Suppression of miR-143 contributes to overexpression of IL-6, HIF-1α and NF-κB p65 in Cr(VI)-induced human exposure and tumor growth

DNA-Assisted CRISPR-Cas12a Enhanced Fluorescent Assay for Protein Detection in Complicated Matrices

Proteins are important biological macromolecules that perform a wide variety of functions in the cell and human body, and can serve as important biomarkers for early diagnosis and prognosis of human diseases as well as monitoring the effectiveness of disease treatment. Hence, sensitive and accurate detection of proteins in human biospecimens is imperative. However, at present, there is no ideal method available for the detection of proteins in clinical samples, many of which are present at ultralow (less than 1 pM) concentrations and in complicated matrices. Herein, we report an ultrasensitive and selective DNA-assisted CRISPR-Cas12a enhanced fluorescent assay (DACEA) for protein detection with detection limits reaching as low as attomolar concentrations. The high assay sensitivity was accomplished through the combined DNA barcode amplification (by using dual-functionalized AuNPs) and CRISPR analysis, while the high selectivity and high resistance to the matrix effects of our method were accomplished via the formation of protein-antibody sandwich structure and the specific recognition of Cas12a (under the guidance of crRNA) toward the designed target ssDNA. Given its ability to accurately and sensitively detect trace amounts of proteins in complicated matrices, the DACEA protein assay platform pioneered in this work has a potential application in routine protein biomarker testing.

Hexavalent chromium induced metabolic reprogramming, carcinogenesis and tumor progression through PDK1 upregulation

Lung cancer is the leading factor of cancer-related death in the worldwide. Hexavalent chromium [Cr(VI)] is a potential carcinogen for inducing lung cancers. To understand new mechanism of Cr(VI)-induced tumorigenesis and cancer development, we identified that PDK1 expression levels were greatly increased in chromium-transformed cells (Cr-T) compared to the parental BEAS-2B (B2B) cells by proteomic profiling and Western blotting; PDK1 levels were also induced in lung cancer cell lines and in lung samples of mice exposed to Cr(VI). Cr(VI) increased Warburg effect, cell migration, proliferation and colony formation through PDK1 upregulation. To identify the mechanism of PDK1 induction, we performed miRNA-seq analysis of Cr-T and B2B cells, and found miR-493 levels was significantly suppressed by Cr(VI). PDK1 was induced by miR-493 suppression, and was a direct target of miR-493. Interestingly, we also found HIF-1α was directly targeting by miR-493 and was induced by miR-493 downregulation. HIF-1α expression levels were upregulated in lung samples of mice with Cr(VI)-exposure. PDK1 was induced by HIF-1α, showing miR-493 suppression can directly induce PDK1 as well as through HIF-1α induction. MiR-493 overexpression was sufficient to suppress tumor growth, PDK1 and HIF-1α expression in vivo. We also showed that levels of miR-493 suppression, HIF-1α and PDK1 elevations were strongly correlated with poor prognosis of lung cancer subjects. These results demonstrate both HIF-1α and PDK1 expression are induced by Cr(VI)-mediated miR-493 suppression, and MiR-493/HIF-1α/PDK1 axis is a new pathway in Cr(VI)-inducing carcinogenesis and tumor growth.

Human exposure to chromite mining pollution, the toxicity mechanism and health impact

Significant amounts of toxic metal-containing mining waste are produced by chromium mining activities, along with the production of air pollutants. The presence of toxic metals in various environmental media including air, water, and soil, along with their chemical species such as hexavalent chromium, pose major health hazards for both directly exposed mining workers and the population residing near the mining areas. Highlighting the requirements for enhanced environmental protection and safety measures, this comprehensive review shed light on the global environmental pollution stemming from chromite mining activities. Based on the published literature, the study also investigated into the pollution caused by toxic metals and explored their probable health effects on exposed individuals. The exposure routes and the mechanisms of toxic metal induced carcinogenicity in the exposed groups were assessed. Additionally, the generated reactive species in exposed individuals and the toxicity mechanisms of hexavalent chromium were discussed. Considering these findings, this review proposed the necessity of cross-sectional biomonitoring studies involving occupationally exposed workers from chromite mining operations. The anticipated impact of this review is to influence the global and national chromite mining industry, instigating improvements in occupational settings, real-time pollution monitoring, and healthcare provisions for exposed workers.

