulated. Considering that STING not only interacts with TBK1 but also with MARCH1, we speculated that MARCH1 might regulate the mTOR signaling pathway by targeting TBK1. The aim of this study was to determine whether MARCH1 regulates the mTOR signaling pathway by targeting TBK1.

METHODS

The co-immunoprecipitation (Co-IP) assay was used to verify the interaction between MARCH1 with STING or TBK1. The ubiquitination of STING or TBK1 was analyzed using denatured co-immunoprecipitation. The level of proteins detected in the co-immunoprecipitation or denatured co-immunoprecipitation samples were determined by Western blotting. Stable knocked-down cells were constructed by infecting lentivirus bearing the related shRNA sequences. Scratch wound healing and clonogenic cell survival assays were used to detect the migration and proliferation of breast cancer cells.

RESULTS

We showed that MARCH1 played an important role in growth factor-induced the TBK1- mTOR signaling pathway. MARCH1 overexpression attenuated the growth factor-induced activation of mTOR signaling pathway, whereas its deficiency resulted in the opposite effect. Mechanistically, MARCH1 interacted with and promoted the K63-linked ubiquitination of TBK1. This ubiquitination of TBK1 then attenuated its interaction with mTOR, thereby inhibiting the growth factor-induced mTOR signaling pathway. Importantly, faster proliferation induced by MARCH1 deficiency was weakened by mTOR, STING, or TBK1 inhibition.

CONCLUSION

MARCH1 suppressed growth factors mediated the mTOR signaling pathway by targeting the STING-TBK1-mTOR axis.

NF-κB signaling in therapy resistance of breast cancer: Mechanisms, approaches, and challenges

Breast cancer is the most common type of cancer and is the second leading cause of cancer-related mortality in women. Chemotherapy, targeted therapy, endocrine therapy, and radiotherapy are all effective in destroying tumor cells, but they also activate the defense and protection systems of cancer cells, leading to treatment resistance. Breast cancer is characterized by a highly inflammatory tumor microenvironment. The NF-κB pathway is essential for connecting inflammation and cancer, as well as for tumor growth and therapy resistance. An increase in NF-κB signaling boosts the growth potential of breast cancer cells and facilitates the spread of tumors to bone, lymph nodes, lungs, and liver. This review focuses on the mechanisms by which chemotherapy, targeted therapy, endocrine therapy, and radiotherapy induce breast cancer resistance through NF-κB signaling. Additionally, we investigate therapeutic regimens, including single agents or in combination with target inhibitors, plant extracts, nanomedicines, and miRNAs, that have been reported in clinical trials, in vivo, and in vitro to reverse resistance. In particular, NF-κB inhibitors combined with tamoxifen were shown to significantly increase the sensitivity of breast cancer cells to tamoxifen. Combination therapy of miRNA-34a with doxorubicin was also found to synergistically inhibit the progression of doxorubicin-resistant breast cancer by inhibiting Notch/NF-κB signaling.

Stimulator of Interferon Genes Protein (STING) Expression in Cancer Cells: A Tissue Microarray Study Evaluating More than 18,000 Tumors from 139 Different Tumor Entities

Stimulator of interferon genes protein (STING) activates the immune response in inflammatory cells. STING expression in cancer cells is less well characterized, but STING agonists are currently being evaluated as anticancer drugs. A tissue microarray containing 18,001 samples from 139 different tumor types was analyzed for STING by immunohistochemistry. STING-positive tumor cells were found in 130 (93.5%) of 139 tumor entities. The highest STING positivity rates occurred in squamous cell carcinomas (up to 96%); malignant mesothelioma (88.5%-95.7%); adenocarcinoma of the pancreas (94.9%), lung (90.3%), cervix (90.0%), colorectum (75.2%), and gallbladder (68.8%); and serous high-grade ovarian cancer (86.0%). High STING expression was linked to adverse phenotypes in breast cancer, clear cell renal cell carcinoma, colorectal adenocarcinoma, hepatocellular carcinoma, and papillary carcinoma of the thyroid (p < 0.05). In pTa urothelial carcinomas, STING expression was associated with low-grade carcinoma (p = 0.0002). Across all tumors, STING expression paralleled PD-L1 positivity of tumor and inflammatory cells (p < 0.0001 each) but was unrelated to the density of CD8+ lymphocytes. STING expression is variable across tumor types and may be related to aggressive tumor phenotype and PD-L1 positivity. The lack of relationship with tumor-infiltrating CD8+ lymphocytes argues against a significant IFN production by STING positive tumor cells.

