The novel Aryl hydrocarbon receptor inhibitor biseugenol inhibits gastric tumor growth and peritoneal dissemination

The aryl hydrocarbon receptor as a tumor modulator: mechanisms to therapy

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that is widely recognized to play important, but complex, modulatory roles in a variety of tumor types. In this review, we comprehensively summarize the increasingly controversial role of AhR as a tumor regulator and the mechanisms by which it alters tumor progression based on the cancer cell type. Finally, we discuss new and emerging strategies to therapeutically modulate AhR, focusing on novel agents that hold promise in current human clinical trials as well as existing FDA-approved drugs that could potentially be repurposed for cancer therapy.

Acute endoplasmic reticulum stress-induced mitochondria respiratory chain damage: The role of activated calpains

The induction of acute endoplasmic reticulum (ER) stress damages the electron transport chain (ETC) in cardiac mitochondria. Activation of mitochondria-localized calpain 1 (CPN1) and calpain 2 (CPN2) impairs the ETC in pathological conditions, including aging and ischemia-reperfusion in settings where ER stress is increased. We asked if the activation of calpains causes the damage to the ETC during ER stress. Control littermate and CPNS1 (calpain small regulatory subunit 1) deletion mice were used in the current study. CPNS1 is an essential subunit required to maintain CPN1 and CPN2 activities, and deletion of CPNS1 prevents their activation. Tunicamycin (TUNI, 0.4 mg/kg) was used to induce ER stress in C57BL/6 mice. Cardiac mitochondria were isolated after 72 h of TUNI treatment. ER stress was increased in both control littermate and CPNS1 deletion mice with TUNI treatment. The TUNI treatment activated both cytosolic and mitochondrial CPN1 and 2 (CPN1/2) in control but not in CPNS1 deletion mice. TUNI treatment led to decreased oxidative phosphorylation and complex I activity in control but not in CPNS1 deletion mice compared to vehicle. The contents of complex I subunits, including NDUFV2 and ND5, were decreased in control but not in CPNS1 deletion mice. TUNI treatment also led to decreased oxidation through cytochrome oxidase (COX) only in control mice. Proteomic study showed that subunit 2 of COX was decreased in control but not in CPNS1 deletion mice. Our results provide a direct link between activation of CPN1/2 and complex I and COX damage during acute ER stress.

Targeting histone deacetylase-3 blocked epithelial-mesenchymal plasticity and metastatic dissemination in gastric cancer

BACKGROUND AND PURPOSE

Histone deacetylase (HDAC) inhibitors (HDIs) can modulate the epithelial-mesenchymal transition (EMT) progression and inhibit the migration and invasion of cancer cells. Emerging as a novel class of anti-cancer drugs, HDIs are attracted much attention in the field of drug discovery. This study aimed to discern the underlying mechanisms of Honokiol in preventing the metastatic dissemination of gastric cancer cells by inhibiting HDAC3 activity/expression.

EXPERIMENTAL APPROACH

Clinical pathological analysis was performed to determine the relationship between HDAC3 and tumor progression. The effects of Honokiol on pharmacological characterization, functional, transcriptional activities, organelle structure changes, and molecular signaling were analyzed using binding assays, differential scanning calorimetry, luciferase reporter assay, HDAC3 activity, ER stress response element activity, transmission electron microscopy, immune-blotting, and Wnt/β-catenin activity assays. The in vivo effects of Honokiol on peritoneal dissemination were determined by a mouse model and detected by PET/CT tomography.

KEY RESULTS

HDAC3 over-expression was correlated with poor prognosis. Honokiol significantly abolished HDAC3 activity (Y298) via inhibition of NFκBp65/CEBPβ signaling, which could be reversed by the over-expression of plasmids of NFκBp65/CEBPβ. Treatments with 4-phenylbutyric acid (a chemical chaperone) and calpain-2 gene silencing inhibited Honokiol-inhibited NFκBp65/CEBPβ activation. Honokiol increased ER stress markers and inhibited EMT-associated epithelial markers, but decreased Wnt/β-catenin activity. Suppression of HDAC3 by both Honokiol and HDAC3 gene silencing decreased cell migration and invasion in vitro and metastasis in vivo.

CONCLUSIONS AND IMPLICATIONS

Honokiol acts by suppressing HDAC3-mediated EMT and metastatic signaling. By prohibiting HDAC3, metastatic dissemination of gastric cancer may be blocked. Conceptual model showing the working hypothesis on the interaction among Honokiol, HDAC3, and ER stress in the peritoneal dissemination of gastric cancer. Honokiol targeting HDAC3 by ER stress cascade and mitigating the peritoneal spread of gastric cancer. Honokiol-induced ER stress-activated calpain activity targeted HDAC3 and blocked Tyr298 phosphorylation, subsequently blocked cooperating with EMT transcription factors and cancer progression. The present study provides evidence to demonstrate that HDAC3 is a positive regulator of EMT and metastatic growth of gastric cancer cells. The findings here imply that overexpressed HDAC3 is a potential therapeutic target for honokiol to reverse EMT and prevent gastric cancer migration, invasion, and metastatic dissemination. • Honokiol significantly abolished HDAC3 activity on catalytic tyrosine 298 residue site. In addition, Honokiol-induced ER stress markedly inhibited HDAC3 expression via inhibition of NFκBp65/CEBPβ signaling. • HDAC3, which is a positive regulator of metastatic gastric cancer cell growth, can be significantly inhibited by Honokiol. • Opportunities for HDAC3 inhibition may be a potential therapeutic target for preventing gastric cancer metastatic dissemination.