Hexavalent chromium exposure induces lung injury via activation of NLRP3 and AIM2 inflammasomes in rats

Hexavalent chromium (Cr(VI)) has been identified as a Class I human carcinogen, but its carcinogenic mechanism is currently unclear. There is still a lack of understanding of its associations with early pulmonary inflammatory damages. Inflammation is an important stage before the occurrence of tumors, and under the long-term stimulation of inflammation, it can promote the development of tumors. In this study, the aim is to explore the effect of Cr(VI) exposure on pulmonary inflammation and its relationship with the mechanism of inflammation cancer transformation. We established a Cr(VI) exposure model in SD rats using tracheal instillation of potassium dichromate solution, and collected samples at the time of cessation of exposure and 14 days after cessation of exposure. Analyzing the experimental results, it was found that the lung index increased after exposure to Cr(VI), promoting the occurrence of apoptosis in lung tissue cells and exacerbating lung tissue damage. The damage situation improved after exposure termination; Inductively coupled plasma mass (ICPRQ) spectrometer detection found that the exposed group had significantly increased levels of blood chromium, blood manganese, blood copper, blood arsenic, urine chromium, urine copper, and urine lead; After two weeks of repair, blood chromium and blood manganese levels were significantly lower than those in the same dose group of the exposure group, while blood copper levels were significantly higher than those in the same dose group of the exposure group. There was no significant difference in blood arsenic levels between the exposure group and the exposure group. Urine chromium and urine lead levels were significantly lower than those in the same dose group of the exposure group, while urine copper levels only increased. At the same time, it was found that Cr(VI) exposure caused disruption of oxidative stress levels in rat lung tissues. After 14-day exposure, Cr(VI) significantly decreased and oxidative stress levels significantly decreased. Further investigation revealed that Cr(VI) induces activation of inflammasomes NLRP3, AIM2, and their signaling pathways in lung inflammatory injuries, but this condition persists even after cessation of exposure. The study suggested that in hexavalent chromium induced lung tissue injuries in rats, NLRP3 and AIM2 inflammasomes and their signaling pathways activation. Furthermore, the characteristic of sustained activation after cessation of exposure was also indicated. These results provide new ideas and references for further elucidating the mechanisms of Cr(VI), lung inflammation and inflammation cancer transformation.

HDAC1 and FOXK1 mediate EGFR-TKI resistance of non-small cell lung cancer through miR-33a silencing

BACKGROUND

The development of acquired EGFR-TKI treatment resistance is still a major clinical challenge in the treatment of non-small cell lung cancer (NSCLC). This study aimed to investigate the role of HDAC1/FOXK1/miR-33a signaling in EGFR-TKI resistance.

METHODS

The expression levels of miR-33a, HDAC1, and FOXK1 were examined using quantitative polymerase chain reaction (PCR) and bioinformatics analysis. Cell proliferation, migration, and apoptosis were explored by cell number assay, Transwell, and flow cytometry assays, respectively. After overexpression or knockdown of HDAC1, miR-33a expression in the cells, cell functions were tested. Immunoprecipitation and correlation analyses were used to evaluate the interaction between HDAC1 and FOXK1 protein. The tumor-suppressive role of miR-33a was investigated by animal experiments.

RESULTS

The suppression of miR-33a increased TKI resistance by affecting cell proliferation, migration, and apoptosis in gefitinib-resistant cells. HDAC1 is the key upstream molecule that inhibits miR-33 expression. HDAC1 upregulation increased gefitinib resistance by its binding to FOXK1 in cells to silence miR-33a expression. MiR-33a overexpression exerts tumor-suppressive effects by negatively regulating ABCB7 and p70S6K1 expression. Moreover, overexpression of miR-33a inhibited tumor growth in a xenograft nude mouse model.

CONCLUSIONS

HDAC1/FOXK1 upregulation and miR-33a silencing are new mechanisms of EGFR-TKI resistance in NSCLC.

Regulation of the HIF switch in human endothelial and cancer cells

Hypoxia-inducible factors (HIFs) are transcription factors that reprogram the transcriptome for cells to survive hypoxic insults and oxidative stress. They are important during embryonic development and reprogram the cells to utilize glycolysis when the oxygen levels are extremely low. This metabolic change facilitates normal cell survival as well as cancer cell survival. The key feature in survival is the transition between acute hypoxia and chronic hypoxia, and this is regulated by the transition between HIF-1 expression and HIF-2/HIF-3 expression. This transition is observed in many human cancers and endothelial cells and referred to as the HIF Switch. Here we discuss the mechanisms involved in the HIF Switch in human endothelial and cancer cells which include mRNA and protein levels of the alpha chains of the HIFs. A major continuing effort in this field is directed towards determining the differences between normal and tumor cell utilization of this important pathway, and how this could lead to potential therapeutic approaches.

