Distribution of N-nitrosamines in drinking water and human urinary excretions in high incidence area of esophageal cancer in Huai'an, China

Bclaf1 mediates super-enhancer-driven activation of POLR2A to enhance chromatin accessibility in nitrosamine-induced esophageal carcinogenesis

Gene-environment interactions are pivotal contributors to nitrosamine-induced esophageal carcinogenesis. While genetic mechanisms in esophageal carcinoma (ESCA) are well-defined, epigenetic drivers remain elusive. This study identifies a novel mechanism of epigenetic regulation centered on B-cell lymphoma-2-associated transcription factor 1 (Bclaf1) in nitrosamine-induced (Methylnitronitrosoguanidine, MNNG) esophageal carcinogenesis. In nitrosamine-induced malignant transformation cells (MNNG-M), Bclaf1 expression is progressively increased with malignancy, and elevated Bclaf1 levels are correlated with poor prognosis in ESCA patients. Functionally, Bclaf1 significantly promotes the abnormal proliferation of MNNG-M and ESCA cells in vitro and in vivo. Mechanistically, transposase-accessible chromatin sequencing (ATAC-seq) results suggest that Bclaf1 silencing markedly reduces chromatin accessibility, thereby impairing the synthesis of newly transcribed RNA. Bclaf1 activates RNA polymerase II subunit POLR2A to promote chromatin accessibility through distinct transcriptional and splicing mechanisms. More specifically, cleavage under targets and tagmentation (CUT&Tag) assays revealed Bclaf1/P300/H3K27ac co-recruitment at the POLR2A promoter, driving transcription via the E2/E3 elements of the POLR2A super-enhancer. Additionally, RNA-binding protein immunoprecipitation (RIP) assays demonstrated that the Bclaf1 cofactor, small nuclear ribonucleoprotein polypeptide A (SNRPA), interacts with pre-POLR2A to regulate its splicing. Collectively, our study reveals that Bclaf1 facilitates nitrosamine-induced ESCA by controlling POLR2A transcriptional and splicing activities, providing novel insight for early detection and intervention.

The association between N-nitrosamines exposure and lipid metabolism in the high incidence area of esophageal cancer: A case-control analysis

Environmental carcinogens such as N-nitrosamines are high-risk factors for the development of esophageal cancer (EC). However, the association between nitrosamines exposure and lipid metabolism disorders in human EC remained largely obscure. Therefore, we conducted a population-based case-control study established with esophageal inflammation (BCH), esophageal heterotrophic hyperplasia (DYS), patients with primary EC and matched controls in high prevalence area of EC in China. Our prospective work investigated the joint and independent effects of N-nitrosamines co-exposure on the risk of EC development. Lipidomics analysis was employed to screen differential lipid biomarkers in serum, and the mediating effects of key lipid metabolites in the association between nitrosamines exposure and EC were evaluated. After adjustment for confounders, N-nitrosodimethylamine (NDMA, 1.79 (95% CI: 1.35, 2.39)), N-nitrosodi-n-propylamine (NDPA, 1.55 (95%CI: 1.15, 2.09)), N-nitrosodiethylamine (NDEA, 1.82 (95%CI: 1.36, 2.45)), N-nitrosodibutylamine (NDBA, 1.60 (95%CI: 1.20, 2.13)), N-nitrosomethylethylamine (NMEA, 1.81 (95%CI: 1.36, 2.41)) and N-nitrosomorpholine (NMOR, 1.84 (95%CI: 1.38, 2.45)) exposure all elevated the risks of EC development. The Bayesian kernel machine regression (BKMR) with hierarchical variable selection showed significant positive joint associations of urinary NDMA, NDPA, NMOR, NDEA and EC development, when all nitrosamines were at the 55th percentiles or above, compared with the median. Lipidomic screening of serum samples from the stages of BCH, DYS and EC suggested the perturbation in the biosynthesis of unsaturated fatty acid metabolism pathway, of which myristic acid (FFA 14:0), palmitoleic acid (FFA 16:1), docosahexaenoic acid (FFA 22:6) exerted remarkable mediation effects in the association between N-nitrosamines exposure and EC development. These findings provided new sights for screening early lipid biomarkers and intervention targets in human EC.

Rapid green analytical methodology for simultaneous monitoring of nitrosamines and semi-volatile organic compounds in water and human urine samples

Nitrosamines and semi-volatile organic compounds (SVOCs) are carcinogenic contaminants in water and biological matrices. Conventional analytical methods often struggle to detect trace concentrations due to poor extraction efficacies. This study presents a novel, low-cost, in-syringe-assisted fast extraction cum cleanup technique coupled with GC-FID for monitoring four nitrosamines and two SVOCs in drinking water and human urine samples to measure the contamination and exposure levels. This extraction protocol combines a novel green in-syringe liquid-liquid extraction step using dimethyl carbonate as the green extraction solvent, coupled with a semi-automated solid-phase extraction cleanup process. Then, the final extractant is analyzed using gas chromatography-flame ionization detection (GC-FID) for monitoring. The method demonstrated excellent linearity (R2 > 0.998) between 1.5 and 500 ng mL⁻1 for all six target compounds. Detection limits ranged from 1.0 to 2.0 ng mL⁻1. Extraction recoveries were between 87 and 105% for both urine samples and water samples. Intra-day and inter-day precision were below 9% RSD. The blue applicability grade index evaluation scored 70.0, indicating good practical applicability. The developed analytical protocol offers a sensitive, accurate, low-cost, rapid, and environmentally friendly method for simultaneously quantifying multiple nitrosamines and SVOCs in environmental and human samples. Its performance characteristics and sustainability metrics suggest the potential for broad application in monitoring and exposure studies.

Analytical Methodologies to Detect N-Nitrosamine Impurities in Active Pharmaceutical Ingredients, Drug Products and Other Matrices

Since 2018, N-nitrosamine impurities have become a widespread concern in the global regulatory landscape of pharmaceutical products. This concern arises due to their potential for contamination, toxicity, carcinogenicity, and mutagenicity and their presence in many active pharmaceutical ingredients, drug products, and other matrices. N-Nitrosamine impurities in humans can lead to severe chemical toxicity effects. These include carcinogenic effects, metabolic disruptions, reproductive harm, liver diseases, obesity, DNA damage, cell death, chromosomal alterations, birth defects, and pregnancy loss. They are particularly known to cause cancer (tumors) in various organs and tissues such as the liver, lungs, nasal cavity, esophagus, pancreas, stomach, urinary bladder, colon, kidneys, and central nervous system. Additionally, N-nitrosamine impurities may contribute to the development of Alzheimer's and Parkinson's diseases and type-2 diabetes. Therefore, it is very important to control or avoid them by enhancing effective analytical methodologies using cutting-edge analytical techniques such as LC-MS, GC-MS, CE-MS, SFC, etc. Moreover, these analytical methods need to be sensitive and selective with suitable precision and accuracy, so that the actual amounts of N-nitrosamine impurities can be detected and quantified appropriately in drugs. Regulatory agencies such as the US FDA, EMA, ICH, WHO, etc. need to focus more on the hazards of N-nitrosamine impurities by providing guidance and regular updates to drug manufacturers and applicants. Similarly, drug manufacturers should be more vigilant to avoid nitrosating agents and secondary amines during the manufacturing processes. Numerous review articles have been published recently by various researchers, focusing on N-nitrosamine impurities found in previously notified products, including sartans, metformin, and ranitidine. These impurities have also been detected in a wide range of other products. Consequently, this review aims to concentrate on products recently reported to contain N-nitrosamine impurities. These products include rifampicin, champix, famotidine, nizatidine, atorvastatin, bumetanide, itraconazole, diovan, enalapril, propranolol, lisinopril, duloxetine, rivaroxaban, pioglitazones, glifizones, cilostazol, and sunitinib.

