STAT3, a Master Regulator of Anti-Tumor Immune Response

Chuanxiong Rhizoma regulates ferroptosis and the immune microenvironment in ischemic stroke through the JAK-STAT3 pathway

Ferroptosis is linked to various pathological conditions; however, the specific targets and mechanisms through which traditional Chinese medicine influences ischemic stroke (IS)-induced ferroptosis remain poorly understood. In this study, data from the Gene Expression Omnibus and disease target databases (OMIM, GeneCards, DisGeNet, TTD, and DrugBank) were integrated with ferroptosis-related gene datasets. To identify key molecular targets of Chuanxiong Rhizoma (CX), drug ingredient databases, including PubChem and TCMBank, were employed to map CX-related targets (CX-DEGs-FRG and CX-IS-FRG). Gene targets and relevant signaling pathways were analyzed using weighted gene co-expression network analysis, protein-protein interaction networks, Gene Ontology, and Kyoto Encyclopedia of Genes and Genomes pathway enrichment. The least absolute shrinkage and selection operator regression and support vector machine methods were utilized to identify intersecting genes, and the predictive accuracy of core targets was evaluated through receiver operating characteristic curve analysis. Immune cell infiltration in the IS microenvironment was assessed using CIBERSORT, followed by molecular docking of CX's active components with key targets. The JAK-STAT3 pathway was identified as a critical regulatory mechanism, and five key targets (ALOX5, PTGS2, STAT3, G6PD, and HIF1A) emerged as central to the IS-induced ferroptosis. Elevated infiltration of CD8 + T cells and neutrophils was significantly correlated with IS. Notably, the active components mandenol and myricanone demonstrated strong binding affinities with these five targets, which validated the results from network-based analysis. In conclusion, the JAK-STAT3 pathway, through its regulation of ALOX5, PTGS2, STAT3, G6PD, and HIF1A, could play a crucial role in modulating ferroptosis and immune responses in IS. These findings suggest that CX could serve as a potential therapeutic approach for IS, targeting the regulation of IS-induced ferroptosis and the immune microenvironment.

Pan-cancer analysis of STAT3 indicates its potential prognostic value and correlation with immune cell infiltration in prostate cancer

BACKGROUND

Targeting the STAT3 signaling pathway is a promising therapeutic approach for cancer patients. However, the association between STAT3 expression, the tumor immune microenvironment, and genetic variation remains unclear across human cancers, especially prostate cancer.

METHODS

We used R software and other tools to analyze pan-cancer and mutation data from publicly available databases statistically. A comprehensive investigation was performed to assess the genetic heterogeneity and clinical relevance of STAT3 in various malignancies, with a specific focus on its role in the immune landscape and prognostic significance in prostate cancer. The findings were validated through immunohistochemistry (IHC) and multiplex immunofluorescence (mIF).

RESULTS

STAT3 expression is abnormal in the majority of cancer tissues, which is strongly correlated with these patients' prognosis. Eight measures of tumor heterogeneity and six measures of tumor stemness of multiple tumor types showed a strong correlation with STAT3 expression. Furthermore, in individuals with prostate cancer, STAT3 expression indicated the degree of immune cell infiltration and the advancement of the disease. IHC analysis revealed that STAT3 was down-regulated in prostate tumor tissues, while mIF analysis demonstrated that STAT3 signaling (p-STAT3) was extensively active in tumor tissues and positive lymph node tissues.

CONCLUSION

STAT3 may serve as a valuable prognostic biomarker and therapeutic target across various cancers, with particular relevance to prostate cancer.

Using bioinformatics and artificial intelligence to map the cyclin-dependent kinase 4/6 inhibitor biomarker landscape in breast cancer

A cyclin-dependent kinase 4/6 (CDK4/6) inhibitor combined with endocrine therapy is the standard-of-care for patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative advanced breast cancer. However, not all patients respond to the treatment, resistance often occurs and efficacy outcomes from early breast cancer trials have been mixed. To identify biomarkers associated with CDK4/6 inhibitor response or resistance, we combined bioinformatic-database analyses, artificial intelligence-assisted literature review, and manual literature review (Embase and OVID Medline; search window: January 2012-October 2022) to compile data to comprehensively describe the CDK4/6 inhibitor biomarker landscape. Based on these results, and validation by external experts, we identified 15 biomarkers of clinical importance (AR , AURKA, ERBB2, ESR1, CCNE1, CDKN1A/B, CDK2, CDK6, CDK7, CDK9, FGFR1/2, MYC, PIK3CA/AKT, RB1 and STAT3) that could guide future breast cancer research.

Tumor-Derived Extracellular Vesicles Enable Tumor Tropism Chemo-Genetherapy for Local Immune Activation in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is highly heterogeneous, lacks accessible therapeutic targets, and features an immunosuppressive tumor microenvironment (TME). Anthracycline-based chemotherapy remains the primary treatment method for TNBC, while the current popular immune checkpoint inhibitors persistently encounter therapeutic resistance. Therefore, there is an urgent need to explore combined therapeutic strategies to remodel the TME and improve the treatment response. Considering the highly specific homing ability of tumor cell-derived vesicles and the key role of the signal transduction and activation of the transcription factor 3 (STAT3) pathway in TNBC, we propose a synergistic therapeutic strategy that integrates gene therapy, chemotherapy, and immunotherapy based on STAT3 short interfering RNA (siSTAT3) and doxorubicin (DOX)-functionalized tumor-derived extracellular vesicles (TEVs) (siSTAT3-DOX@TEV). The in vitro and in vivo results demonstrate that siSTAT3-DOX@TEV target tumor tissues precisely, downregulate STAT3 expression, and synergistically and efficiently induce immunogenic death, thereby reversing the immunosuppressive TME. Moreover, mass cytometry and immunohistochemistry reveal the local immune activation effect of siSTAT3-DOX@TEV, with a significant increase in M1 macrophages, CD4+ T cells, and CD8+ T cells in tumor tissues. These results provide strong hints for the development of TEV-based chemo-gene therapeutic agents for TNBC treatment at the clinical level.

pSTAT3 Expression is Increased in Advanced Prostate Cancer in Post-Initiation of Androgen Deprivation Therapy

BACKGROUND

The transcription factor Signal Transducer and Activator of Transcription 3 (STAT3) plays a role in carcinogenesis and is involved in processes, such as proliferation, differentiation, drug resistance and immunosuppression. STAT3 can be activated by phosphorylation of tyrosine at position 705 (pSTAT3Tyr705) or serine at 727 (pSTAT3Ser727). High expression levels of pSTAT3 are implicated in advanced stages of prostate cancer (PCa) and are known to interact with the androgen receptor signaling pathway. However, not much is known about how androgen deprivation therapy (ADT) in advanced disease affects pSTAT3 expression. The aim of this study was to determine the influence of ADT on pSTAT3 expression in PCa tissue.

METHODS

The study cohort came from a PCa tissue microarray resource containing prostate specimens from patients before and post-initiation of ADT. Tissue samples from 111 patients were immunostained for pSTAT3Tyr705 and pSTAT3Ser727. H-score was used to evaluate the intensity and the percentage of pSTAT3 expression in malignant epithelial and stromal compartments. Univariate and multivariable Cox regression analyses were used to assess pSTAT3Tyr705 and pSTAT3Ser727 as biomarkers of oncological outcome in patients undergoing ADT.

RESULTS

Post-ADT PCa samples demonstrated increased nuclear and cytoplasmic levels of pSTAT3Ser727 in the stroma compared to pre-ADT samples, whereas pSTAT3Tyr705 expression was increased significantly in both stromal and malignant epithelial compartments except for stromal cytoplasm. High cytoplasmic pSTAT3Ser727 in stromal compartments correlated with reduced overall survival, shorter time to castration-resistant PCa development, and decreased metastasis-free survival. An increase in nuclear and cytoplasmic pSTAT3Ser727 expression within the stromal compartment of post-ADT samples corresponded to a shorter time to CRPC development, which was not observed for pSTAT3Tyr705. Multivariable survival analysis using Cox's regression identified that high cytoplasmic pSTAT3Ser727 expression in the stroma of post-ADT samples and pT3 or pT4-stage were associated with worse overall survival and 5-year metastasis-free survival (MFS).

CONCLUSIONS

This study presents novel insights into the impact of ADT on the expression levels of pSTAT3Tyr705 and pSTAT3Ser727 in PCa. Cytoplasmic pSTAT3Ser727 status of cancer-associated stromal cells in post-ADT samples may serve as an independent prognostic marker for OS and 5-year MFS, identifying prostate cancer patients prone to developing resistance to ADT.

A New IL-6-Inducing Mechanism in Cancer with New Therapeutic Possibilities

Background: Interleukin-6 is dysregulated in multiple pathological conditions, e.g., cancer and inflammatory diseases. Aim: To investigate new mechanisms for the regulation of pathological IL-6 production. Methods: PBMCs (peripheral blood mononuclear cells) stimulated by cancer serum factors or specific peptides produce interleukin-6 (IL-6). Immunoregulatory albumin neo-structures and peptides were identified with 2D gel electrophoresis and MALDI-TOF-MS (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry) analyses. Il-6 and albumin neo-structures were determined by ELISA (enzyme-linked immunosorbent assay). Results: Conformational changes in normal serum albumin by proteolytic degradation generates an IL-6-inducing neo-structure, IL-6-inducing factor (IL-6IF). This neo-structure is immunogenic which results in the production of autoantibodies. IL-6 production induced by IL-6IF and cancer patient sera is inhibited by specific antibodies. The serum concentration of IL-6IF is significantly higher in advanced cancer stages, and its presence is significantly correlated with the survival of the patients. Conclusions: A new mechanism for the induction IL-6 synthesis is presented. Based on this mechanism, the pathological IL-6 production related to enhanced proteolytic activity can be diagnosed and selectively inhibited by specific antibodies. Such antibodies were identified and purified. Thus, the neo-structure, inducing pathological IL-6 production, associated with a reduced survival of cancer patients, can be selectively removed by the therapeutic administration of antibodies leaving the function of IL-6 needed for the normal activity of the immune system intact.

