Radon Biomonitoring and microRNA in Lung Cancer

Recent advances of miR-23 in human diseases and growth development

MicroRNA (miRNA) is broadly manifested in eukaryotes and serves as a critical function in biological development and disease occurrence. With the rapid advancement of experimental research tools, researchers have discovered functional correlations among different miRNA isoforms and clusters within the same miRNA family. As a highly conserved member in the miR-23-27-24 cluster, miR-23 exhibits different isoforms and participates in various essential development. Although the miR-23-27-24 cluster has overlapping target sites, their differential expression can demonstrate independent biological functions. Furthermore, the untapped effects of miR-23 on organisms, whether as a functional cluster or a single regulator, has not been systematically elucidated yet. In this review article, we analyze the genomic location of miR-23 and its sequence variances among its isoforms or family members while summarizing its regulatory functions in metabolic diseases, immune responses, cardiovascular diseases, cancer, organ development as well as nervous system function. This review highlights the significant role of miR-23 as a biomarker for disease diagnosis and a key regulatory factor in pathogenesis, which can help us comprehend the diverse functions of miRNAs and provide a theoretical reference for the functional differences among miRNA isoforms.

The role of exosomal hsa-miR-125b-5p and hsa-miR-320c as non-invasive biomarkers in high-radon areas of Kazakhstan

BACKGROUND

Radon, a radioactive gas, is a significant risk factor for lung cancer, especially in non-smokers. This study examines the expression of exosomal microRNAs (miRNAs) as potential biomarkers for radon-induced effects.

METHODS

A total of 109 participants from high- and low-radon areas in Kazakhstan were included. Exosomal hsa-miR-125b-5p and hsa-miR-320c levels were quantified using real-time PCR.

RESULTS

Results revealed a 25.4-fold increase in hsa-miR-125b-5p and a 12.5-fold decrease in hsa-miR-320c in participants exposed to high-radon levels compared to controls. Bioinformatic analysis identified key target genes, such as PRDM1 and IRF4, which are implicated in cancer development.

CONCLUSION

These findings suggest that exosomal miRNAs could serve as non-invasive biomarkers for radon exposure, offering potential for early diagnosis and monitoring of radon-induced lung cancer. The study underscores the need for further research to validate these miRNAs as reliable diagnostic tools.

Transcriptomic analysis reveals transcription factors implicated in radon-induced lung carcinogenesis

Background

Radon, a potent carcinogen, is a significant catalyst for lung cancer development. However, the molecular mechanisms triggering radon-induced lung cancer remain elusive.

Methods

Utilizing a radon exposure concentration of 20,000 Bq/m3 for 20 min/session, malignant transformation was induced in human bronchial epithelial cells (BEAS-2B).

Results

Radon-exposed cells derived from passage 25 (BEAS-2B-Rn) exhibited enhanced proliferation and increased colony formation. Analysis of differential gene expression (DEG) through transcription factors revealed 663 up-regulated and 894 down-regulated genes in radon-exposed cells. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed significant alterations in the malignant transformation pathway of cells, including those related to cancer and the PI3K/AKT signaling pathway. A PPI network analysis indicated a significant association of oncogenes, such as CCND1, KIT, and GATA3, with lung cancer among differentially expressed genes. In addition, the stability of the housekeeping gene was determined through RT-qPCR analysis, which also confirmed the results of transcriptome analysis.

Conclusions

The results suggest that transcription factors may play a pivotal role in conferring a survival advantage to radon-exposed cells. This is achieved by malignant transformation of human bronchial epithelial cells into lung carcinogenesis cell phenotypes.

Radon and lung cancer: Current status and future prospects

Beyond tobacco smoking, radon takes its place as the second most significant contributor to lung cancer, excluding hereditary and other biologically related factors. Radon and its byproducts play a pivotal role in exposing humans to elevated levels of natural radiation. Approximately 10-20 % of lung cancer cases worldwide can be attributed to radon exposure, leading to between 3 % and 20 % of all lung cancer-related deaths. Nevertheless, a knowledge gap persists regarding the association between radon and lung cancer, impeding radon risk reduction initiatives globally. This review presents a comprehensive overview of the current state of research in epidemiology, cell biology, dosimetry, and risk modeling concerning radon exposure and its relevance to lung cancer. It also delves into methods for measuring radon concentrations, monitoring radon risk zones, and identifying priorities for future research.