From detection methods to risk prevention: Control of N-nitrosamines in foods and the role of natural bioactive compounds

Food processing unavoidably introduces various risky ingredients that threaten food safety. N-Nitrosamines (NAs) constitute a class of food contaminants, which are considered carcinogenic to humans. According to the compiled information, pretreatment methods based on solid-phase extraction (SPE) were widely used before the determination of volatile NAs in foods. The innovation of adsorbents and hybridization of other methods have been confirmed as the future trends of SPE-based pretreatment methods. Moreover, technologies based on liquid chromatography and gas chromatography were popularly applied for the detection of NAs. Recently, sensor-based methods have garnered increasing attention due to their efficiency and flexibility. More portable sensor-based technologies are recommended for on-site monitoring of NAs in the future. The application of artificial intelligence can facilitate data processing during high-throughput detection of NAs. Natural bioactive compounds have been confirmed to be effective in mitigating NAs in foods through antioxidation, scavenging precursors, and regulating microbial activities. Meanwhile, they exhibit strong protective activities against hepatic damage, pancreatic cancer, and other NA injuries. Further supplementation of data on the bioavailability of bioactives can be achieved through encapsulation and clinical trials. The utilization of bioinformatics tools rooted in various omics technologies is suggested for investigating novel mechanisms and finally broadening their applications in targeted therapies.

Industrial effluents and N-nitrosamines in karst aquatic systems: a study on distribution and ecological implications

The discharge of electroplating wastewater, containing high concentrations of N-nitrosamines, poses significant risks to human health and aquatic ecosystems. Karst aquatic environment is easily impacted by N-nitrosamines due to the fragile surface ecosystem. However, it's still unclear in understanding N-nitrosamine transformation in karst water systems. To explore the response and transport of nine N-nitrosamines in electroplating effluent within both karst surface water and groundwater, different river and groundwater samples were collected from both the upper and lower reaches of the effluent discharge areas in a typical karst industrial catchment in Southwest China. Results showed that the total average concentrations of N-nitrosamines (∑NAs) in electroplating effluent (1800 ng/L) was significantly higher than that in the receiving river water (130 ng/L) and groundwater (70 ng/L). The dynamic nature of karst aquifers resulted in comparable average concentrations of ∑NAs in groundwater (70 ng/L) and river water (79 ng/L) at this catchment. Based on the principal component analysis and multiple linear regression analysis, the electroplating effluent contributed 89% and 53% of N-nitrosamines to the river water and groundwater, respectively. The results based on the species sensitivity distribution model revealed N-nitrosodibutylamine as a particularly toxic compound to aquatic organisms. Furthermore, the average N-nitrosamine carcinogenic risk was significantly higher in lower groundwater reaches compared to upper reaches. This study represents a pioneering effort in considering specific N-nitrosamine properties in evaluating their toxicity and constructing species sensitivity curves. It underscores the significance of electroplating effluent as a primary N-nitrosamine source in aquatic environments, emphasizing their swift dissemination and significant accumulation in karst groundwater.

A critical review of advances in tumor metabolism abnormalities induced by nitrosamine disinfection by-products in drinking water

Intensified sanitation practices amid the recent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak might result in the increased release of chloramine disinfectants into surface water, significantly promoting the formation of nitrosamine disinfection by-products (DBPs) in drinking water. Unfortunately, these nitrosamine DBPs exhibit significant genotoxic, carcinogenic, and mutagenic properties, whereas chlorinating disinfectants remain in global practice. The current review provides valuable insights into the occurrence, identification, contamination status, exposure limits, and toxicity of the new unregulated disinfection by-products (nitrosamine DBPs) in drinking water. As a result, concentrations of nitrosamine DBPs far exceed allowable limits in drinking water, and prolonged exposure has the potential to cause metabolic disorders, a critical step in tumor initiation and progression. Importantly, based on recent research, we have concluded the role of nitrosamines DBPs in different metabolic pathways. Remarkably, nitrosamine DBPs can induce chronic inflammation and initiate tumors by activating sphingolipid and polyunsaturated fatty acid metabolism. Regarding amino acid and nucleotide metabolism, nitrosamine DBPs can inhibit tryptophan metabolism and de novo nucleotide synthesis. Moreover, inhibition of de novo nucleotide synthesis fails to repair DNA damage induced by nitrosamines. Additionally, the accumulation of lactate induced by nitrosamine DBPs may act as a pivotal signaling molecule in communication within the tumor microenvironment. However, with the advancement of tumor metabolomics, understanding the role of nitrosamine DBPs in causing cancer by inducing metabolic abnormalities significantly lags behind, and specific mechanisms of toxic effects are not clearly defined. Urgently, further studies exploring this promising area are needed.

Functional UiO-66 for highly selective adsorption of N-nitrosodipropylamine: adsorption performance and mechanisms

N-Nitrosodipropylamine (NDPA) is a class of nitrogenous disinfection by-products (N-DBPs) with high toxicity. Although NDPA present in water bodies is at relatively low concentrations, the potential risk is high due to its high toxicity and bioaccumulation. Metal-organic frameworks (MOFs), a new type of porous material with remarkable functionality, have shown great performance in a wide variety of applications in adsorption. This is the first study investigating the adsorption of MOFs on NDPA. Herein, UiO-66 with -NH2 and imidazolium functional groups were synthesized by modifying UiO-66 after amination. Adsorption kinetics and isotherm models were used to compare the adsorption properties of the two materials for low-concentration NDPA in water. The results showed that the behavior of all the adsorbents was consistent with the Langmuir model and the pseudo-second-order model and that the adsorption was homogeneous chemisorption. The structures of the nanoparticles were characterized by FTIR, zeta potential, XRD, SEM and BET measurements. Based on the characteristics, four adsorption mechanisms, namely electron conjugation, coordination reaction, anion-π interaction, and van der Waals forces, were simultaneously involved in the adsorption. The influencing factor experiment revealed that the adsorption of UiO-66-NH2 and (I-)Meim-UiO-66 involved hydrogen bonding and electrostatic interactions, respectively.

Exploring the Interplay Between Vitamin B12-related Biomarkers, DNA Methylation, and Gene-Nutrition Interaction in Esophageal Precancerous Lesions

BACKGROUND

Vitamin B12 depletion has been suggested to be associated with esophageal precancerous lesions (EPL). However, the potential mechanisms remain unclear.

AIMS

This study aims to evaluate the role of vitamin B12 and its regulated epigenetic modification in EPL and provide preliminary information on the identification of potential molecular biomarkers for the early prediction of EPL.

METHODS

We collected information and samples from the Early Diagnosis and Early Treatment Project of Esophageal Cancer database from 200 EPL cases and 200 matched controls. Vitamin B12, one-carbon metabolism biomarkers, genetic polymorphism of TCN2 C776G, and DNA methylation were compared. Preliminarily identified candidate promoters of differentially methylated CpG positions were further verified by targeted bisulfite sequencing.

RESULTS

EPL cases had significantly lower serum levels of vitamin B12 and transcobalamin II, and higher serum levels of homocysteine and 5-methyltetrahydrofolate than controls. The TCN2 C776G polymorphism was found to be associated with susceptibility to EPL and may interact with vitamin B12 nutritional status to influence the risk of EPL in male subjects. In addition, global hypomethylation related to vitamin B12 depletion was observed in EPL cases, along with region-specific hypermethylation of UGT2B15 and FGFR2 promoters.

CONCLUSIONS

This study suggests that vitamin B12 depletion may be associated with aberrant DNA methylation and increased risk of EPL through the one-carbon metabolism pathway, presents that the TCN2 C776G polymorphism may interact with vitamin B12 nutritional status to affect EPL risk in males, and also identifies specific locations in the UGT2B15 and FGFR2 promoters with potential as promising molecular biomarkers.