Role of Ubiquitination and Epigenetics in the Regulation of AhR Signaling in Carcinogenesis and Metastasis: "Albatross around the Neck" or "Blessing in Disguise"

The molecular mechanisms and signal transduction cascades evoked by the activation of aryl hydrocarbon receptor (AhR) are becoming increasingly understandable. AhR is a ligand-activated transcriptional factor that integrates environmental, dietary and metabolic cues for the pleiotropic regulation of a wide variety of mechanisms. AhR mediates transcriptional programming in a ligand-specific, context-specific and cell-type-specific manner. Pioneering cutting-edge research works have provided fascinating new insights into the mechanistic role of AhR-driven downstream signaling in a wide variety of cancers. AhR ligands derived from food, environmental contaminants and intestinal microbiota strategically activated AhR signaling and regulated multiple stages of cancer. Although AhR has classically been viewed and characterized as a ligand-regulated transcriptional factor, its role as a ubiquitin ligase is fascinating. Accordingly, recent evidence has paradigmatically shifted our understanding and urged researchers to drill down deep into these novel and clinically valuable facets of AhR biology. Our rapidly increasing realization related to AhR-mediated regulation of the ubiquitination and proteasomal degradation of different proteins has started to scratch the surface of intriguing mechanisms. Furthermore, AhR and epigenome dynamics have shown previously unprecedented complexity during multiple stages of cancer progression. AhR not only transcriptionally regulated epigenetic-associated molecules, but also worked with epigenetic-modifying enzymes during cancer progression. In this review, we have summarized the findings obtained not only from cell-culture studies, but also from animal models. Different clinical trials are currently being conducted using AhR inhibitors and PD-1 inhibitors (Pembrolizumab and nivolumab), which confirm the linchpin role of AhR-related mechanistic details in cancer progression. Therefore, further studies are required to develop a better comprehension of the many-sided and "diametrically opposed" roles of AhR in the regulation of carcinogenesis and metastatic spread of cancer cells to the secondary organs.

Omeprazole suppresses aggressive cancer growth and metastasis in mice through promoting Snail degradation

Omeprazole is a proton pump inhibitor that has recently been reported to exhibit anticancer activity against several types of cancer. However, the anticancer mechanisms of omeprazole remain elusive. Snail is an oncogenic zinc finger transcription factor; aberrant activation of Snail is associated with the occurrence and progression of cancer. In this study, we investigated whether Snail acted as a direct anticancer target of omeprazole. We showed that omeprazole displayed a high binding-affinity to recombinant Snail protein (K_d = 0.076 mM), suggesting that omeprazole directly and physically binds to the Snail protein. We further revealed that omeprazole disrupted CREB-binding protein (CBP)/p300-mediated Snail acetylation and then promoted Snail degradation through the ubiquitin-proteasome pathway in HCT116 cells. Omeprazole treatment markedly suppressed Snail-driven epithelial-mesenchymal transition (EMT) in aggressive HCT116, SUM159, and 4T1 cancer cells in vitro and reduced EMT-associated tumor invasion and metastasis in cancer cell xenograft models. Omeprazole also inhibited tumor growth by limiting Snail-dependent cell cycle progression. Overall, this study, for the first time, identifies Snail as a target of omeprazole and reveals a novel mechanism underlying the therapeutic effects of omeprazole against cancer. This study strongly suggests that omeprazole may be an excellent auxiliary drug for treating patients with malignant tumors.

Aggravation of pulmonary fibrosis after knocking down the Aryl hydrocarbon receptor in the Insulin-like growth factor 1 receptor pathway

BACKGROUND AND PURPOSE

Idiopathic pulmonary fibrosis (IPF) is a devastating disease with multiple contributing factors. Insulin-like growth factor 1 receptor (IGF1R), with a reciprocal function to Aryl hydrocarbon receptor (AhR), is known to be involved in the development of airway inflammation. However, the exact relationship between IGF1R and AhR in lung fibrogenesis is unclear. This study aimed to investigate the cascade pathway involving IGF1R and AhR in IPF.

EXPERIMENTAL APPROACH

The AhR and IGF1R expressions were determined in the lungs of IPF patients and in a rodent fibrosis model. Pulmonary fibrosis was evaluated in bleomycin (BLM)-induced lung injury in wild type and AhR knockout (AhR^-/- ) mice. The effects of IGF1R inhibition and AhR activation in vitro on TGF-β1-induced epithelial-mesenchymal transition (EMT) in Beas2B cells and in vivo on BLM-exposed mice were also examined.