Simultaneous measurements of radon, thoron and thoron progeny and induced cancer risk assessment in Djeno, Pointe-Noire, Republic of Congo

In this study, the activity concentrations of radon (222Rn), thoron (220Rn) and thoron progeny were measured simultaneously in Djeno (Pointe-Noire, Republic of Congo) using RADUET detectors to evaluate the air quality and the radiological risks due to the inhalation of these radionuclides. Activity concentrations of radon progeny were calculated from those of radon. Indoor radon, thoron and progenies followed a lognormal distribution ranging between 20 and 40, 6 and 62, 8 and 17.6 and 0.4 and 19.6 Bq m-3 for radon, thoron, radon progeny and thoron progeny, respectively. Mean values for radon were lower than the worldwide values estimated by the United Nation Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), which are 40 Bq m-3 (arithmetic mean) and 45 Bq m-3 (geometric mean). Radon concentrations in the dwellings under study were below the World Health Organization and the International Commission on Radiological Protection recommended reference levels, which are, respectively, 100 and 300 Bq m-3. The mean concentration of thoron was twice the world average value of 10 Bq m-3 estimated by UNSCEAR. Thoron progeny mean concentration was sharply greater than the typical value (0.3 Bq m-3) for indoor atmosphere provided by UNSCEAR. Annual effective dose ranges were 0.40-0.87 mSv (arithmetic mean, 0.57 ± 0.11 mSv) for radon and 0.10-4.14 mSv (arithmetic mean, 0.55 ± 0.77 mSv) for thoron. The mean value for radon was lower than the value (1.15 mSv) estimated by UNSCEAR, while the mean value for thoron was five times higher than the UNSCEAR value (0.10 mSv). The study showed that the use of the typical equilibrium factor value given by UNSCEAR to compute effective dose led to an error above 80%. Finally, the results of this study showed that the excess relative risk of radon-induced cancer was low, below 2% for the population under 55 y. The results presented in the present study prove that the population of Djeno is exposed to a relatively low potential risk of radon- and thoron-induced cancer.

miR-325 Supresses Cell Proliferation and Migration in Non-Small Cell Lung Cancer via Targeting DNA Ligase 1 (LIG1)

DNA ligase 1 (LIG1) plays a key role in DNA synthesis and DNA damage repair pathways. LIG1 has been shown to be up-regulated in human non-small cell lung cancer (NSCLC); however, its role and molecular regulatory mechanism in NSCLC cell proliferation are still not fully understand. In this study, we aimed to explore the role of LIG1 and post-transcripional regulators in NSCLC. Utilizing bioinformatic tools and qRT-PCR, our investigation substantiated the up-regulation of LIG1 within NSCLC cell lines and tumour tissues. Remarkably, individuals exhibiting elevated levels of LIG1 had diminished survival rates. Functionally, the depletion of LIG1 inhibited cell proliferation and migration, contrasting with the increased proliferation and migration upon LIG1 over-expression. Prediction from the TargetScanHuman database and results of dual luciferase reporter assays indicated that miR-325 could directly bind to and negatively regulate LIG1. Moreover, our findings demonstrated that the mimicry of miR-325 decreased cell viability, whereas its inhibition correspondingly increased viability, indicative of the tumour-suppressive role of miR-325 through the down-regulation of LIG1. Collectively, our findings show that LIG1 could promote tumour progression and knockdown of LIG1 could exert suppressive effects on NSCLC. As the post-transcriptional factor of LIG1, miR-325 could negatively regulate the expression of LIG1 to inhibit tumour progression in vitro. These findings suggest that LIG1 and miR-325 might be potential therapeutic targets for NSCLC treatment.

Radon exhalation characteristics after pyrolysis of long flame coal

Coal pyrolysis is a important method for classifying and utilizing coal resources and contributes to enhanced comprehensive resource utilization. However, In high-temperature areas such as coal pyrolysis, there is an abnormal phenomenon release of radioactive gas radon, understanding the relationship between temperature and radon exhalation characteristics, as well as the underlying mechanisms, holds great importance for assessing radon pollution in mining areas. After coal undergoes pyrolysis under high temperature conditions, its material composition, pore structure, water content, and other properties have changed. The pyrolysis products in different atmosphere environments have differences, and the characteristics of radon emission are also different. To address this, the present study conducted coal pyrolysis experiments in both aerobic and anaerobic environments, using long flame coal sourced from Yulin, China. The radon release concentration of the pyrolysis products was measured. The research findings indicate that during pyrolysis at elevated temperatures, the ratio of coal mass loss is constantly increasing. High temperatures promote the development of pores and fissures, and significant changes in coal properties at temperature thresholds (300 °C and 500 °C). The specific surface area, pore volume, and fracture ratio all display substantial increases, and the amplitude of change is greater under aerobic conditions. The fractal dimension of total pores and macropores shows continuous growth, while the specific surface area, pore volume, and fracture ratio exhibit a strong negative correlation with the radon emission rate of pyrolysis products. The expansion and penetration of pores and cracks, along with the release of a substantial amount of pyrolysis gas, accelerate the transformation, migration, and exhalation of radon, resulting in a negative correlation between the heat treatment temperature and the radon release rate of pyrolysis products. Under aerobic conditions, the radon release rate of pyrolysis products decreases more significantly.

