Proteogenomics of Non-smoking Lung Cancer in East Asia Delineates Molecular Signatures of Pathogenesis and Progression.

Lung cancer in East Asia is characterized by a high percentage of never-smokers, early onset and predominant EGFR mutations. To illuminate the molecular phenotype of this demographically distinct disease, we performed a deep comprehensive proteogenomic study on a prospectively collected cohort in Taiwan, representing early stage, predominantly female, non-smoking lung adenocarcinoma. Integrated genomic, proteomic, and phosphoproteomic analysis delineated the demographically distinct molecular attributes and hallmarks of tumor progression. Mutational signature analysis revealed age- and gender-related mutagenesis mechanisms, characterized by high prevalence of APOBEC mutational signature in younger females and over-representation of environmental carcinogen-like mutational signatures in older females. A proteomics-informed classification distinguished the clinical characteristics of early stage patients with EGFR mutations. Furthermore, integrated protein network analysis revealed the cellular remodeling underpinning clinical trajectories and nominated candidate biomarkers for patient stratification and therapeutic intervention. This multi-omic molecular architecture may help develop strategies for management of early stage never-smoker lung adenocarcinoma.

An atlas of epithelial cell states and plasticity in lung adenocarcinoma.

Understanding the cellular processes that underlie early lung adenocarcinoma (LUAD) development is needed to devise intervention strategies1. Here we studied 246,102 single epithelial cells from 16 early-stage LUADs and 47 matched normal lung samples. Epithelial cells comprised diverse normal and cancer cell states, and diversity among cancer cells was strongly linked to LUAD-specific oncogenic drivers. KRAS mutant cancer cells showed distinct transcriptional features, reduced differentiation and low levels of aneuploidy. Non-malignant areas surrounding human LUAD samples were enriched with alveolar intermediate cells that displayed elevated KRT8 expression (termed KRT8+ alveolar intermediate cells (KACs) here), reduced differentiation, increased plasticity and driver KRAS mutations. Expression profiles of KACs were enriched in lung precancer cells and in LUAD cells and signified poor survival. In mice exposed to tobacco carcinogen, KACs emerged before lung tumours and persisted for months after cessation of carcinogen exposure. Moreover, they acquired Kras mutations and conveyed sensitivity to targeted KRAS inhibition in KAC-enriched organoids derived from alveolar type 2 (AT2) cells. Last, lineage-labelling of AT2 cells or KRT8+ cells following carcinogen exposure showed that KACs are possible intermediates in AT2-to-tumour cell transformation. This study provides new insights into epithelial cell states at the root of LUAD development, and such states could harbour potential targets for prevention or intervention.

The Dietary Supplement Chondroitin-4-Sulfate Exhibits Oncogene-Specific Pro-tumor Effects on BRAF V600E Melanoma Cells.

Dietary supplements such as vitamins and minerals are widely used in the hope of improving health but may have unidentified risks and side effects. In particular, a pathogenic link between dietary supplements and specific oncogenes remains unknown. Here we report that chondroitin-4-sulfate (CHSA), a natural glycosaminoglycan approved as a dietary supplement used for osteoarthritis, selectively promotes the tumor growth potential of BRAF V600E-expressing human melanoma cells in patient- and cell line-derived xenograft mice and confers resistance to BRAF inhibitors. Mechanistically, chondroitin sulfate glucuronyltransferase (CSGlcA-T) signals through its product CHSA to enhance casein kinase 2 (CK2)-PTEN binding and consequent phosphorylation and inhibition of PTEN, which requires CHSA chains and is essential to sustain AKT activation in BRAF V600E-expressing melanoma cells. However, this CHSA-dependent PTEN inhibition is dispensable in cancer cells expressing mutant NRAS or PI3KCA, which directly activate the PI3K-AKT pathway. These results suggest that dietary supplements may exhibit oncogene-dependent pro-tumor effects.

