Molecular mechanism, regulation, and therapeutic targeting of the STAT3 signaling pathway in esophageal cancer (Review)

Deciphering STAT3's negative regulation of LHPP in ESCC progression through single-cell transcriptomics analysis

BACKGROUND

Esophageal Squamous Cell Carcinoma (ESCC) remains a predominant health concern in the world, characterized by high prevalence and mortality rates. Advances in single-cell transcriptomics have revolutionized cancer research by enabling a precise dissection of cellular and molecular diversity within tumors.

OBJECTIVE

This study aims to elucidate the cellular dynamics and molecular mechanisms in ESCC, focusing on the transcriptional influence of STAT3 (Signal Transducer and Activator of Transcription 3) and its interaction with LHPP, thereby uncovering potential therapeutic targets.

METHODS

Single-cell RNA sequencing was employed to analyze 44,206 cells from tumor and adjacent normal tissues of ESCC patients, identifying distinct cell types and their transcriptional shifts. We conducted differential gene expression analysis to assess changes within the tumor microenvironment (TME). Validation of key regulatory interactions was performed using qPCR in a cohort of 21 ESCC patients and further substantiated through experimental assays in ESCC cell lines.

RESULTS

The study revealed critical alterations in cell composition and gene expression across identified cell populations, with a notable shift towards pro-tumorigenic states. A significant regulatory influence of STAT3 on LHPP was discovered, establishing a novel aspect of ESCC pathogenesis. Elevated levels of STAT3 and suppressed LHPP expression were validated in clinical samples. Functional assays confirmed that STAT3 directly represses LHPP at the promoter level, and disruption of this interaction by promoter mutations diminished STAT3's repressive effect.

CONCLUSION

This investigation underscores the central role of STAT3 as a regulator in ESCC, directly impacting LHPP expression and suggesting a regulatory loop crucial for tumor behavior. The insights gained from our comprehensive cellular and molecular analysis offer a deeper understanding of the dynamics within the ESCC microenvironment. These findings pave the way for targeted therapeutic interventions focusing on the STAT3-LHPP axis, providing a strategic approach to improve ESCC management and prognosis.

Altered Microbiome Promotes Pro-Inflammatory Pathways in Oesophago-Gastric Tumourigenesis

INTRODUCTION

The upper gastrointestinal microbiome is a dynamic entity that is involved in numerous processes including digestion, production of vitamins and protection against pathogens. Many external and intrinsic factors may cause changes in the proportions of bacteria within the microbial community, termed 'dysbiosis'. A number of these have been identified as risk factors for a range of diseases, including oesophago-gastric carcinoma.

MATERIALS AND METHODS

A narrative review was conducted to elucidate the current evidence on the role of the microbiome in promoting oesophago-gastric tumourigenesis. Significant causes of dysbiosis including age, medications and GORD were examined and key pro-inflammatory pathways implicated in tumourigenesis and their interaction with the microbiome were described.

RESULTS AND DISCUSSION

An association between microbial dysbiosis and development of oesophago-gastric cancer may be mediated via activation of pro-inflammatory pathways, the inflammasome and the innate immune system. Advances in sequencing technology allow microbial communities to be fingerprinted by sequencing the 16S rRNA gene, enabling a deeper understanding of the genera that may be implicated in driving tumourigenesis.

CONCLUSIONS

Developing a greater understanding of the influence of the microbiota on oesophago-gastric tumourigenesis may enable advances to be made in the early detection of malignancy and in the development of novel systemic therapies, leading to improved rates of survival.

Exploring the Potential of Ellagic Acid in Gastrointestinal Cancer Prevention: Recent Advances and Future Directions

Gastrointestinal (GI) cancers are a significant global health concern with diverse etiologies and limited treatment options. Ellagic acid (EA), a natural polyphenolic compound, exhibits promising anticancer properties against various GI malignancies. In this article, we have reviewed recent research on the anticancer potential of EA across esophageal, gastric, colorectal, pancreatic, and liver cancers. In esophageal cancer, EA inhibits the formation of O6-methylguanine (O6-meGua) adducts induced by carcinogens like N-nitrosomethylbenzylamine (NMBA), thereby suppressing tumor growth. Additionally, EA inhibits STAT3 signaling and stabilizes tumor suppressor proteins, showing potential as an anti-esophageal cancer agent. In gastric cancer, EA regulates multiple pathways involved in cell proliferation, invasion, and apoptosis, including the p53 and PI3K-Akt signaling pathways. It also demonstrates anti-inflammatory and antioxidant effects, making it a promising therapeutic candidate against gastric cancer. In colorectal cancer (CRC), EA inhibits cell proliferation, induces apoptosis, and modulates the Wnt/β-catenin and PI3K/Akt pathways, suggesting its efficacy in preventing CRC progression. Furthermore, EA has shown promise in pancreatic cancer by inhibiting nuclear factor-kappa B, inducing apoptosis, and suppressing epithelial-mesenchymal transition. In liver cancer, EA exhibits radio-sensitizing effects, inhibits inflammatory pathways, and modulates the tumor microenvironment, offering potential therapeutic benefits against hepatocellular carcinoma. Studies on EA potential in combination therapies and the development of targeted delivery systems are required for enhanced efficacy against gastrointestinal cancers.