Experimental congenital diaphragmatic hernia features an alteration of DNA sensing targets cGAS and STING

BACKGROUND

The pathogenesis of congenital diaphragmatic hernia (CDH) depends on multiple factors. Activation of the DNA-sensing cyclic-GMP-AMP-synthase (cGAS) and Stimulator-of-Interferon-Genes (STING) pathway by double-stranded DNA (dsDNA) links environmental stimuli and inflammation. We hypothesized that nitrofen exposure alters cGAS and STING in human bronchial epithelial cells and fetal rat lungs.

METHODS

We used the Quant-IT™-PicoGreen™ assay to assess dsDNA concentration in BEAS-2B cells after 24 h of nitrofen-exposure and performed immunofluorescence of cGAS/STING. We used nitrofen to induce CDH and harvested control and CDH lungs at embryonic day E15, E18 and E21 for cGAS/STING immunofluorescence, RT-qPCR and RNA-Scope™ in-situ-hybridization (E18, E21).

RESULTS

We found a higher concentration of dsDNA following nitrofen treatment. Nitrofen-exposure to BEAS-2B cells increased cGAS and STING protein abundance. cGAS abundance was higher in nitrofen lungs at E15, E18 and E21. RNA-Scope in-situ-hybridization showed higher cGAS and STING expression in E18 and E21 lungs. RT-qPCR revealed higher mRNA expression levels of STING in E21 nitrofen-induced lungs.

CONCLUSION

Our data suggest that nitrofen-exposure increases dsDNA content which leads to stimulation of the cGAS/STING pathway in human BEAS-2B cells and the nitrofen rat model of CDH. Consequently, DNA sensing and the cGAS-STING-pathway potentially contribute to abnormal lung development in CDH.

IMPACT STATEMENT

We found an alteration of DNA sensing targets cGAS and STING in human BEAS-2B cells and experimental congenital diaphragmatic hernia with higher protein abundance and mRNA expression in cells and lung sections of nitrofen-treated rat pups. This is the first study to investigate DNA sensing, a potential link between environmental stimuli and inflammation, in experimental CDH. Our study extends the knowledge on the pathogenesis of experimental CDH.

circATAD2 mitigates CD8+ T cells antitumor immune surveillance in breast cancer via IGF2BP3/m6A/PD-L1 manner

Immune surveillance and chemotherapy sensitivity play critical functions in the tumorigenesis of breast cancer (BC). Emerging findings have indicated that circular RNA (circRNA) and N6-methyladenosine (m6A) both participate in the BC tumorigenesis. Here, present study aimed to investigate the roles of m6A-modified circATAD2 on BC and explore better understanding for BC precision therapeutic. Results reported that m6A-modifid circRNA (m6A-circRNA) microarray revealed the m6A-circRNA landscape in BC. M6A-modifid circATAD2 upregulated in BC samples and was closely correlated to poor prognosis. Functionally, circATAD2 promoted the immune evasion of BC cells and reduced the CD8+ T cells' killing effect. Mechanistically, MeRIP-seq unveiled the m6A modification in the 3'-UTR of PD-L1 mRNA, which was bound by circATAD2 and recognized by m6A reader IGF2BP3 to enhance PD-L1 mRNA stability and expression. In summary, these findings revealed the circATAD2/m6A/IGF2BP3/PD-L1 axis in BC immune surveillance, suggesting the potential that circATAD2 as a potential target for PD-L1-mediated BC.