Transcriptomic analysis reveals particulate hexavalent chromium regulates key inflammatory pathways in human lung fibroblasts as a possible mechanism of carcinogenesis

Hexavalent chromium [Cr(VI)] is considered a major environmental health concern and lung carcinogen. However, the exact mechanism by which Cr(VI) causes lung cancer in humans remains unclear. Since several reports have demonstrated a role for inflammation in Cr(VI) toxicity, the present study aimed to apply transcriptomics to examine the global mRNA expression in human lung fibroblasts after acute (24 h) or prolonged (72 and 120 h) exposure to 0.1, 0.2 and 0.3 μg/cm2 zinc chromate, with a particular emphasis on inflammatory pathways. The results showed Cr(VI) affected the expression of multiple genes and these effects varied according to Cr(VI) concentration and exposure time. Bioinformatic analysis of RNA-Seq data based on the Gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and MetaCore databases revealed multiple inflammatory pathways were affected by Cr(VI) treatment. qRT-PCR data corroborated RNA-Seq findings. This study showed for the first time that Cr(VI) regulates key inflammatory pathways in human lung fibroblasts, providing novel insights into the mechanisms by which Cr(VI) causes lung cancer.

Fine particulate matter PM2.5 and its constituent, hexavalent chromium induce acute cytotoxicity in human airway epithelial cells via inflammasome-mediated pyroptosis

PM2.5-induced airway injury contributes to an increased rate of respiratory morbidity. However, the relationship between PM2.5 toxicants and acute cytotoxic effects remains poorly understood. This study aimed to investigate the mechanisms of PM2.5- and its constituent-induced cytotoxicity in human airway epithelial cells. Exposure to PM2.5 resulted in dose-dependent cytotoxicity within 24 h. Among the PM2.5 constituents examined, Cr(VI) at the dose found in PM2.5 exhibited cytotoxic effects. Both PM2.5 and Cr(VI) cause necrosis while also upregulating the expression of proinflammatory cytokine transcripts. Interestingly, exposure to the conditioned PM, obtained from adsorption in the Cr(VI)-reducing agents, FeSO4 and EDTA, showed a decrease in cytotoxicity. Furthermore, PM2.5 mechanistically enhances programmed pyroptosis through the activation of NLRP3/caspase-1/Gasdermin D pathway and increase of IL-1β. These pyroptosis markers were reduced when exposure to conditioned PM. These findings provide a deeper understanding of mechanisms underlying PM2.5 and Cr(VI) in acute airway toxicity.

Transition metals in angiogenesis - A narrative review

The aim of this paper is to offer a narrative review of the literature regarding the influence of transition metals on angiogenesis, excluding lanthanides and actinides. To our knowledge there are not any reviews up to date offering such a summary, which inclined us to write this paper. Angiogenesis describes the process of blood vessel formation, which is an essential requirement for human growth and development. When the complex interplay between pro- and antiangiogenic mediators falls out of balance, angiogenesis can quickly become harmful. As it is so fundamental, both its inhibition and enhancement take part in various diseases, making it a target for therapeutic treatments. Current methods come with limitations, therefore, novel agents are constantly being researched, with metal agents offering promising results. Various transition metals have already been investigated in-depth, with studies indicating both pro- and antiangiogenic properties, respectively. The transition metals are being applied in various formulations, such as nanoparticles, complexes, or scaffold materials. Albeit the increasing attention this field is receiving, there remain many unanswered questions, mostly regarding the molecular mechanisms behind the observed effects. Notably, approximately half of all the transition metals have not yet been investigated regarding potential angiogenic effects. Considering the promising results which have already been established, it should be of great interest to begin investigating the remaining elements whilst also further analyzing the established effects.

Dysregulation of MiR-199a/IL8 pathway in chronic Cr (VI)-induced tumor growth and angiogenesis

Hexavalent chromium [Cr(VI)] is a well-known environmental carcinogen. Recent studies revealed that chronic exposure of human bronchial epithelial cells (BEAS-2B, B2B) to Cr(VI) activated several signaling pathways and induced cell malignant transformation and tumor growth. However, new mechanisms of Cr(VI) in inducing carcinogenesis remains to be elucidated. This study showed that miR-199a expression levels were significantly lower in Cr(VI)-transformed Cr-T cells. By using the mouse model, the expression levels of miR-199a were significantly decreased in blood samples and lung tissues of mice intranasally exposed to Cr(VI) for 12 weeks compared to the solvent exposure control. Overexpression of miR-199a inhibited tube formation and angiogenesis. C-X-C motif chemokine ligand 8 (CXCL8, IL8) levels were significantly higher in blood samples of Cr (VI)-exposed workers compared to normal workers, and forced expression of miR-199a in the cells suppressed IL8 levels. miR-199a suppression induced expression of hypoxia-inducible factor 1α (HIF-1α) and nuclear factor kappa B (NF-κB) p65 to increase IL8 expression. With animal experiment, the results showed that miR-199a overexpression inhibited tumor growth and angiogenesis through inhibiting IL8, HIF-1α and NF-κB p65 expression in vivo. These results show that miR-199a/IL8 pathway is important in Cr(VI)-induced carcinogenesis and angiogenesis.