KEY RESULTS

There were increased IGF1R levels but diminished AhR expression in the lung tissues of IPF patients and BLM-induced mice. Knockout of AhR aggravated lung fibrosis, while the use of IGF1R inhibitor and AhR agonist significantly attenuated such effects and inhibited TGF-β1-induced EMT in Beas2B cells. Both TGF-β1 and BLM markedly suppressed AhR expression through endoplasmic reticulum (ER) stress and consequently, IGF1R activation. The IGF1R inhibitor and specific knockdown of IGF1R reversed the activation of the TGF-β1 signal pathway.

CONCLUSION AND IMPLICATIONS

In the development of IPF, AhR and IGF1R play opposite roles via the TGF-β/Smad/STAT signaling cascade. The AhR/IGF1R axis is a potential target for the treatment of lung injury and fibrosis.

Aberrant Upregulation of Indoleamine 2,3-Dioxygenase 1 Promotes Proliferation and Metastasis of Hepatocellular Carcinoma Cells via Coordinated Activation of AhR and β-Catenin Signaling

Hepatocellular carcinoma (HCC) is the fourth most common cause of cancer-related death worldwide. Chronic liver inflammation due to hepatitis virus infection and other major effectors is a major risk factor of HCC. Indoleamine 2,3-dioxygenase 1 (IDO1), a heme enzyme highly expressed upon stimulation with proinflammatory cytokines such as interferon-γ (IFN-γ), is activated to modulate the tumor microenvironment and potentially crucial in the development of certain cancer types. Earlier studies have majorly reported an immunomodulatory function of IDO1. However, the specific role of IDO1 in cancer cells, particularly HCC, remains to be clarified. Analysis of The Cancer Genome Atlas Liver Hepatocellular Carcinoma (TCGA LIHC) dataset in the current study revealed a significant correlation between IDO1 expression and HCC. We further established inducible IDO1-expressing cell models by coupling lentivirus-mediated knockdown and IFN-γ induction of IDO1 in normal and HCC cells. In functional assays, proliferation and motility-related functions of HCC cells were compromised upon suppression of IDO1, which may partially be rescued by its enzymatic product, kynurenine (KYN), while normal hepatocytes were not affected. Aryl hydrocarbon receptor (AhR), a reported endogenous KYN receptor, is suggested to participate in tumorigenesis. In mechanistic studies, IDO1 activation promoted both AhR and β-catenin activity and nuclear translocation. Immunofluorescence staining and co-immunoprecipitation assays further disclosed interactions between AhR and β-catenin. In addition, we identified a Src-PTEN-PI3K/Akt-GSK-3β axis involved in β-catenin stabilization and activation following IDO1-mediated AhR activation. IDO1-induced AhR and β-catenin modulated the expression of proliferation- and EMT-related genes to facilitate growth and metastasis of HCC cells. Our collective findings provide a mechanistic basis for the design of more efficacious IDO1-targeted therapy for HCC.

New Understanding of the Relevant Role of LINE-1 Retrotransposition in Human Disease and Immune Modulation

Long interspersed nuclear element-1 (LINE-1) retrotransposition is a major hallmark of cancer accompanied by global chromosomal instability, genomic instability, and genetic heterogeneity and has become one indicator for the occurrence, development, and poor prognosis of many diseases. LINE-1 also modulates the immune system and affects the immune microenvironment in a variety of ways. Aberrant expression of LINE-1 retrotransposon can provide strong stimuli for an innate immune response, activate the immune system, and induce autoimmunity and inflammation. Therefore, inhibition the activity of LINE-1 has become a potential treatment strategy for various diseases. In this review, we discussed the components and regulatory mechanisms involved with LINE-1, its correlations with disease and immunity, and multiple inhibitors of LINE-1, providing a new understanding of LINE-1.

Prognostic Role of Aryl Hydrocarbon Receptor Interacting Protein (AIP) Immunohistochemical Expression in Patients with Resected Gastric Carcinomas

Aryl hydrocarbon receptor (AHR) interacting protein (AIP) is a chaperone which binds to inactive AHR in the cell cytoplasm. AHR is best known for mediating the toxicity of halogenated aromatics, but it has also been linked to carcinogenesis and tumor progression in several tumor types. Our aims are to assess the features of AIP immunohistochemical (IHC) staining and to evaluate its possible role as a prognostic marker in gastric cancer (GC). Retrospective study of 147 cases of resected GC. Clinicopathological features were collected, tissue microarrays were constructed for AIP IHC and statistical analysis were performed. AIP staining was observed in 50.3% of tumors. All AIP-positive cases exhibited cytoplasmic or membranous staining, variably associated with nuclear co-staining. 93.2% of AIP-positive tumors showed AIP immunoreactivity in 100% of cells. Staining intensity was mild, moderate and intense in 33.8%, 13.5% and 52.7% of cases. Tumors were stratified according to AIP staining intensity into low expression (no or mild AIP immunoreactivity) and high expression (moderate or intense AIP immunoreactivity). 36.6% of our cases showed high AIP expression. High AIP expression was significantly and independently correlated to tumor progression and cancer death. Tumors with high AIP expression showed lower survival and higher progression rates. AIP expression might be useful for determining GC prognosis. More studies are needed to clarify the role of AHR pathway in GC, AIP expression and its potential use as a surrogate marker for selecting patients for AHR modulation therapy.

