The influence of genetic polymorphisms in XRCC3 and ADH5 genes on the frequency of genotoxicity biomarkers in workers exposed to formaldehyde

The interplay between XPG-Asp1104His polymorphism and reproductive risk factors elevates risk of breast cancer in Tanzanian women: A multiple interaction analysis

BACKGROUND

Reproductive history and genetics are well-known risk factors of breast cancer (BC). Little is known about how these factors interact to effect BC. This study investigated the association of ten polymorphisms in DNA repair genes with BC susceptibility in the Tanzanian samples and further analyzed the association between reproductive risk factors and disease risk METHODS: A hospital-based case-control study in 263 histopathological confirmed BC patients and 250 age-matched cancer-free controls was carried out. Allelic, genotypic, and haplotype association analyses were executed. Also, multifactor dimensionality reduction (MDR), and interaction dendrogram approaches were performed.

RESULTS

The frequency of genotypic and allelic variants of XRCC1-Arg399Gln (rs25487), XRCC2-Arg188His (rs3218536), XRCC3-Thr241Met (rs861539), XPG-Asp1104His (rs17655), and MSH2-Gly322Asp (rs4987188) were significantly different between the groups (p < 0.05). Moreover, XRCC1-Arg399Gln (rs25487), XRCC3-Thr241Met (rs861539), and XPG-Asp1104His (rs17655) were associated with the increased risk of BC in co-dominant, dominant, recessive, and additive genetic-inheritance models (p < 0.05). XRCC1-Arg/Gln genotype indicated a 3.1-fold increased risk of BC in pre-menopausal patients (p = 0.001) while XPG-His/His genotype showed a 1.2-fold increased risk in younger BC patients (<40 years) (p = 0.028). Asp/His+His/His genotypes indicated a 1.3-fold increased risk of BC in PR+ patients and a 1.1-fold decreased risk of BC in luminal-A patients (p = 0.014, p = 0.020, respectively). MDR analysis revealed a positive interaction between BC and the XPG-Asp1104His (rs17655) together with family history of cancer in the first-degree relatives. Dendrogram analysis indicated that the XPG-Asp1104His (rs17655) and family history of cancer in first-degree relatives were significantly synergistic and might be associated with an elevated risk of BC in Tanzania.

CONCLUSIONS

The XPG-Asp1104His (rs17655) might exert both independent and interactive effects on BC development in the Tanzanian women.

Applying genome-wide CRISPR to identify known and novel genes and pathways that modulate formaldehyde toxicity

Formaldehyde (FA), a ubiquitous environmental pollutant, is classified as a Group I human carcinogen by the International Agency for Research on Cancer. Previously, we reported that FA induced hematotoxicity and chromosomal aneuploidy in exposed workers and toxicity in bone marrow and hematopoietic stem cells of experimental animals. Using functional toxicogenomic profiling in yeast, we identified genes and cellular processes modulating eukaryotic FA cytotoxicity. Although we validated some of these findings in yeast, many specific genes, pathways and mechanisms of action of FA in human cells are not known. In the current study, we applied genome-wide, loss-of-function CRISPR screening to identify modulators of FA toxicity in the human hematopoietic K562 cell line. We assessed the cellular genetic determinants of susceptibility and resistance to FA at 40, 100 and 150 μM (IC10, IC20 and IC60, respectively) at two time points, day 8 and day 20. We identified multiple candidate genes that increase sensitivity (e.g. ADH5, ESD and FANC family) or resistance (e.g. FASN and KDM6A) to FA when disrupted. Pathway analysis revealed a major role for the FA metabolism and Fanconi anemia pathway in FA tolerance, consistent with findings from previous studies. Additional network analyses revealed potential new roles for one-carbon metabolism, fatty acid synthesis and mTOR signaling in modulating FA toxicity. Validation of these novel findings will further enhance our understanding of FA toxicity in human cells. Our findings support the utility of CRISPR-based functional genomics screening of environmental chemicals.

