Chemically-Induced DNA Damage, Mutagenesis, and Cancer

Evaluation of the probable synergistic toxicity of selected potentiated antiretroviral and antibiotics on some aquatic biomarker organisms

Environmental effects of active pharmaceutical compounds (APCs) in the environment are not well characterized, hence the need for comprehensive evaluation. This study employed three bioassays using three organisms, namely, Allium cepa, Daphnia magna, and Salmonella typhimurium, in the ecotoxicity study of lone and a mixture of selected APCs, namely, lamivudine (L), an antiretroviral, and ciprofloxacin (C) and sulfamethoxazole (S), antibiotics, at a concentration range between 10 and 100 ppb, in order to evaluate the potential of the lone and ternary mixture to exert synergistic toxicity. Study results from exposure to lone APCs showed that the L, C, and S trio individually had fatal impacts on daphnids, with mortality rates of 100, 75, and 95%, respectively, after 48 h. Sulfamethoxazole showed a mutagenic tendency, with a mutation ratio (background/sample ratio) of 2.0. Lamivudine showed a lethal impact on the root length of A. cepa (p > 0.05, p = 3.60E-3). Further microscopic examination of the A. cepa root tip revealed chromosomal aberrations on exposure to each compound. The LCS-mix ecotoxicology bioassays indicated a synergistic effect on the daphnids, probably due to potentiation. Although the LCS mix had a cytotoxic effect (evidenced by the absence of bacteria colonies) on exposed TA 98 P450 Salmonella typhimurium strain, this effect was not observed in other bacterial strains. Microscopic examination of A. cepa exposed to the LCS-mix revealed an aberration in the mitotic stage of the cell. The impact of combination of the pharmaceuticals in aqueous ecosystems was greater than when exposed to the tested individual pharmaceutical compounds. Study result showed that these compounds have tendencies to pose a higher risk to exposed living entities when in combined/potentiated forms, and this could lead to distortion of the regular functioning of the ecosystem, particularly bacterial and other microbial populations that are listed among primary producers of the aquatic food web.

The Expression Characteristics and Function of the RECQ Family in Pan-Cancer

BACKGROUND

The genes of the RECQ DNA helicase family play a part in preserving the stability of the genome and controlling different disease mechanisms. However, the expression features of RECQs in relation to pan-cancer, their correlation with the immune microenvironment of tumors, and the landscape of prognostic power are still undisclosed.

METHODS

Various sequence and clinical data extracted from 33 cancers were utilized to generate a comprehensive overview of RECQs in the landscape. Afterward, we discovered variations in gene expression, potential enrichment of functions, genetic alterations, and analysis related to the immune response in tumors. Additionally, we explored the clinical characteristics and diagnostic significance of RECQs. And the important association of RECQL4 with liver hepatocellular carcinoma (LIHC) was investigated.

RESULTS

RECQs exhibited extensive mutations in different types of cancers. The expression of RECQ may be influenced by an oncogenic mutation in certain types of cancer, resulting in the observed genomic and epigenetic changes in diverse tumor formations. Furthermore, RECQs originating from tumors exhibited a significant association with the immune microenvironment of the tumor, indicating their potential as promising targets for therapy. Patient prognosis was significantly associated with the majority of genes in the RECQ family. In LIHC, RECQL4 eventually emerged as a separate prognostic determinant.

CONCLUSIONS

To summarize, RECQs are essential for the regulation of the immune system in tumors, and RECQL4 serves as a prognostic indicator in LIHC. The results of our study offer fresh perspectives on RECQs from a bioinformatics perspective and emphasize the importance of RECQs in the diagnosis and treatment of cancer.