Chemotherapy-initiated cysteine-rich protein 61 decreases acute B-lymphoblastic leukemia chemosensitivity

PURPOSE

Chemoresistance is a major challenge for acute lymphoblastic leukemia (ALL) treatment. Cysteine-rich protein 61 (Cyr61) plays an important role in drug resistance modulation of tumor cells, and Cyr61 levels are increased in the bone marrow of patients with ALL and contribute to ALL cell survival. However, the effect of Cyr61 on B cell acute lymphoblastic leukemia (B-ALL) cell chemosensitivity and the regulatory mechanisms underlying Cyr61 production in bone marrow remain unknown.

METHODS

Nalm-6 and Reh human B-ALL cell lines were used in this study. Cyr61 levels were assessed using quantitative real-time PCR (qRT-PCR), western blot analysis, and enzyme-linked immunosorbent assay. The effect of Cyr61 on B-ALL cell chemosensitivity to daunorubicin (DNR) was evaluated using cell viability and flow cytometry analyses. The regulatory mechanisms of Cyr61 production in bone marrow were examined using qRT-PCR and western blot analysis.

RESULTS

Cyr61 knockdown and overexpression increased and decreased the chemosensitivity of B-ALL cells to DNR, respectively. Cyr61 attenuated chemotherapeutic drug-induced apoptosis by upregulating B cell lymphoma-2. Notably, DNR induced DNA damage response and increased Cyr61 secretion in B-ALL cells through the ataxia telangiectasia mutated (ATM)-dependent nuclear factor kappa B pathway.

CONCLUSION

DNR induces Cyr61 production in B-ALL cells, and increased Cyr61 levels reduce the chemosensitivity of B-ALL cells. Consequently, targeting Cyr61 or related ATM signaling pathway may present a promising treatment strategy to enhance the chemosensitivity of patients with B-ALL.

The cytosolic DNA-sensing cGAS-STING pathway in neurodegenerative diseases

BACKGROUND

With the widespread prevalence of neurodegenerative diseases (NDs) and high rates of mortality and disability, it is imminent to find accurate targets for intervention. There is growing evidence that neuroimmunity is pivotal in the pathology of NDs and that interventions targeting neuroimmunity hold great promise. Exogenous or dislocated nucleic acids activate the cytosolic DNA sensor cyclic GMP-AMP synthase (cGAS), activating the stimulator of interferon genes (STING). The activated STING triggers innate immune responses and then the cGAS-STING signaling pathway links abnormal nucleic acid sensing to the immune response. Recently, numerous studies have shown that neuroinflammation regulated by cGAS-STING signaling plays an essential role in NDs.

AIMS

In this review, we summarized the mechanism of cGAS-STING signaling in NDs and focused on inhibitors targeting cGAS-STING.

CONCLUSION

The cGAS-STING signaling plays an important role in the pathogenesis of NDs. Inhibiting the cGAS-STING signaling may provide new measures in the treatment of NDs.

Sudocetaxel Zendusortide (TH1902) triggers the cGAS/STING pathway and potentiates anti-PD-L1 immune-mediated tumor cell killing

The anticancer efficacy of Sudocetaxel Zendusortide (TH1902), a peptide-drug conjugate internalized through a sortilin-mediated process, was assessed in a triple-negative breast cancer-derived MDA-MB-231 immunocompromised xenograft tumor model where complete tumor regression was observed for more than 40 days after the last treatment. Surprisingly, immunohistochemistry analysis revealed high staining of STING, a master regulator in the cancer-immunity cycle. A weekly administration of TH1902 as a single agent in a murine B16-F10 melanoma syngeneic tumor model demonstrated superior tumor growth inhibition than did docetaxel. A net increase in CD45 leukocyte infiltration within TH1902-treated tumors, especially for tumor-infiltrating lymphocytes and tumor-associated macrophages was observed. Increased staining of perforin, granzyme B, and caspase-3 was suggestive of elevated cytotoxic T and natural killer cell activities. Combined TH1902/anti-PD-L1 treatment led to increases in tumor growth inhibition and median animal survival. TH1902 inhibited cell proliferation and triggered apoptosis and senescence in B16-F10 cells in vitro, while inducing several downstream effectors of the cGAS/STING pathway and the expression of MHC-I and PD-L1. This is the first evidence that TH1902 exerts its antitumor activity, in part, through modulation of the immune tumor microenvironment and that the combination of TH1902 with checkpoint inhibitors (anti-PD-L1) could lead to improved clinical outcomes.

