TG-interacting factor mediates arsenic-induced malignant transformation of keratinocytes via c-Src/EGFR/AKT/FOXO3A and redox signalings

Hyperphosphorylation of EGFR/ERK signaling facilitates long-term arsenite-induced hepatocytes epithelial-mesenchymal transition and liver fibrosis in sprague-dawley rats

Arsenic is a well known environmental hazardous material, chronic arsenic exposure results in different types of liver damage. Among them, liver fibrosis has become a research hotspot because of its reversibility, while the underlying mechanism is still unclear. Previous studies revealed that EGFR/ERK signaling appears to play an important role in fibrosis diseases. In this study, sprague-dawley rats were exposed to different doses of arsenite for 36 weeks to investigate the roles of EGFR/ERK signaling on arsenite-induced liver fibrogenesis. Our results showed that long-term arsenite exposure induced liver fibrosis, accompanied by hepatic stellate cells (HSCs) activation, excessive serum secretion of extracellular matrix (ECM), and hepatocytes epithelial-mesenchymal transformation (EMT). In addition, arsenite exposure caused hyperphosphorylation of EGFR/ERK signaling in liver tissue of rats, indicating that EGFR/ERK signaling may be involved in arsenite-induced liver fibrosis. Indeed, erlotinib (a specific phosphorylation inhibitor of EGFR) intervention significantly decreased arsenite induced hyperphosphorylation of EGFR/ERK signaling, thereby suppressed hepatocytes EMT process and alleviated liver fibrogenesis in arsenite exposed rats. In summary, the present study provides evidences showing that hyperphosphorylation of EGFR/ERK signaling facilitates long-term arsenite-induced hepatocytes EMT and liver fibrosis in rats, which brings new insights into the pathogenesis of arsenic-induced liver injury.

Intravenous As2O3 as a promising treatment for psoriasis - an experimental study in psoriasis-like mouse model

OBJECTIVE

To evaluate the efficacy and mechanistic bases of the intravenous injection of arsenic trioxide at clinical-relevant doses for treating an imiquimod-induced psoriasis-like mouse model.

METHODS

After inducing psoriasis-like skin lesions on the back of mice with imiquimod, mice in each group were injected with a clinical dose of arsenic trioxide through the tail vein. The changes in the gene expression, protein expression and distribution of relevant inflammatory factors were evaluated in the inflicted skin area, for mechanisms underlying the efficacy of intravenous As₂O₃ intervention. HaCaT cells were used to establish an in vitro psoriasis model and pcDNA3.1-NF-κB overexpression plasmid was transfected into cells to overexpress P65, which further confirmed the role of the NF-κB signaling pathway in the effectiveness of As₂O₃.

RESULTS

Clinical dose of As₂O₃ can significantly improve abnormal symptoms and pathological changes in psoriasis-like skin lesions induced by IMQ in mice. While IMQ induced abnormal expression and distribution of inflammatory factors in the RIG-I pathway and the microRNA-31 (miR-31) pathway in psoriatic skin tissues, intravenous As₂O₃ can effectively regulate and restore the normality. The leading role of NF-κB signaling was evidenced in vivo and validated in vitro using the NF-κB-overexpressed HaCaT cell model.

CONCLUSION

Clinical dosage of As₂O₃ may achieve effective treatment of IMQ-induced psoriatic skin lesions by modulating the NF-κB signaling pathway which regulates both the RIG-I and the miR-31 lines of action. Our data provided strong evidence supporting the claim that systemic As₂O₃ administration of clinical doses can be a promising treatment for psoriasis patients.

Hypermethylation of Mig-6 gene promoter region inactivates its function, leading to EGFR/ERK signaling hyperphosphorylation, and is involved in arsenite-induced hepatic stellate cells activation and extracellular matrix deposition

Arsenic is a widespread naturally contaminant. Previous studies have highlighted the issue of liver fibrosis induced by arsenic exposure, while the exact mechanisms are not yet fully understood. Recent studies suggest that Mig-6/EGFR/ERK signaling appear to play important roles in fibrosis caused by various factors. In this study, we focused on the epigenetic modification combined with the signaling dysregulation to validate the role of Mig-6 in regulating EGFR/ERK signaling in arsenite-induced human hepatic stellate cells (HSCs) activation. Our results revealed that arsenite exposure induced HSCs activation and extracellular matrix (ECM) deposition. The EGFR/ERK signaling was significantly hyperphosphorylated in arsenite-exposed HSCs, and Mig-6 inactivation was involved in arsenite induced hyperphosphorylation of EGFR and activation of HSCs. Additionally, we further illustrated that hypermethylation of Mig-6 gene promoter region was responsible for the downregulation of Mig-6 induced by arsenite exposure. Moreover, 5-Aza-dC (a DNA methyltransferase inhibitor) can efficiently rescue hypermethylation of Mig-6 gene, decrease the hyperphosphorylation of EGFR/ERK signaling, then reverse arsenite induced HSCs activation. Taken together, the present study strongly suggests that inactivating of Mig-6 function by hypermethylation of its promoter region leading to hyperphosphorylation of EGFR/ERK signaling, and is involved in arsenite-induced HSCs activation and ECM deposition.