Snail1: A Transcriptional Factor Controlled at Multiple Levels

Snail1 transcriptional factor plays a key role in the control of epithelial to mesenchymal transition and fibroblast activation. As a consequence, Snail1 expression and function is regulated at multiple levels from gene transcription to protein modifications, affecting its interaction with specific cofactors. In this review, we describe the different elements that control Snail1 expression and its activity both as transcriptional repressor or activator.

Endoplasmic reticulum proteostasis control and gastric cancer

The endoplasmic reticulum (ER) is the primary organelle responsible for the synthesis, modification, folding and secretion of proteins, especially in specialized secretory cells. It also contributes to the maintenance of cellular functions, such as Ca²⁺ storage, lipogenesis, gluconeogenesis, and organelle biogenesis. Cellular stress conditions, such as glucose deprivation, hypoxia and disturbance of Ca²⁺ homeostasis, may increase the risk of protein misfolding and perturb proteostasis. This activates ER stress and triggers the unfolded protein response (UPR), leading to either the restoration of homeostasis or cell death. ER stress and UPR have been shown to play crucial roles in the pathogenesis, progression and treatment response of various cancers. In gastric cancer (GC), one of the most aggressive cancer types, critical functions of ER stress signaling have also started to emerge. Herein, we summarize the current knowledge linking ER stress and UPR to GC; we also discuss the possible nodes of therapeutic intervention and propose directions of future research.

Inflammatory breast cancer: Activation of the aryl hydrocarbon receptor and its target CYP1B1 correlates closely with Wnt5a/b-β-catenin signalling, the stem cell phenotype and disease progression

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AHR is over-expressed and hyperactivated in carcinoma tissues of IBC patients.

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AHR knockdown inhibits expression of CYP1B1 and Wnt5a in IBC cells.

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AHR and CYP1B1 expression correlates with Wnt5 a/b and b-catenin expression levels.

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AHR and CYP1B1 expression correlates with percentage of CD44⁽⁺⁾/CD24^(−/low) subset in IBC.

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AHR and its surrogate molecules correlate with IBC poor prognosis.

The aim of the present study was to evaluate the expression levels of the aryl hydrocarbon receptor (AHR) and its target gene CYP1B1 and to correlate their expression with Wnt5a/b-β-catenin, the CD44⁺/CD24^(−/low) cancer stem cell (CSC) subset and factors associated with poor prognosis in inflammatory breast cancer (IBC) and non-IBC patients. The methods of analysis used were quantitative real-time PCR, western blotting, immunohistochemistry and flow cytometry. Compared to non-IBC tissues, IBC tissues exhibited the overexpression of AHR and its target gene/protein CYP1B1. AHR and CYP1B1 mRNA levels were associated with the poor clinical prognosis markers tumour grade, lymphovascular invasion, cell proliferation and lymph node metastasis. Furthermore, AHR expression correlated with the expression of Wnt5a/b and β-catenin signalling molecules, and Wnt5a mRNA expression was downregulated in the SUM149 human IBC cell line and the MDA-MB-231 non-IBC cell line upon inhibition of AHR. AHR gene knockout (CRISPR-Cas9) inhibits CYP1B1 and Wnt5a expression in the IBC cell line. The CD44⁺/CD24^(−/low) subset was significantly correlated with the expression of AHR, CYP1B1, Wnt5a/b and β-catenin in IBC tissues. The overexpression of AHR and its target CYP1B1 correlated with the expression of Wnt5a/b and β-catenin, CSCs, and poor clinical prognostic factors of IBC. Thus, targeting AHR and/or its downstream target molecules CYP1B1 and Wnt5a/b may represent a therapeutic approach for IBC.

Bioinformatics analysis to identify action targets in NCI-N87 gastric cancer cells exposed to quercetin

CONTEXT

Quercetin exerts antiproliferative effects on gastric cancer. However, its mechanisms of action on gastric cancer have not been comprehensively revealed.

OBJECTIVE

We investigated the mechanisms of action of quercetin against gastric cancer cells.

MATERIALS AND METHODS

Human NCI-N87 gastric cancer cells were treated with 15 μM quercetin or dimethyl sulfoxide (as a control) for 48 h. DNA isolated from cells was sequenced on a HiSeq 2500, and the data were used to identify differentially expressed genes (DEGs) between groups. Then, enrichment analyses were performed for DEGs and a protein-protein interaction (PPI) network was constructed. Finally, the transcription factors (TFs)-DEGs regulatory network was visualized by Cytoscape software.