Association between type of drinking water and upper gastrointestinal cancer incidence in the Linxian General Population

BACKGROUND

This study aimed to explore the association between drinking water source and risk of upper gastrointestinal (UGI) cancer, including esophageal cancer (EC) and gastric cancer (GC), in the Linxian General Population Nutrition Intervention Trial (NIT) cohort.

METHODS

In this study, we used data from the Linxian NIT cohort, which included 29,584 healthy adults aged 40 to 69 years. Subjects were enrolled in April 1986 and followed up until March 2016. Tap water drinking status and demographic characteristics were collected at baseline. Subjects who drank tap water were treated as the exposed group. Hazard ratios (HRs) and 95% confidence intervals (95% CIs) were estimated using the Cox proportional hazard model.

RESULTS

A total of 5,463 cases of UGI cancer were identified during the 30-year follow-up period. After adjusting for multiple factors, the incidence rate of UGI cancer in participants who drank tap water was significantly lower compared with individuals in the control (HR = 0.91, 95% CI: 0.86-0.97). A similar association was observed between tap water drinking and EC incidence (HR = 0.89, 95% CI: 0.82-0.97). The association between drinking tap water and risk of UGI cancer and EC incidence did not vary across the subgroup by age and gender (All Pinteraction > 0.05). For EC incidence, an interaction effect was observed for riboflavin/niacin supplements and drinking water source (Pinteraction = 0.03). No association was observed between drinking water source and GC incidence.

CONCLUSIONS

In this prospective cohort study in Linxian, participants who drank tap water had a lower risk of EC incidence. As a source of drinking water, use of tap water may reduce the risk of EC by avoiding exposure to nitrate/nitrite. Measures should be taken to improve the quality of drinking water in high-incidence areas of EC.

TRIAL REGISTRATION

The trial is registered with ClinicalTrials.gov (NCT00342654, 21/06/2006), and the trial name is Nutrition Intervention Trials in Linxian Follow-up Study.

Multi-omics analysis revealed NMBA induced esophageal carcinoma tumorigenesis via regulating PPARα signaling pathway

As widespread environmental carcinogens causing esophageal carcinoma (EC), the effects of N-nitrosamines on human health hazards and accurate toxicity mechanisms have not been well-elucidated. In this study, we explored the tumorigenic mechanism of N-nitrosomethylbenzylamine (NMBA) exposure using both cell and rat models. It was found that NMBA (2 μM) exposure for 26 weeks induced malignant transformation of normal esophageal epithelial (Het-1A) cells. After then proteomics analysis showed that lipid metabolism disorder predominantly participated in the process of NMBA-induced cell malignant transformation. Further the integrated proteomics and lipidomics analysis revealed that the enhancement of fatty acid metabolism promoted the EC tumorigenesis induced by NMBA through facilitating the fatty acid-associated PPARα signaling pathway. The animal studies also revealed that accelerated fatty acid decomposition in the progression of NMBA-induced EC models of rats was accompanied by the activation of the PPARα pathway. Overall, our findings depicted the key dynamic molecular alteration triggered by N-nitrosamines, and provided comprehensive biological perspectives into the carcinogenic risk assessment of N-nitrosamines.

Characteristics and health risk assessment of volatile N-nitrosamines in the plasma of adults in Guangdong Province, China

N-nitrosamines are strong carcinogens that are widely present in the environment. This study developed a method, and analyzed the concentrations of volatile N-nitrosamines (VNAs) in the plasma of adults in Guangdong Province, China. Finally, the health risks to adults in Guangdong Province, China, with dietary exposure to VNAs were assessed. Gas chromatography/mass spectrometry (GC/MS) in electron impact (EI) ionization source mode was used to quantitatively analyze VNAs, and to perform accurate mass determination. The lower limit of detection (LOD) of nine nitrosamines are ranged from 0.01 to 2.14 ng/mL. The recovery rate ranged from 83 % to 116 %, and the relative standard deviation (RSD) was < 10 %. The method developed is simple, rapid, and provides good reproducibility and high sensitivity. N-nitrosodimethylamine (NDMA), N-nitrosomethylethylamine (NMEA), N-nitrosodinbutylamine (NDBA), N-nitrosopiperidine (NPIP), N-nitrosopyrrolidine (NPYR), N-nitrosomorpholine (NMOR) and N-nitrosodiphenylamine (NDPhA) were detected in 92 adult plasma samples. NDMA and NMEA were detected in 56.5 % and 44.6 % of the samples, followed by NPIP (34.8 %). NDMA had the highest median concentration (43.7 ng/mL) in the total samples. There were gender-related differences found in the concentrations of NDBA and NDPhA. The exposure risk assessment results showed that the two highest daily dietary intakes of VNAs were N-nitrosodi-n-propylamine (NDPA) and NDMA, and aquatic products and pickled vegetables contributed the most total nitrosamine intake. The lifetime cancer risk of adults ranged from 2.88 × 10^-10 to 7.46 × 10^-5, and the risk associated with NDMA, NDPA, N-nitrosodiethylamine (NDEA), NMEA and NPIP are important and should attract more attention. This study aimed to explore the exposure levels of VNAs in the plasma of adults in Guangdong Province, China, and to assess the health risks of dietary intake of VNAs, which provides a basis of the effect of VNAs exposure on human health.

Seasonal variability, predictive modeling and health risks of N-nitrosamines in drinking water of Shanghai

The prevalence of carcinogenic N-nitrosamines in drinking water is of significant concern. In the present study, eight N-nitrosamines from three representative drinking water treatment plants (DWTPs) in Shanghai, China were monitored for an entire year to evaluate their seasonal variability, probabilistic cancer risk and the resulting disease burden. The possibility of employing routinely monitored water quality parameters as predictors of N-nitrosamines was also examined. The results showed that the Taipu River-fed reservoir suffered more serious N-nitrosamine contamination than the Yangtze River-fed reservoirs. Winter witnessed higher levels of N-nitrosamines in both source and finished water. N-nitrosamine concentrations increased from source water to finished water in autumn or winter, but no spatial variations were observed in summer. The total lifetime cancer risk (LCR) posed by N-nitrosamines in finished water was within the acceptable range (1.00 × 10^-6 to 1.00 × 10^-4), with N-nitrosodimethylamine (NDMA) and N-nitrosodiethylamine (NDEA) being the main contributors. Winter and autumn were found to have higher total LCR values. The average individual disability-adjusted life years (DALYs) lost was 4.43 × 10^-6 per person-year (ppy), exceeding the reference risk level (1.00 × 10^-6 ppy). Liver cancer accounted for 97.1 % of the total disease burden, while bladder and esophagus cancers made a little contribution (2.9 %). A multiple regression model was developed to estimate the total N-nitrosamines in finished water as a function of water quality parameters, and the R² value was 0.735. This study not only provides fundamental data for public health policy development, but also reveals the necessity to incorporate a seasonal control strategy in DWTPs to minimize the associated health risks induced by N-nitrosamines.