Akt Regulated Phosphorylation of GSK-3β/Cyclin D1, p21 and p27 Contributes to Cell Proliferation Through Cell Cycle Progression From G1 to S/G2M Phase in Low-Dose Arsenite Exposed HaCat Cells

Arsenic is a toxic environmental contaminant. Long-term exposure to arsenic through drinking water induces human cancers. However, it is as yet uncertain about the mechanisms of arsenic induced carcinogenesis. Although the effects of low-dose arsenicals on proliferation and cell cycle have been revealed by short time exposure, the evidences for long-term exposure were seldom reported. The detailed mechanism has been unclear and supplemented constantly. In the present study, we used normal human keratinocytes (HaCat) to study the effects of long-term, low-dose sodium arsenite (NaAsO₂) exposure on cell proliferation with emphasis on the Akt regulated cell cycle signaling pathways. Treatment of NaAsO₂ resulted in increased cell proliferation and promotion of cell cycle progression from G1 to S/G2M phase, both of which could be attenuated by MK2206, a highly selective inhibitor of Akt. Along with the increased expression of phospho-Akt (p-Akt, Ser 473), increased expression of p-GSK-3β (Ser 9), p-p21 (Thr 145), p-p27 (Thr 157) and total cyclin D1, and decreased expression of p-cyclin D1 (Thr 286), p21 and p27 were also found in the NaAsO₂ exposed cells. Treatment of MK2206 markedly reversed the expression of all of the above proteins. Our findings indicated that the phosphorylated activation of Akt played a role in the proliferation of HaCat cells upon long-term, low-dose NaAsO₂ exposure through the phosphorylative regulation of its downstream cell cycle regulating factors of GSK-3β/cyclin D1, p21 and p27, which could induce the promotion of cell cycle progression from G1 to S/G2M phase.

Forkhead box O proteins: Crucial regulators of cancer EMT

The epithelial-mesenchymal transition (EMT) is an acknowledged cellular transition process in which epithelial cells acquire mesenchymal-like properties that endow cancer cells with increased migratory and invasive behavior. Forkhead box O (FOXO) proteins have been shown to orchestrate multiple EMT-associated pathways and EMT-related transcription factors (EMT-TFs), thereby modulating the EMT process. The focus of the current review is to evaluate the latest research progress regarding the roles of FOXO proteins in cancer EMT. First, a brief overview of the EMT process in cancer and a general background on the FOXO family are provided. Next, we present the interactions between FOXO proteins and multiple EMT-associated pathways during malignancy development. Finally, we propose several novel potential directions for future research. Collectively, the information compiled herein should serve as a comprehensive repository of information on this topic and should aid in the design of additional studies and the future development of FOXO proteins as therapeutic targets.

Long-term exposure of immortalized keratinocytes to arsenic induces EMT, impairs differentiation in organotypic skin models and mimics aspects of human skin derangements

Arsenic is one of the most important human carcinogens and environmental pollutants. However, the evaluation of the underlying carcinogenic mechanisms is challenging due to the lack of suitable in vivo and in vitro models, as distinct interspecies differences in arsenic metabolism exist. Thus, it is of high interest to develop new experimental models of arsenic-induced skin tumorigenesis in humans. Consequently, aim of this study was to establish an advanced 3D model for the investigation of arsenic-induced skin derangements, namely skin equivalents, built from immortalized human keratinocytes (NHEK/SVTERT3-5). In contrast to spontaneously immortalized HACAT cells, NHEK/SVTERT3-5 cells more closely resembled the differentiation pattern of primary keratinocytes. With regard to arsenic, our results showed that while our new cell model was widely unaffected by short-time treatment (72 h) with low, non-toxic doses of ATO (0.05-0.25 µM), chronic exposure (6 months) resulted in distinct changes of several cell characteristics. Thus, we observed an increase in the G2 fraction of the cell cycle accompanied by increased nucleus size and uneven tubulin distribution. Moreover, cells showed strong signs of de-differentiation and upregulation of several epithelial-to-mesenchymal transition markers. In line with these effects, chronic contact to arsenic resulted in impaired skin-forming capacities as well as localization of ki67-positive (proliferating) cells at the upper layers of the epidermis; a condition termed Bowen's disease. Finally, chronically arsenic-exposed cells were characterized by an increased tumorigenicity in SCID mice. Taken together, our study presents a new model system for the investigation of mechanisms underlying the tumor-promoting effects of chronic arsenic exposure.