Relationship between systemic inflammation and lung injury induced by chromate exposure: A cross-sectional study in workers

Hexavalent chromium [Cr(VI)] compounds, known as "Group I Human Carcinogen" and "Category I Respiratory Sensitizer", posed great challenges to the respiratory system. A cross-sectional study was undertaken among chromate workers. Serum club cell protein 16 (CC16) and soluble urokinase-type plasminogen activator receptor (suPAR) were measured using ELISA. Thirteen macrophage-related mediators were tested using cytometric bead array. After controlling for sex, age, smoking status, drinking status and BMI, each increase of one-unit of Ln-transformed blood Cr was related to the increase of IL-1beta [Beta (95% CI), 7.22(1.14, 13.29)%, P = 0.021], IL-23 [8.5(1.15, 15.85)%, P = 0.021], IFN-gamma [3.14(0.15, 6.13)%, P = 0.040], and suPAR [9.31(2.5, 16.12) %, P = 0.008], as well as the increase of CC16 by 3.88(0.42, 7.34) % (P = 0.029). Moreover, these inflammatory mediators played an mediation role in the rise of CC16 caused by Cr(VI). The exposure-response curve analysis revealed a substantial nonlinear association of IFN-gamma and suPAR with CC16, thus the mediation effect of INF-gamma and suPAR required cautious interpretation. The positive connection between macrophage-related mediators was stronger in the high exposure group than in the low exposure group, suggesting that high concentration of chromate might promote a complex interplay within the immune system.

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.

Fagonia indica ameliorates chromium-induced nephrotoxicity: Role of antioxidant activity and pro-inflammatory cytokines in in-vivo renoprotection

Chromium (Cr) is an environmental pollutant, has high redox potential, and can exist in various oxidation states, possibly leading to nephrotoxicity. As a potential treatment option, Fagonia indica (F. indica) is an herb remedy traditionally used as a phytomedicine to cure ailments. However, efficient validation of its protective effect and molecular mechanisms has not yet been established. As such, this study aims to investigate the protective effect of F. indica against Cr-induced nephrotoxicity in Swiss mice. Mice were divided into five groups: group I (negative control), group II (F. indica), group III (potassium dichromate [PDC]-treated), group IV (PDC + saline), and group V (PDC + F. indica). Our results demonstrate that group III exhibited decreases in superoxide dismutase (SOD), glutathione s-transferases (GST), glutathione peroxidase (GSH-Px), catalase (CAT), and thioredoxin peroxidase (TPX) levels. Meanwhile, protein carbonyl (PCO) and malondialdehyde (MDA) levels increased in kidney homogenates, increasing the expression of the pro-inflammatory cytokine interleukin-6 (IL-6). This was followed by elevated NF-κB, blood urea nitrogen (BUN), and creatinine serum levels in group III compared with group I. Moreover, histopathological and immunohistochemical examinations demonstrated severe damage to the renal tubular epithelial cells, as well as marked congestion and expressions of caspase-3 and NF-κB. Further, group V showed an improvement in antioxidant activity parameters and reductions in the IL-6, caspase-3, and NF-κB expressions, followed by significant decreases in NF-κB, BUN, and creatinine serum levels. Furthermore, fewer histopathological disturbances were observed compared with untreated group III. Such alterations may be attributed to the antioxidant and anti-inflammatory effects of F. indica. Therefore, our exploration reveals that F. indica is effective in protecting against Cr-induced nephrotoxicity, and it could be applied in the future to human kidney diseases caused by environmental pollutants.

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.