Early antitumor activity of oral Langerhans cells is compromised by a carcinogen.

Early diagnosis of oral squamous cell carcinoma (OSCC) remains an unmet clinical need. Therefore, elucidating the initial events of OSCC preceding tumor development could benefit OSCC prognosis. Here, we define the Langerhans cells (LCs) of the tongue and demonstrate that LCs protect the epithelium from carcinogen-induced OSCC by rapidly priming αßT cells capable of eliminating γH2AX+ epithelial cells, whereas γδT and natural killer cells are dispensable. The carcinogen, however, dysregulates the epithelial resident mononuclear phagocytes, reducing LC frequencies, while dendritic cells (DCs), macrophages, and plasmacytoid DCs (pDCs) populate the epithelium. Single-cell RNA-sequencing analysis indicates that these newly differentiated cells display an immunosuppressive phenotype accompanied by an expansion of T regulatory (Treg) cells. Accumulation of the Treg cells was regulated, in part, by pDCs and precedes the formation of visible tumors. This suggests LCs play an early protective role during OSCC, yet the capacity of the carcinogen to dysregulate the differentiation of mononuclear phagocytes facilitates oral carcinogenesis.

An update on the formation in tobacco, toxicity and carcinogenicity of N'-nitrosonornicotine and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone.

The tobacco-specific nitrosamines N'-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) are considered 'carcinogenic to humans' by the International Agency for Research on Cancer (IARC) and are believed to be important in the carcinogenic effects of both smokeless tobacco and combusted tobacco products. This short review focuses on the results of recent studies on the formation of NNN and NNK in tobacco, and their carcinogenicity and toxicity in laboratory animals. New mechanistic insights are presented regarding the role of dissimilatory nitrate reductases in certain microorganisms involved in the conversion of nitrate to nitrite that leads to the formation of NNN and NNK during curing and processing of tobacco. Carcinogenicity studies of the enantiomers of the major NNK metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and the enantiomers of NNN are reviewed. Recent toxicity studies of inhaled NNK and co-administration studies of NNK with formaldehyde, acetaldehyde, acrolein and CO2, all of which occur in high concentrations in cigarette smoke, are discussed.

Atypical genotoxicity of carcinogenic nickel(II): Linkage to dNTP biosynthesis, DNA-incorporated rNMPs, and impaired repair of TOP1-DNA crosslinks.

Cancer is a genetic disease requiring multiple mutations for its development. However, many carcinogens are DNA-unreactive and nonmutagenic and consequently described as nongenotoxic. One of such carcinogens is nickel, a global environmental pollutant abundantly emitted by burning of coal. We investigated activation of DNA damage responses by Ni and identified this metal as a replication stressor. Genotoxic stress markers indicated the accumulation of ssDNA and stalled replication forks, and Ni-treated cells were dependent on ATR for suppression of DNA damage and long-term survival. Replication stress by Ni resulted from destabilization of RRM1 and RRM2 subunits of ribonucleotide reductase and the resulting deficiency in dNTPs. Ni also increased DNA incorporation of rNMPs (detected by a specific fluorescent assay) and strongly enhanced their genotoxicity as a result of repressed repair of TOP1-DNA protein crosslinks (TOP1-DPC). The DPC-trap assay found severely impaired SUMOylation and K48-polyubiquitination of DNA-crosslinked TOP1 due to downregulation of specific enzymes. Our findings identified Ni as the human carcinogen inducing genome instability via DNA-embedded ribonucleotides and accumulation of TOP1-DPC which are carcinogenic abnormalities with poor detectability by the standard mutagenicity tests. The discovered mechanisms for Ni could also play a role in genotoxicity of other protein-reactive carcinogens.

Artificial intelligence uncovers carcinogenic human metabolites.

