Arsenite evokes IL-6 secretion, autocrine regulation of STAT3 signaling, and miR-21 expression, processes involved in the EMT and malignant transformation of human bronchial epithelial cells

Quinazoline sulfonamide derivatives targeting MicroRNA-34a/MDM4/p53 apoptotic axis with radiosensitizing activity

Aim: New quinazoline benzenesulfonamide hybrids 4a-n were synthesized to determine their cytotoxicity and effect on the miR-34a/MDM4/p53 apoptotic pathway. Materials & methods: Cytotoxicity against hepatic, breast, lung and colon cancer cell lines was estimated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Results: Compound 4d was the most potent against HepG2 and MCF-7 cancer cells, with potential apoptotic activity verified by a significant upregulation of miR-34a and p53 gene expressions. The apoptotic effect of 4d was further investigated and showed downregulation of miR-21, VEGF, STAT3 and MDM4 gene expression. Conclusion: The anticancer and apoptotic activities of 4d were enhanced post irradiation by a single dose of 8 Gy γ-radiation. Docking analysis demonstrated a valuable affinity of 4d toward VEGFR2 and MDM4 active sites.

Arsenic toxicity: sources, pathophysiology and mechanism

Background

Arsenic is a naturally occurring element that poses a significant threat to human health due to its widespread presence in the environment, affecting millions worldwide. Sources of arsenic exposure are diverse, stemming from mining activities, manufacturing processes, and natural geological formations. Arsenic manifests in both organic and inorganic forms, with trivalent meta-arsenite (As3+) and pentavalent arsenate (As5+) being the most common inorganic forms. The trivalent state, in particular, holds toxicological significance due to its potent interactions with sulfur-containing proteins.

Objective

The primary objective of this review is to consolidate current knowledge on arsenic toxicity, addressing its sources, chemical forms, and the diverse pathways through which it affects human health. It also focuses on the impact of arsenic toxicity on various organs and systems, as well as potential molecular and cellular mechanisms involved in arsenic-induced pathogenesis.

Methods

A systematic literature review was conducted, encompassing studies from diverse fields such as environmental science, toxicology, and epidemiology. Key databases like PubMed, Scopus, Google Scholar, and Science Direct were searched using predetermined criteria to select relevant articles, with a focus on recent research and comprehensive reviews to unravel the toxicological manifestations of arsenic, employing various animal models to discern the underlying mechanisms of arsenic toxicity.

Results

The review outlines the multifaceted aspects of arsenic toxicity, including its association with chronic diseases such as cancer, cardiovascular disorders, and neurotoxicity. The emphasis is placed on elucidating the role of oxidative stress, genotoxicity, and epigenetic modifications in arsenic-induced cellular damage. Additionally, the impact of arsenic on vulnerable populations and potential interventions are discussed.

Conclusions

Arsenic toxicity represents a complex and pervasive public health issue with far-reaching implications. Understanding the diverse pathways through which arsenic exerts its toxic effects is crucial to developing effective mitigation strategies and interventions. Further research is needed to fill gaps in our understanding of arsenic toxicity and to inform public health policies aimed at minimising exposure.Arsenic toxicity is a crucial public health problem influencing millions of people around the world. The possible sources of arsenic toxicity includes mining, manufacturing processes and natural geological sources. Arsenic exists in organic as well as in inorganic forms. Trivalent meta-arsenite (As3+) and pentavalent arsenate (As5+) are two most common inorganic forms of arsenic. Trivalent oxidation state is toxicologically more potent due to its potential to interact with sulfur containing proteins. Humans are exposed to arsenic in many ways such as environment and consumption of arsenic containing foods. Drinking of arsenic-contaminated groundwater is an unavoidable source of poisoning, especially in India, Bangladesh, China, and some Central and South American countries. Plenty of research has been carried out on toxicological manifestation of arsenic in different animal models to identify the actual mechanism of aresenic toxicity. Therefore, we have made an effort to summarize the toxicology of arsenic, its pathophysiological impacts on various organs and its molecular mechanism of action.

The Role of microRNAs in Arsenic-Induced Human Diseases: A Review

MicroRNAs (miRNAs) are noncoding RNAs with 20-22 nucleotides, which are encoded by endogenous genes and are capable of targeting the majority of human mRNAs. Arsenic is regarded as a human carcinogen, which can lead to many adverse health effects including diabetes, skin lesions, kidney disease, neurological impairment, male reproductive injury, and cardiovascular disease (CVD) such as cardiac arrhythmias, ischemic heart failure, and endothelial dysfunction. miRNAs can act as tumor suppressors and oncogenes via directly targeting oncogenes or tumor suppressors. Recently, miRNA dysregulation was considered to be an important mechanism of arsenic-induced human diseases and a potential biomarker to predict the diseases caused by arsenic exposure. Endogenic miRNAs such as miR-21, the miR-200 family, miR-155, and the let-7 family are involved in arsenic-induced human disease by inducing translational repression or RNA degradation and influencing multiple pathways, including mTOR/Arg 1, HIF-1α/VEGF, AKT, c-Myc, MAPK, Wnt, and PI3K pathways. Additionally, exogenous miRNAs derived from plants, such as miR-34a, miR-159, miR-2911, miR-159a, miR-156c, miR-168, etc., among others, can be transported from blood to specific tissue/organ systems in vivo. These exogenous miRNAs might be critical players in the treatment of human diseases by regulating host gene expression. This review summarizes the regulatory mechanisms of miRNAs in arsenic-induced human diseases, including cancers, CVD, and other human diseases. These special miRNAs could serve as potential biomarkers in the management and treatment of human diseases linked to arsenic exposure. Finally, the protective action of exogenous miRNAs, including antitumor, anti-inflammatory, anti-CVD, antioxidant stress, and antivirus are described.

Arsenic and Diabetes Mellitus: A Putative Role for the Immune System

Diabetes mellitus (DM) is an enormous public health issue worldwide. Recent data suggest that chronic arsenic exposure is linked to the risk of developing type 1 and type 2 DM, albeit the underlying mechanisms are unclear. This review discusses the role of the immune system as a link to possibly explain some of the mechanisms of developing T1DM or T2DM associated with arsenic exposure in humans, animal models, and in vitro studies. The rationale for the hypothesis includes: (1) Arsenic is a well-recognized modulator of the immune system; (2) arsenic exposures are associated with increased risk of DM; and (3) dysregulation of the immune system is one of the hallmarks in the pathogenesis of both T1DM and T2DM. A better understanding of DM in association with immune dysregulation and arsenic exposures may help to understand how environmental exposures modulate the immune system and how these effects may impact the manifestation of disease.

miRNAs and arsenic-induced carcinogenesis

Arsenic-induced carcinogenesis is a worldwide health problem. Identifying the molecular mechanisms responsible for the induction of arsenic-induced cancers is important for developing treatment strategies. MicroRNA (miRNA) dysregulation is known to affect development and progression of human cancer. Several studies have identified an association between altered miRNA expression in cancers from individuals chronically exposed to arsenic and in cell models for arsenic-induced carcinogenesis. This chapter provides a comprehensive review for miRNA dysregulation in arsenic-induced cancer.

MicroRNA-Gene Interactions Impacted by Toxic Metal(oid)s during EMT and Carcinogenesis

Chronic environmental exposure to toxic metal(loid)s significantly contributes to human cancer development and progression. It is estimated that approximately 90% of cancer deaths are a result of metastasis of malignant cells, which is initiated by epithelial-mesenchymal transition (EMT) during early carcinogenesis. EMT is regulated by many families of genes and microRNAs (miRNAs) that control signaling pathways for cell survival, death, and/or differentiation. Recent mechanistic studies have shown that toxic metal(loid)s alter the expression of miRNAs responsible for regulating the expression of genes involved in EMT. Altered miRNA expressions have the potential to be biomarkers for predicting survival and responses to treatment in cancers. Significantly, miRNAs can be developed as therapeutic targets for cancer patients in the clinic. In this mini review, we summarize key findings from recent studies that highlight chemical-miRNA-gene interactions leading to the perturbation of EMT after exposure to toxic metal(loid)s including arsenic, cadmium, nickel, and chromium.