Inflammatory effects of hexavalent chromium in the lung: A comprehensive review

Besides smoking, lung cancer can be caused by other factors, including heavy metals such as cadmium, nickel, arsenic, beryllium and hexavalent chromium [Cr(VI)], which is used in multiple settings, resulting in widespread environmental and occupational exposures as well as heavy use. The mechanism by which Cr(VI) causes lung cancer is not completely understood. Currently, it is admitted chromosome instability is a key process in the mechanism of Cr(VI)-induced cancer, and previous studies have suggested Cr(VI) impacts the lung tissue in mice by triggering tissue damage and inflammation. However, the mechanism underlying Cr(VI)-induced inflammation and its exact role in lung cancer are unclear. Therefore, this review aimed to systematically examine previous studies assessing Cr(VI)-induced inflammation and to summarize the major inflammatory pathways involved in Cr(VI)-induced inflammation. In cell culture studies, COX2, VEGF, JAK-STAT, leukotriene B4 (LTB4), MAPK, NF-ҡB and Nrf2 signaling pathways were consistently upregulated by Cr(VI), clearly demonstrating that these pathways are involved in Cr(VI)-induced inflammation. In addition, Akt signaling was also shown to contribute to Cr(VI)-induced inflammation, although discrepant findings were reported. Few mechanistic studies were performed in animal models, in which Cr(VI) upregulated oxidative pathways, NF-kB signaling and the MAPK pathway in the lung tissue. Similar to cell culture studies, opposite effects of Cr(VI) on Akt signaling were reported. This work provides insights into the mechanisms by which Cr(VI) induces lung inflammation. However, discrepant findings and other major issues in study design, both in cell and animal models, suggest that further studies are required to unveil the mechanism of Cr(VI)-induced inflammation and its role in lung cancer.

Epigenetic and epitranscriptomic mechanisms of chromium carcinogenesis

Hexavalent chromium [Cr(VI)], a Group I carcinogen classified by the International Agency for Research on Cancer (IARC), represents one of the most common occupational and environmental pollutants. The findings from human epidemiological and laboratory animal studies show that long-term exposure to Cr(VI) causes lung cancer and other cancer. Although Cr(VI) is a well-recognized carcinogen, the mechanism of Cr(VI) carcinogenesis has not been well understood. Due to the fact that Cr(VI) undergoes a series of metabolic reductions once entering cells to generate reactive Cr metabolites and reactive oxygen species (ROS) causing genotoxicity, Cr(VI) is generally considered as a genotoxic carcinogen. However, more and more studies have demonstrated that acute or chronic Cr(VI) exposure also causes epigenetic dysregulations including changing DNA methylation, histone posttranslational modifications and regulatory non-coding RNA (microRNA and long non-coding RNA) expressions. Moreover, emerging evidence shows that Cr(VI) exposure is also capable of altering cellular epitranscriptome. Given the increasingly recognized importance of epigenetic and epitranscriptomic dysregulations in cancer initiation and progression, it is believed that Cr(VI) exposure-caused epigenetic and epitranscriptomic changes could play important roles in Cr(VI) carcinogenesis. The goal of this chapter is to review the epigenetic and epitranscriptomic effects of Cr(VI) exposure and discuss their roles in Cr(VI) carcinogenesis. Better understanding the mechanism of Cr(VI) carcinogenesis may identify new molecular targets for more efficient prevention and treatment of cancer resulting from Cr(VI) exposure.

LncRNA SBF2-AS1: A Budding Star in Various Cancers

Long non-coding RNA (lncRNA) is a new kind of RNA with lengths over 200 nucleotides. Current frontiers revealed that lncRNAs implicate in various tumor progression, including tumorigenesis, proliferation, migration, invasion, metastasis and angiogenesis. Recently discovered long non-coding RNA SET-binding factor 2 antisense RNA 1 (lncRNA SBF2-AS1), an oncogenic antisense RNA to SBF2, locates at 11p15.1 locus and is 2708 nt long. Accumulating evidences have demonstrated that lncRNA SBF2-AS1 participates in various tumor progression including pathogenesis, diagnosis, treatment and prognosis of acute myeloid leukemia (AML), breast cancer (BC), cervical cancer (CC), clear cell renal cell carcinoma (ccRCC), colorectal cancer (CRC), diffuse large B-cell lymphoma (DLBCL), esophageal squamous cell carcinoma (ESCC), gastric cancer (GC), glioma, glioblastoma (GBM), hepatocellular carcinoma (HCC), lung cancer (LC), lung adenocarcinoma (LUAD), non-small cell lung cancer (NSCLC), osteosarcoma (OS), pancreatic cancer (PC), papillary thyroid cancer (PTC), small cell lung cancer (SCLC). Therefore, we summarized the underlying mechanisms about lncRNA SBF2-AS1 in various cancers to utilize its therapeutic function in target-selective treatment modality.