The genome of a eukaryotic cell is often vulnerable to both intrinsic and extrinsic threats owing to its constant exposure to a myriad of heterogeneous compounds. Despite the availability of innate DNA damage responses, some genomic lesions trigger malignant transformation of cells. Accurate prediction of carcinogens is an ever-challenging task owing to the limited information about bona fide (non-)carcinogens. We developed Metabokiller, an ensemble classifier that accurately recognizes carcinogens by quantitatively assessing their electrophilicity, their potential to induce proliferation, oxidative stress, genomic instability, epigenome alterations, and anti-apoptotic response. Concomitant with the carcinogenicity prediction, Metabokiller is fully interpretable and outperforms existing best-practice methods for carcinogenicity prediction. Metabokiller unraveled potential carcinogenic human metabolites. To cross-validate Metabokiller predictions, we performed multiple functional assays using Saccharomyces cerevisiae and human cells with two Metabokiller-flagged human metabolites, namely 4-nitrocatechol and 3,4-dihydroxyphenylacetic acid, and observed high synergy between Metabokiller predictions and experimental validations.

Quantum Mechanical Assessment of Nitrosamine Potency.

Nitrosamines are in the cohort of concern (CoC) as determined by regulatory guidance. CoC compounds are considered highly potent carcinogens that need to be limited below the threshold of toxicological concern, 1.5 µg/day. Nitrosamines like NDMA and NDEA require strict control, while novel nitrosamine drug substance-related impurities (NDSRIs) may or may not be characterized as potent carcinogens. A risk assessment based on the structural features of NDSRIs is important in order to predict potency because they lack substance-specific carcinogenicity. Herein, we present a quantum mechanical (QM)-based analysis on structurally diverse sets of nitrosamines to better understand how structure influences the reactivity that could result in carcinogenicity. We describe the potency trend through activation energies corresponding to α-hydroxylation, aldehyde formation, diazonium intermediate formation, reaction with DNA base, and hydrolysis reactions, and other probable metabolic pathways associated with the carcinogenicity of nitrosamines. We evaluated activation energies for selected cases such as N-nitroso pyrrolidines, N-nitroso piperidines, N-nitroso piperazines, N-nitroso morpholines, N-nitroso thiomorpholine, N-methyl nitroso aromatic, fluorine-substituted nitrosamines, and substituted aliphatic nitrosamines. We compare these results to the recent framework of the carcinogenic potency characterization approach (CPCA) proposed by health authorities which is meant to give guidance on acceptable intakes (AI) for NDSRIs lacking substance-specific carcinogenicity data. We show examples where QM modeling and CPCA are aligned and examples where CPCA both underestimates and overestimates the AI. In cases where CPCA predicts high potency for NDSRIs, QM modeling can help better estimate an AI. Our results suggest that a combined mechanistic understanding of α-hydroxylation, aldehyde formation, hydrolysis, and reaction with DNA bases could help identify the structural features that underpin the potency of nitrosamines. We anticipate this work will be a valuable addition to the CPCA and provide a more analytical way to estimate AI for novel NDSRIs.

Tissue Organoid Cultures Metabolize Dietary Carcinogens Proficiently and Are Effective Models for DNA Adduct Formation.

Human tissue three-dimensional (3D) organoid cultures have the potential to reproduce in vitro the physiological properties and cellular architecture of the organs from which they are derived. The ability of organoid cultures derived from human stomach, liver, kidney, and colon to metabolically activate three dietary carcinogens, aflatoxin B1 (AFB1), aristolochic acid I (AAI), and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), was investigated. In each case, the response of a target tissue (liver for AFB1; kidney for AAI; colon for PhIP) was compared with that of a nontarget tissue (gastric). After treatment cell viabilities were measured, DNA damage response (DDR) was determined by Western blotting for p-p53, p21, p-CHK2, and γ-H2AX, and DNA adduct formation was quantified by mass spectrometry. Induction of the key xenobiotic-metabolizing enzymes (XMEs) CYP1A1, CYP1A2, CYP3A4, and NQO1 was assessed by qRT-PCR. We found that organoids from different tissues can activate AAI, AFB1, and PhIP. In some cases, this metabolic potential varied between tissues and between different cultures of the same tissue. Similarly, variations in the levels of expression of XMEs were observed. At comparable levels of cytotoxicity, organoids derived from tissues that are considered targets for these carcinogens had higher levels of adduct formation than a nontarget tissue.