N-nitrosamines-mediated downregulation of LncRNA-UCA1 induces carcinogenesis of esophageal squamous by regulating the alternative splicing of FGFR2

Concerns are raised over the risk to digestive system's tumors from the N-nitrosamines (NAs) exposure in drinking water. Albeit considerable studies are conducted to explore the underlying mechanism responsible for NAs-induced esophageal squamous cell carcinoma (ESCC), the exact molecular mechanisms remain largely unknown, especially at the epigenetic regulation level. In this study, it is revealed that the urinary concentration of N-Nitrosodiethylamine is higher in high incidence area of ESCC, and the lncRNA-UCA1(UCA1) is significantly decreased in ESCC tissues. In vitro and in vivo experiments further show that UCA1 is involved in the malignant transformation of Het-1A cells and precancerous lesions of the rat esophagus induced by N-nitrosomethylbenzylamine (NMBzA). Functional gain and loss experiments verify UCA1 can affect the proliferation, migration, and invasion of ESCC cells in vitro and in vivo. Mechanically, through binding to heterogeneous nuclear ribonucleoprotein F (hnRNP F) protein, UCA1 regulates alternative splicing of fibroblast growth factor receptor 2 (FGFR2), which promotes the FGFR2IIIb isoform switching to FGFR2 IIIc isoform, and the latter activates epithelial-mesenchymal transition via PI3K-AKT signaling pathways impacting tumorigenesis. Therefore, NAs-mediated downregulation of UCA1 promotes ESCC progression through targeting hnRNP F/FGFR2/PI3k-AKT axis, which provides a new chemical carcinogenic target and establishes a previously unknown mechanism for NAs-induced ESCC.

Association between water source and chronic gastrointestinal diseases in Chinese: A cross-sectional and longitudinal study

Background

Gastrointestinal health is closely associated with the quality of the water supply. However, long-term associations between the water supply type and chronic gastrointestinal disease (CGD) are unclear.

Method

The water supply was categorized as "tap-water" or "non-tap water" use. Changes in water source use were categorized into four types: "non-tap water both at baseline and in follow-ups," "non-tap water at baseline and tap-water in follow-ups," "tap-water at baseline and non-tap water in follow-ups," or "tap-water at baseline and in follow-ups." We explored the association between tap-water use (and changes therein) and the risk of CGD in a cross-sectional and longitudinal population study based on national cohort data from 2011 to 2018.

Results

After the inclusion and exclusion process, 13,332 and 9,688 participants were included in the cross-sectional and longitudinal analyses, respectively. Tap-water use was associated with fewer CGD cases at baseline (OR = 0.98, 95% CI: 0.90, 1.07). Tap-water use at baseline was associated with significantly lower incidence of CGD in follow-ups (HR = 0.70, 95% CI: 0.70, 0.90). Compared with consistent non-tap water use in both baseline and follow-ups, switching from non-tap water to tap-water use in follow-ups was associated with a lower risk of CGD (HR = 0.79, 95% CI: 0.64, 0.97), tap water use at both baseline and in follow-ups was associated with a lower risk of CGD (HR = 0.72, 95% CI: 0.59, 0.88). The decreased risk of CGD followed a linear trend (P _fortrend < 0.01). Adjustment for indoor solid fuel use and outdoor air pollution exposure to PM_2.5 did not change the association between tap water use and CGD.

Conclusion

Tap water use was associated with a reduced risk of incident CGD. The results from this study should aid in effect assessment for water purification strategies and public decision support for gastrointestinal health management.

Research progress of N-nitrosamine detection methods: a review

N-Nitrosamines (nitrosamines) are attracting increased attention because of their high toxicity and wide distribution. They have been strictly restricted by regulations in many fields. Researchers around the world have conducted substantial work on nitrosamine detection. This paper reviews the progress of research on nitrosamine detection methods with emphasis on biological-matrix samples. After introducing the category, toxicity, regulatory limit and source of nitrosamines, the paper discusses the most commonly used sample-preparation techniques and instrumental-detection techniques for nitrosamine detection, including some typical application cases.

Rapid and selective determination of 9 nitrosamines in biological samples using ultra-high performance liquid chromatography-triple quadrupole linear ion trap mass spectrometry

A sensitive, selective and convenient method for the simultaneous determination of 9 nitrosamines (NAs) in biological samples was developed using isotope dilution ultra-high performance liquid chromatography-triple quadrupole linear ion trap mass spectrometry (UPLC-QTRAP-MS). Multiple reaction monitoring-information dependent acquisition-enhanced product ion (MRM-IDA-EPI) scan mode was performed to eliminate false positive results, and the whole detection procedure was characterized by less time consuming and simple sample preparation. 9 NAs were separated through a T3 column with the gradient elution of acetonitrile and water, and detected by UPLC-QTRAP-MS with an atmospheric pressure chemical ionization (APCI) source in the positive mode. The quantitative analysis was carried out via the isotope internal standard method with a matrix calibration curve. Under the optimized conditions, good linearity for the 9 NAs was achieved in the range of 0.2-20 μg L^-1 with correlation coefficients (r) higher than ≥0.9991, and the limits of detection and limits of quantitation were 0.02-0.1 μg L^-1 (S/N = 3) and 0.06-0.3 μg L^-1 (S/N = 10), respectively. Satisfactory recoveries ranging from 79.4% to 108.0% were obtained, and the precision of the proposed method, indicated by the relative standard deviations (RSDs), was 2.3-12.9%. The matrix effect study showed that NDMA, NMOR and NMEA presented a matrix suppression effect, NDPHA displayed a matrix enhancement effect, and the matrix effects of the other 5 analytes could be ignored. Real application of the developed method in 13 urine and 24 plasma samples demonstrated that NDBA, NPIP and NPYR occurred in both urine and plasma samples with the concentration of 0.038-0.60 μg L^-1, while other NAs were not detected. Such a method was sensitive and selective, and could be applied to the rapid qualitative and quantitative analysis of the 9 NAs in biological samples.

Identification of tissue-specific microbial profile of esophageal squamous cell carcinoma by full-length 16S rDNA sequencing

It was previously believed that the microbial community in the esophagus was relatively stable, but it has been reported that different esophageal diseases have different microbial community characteristics. In this study, we recruited patients with esophageal squamous cell carcinoma (ESCC) and collected 51 pairs of tumor and adjacent non-tumor tissues for full-length 16S rDNAsequencing and qPCR to compare the differences in microbial community structure. The results of sequencing in 19 pairs of tissues showed that Proteobacteria, Firmicutes, Bacteroidetes, Deinococcus-Thermus, and Actinobacteria were the main bacteria in tumor and adjacent non-tumor tissues. At the genus level, the bacteria with the highest relative proportion in tumor and adjacent non-tumor tissues were Streptococcus and Labrys, respectively. At the same time, it was observed that the complexity of microbial interactions in tumor tissues was weaker than that of adjacent non-tumor tissues. The results also found that the relative abundance of 24 taxa was statistically different between tumor and adjacent non-tumor tissues. The findings of qPCR in 32 pairs of tissues further evidence that the relative proportions of Blautia, Treponema, Lactobacillus murinus, Peptoanaerobacter stomatis, and Fusobacteria periodonticum were statistically different in tumor and adjacent non-tumor tissues. The findings of PIRCUSt2 indicated the lipopolysaccharide biosynthesis and biotin metabolism in the microbiome of cancer tissues are more significant. This study supplements the existing information on the structure, function, and interaction of microorganisms in the esophagus in situ and provides a direction for the further exploration of the relationship between esophageal in situ microorganisms and esophageal squamous cell carcinoma. KEY POINTS: • The structure of the microbial community in esophageal cancer tissue and adjacent non-tumor tissues at the phylum level is similar • Streptococcus and Labrys are the most important bacteria in esophageal tumor tissues and adjacent non-tumor tissues, respectively • Microbial interactions in tumor tissues are stronger than in adjacent non-tumor tissues.