Gold Nanoparticles Downregulate IL-6 Expression/Production by Upregulating microRNA-26a-5p and Deactivating the RelA and NF-κBp50 Transcription Pathways in Activated Breast Cancer Cells

MicroRNAs (miRNAs) are involved in the modulation of pathogenic genes by binding to their mRNA sequences' 3' untranslated regions (3'UTR). Interleukin-6 (IL-6) is known to promote cancer progression and treatment resistance. In this study, we aimed to explore the therapeutic effects of gold nanoparticles (GNP) against IL-6 overexpression and the modulation of miRNA-26a-5p in breast cancer (BC) cells. GNP were synthesized using the trisodium citrate method and characterized through UV-Vis spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM). To predict the binding of miR-26a-5p in the IL-6 mRNA's 3'UTR, we utilized bioinformatics algorithms. Luciferase reporter clone assays and anti-miRNA-26a-5p transfection were employed to validate the binding of miR26a-5p in the IL-6 mRNA's 3'UTR. The activity of RelA and NF-κBp50 was assessed and confirmed using Bay 11-7082. The synthesized GNP were spherical with a mean size of 28.3 nm, exhibiting high stability, and were suitable for BC cell treatment. We found that miR-26a-5p directly regulated IL-6 overexpression in MCF-7 cells activated with PMA. Treatment of MCF-7 cells with GNP resulted in the inhibition of IL-6 overexpression and secretion through the increase of miR26a-5p. Furthermore, GNP deactivated NF-κBp65/NF-κBp50 transcription activity. The newly engineered GNP demonstrated safety and showed promise as a therapeutic approach for reducing IL-6 overexpression. The GNP suppressed IL-6 overexpression and secretion by deactivating NF-κBp65/NF-κBp50 transcription activity and upregulating miR-26a-5p expression in activated BC cells. These findings suggest that GNP have potential as a therapeutic intervention for BC by targeting IL-6 expression and associated pathways.

The Role of the Toll-like Receptor 2 and the cGAS-STING Pathways in Breast Cancer: Friends or Foes?

Breast cancer stands as a primary malignancy among women, ranking second in global cancer-related deaths. Despite treatment advancements, many patients progress to metastatic stages, posing a significant therapeutic challenge. Current therapies primarily target cancer cells, overlooking their intricate interactions with the tumor microenvironment (TME) that fuel progression and treatment resistance. Dysregulated innate immunity in breast cancer triggers chronic inflammation, fostering cancer development and therapy resistance. Innate immune pattern recognition receptors (PRRs) have emerged as crucial regulators of the immune response as well as of several immune-mediated or cancer cell-intrinsic mechanisms that either inhibit or promote tumor progression. In particular, several studies showed that the Toll-like receptor 2 (TLR2) and the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathways play a central role in breast cancer progression. In this review, we present a comprehensive overview of the role of TLR2 and STING in breast cancer, and we explore the potential to target these PRRs for drug development. This information will significantly impact the scientific discussion on the use of PRR agonists or inhibitors in cancer therapy, opening up new and promising avenues for breast cancer treatment.

Type-I interferon pathway and DNA damage accumulation in peripheral blood of patients with psoriatic arthritis

Objectives

The abnormal DNA damage response is associated with upregulation of the type-1 interferon (IFN-I) pathway in certain rheumatic diseases. We investigated whether such aberrant mechanisms operate in psoriatic arthritis (PsA).

