Nickel chloride regulates ANGPTL4 via the HIF-1α-mediated TET1 expression in lung cells

Exposure to nickel chloride induces epigenetic modification on detoxification enzyme glutathione S-transferase M2

Nickel (Ni) is a human carcinogen with genotoxic and epigenotoxic effects. Environmental and occupational exposure to Ni increases the risk of cancer and chronic inflammatory diseases. Our previous findings indicate that Ni alters gene expression through epigenetic regulation, specifically impacting E-cadherin and angiopoietin-like 4 (ANGPTL4), involved in epithelial-mesenchymal transition and migration. GST-M2, a member of the glutathione S-transferase (GST) enzyme family, plays a crucial role in cellular defense against oxidative damage and has been increasingly associated with cancer. GST-M2 overexpression inhibits lung cancer invasion and metastasis in vitro and in vivo. Hypermethylation of its promoter in cancer cells reduces gene expression, correlating with poor prognosis in non-small-cell lung cancer patients. The impact of Ni on GST-M2 remains unclear. We will investigate whether nickel exerts regulatory effects on GST-M2 through epigenetic modifications. Additionally, metformin, an antidiabetic drug, is being studied as a chemopreventive agent against nickel-induced damage. Our findings indicate that nickel chloride (NiCl2 ) exposure, both short-term and long-term, represses GST-M2 expression. However, the expression can be restored by demethylation agent 5-aza-2'-deoxycytidine and metformin. NiCl2 promotes hypermethylation of the GST-M2 promoter, as confirmed by methylation-specific PCR and bisulfite sequencing. Additionally, NiCl2 also influences histone acetylation, and metformin counteracts the suppressive effect of NiCl2 on histone H3 expression. Metformin reestablishes the binding of specificity protein 1 to the GST-M2 promoter, which is otherwise disrupted by NiCl2 . These findings elucidate the mechanism by which Ni reduces GST-M2 expression and transcriptional activity, potentially contributing to Ni-induced lung carcinogenesis.

Sp1-activated FGFR2 is involved in early-life exposure to nickel-induced craniosynostosis by regulating the ERK1/2 signaling pathway

Nickel, a common environmental hazard, is a risk factor for craniosynostosis. However, the underlying biological mechanism remains unclear. Here, we found that early-life nickel exposure induced craniosynostosis in mice. In vitro, nickel promoted the osteogenic differentiation of human mesenchymal stem cells (hMSCs), and its osteogenic ability in vivo was confirmed by an ectopic osteogenesis model. Further mRNA sequencing showed that ERK1/2 signaling and FGFR2 were aberrantly activated. FGFR2 was identified as a key regulator of ERK1/2 signaling. By promoter methylation prediction and methylation-specific PCR (MSP) assays, we found that nickel induced hypomethylation in the promoter of FGFR2, which increased its binding affinity to the transcription factor Sp1. During pregnancy and postnatal stages, AZD4547 rescued nickel-induced craniosynostosis by inhibiting FGFR2 and ERK1/2. Compared with normal individuals, nickel levels were increased in the serum of individuals with craniosynostosis. Further logistic and RCS analyses showed that nickel was an independent risk factor for craniosynostosis with a nonlinear correlation. Mediated analysis showed that FGFR2 mediated 30.13% of the association between nickel and craniosynostosis risk. Collectively, we demonstrate that early-life nickel exposure triggers the hypomethylation of FGFR2 and its binding to Sp1, thereby promoting the osteogenic differentiation of hMSCs by ERK1/2 signaling, leading to craniosynostosis.

Nickel chloride promotes lung cancer invasion and metastasis by up-regulating the expression of E3 ubiquitin ligase TRIM31 through the IL-6/STAT3 signaling axis

Nickel compounds are widely used in industries and daily life as important industrial products. Long-term exposure to nickel compounds has been associated with increased incidence and poor prognosis of lung cancer. However, the molecular mechanism by which exposure to nickel compounds induces the malignant phenotype of lung cancer cells remains unclear. In this study, we confirmed that nickel chloride (NiCl2) exposure promotes invasion and metastasis through IL-6/STAT3 both in vitro and vivo. Mechanistically, we found that NiCl2 mediated the transcriptional regulation of E3 ubiquitin ligase TRIM31 by SATAT3 phosphorylation, and promoted its up-regulation. Overexpression TRIM31 is an independent risk factor for lung cancer patients, and it promotes the invasion and metastasis of lung cancer cells. In addition, E3 ubiquitination ligase TRIM31 binds to its substrate TP53 protein in the RING region and accelerates TP53 protein ubiquitination and degradation. Functional recovery experiments showed that NiCl2 exposure promotes the invasion and metastasis ability of lung cancer and ubiquitination-mediated degradation of TP53 protein through the STAT3/TRIM31 axis. These findings reveal the role and mechanism of NiCl2 in lung cancer progression, indicating that STAT3 and TRIM31 may be promising targets for the treatment of lung cancer.

Hypoxia inducible factor-1α (HIF-1α) in breast cancer: The crosstalk with oncogenic and onco-suppressor factors in regulation of cancer hallmarks

Low oxygen level at tumor microenvironment leads to a condition, known as hypoxia that is implicated in cancer progression. Upon hypoxia, HIF-1α undergoes activation and due to its oncogenic function and interaction with other molecular pathways, promotes tumor progression. The HIF-1α role in regulating breast cancer progression is described, Overall, HIF-1α has upregulation in breast tumor and due to its tumor-promoting function, its upregulation is in favor of breast tumor progression. HIF-1α overexpression prevents apoptosis in breast tumor and it promotes cell cycle progression. Silencing HIF-1α triggers cycle arrest and decreases growth. Migration of breast tumor enhances by HIF-1α signaling and it mainly induces EMT in providing metastasis. HIF-1α upregulation stimulates drug resistance and radio-resistance in breast tumor. Furthermore, HIF-1α signaling induces immune evasion of breast cancer. Berberine and pharmacological intervention suppress HIF-1α signaling in breast tumor and regulation of HIF-1α by non-coding RNAs occurs. Furthermore, HIF-1α is a biomarker in clinic.