Formaldehído en ambientes laborales: revisión de la literatura y propuesta de vigilancia ocupacional

Introducción. El formaldehído es una sustancia ampliamente usada a nivel industrial; sin embargo, es considerada un agente mutagénico y carcinógeno para los humanos. Para determinar el grado de riesgo de los trabajadores ocupacionalmente expuestos (TOE) al formaldehído, debe hacerse un seguimiento de sus niveles de concentración ambiental y de los biomarcadores que permiten identificar su daño potencial para la salud. En Colombia, lamentablemente, no existen lineamientos respecto a la exposición ocupacional a esta sustancia.Objetivo.Revisar estudios recientes sobre exposición ocupacional a formaldehído para diseñar una estrategia de seguimiento y vigilancia de los TOE a esta sustancia en Colombia.Materiales y métodos. Se realizó una revisión de la literatura en PubMed, MedLine, ScienceDirect y Embase mediante la siguiente estrategia de búsqueda: artículos sobre exposición ocupacional a formaldehído publicados en inglés o español entre 2013 y 2017. Los términos de búsqueda fueron “occupational exposure”, “formaldehyde” “mutagenicity test” y “DNA adducts” y sus equivalentes en español.Resultados. La búsqueda inicial arrojó 103 registros, sin embargo solo 36 artículos cumplieron los criterios de inclusión establecidos.Conclusiones. La gestión adecuada del riesgo derivado de la exposición ocupacional a formaldehido, así como el seguimiento médico apropiado de estos trabajadores, requiere la implementación de una serie de acciones interdisciplinarias que permitan la creación de un sistema de vigilancia ocupacional integral de los TOE a esta sustancia. 

Genotoxic evaluation of occupational exposure to antineoplastic drugs

During the last years, several reports have provided evidence about adverse health effects on personal involved in Antineoplastic Drugs (ANPD) handling. ANPD has the ability to bind DNA, thus produce genotoxic damage. In this way, XRCC1 and XRCC3 proteins are necessary for efficient DNA repair and polymorphisms in this genes can be associated with an individual response to ANPD exposure. Therefore, the aim of this study was to evaluate genetic damage of occupational exposure to antineoplastic drugs and the possible effect of XRCC1 and XRCC3 polymorphisms in oncology employees from Bogotá, Colombia. Peripheral blood samples were obtained from 80 individuals, among exposed workers and healthy controls. The comet assay and Cytokinesis-block micronucleus cytome assay was performed to determinate genetic damage. From every sample DNA was isolated and genotyping for XRCC1 (Arg194Trp, Arg280His and Arg399Gln) and XRCC3 (Thr241Met) SNPs by PCR-RFLP. The exposed group showed a significant increase of comet assay results and micronucleus frequency, compared with unexposed group. It was observed a gender, exposure time and workplace effect on comet assay results. Our results showed no significant associations of comet assay results and micronucleus frequency with either genotype, allele, nor haplotype of XRCC1 and XRCC3 SNPs. The results suggest that occupational exposure to ANPD may lead to genotoxic damage and even be a risk to human health. To our knowledge, this is the first study to assess the genotoxic damage of occupational exposure to APND in South America.

Occupational exposure to formaldehyde and early biomarkers of cancer risk, immunotoxicity and susceptibility

Formaldehyde (FA) is a high-volume production chemical manufactured worldwide to which many people are exposed to both environmentally and occupationally. FA was recently reclassified as a human carcinogen. Several epidemiological studies have revealed an increased risk of cancer development among workers exposed to FA. Although FA genotoxicity was confirmed in a variety of experimental systems, data from human studies are conflicting. The aim of the present study was to evaluate the occupational exposure to FA in a multistage approach relating the exposure with different biomarkers (dose and effect) and individual susceptibility. Air monitoring was performed to estimate the level of exposure to FA during shift work. Eighty-five workers from hospital anatomy-pathology laboratories exposed to FA and 87 controls were tested for cytogenetic alterations in lymphocytes (micronucleus, MN; sister-chromatid exchange, SCE) and T-cell receptor (TCR) mutation assay. The frequency of MN in exfoliated buccal cells, a first contact tissue was also assessed. Percentages of different lymphocyte subpopulations were selected as immunotoxicity biomarkers. The level of formic acid in urine was investigated as a potential biomarker of internal dose. The effects of polymorphic genes of xenobiotic metabolising enzymes and DNA repair enzymes on the endpoints studied were determined. The mean level of FA exposure was 0.38 ± 0.03 ppm. MN (in lymphocytes and buccal cells) and SCE were significantly increased in FA-exposed workers compared to controls. MN frequency positively correlated with FA levels of exposure and duration. Significant alterations in the percentage of T cytotoxic lymphocytes, NK cells and B lymphocytes were found between groups. Polymorphisms in CYP2E1, GSTP1 and FANCA genes were associated with increased genetic damage in FA-exposed subjects. The obtained information may provide new important data to be used by health and safety care programs and by governmental agencies responsible for setting the acceptable levels for occupational exposure to FA.