Preliminary study of chromosome aberrations using Giemsa, two-colour fish, and micronucleus assays in lymphocytes of individuals living in elevated radon concentration areas

The frequencies of unstable and stable chromosome aberrations and micronuclei were examined in peripheral blood samples from 10 individuals living in elevated radon concentration areas (Takandeang Village, Mamuju, Indonesia). Blood samples from 10 people living in Topoyo Village were used as a control group. For unstable chromosome aberration analysis, a dicentric chromosome assay was conducted using conventional Giemsa staining. Chromosomal painting of chromosomes 1 and 4 using the fluorescence in situ hybridisation technique was also applied to four subjects to assess the stable chromosome aberration. Our study showed no significant increases across all groups in dicentric and other unstable chromosome aberrations, such as rings and acentric fragments. Translocations were found in one person from Takandeang Village and two Topoyo Village inhabitants. The translocations found in the subjects from Takandeang Village were due more to aging factors than to radon exposure. The number of micronuclei per 1000 binucleus cells in Takandeang Village inhabitants was not significantly different than that in the control group (p = 0.943). A more comprehensive analysis should be conducted in a subsequent study by increasing the number of study donors and the number of metaphases to be analysed in both dicentric chromosome assay and fluorescence in situ hybridisation assays. Such research could provide valid information on the cytogenetic effects of elevated indoor radon exposure.

Vaping, Environmental Toxicants Exposure, and Lung Cancer Risk

Lung cancer (LC) is the second-most prevalent tumor worldwide. According to the most recent GLOBOCAN data, over 2.2 million LC cases were reported in 2020, with an estimated new death incident of 1,796,144 lung cancer cases. Genetic, lifestyle, and environmental exposure play an important role as risk factors for LC. E-cigarette, or vaping, products (EVPs) use has been dramatically increasing world-wide. There is growing concern that EVPs consumption may increase the risk of LC because EVPs contain several proven carcinogenic compounds. However, the relationship between EVPs and LC is not well established. E-cigarette contains nicotine derivatives (e.g., nitrosnornicotine, nitrosamine ketone), heavy metals (including organometal compounds), polycyclic aromatic hydrocarbons, and flavorings (aldehydes and complex organics). Several environmental toxicants have been proven to contribute to LC. Proven and plausible environmental carcinogens could be physical (ionizing and non-ionizing radiation), chemicals (such as asbestos, formaldehyde, and dioxins), and heavy metals (such as cobalt, arsenic, cadmium, chromium, and nickel). Air pollution, especially particulate matter (PM) emitted from vehicles and industrial exhausts, is linked with LC. Although extensive environmental exposure prevention policies and smoking reduction strategies have been adopted globally, the dangers remain. Combined, both EVPs and toxic environmental exposures may demonstrate significant synergistic oncogenicity. This review aims to analyze the current publications on the importance of the relationship between EVPs consumption and environmental toxicants in the pathogenesis of LC.

Tumor cells-derived exosomal PD-L1 promotes the growth and invasion of lung cancer cells <em>in vitro via</em> mediating macrophages M2 polarization

Lung cancer originating from the bronchial epithelium is the most common lung malignancy. It has been reported that programmed cell death 1 ligand 1 (PD-L1) and tumor-associated macrophages are closely related to the development of lung cancer. However, whether tumor-derived exosomal PD-L1 could mediate the regulation of macrophage polarization in lung cancer remains unclear. For this research, the level of PD-L1 in normal tissues and lung cancer tissues was evaluated using RT-qPCR. Next, the apoptosis of lung cancer cells was evaluated using flow cytometry assay. Then, the structure and morphology of vesicles were observed using transmission electron microscopy and nanoparticle tracking analysis. Later on, the internalization of exosomes by macrophage was observed using fluorescence microscopy. Our results showed that the level of PD-L1 was upregulated in tumor tissues and lung cancer cells. Knockdown of PD-L1 notably inhibited the viability, migration and invasion of lung cancer cells. In addition, lung cancer cells-derived exosomal PD-L1 could be absorbed by macrophages. Meanwhile, exosomal PD-L1 was able to promote macrophages M2 polarization. Moreover, macrophages M2 polarization induced by exosomal PD-L1 further remarkably promoted the viability, migration, invasion, and epithelial-mesenchymal transition process of lung cancer cells. Collectively, knockdown of PD-L1 notably inhibited the viability, migration and invasion of lung cancer cells. Tumor cell-derived exosomal PD-L1 could promote the growth of lung cancer cells by mediating macrophages M2 polarization. Thus, inhibiting macrophages M2 polarization might be a promoting therapy for the treatment of lung cancer.