Epigenomic reprogramming in iAs-mediated carcinogenesis

Arsenic is a naturally occurring metal carcinogen found in the Earth's crust. Millions of people worldwide are chronically exposed to arsenic through drinking water and food. Exposure to inorganic arsenic has been implicated in many diseases ranging from acute toxicities to malignant transformations. Despite the well-known deleterious health effects of arsenic exposure, the molecular mechanisms in arsenic-mediated carcinogenesis are not fully understood. Since arsenic is non-mutagenic, the mechanism by which arsenic causes carcinogenesis is via alterations in epigenetic-regulated gene expression. There are two possible ways by which arsenic may modify the epigenome-indirectly through an arsenic-induced generation of reactive oxygen species which then impacts chromatin remodelers, or directly through interaction and modulation of chromatin remodelers. Whether directly or indirectly, arsenic modulates epigenetic gene regulation and our understanding of the direct effect of this modulation on chromatin structure is limited. In this chapter we will discuss the various ways by which inorganic arsenic affects the epigenome with consequences in health and disease.

JAK2/STAT3 in role of arsenic-induced cell proliferation: a systematic review and meta-analysis

OBJECTIVES

Malignant cell proliferation is one of the important mechanisms of arsenic poisoning. A large number of studies have shown that STAT3 plays an important role in cell malignant proliferation, but there are still many contradictions in the effect of arsenic on JAK2/STAT3. This study aims to explore the role of JAK2/STAT3 in arsenic-induced cell proliferation.

METHODS

By taking normal cells as the research object and using Standard Mean Difference (SMD) as the effect size, meta-analysis was used to explore the effect of arsenic on JAK2/STAT3. Then, the dose-effect Meta was used to further clarify the dose-effect relationship of arsenic on JAK2/STAT3.

RESULTS

Through meta-analysis, this study found that arsenic could promote the phosphorylation of STAT3 (SMD=4.21, 95%CI [1.05, 7.37]), and increase IL-6 and p-JAK2, Vimentin, VEGF expression levels, thereby inducing malignant cell proliferation. In addition, this study also found that arsenic exposure dose (<5 μmol m^-3), time(<24 h) and cell type were important sources of heterogeneity in the process of exploring the effects of arsenic on p-STAT3, IL-6 and p-JAK2. Dose-effect relationship meta-analysis results showed that arsenic exposure significantly increased the expression level of IL-6. When the arsenic exposure concentration was less than 7 μmol m^-3, the expression level of p-JAK2 upregulated significantly as the arsenic exposure concentration gradually increasing. Moreover, the expression level of p-STAT3 elevated significantly with the gradual increase of the arsenic concentration under 5 μmol m^-3 of arsenic exposure, but the expression level of p-STAT3 gradually decreases when the concentration is greater than 5 μmol m^-3.

CONCLUSIONS

Exposure to low dose of arsenic could promote the expression of JAK2/STAT3 and induce the malignant proliferation of cells through upregulating IL-6, and there was dose-effect relationship among them.

Epigenetic Dysregulations in Arsenic-Induced Carcinogenesis

Arsenic is a crucial environmental metalloid whose high toxicity levels negatively impact human health. It poses significant health concerns to millions of people in developed and developing countries such as the USA, Canada, Bangladesh, India, China, and Mexico by enhancing sensitivity to various types of diseases, including cancers. However, how arsenic causes changes in gene expression that results in heinous conditions remains elusive. One of the proposed essential mechanisms that still has seen limited research with regard to causing disease upon arsenic exposure is the dysregulation of epigenetic components. In this review, we have extensively summarized current discoveries in arsenic-induced epigenetic modifications in carcinogenesis and angiogenesis. Importantly, we highlight the possible mechanisms underlying epigenetic reprogramming through arsenic exposure that cause changes in cell signaling and dysfunctions of different epigenetic elements.

Non-malignant respiratory illness associated with exposure to arsenic compounds in the environment

Arsenic (As), a toxic metalloid, primarily originates from both natural and anthropogenic activities. Reports suggested that millions of people globally exposed to high levels of naturally occurring As compounds via inhalation and ingestion. There is evidence that As is a well-known lung carcinogen. However, there has been relatively little evidence suggesting its non-malignant lung effects. This review comprehensively summarises current experimental and clinical studies implicating the association of As exposure and the development of several non-malignant lung diseases. Experimental studies provided evidence that As exposure induces redox imbalance, apoptosis, inflammatory response, epithelial-to-mesenchymal transition (EMT), and affected normal lung development through alteration of the components of intracellular signaling cascades. In addition, we also discuss the sources and possible mechanisms of As influx and efflux in the lung. Finally, current experimental studies on treatment strategies using phytochemicals and our perspective on future research with As are also discussed.

Toxic metals in the regulation of epithelial-mesenchymal plasticity: demons or angels?

Epithelial cells can trans-differentiate into motile mesenchymal cells through a dynamic process known as epithelial-mesenchymal transition (EMT). EMT is crucial in embryonic development and wound healing but also contributes to human diseases such as organ fibrosis and cancer progression. Heavy metals are environmental pollutants that can affect human health in various ways, including causing cancers. The cytotoxicity and carcinogenicity of heavy metals are complex, and studies have demonstrated that some of these metals can affect the progress of EMT. Here, we focus on reviewing the roles of six environmentally common toxic metals concerning EMT: arsenic (AS), cadmium (Cd), cobalt (Co), chromium (Cr), nickel (Ni), and copper (Cu). Noteworthily, the effects of these elements on EMT may vary according to the form, dose, and exposure time; the dual role of heavy metals (e.g., AS, Cd, and Cu) on EMT is also observed, in which, sometimes they can promote while sometimes inhibit the EMT process. Given the vast number of toxicologically relevant metals that exist in nature, we believe a comprehensive understanding of their effects on EMT is required to dictate in what circumstances these metals act more likely as demons or angels.

Epigenetic modifications from arsenic exposure: A comprehensive review

Arsenic is a notorious element with the potential to harm exposed individuals in ways that include cancerous and non-cancerous health complications. Millions of people across the globe (especially in South and Southeast Asian countries including China, Vietnam, India and Bangladesh) are currently being unknowingly exposed to precarious levels of arsenic. Among the diverse effects associated with such arsenic levels of exposure is the propensity to alter the epigenome. Although a large volume of literature exists on arsenic-induced genotoxicity, cytotoxicity, and inter-individual susceptibility due to active research on these subject areas from the last millennial, it is only recently that attention has turned on the ramifications and mechanisms of arsenic-induced epigenetic changes. The present review summarizes the possible mechanisms involved in arsenic induced epigenetic alterations. It focuses on the mechanisms underlying epigenome reprogramming from arsenic exposure that result in improper cell signaling and dysfunction of various epigenetic components. The mechanistic information articulated from the review is used to propose a number of novel therapeutic strategies with a potential for ameliorating the burden of worldwide arsenic poisoning.