Role of Macronutrients and Micronutrients in DNA Damage: Results From a Food Frequency Questionnaire

The links between diet and genomic instability have been under investigation for several decades, and evidence suggests a significant causal or preventive role for various dietary factors. This study investigates the influence of macronutrients (calories, protein, and glucides) and micronutrients, such as vitamins and minerals, as assessed by a food frequency questionnaire, on genotoxicity biomarkers measured by cytokinesis-blocked micronucleus assay and comet assay. The results found significant positive and negative correlations. Micronucleus frequency tends to increase with higher intake of caffeine, calcium, magnesium, zinc, and protein (P < .05, Spearman correlation). Calorie and omega-6 intakes are negatively correlated with DNA damage measured by the comet assay. These results are somewhat controversial because some of the correlations found are contrary to dominant views in the literature; however, we suggest that unraveling the association between diet and genetic instability requires a much better understanding of the modulating role of macronutrients and micronutrients.

Re-evaluation of the WHO (2010) formaldehyde indoor air quality guideline for cancer risk assessment

In 2010, the World Health Organization (WHO) established an indoor air quality guideline for short- and long-term exposures to formaldehyde (FA) of 0.1 mg/m3 (0.08 ppm) for all 30-min periods at lifelong exposure. This guideline was supported by studies from 2010 to 2013. Since 2013, new key studies have been published and key cancer cohorts have been updated, which we have evaluated and compared with the WHO guideline. FA is genotoxic, causing DNA adduct formation, and has a clastogenic effect; exposure-response relationships were nonlinear. Relevant genetic polymorphisms were not identified. Normal indoor air FA concentrations do not pass beyond the respiratory epithelium, and therefore FA's direct effects are limited to portal-of-entry effects. However, systemic effects have been observed in rats and mice, which may be due to secondary effects as airway inflammation and (sensory) irritation of eyes and the upper airways, which inter alia decreases respiratory ventilation. Both secondary effects are prevented at the guideline level. Nasopharyngeal cancer and leukaemia were observed inconsistently among studies; new updates of the US National Cancer Institute (NCI) cohort confirmed that the relative risk was not increased with mean FA exposures below 1 ppm and peak exposures below 4 ppm. Hodgkin's lymphoma, not observed in the other studies reviewed and not considered FA dependent, was increased in the NCI cohort at a mean concentration ≥0.6 mg/m3 and at peak exposures ≥2.5 mg/m3; both levels are above the WHO guideline. Overall, the credibility of the WHO guideline has not been challenged by new studies.

Aldehyde dehydrogenase 2 in aplastic anemia, Fanconi anemia and hematopoietic stem cells

Maintenance of the hematopoietic stem cell (HSC) compartment depends on the ability to metabolize exogenously and endogenously generated toxins, and to repair cellular damage caused by such toxins. Reactive aldehydes have been demonstrated to cause specific genotoxic injury, namely DNA interstrand cross-links. Aldehyde dehydrogenase 2 (ALDH2) is a member of a 19 isoenzyme ALDH family with different substrate specificities, subcellular localization, and patterns of expression. ALDH2 is localized in mitochondria and is essential for the metabolism of acetaldehyde, thereby placing it directly downstream of ethanol metabolism. Deficiency in ALDH2 expression and function are caused by a single nucleotide substitution and resulting amino acid change, called ALDH2*2. This genetic polymorphism affects 35-45% of East Asians (about ~560 million people), and causes the well-known Asian flushing syndrome, which results in disulfiram-like reactions after ethanol consumption. Recently, the ALDH2*2 genotype has been found to be associated with marrow failure, with both an increased risk of sporadic aplastic anemia and more rapid progression of Fanconi anemia. This review discusses the unexpected interrelationship between aldehydes, ALDH2 and hematopoietic stem cell biology, and in particular its relationship to Fanconi anemia.