Reactive oxygen species-mediated activation of NLRP3 inflammasome associated with pyroptosis in Het-1A cells induced by the co-exposure of nitrosamines

Nitrosamines were a class of important environmental carcinogens associated with digestive tract neoplasms. As the early toxic effect of nitrosamines, inflammatory response participated in the malignant transformation of cells and promoted the occurrence and development of tumors. However, the role of NLRP3 inflammasome in the nitrosamines-induced inflammatory response was unclear. In this study, the human esophageal epithelial cells (Het-1A) were used to explore potential mechanisms of the activation of NLRP3 inflammasome under co-exposure to nine nitrosamines commonly found in drinking water at the doses of 0, 4, 20, 100, 500, and 2500 ng/mL. The results showed that nitrosamines stimulated activation of the NLRP3 inflammasome and induced cellular oxidative damage in a dose-dependent manner. Pretreatment of reactive oxygen species scavenger N-acetyl-L-cysteine (NAC), particularly mitochondrial reactive oxygen species (mtROS) scavengers Mito-TEMPO, effectively inhibited the activation of NLRP3 inflammasome, suggesting that nitrosamines could mediate the activation of NLRP3 inflammasome via mtROS. Furthermore, we found that nitrosamines co-exposure also promoted cell pyroptosis through the NLRP3/caspase-1/GSDMD pathway, which was demonstrated by adding the caspase-1 inhibitor Z-YVAD-FMK and constructing NLRP3 downregulated Het-1A cell line. This study revealed the underlying mechanism of the activation of NLRP3 inflammasome initiated by nitrosamines co-exposure and provided new perspectives on the toxic effects of nitrosamines.

The dysregulation of unsaturated fatty acid-based metabolomics in the MNNG-induced malignant transformation of Het-1A cells

Studies have shown that environmental carcinogens exerted an important function in the high incidence of esophageal cancer (EC). Nitrosamines have been identified as important environmental carcinogens for EC. This study aimed to investigate the metabolic disturbances and new key toxicological markers in the malignant transformation process of normal esophageal epithelial cells (Het-1A) induced by MNNG (N-methyl-N'-nitro-N-nitrosoguanidine). Untargeted metabolomic and lipidomic profiling analysis by using ultra-high-performance liquid chromatography coupled with mass spectrometry (UHPLC-MS) were applied to explore the metabolic network alterations of Het-1A cells. The metabolomic results showed that significant alterations were observed in metabolic signatures between different generations (P5, P15, P25, P35) and the control cell group (P0). A total of 48 differential endogenous metabolites were screened and identified, mainly containing fatty acids, amino acids, and nucleotides. The differential metabolites were predominantly linked to the pathway of biosynthesis of unsaturated fatty acids metabolism. The cell lipidomic profiling revealed that the most differential lipids contained fatty acids (FAs), phosphatidylcholines (PC), phosphatidylethanolamines (PE), and phosphatidylserines (PS). The enrichment of the lipidomic pathway also confirmed that the lipid metabolism of biosynthesis of unsaturated fatty acids was the significant variation during the cell malignant transformation. Furthermore, we detected the expression of the upstream regulatory enzymes related to the unsaturated fatty acids to explore the regulation mechanism. The expression of stearoyl-CoA desaturase (SCD), ELOVL fatty acid elongase 1 (ELOVL1) promoted, and fatty acid desaturase 1 (FADS1) inhibited the key fatty acids of unsaturated fatty acids metabolism compared to the control cell group. Overall, our results revealed that lipid fatty acid metabolism was involved in the malignant transformation of Het-1A cells induced by MNNG and deepened the awareness of the carcinogenic mechanism of environmental exposure pollutants.

Dysregulation of fatty acid metabolism associated with esophageal inflammation of ICR mice induced by nitrosamines exposure

Nitrosamines, as ubiquitous environmental carcinogens with adverse impact on human health, were crucial inducers of esophageal cancer (EC). Esophageal inflammation (EI) was an important biological process and considered to be associated with the progression of EC. However, the underlying regulatory mechanism of EI process caused by nitrosamines exposure remained largely unclear. In this study, a metabolomics approach based on mass spectrometry was utilized to explore the effect of nitrosamines exposure to ICR mice. Also, the changes of pivotal metabolic enzyme levels, urinary nitrosamines and histopathological analysis were evaluated. The results showed that nitrosamines exposure was intimately interrelated with EI process in mice. Metabolomics profiling analysis indicated that nitrosamines caused significant alterations of metabolic pathway predominantly enriched in fatty acid metabolism. Targeted metabolomics analysis revealed that nitrosamines promoted decomposition of fatty acids and facilitated fatty acid β-oxidation (FAO) of mice. The significant increase of carnitine palmitoyltransferase 1 (CPT1) and downregulation of acetyl-CoA acyltransferase 2 (ACAA2) would promote FAO in EI process induced by nitrosamines. Additionally, the exposure levels of more than half of nitrosamines in urine were correlated with inflammatory fatty acid biomarkers. Overall, this study found that EI triggered by nitrosamines may be associated with the promotion of FAO, and provided novel insights for evaluating the underlying mechanism of environmental pollutant-caused toxicity based on metabolomics.

Metabolomics-based molecular signatures reveal the toxic effect of co-exposure to nitrosamines in drinking water

Nitrosamines, a group of emerging nitrogenous pollutants, are ubiquitously found in the drinking water system. However, less is known about how systemic biological responses resist or tolerate nitrosamines, especially long-term co-exposure at low concentrations. In this study, untargeted metabolomics was used to investigate the metabolic perturbations in human esophageal epithelial Het-1A cells induced by a mixture of nine common nitrosamines in drinking water at environmentally relevant, human-internal-exposure, and genotoxic concentrations. Generally, the disrupted metabolic spectrum became complicated with nitrosamines dose increasing. Notably, two inflammation-associated pathways, namely, cysteine (Cys) and methionine (MET) metabolism, and nicotinate and nicotinamide metabolism, changed significantly under the action of nitrosamines, even at the environmentally relevant level. Furthermore, targeted metabolomics and molecular biology indicators in cells were identified in mice synchronously. For one thing, the up-regulated Cys and MET metabolism provided methyl donors for histone methylation in the context of pro-inflammatory response. For another, the down-regulated NAD⁺/NADH ratio inhibited the deacetylation of NF-кB p65 and eventually activated the NF-кB signaling pathway. Taken collectively, the metabolomics molecular signatures were important indicative markers for nitrosamines-induced inflammation. The potential crosstalk between the inflammatory cascade and metabolic regulation also requires further studies. These findings suggest that more attention should be paid to long-term co-exposure at low concentrations in the control of nitrosamines pollution in drinking water. Additionally, this study also highlights a good prospect of the combined metabolomic-molecular biology approach in environmental toxicology.

Olive Leaf Extract (OLE) Addition as Tool to Reduce Nitrate and Nitrite in Ripened Sausages

Olive leaf extract (OLE) is known to be a source of phenolic compounds with antioxidant and antimicrobial activities. This study investigated the effects of the OLE addition to reduce nitrate/nitrite (NO) content on the physico-chemical features of ripened pork sausages. Seven formulations of pork sausages were set up: CTRL (0 mg/kg OLE; 300 mg/kg NO), Tr1 (200 mg/kg OLE; 150 mg/kg NO), Tr2 (400 mg/kg OLE; 150 mg/kg NO), Tr3 (800 mg/kg OLE; 150 mg/kg NO), Tr4 (200 mg/kg OLE; 0 mg/kg NO), Tr5 (400 mg/kg OLE; 0 mg/kg NO), and Tr6 (800 mg/kg OLE; 0 mg/kg NO). At the end of the ripening period, all the samples were within hygienic limits and the substitution of the additives with OLE allowed the reduction of NO residual contents. Both OLE and NO influenced the colour parameters. At the highest dose of OLE, both alone and in combination with reduced dose of NO, no significant differences in terms of moisture, pH, and aw were found compared to CTRL. In absence of NO, a significant reduction of weight loss was observed. Moreover, in the samples without NO a reduction of the hardness was detected. Finally, the oxidative stability test showed that the increase of the OLE amount prolonged the induction time.