Anwuligan inhibits the progression of non-small cell lung cancer via let-7c-3p/PI3K/AKT/mTOR axis

BACKGROUND

Anwuligan (ANW) isolated from nutmeg, also known as myristyl lignan, has attracted attention due to its therapeutic potential in diseases. However, its effect on lung cancer is still unclear.

METHODS

In this study, the cytotoxicity of ANW on non-small cell lung cancer (NSCLC) cells was detected using a Cell Counting Kit-8 (CCK-8) assay. In vitro, clone formation, wound healing, and Transwell assays were used to investigate the migratory and invasive abilities of NSCLC cells after ANW treatment. The expression levels of the associated proteins were detected using Western blotting. A luciferase assay was used to validate the binding of let-7c-3p to the 3'-untranslated region (UTR) of PIK3CA. In vivo, an A549 cell xenograft mouse model was used to verify the effect of ANW on tumor growth.

RESULTS

The results showed that ANW treatment (20 or 50 μM) had obvious cytotoxicity against A549 and H460 cells, suppressing cell proliferation and migration in vitro. In vivo, the growth of the implanted tumor was inhibited by ANW in a nude mouse model. The growth of NSCLC cells was also inhibited by let-7c-3p overexpression in vitro and in vivo. The inhibitory effect of ANW on the proliferation and metastasis of NSCLC cells was weakened by the downregulation of let-7c-3p, whereas it was enhanced by the overexpression of let-7c-3p; PIK3CA was the main target of let-7c-3p.

CONCLUSIONS

In summary, ANW inhibits the growth and metastasis of NSCLC cells in vivo and in vitro by upregulating the expression of let-7c-3p, which can regulate the PI3K/AKT/mTOR signaling pathway. PIK3CA is the main target of let-7c-3p.

Benzene Exposure and MicroRNAs Expression: In Vitro, In Vivo and Human Findings

MicroRNAs (miRNAs) are important regulators of gene expression and define part of the epigenetic signature. Their influence on human health is established and interest in them is progressively increasing. Environmental and occupational risk factors affecting human health include chemical agents. Benzene represents a pollutant of concern due to its ubiquity and because it may alter gene expression by epigenetic mechanisms, including miRNA expression changes. This review summarizes recent findings on miRNAs associated with benzene exposure considering in vivo, in vitro and human findings in order to better understand the molecular mechanisms through which benzene induces toxic effects and to evaluate whether selected miRNAs may be used as biomarkers associated with benzene exposure. Original research has been included and the study selection, data extraction and assessments agreed with PRISMA criteria. Both in vitro studies and human results showed a variation in miRNAs' expression after exposure to benzene. In vivo surveys also exhibited this trend, but they cannot be regarded as conclusive because of their small number. However, this review confirms the potential role of miRNAs as "early warning" signals in the biological response induced by exposure to benzene. The importance of identifying miRNAs' expression, which, once validated, might work as sentinel molecules to better understand the extent of the exposure to xenobiotics, is clear. The identification of miRNAs as a molecular signature associated with specific exposure would be advantageous for disease prevention and health promotion in the workplace.

Comprehensive Analysis of Circular RNA Expression Profiles in Gefitinib-Resistant Lung Adenocarcinoma Patients

Introduction: Gefitinib is a selective epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) widely used in lung adenocarcinoma (LUAD) patients harboring sensitive EGFR mutations. Although it has a good initial efficacy, acquired resistance to gefitinib is eventually inevitable. Studies have shown that circular RNA (circRNA) is involved in the development of acquired resistance to different anti-cancer drugs, but the comprehensive analysis of its expression profile and functions on acquired gefitinib resistance remains poor. Methods: To explore the aberrant circRNAs expression profiles, we collected peripheral plasma samples from 4 gefitinib-sensitive and 4 gefitinib-resistant patients for performing microarray analysis. Candidates of differentially expressed circRNAs were used and analyzed by bioinformatics modalities including gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and a constructed circRNA-microRNA RNA network. The differential expression of selected circRNAs was verified by quantitative real-time PCR (qRT-PCR). Results: A total of 2571 circRNAs with significantly different expression between the groups were identified by microarray analysis. GO, KEGG, and pathway enrichment analyses reveal that these differentially expressed circRNAs (DECs) were complicated in many biological pathways that may be related to EGFR-TKI resistance such as ABC transporter and PI3K-Akt pathways. A circRNA-microRNA network was constructed by 10 circRNAs potentially involved in EGFR-TKI resistance togethering with their corresponding microRNAs (miRNAs). Consistent with the results of microarray assay, hsa_circ_0030591 and hsa_circ_0040348 were validated to be upregulated in gefitinib-resistant patients by qRT-PCR. Conclusions: Our study provides valuable data on circRNAs expression profiles detected in liquid biopsy for LUAD patients with acquired gefitinib resistance, and we validate that upregulations of hsa_circ_0030591 and hsa_circ_0040348 may play key roles in EGFR-TKI resistance and thus serving as candidates for biomarker.