RESULTS

A total of 121 DEGs were identified in the quercetin group. In the PPI network, Fos proto-oncogene (FOS, degree = 12), aryl hydrocarbon receptor (AHR, degree = 12), Jun proto-oncogene (JUN, degree = 11), and cytochrome P450 family 1 subfamily A member 1 (CYP1A1, degree = 11) with higher degrees highly interconnected with other proteins. Of the 5 TF-DEGs, early growth response 1 (EGR1), FOS like 1 (FOSL1), FOS, and JUN were upregulated, while AHR was downregulated. Moreover, FOSL1, JUN, and Wnt family member 7B (WNT7B) were enriched in the Wnt signaling pathway.

DISCUSSION AND CONCLUSIONS

CYP1A1 highly interconnected with AHR in the PPI network. Therefore, FOS, AHR, JUN, CYP1A1, EGR1, FOSL1, and WNT7B might be targets of quercetin in gastric cancer.

Dietary phytochemicals in the regulation of epithelial to mesenchymal transition and associated enzymes: A promising anticancer therapeutic approach

Epithelial to mesenchymal transition (EMT) is a biological phenomenon that plays a primordial role for initiation of metastasis. It renders cancer cells with increased self-renewal and tumor-initiating capabilities and exacerbated resistance to apoptosis and chemotherapy. Hence, regulation of EMT stands out to be an important strategy in controlling the behavior of malignant cells. Despite the enormous amount of preclinical data on the implication of EMT in cancer progression, there is still lack of routine clinical translation at therapeutic levels. The need of EMT-modulating drugs with high efficacy and low cytotoxicity has led to studies involving the evaluation of the efficacy of a plethora of various classes of phytochemicals present in dietary sources of fruits and vegetables. This review summarizes the role of these different classes of phytochemicals, their natural/synthetic analogs, and their nano-formulations in regulation of EMT in various preclinical models through attenuation of primary signaling pathways. Numerous proteins, transcription factors and enzymes targeted by various classes of phytochemicals in repression of EMT has been presented in this review. Additionally, we have critically analyzed the existing literature and provided views on new direction for accelerating the discovery of novel drug candidates which could be cautiously administered without concomitant effects.

[Aryl-hydrocarbon receptor as a potential target for anticancer therapy]

Aryl-hydrocarbon receptor (Aryl Hydrocarbon Receptor, AHR) is a ligand-dependent transcription factor, whose functions are related to xenobiotic detoxification, response to inflammation, and maintenance of tissue homeostasis. Recent investigations suggest that AHR also plays an important role in the processes of carcinogenesis. Increased expression of AHR is observed in several types of tumors and tumor cell lines. In addition, it turned out that the composition of pharmaceutical drugs used in oncotherapy includes some ligands AHR. These facts allow us to consider an aryl-hydrocarbon receptor as a potential target for anticancer therapy, especially for the treatment of severe cancers whose treatment options are very limited or do not exist at all. In this review the examples of AHR ligands' effect on tumor cell cultures and on model mice lines with AHR-dependent response are discussed.

Evidence for calpains in cancer metastasis

Metastatic dissemination represents the final stage of tumor progression as well as the principal cause of cancer-associated deaths. Calpains are a conserved family of calcium-dependent cysteine proteinases with ubiquitous or tissue-specific expression. Accumulating evidence indicates a central role for calpains in tumor migration and invasion via participating in several key processes, including focal adhesion dynamics, cytoskeletal remodeling, epithelial-to-mesenchymal transition, and apoptosis. Activated after the increased intracellular calcium concentration ( [ Ca 2 + ] i ) induced by membrane channels and extracellular or intracellular stimuli, calpains induce the limited cleavage or functional modulation of various substrates that serve as metastatic mediators. This review covers established literature to summarize the mechanisms and underlying signaling pathways of calpains in cancer metastasis, making calpains attractive targets for aggressive tumor therapies.

Involvement of Aryl Hydrocarbon Receptor and Aryl Hydrocarbon Receptor Repressor in Helicobacter Pylori-related Gastric Pathogenesis

Background: Persistent Helicobacter pylori (H. pylori) infection leads to various gastric diseases. Multiple studies have demonstrated that aryl hydrocarbon receptor (AHR) plays roles in the antibacterial response and aryl hydrocarbon receptor repressor (AHRR) is downregulated in stomach cancer. However, the role of AHR or AHRR in H. pylori-related gastric diseases remains unclear. Aims: To investigate whether AHR or AHRR is involved in H. pylori-related gastric diseases. Methods: Patients with gastritis or gastric adenocarcinoma were enrolled randomly, and gastric tissue specimens were diagnosed pathologically. AHR, AHRR, and H. pylori infection status in tissues were detected by immunohistochemistry. Human gastric cells were cocultured with H. pylori. siRNAs were used to silence AHR or AHRR, and a C57bl/6 mouse model colonized by H. pylori was established. Protein expression was determined by western blotting analysis, and TNF, IL-8 and IL-1β in cell supernatants were measured by ELISA. Results: AHR and AHRR were expressed in gastritis tissues and gastric cancer tissues without H. pylori infection, and principally located in the cytoplasm and nucleus. AHR expression was significantly correlated with AHRR expression in gastric tissues without H. pylori infection (P=0.008). However, their expressions were negatively correlated with H. pylori infection status. H. pylori coculture inhibited AHR and AHRR expression in stomach mucosa in vitro and in vivo. Gastric cells produced more TNF, IL-8 and IL-1β when AHR or AHRR was silenced. Conclusions: This preliminary study indicates that AHR and AHRR may be involved in H. pylori-related gastric pathogenesis, and helps toward understanding of inflammation-initiated carcinogenesis of gastric cancer.