Trends in Incidence and Mortality of Esophageal Cancer in Huai'an District, a High-Risk Area in Northern Jiangsu Province, China

PURPOSE

This study aimed to provide a clear comparable figure of the trends in incidence and mortality rates of esophageal cancer (EC) in Huai'an District, Huai'an City, Jiangsu Province, China, a high-risk area for EC.

METHODS

The data for age- and sex-specific incidence rates between 1998 and 2016, the mortality rates in 1990-2016 and the number of EC patients were obtained from Huai'an District Cancer Registry. Crude rates, Age-standardized rates (ASRs) by world standard population and truncated age-standardized rates of EC incidence and mortality were calculated. The joinpoint regression analysis was used to calculate the annual percent changes (APC), average annual percent changes (AAPC), and their 95% confidence intervals (CIs).

RESULTS

Overall, 20,892 new EC cases and 20,806 EC deaths were registered in Huai'an District. ASR of EC incidence from 1998 to 2016 and mortality from 1990 to 2016 were 73.32/100,000 and 60.03/100,000, respectively. The ASR illustrated that the incidence of EC had significant downward trends in total, male and female (AAPC = -4.65, -4.90, and -5.51, respectively, p <.01). The age-specific incidence and mortality rates of EC increased dramatically in people over the age of 40, and peaked in people between the ages 70-74. In the subdivisions of Huai'an District, geographical diversities in the crude incidence and mortality rates of EC were found.

CONCLUSION

In summary, the incidence and mortality rates of EC showed downward trends in Huai'an District. However, the burden of EC still remained serious in this high-risk area. Cost-effective methods of intervention and health education should be enhanced for improving EC prevention.

Cancer Etiology and Prevention Principle: "1 + X"

Cancer was previously thought to be an inevitable aspect of human health with no effective treatments. However, the results of in-depth cancer research suggest that most types of cancer may be preventable. Therefore, a comprehensive understanding of the disparities in cancer burden caused by different risk factors is essential to inform and improve cancer prevention and control. Here, we propose the cancer etiology and prevention principle "1 + X," where 1 denotes the primary risk factor for a cancer and X represents the secondary contributing risk factors for the cancer. We elaborate upon the "1 + X" principle with respect to risk factors for several different cancer types. The "1 + X" principle can be used for precise prevention of cancer by eliminating the main cause of a cancer and minimizing the contributing factors at the same time.

Occurrence and fate of N-nitrosamines in three full-scale drinking water treatment systems with different treatment trains

The occurrence of mutagenic and carcinogenic N-nitrosamines in drinking water is of great concern. In this study, dynamics and removal of nine N-nitrosamines in three drinking water treatment systems of a southern city of China are monitored during one year of sampling. The impacts of physicochemical treatment units on the removal and generation of N-nitrosamines were evaluated. The O₃ and KMnO₄ based pre-oxidation units have caused an increase in N-nitrosamines concentration, with O₃ showing the substantial generation of N-nitrosamines. The carbon filter and ultrafiltration membrane units were found effective in removing N-nitrosamine precursors. These drinking water treatment systems have been useful in removing N-nitrosamine precursors; meanwhile, a slight decrease was found in already formed N-nitrosamines concentration. However, N-nitrosomorpholine (NMOR) and N-nitrosodiphenylamine (NDPhA) were found resistant toward all kinds of physicochemical treatments, and negligible changes in concentration were noted in all drinking water treatment systems. The distribution networks in the city provided an effective contact period to residual chlorine and precursors, which caused an increase in N-nitrosamines concentration. Overall, N-nitrosodimethylamine (NDMA) and N-nitroso-diethylamine (NDEA) have been found near the cancer risk threshold (10^-6) in all of the drinking water treatment systems, while the remaining seven N-nitrosamines were found below the risk level.

Infection with Human Papillomavirus 18 Promotes Alkylating Agent-Induced Malignant Transformation in a Human Esophageal Cell Line

The relationship between human papillomavirus (HPV) and esophageal cancer (EC) has been controversial, which may be caused by the difference in geographic regions of sample origin. Thus, we conducted a case-control study to find that HPV increased the risk of esophageal cancer, and the HPV18 detection rate is the highest (24.2%) among patients with EC, suggesting that HPV18 could be the most risk subtype of HPV infected. We then identified high-risk HPV18 and N-methyl-N'-nitro-N-nitroso-guanidine (MNNG) to establish a model on the viral etiology cooperating with environmental carcinogens. Het-1A cells containing HPV18 were continuously exposed to MNNG or not; then the morphological phenotype and function assays were performed in 25th passage cells. MNNG promoted the proliferation and invasion abilities and inhibited apoptosis both in Het-1A-HPV18 and control group. However, the Het-1A-HPV18 had a stronger change in phenotypic features and formed more transformed foci in soft agar. Further, Western blot found p53 and p21 were down-regulated, and expression of c-Myc, MMP-2, and MMP-9 and Bcl-2/Bax ratio were up-regulated. Our results revealed that MNNG was easier to induce malignant transformation of Het-1A cells transfected with HPV18. It is good evidence for the close relationship between HPV and the etiology of EC, providing foundation for further study in molecular mechanism and specific intervention targets.

Machine Learning-Enabled Renal Cell Carcinoma Status Prediction Using Multiplatform Urine-Based Metabolomics

Renal cell carcinoma (RCC) is diagnosed through expensive cross-sectional imaging, frequently followed by renal mass biopsy, which is not only invasive but also prone to sampling errors. Hence, there is a critical need for a noninvasive diagnostic assay. RCC exhibits altered cellular metabolism combined with the close proximity of the tumor(s) to the urine in the kidney, suggesting that urine metabolomic profiling is an excellent choice for assay development. Here, we acquired liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) data followed by the use of machine learning (ML) to discover candidate metabolomic panels for RCC. The study cohort consisted of 105 RCC patients and 179 controls separated into two subcohorts: the model cohort and the test cohort. Univariate, wrapper, and embedded methods were used to select discriminatory features using the model cohort. Three ML techniques, each with different induction biases, were used for training and hyperparameter tuning. Assessment of RCC status prediction was evaluated using the test cohort with the selected biomarkers and the optimally tuned ML algorithms. A seven-metabolite panel predicted RCC in the test cohort with 88% accuracy, 94% sensitivity, 85% specificity, and 0.98 AUC. Metabolomics Workbench Study IDs are ST001705 and ST001706.

Determining the leading sources of N-nitrosamines and dissolved organic matter in four reservoirs in Southern China

The presence of carcinogenic N-nitrosamines and dissolved organic matter (DOM) in freshwater is a significant concern from the perspective of public health and drinking water treatment plant operation. This study investigated the N-nitrosamines concentration and their precursors' distributions, and DOM composition in four reservoirs located in a southern city of China. A total of 22 renowned precursors were identified. Precursors from industrial and pharmaceutical origins were found to be dominant in all reservoirs; however, traces of pesticide-based precursors, i.e. pirimicarb and cycluron were also found. The distribution of nine N-nitrosamines was substantially different among the reservoirs. N-Nitrosodibutylamine (NDBA), N-Nitrosopiperidine (NPIP), N-Nitrosodimethylamine (NDMA), and N-Nitrosopyrrolidine (NPYR) were abundantly present in all reservoirs. Most of N-nitrosamines except NDMA and N-nitrosodiethylamine (NDEA) were far below the generally accepted cancer risk of 10^-6, and NDMA/NDEA were found close to the risk level (10^-6). Anthropogenic DOM was dominant in three reservoirs as depicted by a higher biological index (BIX) than the humification index (HIX). By the principle component analysis, BIX appeared as an indicator of N-nitrosamines (except NDEA and NPIP). A strong and direct relationship was observed between the NDMA-formation potential (FP) and concentration of total N-nitrosamines (∑NA), and BIX. These results confirmed that the anthropogenic activities were the leading source of DOM and N-nitrosamines in this city based on land-use.