Mechanisms of Nitrosamine Mutagenicity and Their Relationship to Rodent Carcinogenic Potency.

A thorough literature review was undertaken to understand how the pathways of N-nitrosamine transformation relate to mutagenic potential and carcinogenic potency in rodents. Empirical and computational evidence indicates that a common radical intermediate is created by CYP-mediated hydrogen abstraction at the α-carbon; it is responsible for both activation, leading to the formation of DNA-reactive diazonium species, and deactivation by denitrosation. There are competing sites of CYP metabolism (e.g., ß-carbon), and other reactive species can form following initial bioactivation, although these alternative pathways tend to decrease rather than enhance carcinogenic potency. The activation pathway, oxidative dealkylation, is a common reaction in drug metabolism and evidence indicates that the carbonyl byproduct, e.g., formaldehyde, does not contribute to the toxic properties of N-nitrosamines. Nitric oxide (NO), a side product of denitrosation, can similarly be discounted as an enhancer of N-nitrosamine toxicity based on carcinogenicity data for substances that act as NO-donors. However, not all N-nitrosamines are potent rodent carcinogens. In a significant number of cases, there is a potency overlap with non-N-nitrosamine carcinogens that are not in the Cohort of Concern (CoC; high-potency rodent carcinogens comprising aflatoxin-like-, N-nitroso-, and alkyl-azoxy compounds), while other N-nitrosamines are devoid of carcinogenic potential. In this context, mutagenicity is a useful surrogate for carcinogenicity, as proposed in the ICH M7 (R2) (2023) guidance. Thus, in the safety assessment and control of N-nitrosamines in medicines, it is important to understand those complementary attributes of mechanisms of mutagenicity and structure-activity relationships that translate to elevated potency versus those which are associated with a reduction in, or absence of, carcinogenic potency.

Long Noncoding RNA PSMB8-AS1 Mediates the Tobacco-Carcinogen-Induced Transformation of a Human Bronchial Epithelial Cell Line by Regulating Cell Cycle.

Lung cancer is the main cause of cancer deaths around the world. Nitrosamine 4-(methyl nitrosamine)-1-(3-pyridyl)-1-butanone (NNK) is a tobacco-specific carcinogen of lung cancer. Abundant evidence implicates long noncoding RNAs (lncRNAs) in tumorigenesis. Yet, the effects and mechanisms of lncRNAs in NNK-induced carcinogenesis are still unclear. In this study, we discovered that NNK-induced transformed Beas-2B cells (Beas-2B-NNK) showed increased cell migration and proliferation while decreasing rates of apoptosis. RNA sequencing and differentially expressed lncRNAs analyses showed that lncRNA PSMB8-AS1 was obviously upregulated. Interestingly, silencing the lncRNA PSMB8-AS1 in Beas-2B-NNK cells reduced cell proliferation and migration and produced cell cycle arrest in the G2/M phase along with a decrease in CDK1 expression. Conclusively, our results demonstrate that lncRNA PSMB8-AS1 could promote the malignant characteristics of Beas-2B-NNK cells by regulating CDK1 and affecting the cell cycle, suggesting that it may supply a new prospective epigenetic mechanism for lung cancer.

Multi-endpoint analysis of cadmium chloride-induced genotoxicity shows role for reactive oxygen species and p53 activation in DNA damage induction, cell cycle irregularities, and cell size aberrations.