Chronic arsenic increases cell migration in BEAS-2B cells by increasing cell speed, cell persistence, and cell protrusion length

There is a strong association between arsenic exposure and lung cancer development, however, the mechanism by which arsenic exposure leads to carcinogenesis is not clear. In our previous study, we observed that when BEAS-2B cells are chronically exposed to arsenic, there is an increase in secreted TGFα, as well as an increase in EGFR expression and activity. Further, these changes were broadly accompanied with an increase in cell migration. The overarching goal of this study was to acquire finer resolution of the arsenic-dependent changes in cell migration, as well as to understand the role of increased EGFR expression and activity levels in the underlying mechanisms of cell migration. To do this, we used a combination of biochemical and single cell assays, and observed chronic arsenic treatment enhancing cell migration by increasing cell speed, cell persistence and cell protrusion length. All three parameters were further increased by the addition of TGFα, indicating EGFR activity is sufficient to enhance those aspects of cell migration. In contrast, EGFR activity was necessary for the increase in cell speed, as it was reversed with an EGFR inhibitor, AG1478, but was not necessary to enhance persistence and protrusion length. From these data, we were able to isolate both EGFR-dependent and -independent features of cell migration that were enhanced by chronic arsenic exposure.

Arsenic-induced epigenetic changes in cancer development

Arsenic is a ubiquitous metalloid whose high levels of toxicity pose major health concerns to millions of people worldwide by increasing susceptibility to various cancers and non-cancer illnesses. Since arsenic is not a mutagen, the mechanism by which it causes changes in gene expression and disease pathogenesis is not clear. One possible mechanism is through generation of reactive oxygen species. Another equally important mechanism still very much in its infancy is epigenetic dysregulation. In this review, we discuss recent discoveries underlying arsenic-induced epigenetic changes in cancer development. Importantly, we highlight the proposed mechanisms targeted by arsenic to drive oncogenic gene expression.

Crosstalk between Environmental Inflammatory Stimuli and Non-Coding RNA in Cancer Occurrence and Development

Simple Summary

Increasing evidence has indicated that chronic inflammatory processes have an influence on tumor occurrence and all stages of tumor development. A dramatic increase of studies into non-coding RNAs (ncRNAs) biology has shown that ncRNAs act as oncogenic drivers and tumor suppressors in various inflammation-induced cancers. Thus, this complex network of inflammation-associated cancers and ncRNAs offers targets for prevention from the malignant transformation from inflammation and treatment of malignant diseases.

Abstract

There is a clear relationship between inflammatory response and different stages of tumor development. Common inflammation-related carcinogens include viruses, bacteria, and environmental mutagens, such as air pollutants, toxic metals, and ultraviolet light. The expression pattern of ncRNA changes in a variety of disease conditions, including inflammation and cancer. Non-coding RNAs (ncRNAs) have a causative role in enhancing inflammatory stimulation and evading immune responses, which are particularly important in persistent pathogen infection and inflammation-to-cancer transformation. In this review, we investigated the mechanism of ncRNA expression imbalance in inflammation-related cancers. A better understanding of the function of inflammation-associated ncRNAs may help to reveal the potential of ncRNAs as a new therapeutic strategy.

Dysregulation of microRNAs in metal-induced angiogenesis and carcinogenesis

MicroRNAs (miRNAs) are small endogenous non-coding RNAs that regulate cancer initiation, development, angiogenesis, and therapeutic resistance. Metal exposure widely occurs through air, water, soil, food, and industrial contaminants. Hundreds of millions of people may have metal exposure associated with toxicity, serious health problems, and cancer occurrence. Metal exposure is found to induce oxidative stress, DNA damage and repair, and activation of multiple signaling pathways. However, molecular mechanisms of metal-induced carcinogenesis remain to be elucidated. Recent studies demonstrated that the exposure of metals such as arsenic, hexavalent chromium, cadmium, and nickel caused dysregulation of microRNAs that are implicated to play an important role in cell transformation, tumor growth and angiogenesis. This review focuses on the recent studies that show metal-induced miRNA dysregulation and underlined mechanisms in cell malignant transformation, angiogenesis and tumor growth.

miRNAs Potentially Involved in Post Lung Transplant-Obliterative Bronchiolitis: The Role of miR-21-5p

Epigenetic changes, including miRNAs deregulation, have been suggested to play a significant role in development of obliterative bronchiolitis (OB) in transplanted lungs. Many studies have tried to identify ideal candidate miRNAs and the downstream pathways implicated in the bronchiolar fibro-obliterative process. Several candidate miRNAs, previously indicated as possibly being associated with OB, were analyzed by combining the quantitative real time-polymerase chain reaction (qRT-PCR) and in situ hybridization (ISH) of lung tissues of OB affected patients. Disease and OB-lesion-specific expression of miR-21-5p was confirmed and by computational analysis we were able to identify the network of genes most probably associated miR-21-5p in the context of OB fibrogenesis. Among all potentially associated genes, STAT3 had a very high probability score. Immunohistochemistry showed that STAT3/miR-21-5p were co-over expressed in OB lesions, thus, suggesting miR-21-5p could regulate STAT3 expression. However, miR-21-5p inhibition in cultures of bronchiolitis obliterans syndrome (BOS) derived myofibroblasts did not significantly affect STAT3 mRNA and protein expression levels. This study demonstrates the specificity of miR-21-5p over-expression in OB lesions and contributes to existing knowledge on the miR-21-5p downstream pathway. Activation of STAT3 is associated with miR-21-5p upregulation, however, STAT-3 network activation is most likely complex and miR-21-5p is not the sole regulator of STAT3.

Long noncoding RNA TINCR is a novel regulator of human bronchial epithelial cell differentiation state

Long-noncoding RNAs (lncRNAs) have numerous biological functions controlling cell differentiation and tissue development. The knowledge about the role of lncRNAs in human lungs remains limited. Here we found the regulatory role of the terminal differentiation-induced lncRNA (TINCR) in bronchial cell differentiation. RNA in situ hybridization revealed that TINCR was mainly expressed in bronchial epithelial cells in normal human lung. We performed RNA sequencing analysis of normal human bronchial epithelial cells (NHBECs) with or without TINCR inhibition and found the differential expression of 603 genes, which were enriched for cell adhesion and migration, wound healing, extracellular matrix organization, tissue development and differentiation. To investigate the role of TINCR in the differentiation of NHBECs, we employed air-liquid interface culture and 3D organoid formation assay. TINCR was upregulated during differentiation, loss of TINCR significantly induced an early basal-like cell phenotype (TP63) and a ciliated cell differentiation (FOXJ1) in late phase and TINCR overexpression suppressed basal cell phenotype and the differentiation toward to ciliated cells. Critical regulators of differentiation such as SOX2 and NOTCH genes (NOTCH1, HES1, and JAG1) were significantly upregulated by TINCR inhibition and downregulated by TINCR overexpression. RNA immunoprecipitation assay revealed that TINCR was required for the direct bindings of Staufen1 protein to SOX2, HES1, and JAG1 mRNA. Loss of Staufen1 induced TP63, SOX2, NOTCH1, HES1, and JAG1 mRNA expressions, which TINCR overexpression suppressed partially. In conclusion, TINCR is a novel regular of bronchial cell differentiation, affecting downstream regulators such as SOX2 and NOTCH genes, potentially in coordination with Staufen1.

miR-21-regulated M2 polarization of macrophage is involved in arsenicosis-induced hepatic fibrosis through the activation of hepatic stellate cells

Arsenicosis induced by chronic exposure to arsenic is recognized as one of the main damaging effects on public health. Exposure to arsenic can cause hepatic fibrosis, but the molecular mechanisms by which this occurs are complex and elusive. It is not known if miRNAs are involved in arsenic-induced liver fibrosis. We found that in the livers of mice exposed to arsenite, there were elevated levels of microRNA-21 (miR-21), phosphorylated mammalian target of rapamycin (p-mTOR), and arginase 1 (Arg1); low levels of phosphatase and tensin homolog (PTEN); and more extensive liver fibrosis. For cultured cells, arsenite-induced miR-21, p-mTOR, and Arg1; decreased PTEN; and promoted M2 polarization of macrophages derived from THP-1 monocytes (THP-M), which caused secretion of fibrogenic cytokines, including transforming growth factor-β1. Coculture of arsenite-treated, THP-M with LX-2 cells induced α-SMA and collagen I in the LX-2 cells and resulted in the activation of these cells. Downregulation of miR-21 in THP-M inhibited arsenite-induced M2 polarization and activation of LX-2 cells, but cotransfection with PTEN siRNA or a miR-21 inhibitor reversed this inhibition. Moreover, knockout of miR-21 in mice attenuated liver fibrosis and M2 polarization compared with WT mice exposed to arsenite. Additionally, LN, PCIII, and HA levels were higher in patients with higher hair arsenic levels, and levels of miR-21 were higher than controls and positively correlated with PCIII, LN, and HA levels. Thus, arsenite induces the M2 polarization of macrophages via miR-21 regulation of PTEN, which is involved in the activation of hepatic stellate cells and hepatic fibrosis. The results establish a previously unknown mechanism for arsenicosis-induced fibrosis.