Resveratrol, Epigallocatechin Gallate and Curcumin for Cancer Therapy: Challenges from Their Pro-Apoptotic Properties

Plant-derived bioactive compounds are gaining wide attention for their multiple health-promoting activities and in particular for their anti-cancer properties. Several studies have highlighted how they can prevent cancer initiation and progression, improve the effectiveness of chemotherapy, and, in some cases, limit some of the side effects of chemotherapy agents. In this paper, we provide an update of the literature on the anti-cancer effects of three extensively studied plant-derived compounds, namely resveratrol, epigallocatechin gallate, and curcumin, with a special focus on the anti-cancer molecular mechanisms inducing apoptosis in the major types of cancers globally.

Modulation of redox homeostasis: A strategy to overcome cancer drug resistance

Cancer treatment is hampered by resistance to conventional therapeutic strategies, including chemotherapy, immunotherapy, and targeted therapy. Redox homeostasis manipulation is one of the most effective innovative treatment techniques for overcoming drug resistance. Reactive oxygen species (ROS), previously considered intracellular byproducts of aerobic metabolism, are now known to regulate multiple signaling pathways as second messengers. Cancer cells cope with elevated amounts of ROS during therapy by upregulating the antioxidant system, enabling tumor therapeutic resistance via a variety of mechanisms. In this review, we aim to shed light on redox modification and signaling pathways that may contribute to therapeutic resistance. We summarized the molecular mechanisms by which redox signaling-regulated drug resistance, including altered drug efflux, action targets and metabolism, enhanced DNA damage repair, maintained stemness, and reshaped tumor microenvironment. A comprehensive understanding of these interrelationships should improve treatment efficacy from a fundamental and clinical research point of view.

Intrinsic ROS Drive Hair Follicle Cycle Progression by Modulating DNA Damage and Repair and Subsequently Hair Follicle Apoptosis and Macrophage Polarization

Hair follicles (HFs) maintain homeostasis through the hair cycles; therefore, disrupting the hair cycle may lead to hair loss. Our previous study showed that apoptosis-inducing factor (AIF) nuclear translocation and poly [ADP-ribose] polymerase 1 (PARP1) upregulation induced apoptosis in mouse hair follicles during the hair cycle transition from anagen to catagen. However, the mechanism underlying this phenomenon remains unclear. In this study, we found that intrinsic ROS levels increased during the hair follicle cycle transition from anagen to catagen, followed by abrupt DNA breaks and activation of homologous recombinant and nonhomologous end joining DNA repair, along with the enhancement of apoptosis. Mice in different stages of the hair cycle were sacrificed, and the dorsal skins were collected. The results of western blot and histological staining indicated that AIF-PARP1 plays a key role in HF apoptosis, but their role in the regulation of the HF cycle is not clear. Mice were treated with inhibitors from anagen to catagen: treatment with BMN 673, a PARP1 inhibitor, increased DNA breaks and activated the cytochrome c/caspase-3-mediated apoptotic pathway, accelerating HF regression. Ac-DEVD-CHO (Ac), a caspase-3 inhibitor, attenuated HF degeneration by upregulating PARP1 expression, suggesting a seesaw relationship between cytochrome c-caspase-3- and AIF-PARP1-mediated apoptosis, wherein PARP1 may be the fulcrum. In addition, macrophages were involved in regulating the hair cycle, and the rate of M1 macrophages around HFs increased during catagen, while more M2 macrophages were found during anagen and telogen. Our results indicate that intrinsic ROS drive HF cycle progression through DNA damage and repair, followed by apoptosis. Intrinsic ROS drive hair follicle cycle progression by modulating DNA damage and repair, and consecutively, hair follicle apoptosis and macrophage polarization work together to promote the hair follicle cycle.

Diagnostic, Prognostic, and Immunological Roles of HELLS in Pan-Cancer: A Bioinformatics Analysis

Background

Inappropriate repair of DNA damage drives carcinogenesis. Lymphoid-specific helicase (HELLS) is an important component of the chromatin remodeling complex that helps repair DNA through various mechanisms such as DNA methylation, histone posttranslational modification, and nucleosome remodeling. Its role in human cancer initiation and progression has garnered recent attention. Our study aims to provide a more systematic and comprehensive understanding of the role of HELLS in the development and progression of multiple malignancies through analysis of HELLS in cancers.

