Chronic cadmium exposure aggravates malignant phenotypes of nasopharyngeal carcinoma by activating the Wnt/β-catenin signaling pathway via hypermethylation of the casein kinase 1α promoter

Mechanisms of Heavy Metal Cadmium (Cd)-Induced Malignancy

The environmental pollution of cadmium is worsening, and its significant carcinogenic effects on humans have been confirmed. Cadmium can induce cancer through various signaling pathways, including the ERK/JNK/p38MAPK, PI3K/AKT/mTOR, NF-κB, and Wnt. It can also cause cancer by directly damaging DNA and inhibiting DNA repair systems, or through epigenetic mechanisms such as abnormal DNA methylation, LncRNA, and microRNA. However, the detailed mechanisms of Cd-induced cancer are still not fully understood and require further investigation.

The dynamic face of cadmium-induced Carcinogenesis: Mechanisms, emerging trends, and future directions

Cadmium (Cd) is a malleable element with odorless, tasteless characteristics that occurs naturally in the earth's crust, underground water, and soil. The most common reasons for the anthropological release of Cd to the environment include industrial metal mining, smelting, battery manufacturing, fertilizer production, and cigarette smoking. Cadmium-containing products may enter the environment as soluble salts, vapor, or particle forms that accumulate in food, soil, water, and air. Several epidemiological studies have highlighted the association between Cd exposure and adverse health outcomes, especially renal toxicity, and the impact of Cd exposure on the development and progression of carcinogenesis. Also highlighted is the evidence for early-life and even maternal exposure to Cd leading to devastating health outcomes, especially the risk of cancer development in adulthood. Several mechanisms have been proposed to explain how Cd mediates carcinogenic transformation, including epigenetic alteration, DNA methylation, histone posttranslational modification, dysregulated non-coding RNA, DNA damage in the form of DNA mutation, strand breaks, and chromosomal abnormalities with double-strand break representing the most common DNA form of damage. Cd induces an indirect genotoxic effect by reducing p53's DNA binding activity, eventually impairing DNA repair, inducing downregulation in the expression of DNA repair genes, which might result in carcinogenic transformation, enhancing lipid peroxidation or evasion of antioxidant interference such as catalase, superoxide dismutase, and glutathione. Moreover, Cd mediates apoptosis evasion, autophagy activation, and survival mechanisms. In this review, we decipher the role of Cd mediating carcinogenic transformation in different models and highlight the interaction between various mechanisms. We also discuss diagnostic markers, therapeutic interventions, and future perspectives.

SETD1A promotes the proliferation and glycolysis of nasopharyngeal carcinoma cells by activating the PI3K/Akt pathway

Nasopharyngeal carcinoma is one of the common malignant tumors that the pathogenesis has not yet been completely defined. SETD1A (histone lysine methyltransferase SET domain-containing 1A) is related to the occurrence of various cancers. However, the role of SETD1A in nasopharyngeal carcinoma remains unclear. The SETD1A overexpression vector, si-NC, si-SETD1A#1, and si-SETD1A#2 were transfected into nasopharyngeal carcinoma cells to overexpress or knockdown SETD1A expression. The assay of biofunction was used to explore the role of SETD1A in nasopharyngeal carcinoma cells. The assay of glucose uptake, lactate release, ATP level, western blot, cell proliferation, and cellular apoptosis analysis were performed to investigate the potential mechanism of SETD1A regulation in nasopharyngeal carcinoma. This study was the first to show that SETD1A was upregulated in nasopharyngeal carcinoma cells and the overexpression of SETD1A significantly promoted the cell proliferation and glycolysis and suppressed the cellular apoptosis. Moreover, SETD1A enhances aerobic glycolysis and cell biological function of nasopharyngeal carcinoma cells via PI3K/AKT signaling pathway. SETD1A induced PI3K/AKT activation and subsequently prevented cellular apoptosis. In conclusion, this study identified overexpressed SETD1A as a positive regulator of proliferation that induced nasopharyngeal carcinoma cells’ aerobic glycolysis via PI3K/AKT signaling activation in vitro. This study laid a strong foundation for unveiling the precise anticancer mechanism of SETD1A. The SETD1A may become a novel biomarker for further inhibitor design to obstruct the PI3K/AKT-dependent nasopharyngeal carcinoma progression.