Epigenetic Regulation in Exposome-Induced Tumorigenesis: Emerging Roles of ncRNAs

Environmental factors, including pollutants and lifestyle, constitute a significant role in severe, chronic pathologies with an essential societal, economic burden. The measurement of all environmental exposures and assessing their correlation with effects on individual health is defined as the exposome, which interacts with our unique characteristics such as genetics, physiology, and epigenetics. Epigenetics investigates modifications in the expression of genes that do not depend on the underlying DNA sequence. Some studies have confirmed that environmental factors may promote disease in individuals or subsequent progeny through epigenetic alterations. Variations in the epigenetic machinery cause a spectrum of different disorders since these mechanisms are more sensitive to the environment than the genome, due to the inherent reversible nature of the epigenetic landscape. Several epigenetic mechanisms, including modifications in DNA (e.g., methylation), histones, and noncoding RNAs can change genome expression under the exogenous influence. Notably, the role of long noncoding RNAs in epigenetic processes has not been well explored in the context of exposome-induced tumorigenesis. In the present review, our scope is to provide relevant evidence indicating that epigenetic alterations mediate those detrimental effects caused by exposure to environmental toxicants, focusing mainly on a multi-step regulation by diverse noncoding RNAs subtypes.

Particulate hexavalent chromium alters microRNAs in human lung cells that target key carcinogenic pathways

Hexavalent chromium [Cr(VI)] is a global environmental pollutant and human lung carcinogen. However, the mechanisms of Cr(VI) carcinogenesis are not well defined. Cr(VI)-altered gene expression has been reported in the literature and is implicated in numerous mechanisms of Cr(VI) carcinogenesis. MicroRNAs (miRNAs) play a key role in controlling gene expression and are associated with carcinogenic mechanisms. To date no studies have evaluated global changes in miRNA expression in human cells after Cr(VI) exposure. We used RNA sequencing to evaluate how a particulate Cr(VI) compound (zinc chromate), the most potent form of Cr(VI), alters global miRNA expression after acute (24 h) or prolonged (72 and 120 h) exposure to 0.1, 0.2 and 0.3 μg/cm² zinc chromate in an immortalized, non-cancerous human lung cell line (WTHBF-6). Particulate Cr(VI) significantly affected expression of miRNAs at all time points and concentrations tested. We also found the number of significantly downregulated miRNAs increased in a time- and concentration-dependent manner and many miRNAs were upregulated after 24 h exposure at the intermediate concentration tested. Pathway analyses of the differentially expressed miRNAs predicted miRNAs target pathways of Cr(VI) carcinogenesis in a time- and concentration-dependent manner. These data are the first to evaluate global changes in miRNA expression in human lung cells after Cr(VI) exposure and indicate miRNAs may play a key role in pathways of Cr(VI) carcinogenesis.

Redox sensitive miR-27a/b/Nrf2 signaling in Cr(VI)-induced carcinogenesis

Hexavalent chromium [Cr(VI)] is a well-known carcinogen that can cause several types of cancer including lung cancer. NF-E2-related factor 2 (Nrf2), the redox sensitive transcription factor, can protect normal cells from a variety of toxicants and carcinogens by inducing the expression of cellular protective genes and maintaining redox balance. However, Nrf2 also protects cancer cells from radio- and chemo-therapies and facilitates cancer progression. Although Cr(VI) treatment has been demonstrated to upregulate Nrf2 expression, the mechanisms for Nrf2 regulation upon chronic Cr(VI) exposure remain to be elucidated. We found that Nrf2 was upregulated in BEAS-2B cells exposed to Cr(VI) from 1 to 5 months, and also in Cr(VI)-induced transformed (Cr-T) cells with Cr(VI) treatment for 6 months. We showed that KEAP1, the classic negative regulator of Nrf2, was downregulated after Cr(VI) exposure for 4 months, suggesting that Nrf2 induction by Cr(VI) treatment is through KEAP1 decrease at late stage. To further decipher the mechanisms of Nrf2 upregulation at early stage of Cr(VI) exposure, we demonstrated that miR-27a and miR-27b were redox sensitive miRNAs, since reactive oxygen species (ROS) scavengers induced miR-27a/b expression. After Cr(VI) exposure for 1 month, the expression levels of miR-27a/b was dramatically decreased. The changes of miR-27a/b and their target Nrf2 were confirmed in vivo by mouse model intranasally exposed to Cr(VI) for 12 weeks. Nrf2 was a direct target of miR-27a/b, which acted as tumor suppressors in vitro and in vivo to inhibit tumorigenesis and cancer development of Cr-T cells. The results suggested that the inhibition of miR-27a/b was responsible for Nrf2 upregulation at both early stage and late stage of Cr(VI) exposure. This novel regulation of Nrf2 upon chronic Cr(VI) exposure through redox-regulated miR-27a/b will provide potential targets for preventing and treating Cr(VI)-induced carcinogenesis in the future.