Induction of immunogenic cell death and enhancement of the radiation-induced immunogenicity by chrysin in melanoma cancer cells

Chrysin is a natural flavonoid with anti-cancer effects. Despite its beneficial effects, little information is available regarding its immunogenic cell death (ICD) properties. In this work, we hypothesized that chrysin can potentiate radiotherapy(RT)-induced immunogenicity in melanoma cell line (B16-F10). We examined the effects of chrysin alone and in combination with radiation on ICD induction in B16-F10 cells. Cell viability was assessed using an MTT assay. Cell apoptosis and calreticulin (CRT) exposure were determined using flow cytometry. Western blotting and ELISA assay were employed to examine changes in protein expression. Combination therapy exhibited a synergistic effect, with an optimum combination index of 0.66. The synergistic anti-cancer effect correlated with increased cell apoptosis in cancer cells. Compared to the untreated control, chrysin alone and in combination with RT induced higher levels of DAMPs, such as CRT, HSP70, HMGB1, and ATP. The protein expression of p-STAT3/STAT3 and PD-L1 was reduced in B16-F10 cells exposed to chrysin alone and in combination with RT. Conditioned media from B16-F10 cells exposed to mono-and combination treatments elicited IL-12 secretion in dendritic cells (DCs), inducing a Th1 response. Our findings revealed that chrysin could induce ICD and intensify the RT-induced immunogenicity.

STAT3 blockade ameliorates LPS-induced kidney injury through macrophage-driven inflammation

BACKGROUND

Signal transducer and activator of transcription 3 (STAT3), a multifaceted transcription factor, modulates host immune responses by activating cellular response to signaling ligands. STAT3 has a pivotal role in the pathophysiology of kidney injury by counterbalancing resident macrophage phenotypes under inflammation conditions. However, STAT3's role in acute kidney injury (AKI), particularly in macrophage migration, and in chronic kidney disease (CKD) through fibrosis development, remains unclear.

METHODS

Stattic (a JAK2/STAT3 inhibitor, 5 mg/kg or 10 mg/kg) was administered to evaluate the therapeutic effect on LPS-induced AKI (L-AKI) and LPS-induced CKD (L-CKD), with animals sacrificed 6-24 h and 14 days post-LPS induction, respectively. The immune mechanisms of STAT3 blockade were determined by comparing the macrophage phenotypes and correlated with renal function parameters. Also, the transcriptomic analysis was used to confirm the anti-inflammatory effect of L-AKI, and the anti-fibrotic role was further evaluated in the L-CKD model.

RESULTS

In the L-AKI model, sequential increases in BUN and blood creatinine levels were time-dependent, with a marked elevation of 0-6 h after LPS injection. Notably, two newly identified macrophage subpopulations (CD11bhighF4/80low and CD11blowF4/80high), exhibited population changes, with an increase in the CD11bhighF4/80low population and a decrease in the CD11blowF4/80high macrophages. Corresponding to the FACS results, the tubular injury score, NGAL, F4/80, and p-STAT3 expression in the tubular regions were elevated. STAT3 inhibitor injection in L-AKI and L-CKD mice reduced renal injury and fibrosis. M2-type subpopulation with CD206 in CD11blowF4/80high population increased in the Stattic-treated group compared with that in the LPS-alone group in the L-AKI model. Additionally, STAT3 inhibitor reduced inflammation driven by LPS-stimulated macrophages and epithelial cells injury in the co-culture system. Transcriptomic profiling identified 3 common genes in the JAK-STAT, TLR, and TNF signaling pathways and 11 common genes in the LPS with macrophage response. The PI3K-AKT (IL-6, Akt3, and Pik3r1) and JAK-STAT pathways were determined as potential Stattic targets. Further confirmation through mRNA and protein expressions analyses showed that Stattic treatment reduced inflammation in the L-AKI and fibrosis in the L-CKD mice.

CONCLUSIONS

STAT3 blockade effectively mitigated inflammation by retrieving the CD11blowF4/80high population, further emphasizing the role of STAT3-associated macrophage-driven inflammation in kidney injury.

MicroRNA-135b mainly functions as an oncogene during tumor progression

Late diagnosis is considered one of the main reasons of high mortality rate among cancer patients that results in therapeutic failure and tumor relapse. Therefore, it is needed to evaluate the molecular mechanisms associated with tumor progression to introduce efficient markers for the early tumor detection among cancer patients. The remarkable stability of microRNAs (miRNAs) in body fluids makes them potential candidates to use as the non-invasive tumor biomarkers in cancer screening programs. MiR-135b has key roles in prognosis and survival of cancer patients by either stimulating or inhibiting cell proliferation, invasion, and angiogenesis. Therefore, in the present review we assessed the molecular biology of miR-135b during tumor progression to introduce that as a novel tumor marker in cancer patients. It has been reported that miR-135b mainly acts as an oncogene by regulation of transcription factors, signaling pathways, drug response, cellular metabolism, and autophagy. This review paves the way to suggest miR-135b as a tumor marker and therapeutic target in cancer patients following the further clinical trials and animal studies.

Feasibility of the inhibitor development for cancer: A systematic approach for drug design

The traditional Chinese medicine (TCM) bupleurum-ginger-licorice formula presents significant anti-cancer effects, but its active ingredients and inhibitory mechanism remain unclear. In this work, the core effective ingredient quercetin and its signal transducer and activator of transcription 3 (Stat3) receptor both were identified by network pharmacology. Quercetin is a low-toxicity, non-carcinogenic flavonoid with antioxidant, anti-inflammatory and anticancer activities, which is widely distributed in edible plants. Stat3 can bind to specific DNA response elements and serves as a transcription factor to promote the translation of some invasion/migration-related target genes, considered as a potential anticancer target. Here, molecular docking and molecular dynamics (MD) simulation both were used to explore molecular recognition of quercetin with Stat3. The results show that quercetin impairs DNA transcription efficiency by hindering Stat3 dimerization, partially destroying DNA conformation. Specifically, when the ligand occupies the SH2 cavity of the enzyme, spatial rejection is not conductive to phosphokinase binding. It indirectly prevents the phosphorylation of Y705 and the formation of Stat3 dimer. When the inhibitor binds to the DT1005 position, it obviously shortens the distance between DNA and DBD, enhances their binding capacity, and thereby reduces the degree of freedom required for transcription. This work not only provides the binding modes between Stat3 and quercetin, but also contributes to the optimization and design of such anti-cancer inhibitors.

BP1003 Decreases STAT3 Expression and Its Pro-Tumorigenic Functions in Solid Tumors and the Tumor Microenvironment

Overexpression and aberrant activation of signal transducer and activator of transcription 3 (STAT3) contribute to tumorigenesis, drug resistance, and tumor-immune evasion, making it a potential cancer therapeutic target. BP1003 is a neutral liposome incorporated with a nuclease-resistant P-ethoxy antisense oligodeoxynucleotide (ASO) targeting the STAT3 mRNA. Its unique design enhances BP1003 stability, cellular uptake, and target affinity. BP1003 efficiently reduces STAT3 expression and enhances the sensitivity of breast cancer cells (HER2+, triple negative) and ovarian cancer cells (late stage, invasive ovarian cancer) to paclitaxel and 5-fluorouracil (5-FU) in both 2D and 3D cell cultures. Similarly, ex vivo and in vivo patient-derived models of pancreatic ductal adenocarcinoma (PDAC) show reduced tissue viability and tumor volume with BP1003 and gemcitabine combination treatments. In addition to directly affecting tumor cells, BP1003 can modulate the tumor microenvironment. Unlike M1 differentiation, monocyte differentiation into anti-inflammatory M2 macrophages is suppressed by BP1003, indicating its potential contribution to immunotherapy. The broad anti-tumor effect of BP1003 in numerous preclinical solid tumor models, such as breast, ovarian, and pancreatic cancer models shown in this work, makes it a promising cancer therapeutic.

Inhibition of STAT3: A promising approach to enhancing the efficacy of chemotherapy in medulloblastoma

Medulloblastoma is a type of brain cancer that primarily affects children. While chemotherapy has been shown to be effective in treating medulloblastoma, the development of chemotherapy resistance remains a challenge. One potential therapeutic approach is to selectively inhibit the inducible transcription factor called STAT3, which is known to play a crucial role in the survival and growth of tumor cells. The activation of STAT3 has been linked to the growth and progression of various cancers, including medulloblastoma. Inhibition of STAT3 has been shown to sensitize medulloblastoma cells to chemotherapy, leading to improved treatment outcomes. Different approaches to STAT3 inhibition have been developed, including small-molecule inhibitors and RNA interference. Preclinical studies have shown the efficacy of STAT3 inhibitors in medulloblastoma, and clinical trials are currently ongoing to evaluate their safety and effectiveness in patients with various solid tumors, including medulloblastoma. In addition, researchers are also exploring ways to optimize the use of STAT3 inhibitors in combination with chemotherapy and identify biomarkers that can predict treatment that will help to develop personalized treatment strategies. This review highlights the potential of selective inhibition of STAT3 as a novel approach for the treatment of medulloblastoma and suggests that further research into the development of STAT3 inhibitors could lead to improved outcomes for patients with aggressive cancer.