PARG Promotes Esophagus Cancer Cell Metastasis by Activation of the Wnt/β-Catenin Pathway

Esophagus cancer (EC) is a highly malignant and metastatic cancer. Poly(ADP-ribose) glycohydrolase (PARG), a DNA replication and repair regulator, inhibits cancer cell replication defects. This study aimed to explore the role of PARG in EC. The biological behaviors were analyzed using MTT assay, Transwell assay, scratch test, cell adhesion assay, and western blot. PARG expression was detected using quantitative PCR and immunohistochemical assay. The regulation of the Wnt/β-catenin pathway was assessed using western blot. The results showed that PARG was highly expressed in EC tissues and cells. Knockdown of PARG suppressed cell viability, invasion, migration, adhesion, and epithelial-mesenchymal transition. Conversely, overexpression of PARG promoted the biological behaviors mentioned above. Moreover, overexpression of PARG promoted the activation of the Wnt/β-catenin pathway rather than the STAT and Notch pathways. XAV939, the Wnt/β-catenin pathway inhibitor, partly abolished the biological behaviors mediated by PARG overexpression. In conclusion, PARG promoted the malignant advancement of EC via activating the Wnt/β-catenin pathway. These findings suggested that PARG might be a new therapeutic target for EC.

The oncogenic mechanisms of the Janus kinase-signal transducer and activator of transcription pathway in digestive tract tumors

Digestive tract tumors are heterogeneous and involve the dysregulation of multiple signaling pathways. The Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway plays a notable role in the oncogenesis of digestive tract tumors. Typically activated by pro-inflammatory cytokines, it regulates important biological processes, such as cell growth, differentiation, apoptosis, immune responses, and inflammation. The aberrant activation of this pathway manifests in different forms, including mutations in JAKs, overexpression of cytokine receptors, and sustained STAT activation, and contributes to promoting the malignant characteristics of cancer cells, including uncontrolled proliferation, resistance to apoptosis, enhanced invasion and metastasis, angiogenesis, acquisition of stem-like properties, and drug resistance. Numerous studies have shown that aberrant activation of the JAK-STAT pathway is closely related to the development and progression of digestive tract tumors, contributing to tumor survival, angiogenesis, changes in the tumor microenvironment, and even immune escape processes. In addition, this signaling pathway also affects the sensitivity of digestive tract tumors to chemotherapy and targeted therapy. Therefore, it is crucial to comprehensively understand the oncogenic mechanisms underlying the JAK-STAT pathway in order to develop effective therapeutic strategies against digestive tract tumors. Currently, several JAK-STAT inhibitors are undergoing clinical and preclinical trials as potential treatments for various human diseases. However, further investigation is required to determine the role of this pathway, as well as the effectiveness and safety of its inhibitors, especially in the context of digestive tract tumors. In this review, we provide an overview of the structure, classic activation, and negative regulation of the JAK-STAT pathway. Furthermore, we discuss the pathogenic mechanisms of JAK-STAT signaling in different digestive tract tumors, with the aim of identifying potential novel therapeutic targets. Video Abstract.

Natural bioactive compounds and STAT3 against hepatocellular carcinoma: An update

Hepatocellular carcinoma (HCC) is a challenging and very fatal liver cancer. The signal transducer and activator of transcription 3 (STAT3) pathway is a crucial regulator of tumor development and are ubiquitously active in HCC. Therefore, targeting STAT3 has emerged as a promising approach for preventing and treating HCC. Various natural bioactive compounds (NBCs) have been proven to target STAT3 and have the potential to prevent and treat HCC as STAT3 inhibitors. Numerous kinds of STAT3 inhibitors have been identified, including small molecule inhibitors, peptide inhibitors, and oligonucleotide inhibitors. Due to the undesirable side effects of the conventional therapeutic drugs against HCC, the focus is shifted to NBCs derived from plants and other natural sources. NBCs can be broadly classified into the categories of terpenes, alkaloids, carotenoids, and phenols. Most of the compounds belong to the family of terpenes, which prevent tumorigenesis by inhibiting STAT3 nuclear translocation. Further, through STAT3 inhibition, terpenes downregulate matrix metalloprotease 2 (MMP2), matrix metalloprotease 9 (MMP9) and vascular endothelial growth factor (VEGF), modulating metastasis. Terpenes also suppress the anti-apoptotic proteins and cell cycle markers. This review provides comprehensive information related to STAT3 abrogation by NBCs in HCC with in vitro and in vivo evidences.