Genome wide profiling of miRNAs relevant to the DNA damage response induced by hexavalent chromium exposure (DDR-related miRNAs in response to Cr (VI) exposure)

AIM

We aimed to explore the expression of miRNAs and their potential roles in the DNA damage response (DDR) induced by Cr (VI) exposure in human B lymphoblast cells (HMy2.CIR cells) and in a population of Cr (VI)-exposed humans.

METHODS

Differentially expressed miRNAs were found by a combination of miRNA sequencing and RT-qPCR validation in HMy2.CIR cells treated with K₂Cr₂O₇. Differentially expressed miRNAs related to DDR were selected for functional study. The expression levels of differential miRNAs were also investigated in chromate workers.

RESULTS

A total of 214 differentially expressed miRNAs were identified by sequencing, and the expression of 5 miRNAs among 25 associated with DDR was found to be consistent between sequencing and validation studies.Functional studies showed that miR-148a-3p, miR-21-5p, and miR-424-3p might be related to Cr (VI)-induced cell apoptosis, and miR-221-3p might participate in Cr (VI)-induced DDR. We also found that the expression of miR-21-5p and miR-424-3p was upregulated in chromate workers.

CONCLUSIONS

Cr (VI) exposure could significantly impact miRNAs expression in vitro and in chromate workers. Functional studies showed that miR-148a-3p, miR-21-5p and miR-221-3p might take a crucial role in the cellular DDR induced by Cr (VI) exposure.

Correlation of DNA methylation patterns to the phenotypic features of Tibetan elite alpinists in extreme hypoxia

High altitude is an extreme environment that imposes hypoxic pressure on physiological processes, and natives living at high altitudes are more adaptive in certain physiological processes. So far, epigenetic modifications under extreme changes in hypoxic pressures are relatively less understood. Here, we recruit 32 Tibetan elite alpinists (TEAs), who have successfully mounted Everest (8848 m) at least five times. Blood samples and physiological phenotypes of TEAs and 32 matched non-alpinist Tibetan volunteers (non-TEAs) are collected for analysis. Genome-wide DNA methylation analysis identifies 23,202 differentially methylated CpGs (Padj < 0.05, |β| > 0.1) between the two groups. Some differentially methylated CpGs are in hypoxia-related genes such as PPP1R13L, MAP3K7CL, SEPTI-9, and CUL2. In addition, Gene ontology enrichment analysis reveals several inflammation-related pathways. Phenotypic analysis indicates that 12 phenotypes are significantly different between the two groups. In particular, TEAs exhibit higher blood oxygen saturation levels and lower neutrophil count, platelet count, and heart rate. For DNA methylation association analysis, we find that two CpGs (cg16687447, cg06947206) upstream of PTEN were associated with platelet count. In conclusion, extreme hypoxia exposure leads to epigenetic modifications and phenotypic alterations of TEA, providing us clues for exploring the molecular mechanism underlying changes under extreme hypoxia conditions.

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.

Differentially Expressed MiRNAs of Goat Submandibular Glands Among Three Developmental Stages Are Involved in Immune Functions

Submandibular glands (SMGs) are one of the primary components of salivary glands in goats. The proteins and biologically active substances secreted by the SMGs change with growth and development. Our previous studies showed that most of the differentially expressed genes in the SMGs of goats at different developmental stages are involved in immune-related signaling pathways, but the miRNA expression patterns in the same tissues are unknown. The aim of this study was to reveal the expression profile of miRNAs at three different developmental stages, detect differentially expressed miRNAs (DE miRNAs) and predict disease-related DE miRNAs. SMG tissue samples were collected from groups of 1-month-old kids, 12-month-old maiden goats and 24-month-old adult goats (three samples from each group), and high-throughout transcriptome sequencing was conducted. A total of 178, 241 and 7 DE miRNAs were discovered between 1-month-old kids and 12-month-old maiden goats, between 1-month-old kids and 24-month-old adult goats, and between 12-month-old maiden goats and 24-month-old adult goats, respectively. Among these DE miRNAs, 88 DE miRNAs with medium or high expression levels (TPM ≥50) were classified into five expression pattern clusters. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses indicated that some of the predicted target genes of the DE miRNAs in the five clusters were enriched in disease-related GO terms and pathways. MiRNA target genes in significant pathways were significantly enriched in Hepatitis B (FDR = 9.03E-10) and Pathways in cancer (FDR = 4.2E-10). Further analysis was performed with a PPI network, and 10 miRNAs were predicted to play an important role in the occurrence and prevention of diseases during the growth and development of goats.