A study on the differences in radon exhalation of different lithologies at various depths and the factors influencing its distribution in northern Shaanxi, China

The inhalation of a high concentration of radon gas increases the risk of cancer. Therefore, it is of utmost necessity to pay due attention to the problem of environmental radon pollution. The high radioactivity above the coal slab causes serious radon radiation contamination on the mining grounds in coal mining areas such as the northern part of China and the western part of the United States. At present, there is a lack of research on radon exhalation in different lithologies. In this study, the differences in the radon exhalation of different lithologies at various depths and their controlling factors were studied by NMR and radon measurement. The results highlighted that the radon exhalation rates in different rocks varied from 0.3 to 0.6 Bq/m²·s. The average radon exhalation rate of the soil was 0.7 Bq/m²·s, and the radon exhalation rates of different lithologies followed the pattern red clay > loess > sandstone > mudstone > coal. The radon exhalation rate increased initially, followed by a decrease, and the radon exhalation rate was the highest at the boundary between the soil and rock layers. The radon exhalation rates of different lithologies have a strong correlation with the small pores (<0.1 μm), which govern the changes in the porous structure with depth. The results of this study are important from the perspective evaluation of environmental radon pollution.

Measurement of Radon Concentration in Water within Ojo Axis of Lagos State, Nigeria

Background: The problem of radon (Radon-222) in water is one of the daily health hazards faced by those in Ojo Axis, Nigeria. Therefore, continuous monitoring of radon contamination in different types of water is essential. In the present work, sixteen groundwater and surface-water samples (wells, boreholes, and sachets) were collected from six different locations within the Ojo Local Government area in Nigeria. The water samples collected were stored in 75 cl bottles that were already sterilized with distilled water to avoid contamination. Water samples were then taken to the laboratory for the analysis of radon levels using a RAD7, an active electronic device produced by the Durridge Company in the USA. The radon level in the water is higher than the safe limits of 11.1 Bq/L, as per EPA regulations, except for two sample points from the studied areas. The total annual effective doses from ingestion and inhalation for drinking and groundwater were higher than the safe limit of 0.1 mSv y−1 that is recommended by the World Health Organization and the European Union Commission. Conclusions: The obtained results underline the importance of the development and/or updating of databases regarding radon levels in drinking and groundwater in the Ojo Local Government area in Nigeria.

Chromosome aberrations, micronucleus frequency, and catalase concentration in a population chronically exposed to high levels of radon

PURPOSE

To deepen our knowledge on the effects of high levels of indoor radon exposure, we assessed the frequencies of unstable and stable chromosome aberrations and micronucleus (MN), as well as the concentration of an endogenous antioxidant (catalase, CAT), in blood samples of individuals chronically exposed to high indoor radon concentrations in Indonesia (Tande-Tande sub-village, Mamuju, West Sulawesi). Moreover, we also investigated the occurrence of a radio-adaptive response (RAR) in Tande-Tande sub-village inhabitants using the G2 MN assay.

MATERIALS AND METHODS

The frequencies of dicentric (DC), acentric (AF), ring (R), and translocation (Tr) chromosomes in Tande-Tande inhabitants were compared to those in people living in a reference area with low levels of indoor radon levels (Topoyo village, Indonesia). The number of MN per 1000 binucleated cells (BNC) and CAT concentration per total protein was quantified and compared between groups. Lastly, we irradiated (2 Gy) phytohemagglutinin-stimulated samples in vitro and measured the frequency of MN to verify the occurrence of a RAR in Tande-Tande sub-village inhabitants.