Methods

We explored the role of HELLS in cancers using The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) database. Multiple web platforms and software were used for data analysis, including R, Cytoscape, HPA, Archs4, TISIDB, cBioPortal, STRING, GSCALite, and CancerSEA.

Results

High HELLS expression was found in a variety of cancers and differentially expressed across molecular and immune subtypes. HELLS was involved in many cancer pathways. Its expression positively correlated with Th2 and Tcm cells in most cancers. It also correlated with genetic markers of immunomodulators in various cancers.

Conclusions

Our study elucidates the role HELLS plays in promotion, inhibition, and treatment of different cancers. HELLS is a potential cancer diagnostic and prognostic biomarker with immune, targeted, or cytotoxic therapeutic value. This work is a prerequisite to clinical validation and treatment of HELLS in cancers.

DNA damage and cell apoptosis induced by fungicide difenoconazole in mouse mononuclear macrophage RAW264.7

Difenoconazole (DFC) is a typical triazole fungicide. Because of its effective bactericidal activity, it has been widely used in agricultural products such as fruits and vegetables. This study revealed the cytotoxic effect of fungicide DFC on mouse monocyte macrophage RAW264.7. The results showed that the IC₅₀ value of DFC on RAW264.7 cells was 37.08 μM (24 h). DFC can significantly inhibit the viability of RAW264.7 cells, induce DNA damage and enhance apoptosis. The established cytotoxicity test showed that DFC-induced DNA double strand breaks in RAW264.7 cells. DFC-treated cells showed typical morphological changes of apoptosis, including chromatin condensation and nuclear lysis. In addition, DFC can induce the release of Cyt c, promote the collapse of mitochondrial membrane potential and increase the Bax/Bcl-2 ratio in RAW264.7 cells. Through this research, people further understand the toxicity of DFC and provide a more scientific basis for its safety application and risk management.

Univariable and Multivariable Two-Sample Mendelian Randomization Investigating the Effects of Leisure Sedentary Behaviors on the Risk of Lung Cancer

Leisure sedentary behaviors (LSB) are widespread, and observational studies have provided emerging evidence that LSB play a role in the development of lung cancer (LC). However, the causal inference between LSB and LC remains unknown. Methods: We utilized univariable (UVMR) and multivariable two-sample Mendelian randomization (MVMR) analysis to disentangle the effects of LSB on the risk of LC. MR analysis was conducted with genetic variants from genome-wide association studies of LSB (408,815 persons from UK Biobank), containing 152 single-nucleotide polymorphisms (SNPs) for television (TV) watching, 37 SNPs for computer use, and four SNPs for driving, and LC from the International Lung Cancer Consortium (11,348 cases and 15,861 controls). Multiple sensitivity analyses were further performed to verify the causality. Results: UVMR demonstrated that genetically predisposed 1.5-h increase in LSB spent on watching TV increased the odds of LC by 90% [odds ratio (OR), 1.90; 95% confidence interval (CI), 1.44-2.50; p < 0.001]. Similar trends were observed for squamous cell lung cancer (OR, 1.97; 95%CI, 1.31-2.94; p = 0.0010) and lung adenocarcinoma (OR, 1.64; 95%CI 1.12-2.39; p = 0.0110). The causal effects remained significant after adjusting for education (OR, 1.97; 95%CI, 1.44-2.68; p < 0.001) and body mass index (OR, 1.86; 95%CI, 1.36-2.54; p < 0.001) through MVMR approach. No association was found between prolonged LSB spent on computer use and driving and LC risk. Genetically predisposed prolonged LSB was additionally correlated with smoking (OR, 1.557; 95%CI, 1.287-1.884; p < 0.001) and alcohol consumption (OR, 1.010; 95%CI, 1.004-1.016; p = 0.0016). Consistency of results across complementary sensitivity MR methods further strengthened the causality. Conclusion: Robust evidence was demonstrated for an independent, causal effect of LSB spent on watching TV in increasing the risk of LC. Further work is necessary to investigate the potential mechanisms.