Cadmium chloride (CdCl2) is a known genotoxic carcinogen, with a mechanism of action thought to partly involve the generation of reactive oxygen species (ROS). We applied here a multi-endpoint approach in vitro to explore the impact of CdCl2 on both the genome and on wider cell biology pathways relevant to cancer. Multi-endpoint approaches are believed to offer greater promise in terms of understanding the holistic effects of carcinogens in vitro. This richer understanding may help better classification of carcinogens as well as allowing detailed mechanisms of action to be identified. We found that CdCl2 caused DNA damage [micronuclei (MN)] in both TK6 and NH32 cells in a dose-dependent manner after 4 h exposure (plus 23 h recovery), with lowest observable effect levels (LOELs) for MN induction of 1 µM (TK6) and 1.6 µM (NH32). This DNA damage induction in TK6 cells was ROS dependent as pretreatment with the antioxidant N-Acetyl Cysteine (1 mM), abrogated this effect. However, 2',7'-dichlorofluorescin diacetate was not capable of detecting the ROS induced by CdCl2. The use of NH32 cells allowed an investigation of the role of p53 as they are a p53 null cell line derived from TK6. NH32 showed a 10-fold increase in MN in untreated cells and a similar dose-dependent effect after CdCl2 treatment. In TK6 cells, CdCl2 also caused activation of p53 (accumulation of total and phosphorylated p53), imposition of cell cycle checkpoints (G2/M) and intriguingly the production of smaller and more eccentric (elongated) cells. Overall, this multi-endpoint study suggests a carcinogenic mechanism of CdCl2 involving ROS generation, oxidative DNA damage and p53 activation, leading to cell cycle abnormalities and impacts of cell size and shape. This study shows how the integration of multiple cell biology endpoints studied in parallel in vitro can help mechanistic understanding of how carcinogens disrupt normal cell biology.

Ames test study designs for nitrosamine mutagenicity testing: qualitative and quantitative analysis of key assay parameters.

The robust control of genotoxic N-nitrosamine (NA) impurities is an important safety consideration for the pharmaceutical industry, especially considering recent drug product withdrawals. NAs belong to the 'cohort of concern' list of genotoxic impurities (ICH M7) because of the mutagenic and carcinogenic potency of this chemical class. In addition, regulatory concerns exist regarding the capacity of the Ames test to predict the carcinogenic potential of NAs because of historically discordant results. The reasons postulated to explain these discordant data generally point to aspects of Ames test study design. These include vehicle solvent choice, liver S9 species, bacterial strain, compound concentration, and use of pre-incubation versus plate incorporation methods. Many of these concerns have their roots in historical data generated prior to the harmonization of Ames test guidelines. Therefore, we investigated various Ames test assay parameters and used qualitative analysis and quantitative benchmark dose modelling to identify which combinations provided the most sensitive conditions in terms of mutagenic potency. Two alkyl-nitrosamines, N-nitrosodimethylamine (NDMA) and N-nitrosodiethylamine (NDEA) were studied. NDMA and NDEA mutagenicity was readily detected in the Ames test and key assay parameters were identified that contributed to assay sensitivity rankings. The pre-incubation method (30-min incubation), appropriate vehicle (water or methanol), and hamster-induced liver S9, alongside Salmonella typhimurium strains TA100 and TA1535 and Escherichia coli strain WP2uvrA(pKM101) provide the most sensitive combination of assay parameters in terms of NDMA and NDEA mutagenic potency in the Ames test. Using these parameters and further quantitative benchmark dose modelling, we show that N-nitrosomethylethylamine (NMEA) is positive in Ames test and therefore should no longer be considered a historically discordant NA. The results presented herein define a sensitive Ames test design that can be deployed for the assessment of NAs to support robust impurity qualifications.

An integrated in vitro carcinogenicity test that distinguishes between genotoxic carcinogens, non-genotoxic carcinogens, and non-carcinogens.