ECRG4 acts as a tumor suppressor in nasopharyngeal carcinoma by suppressing the AKT/GSK3β/β-catenin signaling pathway

Nasopharyngeal carcinoma (NPC) is a malignant tumor with a poor prognosis. Studies have shown that esophageal carcinoma related gene 4 (ECRG4) is hypermethylated and significantly downregulated in NPC tissues. However, the role of ECRG4 in NPC, and in particular the underlying molecular mechanism, is largely unclear. In this study, using immunohistochemical staining of ECRG4 in NPC and normal specimens, we confirmed that ECRG4 was downregulated in human NPC tissues. In addition, various biological and molecular studies were carried out and the results showed that ECRG4 exerted anticancer effect in NPC, including inhibiting cell growth, migration, and invasion of NPC cells in vitro. Moreover, restoring ECRG4 expression suppressed the in vivo tumorigenesis of CNE2 cells. ECRG4 inhibited AKT/GSK3β/β-catenin signaling, as well as the downstream targets of β-catenin. LiCl treatment, which reduced GSK3β phosphorylation and upregulated β-catenin expression, restored the invasive ability of ECRG4-overexpressing NPC cells. Furthermore, we showed that the DNA methylation inhibitor 5-aza-dC reduced ECRG4 methylation and the invasive ability of negative control cells, but not that of ECRG4-overexpressing cells, suggesting that the inhibitory effect of 5-aza-dC depends on low expression of ECRG4. Collectively, our results demonstrated that ECRG4 downregulation contributed to NPC growth and invasion by activating AKT/GSK3β/β-catenin signaling pathway. ECRG4 could be a promising therapeutic target for the treatment of NPC.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10616-022-00520-8.

Environmental Cadmium Exposure Promotes the Development, Progression and Chemoradioresistance of Esophageal Squamous Cell Carcinoma

Cadmium (Cd) exposure has been implicated in the etiology of esophageal squamous cell carcinoma (ESCC), albeit with inconsistent results from epidemiologic studies and without causal evidence. In this study, we explore the relationship of Cd exposure and the development, progression and therapeutic resistance of ESCC. A total of 150 ESCC patients and 177 matched controls from a coastal region with a high incidence of ESCC in China were included in the study. It was found that the median blood Cd level (BCL) was significantly higher in ESCC patients than that in the controls. Odds ratios for ESCC risk were 3.12 (95% CI 1.54-6.30) and 3.71 (95% CI 1.84-7.48) in the third and fourth quartiles of Cd distribution, respectively. Notably, BCL above 4.71 μg/L was strongly associated with shorter progression-free survival time compared to that below 1.60 μg/L (p < 0.001). The chronic Cd-treated ESCC cells (CCT-ESCC) CCT-EC109 and CCT-EC9706 exhibited increased cell proliferation and tumorigenesis, enhanced migration and invasion, and upregulated EMT biomarkers following 12 weeks of exposure to 5 μM cadmium chloride. Furthermore, Cd treatment attenuated the efficacy of 5-fluorouracil, cisplatin and irradiation treatment in CCT-ESCC cells both in vitro and in vivo. Moreover, we revealed that Cd stimulated the cancer cell stemness and Wnt/β-catenin signaling pathway in the CCT-ESCC cells. Additionally, 5-aza-2-deoxy-cytidine treatment resulted in suppression of the Wnt/β-catenin signaling pathway and rescue of the Cd-induced cell radioresistance. These results offer new insights into the role of environmental Cd exposure in the development, progression and chemoradioresistance of ESCC.

Exposure to cadmium and head and neck cancers: a meta-analysis of observational studies

Cadmium (Cd) is a widespread environmental pollutant. A number of observational studies have reported that Cd might be a cause of nasopharyngeal (NPC), pharyngeal (PC), or laryngeal cancers (LC). In this study evidence about the relation of Cd and NPC, PC, and LC has been summarized. A literature review was conducted until 20 June 2020 in PubMed, Ovid, Scopus, Web of Science and Google scholar databases to investigate the epidemiologic evidence for the relation between cadmium exposure and cancers of the nasopharynx, pharynx, and larynx. Ten articles were selected after careful screening of retrieved studies. All of these studies obtained a Newcastle-Ottawa Scale (NOS) quality score from 6 to 8. Due to high heterogeneity, in all analyses, random effect was used. The pooled results showed that cadmium levels in NPC (standard mean difference (SMD=0.55; 95% CI=0.20, 0.89; p=0.002) and PC (SMD=9.79; 95% CI=0.62, 18.96; p=0.036) patients/tissues were significantly higher than their controls. But cadmium levels were not significantly different between LC cases/tissues and their controls. (SMD=-0.05; 95% CI=-0.99, 0.89; p=0.921). Exposure to cadmium is likely to cause nasopharyngeal and pharyngeal cancer.