RESULTS AND CONCLUSION

The frequencies of DC, AF, and Tr did not differ between Tande-Tande inhabitants and control subjects (p = 0.350, 0.521, 0.597). The frequency of MN in Tande-Tande inhabitants was significantly lower than that in the control group (p = 0.006). Similarly, CAT concentration in Tande-Tande inhabitants was also significantly lower than that in the control population (p < 0.001). Significant negative correlations were identified for MN number and CAT concentration versus indoor radon concentration, annual effective dose, or cumulative dose both within groups and when all data were analyzed together. Our findings indicate that, despite the high indoor radon levels, Tande-Tande inhabitants are not under oxidative stress, since this group had lower CAT concentration and MN frequency than those in the control group. The negative correlation between MN frequency and indoor radon concentration, annual effective dose, and cumulative dose suggests the occurrence of an RAR phenomenon in Tande-Tande sub-village inhabitants. This interpretation is also supported by the results of the G2 MN assay, which revealed lower MN frequencies after in vitro irradiation of samples from Tande-Tande sub-village inhabitants than those in samples from the control group (p = 0.0069, for cumulative MN frequency; p = 0.0146, for radiation-induced MN only).

Radon and Lung Cancer: Current Trends and Future Perspectives

Simple Summary

Radon represents the main risk factor of lung cancer in non-smokers and the second one in smoking patients. In Europe, there are several radon-prone areas, but regulatory policies may vary between countries. Radon causes DNA damage and high genomic tumor instability, but its exact carcinogenesis mechanism in lung cancer remains unknown. Molecular drivers in NSCLC are more often described in non-smoker patients and a potential association between radon exposure and oncogenic-driven NSCLC has been postulated. This is an updated review on indoor radon exposure and its role in lung cancer carcinogenesis, especially focusing on its potential relation with NSCLC with driver genomic alterations. We want to contribute to rising knowledge and awareness on this still silent but preventable lung cancer risk factor.

Abstract

Lung cancer is a public health problem and the first cause of cancer death worldwide. Radon is a radioactive gas that tends to accumulate inside homes, and it is the second lung cancer risk factor after smoking, and the first one in non-smokers. In Europe, there are several radon-prone areas, and although the 2013/59 EURATOM directive is aimed to regulate indoor radon exposition, regulating measures can vary between countries. Radon emits alpha-ionizing radiation that has been linked to a wide variety of cytotoxic and genotoxic effects; however, the link between lung cancer and radon from the genomic point of view remains poorly described. Driver molecular alterations have been recently identified in non-small lung cancer (NSCLC), such as somatic mutations (EGFR, BRAF, HER2, MET) or chromosomal rearrangements (ALK, ROS1, RET, NTRK), mainly in the non-smoking population, where no risk factor has been identified yet. An association between radon exposure and oncogenic NSCLC in non-smokers has been hypothesised. This paper provides a practical, concise and updated review on the implications of indoor radon in lung cancer carcinogenesis, and especially of its potential relation with NSCLC with driver genomic alterations.

The level of free-circulating mtDNA in patients with radon-induced lung cancer

OBJECTIVE

According to the World Health Organization, radon is the second leading cause of lung cancer after smoking. Cell free circulating mitochondrial DNA (cf mtDNA) have been used not only as a biomarker of carcinogenesis but also as a biomarker of exposure to radiation, but nothing is known about changes in the level of cf mtDNA following radon exposure. Therefore, the purpose of this study was to estimate the cf mtDNA copy number as a biomarker of the response to radon exposure in lung cancer pathogenesis.

METHODS

207 subjects were examined including 41 radon-exposed lung cancer patients, 40 lung cancer patients without radon exposure and 126 healthy controls exposed/not exposed to high level of radon. Total cell free circulating DNA from blood samples was extracted and used to detect cell free circulating mitochondrial DNA copy number by quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

Our data indicate that the level of cf mtDNA in the radon-induced lung cancer patients was significantly higher than that of the other study participants. There was a significant difference in the level of cf mtDNA in the blood plasma of healthy volunteers exposed and not exposed to high doses of radon. Moreover, in healthy volunteers living in areas with high radon levels, the mtDNA copy number was higher than that in patients with lung cancer who were not exposed to high doses of radon.

CONCLUSION

Our study provides evidence for a possible role of cf mtDNA as a promising biomarker of lung cancer induced by exposure to high dose of radon.

Mixed Contaminants: Occurrence, Interactions, Toxicity, Detection, and Remediation

The ever-increasing rate of pollution has attracted considerable interest in research. Several anthropogenic activities have diminished soil, air, and water quality and have led to complex chemical pollutants. This review aims to provide a clear idea about the latest and most prevalent pollutants such as heavy metals, PAHs, pesticides, hydrocarbons, and pharmaceuticals—their occurrence in various complex mixtures and how several environmental factors influence their interaction. The mechanism adopted by these contaminants to form the complex mixtures leading to the rise of a new class of contaminants, and thus resulting in severe threats to human health and the environment, has also been exhibited. Additionally, this review provides an in-depth idea of various in vivo, in vitro, and trending biomarkers used for risk assessment and identifies the occurrence of mixed contaminants even at very minute concentrations. Much importance has been given to remediation technologies to understand our current position in handling these contaminants and how the technologies can be improved. This paper aims to create awareness among readers about the most ubiquitous contaminants and how simple ways can be adopted to tackle the same.