Inhalation cancer risk assessment for environmental exposure to hexavalent chromium: Comparison of margin-of-exposure and linear extrapolation approaches

Hexavalent chromium [Cr(VI)] exists in the ambient air at low concentrations (average upperbound ~0.1 ng/m³) yet airborne concentrations typically exceed EPA's Regional Screening Level for residential exposure (0.012 ng/m³) and other similar benchmarks, which assume a mutagenic mode of action (MOA) and use low-dose linear risk assessment models. We reviewed Cr(VI) inhalation unit risk estimates developed by researchers and regulatory agencies for environmental and occupational exposures and the underlying epidemiologic data, updated a previously published MOA analysis, and conducted dose-response modeling of rodent carcinogenicity data to evaluate the need for alternative exposure-response data and risk assessment approaches. Current research supports the role of non-mutagenic key events in the MOA, with growing evidence for epigenetic modifiers. Animal data show a weak carcinogenic response, even at cytotoxic exposures, and highlight the uncertainties associated with the current epidemiological data used in risk assessment. Points of departure from occupational and animal studies were used to determine margins of exposure (MOEs). MOEs range from 1.5 E+3 to 3.3 E+6 with a median of 5 E+5, indicating that current environmental exposures to Cr(VI) in ambient air should be considered of low concern. In this comprehensive review, the divergent results from default linear and MOE assessments support the need for more relevant and robust epidemiologic data, additional mechanistic studies, and refined risk assessment strategies.

Down-regulated lncRNA SBF2-AS1 inhibits tumorigenesis and progression of breast cancer by sponging microRNA-143 and repressing RRS1

Background

Recently, the roles of long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) in human diseases have been unveiled, this research was conducted to explore the impacts of lncRNA SET-binding factor 2-antisense RNA1 (SBF2-AS1), miR-143 and resistance to ralstonia solanacearum 1 (RRS1) on breast cancer (BC) development.

Methods

The expression of SBF2-AS1, miR-143 and RRS1 in BC tissues, as well as in MDA-MB-231 and MCF-7 cell lines were assessed. Subsequently, the cells were transfected with miR-143 mimics or/and silenced or overexpressed SBF2-AS1 plasmids, and their negative controls. Then the proliferation, colony formation ability, cell cycle arrest, apoptosis, invasion and migration of the cells were assessed through gain- and loss-of-function experiments. Furthermore, the tumor growth, ki-67 expression and apoptosis in vivo were observed by subcutaneous tumorigenesis in nude mice. Binding relation between SBF2-AS1 and miR-143, and that between miR-143 and RRS1 were confirmed.

Results

SBF2-AS1 and RRS1 were amplified, while miR-143 was reduced in BC tissues and cells. Reduced SBF2-AS1 and elevated miR-143 could repress the proliferation, invasion and migration via restraining RRS1 expression. Moreover, knockdown of SBF2-AS1 up-regulated miR-143 to promote the apoptosis of BC cells by downregulating RRS1, resulting in a prohibitive effect on the tumorigenesis and progression of BC. Results of in vivo experiments indicated that the inhibited SBF2-AS1 and overexpressed miR-143 could restrict BC cell proliferation and promote apoptosis, and decelerate tumor growth in xenografts.

Conclusion

We have discovered in this study that down-regulated SBF2-AS1 could inhibit tumorigenesis and progression of BC by up-regulation miR-143 and repressing RRS1, which provides basic therapeutic considerations for a novel target against BC.

MiR-27b suppresses epithelial-mesenchymal transition and chemoresistance in lung cancer by targeting Snail1

HEADING AIMS

MicroRNA-27b (miR-27b) has been shown to play a role in the progression of many different forms of cancer, but its specific relevance in the context of non-small cell lung cancer (NSCLC) remains uncertain. As such, this study sought to explore the role of miR-27b in NSCLC and the mechanisms whereby it functions.

MATERIALS AND METHODS

We quantified miR-27b and target gene expression via quantitative real-time PCR (RT-qPCR).We then used functional including proliferation assays, migration assay, flow cytometry, and western blotting to explore the mechanisms whereby miR-27b functions in vitro and in vivo. We additionally confirmed miR-27b target genes via luciferase reporter assay.

KEY FINDINGS

We observed a marked decrease in miR-27b expression in NSCLC patient samples relative to paracancerous control tissues. We further found that altering miR-27b expression levels in vitro affected NSCLC tumor cell migration, proliferation, and ability to undergo epithelial-mesenchymal transition. Through the use of target prediction algorithms we identified Snail to be a miR-27b target protein that was suppressed when this miRNA was highlight expressed. Lastly, we found miR-27b expression to increase NSCLC cell sensitivity to cisplatin through its ability to target Snail.

SIGNIFICANCE

Our results clearly demonstrate that miR-27b can suppress NSCLC tumor development and progression, highlighting this miR-27b/Snail1 axis as putative target for the therapeutic treatment of NSCLC.