Methods

DNA damage levels were measured by alkaline comet assay in peripheral blood mononuclear cells from 52 PsA patients and age-sex-matched healthy individuals. RNA expression of IFIT1, MX1 and IFI44, which are selectively induced by IFN-I, was quantitated by real-time polymerase chain reaction and their composite normalized expression resulted in IFN-I score calculation. RNA expression of IL1β, IL6, TNF, IL17A and IL23A was also assessed in PsA and control subgroups.

Results

In PsA, DNA damage accumulation was increased by almost two-fold compared to healthy individuals (olive tail moment arbitrary units, mean ± SD; 9.42 ± 2.71 vs 4.88 ± 1.98, p<0.0001). DNA damage levels significantly correlated with serum C-Reactive-protein and IL6 RNA expression in PBMCs. Despite increased DNA damage, the IFN-I score was strikingly lower in PsA patients compared to controls (-0.49 ± 6.99 vs 4.24 ± 4.26; p<0.0001). No correlation was found between IFN-I pathway downregulation and DNA damage. However, the IFN-I score in a PsA subgroup was lower in those patients with higher IL1β expression, as well as in those with higher TNF/IL23A PBMCs expression.

Conclusion

DNA damage in PsA correlates with measures of inflammation but is not associated with the IFN-I pathway induction. The unexpected IFN-I downregulation, albeit reminiscent to findings in experimental models of spondyloarthritis, may be implicated in PsA pathogenesis and explained by operation of other cytokines.

Targeting STING in cancer: Challenges and emerging opportunities

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway is a key pathway through which the host regulates immune responses by recognizing cytoplasmic double-stranded DNA of abnormal origin, and it plays an important role in tumor growth as well as metastasis, with relevant molecular details constantly being explored and updated. The significant immunomodulatory effects make STING an attractive target for cancer immunotherapy, and STING agonists have been receiving great attention for their development and clinical translation. Despite exciting results in preclinical work, the application of STING agonists to cancer therapy remains challenging due to their poor pharmacokinetic and physicochemical properties, as well as toxic side effects they produce. Here, we summarize the dichotomous role of cGAS-STING in cancer and discuss the limitations of cancer immunotherapy based on STING activation as well as feasible strategies to overcome them to achieve tumor regression.

Therapeutic potential of single-nucleotide polymorphism-mediated interleukin-6 receptor blockade in cancer treatment: A Mendelian randomization study

Background

Interleukin-6 (IL-6) is a crucial member of the cytokine network and plays a pivotal role in the pathogenesis of various diseases, including cancer. IL-6 receptor (IL-6R) blockade is widely employed as a therapeutic strategy; however, its efficacy in anticancer therapy remains ambiguous.

Methods

An inverse variance-weighted Mendelian randomization (MR) analysis was conducted to assess the causal effects exerted by IL-6R blockade in remediating cancer. Drug-targeted single-nucleotide polymorphisms (SNPs) were introduced within 300 kb of the IL-6R gene. An instrumental variable comprising 26 SNPs represented IL-6 signaling downregulation and C-reactive protein level reduction. Datasets pertaining to the 33 types of cancer investigated in this study were acquired from the FinnGen genome-wide association study.

Results

The selected instrumental variable lowered fibrinogen levels, confirming its ability to mimic IL-6R blockade. IL-6R blockade exhibited therapeutic effects on five different cancer types documented in the FinnGen database (N = 334,364, including 76,781 cancer patients): bladder (odds ratios (OR) = 0.563), laryngeal (OR = 0.293), eye (OR = 0.098), gallbladder (OR = 0.059), and myeloid leukemia (OR = 0.442); however, it simultaneously elevated the risk of developing basal cell carcinoma (OR = 1.312) and melanoma (OR = 1.311). Sensitivity analyses did not alter the primary results.