Adaptive changes in global gene expression profile of lung carcinoma A549 cells acutely exposed to distinct types of AhR ligands

Exposure to persistent ligands of aryl hydrocarbon receptor (AhR) has been found to cause lung cancer in experimental animals, and lung adenocarcinomas are often associated with enhanced AhR expression and aberrant AhR activation. In order to better understand the action of toxic AhR ligands in lung epithelial cells, we performed global gene expression profiling and analyze TCDD-induced changes in A549 transcriptome, both sensitive and non-sensitive to CH223191 co-treatment. Comparison of our data with results from previously reported microarray and ChIP-seq experiments enabled us to identify candidate genes, which expression status reflects exposure of lung cancer cells to TCDD, and to predict processes, pathways (e.g. ER stress, Wnt/β-cat, IFNɣ, EGFR/Erbb1), putative TFs (e.g. STAT, AP1, E2F1, TCF4), which may be implicated in adaptive response of lung cells to TCDD-induced AhR activation. Importantly, TCDD-like expression fingerprint of selected genes was observed also in A549 cells exposed acutely to both toxic (benzo[a]pyrene, benzo[k]fluoranthene) and endogenous AhR ligands (2-(1H-Indol-3-ylcarbonyl)-4-thiazolecarboxylic acid methyl ester and 6-formylindolo[3,2-b]carbazole). Overall, our results suggest novel cellular candidates, which could help to improve monitoring of AhR-dependent transcriptional activity during acute exposure of lung cells to distinct types of environmental pollutants.

The aryl hydrocarbon receptor in the crossroad of signalling networks with therapeutic value

The aryl hydrocarbon receptor (AhR) is well-known for its major contributions to the cellular responses against environmental toxins and carcinogens. Notably, AhR has also emerged as a key transcription factor controlling many physiological processes including cell proliferation and apoptosis, differentiation, adhesion and migration, pluripotency and stemness. These novel functions have broadened our understanding of the signalling pathways and molecular intermediates interacting with AhR under both homeostatic and pathological conditions. Recent discoveries link AhR with the function of essential organs such as liver, skin and gonads, and with complex organismal structures including the immune and cardiovascular systems. The identification of potential endogenous ligands able to regulate AhR activity, opens the possibility of designing ad hoc molecules with pharmacological and/or therapeutic value to treat human diseases in which AhR may have a causal role. Integration of experimental data from in vitro and in vivo studies with "omic" analyses of human patients affected with cancer, immune diseases, inflammation or neurological disorders will likely contribute to validate the clinical relevance of AhR and the possible benefits of modulating its activity by pharmacologically-driven strategies. In this review, we will highlight signalling pathways involved in human diseases that could be targetable by AhR modulators and discuss the feasibility of using such molecules in therapy. The pros and cons of AhR-aimed approaches will be also mentioned.

TPL2 (Therapeutic Targeting Tumor Progression Locus-2)/ATF4 (Activating Transcription Factor-4)/SDF1α (Chemokine Stromal Cell-Derived Factor-α) Axis Suppresses Diabetic Retinopathy

RATIONALE

Diabetic retinopathy is characterized by vasopermeability, vascular leakage, inflammation, blood-retinal barrier breakdown, capillary degeneration, and neovascularization. However, the mechanisms underlying the association between diabetes mellitus and progression retinopathy remain unclear.

OBJECTIVE

TPL2 (tumor progression locus 2), a serine-threonine protein kinase, exerts a pathological effect on vascular angiogenesis. This study investigated the role of N^ε-(carboxymethyl)lysine, a major advanced glycation end products, and the involved TPL2-related molecular signals in diabetic retinopathy using models of in vitro and in vivo and human samples.

METHODS AND RESULTS

Serum N^ε-(carboxymethyl)lysine levels and TPL2 kinase activity were significantly increased in clinical patients and experimental animals with diabetic retinopathy. Intravitreal administration of pharmacological blocker or neutralizing antibody inhibited TPL2 and effectively suppressed the pathological characteristics of retinopathy in streptozotocin-induced diabetic animal models. Intravitreal VEGF (vascular endothelial growth factor) neutralization also suppressed the diabetic retinopathy in diabetic animal models. Mechanistic studies in primary human umbilical vein endothelial cells and primary retinal microvascular endothelial cells from streptozotocin-diabetic rats, db/db mice, and samples from patients with diabetic retinopathy revealed a positive parallel correlation between N^ε-(carboxymethyl)lysine and the TPL2/chemokine SDF1α (stromal cell-derived factor-α) axis that is dependent on endoplasmic reticulum stress-related molecules, especially ATF4 (activating transcription factor-4).