Renal cancer: signaling pathways and advances in targeted therapies

Renal cancer is a highlyheterogeneous malignancy characterized by rising global incidence and mortalityrates. The complex interplay and dysregulation of multiple signaling pathways,including von Hippel-Lindau (VHL)/hypoxia-inducible factor (HIF), phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR), Hippo-yes-associated protein (YAP), Wnt/ß-catenin, cyclic adenosine monophosphate (cAMP), and hepatocyte growth factor (HGF)/c-Met, contribute to theinitiation and progression of renal cancer. Although surgical resection is thestandard treatment for localized renal cancer, recurrence and metastasiscontinue to pose significant challenges. Advanced renal cancer is associatedwith a poor prognosis, and current therapies, such as targeted agents andimmunotherapies, have limitations. This review presents a comprehensiveoverview of the molecular mechanisms underlying aberrant signaling pathways inrenal cancer, emphasizing their intricate crosstalk and synergisticinteractions. We discuss recent advancements in targeted therapies, includingtyrosine kinase inhibitors, and immunotherapies, such as checkpoint inhibitors.Moreover, we underscore the importance of multiomics approaches and networkanalysis in elucidating the complex regulatory networks governing renal cancerpathogenesis. By integrating cutting-edge research and clinical insights, this review contributesto the development of innovative diagnostic and therapeutic strategies, whichhave the potential to improve risk stratification, precision medicine, andultimately, patient outcomes in renal cancer.

Harnessing the capacity of phytochemicals to enhance immune checkpoint inhibitor therapy of cancers: A focus on brain malignancies

Brain cancers, particularly glioblastoma multiforme (GBM), are challenging health issues with frequent unmet aspects. Today, discovering safe and effective therapeutic modalities for brain tumors is among the top research interests. Immunotherapy is an emerging area of investigation in cancer treatment. Since immune checkpoints play fundamental roles in repressing anti-cancer immunity, diverse immune checkpoint inhibitors (ICIs) have been developed, and some monoclonal antibodies have been approved clinically for particular cancers; nevertheless, there are significant concerns regarding their efficacy and safety in brain tumors. Among the various tools to modify the immune checkpoints, phytochemicals show good effectiveness and excellent safety, making them suitable candidates for developing better ICIs. Phytochemicals regulate multiple immunological checkpoint-related signaling pathways in cancer biology; however, their efficacy for clinical cancer immunotherapy remains to be established. Here, we discussed the involvement of immune checkpoints in cancer pathology and summarized recent advancements in applying phytochemicals in modulating immune checkpoints in brain tumors to highlight the state-of-the-art and give constructive prospects for future research.

RNAi mediated silencing of STAT3/PD-L1 in tumor-associated immune cells induces robust anti-tumor effects in immunotherapy resistant tumors

Malignant tumors are often associated with an immunosuppressive tumor microenvironment (TME), rendering most of them resistant to standard-of-care immune checkpoint inhibitors (CPIs). Signal transducer and activator of transcription 3 (STAT3), a ubiquitously expressed transcription factor, has well-defined immunosuppressive functions in several leukocyte populations within the TME. Since the STAT3 protein has been challenging to target using conventional pharmaceutical modalities, we investigated the feasibility of applying systemically delivered RNA interference (RNAi) agents to silence its mRNA directly in tumor-associated immune cells. In preclinical rodent tumor models, chemically stabilized acylated small interfering RNAs (siRNAs) selectively silenced Stat3 mRNA in multiple relevant cell types, reduced STAT3 protein levels, and increased cytotoxic T cell infiltration. In a murine model of CPI-resistant pancreatic cancer, RNAi-mediated Stat3 silencing resulted in tumor growth inhibition, which was further enhanced in combination with CPIs. To further exemplify the utility of RNAi for cancer immunotherapy, this technology was used to silence Cd274, the gene encoding the immune checkpoint protein programmed death-ligand 1 (PD-L1). Interestingly, silencing of Cd274 was effective in tumor models that are resistant to PD-L1 antibody therapy. These data represent the first demonstration of systemic delivery of RNAi agents to the TME and suggest applying this technology for immuno-oncology applications.

Stat3 Regulates Developmental Hematopoiesis and Impacts Myeloid Cell Function via Canonical and Non-Canonical Modalities

INTRODUCTION

Signal transducer and activator of transcription (STAT) 3 is extensively involved in the development, homeostasis, and function of immune cells, with STAT3 disruption associated with human immune-related disorders. The roles ascribed to STAT3 have been assumed to be due to its canonical mode of action as an inducible transcription factor downstream of multiple cytokines, although alternative noncanonical functional modalities have also been identified. The relative involvement of each mode was further explored in relevant zebrafish models.

METHODS

Genome editing with CRISPR/Cas9 was used to generate mutants of the conserved zebrafish Stat3 protein: a loss of function knockout (KO) mutant and a mutant lacking C-terminal sequences including the transactivation domain (ΔTAD). Lines harboring these mutations were analyzed with respect to blood and immune cell development and function in comparison to wild-type zebrafish.

RESULTS

The Stat3 KO mutant showed perturbation of hematopoietic lineages throughout primitive and early definitive hematopoiesis. Neutrophil numbers did not increase in response to lipopolysaccharide (LPS) or granulocyte colony-stimulating factor (G-CSF) and their migration was significantly diminished, the latter correlating with abrogation of the Cxcl8b/Cxcr2 pathway, with macrophage responses perturbed. Intriguingly, many of these phenotypes were not shared by the Stat3 ΔTAD mutant. Indeed, only neutrophil and macrophage development were disrupted in these mutants with responsiveness to LPS and G-CSF maintained, and neutrophil migration actually increased.

CONCLUSION

This study has identified roles for zebrafish Stat3 within hematopoietic stem cells impacting multiple lineages throughout primitive and early definitive hematopoiesis, myeloid cell responses to G-CSF and LPS and neutrophil migration. Many of these roles showed conservation, but notably several involved noncanonical modalities, providing additional insights for relevant diseases.

Mechanism of Action of Melatonin as a Potential Adjuvant Therapy in Inflammatory Bowel Disease and Colorectal Cancer

Inflammatory bowel disease (IBD), a continuum of chronic inflammatory diseases, is tightly associated with immune system dysregulation and dysbiosis, leading to inflammation in the gastrointestinal tract (GIT) and multiple extraintestinal manifestations. The pathogenesis of IBD is not completely elucidated. However, it is associated with an increased risk of colorectal cancer (CRC), which is one of the most common gastrointestinal malignancies. In both IBD and CRC, a complex interplay occurs between the immune system and gut microbiota (GM), leading to the alteration in GM composition. Melatonin, a neuroendocrine hormone, was found to be involved with this interplay, especially since it is present in high amounts in the gut, leading to some protective effects. Actually, melatonin enhances the integrity of the intestinal mucosal barrier, regulates the immune response, alleviates inflammation, and attenuates oxidative stress. Thereby, the authors summarize the multifactorial interaction of melatonin with IBD and with CRC, focusing on new findings related to the mechanisms of action of this hormone, in addition to its documented positive outcomes on the treatment of these two pathologies and possible future perspectives to use melatonin as an adjuvant therapy.

Coagulation Protease-Driven Cancer Immune Evasion: Potential Targets for Cancer Immunotherapy

Blood coagulation and cancer are intrinsically connected, hypercoagulation-associated thrombotic complications are commonly observed in certain types of cancer, often leading to decreased survival in cancer patients. Apart from the common role in coagulation, coagulation proteases often trigger intracellular signaling in various cancers via the activation of a G protein-coupled receptor superfamily protease: protease-activated receptors (PARs). Although the role of PARs is well-established in the development and progression of certain types of cancer, their impact on cancer immune response is only just emerging. The present review highlights how coagulation protease-driven PAR signaling plays a key role in modulating innate and adaptive immune responses. This is followed by a detailed discussion on the contribution of coagulation protease-induced signaling in cancer immune evasion, thereby supporting the growth and development of certain tumors. A special section of the review demonstrates the role of coagulation proteases, thrombin, factor VIIa, and factor Xa in cancer immune evasion. Targeting coagulation protease-induced signaling might be a potential therapeutic strategy to boost the immune surveillance mechanism of a host fighting against cancer, thereby augmenting the clinical consequences of targeted immunotherapeutic regimens.

STAT activation in regulatory CD4+ T cells of patients with primary sclerosing cholangitis

INTRODUCTION

Regulatory CD4+ T cells (Tregs) are pivotal for inhibition of autoimmunity. Primary sclerosing cholangitis (PSC) is an autoimmune cholestatic liver disease of unknown etiology where contribution of Tregs is still unclear. Activation of the JAK-STAT pathway critically modifies functions of Tregs. In PSC, we studied activation of STAT proteins and Treg functions in response to cytokines.

METHODS

In 51 patients with PSC, 10 disease controls (chronic replicative hepatitis C), and 36 healthy controls we analyzed frequencies of Foxp3+CD25+CD127lowCD4+ Tregs, their expression of ectonucleotidase CD39, and cytokine-induced phosphorylation of STAT1, 3, 5, and 6 using phospho-flow cytometry. In parallel, we measured cytokines IFN-gamma, interleukin (IL)-6, IL-2, and IL-4 in serum via bead-based immunoassays.