Multifaceted approach toward mapping out the anticancer properties of small molecules via in vitro evaluation on melanoma and nonmelanoma skin cancer cells, and in silico target fishing

Melanoma and nonmelanoma skin cancers are among the most prevalent and most lethal forms of skin cancers. To identify new lead compounds with potential anticancer properties for further optimization, in vitro assays combined with in-silico target fishing and docking have been used to identify and further map out the antiproliferative and potential mode of action of molecules from a small library of compounds previously prepared in our laboratory. From screening these compounds in vitro against A375, SK-MEL-28, A431, and SCC-12 skin cancer cell lines, 35 displayed antiproliferative activities at the micromolar level, with the majority being primarily potent against the A431 and SCC-12 squamous carcinoma cell lines. The most active compounds 11 (A431: IC50  = 5.0 μM, SCC-12: IC50  = 2.9 μM, SKMEL-28: IC50  = 4.9 μM, A375: IC50  = 6.7 μM) and 13 (A431: IC50  = 5.0 μM, SCC-12: IC50  = 3.3 μM, SKMEL-28: IC50  = 13.8 μM, A375: IC50  = 17.1 μM), significantly and dose-dependently induced apoptosis of SCC-12 and SK-MEL-28 cells, as evidenced by the suppression of Bcl-2 and upregulation of Bax, cleaved caspase-3, caspase-9, and PARP protein expression levels. Both agents significantly reduced scratch wound healing, colony formation, and expression levels of deregulated cancer molecular targets including RSK/Akt/ERK1/2 and S6K1. In silico target prediction and docking studies using the SwissTargetPrediction web-based tool suggested that CDK8, CLK4, nuclear receptor ROR, tyrosine protein-kinase Fyn/LCK, ROCK1/2, and PARP, all of which are dysregulated in skin cancers, might be prospective targets for the two most active compounds. Further validation of these targets by western blot analyses, revealed that ROCK/Fyn and its associated Hedgehog (Hh) pathways were downregulated or modulated by the two lead compounds. In aggregate, these results provide a strong framework for further validation of the observed activities and the development of a more comprehensive structure-activity relationship through the preparation and biological evaluation of analogs.

Presence of Activated (Phosphorylated) STAT3 in Radiation Necrosis Following Stereotactic Radiosurgery for Brain Metastases

Brain radiation necrosis (RN) is a subacute or late adverse event following radiotherapy, involving an exacerbated inflammatory response of the brain tissue. The risk of symptomatic RN associated with stereotactic radiosurgery (SRS) as part of the treatment of brain metastases (BMs) has been a subject of recent investigation. The activation of the signal transducer and activator of transcription 3 (STAT3) was shown in reactive astrocytes (RA) associated with BMs. Given that the pathophysiological mechanisms behind RN are not fully understood, we sought to investigate the role of STAT3 among other inflammatory markers in RN development. A mouse model of RN using clinical LINAC-based SRS was designed to induce brain necrosis with the administration of 50 Gy in a single fraction to the left hemisphere using a circular collimator of 5 mm diameter. Immunohistochemistry and multiplex staining for CD4, CD8, CD68, GFAP, and STAT3 were performed. For validation, eleven patients with BMs treated with SRS who developed symptomatic RN and required surgery were identified to perform staining for CD68, GFAP, and STAT3. In the mouse model, the RN and perinecrotic areas showed significantly higher staining for F4/80+ and GFAP+ cells, with a high infiltration of CD4 and CD8 T-lymphocytes, when compared to the non-irradiated cerebral hemisphere. A high number of GFAP+pSTAT3+ and F4/80+pSTAT3+ cells was found in the RN areas and the rest of the irradiated hemisphere. The analysis of human brain specimens showed that astrocytes and microglia were actively phosphorylating STAT3 in the areas of RN and gliosis. Phosphorylated STAT3 is highly expressed in the microglia and RA pertaining to the areas of brain RN. Targeting STAT3 via inhibition represents a promising strategy to ameliorate symptomatic RN in BM patients undergoing SRS.

Pharmacological anti-tumor effects of natural Chamaecyparis obtusa (siebold & zucc.) endl. Leaf extracts on breast cancer

ETHNOPHARMACOLOGICAL RELEVANCE

Chamaecyparis obtusa (C. obtusa, cypress species) is a plant that grows mainly in the temperate Northern Hemisphere and has long been used as a traditional anti-inflammatory treatment in East Asia. C. obtusa contains phytoncides, flavonoids, and terpenes, which have excellent anti-cancer effects and have been reported to prevent the progression of various cancers. However, the detailed mechanisms underlying the anti-cancer effects of C. obtusa extracts are unknown.