Occurrence of N-nitrosamines and their precursors in the middle and lower reaches of Yangtze River water

The presence of some types of N-nitrosamines in water bodies is of great concern worldwide due to their carcinogenic risks and harmful mutagenic effects on human health. In the present study, eight N-nitrosamines and their formation potentials (FPs) were primarily investigated in Yangtze River surface water to evaluate their spatial distribution, mass loads, and ecological risks. The results showed that of the eight N-nitrosamines investigated, NDMA (<1.5-17 ng/L), NDEA (<1.4-9.5 ng/L), NDPA (1.0 ng/L), NMOR (<1.0-1.3 ng/L), NPIP (<2.1-3.7 ng/L), and NDBA (<3.6-30 ng/L) were detected. The FPs of NDMA (<27-130 ng/L), NDEA (<0.9-2.3 ng/L), NDPA (<1.2-1.9 ng/L), NPYR (<1.4-2.9 ng/L), NMOR (<1.0 ng/L), and NDBA (<1.1-14 ng/L) were significantly identified. NDBA was predominantly observed in surface water, while NDMA was noticeably detected in chloraminated water samples. It was estimated that approximately 5.4 t/y of N-nitrosamines were carried by the Yangtze River to the East China Sea, whereas the input flux of N-nitrosamine precursors was estimated to be approximately 69.5 t/y. Spatial variations were observed due to the input of N-nitrosamines from the upstream dams and lakes. The origin of N-nitrosamine precursors was not associated with the presence of sediment in river water. NDEA could be introduced into river water by the discharge of wastewater. NDBA and its precursors could originate from industrial and aquaculture activities. NDMA and its precursors could result from both of the aforementioned sources. Moreover, the wastewater discharge from small cities, pH value, wastewater treatment ratio, and dilution could be the key factors that influence the occurrence of N-nitrosamines along the Yangtze River. More attention should be paid to the cancer risks posed by N-nitrosamines. The ecological risks posed by N-nitrosamines in the Yangtze River can be ignored.

Intake of volatile nitrosamines by Chinese residents in different provinces via food and drinking water

N-nitrosamines are potent carcinogens, particularly N-nitrosodimethylamine (NDMA) and N-nitrosodiethylamine (NDEA), which are commonly found in a variety of foods and drinking water. We calculated the food and drinking water intakes of NDMA, NDEA, and total volatile nitrosamines (TVNA) by Chinese residents in different provinces by multiplying the reported total diet study results by the nitrosamine contents in food and drinking water. The weighted content of nitrosamines in each category of foods and the concentration of nitrosamines in drinking water was obtained through literature review. The exogenous NDMA, NDEA and TVNA intakes of adult residents in 20 provinces ranged from 171 to 425 ng/d, 41 to 140 ng/d and 373 to 1028 ng/d, respectively. The main contributors to NDMA and TVNA intakes were vegetables, cereals, aquatic products, and meats while the main sources of NDEA intake were vegetables and cereals. The average total NDMA intake per capita in China (251 ng/d) was similar to that in Germany in 1991 (231 ng/d) but higher than that in the United States (136 ng/d), Canada (87.6 ng/d) and France (188 ng/d). Large differences in nitrosamine intakes were observed between the coastal provinces and inland provinces. Drinking water was estimated to contribute 13.1%, 1.3% and 10.8% of the exogenous intakes of NDMA, NDEA and TVNA, respectively. Based on our results, we recommend setting the NDMA drinking water criterion of 40 ng/L. Overall, this study presents basic information regarding nitrosamines intake via food and drinking water in China that will facilitate risk assessment, generation of health advisories and policy making.

Challenges for Safe and Healthy Drinking Water in China

PURPOSE OF REVIEW

Rapid economic growth and its huge population are putting tremendous pressure on water sustainability in China. Ensuring clean drinking water is a great challenge for public health due to water shortage and pollution. This article reviews current scientific findings on health-related issues on drinking water and discusses the challenges for safe and healthy drinking water in China.

RECENT FINDINGS

From literature published since 2010, a variety of emerging contaminants were detected in drinking water, including disinfection byproducts (DBPs), pharmaceuticals and personal care products (PPCPs), endocrine-disrupting compounds (EDCs), antibiotic resistance genes, and pathogens. Arsenic and fluoride are still the two major contaminants in groundwater. Microcystins, toxins produced by cyanobacteria, were also frequently detected in surface water for drinking. Health effects of exposure to arsenic, fluoride, nitrates, DBPs, and noroviruses in drinking water have been reported in several epidemiological studies. According to literature, water scarcity is still a severe ongoing issue, and regional disparity affects the access to safe and healthy drinking water. In addition, urbanization and climate change have strong influences on drinking water quality and water quantity. Multiple classes of contaminants of emerging concern have been detected in drinking water, while epidemiological studies on their health effects are still inadequate. Water scarcity, regional disparity, urbanization, and climate change are the major challenges for safe and healthy drinking water in China.

Synergism of HPV and MNNG repress miR-218 promoting Het-1A cell malignant transformation by targeting GAB2

Dysregulation of microRNAs (miRNAs) is induced during tumorigenesis. Our previous research suggested that HPV and MNNG led to malignant transformation of esophageal epithelial cells. To investigate the regulation and function of miR-218(miR-218-5p) during the malignant transformation of esophageal epithelial cells, we found miR-218 was inhibited synergistically by HPV and MNNG, suppressing cell proliferation, migration and invasion by up-regulating 3' untranslated region (3'UTR) GAB2 in Het-1A-HPV-MNNG cells (malignant Het-1A cells induced by HPV and MNNG). A negative correlation was found between miR-218 and GAB2 mRNA expression in esophageal cancer patients and control people. GAB2 was up-regulated in Het-1A-HPV-MNNG cells. Further, down-expression of GAB2 reversed HPV&MNNG-mediated activation of migration and invasion and repressed SHP2/ERK and Akt/mTOR pathway signaling. In conclusion, miR-218 partially accounts for the prevention effect during malignant transformation of normal esophageal epithelial cells, which targets GAB2, which supplies the potential treatment in cancer therapy.

Synergistic Carcinogenesis of HPV18 and MNNG in Het-1A Cells through p62-KEAP1-NRF2 and PI3K/AKT/mTOR Pathway

N-methyl-N´-nitro-N-nitrosoguanidine is a clear carcinogen, increasing evidence that indicates an etiological role of human papillomavirus in esophageal carcinoma. Studies have reported the synergistic effect on environmental carcinogens and viruses in recent years. On the basis of establishing the malignant transformation model of Het-1A cells induced by synergistic of HPV18 and MNNG, this study was to explore the synergistic carcinogenesis of MNNG and HPV. Our research indicated that HPV&MNNG led to a significant increase in the protein-expression levels of c-Myc, cyclinD1, BCL-2, BAX, E-cadherin, N-cadherin, mTOR, LC3II, and p62, with concomitant decreases in p21 and LC3I. HPV18 and MNNG induced accumulation of p62 and its interaction with KEAP1, which promoted NRF2 nuclear translocation. p62 loss prevents growth and increases autophagy of malignant cells by activating KEAP1/NRF2-dependent antioxidative response. In addition, PI3K and p-AKT were stimulated by HPV&MNNG, and PI3K/AKT/mTOR is positively associated with cell proliferation, migration, invasion, and autophagy during malignant transformation. Taken together, MNNG&HPV regulates autophagy and further accelerates cell appreciation by activating the p62/KEAP1/NRF2 and PI3K/AKT/mTOR pathway. MNNG&HPV may improve Het-1A cell autophagy to contribute to excessive cell proliferation, reduced apoptosis, and protection from oxidative damage, thus accelerating the process of cell malignant transformation and leading to cancerous cells.