RESULTS

In patients with PSC, ex vivo frequencies of peripheral Tregs and their expression of CD39 were significantly reduced (p < .05 each). Furthermore, serum levels of IFN-gamma, IL-6, IL-2, and IL-4 were markedly higher in PSC (p < .05 each). Unlike activation of STAT1, STAT5, and STAT6, IL-6 induced increased phosphorylation of STAT3 in Tregs of PSC-patients (p = .0434). Finally, STAT3 activation in Tregs correlated with leukocyte counts.

CONCLUSIONS

In PSC, we observed enhanced STAT3 responsiveness of CD4+ Tregs together with reduced CD39 expression probably reflecting inflammatory activity of the disease.

Efficient polymeric nanoparticles for RNAi in macrophage reveal complex effects on polarization markers upon knockdown of STAT3/STAT6

Tumor associated macrophages (TAMs) are the most abundant immune cell type in the tissue microenvironment, affecting tumor progression, metastasis and therapeutic response. Different macrophage activation ("polarization") states can be distinguished: resting (M0; non-activated), pro-inflammatory/anti-tumorigenic (M1) and anti-inflammatory/pro-tumorigenic (M2). When exploring macrophages as targets in novel cancer immunotherapy approaches, TAM repolarization from the M2 into the M1 phenotype is an intriguing strategy to block their pro-tumoral and enhance their anti-tumoral properties. In the context of RNAi-based gene knockdown of M2 promoting genes, major bottlenecks include cellular siRNA delivery and correct intracellular processing. This is particularly true in case of macrophages as a cell type well-known to be notoriously hard-to-transfect. Among polymeric nanocarriers, the cationic polymer polyethylenimine (PEI) is widely explored for delivering nucleic acids. Further advanced nanocarriers are tyrosine-modified polymers based on PEI or polypropylenimine dendrimers (PPI) for highly efficient siRNA delivery in vitro and in vivo. In this paper, we explored a panel of PEI- or PPI-based nanoparticle systems for siRNA-mediated gene knockdown efficacy in macrophages and subsequent TAM repolarization. The tyrosine-modified linear 10 kDa PEI (LP10Y) or branched 5 kDa PEI (P5Y) as well as a tyrosine-modified PPI (PPI-Y) were found most efficient for gene knockdown in macrophage cell lines or primary macrophages, independent of their polarization. Knockdown of STAT6 or STAT3 led to repolarization of M2 macrophages, as indicated by alterations in various M2 and M1 marker levels. This highly specific approach also demonstrated non-redundant functions of STAT3 and STAT6. Importantly, macrophage re-polarization from M2 to M1 upon PPI-Y/siRNA-mediated STAT6 knockdown increased tumor cell phagocytosis in a co-culture model. In conclusion, we identify certain tyrosine-modified PEI- or PPI-based nanoparticles as particularly efficient for macrophage transfection, and the specific, siRNA-mediated STAT6 knockdown as a promising approach for macrophage repolarization and enhancement of their tumor cell suppressive role.

IL-17 induces NSCLC cell migration and invasion by elevating MMP19 gene transcription and expression through the interaction of p300-dependent STAT3-K631 acetylation and its Y705-phosphorylation

The cancer cell metastasis is a major death reason for patients with non-small cell lung cancer (NSCLC). Although researchers have disclosed that interleukin 17 (IL-17) can increase matrix metalloproteinases (MMPs) induction causing NSCLC cell metastasis, the underlying mechanism remains unclear. In the study, we found that IL-17 receptor A (IL-17RA), p300, p-STAT3, Ack-STAT3, and MMP19 were up-regulated both in NSCLC tissues and NSCLC cells stimulated with IL-17. p300, STAT3 and MMP19 overexpression or knockdown could raise or reduce IL-17-induced p-STAT3, Ack-STAT3 and MMP19 level as well as the cell migration and invasion. Mechanism investigation revealed that STAT3 and p300 bound to the same region (-544 to -389 nt) of MMP19 promoter, and p300 could acetylate STAT3-K631 elevating STAT3 transcriptional activity, p-STAT3 or MMP19 expression and the cell mobility exposed to IL-17. Meanwhile, p300-mediated STAT3-K631 acetylation and its Y705-phosphorylation could interact, synergistically facilitating MMP19 gene transcription and enhancing cell migration and invasion. Besides, the animal experiments exhibited that the nude mice inoculated with NSCLC cells by silencing p300, STAT3 or MMP19 gene plus IL-17 treatment, the nodule number, and MMP19, Ack-STAT3, or p-STAT3 production in the lung metastatic nodules were all alleviated. Collectively, these outcomes uncover that IL-17-triggered NSCLC metastasis involves up-regulating MMP19 expression via the interaction of STAT3-K631 acetylation by p300 and its Y705-phosphorylation, which provides a new mechanistic insight and potential strategy for NSCLC metastasis and therapy.

Biomarker-directed targeted therapy plus durvalumab in advanced non-small-cell lung cancer: a phase 2 umbrella trial

For patients with non-small-cell lung cancer (NSCLC) tumors without currently targetable molecular alterations, standard-of-care treatment is immunotherapy with anti-PD-(L)1 checkpoint inhibitors, alone or with platinum-doublet therapy. However, not all patients derive durable benefit and resistance to immune checkpoint blockade is common. Understanding mechanisms of resistance-which can include defects in DNA damage response and repair pathways, alterations or functional mutations in STK11/LKB1, alterations in antigen-presentation pathways, and immunosuppressive cellular subsets within the tumor microenvironment-and developing effective therapies to overcome them, remains an unmet need. Here the phase 2 umbrella HUDSON study evaluated rational combination regimens for advanced NSCLC following failure of anti-PD-(L)1-containing immunotherapy and platinum-doublet therapy. A total of 268 patients received durvalumab (anti-PD-L1 monoclonal antibody)-ceralasertib (ATR kinase inhibitor), durvalumab-olaparib (PARP inhibitor), durvalumab-danvatirsen (STAT3 antisense oligonucleotide) or durvalumab-oleclumab (anti-CD73 monoclonal antibody). Greatest clinical benefit was observed with durvalumab-ceralasertib; objective response rate (primary outcome) was 13.9% (11/79) versus 2.6% (5/189) with other regimens, pooled, median progression-free survival (secondary outcome) was 5.8 (80% confidence interval 4.6-7.4) versus 2.7 (1.8-2.8) months, and median overall survival (secondary outcome) was 17.4 (14.1-20.3) versus 9.4 (7.5-10.6) months. Benefit with durvalumab-ceralasertib was consistent across known immunotherapy-refractory subgroups. In ATM-altered patients hypothesized to harbor vulnerability to ATR inhibition, objective response rate was 26.1% (6/23) and median progression-free survival/median overall survival were 8.4/22.8 months. Durvalumab-ceralasertib safety/tolerability profile was manageable. Biomarker analyses suggested that anti-PD-L1/ATR inhibition induced immune changes that reinvigorated antitumor immunity. Durvalumab-ceralasertib is under further investigation in immunotherapy-refractory NSCLC.ClinicalTrials.gov identifier: NCT03334617.

Multifaceted roles for STAT3 in gammaherpesvirus latency revealed through in vivo B cell knockout models

Cancers associated with the oncogenic gammaherpesviruses, Epstein-Barr virus and Kaposi sarcoma herpesvirus, are notable for their constitutive activation of the transcription factor signal transducer and activator of transcription 3 (STAT3). To better understand the role of STAT3 during gammaherpesvirus latency and the B cell response to infection, we used the model pathogen murine gammaherpesvirus 68 (MHV68). Genetic deletion of STAT3 in B cells of CD19cre/+Stat3f/f mice reduced peak MHV68 latency approximately sevenfold. However, infected CD19cre/+Stat3f/f mice exhibited disordered germinal centers and heightened virus-specific CD8 T cell responses compared to wild-type (WT) littermates. To circumvent the systemic immune alterations observed in the B cell-STAT3 knockout mice and more directly evaluate intrinsic roles for STAT3, we generated mixed bone marrow chimeric mice consisting of WT and STAT3 knockout B cells. We discovered a dramatic reduction in latency in STAT3 knockout B cells compared to their WT B cell counterparts in the same lymphoid organ. RNA sequencing of sorted germinal center B cells revealed that MHV68 infection shifts the gene signature toward proliferation and away from type I and type II IFN responses. Loss of STAT3 largely reversed the virus-driven transcriptional shift without impacting the viral gene expression program. STAT3 promoted B cell processes of the germinal center, including IL-21-stimulated downregulation of surface CD23 on B cells infected with MHV68 or EBV. Together, our data provide mechanistic insights into the role of STAT3 as a latency determinant in B cells for oncogenic gammaherpesviruses.IMPORTANCEThere are no directed therapies to the latency program of the human gammaherpesviruses, Epstein-Barr virus and Kaposi sarcoma herpesvirus. Activated host factor signal transducer and activator of transcription 3 (STAT3) is a hallmark of cancers caused by these viruses. We applied the murine gammaherpesvirus pathogen system to explore STAT3 function upon primary B cell infection in the host. Since STAT3 deletion in all CD19+ B cells of infected mice led to altered B and T cell responses, we generated chimeric mice with both normal and STAT3-deleted B cells. B cells lacking STAT3 failed to support virus latency compared to normal B cells from the same infected animal. Loss of STAT3 impaired B cell proliferation and differentiation and led to a striking upregulation of interferon-stimulated genes. These findings expand our understanding of STAT3-dependent processes that are key to its function as a pro-viral latency determinant for oncogenic gammaherpesviruses in B cells and may provide novel therapeutic targets.