Conclusion

Therefore, this study aimed to evaluate the potential and efficacy of SNP-based IL-6R blockade in treating cancer.

Cancer cell-specific cGAS/STING Signaling pathway in the era of advancing cancer cell biology

Pattern-recognition receptors (PRRs) are critical to recognizing endogenous and exogenous threats to mount a protective proinflammatory innate immune response. PRRs may be located on the outer cell membrane, cytosol, and nucleus. The cGAS/STING signaling pathway is a cytosolic PRR system. Notably, cGAS is also present in the nucleus. The cGAS-mediated recognition of cytosolic dsDNA and its cleavage into cGAMP activates STING. Furthermore, STING activation through its downstream signaling triggers different interferon-stimulating genes (ISGs), initiating the release of type 1 interferons (IFNs) and NF-κB-mediated release of proinflammatory cytokines and molecules. Activating cGAS/STING generates type 1 IFN, which may prevent cellular transformation and cancer development, growth, and metastasis. The current article delineates the impact of the cancer cell-specific cGAS/STING signaling pathway alteration in tumors and its impact on tumor growth and metastasis. This article further discusses different approaches to specifically target cGAS/STING signaling in cancer cells to inhibit tumor growth and metastasis in conjunction with existing anticancer therapies.

Irradiated Mammary Spheroids Elucidate Mechanisms of Macrophage-Mediated Breast Cancer Recurrence

Introduction

While most patients with triple negative breast cancer receive radiation therapy to improve outcomes, a significant subset of patients continue to experience recurrence. Macrophage infiltration into radiation-damaged sites has been shown to promote breast cancer recurrence in pre-clinical models. However, the mechanisms that drive recurrence are unknown. Here, we developed a novel spheroid model to evaluate macrophage-mediated tumor cell recruitment.

Methods

We characterized infiltrating macrophage phenotypes into irradiated mouse mammary tissue via flow cytometry. We then engineered a spheroid model of radiation damage with primary fibroblasts, macrophages, and 4T1 mouse mammary carcinoma cells using in vivo macrophage infiltration results to inform our model. We analyzed 4T1 infiltration into spheroids when co-cultured with biologically relevant ratios of pro-healing M2:pro-inflammatory M1 macrophages. Finally, we quantified interleukin 6 (IL-6) secretion associated with conditions favorable to tumor cell infiltration, and we directly evaluated the impact of IL-6 on tumor cell invasiveness in vitro and in vivo.

Results

In our in vivo model, we observed a significant increase in M2 macrophages in mouse mammary glands 10 days post-irradiation. We determined that tumor cell motility toward irradiated spheroids was enhanced in the presence of a 2:1 ratio of M2:M1 macrophages. We also measured a significant increase in IL-6 secretion after irradiation both in vivo and in our model. This secretion increased tumor cell invasiveness, and tumor cell invasion and recruitment were mitigated by neutralizing IL-6.

Conclusions

Our work suggests that interactions between infiltrating macrophages and damaged stromal cells facilitate breast cancer recurrence through IL-6 signaling.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-023-00775-x.

Enhancement of PD-L1-attenuated CAR-T cell function through breast cancer-associated fibroblasts-derived IL-6 signaling via STAT3/AKT pathways

BACKGROUND

Carcinoma-associated fibroblasts (CAFs) play a critical role in cancer progression and immune cell modulation. In this study, it was aimed to evaluate the roles of CAFs-derived IL-6 in doxorubicin (Dox) resistance and PD-L1-mediated chimeric antigenic receptor (CAR)-T cell resistance in breast cancer (BCA).

METHODS

CAF conditioned-media (CM) were collected, and the IL-6 level was measured by ELISA. CAF-CM were treated in MDA-MB-231 and HCC70 TNBC cell lines and siIL-6 receptor (IL-6R) knocked down (KD) cells to determine the effect of CAF-derived IL-6 on Dox resistance by flow cytometry and on increased PD-L1 through STAT3, AKT and ERK1/2 pathways by Western blot analysis. After pre-treating with CM, the folate receptor alpha (FRα)-CAR T cell cytotoxicity was evaluated in 2D and 3D spheroid culture assays.