Chemical safety testing plays a crucial role in product and pharmacological development, as well as chemoprevention; however, in vitro genotoxicity safety tests do not always accurately predict the chemicals that will be in vivo carcinogens. If chemicals test positive in vitro for genotoxicity but negative in vivo, this can contribute to unnecessary testing in animals used to confirm erroneous in vitro positive results. Current in vitro tests typically evaluate only genotoxicity endpoints, which limits their potential to detect non-genotoxic carcinogens. The frequency of misleading in vitro positive results can be high, leading to a requirement for more informative in vitro tests. It is now recognized that multiple-endpoint genotoxicity testing may aid more accurate detection of carcinogens and non-carcinogens. The objective of this review was to evaluate the utility of our novel, multiple-endpoint in vitro test, which uses multiple cancer-relevant endpoints to predict carcinogenic potential. The tool assessed micronucleus frequency, p53 expression, p21 expression, mitochondrial respiration, cell cycle abnormalities and, uniquely, cell morphology changes in human lymphoblastoid cell lines, TK6 and MCL-5. The endpoints were used to observe cellular responses to 18 chemicals within the following categories: genotoxic carcinogens, non-genotoxic carcinogens, toxic non-carcinogens, and misleading in vitro positive and negative agents. The number of endpoints significantly altered for each chemical was considered, alongside the holistic Integrated Signature of Carcinogenicity score, derived from the sum of fold changes for all endpoints. Following the calculation of an overall score from these measures, carcinogens exhibited greater potency than non-carcinogens. Genotoxic carcinogens were generally more potent than non-genotoxic carcinogens. This novel approach therefore demonstrated potential for correctly predicting whether chemicals with unknown mechanism may be considered carcinogens. Overall, while further validation is recommended, the test demonstrates potential for the identification of carcinogenic compounds. Adoption of the approach could enable reduced animal use in carcinogenicity testing.

Talc and human cancer: a systematic review of the experimental animal and mechanistic evidence.

The potential carcinogenicity of talc has been evaluated in many studies in humans and experimental animals published in the scientific literature over the last several decades, with a number of these studies reporting no associations between talc exposure and any type of cancer. In order to fully understand the current state of the science regarding the potential for talc to induce human cancers, we conducted a comprehensive and systematic review of the available experimental animal and mechanistic evidence (in conjunction with a systematic review of the epidemiology evidence in a companion analysis) to evaluate whether it supports talc as being carcinogenic to humans. We considered study quality and its impact on the interpretation of results and evaluated all types of cancer and all exposure routes. We also evaluated the evidence on the potential for talc to migrate in the body to potential tumor sites. We identified seven experimental animal carcinogenicity studies and 11 mechanistic studies of talc to systematically review. We found that several of the experimental animal carcinogenicity studies of talc have limitations that preclude their sensitivity to detect increases in tumor incidence. Regardless, the studies cover multiple exposure routes, species, and exposure durations, and none indicate that talc is a carcinogen in experimental animals except in rats under conditions of extremely high exposure that likely resulted in lung particle overload, a nonspecific effect of high exposures to poorly soluble particles, and not from any carcinogenic properties of talc. Lung particle overload leading to lung tumor formation has only been observed in rats and not in any other species, including humans. The mechanistic studies indicate that talc is not genotoxic or mutagenic, but can induce some effects that could be events on a possible pathway to carcinogenicity, mainly at high exposures or in in vitro studies with exposures of unclear relevance in vivo, but these effects are not consistent across studies and cell types. This systematic review of the experimental animal carcinogenicity and mechanistic evidence for talc indicates that an association between talc exposure and cancer is not expected in humans. Talc carcinogenicity is not plausible in any species except rats, and only when the exposure conditions are high enough to induce lung particle overload, which is not relevant to human exposures.

A systematic review of the epidemiology evidence on talc and cancer.