Immune Evasion in Cancer Is Regulated by Tumor-Asociated Macrophages (TAMs): Targeting TAMs

Recent advancements in cancer treatment have explored a variety of approaches to address the needs of patients. Recently, immunotherapy has evolved as an efficacious treatment for various cancers resistant to conventional therapies. Hence, significant milestones in immunotherapy were achieved clinically in a large subset of cancer patients. Unfortunately, some cancer types do not respond to treatment, and among the responsive cancers, some patients remain unresponsive to treatment. Consequently, there is a critical need to examine the mechanisms of immune resistance and devise strategies to target immune suppressor cells or factors, thereby allowing for tumor sensitivity to immune cytotoxic cells. M2 macrophages, also known as tumor-associated macrophages (TAMs), are of interest due to their role in suppressing the immune system and influencing antitumor immune responses through modulating T cell activity and immune checkpoint expression. TAMs are associated with signaling pathways that modulate the tumor microenvironment (TME), contributing to immune evasion. One approach targets TAMs, focusing on preventing the polarization of M1 macrophages into the protumoral M2 phenotype. Other strategies focus on direct or indirect targeting of M2 macrophages through understanding the interaction of TAMs with immune factors or signaling pathways. Clinically, biomarkers associated with TAMs' immune resistance in cancer patients have been identified, opening avenues for intervention using pharmacological agents or immunotherapeutic approaches. Ultimately, these multifaceted approaches are promising in overcoming immune resistance and improving cancer treatment outcomes.

Discovery of novel benzohydroxamate-based histone deacetylase 6 (HDAC6) inhibitors with the ability to potentiate anti-PD-L1 immunotherapy in melanoma

In this study, a novel series of histone deacetylases 6 (HDAC6) inhibitors containing polycyclic aromatic rings were discovered and evaluated for their pharmacological activities. The most potent compound 10c exhibited high HDAC6 inhibitory activity (IC50 = 261 nM) and excellent HDAC6 selectivity (SI = 109 for HDAC6 over HDAC3). 10c also showed decent antiproliferative activity in vitro with IC50 of 7.37-21.84 μM against four cancer cell lines, comparable to that of tubastatin A (average IC50 = 6.10 μM). Further mechanism studies revealed that 10c efficiently induced apoptosis and S-phase arrest in B16-F10 cells. In addition, 10c markedly increased the expression of acetylated-α-tubulin both in vitro and in vivo, without affecting the levels of acetylated-H3 (marker of HDAC1 inhibition). Furthermore, 10c (80 mg/kg) exhibited moderate antitumor efficacy in a melanoma tumour model with a tumour growth inhibition (TGI) of 32.9%, comparable to that (TGI = 31.3%) of tubastatin A. Importantly, the combination of 10c with NP19 (a small molecule PD-L1 inhibitor discovered by us before) decreased tumour burden substantially (TGI% = 60.1%) as compared to monotherapy groups. Moreover, the combination of 10c with NP19 enhanced the anti-tumour immune response, mediated by a decrease of PD-L1 expression levels and increased infiltration of anti-tumour CD8+ T cells in tumour tissues. Collectively, 10c represents a novel HDAC6 inhibitor deserving further investigation as a potential anti-cancer agent.

Hypoxia-driven protease legumain promotes immunosuppression in glioblastoma

Glioblastoma (GBM) is a hypoxic and "immune-cold" tumor containing rich stromal signaling molecules and cell populations, such as proteases and immunosuppressive tumor-associated macrophages (TAMs). Here, we seek to profile and characterize the potential proteases that may contribute to GBM immunosuppression. Legumain (LGMN) emerges as the key protease that is highly enriched in TAMs and transcriptionally upregulated by hypoxia-inducible factor 1-alpha (HIF1α). Functionally, the increased LGMN promotes TAM immunosuppressive polarization via activating the GSK-3β-STAT3 signaling pathway. Inhibition of macrophage HIF1α and LGMN reduces TAM immunosuppressive polarization, impairs tumor progression, enhances CD8+ T cell-mediated anti-tumor immunity, and synergizes with anti-PD1 therapy in GBM mouse models. Thus, LGMN is a key molecular switch connecting two GBM hallmarks of hypoxia and immunosuppression, providing an actionable therapeutic intervention for this deadly disease.

The missing link? LGMN connects hypoxia and immunosuppression in glioblastoma

In this issue, Pang and colleagues1 identify the protease legumain as a potential immunotherapy target in glioblastoma that drives tumor-associated macrophages in response to hypoxia.

Targeting the STAT3 oncogenic pathway: Cancer immunotherapy and drug repurposing

Immune effector cells in the microenvironment tend to be depleted or remodeled, unable to perform normal functions, and even promote the malignant characterization of tumors, resulting in the formation of immunosuppressive microenvironments. The strategy of reversing immunosuppressive microenvironment has been widely used to enhance the tumor immunotherapy effect. Signal transducer and activator of transcription 3 (STAT3) was found to be a crucial regulator of immunosuppressive microenvironment formation and activation as well as a factor, stimulating tumor cell proliferation, survival, invasiveness and metastasis. Therefore, regulating the immune microenvironment by targeting the STAT3 oncogenic pathway might be a new cancer therapy strategy. This review discusses the pleiotropic effects of STAT3 on immune cell populations that are critical for tumorigenesis, and introduces the novel strategies targeting STAT3 oncogenic pathway for cancer immunotherapy. Lastly, we summarize the conventional drugs used in new STAT3-targeting anti-tumor applications.

Epstein-Barr virus infectious particles initiate B cell transformation and modulate cytokine response

IMPORTANCE

The Epstein-Barr virus efficiently infects and transforms B lymphocytes. During this process, infectious viral particles transport the viral genome to the nucleus of target cells. We show here that these complex viral structures serve additional crucial roles by activating transcription of the transforming genes encoded by the virus. We show that components of the infectious particle sequentially activate proinflammatory B lymphocyte signaling pathways that, in turn, activate viral gene expression but also cause cytokine release. However, virus infection activates expression of ZFP36L1, an RNA-binding stress protein that limits the length and the intensity of the cytokine response. Thus, the infectious particles can activate viral gene expression and initiate cellular transformation at the price of a limited immune response.

Mechanism of Bazhen decoction in the treatment of colorectal cancer based on network pharmacology, molecular docking, and experimental validation

Objective

Bazhen Decoction (BZD) is a common adjuvant therapy drug for colorectal cancer (CRC), although its anti-tumor mechanism is unknown. This study aims to explore the core components, key targets, and potential mechanisms of BZD treatment for CRC.

Methods

The Traditional Chinese Medicine Systems Pharmacology (TCMSP) was employed to acquire the BZD's active ingredient and targets. Meanwhile, the Drugbank, Therapeutic Target Database (TTD), DisGeNET, and GeneCards databases were used to retrieve pertinent targets for CRC. The Venn plot was used to obtain intersection targets. Cytoscape software was used to construct an "herb-ingredient-target" network and identify core targets. GO and KEGG pathway enrichment analyses were conducted using R language software. Molecular docking of key ingredients and core targets of drugs was accomplished using PyMol and Autodock Vina software. Cell and animal research confirmed Bazhen Decoction efficacy and mechanism in treating colorectal cancer.

Results

BZD comprises 173 effective active ingredients. Using four databases, 761 targets related to CRC were identified. The intersection of BZD and CRC yielded 98 targets, which were utilized to construct the "herb-ingredient-target" network. The four key effector components with the most targets were quercetin, kaempferol, licochalcone A, and naringenin. Protein-protein interaction (PPI) analysis revealed that the core targets of BZD in treating CRC were AKT1, MYC, CASP3, ESR1, EGFR, HIF-1A, VEGFR, JUN, INS, and STAT3. The findings from molecular docking suggest that the core ingredient exhibits favorable binding potential with the core target. Furthermore, the GO and KEGG enrichment analysis demonstrates that BZD can modulate multiple signaling pathways related to CRC, like the T cell receptor, PI3K-Akt, apoptosis, P53, and VEGF signaling pathway. In vitro, studies have shown that BZD dose-dependently inhibits colon cancer cell growth and invasion and promotes apoptosis. Animal experiments have shown that BZD treatment can reverse abnormal expression of PI3K, AKT, MYC, EGFR, HIF-1A, VEGFR, JUN, STAT3, CASP3, and TP53 genes. BZD also increases the ratio of CD4+ T cells to CD8+ T cells in the spleen and tumor tissues, boosting IFN-γ expression, essential for anti-tumor immunity. Furthermore, BZD has the potential to downregulate the PD-1 expression on T cell surfaces, indicating its ability to effectively restore T cell function by inhibiting immune checkpoints. The results of HE staining suggest that BZD exhibits favorable safety profiles.

Conclusion

BZD treats CRC through multiple components, targets, and metabolic pathways. BZD can reverse the abnormal expression of genes such as PI3K, AKT, MYC, EGFR, HIF-1A, VEGFR, JUN, STAT3, CASP3, and TP53, and suppresses the progression of colorectal cancer by regulating signaling pathways such as PI3K-AKT, P53, and VEGF. Furthermore, BZD can increase the number of T cells and promote T cell activation in tumor-bearing mice, enhancing the immune function against colorectal cancer. Among them, quercetin, kaempferol, licochalcone A, naringenin, and formaronetin are more highly predictive components related to the T cell activation in colorectal cancer mice. This study is of great significance for the development of novel anti-cancer drugs. It highlights the importance of network pharmacology-based approaches in studying complex traditional Chinese medicine formulations.