The Mechanism of Trivalent Inorganic Arsenic on HIF-1α: a Systematic Review and Meta-analysis

The purpose of our study was to investigate the role of hypoxia-inducible factor-1α (HIF-1α) in arsenic-induced carcinogenesis. We included 39 articles for meta-analysis. The results showed that low-dose exposure to arsenic (≤ 10 μmol/L) could promote the expression of phosphatidylinositol 3-kinase (PI3K) and phosphorylation-protein kinase B (p-AKT). High-dose arsenic exposure (> 10 μmol/L) promoted the expression of PI3K, HIF-1α, vascular endothelial growth factor (VEGF), and p38MAPK (P38). Acute arsenic exposure (< 24 h) promoted the expression of PI3K, HIF-1α, and VEGF. Chronic arsenic exposure (≥ 24 h) promoted the expression of PI3K, p-AKT, and P38. Moreover, for normal tissue-derived cells, arsenic could induce the increased expression of PI3K, p-AKT, HIF-1α, and VEGF. For tumor tissue-derived cells, arsenic could induce the expression of PI3K, p-AKT, and P38. We found that arsenic exposure could activate the PI3K/AKT pathway, further induce the high expression of HIF-1α, and then upregulate the levels of miRNA-21 and VEGF, promote the expression of proliferating cell nuclear antigen (PCNA), and ultimately lead to malignant cell proliferation. Our findings indicated that arsenic could increase the expression of HIF-1α by activating the PI3K/AKT pathway and eventually induce malignant cell proliferation.

Combinatorial Low Dose Arsenic Trioxide and Cisplatin Exacerbates Autophagy via AMPK/STAT3 Signaling on Targeting Head and Neck Cancer Initiating Cells

Head and neck squamous cell carcinoma (HNSCC) is a highly lethal disease with high-level of epidemic both in the world and Taiwan. Previous studies support that head and neck cancer-initiating cells (HN-CICs), a subpopulation of cancer cells with enhanced stemness properties, contribute to therapy resistance and tumor recurrence. Arsenic trioxide (As₂O₃; ATO) has shown to be an effective anti-cancer drug targeting acute promyelocytic leukemia (APL). Combinatorial treatment with high dose of ATO and cisplatin (CDDP) exert synergistic apoptotic effects in cancer cell lines of various solid tumors, however, it may cause of significant side effect to the patients. Nevertheless, none has reported the anti-cancerous effect of ATO/CDDP targeting HN-CICs. In this study, we aim to evaluate the low dose combination of ATO with conventional chemo-drugs CDDP treatment on targeting HN-CICs. We first analyzed the inhibitory tumorigenicity of co-treatment with ATO and chemo-drugs on HN-CICs which are enriched from HNSCC cells. We observed that ATO/CDDP therapeutic regimen successfully synergized the cell death on HN-CICs with a Combination Index (CI) <1 by Chou-Talalay's analysis in vitro. Interestingly, the ATO/CDDP regimen also induced exaggerated autophagy on HN-CICs. Additionally, this drug combination strategy also empowered both preventive and therapeutic effect by in vivo xenograft assays. Finally, we provide the underlying molecular mechanisms of ATO-based therapeutic regimen on HN-CICs. Together, low dose of combinatorial ATO/CDDP regimen induced cell death as well as exacerbated autophagy via AMPK-STAT3 mediated pathway in HN-CICs.

Role of JAK/STAT3 Signaling in the Regulation of Metastasis, the Transition of Cancer Stem Cells, and Chemoresistance of Cancer by Epithelial-Mesenchymal Transition

The JAK/STAT3 signaling pathway plays an essential role in various types of cancers. Activation of this pathway leads to increased tumorigenic and metastatic ability, the transition of cancer stem cells (CSCs), and chemoresistance in cancer via enhancing the epithelial–mesenchymal transition (EMT). EMT acts as a critical regulator in the progression of cancer and is involved in regulating invasion, spread, and survival. Furthermore, accumulating evidence indicates the failure of conventional therapies due to the acquisition of CSC properties. In this review, we summarize the effects of JAK/STAT3 activation on EMT and the generation of CSCs. Moreover, we discuss cutting-edge data on the link between EMT and CSCs in the tumor microenvironment that involves a previously unknown function of miRNAs, and also discuss new regulators of the JAK/STAT3 signaling pathway.

Ginkgo biloba extract attenuates the disruption of pro-and anti-inflammatory T-cell balance in peripheral blood of arsenicosis patients

Endemic arsenicosis is a public health problem that affects thousands of people worldwide. However, the biological mechanism involved is not well characterized, and there is no specific treatment. Exposure to arsenic may be associated with immune-related problems. In the present work, we performed an investigation to determine whether the Th17/Treg balance was abnormal in peripheral blood mononuclear cells (PBMCs) of patients with arsenicosis caused by burning coal. Furthermore, we investigated the effect of Ginkgo biloba extract (GBE) on the Th17/Treg imbalance in patients with arsenicosis. In this trial, 81 arsenicosis patients and 37 controls were enrolled. The numbers of Th17 and Treg cells, as well as related transcription factors and serum cytokines, were determined at the beginning and end of the study. Patients with arsenicosis exhibited higher levels of Th17 cells, Th17-related cytokines (IL-17A and IL-6), and the transcription factor RORγt. There were lower levels of Treg cells, a Treg-related cytokine (IL-10), and the transcription factor Foxp3 as compared with controls. There was a positive correlation between the levels of Th17 cells and IL-17A and the levels of arsenic in hair. Arsenicosis patients were randomly assigned to a GBE treatment group or a placebo group. After 3 months of follow-up, 74 patients completed the study (39 cases in the GBE group and 35 in the placebo group). Administration of GBE to patient upregulated the numbers of Treg cells and the level of IL-10 and downregulated the numbers of Th17 cells and the levels of cytokines associated with Th17 cells. The mRNA levels of Foxp3 and RORγt were increased and decreased, respectively. These results indicated that exposure to arsenic is associated with immune-related problems. The present investigation describes a previously unknown mechanism showing that an imbalance of pro- and anti-inflammatory T cells is involved in the pathogenesis of arsenicosis and that a GBE exerts effects on arsenicosis through regulation of the pro- and anti-inflammatory T cell balance.

Arsenic-Induced Carcinogenesis: The Impact of miRNA Dysregulation

Arsenic is a toxic metalloid widely present in the earth's crust, and is a proven human carcinogen. Chronic arsenic exposure mainly through drinking water causes skin, lung, and urinary bladder cancers, and is associated with liver, prostate, and kidney cancers, cardiovascular and neurological disorders, and diabetes. Several modes of action have been suggested in arsenic carcinogenesis. However, the molecular etiology of arsenic-induced cancer remains unclear. Recent evidence clearly indicates that gene expression modifications induced by arsenic may involve epigenetic alterations, including miRNA dysregulation. Many miRNAs have been implicated in different human cancers as a consequence of losses and or gains of miRNA function that contribute to cancer development. Progress in identifying miRNA dysregulation induced by arsenic has been made using different approaches and models. The present review discusses the recent data regarding dysregulated expression of miRNA in arsenic-induced malignant transformation in vitro, gaps in current understanding and deficiencies in current models for arsenic-induced carcinogenesis, and future directions of research that would improve our knowledge regarding the mechanisms involved in arsenic-induced carcinogenesis.