Multiomics Landscape Uncovers the Molecular Mechanism of the Malignant Evolution of Lung Adenocarcinoma Cells to Chronic Low Dose Cadmium Exposure

Cadmium (Cd) from cigarette smoke and polluted air can lead to lung adenocarcinoma after long-term inhalation. However, most studies are based on short-term exposure to this toxic metal at high concentrations. Here, we investigate the effects of long-term exposure of A549 cells (lung adenocarcinoma) to cadmium at low concentrations using morphological and multiomics analyses. First, we treated A549 cells continuously with CdCl2 at 1μM for 8 months and found that CdCl2 promoted cellular migration and invasion. After that, we applied transmission electron and fluorescence microscopies and did not observe significant morphological changes in Golgi apparatus, endoplasmic reticulum, lysosomes, or mitochondria on Cd treated cells; microfilaments, in contrast, accumulated in lamellipodium and adhesion plaques, which suggested that Cd enhanced cellular activity. Second, by using whole-exome sequencing (WES) we detected 4222 unique SNPs in Cd-treated cells, which included 382 unique non-synonymous mutation sites. The corresponding mutated genes, after GO and KEGG enrichments, were involved mainly in cell adhesion, movement, and metabolic pathways. Third, by RNA-seq analysis, we showed that 1250 genes (784 up and 466 down), 1623 mRNAs (1023 up and 591 down), and 679 lncRNAs (375 up and 304 down) were expressed differently. Furthermore, GO enrichment of these RNA-seq results suggested that most differentially expressed genes were related to cell adhesion and organization of the extracellular matrix in biological process terms; KEGG enrichment revealed that the differentially expressed genes took part in 26 pathways, among which the metabolic pathway was the most significant. These findings could be important for unveiling mechanisms of Cd-related cancers and for developing cancer therapies in the future.

Cadmium-Associated Molecular Signatures in Cancer Cell Models

The exposure of cancer cells to cadmium and its compounds is often associated with the development of more malignant phenotypes, thereby contributing to the acceleration of tumor progression. It is known that cadmium is a transcriptional regulator that induces molecular reprogramming, and therefore the study of differentially expressed genes has enabled the identification and classification of molecular signatures inherent in human neoplastic cells upon cadmium exposure as useful biomarkers that are potentially transferable to clinical research. This review recapitulates selected studies that report the detection of cadmium-associated signatures in breast, gastric, colon, liver, lung, and nasopharyngeal tumor cell models, as specifically demonstrated by individual gene or whole genome expression profiling. Where available, the molecular, biochemical, and/or physiological aspects associated with the targeted gene activation or silencing in the discussed cell models are also outlined.

Epimutational effects of electronic cigarettes

Electronic cigarettes (e-cigarettes), since they do not require tobacco combustion, have traditionally been considered less harmful than conventional cigarettes (c-cigarettes). In recent years, however, researchers have found many toxic compounds in the aerosols of e-cigarettes, and numerous studies have shown that e-cigarettes can adversely affect the human epigenome. In this review, we provide an update on recent findings regarding epigenetic outcomes of e-cigarette aerosols. Moreover, we discussed the effects of several typical e-cigarette ingredients (nicotine, tobacco-specific nitrosamines, volatile organic compounds, carbonyl compounds, and toxic metals) on DNA methylation, histone modifications, and noncoding RNA expression. These epigenetic effects could explain some of the diseases caused by e-cigarettes. It also reminds the public that like c-cigarettes, inhaling e-cigarette aerosols could also be accompanied with potential epigenotoxicity on the human body.

Chronic Exposure to Cadmium Induces Differential Methylation in Mice Spermatozoa

Cadmium exposure is ubiquitous and has been linked to diseases including cancers and reproductive defects. Since cadmium is nonmutagenic, it is thought to exert its gene dysregulatory effects through epigenetic reprogramming. Several studies have implicated germline exposure to cadmium in developmental reprogramming. However, most of these studies have focused on maternal exposure, while the impact on sperm fertility and disease susceptibility has received less attention. In this study, we used reduced representation bisulfite sequencing to comprehensively investigate the impact of chronic cadmium exposure on mouse spermatozoa DNA methylation. Adult male C57BL/J6 mice were provided water with or without cadmium chloride for 9 weeks. Sperm, testes, liver, and kidney tissues were collected at the end of the treatment period. Cadmium exposure was confirmed through gene expression analysis of metallothionein-1 and 2, 2 well-known cadmium-induced genes. Analysis of sperm DNA methylation changes revealed 1788 differentially methylated sites present at regulatory regions in sperm of mice exposed to cadmium compared with vehicle (control) mice. Furthermore, most of these differential methylation changes positively correlated with changes in gene expression at both the transcription initiation stage as well as the splicing levels. Interestingly, the genes targeted by cadmium exposure are involved in several critical developmental processes. Our results present a comprehensive analysis of the sperm methylome in response to chronic cadmium exposure. These data, therefore, highlight a foundational framework to study gene expression patterns that may affect fertility in the exposed individual as well as their offspring, through paternal inheritance.