Combination of STAT3 inhibitor with Herceptin reduced immune checkpoints expression and provoked anti-breast cancer immunity: An in vitro study

Breast cancer (BC) is the most prevalent diagnosed cancer among women. Herceptin blocks the effects of Her-2 and tumour cell growth. Despite many achievements using Herceptin in Her-2+ invasive BC treatment, there are treatment failures and resistances. The signal transducer and activator of transcription 3 (STAT3) is persistently activated in BC and is associated with immune suppression and tumour cell proliferation. We evaluated whether STAT3 inhibition could increase Herceptin impact on in vitro reduction of immune checkpoint inhibitors and polarize T cells to a protective immune response. We treated SK-BR-3 cells with Herceptin and the STAT3-inhibitor (FLLL32) and assessed the apoptosis and expression of apoptosis-related proteins, VEGF, Her-2 and apoptosis targets of STAT3. PBMCs were isolated from healthy donors and co-cultured with SK-BR-3 cells in the presence or absence of Herceptin and FLLL32. PD-L1, CTLA-4, TIM-3 and T-cell intracellular cytokines were then evaluated. Our results demonstrated that STAT3 inhibition and Herceptin increased SK-BR-3 cell apoptosis, significantly. STAT3 inhibition through combination treatment had a more significant effect on regulating PD-1, TIM-3 and CTLA-4 expression on PBMCs. Alternatively, the combination of FLLL32 and Herceptin promoted T helper-1 protective immune response. The combination of FLLL32 and Herceptin suppress the expression of immune checkpoints and provoke the T-helper1 immune response in lymphocytes. Our analysis indicates STAT3 as a promising target that improves Herceptin's role in breast cancer cell apoptosis.

Design, Synthesis, and Biological Evaluation of Novel Quinazolin-4(3H)-One-Based Histone Deacetylase 6 (HDAC6) Inhibitors for Anticancer Activity

A series of novel quinazoline-4-(3H)-one derivatives were designed and synthesized as histone deacetylase 6 (HDAC6) inhibitors based on novel quinazoline-4-(3H)-one as the cap group and benzhydroxamic acid as the linker and metal-binding group. A total of 19 novel quinazoline-4-(3H)-one analogues (5a-5s) were obtained. The structures of the target compounds were characterized using ¹H-NMR, ¹³C-NMR, LC-MS, and elemental analyses. Characterized compounds were screened for inhibition against HDAC8 class I, HDAC4 class IIa, and HDAC6 class IIb. Among the compounds tested, 5b proved to be the most potent and selective inhibitor of HDAC6 with an IC₅₀ value 150 nM. Some of these compounds showed potent antiproliferative activity in several tumor cell lines (HCT116, MCF7, and B16). Amongst all the compounds tested for their anticancer effect against cancer cell lines, 5c emerged to be most active against the MCF-7 line with an IC₅₀ of 13.7 μM; it exhibited cell-cycle arrest in the G2 phase, as well as promoted apoptosis. Additionally, we noted a significant reduction in the colony-forming capability of cancer cells in the presence of 5c. At the intracellular level, selective inhibition of HDAC6 was enumerated by monitoring the acetylation of α-tubulin with a limited effect on acetyl-H3. Importantly, the obtained results suggested a potent effect of 5c at sub-micromolar concentrations as compared to the other molecules as HDAC6 inhibitors in vitro.

Combined therapeutic effect of YHO-1701 with PD-1 blockade is dependent on natural killer cell activity in syngeneic mouse models

The signal transducer and activator of transcription 3 (STAT3) signaling pathway is a key mediator of cancer cell proliferation, survival, and invasion. We discovered YHO-1701 as a small molecule inhibitor of STAT3 dimerization and demonstrated its potent anti-tumor activity using xenograft mouse models as monotherapy and combination therapy with molecular targeted drugs. STAT3 is also associated with cancer immune tolerance; therefore, we used the female CT26 syngeneic mouse model to examine the effect of combining YHO-1701 administration with PD-1/PD-L1 blockade. Pretreatment of the mice with YHO-1701 before starting anti-PD-1 antibody administration resulted in a significant therapeutic effect. In addition, the effect of monotherapy and combination treatment with YHO-1701 was significantly abolished by depleting natural killer (NK) cell activity. YHO-1701 was also found to restore the activity of mouse NK cells under inhibitory conditions in vitro. Furthermore, this combination therapy significantly inhibited tumor growth in an immunotherapy-resistant model of murine CMS5a fibrosarcoma. These results suggest that the combination of YHO-1701 with PD-1/PD-L1 blockade might be a new candidate for cancer immunotherapy involving the enhancement of NK cell activity in the tumor microenvironment.

B7H6 silencing increases chemosensitivity to dacarbazine and suppresses cell survival and migration in cutaneous melanoma

Cutaneous melanoma (CM) is a highly metastatic cancer whose incidence rate is heightening worldwide. B7H6, as one of the co-stimulatory ligands of the B7 family, is expressed in malignant cells, involved in tumorigenesis. This study aimed to investigate the significance of B7H6 in CM cell chemosensitivity and metastatic ability. A375 CM cells were transfected with B7H6-siRNA and treated with dacarbazine individually or combined. The MTT assay to estimate half-maximal inhibitory concentration of dacarbazine and cell viability, the apoptotic induction using Annexin V/PI, cell cycle progression via flow cytometry, and wound healing assay for determining the migration ability of cells and assessing the clonogenic potential of A375 cells were executed. Functional analyses were performed to evaluate changes in A375 cells. The results illustrated that B7H6 suppression significantly increased the chemosensitivity of A375 cells to dacarbazine. Apoptosis induction by dacarbazine was enhanced after B7H6 knockdown through modulating Caspase-3, Bax, and Bcl-2 mRNA levels. Western blotting indicated enhancement of cleaved caspase-3 protein expression in treatment groups. A375 cells were arrested at the sub-G1 and S phases when using B7H6-siRNA and dacarbazine. B7H6 suppression combined with dacarbazine restrained cell migration through suppression of matrix metalloproteinase (MMP) expression, including MMP2, MMP3, and MMP9. In addition, the clonogenic ability of A375 cells was decreased by downregulating Sox2, Nanog, and CD44 mRNA levels. A visible decrement in STAT3 protein expression was observed in the combination group. Hence, our findings revealed that B7H6 knockdown with dacarbazine could be a promising treatment approach for cutaneous melanoma.

Inflammatory Networks in Renal Cell Carcinoma

Cancer-associated inflammation has been established as a hallmark feature of almost all solid cancers. Tumor-extrinsic and intrinsic signaling pathways regulate the process of cancer-associated inflammation. Tumor-extrinsic inflammation is triggered by many factors, including infection, obesity, autoimmune disorders, and exposure to toxic and radioactive substances. Intrinsic inflammation can be induced by genomic mutation, genome instability and epigenetic remodeling in cancer cells that promote immunosuppressive traits, inducing the recruitment and activation of inflammatory immune cells. In RCC, many cancer cell-intrinsic alterations are assembled, upregulating inflammatory pathways, which enhance chemokine release and neoantigen expression. Furthermore, immune cells activate the endothelium and induce metabolic shifts, thereby amplifying both the paracrine and autocrine inflammatory loops to promote RCC tumor growth and progression. Together with tumor-extrinsic inflammatory factors, tumor-intrinsic signaling pathways trigger a Janus-faced tumor microenvironment, thereby simultaneously promoting or inhibiting tumor growth. For therapeutic success, it is important to understand the pathomechanisms of cancer-associated inflammation, which promote cancer progression. In this review, we describe the molecular mechanisms of cancer-associated inflammation that influence cancer and immune cell functions, thereby increasing tumor malignancy and anti-cancer resistance. We also discuss the potential of anti-inflammatory treatments, which may provide clinical benefits in RCCs and possible avenues for therapy and future research.

B cell-intrinsic STAT3-mediated support of latency and interferon suppression during murine gammaherpesvirus 68 infection revealed through an in vivo competition model

Cancers associated with the oncogenic gammaherpesviruses, Epstein-Barr virus and Kaposi sarcoma herpesvirus, are notable for their constitutive activation of the transcription factor STAT3. To better understand the role of STAT3 during gammaherpesvirus latency and immune control, we utilized murine gammaherpesvirus 68 (MHV68) infection. Genetic deletion of STAT3 in B cells of CD19cre/+Stat3f/f mice reduced peak latency approximately 7-fold. However, infected CD19cre/+Stat3f/f mice exhibited disordered germinal centers and heightened virus-specific CD8 T cell responses compared to WT littermates. To circumvent the systemic immune alterations observed in the B cell-STAT3 knockout mice and more directly evaluate intrinsic roles for STAT3, we generated mixed bone marrow chimeras consisting of WT and STAT3-knockout B cells. Using a competitive model of infection, we discovered a dramatic reduction in latency in STAT3-knockout B cells compared to their WT B cell counterparts in the same lymphoid organ. RNA sequencing of sorted germinal center B cells revealed that STAT3 promotes proliferation and B cell processes of the germinal center but does not directly regulate viral gene expression. Last, this analysis uncovered a STAT3-dependent role for dampening type I IFN responses in newly infected B cells. Together, our data provide mechanistic insight into the role of STAT3 as a latency determinant in B cells for oncogenic gammaherpesviruses.