Chronic arsenic trioxide exposure leads to enhanced aggressiveness via Met oncogene addiction in cancer cells

As an environmental poison, arsenic is responsible for many cancer deaths. Paradoxically, arsenic trioxide (ATO) presents also a powerful therapy used to treat refractory acute promyelocytic leukemia (APL) and is intensively investigated for treatment of other cancer types. Noteworthy, cancer therapy is frequently hampered by drug resistance, which is also often associated with enhancement of tumor aggressiveness. In this study, we analyzed ATO-selected cancer cells (A2780ATO) for the mechanisms underlying their enhanced tumorigenicity and aggressiveness. These cells were characterized by enhanced proliferation and spheroid growth as well as increased tumorigenicity of xenografts in SCID mice. Noteworthy, subsequent studies revealed that overexpression of Met receptor was the underlying oncogenic driver of these effects, as A2780ATO cells were characterized by collateral sensitivity against Met inhibitors. This finding was also confirmed by array comparative genomic hybridization (array CGH) and whole genome gene expression arrays, which revealed that Met overexpression by chronic ATO exposure was based on the transcriptional regulation via activation of AP-1. Finally, it was shown that treatment with the Met inhibitor crizotinib was also effective against A2780ATO cell xenografts in vivo, indicating that targeting of Met presents a promising strategy for the treatment of Met-overexpressing tumors after either arsenic exposure or failure to ATO treatment.

Integration of microRNAome, proteomics and metabolomics to analyze arsenic-induced malignant cell transformation

Long-term exposure to arsenic has been linked to tumorigenesis in different organs and tissues, such as skin; however, the detailed mechanism remains unclear. In this present study, we integrated “omics” including microRNAome, proteomics and metabolomics to investigate the potential molecular mechanisms. Compared with non-malignant human keratinocytes (HaCaT), twenty-six miRNAs were significantly altered in arsenic-induced transformed cells. Among these miRNAs, the differential expression of six miRNAs was confirmed using Q-RT-PCR, representing potential oxidative stress genes. Two-dimensional gel electrophoresis (2D-PAGE) and mass spectrometry (MS) were performed to identify the differential expression of proteins in arsenic-induced transformed cells, and twelve proteins were significantly changed. Several proteins were associated with oxidative stress and carcinogenesis including heat shock protein beta-1 (HSPB1), peroxiredoxin-2 (PRDX2). Using ultra-performance liquid chromatography and Q-TOF mass spectrometry (UPLC/Q-TOF MS), 68 metabolites including glutathione, fumaric acid, citric acid, phenylalanine, and tyrosine, related to redox metabolism, glutathione metabolism, citrate cycle, met cycle, phenylalanine and tyrosine metabolism were identified and quantified. Taken together, these results indicated that arsenic-induced transformed cells exhibit alterations in miRNA, protein and metabolite profiles providing novel insights into arsenic-induced cell malignant transformation and identifying early potential biomarkers for cutaneous squamous cell carcinoma induced by arsenic.

Silencing of TGIF attenuates the tumorigenicity of A549 cells in vitro and in vivo

The aim of this study was to investigate the effects of the silencing of the TG-interacting factor (TGIF) on the tumorigenicity of A549 cells in vitro and in vivo. Stable TGIF-silenced A549 cells were established by infecting shRNA lentiviral particles. Western blotting analysis was used to detect the expression of proteins. Cell cycle was detected by flow cytometry. Soft agar assay and tumor formation assay in nude mice were applied. The silencing of TGIF inhibited A549 cell proliferation, colony formation in vitro, growth of tumor xenograft in vivo, and arrested the cell cycle in the G1 phase. The expression of CDK4, cyclin D1, and phospho-Rb was markedly decreased in the A549-shTGIF cells compared with the A549-shcon cells, and p21 was markedly increased in the A549-shTGIF cells compared with the A549-shcon cells. A lower level of β-Catenin protein expression was observed in the A549-shTGIF cells than that in the A549-shcon cells. The silencing of TGIF attenuates the tumorigenicity of A549 cells in vitro and in vivo.

Elevated expression of TGIF is involved in lung carcinogenesis

The purpose of this study was to explore the expression of TG-interacting factor (TGIF) in lung carcinogenesis. Malignant transformation of human bronchial epithelial (16HBE) cell was established by benzo(a)pyrene (BaP) treatment. Soft agar assay and tumor formation assay in nude mice were applied. Tumorigenesis experiment in vivo was done by BaP treatment. Western blotting, immunohistochemistry, and quantitative polymerase chain reaction were used to detect TGIF expression. We observed a higher level of TGIF messenger RNA (mRNA) in lung cancer tissues than that in paracancerous tissues. We observed significantly higher levels of TGIF mRNA and protein in A549 and H1299 cell lines than that in 16HBE cell. Increased expressions of TGIF protein and mRNA were observed in 16HBE cells induced by BaP treatment as compared to those in solvent control group. We observed significantly higher levels of TGIF mRNA and protein in 16HBE-BaP cells than that in 16HBE-control cells. We observed significantly higher levels of TGIF mRNA and protein in mice lung tissues treated with BaP than that in control group. Our results suggested that elevated expression of TGIF was involved in lung carcinogenesis.