CONCLUSIONS

This study demonstrates that inhibiting the N^ε-(carboxymethyl)lysine-induced TPL2/ATF4/SDF1α axis can effectively prevent diabetes mellitus-mediated retinal microvascular dysfunction. This signaling axis may include the therapeutic potential for other diseases involving pathological neovascularization or macular edema.

Role of the aryl hydrocarbon receptor in carcinogenesis and potential as an anti-cancer drug target

The aryl hydrocarbon receptor (AhR) was initially identified as the receptor that binds and mediates the toxic effects induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and structurally related halogenated aromatics. Other toxic compounds including some polynuclear aromatic hydrocarbons act through the AhR; however, during the last 25 years, it has become apparent that the AhR plays an essential role in maintaining cellular homeostasis. Moreover, the scope of ligands that bind the AhR includes endogenous compounds such as multiple tryptophan metabolites, other endogenous biochemicals, pharmaceuticals and health-promoting phytochemicals including flavonoids, indole-3-carbinol and its metabolites. It has also been shown that like other receptors, the AhR is a drug target for multiple diseases including cancer, where both AhR agonists and antagonists effectively block many of the critical hallmarks of cancer in multiple tumor types. This review describes the anti-cancer activities of AhR ligands and demonstrates that it is time to separate the AhR from TCDD and exploit the potential of the AhR as a novel target for cancer chemotherapy.

The aryl hydrocarbon receptor repressor - More than a simple feedback inhibitor of AhR signaling: Clues for its role in inflammation and cancer

The aryl hydrocarbon receptor repressor (AhRR) was first described as a specific competitive repressor of aryl hydrocarbon receptor (AhR) activity based on its ability to dimerize with the AhR nuclear translocator (ARNT) and through direct competition of AhR/ARNT and AhRR/ARNT complexes for binding to dioxin-responsive elements (DREs). Like AhR, AhRR belongs to the basic Helix-Loop-Helix/Per-ARNT-Sim (bHLH/PAS) protein family but lacks functional ligand-binding and transactivation domains. Transient transfection experiments with ARNT and AhRR mutants examining the inhibitory mechanism of AhRR suggested a more complex mechanism than the simple mechanism of negative feedback through sequestration of ARNT to regulate AhR signaling. Recently, AhRR has been shown to act as a tumor suppressor gene in several types of cancer cells. Furthermore, epidemiological studies have found epigenetic changes and silencing of AhRR associated with exposure to cigarette smoke and cancer development. Additional studies from our laboratories have demonstrated that AhRR represses other signaling pathways including NF-κB and is capable of regulating inflammatory responses. A better understanding of the regulatory mechanisms of AhRR in AhR signaling and adverse outcome pathways leading to deregulated inflammatory responses contributing to tumor promotion and other adverse health effects is expected from future studies. This review article summarizes the characteristics of AhRR as an inhibitor of AhR activity and highlights more recent findings pointing out the role of AhRR in inflammation and tumorigenesis.

Benzo[a]pyrene promotes gastric cancer cell proliferation and metastasis likely through the Aryl hydrocarbon receptor and ERK-dependent induction of MMP9 and c-myc

Gastric cancer (GC) is the fifth most common cancer worldwide and the third leading cause of global cancer-related death. Benzo[a]pyrene (BaP), a Group Ⅰ carcinogen categorized by the IARC, is a cumulative foodborne carcinogen and ubiquitous environmental pollutant with potent carcinogenic properties. However, the function and mechanism of BaP exposure on GC progression remains unclear. We investigated the role of BaP in human GC progression to identify potential mechanism underlining its carcinogenic activity. After exposure to various concentrations of BaP, human GC cells SGC-7901 and MNK-45 showed an increased capability of proliferation, migration and invasion. Further study indicated that BaP promotes the expression of matrix metalloproteinase-9 (MMP9) and c-myc at mRNA and protein level, and activates Aryl hydrocarbon receptor (AhR) and ERK pathway. Moreover, BaP-induced overexpression of MMP9 and c-myc were attenuated by the ERK inhibitor U0126 and AhR inhibitor resveratrol, respectively. These data suggest that BaP promotes proliferation and metastasis of GC cells through upregulation of MMP9 and c-myc expression, and this was likely mediated via the AhR and ERK signaling pathway.