Overcoming Acquired Drug Resistance to Cancer Therapies through Targeted STAT3 Inhibition

Anti-neoplastic agents for cancer treatment utilize many different mechanisms of action and, when combined, can result in potent inhibition of cancer growth. Combination therapies can result in long-term, durable remission or even cure; however, too many times, these anti-neoplastic agents lose their efficacy due to the development of acquired drug resistance (ADR). In this review, we evaluate the scientific and medical literature that elucidate STAT3-mediated mechanisms of resistance to cancer therapeutics. Herein, we have found that at least 24 different anti-neoplastic agents-standard toxic chemotherapeutic agents, targeted kinase inhibitors, anti-hormonal agents, and monoclonal antibodies-that utilize the STAT3 signaling pathway as one mechanism of developing therapeutic resistance. Targeting STAT3, in combination with existing anti-neoplastic agents, may prove to be a successful therapeutic strategy to either prevent or even overcome ADR to standard and novel cancer therapies.

The complex network of transcription factors, immune checkpoint inhibitors and stemness features in colorectal cancer: A recent update

Cancer immunity is regulated by several mechanisms that include co-stimulatory and/or co-inhibitory molecules known as immune checkpoints expressed by the immune cells. In colorectal cancer (CRC), CTLA-4, LAG3, TIM-3 and PD-1 are the major co-inhibitory checkpoints involved in tumor development and progression. On the other hand, the deregulation of transcription factors and cancer stem cells activity plays a major role in the development of drug resistance and in the spread of metastatic disease in CRC. In this review, we describe how the modulation of such transcription factors affects the response of CRC to therapies. We also focus on the role of cancer stem cells in tumor metastasis and chemoresistance and discuss both preclinical and clinical approaches for targeting stem cells to prevent their tumorigenic effect. Finally, we provide an update on the clinical applications of immune checkpoint inhibitors in CRC and discuss the regulatory effects of transcription factors on the expression of the immune inhibitory checkpoints with specific focus on the PD-1 and PD-L1 molecules.

Emphasis on Adipocyte Transformation: Anti-Inflammatory Agents to Prevent the Development of Cancer-Associated Adipocytes

Of the various cell types in the tumor microenvironment (TME), adipocytes undergo a dynamic transformation when activated by neighboring cancer cells. Although these adipocytes, known as cancer-associated adipocytes (CAAs), have been reported to play a crucial role in tumor progression, the factors that mediate their transformation remain elusive. In this review, we discuss the hypothesis that inflammatory signals involving NF-ĸB activation can induce lipolysis and adipocyte dedifferentiation. This provides a mechanistic understanding of CAA formation and introduces the concept of preventing adipocyte transformation via anti-inflammatory agents. Indeed, epidemiological studies indicate a higher efficacy of nonsteroidal anti-inflammatory drugs (NSAIDs) in obese patients with cancer, suggesting that NSAIDs can modulate the TME. Inhibition of cyclooxygenase-2 (COX-2) and prostaglandin production leads to the suppression of inflammatory signals such as NF-ĸB. Thus, we suggest the use of NSAIDs in cancer patients with metabolic disorders to prevent the transformation of TME components. Moreover, throughout this review, we attempt to expand our knowledge of CAA transformation to improve the clinical feasibility of targeting CAAs.

Breast cancer tumor microenvironment affects Treg/IL-17-producing Treg/Th17 cell axis: Molecular and therapeutic perspectives

The tumor microenvironment (TME) comprises a variety of immune cells, among which T cells exert a prominent axial role in tumor development or anti-tumor responses in patients with breast cancer (BC). High or low levels of anti-inflammatory cytokines, such as transforming growth factor β, in the absence or presence of proinflammatory cytokines, such as interleukin-6 (IL-6), delineate the fate of T cells toward either regulatory T (Treg) or T helper 17 (Th17) cells, respectively. The transitional state of RORγt⁺Foxp3⁺ Treg (IL-17-producing Treg) resides in the middle of this reciprocal polarization, which is known as Treg/IL-17-producing Treg/Th17 cell axis. TME secretome, including microRNAs, cytokines, and extracellular vesicles, can significantly affect this axis. Furthermore, immune checkpoint inhibitors may be used to reconstruct immune cells; however, some of these novel therapies may favor tumor development. Therefore, understanding secretory and cell-associated factors involved in their differentiation or polarization and functions may be targeted for BC management. This review discusses microRNAs, cytokines, and extracellular vesicles (as secretome), as well as transcription factors and immune checkpoints (as cell-associated factors), which influence the Treg/IL-17-producing Treg/Th17 cell axis in BC. Furthermore, approved or ongoing clinical trials related to the modulation of this axis in the TME of BC are described to broaden new horizons of promising therapeutic approaches.

A cohort study using IL-6/Stat3 activity and PD-1/PD-L1 expression to predict five-year survival for patients after gastric cancer resection

OBJECTIVES

The expression/activation of IL-6, p-Stat3, PD-1 and PD-L1 in gastric cancer (GC) tissues were examined to evaluate their abilities in predicting the survival prognosis in postoperative patients with GC.

METHODS

The clinicopathological data and paraffin-embedded tissues of 205 patients who underwent gastric cancer resection were collected at the First Affiliated Hospital of Shihezi University School of Medicine, and the patients were followed-up annually after surgery. Immunohistochemistry (IHC) was used to detect the expression of IL-6, p-Stat3, PD-1 and PD-L1 proteins using tissue microarrays derived from these patients. Statistical analyses were performed using non-parametric tests, Spearman's correlation, ROC curves, Kaplan-Meier survival analysis, Cox single-factor and multifactor regression models. In comparison, the analyses were also performed for GC patients from public databases (407 patients from TCGA and 433 patients from GEO, respectively).

RESULTS

(1) The expression levels of IL-6, p-Stat3, PD-1 and PD-L1 in GC tissues were significantly higher than adjacent normal tissues (ANT) (81.01% vs. 52.78%, P<0.001; 100% vs. 93.41%, P<0.001; 58.58% vs. 40.12%, P<0.001; 38.20% vs. 26.90%, P = 0.025, respectively). The mean optical density (MOD) values of IL-6, p-Stat3, PD-1 and PD-L1 were significantly higher in GC tissues. (2) The higher the levels of IL-6 (P<0.001), p-Stat3 (P<0.001), and PD-L1 (P = 0.003) were, the worse the survival prognoses were observed, respectively, among GC patients. The expression of PD-1 was not correlated with the prognosis of GC patients (P>0.05). The lower the degree of cell differentiation (P<0.001) was, the worse the survival prognoses were observed among GC patients. (3) Independent risk factors for postoperative prognosis in GC patients included age (≥60 years old), poor cell differentiation, invasion depth (T3/T4), lymph node metastasis (N1-3), distant metastasis (M1), and high levels of IL-6 (2+/3+). (4) A multi-factor combination (cell differentiation+IL-6+p-Stat3+PD-1+PD-L1) appeared to be the best survival predictor for GC patients as indicated by AUC (AUC 0.782, 95% CI = 0.709, 0.856, P<0.001). This combination may be the optimal predictor for postoperative survival of GC patients. (5) The levels of IL-6, p-Stat3, PD-1 and PD-L1 correlated with the infiltration levels of various tumor-infiltrating immune cells. (6) The analyses of ROC curves, calibration, DCA and Kaplan-Meier (KM) survival curves in TCGA dataset confirmed that the nomogram model could accurately predict the prognosis in GC patients.

CONCLUSIONS

(1) The expressed levels of IL-6, p-Stat3, PD-1 and PD-L1 are higher in GC tissues than in adjacent normal tissues. (2) The high levels of IL-6, p-Stat3 and PD-L1 are correlated with poor survival in GC patients. (3) The high levels of IL-6, p-Stat3, PD-1 and PD-L1 have influences in GC tumor microenvironment. (4) The multi-predictor combination of "IL-6+p-Stat3+PD-1+cell differentiation" serves as an optimal survival predictor for postoperative GC patients and better than the TNM staging system. As these molecules can be examined in preoperative biopsies, these observations may provide a useful guide for clinicians to strategize individualized surgical plans for GC patients before surgery.

The combination of SMRT sequencing and Illumina sequencing highlights organ-specific and age-specific expression patterns of miRNAs in Sika Deer

Due to the lack of high-quality Sika Deer (Cervus nippon) transcriptome and sRNAome across multiple organs or development stages, it is impossible to comprehensively analyze the mRNA and miRNA regulatory networks related to growth, development and immunity response. In this study, we used single molecule-real time sequencing (SMRT-seq) and Illumina sequencing methods to generate transcriptome and sRNAome from ten tissues and four age groups of Sika Deer to help us understand molecular characteristics and global miRNA expression profiles. The results showed that a total of 240,846 consensus transcripts were generated with an average length of 2,784 bp. 4,329 Transcription factors (TFs), 109,000 Simple Sequence Repeats (SSRs) and 18,987 Long non-coding RNAs (LncRNAs) were identified. Meanwhile, 306 known miRNAs and 143 novel miRNAs were obtained. A large number of miRNAs showed organ-specific and age-specific differential expression patterns. In particular, we found that the organ-specific miRNAs were enriched in the brain, some of which shared only between the brain and adrenal. These miRNAs were involved in maintaining specific functions within the brain and adrenal. By constructing miRNA96mRNA interaction networks associated with Sika Deer immunity, we found that miRNAs (miR-148a, miR-26a, miR-214, let-7b, etc.) and mRNAs (CD6, TRIM38, C3, CD163, etc.) might play an important role in the immune response of Sika Deer spleen. Together, our study generated an improved transcript annotation for Sika Deer by SMRT-seq and revealed the role of miRNA in regulating the growth, development and immunity response of Sika Deer.