Andrographolide antagonizes the cigarette smoke-induced epithelial-mesenchymal transition and pulmonary dysfunction through anti-inflammatory inhibiting HOTAIR

In cells of the lung surface, cigarette smoke (CS) induces inflammatory and epithelial-mesenchymal transition (EMT), effects that are related to pulmonary dysfunction and Chronic obstructive pulmonary disease (COPD). However, the molecular mechanisms involved remain largely unknown, and potential therapeutic approaches are under development. In the present study, with cell culture and animal studies, we showed that CS exposure causes pulmonary dysfunction and airway remodeling with inflammatory cell infiltration. Consistent with these pulmonary lesions, the inflammatory factors interleukin-6 (IL-6) and interleukin-8 (IL-8) were increased in mice exposed to CS for 4 days. Accordingly, downstream signal transducer and activator of transcription 3 (STAT3) was activated, which up-regulated expression of the lncRNA HOTAIR, and enhancer of zeste homolog 2 (EZH2). In addition, CS exposure led to decreased levels of E-cadherin and to increased N-cadherin, vimentin, and α-SMA, indicating that the EMT was induced in mouse lung tissues. These effects, including increases of IL-6 and HOTAIR, were confirmed in human bronchial epithelial (HBE) cells treated with cigarette smoke extract (CSE). Finally, we established that, in HBE cells, andrographolide reversed the CSE-induced EMT via decreasing IL-6 levels and, in an animal model, prevented CS-induced lung inflammation and small airway remodeling, indicating that it has potential clinical application for CS-induced pulmonary dysfunction and COPD.

miR‑625‑5p suppresses inflammatory responses by targeting AKT2 in human bronchial epithelial cells

Asthma is a common chronic inflammatory airway disease; however, whether microRNAs (miRs) could be used in the treatment of asthma remains unclear. The aim of the present study was to investigate the role of miR‑625‑5p in the inflammatory response of human bronchial epithelial cells (HBECs). Inflammation in the HBEC line, 16HBEC, was induced using different concentrations of lipopolysaccharide (LPS), which demonstrated that 1 µg/ml LPS was an appropriate concentration for further experiments. The association between protein kinase B2 (AKT2) and miR‑625‑5p was verified using a luciferase reporter assay. LPS was added to 16HBECs following the administration of miR‑625‑5p mimics or miR‑625‑5p inhibitors, and cells with silenced or overexpressed AKT2 levels. miR‑625‑5p was expressed at a high level in LPS‑activated 16HBECs. Overexpression of miR‑625‑5p inhibited interleukin (IL)‑6 and tumor necrosis factor (TNF)‑α secretion in 16HBECs. Inhibition of miR‑625‑5p enhanced LPS‑induced IL‑6 and TNF‑α secretion. miR‑625‑5p negatively regulated the expression of AKT2 in 16HBECs. A dual‑luciferase reporter assay system confirmed that miR‑625‑5p directly targeted the 3'untranslated region of AKT2. Transfection with a small interfering RNA against AKT2 inhibited inhibitor of κB phosphorylation. In brief, miR‑625‑5p may protect LPS‑induced HBECs by targeting AKT2 and inhibiting the nuclear factor‑κB signaling pathway. Therefore, miR‑625‑5p may function as an inhibitor of asthma airway inflammation in HBECs by targeting AKT2.

Urothelial Cancer Stem Cell Heterogeneity

Urothelial carcinoma is a tumor type featuring pronounced intertumoral heterogeneity and a high mutational and epigenetic load. The two major histopathological urothelial carcinoma types - the non-muscle-invasive and muscle-invasive urothelial carcinoma - markedly differ in terms of their respective typical mutational profiles and also by their probable cells of origin, that is, a urothelial basal cell for muscle-invasive carcinomas and a urothelial intermediate cell for at least a large part of non-muscle-invasive carcinomas. Both non-muscle-invasive and muscle-invasive urothelial carcinomas can be further classified into discrete intrinsic subtypes based on their typical transcriptomic profiles. Urothelial carcinogenesis shows a number of parallels to a urothelial regenerative response. Both of these processes seem to be dominated by specific stem cell populations. In the last years, the nature and location of urothelial stem cell(s) have been subject to many controversies, which now seem to be settled down, favoring the existence of a largely single urothelial stem cell type located among basal cells. Basal cell markers have also been amply used to identify urothelial carcinoma stem cells, especially in muscle-invasive disease, but they proved useful even in some non-muscle-invasive tumors. Analyses on molecular nature of urothelial carcinoma stem cells performed till now point to their great heterogeneity, both during the tumor development and upon intertumoral comparison, sexual dimorphism providing a special example of the latter. Moreover, urothelial cancer stem cells are endowed with intrinsic plasticity, whereby they can modulate their stemness in relation to other tumor-related traits, especially motility and invasiveness. Such transitional modulations suggest underlying epigenetic mechanisms and, even within this context, inter- and intratumoral heterogeneity becomes apparent. Multiple molecular aspects of urothelial cancer stem cell biology markedly influence therapeutic response, implying their knowledge as a prerequisite to improved therapies of this disease. At the same time, the notion of urothelial cancer stem cell heterogeneity implies that this therapeutic benefit would be most probably and most efficiently achieved within the context of individualized antitumor therapy.

Malignant Transformation of Human Bronchial Epithelial Cells Induced by Arsenic through STAT3/miR-301a/SMAD4 Loop

Arsenic is a well-known of human carcinogen and miR-301a is an oncogenic microRNA, which links to oncogenesis, however, little is understood about its contribution to arsenic-induced cellular transformation and tumorigenesis. Here, we investigated the role of miR-301a during arsenic-induced cellular transformation and tumor formation. miR-301a was found to be upregulated during arsenic-induced BEAS-2B transformation and the overexpression of miR-301a was dependent on IL-6/STAT3 signaling. Inhibition of miR-301a leads to reduction of cell proliferation, colony formation and cell migration. By using dual luciferase assay, SMAD4 was confirmed to be a direct target of miR-301a in BEAS-2B cells and upregulation of SMAD4 is involved the restraining cell growth and migration. In addition, reducing of miR-301a expression enhances doxorubicin-induced cellular apoptosis of transformed BEAS-2B through up-regulating SMAD4. Furthermore, we demonstrated that downregulation of miR-301a in BEAS-2B attenuates tumor growth in the xenograft model by targeting SMAD4. Of note, the level of miR-301a expression correlated inversely with SMAD4 expression in clinical specimens of human lung cancer. Our findings ascertain that miR-301a is an oncogenic miRNA, which targets SMAD4 to establish an essential mechanism for arsenic-induced carcinogenesis, IL-6/STAT3/miR-301a/SMAD4 signaling pathways.