Analysis of different components in the peritumoral tissue microenvironment of colorectal cancer: A potential prospect in tumorigenesis

The present study aimed to observe the varying expression of biomarkers in the microenvironment adjacent to colorectal cancer lesions to provide additional insight into the functions of microenvironment components in carcinogenesis and present a novel or improved indicator for early diagnosis of cancer. A total of 144 human samples from three different locations in 48 patients were collected, these locations were 10, 5 and 2 cm from the colorectal cancer lesion, respectively. The biomarkers analyzed included E‑cadherin, cytokeratin 18 (CK18), hyaluronidase‑1 (Hyal‑1), collagen type I (Col‑I), Crumbs3 (CRB3), vimentin, proteinase activated receptor 3 (PAR‑3), α‑smooth muscle actin (α‑SMA), cyclin D1 (CD1) and cluster of differentiation (CD)133. In addition, crypt architecture was observed. Related functional analysis of proteins was performed using hierarchical index cluster analysis. More severe destroyed crypt architecture closer to the cancer lesions was observed compared with the 10 cm sites, with certain crypts degraded entirely. Expression levels of E‑cadherin, CK18, CRB3 and PAR‑3 were lower in 2 cm sites compared with the 10 cm sites (all P<0.001), while the expression levels of the other biomarkers in the 2 cm sites were increased compared with 10 cm sites (all P<0.0001). Notably, the expression of CK18 in 2 cm sites was higher than in the 5 cm site (P<0.0001), which was different from the expression of E‑cadherin, CRB3 and PAR‑3. The expression levels of Hyal‑1 and Col‑I at the 2 cm sites were lower than that of the 5 cm sites (P>0.05 and P=0.0001, respectively), while the expression of vimentin, α‑SMA, CD1 and CD133 were not. Hyal‑1 and Col‑I may be independently important in cancer initiation in the tumor microenvironment. The results of the present study suggest that the biomarkers in the tissue microenvironment are associated with early tumorigenesis and may contribute to the development of carcinomas. These observations may be useful for early diagnosis of colorectal cancer.

Melatonin set out to ER stress signaling thwarts epithelial mesenchymal transition and peritoneal dissemination via calpain-mediated C/EBPβ and NFκB cleavage

Peritoneal dissemination of tumor has high mortality and is associated with the loss of epithelial features, acquisition of motile mesenchymal morphology characteristics, and invasive properties by tumor cells. Melatonin is an endogenously produced molecule in all plant species that is known to exert antitumor activity, but to date, its underlying mechanisms and antiperitoneal metastasis efficacy is not well defined. This study determined the antiperitoneal dissemination potential of melatonin in vivo and assessed its association with the inhibition of epithelial-to-mesenchymal transition (EMT) signaling mechanism by endoplasmic reticulum (ER) stress, which may be a major molecular mechanism of melatonin against cancer. The results demonstrate that melatonin inhibited peritoneal metastasis in vivo and activated ER stress in Cignal ERSE Reporter Assay, organelle structure in transmission electron microscopy images, calpain activity, and protein biomarkers like p-elf2α. Moreover, the overexpression of transcription factor C/EBPβ in gastric cancer interacted with NFκB and further regulates COX-2 expression. These were dissociated and downregulated by melatonin, as proven by immunofluorescence imaging, immunoprecipitation, EMSA, and ChIP assay. Melatonin or gene silencing of C/EBPβ decreased the EMT protein markers (E-cadherin, Snail, and Slug) and Wnt/beta-catenin activity by Topflash activity, and increased ER stress markers. In an animal study, the results of melatonin therapy were consistent with those of in vitro findings and attenuated systemic proangiogenesis factor production. In conclusion, C/EBPβ and NFκB inhibition by melatonin may impede both gastric tumor growth and peritoneal dissemination by inducing ER stress and inhibiting EMT.

Differential network analysis reveals dysfunctional regulatory networks in gastric carcinogenesis

Gastric Carcinoma is one of the most common cancers in the world. A large number of differentially expressed genes have been identified as being associated with gastric cancer progression, however, little is known about the underlying regulatory mechanisms. To address this problem, we developed a differential networking approach that is characterized by including a nascent methodology, differential coexpression analysis (DCEA), and two novel quantitative methods for differential regulation analysis. We first applied DCEA to a gene expression dataset of gastric normal mucosa, adenoma and carcinoma samples to identify gene interconnection changes during cancer progression, based on which we inferred normal, adenoma, and carcinoma-specific gene regulation networks by using linear regression model. It was observed that cancer genes and drug targets were enriched in each network. To investigate the dynamic changes of gene regulation during carcinogenesis, we then designed two quantitative methods to prioritize differentially regulated genes (DRGs) and gene pairs or links (DRLs) between adjacent stages. It was found that known cancer genes and drug targets are significantly higher ranked. The top 4% normal vs. adenoma DRGs (36 genes) and top 6% adenoma vs. carcinoma DRGs (56 genes) proved to be worthy of further investigation to explore their association with gastric cancer. Out of the 16 DRGs involved in two top-10 DRG lists of normal vs. adenoma and adenoma vs. carcinoma comparisons, 15 have been reported to be gastric cancer or cancer related. Based on our inferred differential networking information and known signaling pathways, we generated testable hypotheses on the roles of GATA6, ESRRG and their signaling pathways in gastric carcinogenesis. Compared with established approaches which build genome-scale GRNs, or sub-networks around differentially expressed genes, the present one proved to be better at enriching cancer genes and drug targets, and prioritizing disease-related genes on the dataset we considered. We propose this extendable differential networking framework as a promising way to gain insights into gene regulatory mechanisms underlying cancer progression and other phenotypic changes.