Influence of Serum Levels of Vitamins A, D, and E as well as Vitamin D Receptor Polymorphisms on Micronucleus Frequencies and Other Biomarkers of Genotoxicity in Workers Exposed to Formaldehyde

BACKGROUND/AIM

Formaldehyde is classified as carcinogenic to humans, making it a major concern, particularly in occupational settings. Fat-soluble vitamins, such as vitamins A, D, and E, are documented as antigenotoxic and antimutagenic and also correlate with the cell antioxidant potential. This study investigates the influence of these vitamins on genotoxicity biomarkers of formaldehyde-exposed hospital workers.

METHODS

The target population were hospital workers exposed to formaldehyde (n = 55). Controls were nonexposed individuals (n = 80). The most used genotoxicity biomarkers were the cytokinesis-block micronucleus assay for lymphocytes and the micronucleus test for exfoliated buccal cells. Vitamins A and E were determined by high-performance liquid chromatography with a diode array detector (HPLC-DAD) and vitamin D receptor (VDR) polymorphisms by real-time PCR.

RESULTS

Significant correlations were found between genotoxicity biomarkers and between vitamins A and E in controls. Multiple regression showed that vitamin A was significantly associated with a higher mean of nucleoplasmic bridges (p < 0.001), and vitamin E was significantly associated with a decreased frequency of nuclear buds (p = 0.045) in the exposed group. No effect of vitamin D was observed. The VDRBsmI TT genotype carriers presented higher means of all the genotoxicity biomarkers; however, we found no significant associations.

CONCLUSIONS

The study suggests that vitamin levels may modulate direct signs of genotoxicity.

Association of the XPD and XRCC3 gene polymorphisms with oral squamous cell carcinoma in a Northeastern Brazilian population: A pilot study

OBJECTIVE

to evaluate the association between XPD and XRCC3 polymorphisms and oral squamous cell carcinoma (OSCC).

DESIGN

the sample consisted of 54 cases of OSCC and 40 cases of inflammatory fibrous hyperplasia (IFH). Genotypes were determined by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method.

RESULTS

XPD-Lys/Gln was more common in IFH (n=28; 70%) than in OSCC (n=24; 44.4%) (OR: 0.3; p<0.05). XPD-Gln was more frequent in high-grade lesions (0.48) than in low-grade lesions (0.21) (OR: 3.4; p<0.05). The Gln/Gln genotype was associated with III and IV clinical stages (OR: 0.07; p<0.05). XRCC3-Met was more frequent in OSCC (0.49) than in IFH (0.35) (OR: 2.6; p<0.05). The Met/Met genotype was associated with the presence of metastases (OR: 8.1; p<0.05) and with III and IV clinical stages (OR: 0.07; p<0.05).

CONCLUSIONS

in this sample, the frequency of XPD-Gln in IFH suggests that this variant may protect against OSCC. The presence of the XRCC3-Met allele seems to contribute to the development of OSCC, metastases and more advanced stages in these lesions.

Assessment of genotoxic effects in nurses handling cytostatic drugs

Several antineoplastic drugs have been classified as carcinogens by the International Agency for Research on Cancer (IARC) on the basis of epidemiological findings, animal carcinogenicity data, and outcomes of in vitro genotoxicity studies. 5-Fluorouracil (5-FU), which is easily absorbed through the skin, is the most frequently used antineoplastic agent in Portuguese hospitals and therefore may be used as an indicator of surface contamination. The aims of the present investigation were to (1) examine surface contamination by 5-FU and (2) assess the genotoxic risk using cytokinesis-block micronucleus assay in nurses from two Portuguese hospitals. The study consisted of 2 groups: 27 nurses occupationally exposed to cytostatic agents (cases) and 111 unexposed individuals (controls). Peripheral blood lymphocytes (PBL) were collected in order to measure micronuclei (MN) in both groups. Hospital B showed a higher numerical level of contamination but not significantly different from Hospital A. However; Hospital A presented the highest value of contamination and also a higher proportion of contaminated samples. The mean frequency of MN was significantly higher in exposed workers compared with controls. No significant differences were found among MN levels between the two hospitals. The analysis of confounding factors showed that age is a significant variable in MN frequency occurrence. Data suggest that there is a potential genotoxic damage related to occupational exposure to cytostatic drugs in oncology nurses.