Exosomal circRNA_100284 from arsenite-transformed cells, via microRNA-217 regulation of EZH2, is involved in the malignant transformation of human hepatic cells by accelerating the cell cycle and promoting cell proliferation

Intercellular communication between malignant cells and neighboring nonmalignant cells is involved in carcinogenesis. In the progression of carcinogenesis, exosomes are messengers for intercellular communication. Circular RNAs (circRNAs) are noncoding RNAs with functions that include regulation of the cell cycle and proliferation. However, the functions of exosomal circRNAs are not clear. The present research aimed to determine whether circRNAs secreted from arsenite-transformed human hepatic epithelial (L-02) cells are transferred into normal L-02 cells and become functionally active in the normal cells. The results showed that circRNA_100284 is involved in the malignant transformation of L-02 cells induced by arsenite. The medium from transformed L-02 cells induced upregulation of circRNA_100284, accelerated the cell cycle, and promoted proliferation of normal L-02 cells. Transformed cells transferred circRNA_100284 into normal L-02 cells via exosomes and led to the malignant transformation of the non-transformed cells. Knockdown of circRNA_100284, which reduced circRNA_100284 levels in exosomes derived from transformed L-02 cells, blocked the accelerated cell cycle and reduced proliferation and malignancy. In addition, in normal L-02 cells, exosomal circRNA_100284 derived from arsenite-transformed L-02 cells induced acceleration of the cell cycle and promoted proliferation via acting as a sponge of microRNA-217. Further, exosomal circRNA_100284 was upregulated in the sera of people exposed to arsenite. Thus, exosomes derived from transformed L-02 cells transferred circRNA_100284 to surrounding cells, which induced an accelerated cell cycle and promoted proliferation of normal liver cells and led to the malignant transformation of the non-transformed cells. The findings support the concept that exosomal circRNAs are involved in cell–cell communication during carcinogenesis induced by arsenite.

Defining the regulatory role of programmed cell death 4 in laryngeal squamous cell carcinoma

Programmed cell death 4 (PDCD4) is decreased in many different kinds of malignant tumors. EMT endows tumor cells invasive and metastatic properties. However, few studies have determined the role of PDCD4 in the regulation of EMT in the context of laryngeal carcinoma. We examined the relationship between PDCD4 and EMT-associated proteins E-cadherin and N-cadherin using laryngeal carcinoma tissues. Gene manipulation was used to define the regulatory capacity of PDCD4. We report that PDCD4 and E-cadherin/N-cadherin expression were significantly changed in the carcinoma tissues, and their expression was associated with pathological grade, metastatic state, and clinical stage. The suppression of PDCD4 (and consequently, E-cadherin) was concomitant with increased proliferation and G2-phase arrest, decreased apoptosis, and increased cell invasion. PDCD4 upregulation reversed the above-mentioned results. In nude mice, PDCD4 knockdown increased tumor growth and pathological features, confirming the tumorigenic role of PDCD4. Finally, PDCD4 silencing was associated with dysregulation of the carcinogenic Wnt-β-catenin and the STAT3-miR-21 signaling pathways. This study revealed a dynamic regulatory relationship between PDCD4 and critical factors for EMT, establishing a broad, functional role for PDCD4 in laryngeal carcinoma, which may be propagated by the STAT3-miR-21 pathway. These findings provide new information on an EMT-associated target that may lead to a novel therapy.

Epithelial-mesenchymal transition in breast epithelial cells treated with cadmium and the role of Snail

Epidemiological and experimental studies have implicated cadmium (Cd) with breast cancer. In breast epithelial MCF10A and MDA-MB-231 cells, Cd has been shown to promote cell growth. The present study examined whether Cd also promotes epithelial-mesenchymal transition (EMT), a hallmark of cancer progression. Human breast epithelial cells consisting of non-cancerous MCF10A, non-metastatic HCC 1937 and HCC 38, and metastatic MDA-MB-231 were treated with 1 or 3 μM Cd for 4 weeks. The MCF10A epithelial cells switched to a more mesenchymal-like morphology, which was accompanied by a decrease in the epithelial marker E-cadherin and an increase in the mesenchymal markers N-cadherin and vimentin. In both non-metastatic HCC 1937 and HCC 38 cells, treatment with Cd decreased the epithelial marker claudin-1. In addition, E-cadherin also decreased in the HCC 1937 cells. Even the mesenchymal-like MDA-MB-231 cells exhibited an increase in the mesenchymal marker vimentin. These changes indicated that prolonged treatment with Cd resulted in EMT in both normal and cancer-derived breast epithelial cells. Furthermore, both the MCF10A and MDA-MB-231 cells labeled with Zcad, a dual sensor for tracking EMT, demonstrated a decrease in the epithelial marker E-cadherin and an increase in the mesenchymal marker ZEB-1. Treatment of cells with Cd significantly increased the level of Snail, a transcription factor involved in the regulation of EMT. However, the Cd-induced Snail expression was completely abolished by actinomycin D. Luciferase reporter assay indicated that the expression of Snail was regulated by Cd at the promotor level. Snail was essential for Cd-induced promotion of EMT in the MDA-MB-231 cells, as knockdown of Snail expression blocked Cd-induced cell migration. Together, these results indicate that Cd promotes EMT in breast epithelial cells and does so by modulating the transcription of Snail.

Regorafenib (Stivarga) pharmacologically targets epithelial-mesenchymal transition in colorectal cancer

Epithelial-to-mesenchymal transition (EMT) is well-known to evoke cancer invasion/metastasis, leading to a high frequency of mortality in patients with metastatic colorectal cancer (mCRC). Protein tyrosine phosphatase (PTPase)-targeted therapy has been identified as a novel cancer therapeutic. Previously, we proved that sorafenib with anti-EMT potency prevents TGF-β1-induced EMT/invasion by directly activating SH2-domain-containing phosphatase 1 (SHP-1)-dependent p-STAT3Tyr705 suppression in hepatocellular carcinoma. Regorafenib has a closely related chemical structure as sorafenib and is approved for the pharmacotherapy of mCRC. Herein, we evaluate whether regorafenib activates PTPase SHP-1 in the same way as sorafenib to abolish EMT-related invasion/metastasis in CRC. Notably, regorafenib exerted potent anti-EMT activity to curb TGF-β1-induced EMT/invasion in vitro as well inhibited lung metastatic outgrowth of SW480 mesenchymal cells in vivo. Mechanistically, regorafenib-enhanced SHP-1 activity significantly impeded TGF-β1-induced EMT/invasion via low p-STAT3Tyr705 level as proved by a SHP-1 inhibitor or siRNA-mediated SHP-1 depletion. Conversely, overexpression of SHP-1 further enhanced the inhibitory effects of regorafenib on TGF-β1-induced p-STAT3Tyr705 and EMT/invasion. Regorafenib directly activates SHP-1 by potently relieving the autoinhibited N-SH2 domain of SHP-1 to inhibit TGF-β1-induced p-STAT3Tyr705 and EMT/invasion. Importantly, the clinical evidence indicated that SHP-1 was positively correlated with E-cadherin and that significantly determined the overall survival of CRC patients. This result further confirms our in vitro data that SHP-1 is a negative regulatory PTPase in EMT regulation and serves as a pharmacological target for mCRC therapy. Collectively, activating PTPase SHP-1 by regorafenib focusing on its anti-EMT activity might be a useful pharmacotherapy for mCRC.

MicroRNA-191, regulated by HIF-2α, is involved in EMT and acquisition of a stem cell-like phenotype in arsenite-transformed human liver epithelial cells

Inorganic arsenic is widely distributed in the environment, and epidemiologic data show a strong association between arsenic exposure and risk of liver cancer. An understanding of the mechanisms underlying development of liver cancer and metastasis would be useful in reducing the incidence and mortality of liver cancer. MicroRNAs (miRs) act as regulators in liver cancer. Here, we show that acute or chronic exposure of human liver epithelial L-02 cells to arsenite increased expression of miR-191. There were decreased levels of BASP-1 and E-cadherin and increased levels of WT-1 and N-cadherin, indicating that arsenite induced epithelial-mesenchymal transition (EMT). Moreover, arsenite increased EpCAM and CD90 mRNA levels, showing the acquisition of stem cell-like properties by these cells. Suppression of miR-191 resulted in repression of EMT and reduced expression of stem-cell markers. Further, a miR-191 inhibitor blocked spheroid formation and production of side population cells. Luciferase reporter assays indicated that miR-191 was a target of HIF-2α, and inhibition of miR-191 decreased the neoplastic and metastatic properties of arsenite-transformed L-02 cells. Thus, in arsenite-transformed liver epithelial cells, transcriptional activation of the miR-191 promoter by HIF-2α is involved in EMT and in the acquisition of a stem cell-like phenotype.