MicroRNAs as Biomarkers for Ionizing Radiation Injury

Accidental radiation exposures such as industrial accidents and nuclear catastrophes pose a threat to human health, and the potential or substantial injury caused by ionizing radiation (IR) from medical treatment that cannot be ignored. Although the mechanisms of IR-induced damage to various organs have been gradually investigated, medical treatment of irradiated individuals is still based on clinical symptoms. Hence, minimally invasive biomarkers that can predict radiation damage are urgently needed for appropriate medical management after radiation exposure. In the field of radiation biomarker, finding molecular biomarkers to assess different levels of radiation damage is an important direction. In recent years, microRNAs have been widely reported as several diseases’ biomarkers, such as cancer and cardiovascular diseases, and microRNAs are also of interest to the ionizing radiation field as radiation response molecules, thus researchers are turning attention to the potential of microRNAs as biomarkers in tumor radiation response and the radiation toxicity prediction of normal tissues. In this review, we summarize the distribution of microRNAs, the progress on research of microRNAs as markers of IR, and make a hypothesis about the origin and destination of microRNAs in vivo after IR.

The Role of Mitochondrial miRNAs in the Development of Radon-Induced Lung Cancer

MicroRNAs are short, non-coding RNA molecules regulating gene expression by inhibiting the translation of messenger RNA (mRNA) or leading to degradation. The miRNAs are encoded in the nuclear genome and exported to the cytosol. However, miRNAs have been found in mitochondria and are probably derived from mitochondrial DNA. These miRNAs are able to directly regulate mitochondrial genes and mitochondrial activity. Mitochondrial dysfunction is the cause of many diseases, including cancer. In this review, we consider the role of mitochondrial miRNAs in the pathogenesis of lung cancer with particular reference to radon exposure.

Superoxide dismutase and glutathione peroxidase activities in a population exposed to high indoor radon concentration: a preliminary report

The objective of this study was to assess the effect of radon exposure on the modulation of endogenous antioxidants in a population chronically exposed to high levels of radon indoors. To do so, we measured the activities of superoxide dismutase (SOD) and glutathione peroxidase (GPX) in peripheral blood mononuclear cells (PBMCs) of people living in an area with high indoor radon concentration (Tande-Tande sub-village, Indonesia). The activities of SOD and GPX in Tande-Tande inhabitants were compared with those in subjects living in the Topoyo village (Indonesia), an area with low indoor radon levels. The activities of SOD and GPX in Tande-Tande sub-village inhabitants did not differ from those in people living in the Topoyo village (0.37 ± 0.021 versus 0.28 ± 0.018 U/mg protein and 8.46 ± 1.48 versus 8.34 ± 1.65 U/mg protein, p > .05). For both populations, there was a significant positive correlation between SOD and GPX activities (p < .001). No significant effects of gender, age, smoking habit, and body mass index on SOD and GPX activities were found for both groups. Although no significant modulation of SOD and GPX activities in PBMCs was detected, further studies should expand the sample size and also assess antioxidant levels in the serum. This study provides a first picture of endogenous antioxidant systems in Tande-Tande sub-village inhabitants, but a more comprehensive analysis, including the measurement of catalase (CAT) activity, might provide additional insight into the effects of chronic exposure to high indoor radon concentrations.

Association of Exosomal miR-210 with Signaling Pathways Implicated in Lung Cancer

MicroRNA is a class of non-coding RNA involved in post-transcriptional gene regulation. Aberrant expression of miRNAs is well-documented in molecular cancer biology. Extensive research has shown that miR-210 is implicated in the progression of multiple cancers including that of the lung, bladder, colon, and renal cell carcinoma. In recent years, exosomes have been evidenced to facilitate cell–cell communication and signaling through packaging and transporting active biomolecules such as miRNAs and thereby modify the cellular microenvironment favorable for lung cancers. MiRNAs encapsulated inside the lipid bilayer of exosomes are stabilized and transmitted to target cells to exert alterations in the epigenetic landscape. The currently available literature indicates that exosomal miR-210 is involved in the regulation of various lung cancer-related signaling molecules and pathways, including STAT3, TIMP-1, KRAS/BACH2/GATA-3/RIP3, and PI3K/AKT. Here, we highlight major findings and progress on the roles of exosomal miR-210 in lung cancer.