Urinary exposure of N-nitrosamines and associated risk of esophageal cancer in a high incidence area in China

Esophageal cancer (EC) is a deadly malignancy worldwide with a high incidence and exhibits unevenly geographic prevalence, which suggests that environmental factors are deeply involved in the development of EC. Although the carcinogenesis of nitrosamines in the esophagus has been identified by tremendous toxicological data, the role of nitrosamines in the genesis of human EC has so far proved inconclusive largely due to a lack of convincing evidences. In this study, urinary nitrosamines in population controls and cases with esophageal precancerous lesions, including reflux esophagitis (RE) accompanying with basal cell hyperplasia (BCH) and dysplasia (DYS), and esophageal squamous cell carcinoma (ESCC) were detected by a SPE-LC-MS/MS method and the associated risk was evaluated. Higher excretion concentrations of N-nitrosomethylethylamine (NMEA) in the RE/BCH patients, NMEA and N-nitrosodibutylamine (NDBA) in the DYS patients, and NMEA, NDBA, N-nitrosopyrrolidine (NPyr) and N-nitrosomorpholine (NMor) in the ESCC patients were observed compared with the controls (p < .05). And with the progression of esophageal lesion, the exposure complexity increased in terms of the categories of nitrosamines. Furthermore, the observed positive associations between the hazardous exposure of NMEA, NDBA and NPyr and the increased risk of ESCC, and between NMEA and NDBA and RE/BCH were established. These findings provided direct evidence to support the hypothesis that exposure to nitrosamines are involved in the carcinogenesis of esophageal epithelia in this high incidence area from the perspective of endogenous exposure assessment. However, discoveries in this study need to be confirmed by systematic researches in the future. And the dose-response relationships, the reference ranges or cutoff values to predict the risks of nitrosamines exposure also need to be defined.

Spatial, temporal variability and carcinogenic health risk assessment of nitrosamines in a drinking water system in China

Nitrosamines, as a class of emerging frequently detected nitrogenous disinfection byproducts (N-DBPs) in drinking water, have gained increasing attention due to their potentially high health risk. Few studies focus on the occurrence variation and carcinogenic health risk of nitrosamines in drinking water systems. Our study aimed to investigate the spatial and temporal variability of nitrosamines in a drinking water system and to conduct a carcinogenic health risk assessment. Three types of water samples, including influent water, treated water and tap water, were collected monthly during an entire year in a drinking water system utilizing a combination of chlorine dioxide and chlorine in central China, and 9 nitrosamines were measured. The nitrosamine formation potentials (FPs) in influent water were also determined. N-nitrosodimethylamine (NDMA) was the most prevalent compound and was dominant in the water samples with average concentrations ranging from 2.5 to 67.4 ng/L, followed by N-nitrosodiethylamine (NDEA) and N-nitrosopiperidine (NPIP). Nitrosamine occurrence varied monthly, and significant seasonal differences were observed in tap water (p < .05). There were decreasing mean NDMA, NDEA and NPIP concentrations from influent water to treated water to tap water, but no significant spatial variability was observed within the water distribution system (p > .05). The average and 95th percentile total lifetime cancer risks for the three main nitrosamines were 4.83 × 10^-5 and 4.48 × 10^-4, respectively, exceeding the negligible risk level (10^-6) proposed by the USEPA. Exposure to nitrosamines in drinking water posed a higher cancer risk for children than for adults, and children aged 0.75 to 1 years suffered the highest cancer risk. These results suggest that nitrosamine occurrence in tap water varied temporally but not spatially. Exposure to drinking water nitrosamines may pose a carcinogenic risk to human health, especially to children.

Upper Gastrointestinal Cancer in China: Spatial Epidemiologic Evidence from Screening Areas

Upper gastrointestinal cancer (UGIC) including esophageal cancer and gastric cancer, which has been a significant burden in China. Few studies have explored the spatial pattern and association of incidence and mortality using nationwide data. This study aims to explore the spatial pattern and association of incidence and mortality between esophageal cancer and gastric cancer, and identify high-risk areas of the cancers to provide scientific evidence for tailoring endoscopic screening programs. We collected UGIC data in 2014 from a National Cancer Report, and then adopted methods of correlation analysis and spatial statistics to identify high-risk areas on the cancers and to explore the pattern. The results show a spatial autocorrelation on the spatial distribution of incidence and mortality of esophageal and gastric cancers, and the relative risks were from 2.52 (95% CI (confidence interval), 2.37-2.67; P < 0.001) to 3.80 (95% CI, 3.46-4.18; P < 0.001) in primary risk areas, respectively. Moreover, esophageal cancer shows an upward and then downward trend from west to east, and from south to north, yet gastric cancer exhibits an upward and then downward trend only from south to north. This study indicates habitants in overlapping risk areas have heavier cancer burdens, and suggests esophageal cancer and gastric cancer have a significant correlation. Therefore, more endoscopic screening attention should focus on overlapping risk areas.

Corn Flour Intake, Aflatoxin B1 Exposure, and Risk of Esophageal Precancerous Lesions in a High-Risk Area of Huai'an, China: A Case-Control Study

Aflatoxin B1 (AFB1), which has potent toxicity and carcinogenicity, is a common contaminant of important agricultural commodities. This study aimed to investigate the frequency of corn flour intake and assess the exposure to AFB1 via direct detection of AFB1 in the diet and serum AFB1 exposure biomarker, so as to evaluate their associations with the risk of esophageal precancerous lesions (EPL). A case-control study based on three-day duplicate diet samples was performed in Huai'an District. One hundred EPL cases and 100 healthy controls were enrolled and required to be age- (±2 years) and gender-matched. The concentration of AFB1 in food samples and the level of serum AFB1-albumin (AFB1-Alb) adduct were quantitatively analyzed. Results showed that corn flour intake was positively associated with serum AFB1-Alb adduct level (p for trend = 0.003), dietary AFB1 exposure (p for trend < 0.001), and the risk of EPL (p for trend = 0.017). Increased serum AFB1-Alb adduct level was associated with an increased risk of EPL as well (p for trend < 0.001). In conclusion, corn flour may be an essential source of AFB1 in Huai'an District, whereas high exposure to AFB1 is likely to be an important risk factor contributing to the progression of EPL.

Regional and Seasonal Distributions of N-Nitrosodimethylamine (NDMA) Concentrations in Chlorinated Drinking Water Distribution Systems in Korea

Volatile N-Nitrosamines (NAs), including N-nitrosodimethylamine (NDMA), an emerging contaminant in drinking water, have been reported to induce cancer in animal studies. This study aims to investigate the regional and seasonal distributions of the concentrations of NDMA, one of the most commonly found NAs with high carcinogenicity, in municipal tap water in Korea. NDMA in water samples was quantitatively determined using high-performance liquid chromatography-fluorescence detection (HPLC-FLD) as a 5-dimethylamino-1-naphthalenesulfonyl (dansyl) derivative after optimization to dry the SPE adsorbent and remove dimethylamine prior to derivatization. Tap water samples were collected from 41 sites in Korea, each of which was visited once in summer and once in winter. The average (±standard deviation) NDMA concentration among all the sites was 46.6 (±22.7) ng/L, ranging from <0.13 to 80.7 ng/L. Significant NDMA differences in the regions, excluding the Jeju region, were not found, whereas the average NDMA concentration was statistically higher in winter than in summer. A multiple regression analysis for the entire data set indicated a negative relationship between NDMA concentration and water temperature. High levels of NDMA in Korea may pose excessive cancer risks from the consumption of such drinking water.