RESULTS

The results showed a significant level of IL-6 in CAF-CM compared to that of normal fibroblasts (NFs). The CM with high IL-6 level significantly induced Dox resistance; and PD-L1 expression through STAT3 and AKT pathways in MDA-MB-231 and HCC70 cells. These induction effects were attenuated in siIL-6R KD cells. Moreover, the TNBC cell lines that were CM-treated with STAT3 and an AKT inhibitor had a reduced effect of IL-6 on PD-L1 expression. BCA cells with high IL-6 containing-CM treatment had resistance to cancer cell killing by FRα CAR-T cells compared to untreated cells.

CONCLUSION

These results highlight CAF-derived IL-6 in the resistance of chemotherapy and T cell therapy. Using inhibitors of IL6-STAT3/AKT-PD-L1 axis may provide a potential benefit of Dox and CAR-T cell therapies in BCA patients.

Targeting the stimulator of interferon genes (STING) in breast cancer

Breast cancer has a high occurrence rate globally and its treatment has demonstrated clinical efficacy with the use of systemic chemotherapy and immune checkpoint blockade. Insufficient cytotoxic T lymphocyte infiltration and the accumulation of immunosuppressive cells within tumours are the primary factors responsible for the inadequate clinical effectiveness of breast cancer treatment. The stimulator of interferon genes (STING) represents a pivotal protein in the innate immune response. Upon activation, STING triggers the activation and enhancement of innate and adaptive immune functions, resulting in therapeutic benefits for malignant tumours. The STING signalling pathway in breast cancer is influenced by various factors such as deoxyribonucleic acid damage response, tumour immune microenvironment, and mitochondrial function. The use of STING agonists is gaining momentum in breast cancer research. This review provides a comprehensive overview of the cyclic guanosine monophosphate-adenosine monophosphate synthase-STING pathway, its agonists, and the latest findings related to their application in breast cancer.

Development of a risk model to predict prognosis in breast cancer based on cGAS-STING-related genes

Background: Breast cancer (BRCA) is regarded as a lethal and aggressive cancer with increasing morbidity and mortality worldwide. cGAS-STING signaling regulates the crosstalk between tumor cells and immune cells in the tumor microenvironment (TME), emerging as an important DNA-damage mechanism. However, cGAS-STING-related genes (CSRGs) have rarely been investigated for their prognostic value in breast cancer patients.

Methods: Our study aimed to construct a risk model to predict the survival and prognosis of breast cancer patients. We obtained 1087 breast cancer samples and 179 normal breast tissue samples from the Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEX) database, 35 immune-related differentially expression genes (DEGs) from cGAS-STING-related genes were systematically assessed. The Cox regression was applied for further selection, and 11 prognostic-related DEGs were used to develop a machine learning-based risk assessment and prognostic model.

Results: We successfully developed a risk model to predict the prognostic value of breast cancer patients and its performance acquired effective validation. The results derived from Kaplan-Meier analysis revealed that the low-risk score patients had better overall survival (OS). The nomogram that integrated the risk score and clinical information was established and had good validity in predicting the overall survival of breast cancer patients. Significant correlations were observed between the risk score and tumor-infiltrating immune cells, immune checkpoints and the response to immunotherapy. The cGAS-STING-related genes risk score was also relevant to a series of clinic prognostic indicators such as tumor staging, molecular subtype, tumor recurrence, and drug therapeutic sensibility in breast cancer patients.

Conclusion: cGAS-STING-related genes risk model provides a new credible risk stratification method to improve the clinical prognostic assessment for breast cancer.