Discovery of selective HDAC6 inhibitors capped by flavonoid or flavonoid-analogous moieties as anti-cancer therapeutics simultaneously harboring anti-proliferative and immunomodulatory activities

Specific HDAC6 inhibitors (HDAC6is) simultaneously harboring anti-proliferative and immunomodulatory properties may prohibit tumor progression via intrinsic and immune driven effects. Herein, built upon the structurally novel lead TFH-7, structure-activity relationship study culminated in the identification of azaflavone-capped compound 20, which exhibited comparable HDAC6 inhibitory activity (IC₅₀ = 8.5 nM) to that of Tubastatin A, a highly selective HDAC6i, as well as favorable subtype specificity. Importantly, concurrent with its impressive anti-proliferative efficacy against several solid tumor cell lines, 20 remarkably alleviated the transduction of immune-related STAT3 signaling and attenuated the expression of immunosuppressive checkpoint PD-L1 at submicromolar concentration, highlighting the immunomodulatory properties. Moreover, consistent with its favorable subtype selectivity, 20 displayed low cytotoxicity against normal human umbilical vein endothelial cells, revealing a promising safety profile. Following the intravenous administration, it demonstrated acceptable elimination half-life and exposure in Sprague-Dawley rats. Hence, the extensive functional investigation or structural modification of 20 is valuable.

Inhibiting STAT3 signaling pathway by natural products for cancer prevention and therapy: In vitro and in vivo activity and mechanisms of action

Signal transducer and activator of transcription 3 (STAT3) plays a critical role in signal transmission from the plasma membrane to the nucleus, regulating the expression of genes involved in essential cell functions and controlling the processes of cell cycle progression and apoptosis. Thus, STAT3 has been elucidated as a promising target for developing anticancer drugs. Many natural products have been reported to inhibit the STAT3 signaling pathway during the past two decades and have exhibited significant anticancer activities in vitro and in vivo. However, there is no FDA-approved STAT3 inhibitor yet. The major mechanisms of these natural product inhibitors of the STAT3 signaling pathway include targeting the upstream regulators of STAT3, directly binding to the STAT3 SH2 domain and inhibiting its activation, inhibiting STAT3 phosphorylation and/or dimerization, and others. In the present review, we have systematically discussed the development of these natural product inhibitors of STAT3 signaling pathway as well as their in vitro and in vivo anticancer activity and mechanisms of action. Outlooks and perspectives on the associated challenges are provided as well.

Therapy resistance: opportunities created by adaptive responses to targeted therapies in cancer

Normal cells explore multiple states to survive stresses encountered during development and self-renewal as well as environmental stresses such as starvation, DNA damage, toxins or infection. Cancer cells co-opt normal stress mitigation pathways to survive stresses that accompany tumour initiation, progression, metastasis and immune evasion. Cancer therapies accentuate cancer cell stresses and invoke rapid non-genomic stress mitigation processes that maintain cell viability and thus represent key targetable resistance mechanisms. In this Review, we describe mechanisms by which tumour ecosystems, including cancer cells, immune cells and stroma, adapt to therapeutic stresses and describe three different approaches to exploit stress mitigation processes: (1) interdict stress mitigation to induce cell death; (2) increase stress to induce cellular catastrophe; and (3) exploit emergent vulnerabilities in cancer cells and cells of the tumour microenvironment. We review challenges associated with tumour heterogeneity, prioritizing actionable adaptive responses for optimal therapeutic outcomes, and development of an integrative framework to identify and target vulnerabilities that arise from adaptive responses and engagement of stress mitigation pathways. Finally, we discuss the need to monitor adaptive responses across multiple scales and translation of combination therapies designed to take advantage of adaptive responses and stress mitigation pathways to the clinic.

Immune Subtype Profiling and Establishment of Prognostic Immune-Related lncRNA Pairs in Human Ovarian Cancer

This study collected immune-related genes (IRGs) and used gene expression data from TCGA database to construct a molecular subtype of ovarian cancer (OV) based on immune-related lncRNA gene pairs (IRLnc_GPs). The relationships between molecular subtypes and prognosis and clinical characteristics were further explored. IRGs were acquired from the ImmPort database, and round-robin pairing of immune-related lncRNAs was performed. The NMF algorithm was used to identify molecular subtypes, and the immune score of a single sample was calculated through ESTIMATE, TIMER, ssGSEA, MCPcounter, and CIBERSORT. The relationship between molecular subtypes and immune microenvironments was identified. A hypergeometric test was used to test the lncRNA pairs among the OV molecular subtypes (C1 and C2 subtypes). The BH method was used to screen the different lncRNA pairs, and a predictive risk model was constructed and verified. Finally, correlation analysis between the risk model, immune checkpoint genes, and chemotherapy drugs was carried out. Based on IRLnc_GP to classify 373 OV samples of TCGA, the samples were divided into two subtypes, and the prognosis between the subtypes showed significant differences. The C1 subtype with a poor prognosis was more related to the pathways of tumor occurrence and development. We identified 180 differential lncRNA pairs between subtypes and constructed a prognostic risk model based on 8 IRLnc_GPs. In the independent dataset, the distribution of subtypes in functional modules was different and highly repeatable. There were significant differences in the molecular and clinical characteristics of the subtypes and the drug sensitivity of immunotherapy/chemotherapy. In conclusion, the risk model established based on IRLnc_GP can better evaluate the prognosis of OV samples and can also assess the effects of different drug treatments in the high- and low-risk groups, providing new insights and ideas for the treatment of OV.

STAT1 and STAT3 Exhibit a Crosstalk and Are Associated with Increased Inflammation in Hepatocellular Carcinoma

Simple Summary

Liver cancer is the fourth-leading cause of cancer-related mortality worldwide and lacks effective therapies. Hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA) are the two most common types of liver cancer and both are associated with underlying inflammatory diseases. Thereby, interleukin-6 (IL-6)-mediated STAT3 signaling is critically involved in early carcinogenesis and disease progression. Here, we assessed the interplay between STAT1 and STAT3 in IL-6 signaling in vitro and studied the activation of STAT1 and STAT3 in a cohort of 124 HCC and a cohort of 138 CCA patients by immunohistochemistry. We found that IL-6 induced STAT1 transcriptional activity upon STAT3 depletion, suggesting that HCC tumor cells may activate both STAT1 and STAT3 signaling under pro-inflammatory conditions. Furthermore, HCC patient tissues showed a strong positive correlation of STAT1 and STAT3 activation in distinct patient groups. These patients also exhibited a high degree of immune cell infiltration, suggesting that these tumors are immune “hot”.

Abstract

Liver cancers, which are mostly hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA), are very aggressive tumors with poor prognosis. Therapeutic options with curative intent are largely limited to surgery and available systemic therapies show limited benefit. Signal transducer and activator of transcription 1 (STAT1) and 3 (STAT3) are key transcription factors activated by pro-inflammatory cytokines such as interferon-γ (IFN-γ) and interleukin-6 (IL-6). In this study, we combined in vitro cell culture experiments and immunohistochemical analyses of human HCC (N = 124) and CCA (N = 138) specimens. We observed that in the absence of STAT3, IL-6 induced the activation of STAT1 and its target genes suggesting that IL-6 derived from the tumor microenvironment may activate both STAT1 and STAT3 target genes in HCC tumor cells. In addition, STAT1 and STAT3 were highly activated in a subset of HCC, which exhibited a high degree of infiltrating CD8- and FOXP3-positive immune cells and PD-L1 expression. Our results demonstrate that STAT1 and STAT3 are expressed and activated in HCC and tumor infiltrating immune cells. In addition, HCC cases with high STAT1 and STAT3 expression also exhibited a high degree of immune cell infiltration, suggesting increased immunological tolerance.

TLR4 and pSTAT3 Expression on Circulating Tumor Cells (CTCs) and Immune Cells in the Peripheral Blood of Breast Cancer Patients: Prognostic Implications

TLR4 and pSTAT3 are key players in cancer inflammation and immune evasion; however, their role in the peripheral blood (PB) is largely unexplored. Herein we evaluated their expression in the circulating tumor cells (CTCs) and peripheral-blood mononuclear cells (PBMCs) of patients with early (n = 99) and metastatic (n = 100) breast cancer (BC). PB samples obtained prior to adjuvant and first-line therapy, were immunofluorescently stained for Cytokeratins/TLR4/pSTAT3/DAPI and analyzed via Ariol microscopy. TLR4+ CTCs were detected in 50% and 68% of early and metastatic CTC-positive patients, respectively, and pSTAT3+ CTCs in 83% and 68%, respectively. In metastatic patients, CTC detection was associated with a high risk of death (HR: 1.764, p = 0.038), while TLR4+ CTCs correlated with a high risk of disease progression (HR: 1.964, p = 0.030). Regarding PBMCs, TLR4 expression prevailed in metastatic disease (p = 0.029), while pSTAT3 expression was more frequent in early disease (p = 0.014). In early BC, TLR4 expression on PBMCs independently predicted for high risk of relapse (HR: 3.549; p = 0.009), whereas in metastatic BC, TLR4+/pSTAT3- PBMCs independently predicted for high risk of death (HR: 2.925; p = 0.012). These results suggest that TLR4/pSTAT3 signaling on tumor- and immune-cell compartments in the PB could play a role in BC progression, and may hold independent prognostic implications for BC patients.