Alterations of miRNAs and Their Potential Roles in Arsenite-Induced Transformation of Human Bronchial Epithelial Cells

The alterations of micro RNAs (miRNAs) and their potential roles in arsenite-induced tumorigenesis are still poorly understood. In this study, miRNA Array was used to detect the expression level of miRNAs in human bronchial epithelial (HBE) cells that were transformed by 2.5 μM arsenite for 13 weeks. These cells exhibited a neoplastic phenotype manifested by increased levels of cellular proliferation and migration and clone formation. Subsequently, 191 dysregulated miRNAs were identified to be associated with arsenite-induced transformation by miRNA Array. Among them, six miRNAs were validated by their expression levels with quantitative real-time polymerase chain reaction (qPCR), and 17 miRNAs were further explored via their target genes as well as regulatory network. Three databases, TargetMiner, miRDB, and TarBase, were used to predict the target genes of the 17 miRNAs, and a total of 954 common genes were sorted. Results of Gene Ontology (GO) analyses showed that the 954 genes were involved in diverse terms of GO categories, such as positive regulation of macroautophagy, epithelial cell maturation, and synaptic vesicle clustering. Moreover, results of Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses demonstrated that most of these target genes were enriched in various cancer-related pathways, including non-small cell lung cancer, Wnt signaling pathway, cell cycle, and p53 signaling pathway. The miRNA-gene regulatory network, which was constructed by cytoscape software with miRNAs and their target genes, showed that miR-15b-5p, miR-106b-5p, and miR-320d were the core hubs. Collectively, our results provide new insights into miRNA-mediated mechanisms underlying arsenite-induced transformation, although more experimental verification is still needed to prove these predictions.

Epithelial-to-Mesenchymal Transition and MicroRNAs in Lung Cancer

Despite major advances, non-small cell lung cancer (NSCLC) remains the major cause of cancer-related death in developed countries. Metastasis and drug resistance are the main factors contributing to relapse and death. Epithelial-to-mesenchymal transition (EMT) is a complex molecular and cellular process involved in tissue remodelling that was extensively studied as an actor of tumour progression, metastasis and drug resistance in many cancer types and in lung cancers. Here we described with an emphasis on NSCLC how the changes in signalling pathways, transcription factors expression or microRNAs that occur in cancer promote EMT. Understanding the biology of EMT will help to define reversing process and treatment strategies. We will see that this complex mechanism is related to inflammation, cell mobility and stem cell features and that it is a dynamic process. The existence of intermediate phenotypes and tumour heterogeneity may be debated in the literature concerning EMT markers, EMT signatures and clinical consequences in NSCLC. However, given the role of EMT in metastasis and in drug resistance the development of EMT inhibitors is an interesting approach to counteract tumour progression and drug resistance. This review describes EMT involvement in cancer with an emphasis on NSCLC and microRNA regulation.

MicroRNA-155 regulates arsenite-induced malignant transformation by targeting Nrf2-mediated oxidative damage in human bronchial epithelial cells

Arsenite is a well-documented human lung carcinogen but the detailed mechanisms of carcinogenesis remain unclear. In this study, human bronchial epithelial (16-HBE) cells were continuously exposed to 2.5μM arsenite for about 13 weeks to induce the phenotypes of malignant transformation. Our results showed that Nrf2 expression was gradually decreased whereas no significant change was observed on NF-κB activation with increased time of arsenite exposure. To test the roles of Nrf2-meidtaed oxidative damage in the arsenite-induced malignant transformation, we compared the levels of cGMP, PKG and oxidative damage-related indicators between arsenic-transformed cells and control cells. Our data demonstrated there were no significantly differences on the contents of cGMP, PKG, MDA and the production of ROS, but the levels of GSH and NO, the activities of SOD, tNOS and iNOS were significantly enhanced in the arsenic-transformed cells. Importantly, Nrf2 inactivation could be modulated by miR-155, and inhibition of miR-155 remarkably attenuated the malignant phenotypes and promoted apoptotic cell death in the arsenic-transformed cells. Together, our findings provide the novel mechanism that miR-155 may regulate arsenite-induced cell malignant transformation by targeting Nrf2-mediated oxidative damage, indicating that inhibition of miR-155 may be a potential strategy against lung carcinogenesis of arsenite.

Low-level arsenic causes chronic inflammation and suppresses expression of phagocytic receptors

The impact of chronic low-level groundwater arsenic (As) exposure [in the range above the WHO-recommended limit of 10 μg/L but ≤50 μg/L (permissible limit of As for many Asian countries)] was investigated for cross talk of inflammatory changes and expression of phagocytic receptors of exposed rural women (N, 45) from districts of 24 Parganas (south) and in matched control groups (N, 43) [As ≤10 μg/L] from the same district. Systemic inflammation was evident from the upregulated levels of pro-inflammatory mediators like tumor necrosis factor-α (TNF-α); interleukins (ILs) like IL-6, IL-8, and IL-12; and C-reactive protein (CRP) in the sera and upregulated expression of protein kinase B phosphorylated at ser473 (pAKTser473)/nuclear factor-κB (NF-κB)/TNF-α axis in the leukocytes of exposed women with respect to control. We found that low-dose As exposure apart from inflicting inflammation altered the expression of phagocytic receptors-Fcγ receptors (FcγRs) and complement receptors (CRs). The leukocytes of the low-As-exposed women exhibited suppression of CD64, CD35, and CD11b and increased expression of CD16 with respect to control. Groundwater As showed a negative correlation with CD64 expression on monocytes [Pearson's r, -0.8205; 95% confidence interval (CI), -0.8789 to -0.7379] and granulocytes [r, -0.7635; 95% CI, -0.8388 to -0.6595] and a positive correlation with CD16 on granulocytes [r, 0.8363; 95% CI, 0.7599 to 0.8899]. A negative correlation of groundwater As was also observed with expression of CD35 on granulocytes [r, -0.8780; 95% CI, -0.9185 to -0.8192] and monocytes [r, -0.7778; 95% CI, -0.8490 to -0.6790] and CD11b on monocytes [r, -0.6035; 95% CI, -0.7218 to -0.4511]. Therefore, it may be indicated that chronic low-level As exposure (11-50 μg/L) not only evoked chronic inflammatory changes but also suppressed the expression of FcγRs and CRs in the exposed women. This, in turn, may lead to susceptibility towards pathogenic infections or in long run may even contribute towards chronic inflammatory diseases including cancer.

Extracellular vesicles in lung cancer-From bench to bedside

Lung cancer is the leading cause of cancer-related deaths worldwide. Despite significant advances in lung cancer research and novel therapies, a better understanding of the disease is crucially needed to facilitate early detection and appropriate diagnoses and to improve treatment outcomes. Extracellular vesicles (EVs), including exosomes, microvesicles, and apoptotic bodies, are released from all tested cell types and modulate cell-cell communication. EVs transfer a wide variety of molecules, such as proteins, messenger RNAs and microRNAs. Emerging data suggest that EVs play an important role in lung cancer pathogenesis and may have potential as biomarkers and therapeutics. Here, we review current research on EVs in lung cancer.