Epigenetic-Metabolic Interplay in the DNA Damage Response and Therapeutic Resistance of Breast Cancer

Therapy resistance is imposing a daunting challenge on effective clinical management of breast cancer. Although the development of resistance to drugs is multifaceted, reprogramming of energy metabolism pathways is emerging as a central but heterogenous regulator of this therapeutic challenge. Metabolic heterogeneity in cancer cells is intricately associated with alterations of different signaling networks and activation of DNA damage response pathways. Here we consider how the dynamic metabolic milieu of cancer cells regulates their DNA damage repair ability to ultimately contribute to development of therapy resistance. Diverse epigenetic regulators are crucial in remodeling the metabolic landscape of cancer. This epigenetic-metabolic interplay profoundly affects genomic stability of the cancer cells as well as their resistance to genotoxic therapies. These observations identify defining mechanisms of cancer epigenetics-metabolism-DNA repair axis that can be critical for devising novel, targeted therapeutic approaches that could sensitize cancer cells to conventional treatment strategies.

More than one route to render tumors resistant to cGAS/STING activation

STING (stimulator of interferon genes) activation has considerable potential as a new strategy for cancer therapy, but clinical results have not been encouraging. Recent studies by Hong et al. and Li et al. explain why STING agonists often fail to regress human tumors and propose combinatorial strategies to overcome the protumor effects of STING activation.

Clonogenicity-based radioresistance determines the expression of immune suppressive immune checkpoint molecules after hypofractionated irradiation of MDA-MB-231 triple-negative breast cancer cells

Only a subset of patients with triple-negative breast cancer (TNBC) benefits from a combination of radio- (RT) and immunotherapy. Therefore, we aimed to examine the impact of radioresistance and brain metastasizing potential on the immunological phenotype of TNBC cells following hypofractionated RT by analyzing cell death, immune checkpoint molecule (ICM) expression and activation of human monocyte-derived dendritic cells (DCs). MDA-MB-231 triple-negative breast cancer tumor cells were used as model system. Apoptosis was the dominant cell death form of brain metastasizing tumor cells, while Hsp70 release was generally significantly increased following RT and went along with necrosis induction. The ICMs PD-L1, PD-L2, HVEM, ICOS-L, CD137-L and OX40-L were found on the tumor cell surfaces and were significantly upregulated by RT with 5 x 5.2 Gy. Strikingly, the expression of immune suppressive ICMs was significantly higher on radioresistant clones compared to their respective non-radioresistant ones. Although hypofractionated RT led to significant cell death induction and release of Hsp70 in all tumor cell lines, human monocyte-derived DCs were not activated after co-incubation with RT-treated tumor cells. We conclude that radioresistance is a potent driver of immune suppressive ICM expression on the surface of TNBC MDA-MB-231 cells. This mechanism is generally known to predominantly influence the effector phase, rather than the priming phase, of anti-tumor immune responses.

Role of STING protein in breast cancer: mechanisms and therapeutic implications

Breast cancer is one of the most frequent causes of cancer related death worldwide, and despite the significant advances in therapeutic approaches, a significant proportion of patients succumb to metastasis and tumor recurrence. Breast cancer is an immunogenic cancer, and therefore, immunotherapy is considered a major therapeutic strategy. The survival rate has been increased significantly in HER2+ breast cancers after immunotherapy by monoclonal antibodies alone, or combined with chemical anti-cancer agents. Moreover, in triple negative breast cancer (TNBC), a number of novel agents called immune checkpoint inhibitors have shown optimal efficacy. The major hindrance in cancer immunotherapy is frequent development of resistance and cancer remission. cGAS-STING pathway has a key role in anti-cancer immunity as its downstream signals especially type I interferon (IFN) acts as a link between innate and adaptive immunity. Considering the roles of type I IFN in enhancing dendritic cells activity, promoting the functions of CD8⁺ T cells, and protecting the effector cells against apoptosis, the induction of cGAS-STING pathway demonstrated promising therapeutic effects against breast cancer, especially in triple negative breast cancers. In this review, we discuss the latest findings and the recent advances regarding the role of cGAS-STING pathway and its activation in breast cancer.