AIM OF THE STUDY

We sought to confirm the anti-cancer effects of C. obtusa leaf extracts and to reveal the mechanism of action, with the possibility of its application in the treatment or prevention of cancer.

MATERIAL &METHODS

The cytotoxicity of C. obtusa leaf extracts was confirmed using an MTT assay. Intracellular changes in protein levels were measured by immunoblotting, and mRNA levels were measured with qRT-PCR. Wound healing assay and transwell migration assay were used to evaluate the metastatic potential of breast cancer cells. The extract-induced apoptosis was observed using IncuCyte Annexin V Red staining analysis. A syngeneic breast cancer mouse model was established by injecting 4T1-Luc mouse breast cancer cells into the fat pad of female BALB/c mice, and the extract was administered orally. Luciferin solution was injected intraperitoneally to assess primary tumor development and metastasis by bioluminescence.

RESULTS

C. obtusa leaf extracts were extracted with boiling water, 70% EtOH, and 99% EtOH. Among the extracts, the 99% EtOH extract of C. obtusa leaf (CO99EL) most clearly inhibited the tyrosine phosphorylation of Signal Transducer and Activator of Transcription 3 (pY-STAT3) in MDA-MB-231 breast cancer cells at a concentration of 25 and 50 μg/mL. In addition, CO99EL strongly inhibited not only endogenous pY-STAT3 levels but also IL-6-induced STAT3 activation in various types of cancer cells, including breast cancer. CO99EL inhibited metastatic potential by downregulating the expression of N-cadherin, fibronectin, TWIST, MMP2, and MMP9 in MDA-MB-231 breast cancer cells. CO99EL also induced apoptotic cell death by increasing cleaved caspase-3 and decreasing anti-apoptotic proteins Bcl-2 and Bcl-xL. In an in vivo syngeneic breast cancer mouse model, 100 mg/kg CO99EL suppressed tumor growth and induced apoptosis of cancer cells. Moreover, CO99EL significantly inhibited lung metastasis from primary breast cancer.

CONCLUSIONS

Our study demonstrated that 100 mg/kg CO99EL has potent anti-tumor effects against breast cancer, thus suggesting that 100 mg/kg CO99EL has potential applications in the treatment and prevention of breast cancer.

Autoimmunity, cancer and COVID-19 abnormally activate wound healing pathways: critical role of inflammation

Recent evidence indicates that targeting IL-6 provides broad therapeutic approaches to several diseases. In patients with cancer, autoimmune diseases, severe respiratory infections [e.g. coronavirus disease 2019 (COVID-19)] and wound healing, IL-6 plays a critical role in modulating the systemic and local microenvironment. Elevated serum levels of IL-6 interfere with the systemic immune response and are associated with disease progression and prognosis. As already noted, monoclonal antibodies blocking either IL-6 or binding of IL-6 to receptors have been used/tested successfully in the treatment of rheumatoid arthritis, many cancer types, and COVID-19. Therefore, in the present review, we compare the impact of IL-6 and anti-IL-6 therapy to demonstrate common (pathological) features of the studied diseases such as formation of granulation tissue with the presence of myofibroblasts and deposition of new extracellular matrix. We also discuss abnormal activation of other wound-healing-related pathways that have been implicated in autoimmune disorders, cancer or COVID-19.

Clinicopathological Significance of STAT3 and p-STAT3 among 91 Patients with Adenocarcinoma of the Esophagogastric Junction

Adenocarcinoma of the esophagogastric junction (AEG) has increased rapidly worldwide during the last few decades. The purpose of this study is to investigate the clinical and prognostic characteristics of signal transduction and activator of transcription factor 3(STAT3) and phosphorylated STAT3 (p-STAT3) expression in AEG patients. We retrospectively analyzed the immunohistochemical results of 61 AEG patients and followed up for 5 years, while Western blot was performed on tissues from another 30 AEG patients. The results showed that STAT3 and p-STAT3 were overexpressed in AEG tissues (P < 0.05, P < 0.01). The high expression of STAT3 was significantly associated with the pTNM stage (P < 0.05), and the increased expression of p-STAT3 was significantly associated with depth of invasion (pT), lymph node metastasis (pN), and pTNM stage (P < 0.05, P < 0.05, P < 0.05). The 5-year survival rate for AEG patients was 41.0% and was significantly associated with tumor differentiation, pN, pTNM, and p-STAT3 (P < 0.05, P < 0.01, P < 0.05, P < 0.01). Cox regression analysis confirmed that tumor differentiation, pN, and high expression of p-STAT3 were independent risk factors for the 5-year survival rate in patients with AEG (P < 0.05, P < 0.01, P < 0.05). Our study showed that STAT3 and p-STAT3 play a critical role in AEG development.