The role of hypoxia-inducible factor 1 alpha (HIF-1α) modulation in heavy metal toxicity

Hypoxia-inducible factor 1 (HIF-1) is an oxygen-sensing transcriptional regulator orchestrating a complex of adaptive cellular responses to hypoxia. Several studies have demonstrated that toxic metal exposure may also modulate HIF-1α signal transduction pathway, although the existing data are scarce. Therefore, the present review aims to summarize the existing data on the effects of toxic metals on HIF-1 signaling and the potential underlying mechanisms with a special focus on prooxidant effect of the metals. The particular effect of metals was shown to be dependent on cell type, varying from down- to up-regulation of HIF-1 pathway. Inhibition of HIF-1 signaling may contribute to impaired hypoxic tolerance and adaptation, thus promoting hypoxic damage in the cells. In contrast, its metal-induced activation may result in increased tolerance to hypoxia through increased angiogenesis, thus promoting tumor growth and contributing to carcinogenic effect of heavy metals. Up-regulation of HIF-1 signaling is mainly observed upon Cr, As, and Ni exposure, whereas Cd and Hg may both stimulate and inhibit HIF-1 pathway. The mechanisms underlying the influence of toxic metal exposure on HIF-1 signaling involve modulation of prolyl hydroxylases (PHD2) activity, as well as interference with other tightly related pathways including Nrf2, PI3K/Akt, NF-κB, and MAPK signaling. These effects are at least partially mediated by metal-induced ROS generation. Hypothetically, maintenance of adequate HIF-1 signaling upon toxic metal exposure through direct (PHD2 modulation) or indirect (antioxidant) mechanisms may provide an additional strategy for prevention of adverse effects of metal toxicity.

Epigenetic Regulation in Chromium-, Nickel- and Cadmium-Induced Carcinogenesis

Environmental and occupational exposure to heavy metals, such as hexavalent chromium, nickel, and cadmium, are major health concerns worldwide. Some heavy metals are well-documented human carcinogens. Multiple mechanisms, including DNA damage, dysregulated gene expression, and aberrant cancer-related signaling, have been shown to contribute to metal-induced carcinogenesis. However, the molecular mechanisms accounting for heavy metal-induced carcinogenesis and angiogenesis are still not fully understood. In recent years, an increasing number of studies have indicated that in addition to genotoxicity and genetic mutations, epigenetic mechanisms play critical roles in metal-induced cancers. Epigenetics refers to the reversible modification of genomes without changing DNA sequences; epigenetic modifications generally involve DNA methylation, histone modification, chromatin remodeling, and non-coding RNAs. Epigenetic regulation is essential for maintaining normal gene expression patterns; the disruption of epigenetic modifications may lead to altered cellular function and even malignant transformation. Therefore, aberrant epigenetic modifications are widely involved in metal-induced cancer formation, development, and angiogenesis. Notably, the role of epigenetic mechanisms in heavy metal-induced carcinogenesis and angiogenesis remains largely unknown, and further studies are urgently required. In this review, we highlight the current advances in understanding the roles of epigenetic mechanisms in heavy metal-induced carcinogenesis, cancer progression, and angiogenesis.

Prognostic Significance of ANGPTL4 in Lung Adenocarcinoma: A Meta-Analysis Based on Integrated TCGA and GEO Databases

Lung adenocarcinoma (LUAD) is a common malignant tumor with a poor prognosis. Recent studies have found that angiopoietin-like 4 (ANGPTL4) is abnormally expressed in many tumors, so it can serve as a potential prognostic marker and therapeutic target. However, its prognostic value in LUAD remains unclear. We downloaded RNA sequence data for LUAD from The Cancer Genome Atlas (TCGA) database, methylation data from the University of California Santa Cruz genome database, and clinical information. R software (version 4.1.1) was applied to analyze the ANGPTL4 expression in LUAD and nontumor samples, and the correlation with clinical characteristics to assess its prognostic and diagnostic value. In addition, we analyzed the relationship between the ANGPTL4 expression and methylation levels. Tumor IMmune Estimation Resource (TIMER) tool was taken for immune infiltration analysis, and two Gene Expression Omnibus (GEO) datasets were combined for meta-analysis. Finally, differentially expressed genes (DEGs) related to ANGPTL4 were analyzed to clarify its function. As shown in our results, ANGPTL4 was upregulated in LUAD and was an independent risk factor for the diagnosis and prognosis of LUAD. The general methylation level and eight ANGPTL4 methylation sites were significantly negatively correlated with the ANGPTL4 expression. Furthermore, we found that B cell infiltration was negatively correlated with ANGPTL4 expression and was an independent risk factor. Meta-analysis showed that the high expression of ANGPTL4 was closely associated with a poor prognosis. 153 DEGs, including the matrix metalloproteinase family, the chemokines subfamily, and the collagen family, were correlated with ANGPTL4. In this study, we found that ANGPTL4 was significantly elevated in LUAD and was closely associated with the development and poor prognosis of LUAD, suggesting that ANGPTL4 may be a prognostic biomarker and a potential therapeutic target for LUAD.