Wnt pathway: A mechanism worth considering in endocrine disrupting chemical action

Endocrine disrupting chemicals (EDCs) are defined as exogenous substances that can alter the development and functioning of the endocrine system. The Wnt signaling pathway is an evolutionarily conserved pathway consisting of proteins that transmit cell-to-cell receptors through cell surface receptors, regulating important aspects of cell migration, polarity, neural formation, and organogenesis, which determines the fate of the cell during embryonic development. Although the effects of EDCs have been studied in terms of many molecular mechanisms; because of its critical role in embryogenesis, the Wnt pathway is of special interest in EDC exposure. This review provides information about the effects of EDC exposure on the Wnt/β-catenin pathway focusing on studies on bisphenol A, di-(2-ethylhexyl) phthalate, diethylstilbestrol, cadmium, and 2,3,7,8-tetrachlorodibenzo-p-dioxin.

Glucose and lipid lowering effects of Enhydra fluctuans extract in cadmium treated normal and type-2 diabetic model rats

BACKGROUND

Recent epidemiological and experimental studies suggest that cadmium and diabetes-related hyperglycemia may act synergistically to worsen metabolic regulation. The present study aims to evaluate the potential effects of Enhydra fluctuans extract in diabetes and dyslipidemia in cadmium (CdCl₂) induced- normal and type 2 diabetic model rats.

METHOD

Forty-eight Long-Evans rats were divided equally into the following six groups: Normal Control (N-C), Normal treated with CdCl₂ (N-Cd), Normal treated with plant extract (N-P), Normal treated with both plant extract and CdCl₂ (N-PCd), Diabetic treated with plant extract (DM-P) and Diabetic treated with both plant extract and CdCl2 (DM-PCd). Blood glucose and other biochemical parameters were estimated by the enzymatic colorimetric method. Histological analysis of liver and heart was done by the hematoxylin-eosin (H & E) method.

RESULTS

Twenty-one days treatment of E. fluctuans extracts at a dose of 200 mg/kg significantly reduced blood glucose level in N-PCd and DM-PCd (p < 0.05), and DM-P (p < 0.01) group. The plant extract had no direct effects on total blood lipids but, it had beneficial effects on TG/HDL-C ratio in N-P and DM-PCd groups (p < 0.05). Cd induction significantly reduced body weight [(N-Cd, N-PCd, DM-PCd) (p < 0.01)], and induced liver [N-Cd (p < 0.05), N-PCd, p < 0.001] and renal impairment [N-Cd (p < 0.05)]. In bi-variate association, a significant positive correlation between serum glucose and SGPT (p < 0.05) as well as SGPT and TG/HDL ratio (p = 0.019) was found in DM-P and in the merged group. The histology of liver and heart showed severe damages including inflammation, nuclear pyknosis, loss of myocardial fibers, necrosis and fibrosis in the Cd treated groups compared to plant treated groups.

CONCLUSION

E. fluctuans seems to have potent antihyperglycemic effects in diabetes and Cd toxicity along with partial antidyslipidemic properties in euglycemic and diabetic rats. Our study suggests a novel oral antihyperglycemic agent in the present environmental context.

Cadmium exposure upregulates SNAIL through miR-30 repression in human lung epithelial cells

Cadmium (Cd) is a known human lung carcinogen. In addition, Cd exposure is associated with several lung diseases including emphysema, chronic obstructive pulmonary disease (COPD), asthma and fibrosis. Although earlier studies have identified several processes dysregulated by Cd exposure, the underlying mechanisms remain unclear. Here, we examined the transcriptome of lung epithelial cells exposed to Cd to understand the molecular basis of Cd-induced diseases. Computational analysis of the transcriptome predicted a significant number of Cd-upregulated genes to be targets of miR-30 family miRNAs. Experimental validation showed downregulation of all the miR-30 family members in Cd exposed cells. We found SNAIL, an EMT master regulator, to be the most upregulated among the miR-30 targets. Furthermore, we found decrease in the levels of epithelial marker E- cadherin (CDH1) and increase in the levels of mesenchymal markers, ZEB1 and vimentin. This suggested induction of EMT in Cd exposed cells. Luciferase reporter assays showed that miR-30 repressed SNAIL by directly targeting its 3' UTR. Over expression of miR-30e and transfection of miR-30e mimics reduced Cd-induced SNAIL upregulation. Our results suggest that miR-30 negatively regulates SNAIL in lung epithelial cells and that Cd-induced downregulation of miR-30 relieves this repression, resulting in SNAIL upregulation and EMT induction. EMT plays a major role in many diseases associated with Cd exposure including fibrosis, COPD, and cancer and metastasis. Therefore, our identification of miR-30 downregulation in Cd exposed cells and the consequent activation of SNAIL provides important mechanistic insights into lung diseases associated with Cd exposure.