Environmental Risk Characterization of an Antiretroviral (ARV) Lamivudine in Ecosystems

Antiretroviral drugs for the treatment of human immunodeficiency virus (HIV) and other viral infections are among the emerging contaminants considered for ecological risk assessment. These compounds have been reported to be widely distributed in water bodies and other aquatic environments, while data concerning the risk they may pose to unintended non-target species in a different ecosystem (environment) is scanty. In South Africa and other developing countries, lamivudine is one of the common antiretrovirals applied. Despite this, little is known about its environmental impacts as an emerging contaminant. The present study employed a battery of ecotoxicity bioassays to assess the environmental threat lamivudine poses to aquatic fauna and flora. Daphnia magna (filter feeders), the Ames bacterial mutagenicity test, Lactuca sativa (lettuce) germination test, and the Allium cepa root tip assay were conducted, testing lamivudine at two concentrations (10 and 100 µg/L), with environmental relevance. The Daphnia magna toxicity test revealed a statistically significant response (p << 0.05) with a mortality rate of 85% on exposure to 100 µg/L lamivudine in freshwater, which increased to 100% at 48-h exposure. At lower concentrations of 10 µg/L lamivudine, 90% and 55% survival rates were observed at 24 h and 48 h, respectively. No potential mutagenic effects were observed from the Ames test at both concentrations of lamivudine. Allium cepa bioassays revealed a noticeable adverse impact on the root lengths on exposure to 100 µg/L lamivudine. This impact was further investigated through microscopic examination, revealing some chromosomal aberration in the exposed Allium cepa root tips. The Lactuca sativa bioassay showed a slight adverse impact on both the germination rate of the seeds and their respective hypocotyl lengths compared to the control. Overall, this indicates that lamivudine poses an ecological health risk at different trophic levels, to both flora and fauna, at concentrations previously found in the environment.

Sequence-Specific Quantitation of Mutagenic DNA Damage via Polymerase Amplification with an Artificial Nucleotide

DNA mutations can result from replication errors due to different forms of DNA damage, including low-abundance DNA adducts induced by reactions with electrophiles. The lack of strategies to measure DNA adducts within genomic loci, however, limits our understanding of chemical mutagenesis. The use of artificial nucleotides incorporated opposite DNA adducts by engineered DNA polymerases offers a potential basis for site-specific detection of DNA adducts, but the availability of effective artificial nucleotides that insert opposite DNA adducts is extremely limited, and furthermore, there has been no report of a quantitative strategy for determining how much DNA alkylation occurs in a sequence of interest. In this work, we synthesized an artificial nucleotide triphosphate that is selectively inserted opposite O⁶-carboxymethyl-guanine DNA by an engineered polymerase and is required for DNA synthesis past the adduct. We characterized the mechanism of this enzymatic process and demonstrated that the artificial nucleotide is a marker for the presence and location in the genome of O⁶-carboxymethyl-guanine. Finally, we established a mass spectrometric method for quantifying the incorporated artificial nucleotide and obtained a linear relationship with the amount of O⁶-carboxymethyl-guanine in the target sequence. In this work, we present a strategy to identify, locate, and quantify a mutagenic DNA adduct, advancing tools for linking DNA alkylation to mutagenesis and for detecting DNA adducts in genes as potential diagnostic biomarkers for cancer prevention.

Ras-Mediated Activation of NF-κB and DNA Damage Response in Carcinogenesis

Cancer is a multi-step process during which cells acquire mutations that eventually lead to uncontrolled cell growth and division and evasion of programmed cell death. The oncogenes such as Ras and c-Myc may be responsible in all three major stages of cancer i.e., early, intermediate, and late. The NF-κB has been shown to control the expression of genes linked with tumor pathways such as chronic inflammation, tumor cell survival, anti-apoptosis, proliferation, invasion, and angiogenesis. In the last few decades, various biomarker pathways have been identified that play a critical role in carcinogenesis such as Ras, NF-κB and DNA damage.