Regulation of EMT by STAT3 in gastrointestinal cancer (Review)

Gastrointestinal (GI) cancer is characterized by its aggressiveness and tendency to metastasize at early stage. Epithelial-mesenchymal transition (EMT), commonly known as the preparing step of metastasis, may account for the aggressive phenotype of GI cancer cells. The process of EMT is finely orchestrated by multiple layers of regulators. Signal transducer and activator of transcription 3 (STAT3) is a transcription factor constitutively activated in diverse malignancies. Recent studies have suggested an involvement of STAT3 in GI cancer EMT. In this review, we first take an insight into the oncogenic functions of STAT3 in GI cancer, and then summarize the possible mechanisms by which STAT3 regulates the EMT process. Through the extensive interactions with EMT-inducing transcription factors and non-coding RNAs, and crosstalk with other signaling pathways, STAT3 has been demonstrated to promote the mesenchymal and invasive phenotype of GI cancer, which provides rationales for specifically targeting STAT3 to prevent and reverse the progression of GI cancer.

The role of microRNAs in metal carcinogen-induced cell malignant transformation and tumorigenesis

MicroRNAs (miRNAs), an important component of epigenetic mechanisms of carcinogenesis, have been shown to play crucial roles in cancer initiation, metastasis, prognosis and responses to drug treatment and may serve as biomarkers for early diagnosis of cancer and tools for cancer therapy. Metal carcinogens, such as arsenic, cadmium, hexavalent chromium and nickel, are well-established human carcinogens causing various cancers upon long term exposure. However, the mechanism of metal carcinogenesis has not been well understood, which limits our capability to effectively diagnose and treat human cancers resulting from chronic metal carcinogen exposure. Over recent years, the role of miRNAs in metal carcinogenesis has been actively explored and a growing body of evidence indicates the critical involvement of miRNAs in metal carcinogenesis. This review aims to discuss recent studies showing that miRNAs play important roles in metal carcinogen-induced cell malignant transformation and tumorigenesis. Some thoughts for future further studies in this field are also presented.

Aberrant Splicing in Cancer: Mediators of Malignant Progression through an Imperfect Splice Program Shift

Although the efforts to understand the genetic basis of cancer allowed advances in diagnosis and therapy, little is known about other molecular bases. Splicing is a key event in gene expression, controlling the excision of introns decoded inside genes and being responsible for 80% of the proteome amplification through events of alternative splicing. Growing data from the last decade point to deregulation of splicing events as crucial in carcinogenesis and tumor progression. Several alterations in splicing events were observed in cancer, caused by either missexpression of or detrimental mutations in some splicing factors, and appear to be critical in carcinogenesis and key events during tumor progression. Notwithstanding, it is difficult to determine whether it is a cause or consequence of cancer and/or tumorigenesis. Most reviews focus on the generated isoforms of deregulated splicing pattern, while others mainly summarize deregulated splicing factors observed in cancer. In this review, events associated with carcinogenesis and tumor progression mainly, and epithelial-to-mesenchymal transition, which is also implicated in alternative splicing regulation, will be progressively discussed in the light of a new perspective, suggesting that splicing deregulation mediates cell reprogramming in tumor progression by an imperfect shift of the splice program.

Novel evidence for an oncogenic role of microRNA-21 in colitis-associated colorectal cancer

OBJECTIVE

miR-21 was found to be overexpressed in the colon tissues and serum of patients with UC and colorectal cancer (CRC); however, the exact roles of miR-21 in colitis-associated CRC remain unclear. The aim of our study was to investigate the biological mechanisms of miR-21 in colitis-associated colon cancer (CAC).

DESIGN

miR-21 expression was examined in the tumours of 62 patients with CRC from China and 37 colitis-associated neoplastic tissues from Japan and Austria. The biological functions of miR-21 were studied using a series of in vitro, in vivo and clinical approaches.

RESULTS

miR-21 levels were markedly upregulated in the tumours of 62 patients with CRC, 22 patients with CAC, and in a mouse model of CAC. Following azoxymethane and dextran sulfate sodium intervention, miR-21-knockout mice showed reduced expression of proinflammatory and procarcinogenic cytokines (interleukin (IL) 6, IL-23, IL-17A and IL-21) and a decrease in the size and number of tumours compared with the control mouse group. The absence of miR-21 resulted in the reduced expression of Ki67 and the attenuated proliferation of tumour cells with a simultaneous increase in E-cadherin and decrease in β-catenin and SOX9 in the tumours of CAC mice. Furthermore, the absence of miR-21 increased the expression of its target gene PDCD4 and subsequently modulated nuclear factor (NF)-κB activation. Meanwhile, miR-21 loss reduced STAT3 and Bcl-2 activation, causing an increase in the apoptosis of tumour cells in CAC mice.

CONCLUSIONS

These observations provide novel evidence for miR-21 blockade to be a key strategy in reducing CAC.

MicroRNA-21 activation of ERK signaling via PTEN is involved in arsenite-induced autophagy in human hepatic L-02 cells

Autophagy, an evolutionarily conserved cellular process, has diverse physiological and pathological roles in biological functions. Whether autophagy is induced by arsenite, a well-established human carcinogen, and the molecular mechanisms involved, remain to be established. Further, microRNAs (miRNAs) act as regulators in various cancers, but how miRNAs regulate autophagy remains largely unexplored. We have found that, in human hepatic epithelial (L-02) cells, arsenite increases levels of autophagy-related proteins in a concentration- and time-dependent manner and elevates the number of autophagic vacuoles (AVs). Arsenite also activates the ERK pathway in a dose- and time-dependent manner. In L-02 cells exposed to arsenite, microRNA-21 (miRNA-21) is over-expressed, and its target proteins, PTEN, PDCD4, and Spry1, are decreased. Moreover, inhibition of miR-21 increases levels of PTEN, and reduces levels of Beclin 1 and LC3 II/I, indicating that miR-21 is involved in arsenite-induced autophagy. In addition, ectopic expression of PTEN blocks the effect of miR-21 on the arsenite-induced autophagy and decreases p-ERK levels. Also, ERK promotes the autophagy induced by arsenite. In sum, upon exposure of cells to arsenite, over-expression of miR-21 activates ERK through PTEN, factors that participate in arsenite-induced autophagy. This link, mediated through miRNAs, establishes a mechanism for the development of autophagy that is associated with arsenic toxicity. Such information contributes to an understanding of the liver toxicity caused by arsenite.

Granzyme M expressed by tumor cells promotes chemoresistance and EMT in vitro and metastasis in vivo associated with STAT3 activation

Granzyme M is a serine protease known to be often expressed by natural killer cells and induce target cells apoptosis in combination with perforin. However, we detected granzyme M expression in murine and human cancer cell lines and human tumor samples in our study. Granzyme M increased chemoresistance, colony-formation, cytokine secretion and invasiveness in vitro. Most importantly, granzyme M facilitated tumor growth and metastasis in vivo. Granzyme M induced the epithelial-mesenchymal transition (EMT) in cancer cells associated with STAT3 activation. Our study revealed the role of granzyme M expressed by tumor in chemoresistance, invasion, metastasis and EMT.

Cancer development, chemoresistance, epithelial to mesenchymal transition and stem cells: A snapshot of IL-6 mediated involvement

Interleukin-6 (IL-6) is a cytokine present in tumor microenvironment. Elevated level of IL-6 is associated with cancer cell proliferation, angiogenesis and metastasis through fueling STAT3, MAPK and Akt signaling. It promotes epithelial to mesenchymal transition (EMT) through altered expression of N-cadherin, vimentin, snail, twist and E-cadherin leading to cancer metastasis. IL-6 boosts mammosphere formation, self-renewal of stem cells, stemness properties of cancer cells and recruitment of mesenchymal stem cells. IL-6 is also a contributing factor for multidrug resistance in cancer due to gp130/MAPK/STAT3 mediated activation of transcription factors C/EBPβ/δ, overexpression of p-glycoprotein, EMT transition and expansion of stem cells. The in-depth investigation of IL-6 mediated cellular effects and its signaling pathway can provide the new window for future research and clinical development of IL-6 targeted therapy in cancer. Thus, an overview is delivered in this review deciphering the emerging aspect of the predominant influence of IL-6 in malignant transformation, EMT, cancer-associated stem cells and chemoresistance.