Therapeutic potential of AMPK signaling targeting in lung cancer: Advances, challenges and future prospects

Lung cancer (LC) is a leading cause of death worldwide with high mortality and morbidity. A wide variety of risk factors are considered for LC development such as smoking, air pollution and family history. It appears that genetic and epigenetic factors are also potential players in LC development and progression. AMP-activated protein kinase (AMPK) is a signaling pathway with vital function in inducing energy balance and homeostasis. An increase in AMP:ATP and ADP:ATP ratio leads to activation of AMPK signaling by upstream mediators such as LKB1 and CamKK. Dysregulation of AMPK signaling is a common finding in different cancers, particularly LC. AMPK activation can significantly enhance LC metastasis via EMT induction. Upstream mediators such as PLAG1, IMPAD1, and TUFM can regulate AMPK-mediated metastasis. AMPK activation can promote proliferation and survival of LC cells via glycolysis induction. In suppressing LC progression, anti-tumor compounds including metformin, ginsenosides, casticin and duloxetine dually induce/inhibit AMPK signaling. This is due to double-edged sword role of AMPK signaling in LC cells. Furthermore, AMPK signaling can regulate response of LC cells to chemotherapy and radiotherapy that are discussed in the current review.

Protection of melatonin against long-term radon exposure-caused lung injury

Radon is one of the major pathogenic factors worldwide. Recently, epidemiological studies have suggested that radon exposure plays an important role in lung injury, which could further cause cancer. However, the toxic effects and underlying mechanism on lung injury are still not clear. Here, we identified the detailed toxic effects of long-term radon exposure. Specifically, the manifestations were inflammatory response and cell apoptosis in dose- and time-dependent manners. In detail, it caused the mitochondrial dysfunction and oxidative stress as determined by the abnormal levels of mitochondrial DNA copy number, adenosine triphosphate, mitochondrial membrane potential, superoxide dismutase, and cycloxygenase-2. Furthermore, we found that melatonin treatment ameliorated mitochondrial dysfunction and attenuated the levels of oxidative stress caused by long-term radon exposure, which could further inhibit the lung tissue apoptosis as determined by the decreased levels of cleaved caspase 3. Our study would provide potential therapeutic application of melatonin on lung tissue injury caused by long-term radon exposure.

Role of microRNAs in Lung Carcinogenesis Induced by Asbestos

MicroRNAs are a class of small noncoding endogenous RNAs 19–25 nucleotides long, which play an important role in the post-transcriptional regulation of gene expression by targeting mRNA targets with subsequent repression of translation. MicroRNAs are involved in the pathogenesis of numerous diseases, including cancer. Lung cancer is the leading cause of cancer death in the world. Lung cancer is usually associated with tobacco smoking. However, about 25% of lung cancer cases occur in people who have never smoked. According to the International Agency for Research on Cancer, asbestos has been classified as one of the cancerogenic factors for lung cancer. The mechanism of malignant transformation under the influence of asbestos is associated with the genotoxic effect of reactive oxygen species, which initiate the processes of DNA damage in the cell. However, epigenetic mechanisms such as changes in the microRNA expression profile may also be implicated in the pathogenesis of asbestos-induced lung cancer. Numerous studies have shown that microRNAs can serve as a biomarker of the effects of various adverse environmental factors on the human body. This review examines the role of microRNAs, the expression profile of which changes upon exposure to asbestos, in key processes of carcinogenesis, such as proliferation, cell survival, metastasis, neo-angiogenesis, and immune response avoidance.

Field Cancerization in NSCLC: A New Perspective on MicroRNAs in Macrophage Polarization

Lung cancer is currently the first cause of cancer-related death. The major lung cancer subtype is non-small cell lung cancers (NSCLC), which accounts for approximatively 85% of cases. The major carcinogenic associated with lung cancer is tobacco smoke, which produces long-lasting and progressive damage to the respiratory tract. The progressive and diffuse alterations that occur in the respiratory tract of patients with cancer and premalignant lesions have been described as field cancerization. At the level of tumor cells, adjacent tumor microenvironment (TME) and cancerized field are taking place dynamic interactions through direct cell-to-cell communication or through extracellular vesicles. These molecular messages exchanged between tumor and nontumor cells are represented by proteins, noncoding RNAs (ncRNAs) and microRNAs (miRNAs). In this paper, we analyze the miRNA roles in the macrophage polarization at the level of TME and cancerized field in NSCLC. Identifying molecular players that can influence the phenotypic states at the level of malignant cells, tumor microenvironment and cancerized field can provide us new insights into tumor regulatory mechanisms that can be further modulated to restore the immunogenic capacity of the TME. This approach could revert alterations in the cancerized field and could enhance currently available therapy approaches.