Decreased DC-SIGNR expression in hepatocellular carcinoma predicts poor patient prognosis

Dendritic cell-specific intercellular adhesion molecule-grabbing non-integrin-related protein (DC-SIGNR) is a transmembrane receptor primarily involved in pathogen recognition by the innate immune system, with particular importance for viral recognition. DC-SIGNR may also be associated with tumorigenesis. The aim of the present study was to investigate the association between DC-SIGNR expression, development of hepatocellular carcinoma (HCC), and clinicopathological features. Immunohistochemistry was used to assess DC-SIGNR protein expression in HCC and paired non-cancerous tissue samples. DC-SIGNR expression was lower in HCC tissues compared with adjacent non-tumor tissue samples. The expression of DC-SIGNR was associated with small tumor size, low Edmondson grade and high patient long term survival rates. Bioinformatics analyses were performed on several datasets to assess the potential function of DC-SIGNR and related genes; the data revealed that DC-SIGNR mRNA expression was lower in HCC tissues compared with non-cancerous controls, and analyses of ten-year survival rates indicated patients with low DC-SIGNR expression exhibited shorter average survival times. In conclusion, decreased DC-SIGNR expression in HCC tissues may be a relevant predictive biomarker of clinical prognosis, in addition to being a viable therapeutic target for HCC treatment.

Nickel Carcinogenesis Mechanism: DNA Damage

Nickel (Ni) is known to be a major carcinogenic heavy metal. Occupational and environmental exposure to Ni has been implicated in human lung and nasal cancers. Currently, the molecular mechanisms of Ni carcinogenicity remain unclear, but studies have shown that Ni-caused DNA damage is an important carcinogenic mechanism. Therefore, we conducted a literature search of DNA damage associated with Ni exposure and summarized known Ni-caused DNA damage effects. In vitro and vivo studies demonstrated that Ni can induce DNA damage through direct DNA binding and reactive oxygen species (ROS) stimulation. Ni can also repress the DNA damage repair systems, including direct reversal, nucleotide repair (NER), base excision repair (BER), mismatch repair (MMR), homologous-recombination repair (HR), and nonhomologous end-joining (NHEJ) repair pathways. The repression of DNA repair is through direct enzyme inhibition and the downregulation of DNA repair molecule expression. Up to now, the exact mechanisms of DNA damage caused by Ni and Ni compounds remain unclear. Revealing the mechanisms of DNA damage from Ni exposure may contribute to the development of preventive strategies in Ni carcinogenicity.

Short-term and long-term exposure to hexavalent chromium alters 53BP1 via H3K18ac and H3K27ac

Hexavalent chromium (Cr(VI)) is a well-known human carcinogen and a strong oxidizer that causes severe DNA damage. However, the associations between epigenetic dysregulation and DNA damage have not been well-characterized. In this study, we evaluated the effects of short-term and long-term exposure to Cr(VI) in human bronchial epithelial (16HBE) cells. Then, we explored the role of epigenetic modification in Cr(VI)-induced DNA damage. We found that short- and long-term exposure to Cr(VI) induced DNA damage and reduced the expression 53BP1, but increased the expression of other DNA repair mediators. Short- and long-term exposure to Cr(VI) reduced the levels of H3K18ac and H3K27ac and reduced their enrichment at the promoter of 53BP1. Long-term Cr(VI) exposure resulted in multiple malignant characteristics including cell invasion, migration, and tumorgenicity. These data demonstrated that reduced H3K18ac and H3K27ac following Cr(VI) treatment contributed to the suppression of 53BP1. Our study demonstrated that epigenetic changes and DNA damage responses are involved in short-term toxicity and long-term carcinogenesis induced by Cr(VI).