Over the past several decades, there have been many epidemiology studies on talc and cancer published in the scientific literature, and several reviews and meta-analyses of talc and respiratory, female reproductive, and stomach cancers, specifically. To help provide a resource for the evaluation of talc as a potential human carcinogen, we applied a consistent set of examination methods and criteria for all epidemiology studies that examined the association between talc exposure (by various routes) and cancers (of various types). We identified 30 cohort, 35 case-control, and 12 pooled studies that evaluated occupational, medicinal, and personal-care product talc exposure and cancers of the respiratory system, the female reproductive tract, the gastrointestinal tract, the urinary system, the lymphohematopoietic system, the prostate, male genital organs, and the central nervous system, as well as skin, eye, bone, connective tissue, peritoneal, and breast cancers. We tabulated study characteristics, quality, and results in a systematic manner, and evaluated all cancer types for which studies of at least three unique populations were available in a narrative review. We focused on study quality aspects most likely to impact the interpretation of results. We found that only one study, of medicinal talc use, evaluated direct exposure measurements for any individuals, though some used semi-quantitative exposure metrics, and few studies adequately assessed potential confounders. The only consistent associations were with ovarian cancer in case-control studies and these associations were likely impacted by recall and potentially other biases. This systematic review indicates that epidemiology studies do not support a causal association between occupational, medicinal, or personal talc exposure and any cancer in humans.

Tackling the toxics in plastics packaging.

The widespread use of plastic packaging for storing, transporting, and conveniently preparing or serving foodstuffs is significantly contributing to the global plastic pollution crisis. This has led to many efforts directed toward amending plastic packaging's end of life, such as recycling, or alternative material approaches, like increasingly using paper for food packaging. But these approaches often neglect the critical issue of chemical migration: When contacting foodstuffs, chemicals that are present in packaging transfer into food and thus unwittingly become part of the human diet. Hazardous chemicals, such as endocrine disrupters, carcinogens, or substances that bioaccumulate, are collectively referred to as "chemicals of concern." They can transfer from plastic packaging into food, together with other unknown or toxicologically uncharacterized chemicals. This chemical transfer is scientifically undisputed and makes plastic packaging a known, and avoidable, source of human exposure to synthetic, hazardous, and untested chemicals. Here, I discuss this issue and highlight aspects in need of improvement, namely the way that chemicals present in food packaging are assessed for toxicity. Further, I provide an outlook on how chemical contamination from food packaging could be addressed in the future. Robust innovations must attempt systemic change and tackle the issue of plastic pollution and chemical migration in a way that integrates all existing knowledge.

The Known and Unknown: Investigating the Carcinogenic Potential of Plastic Additives.

Microplastics are routinely ingested and inhaled by humans and other organisms. Despite the frequency of plastic exposure, little is known about its health consequences. Of particular concern are plastic additives─chemical compounds that are intentionally or unintentionally added to plastics to improve functionality or as residual components of plastic production. Additives are often loosely bound to the plastic polymer and may be released during plastic exposures. To better understand the health effects of plastic additives, we performed a comprehensive literature search to compile a list of 2,712 known plastic additives. Then, we performed an integrated toxicogenomic analysis of these additives, utilizing cancer classifications and carcinogenic expression pathways as a primary focus. Screening these substances across two chemical databases revealed two key observations: (1) over 150 plastic additives have known carcinogenicity and (2) the majority (∼90%) of plastic additives lack data on carcinogenic end points. Analyses of additive usage patterns pinpointed specific polymers, functions, and products in which carcinogenic additives reside. Based on published chemical-gene interactions, both carcinogenic additives and additives with unknown carcinogenicity impacted similar biological pathways. The predominant pathways involved DNA damage, apoptosis, the immune response, viral diseases, and cancer. This study underscores the urgent need for a systematic and comprehensive carcinogenicity assessment of plastic additives and regulatory responses to mitigate the potential health risks of plastic exposure.

Usnic acid attenuates 7,12-dimethylbenz[a] anthracene (DMBA) induced oral carcinogenesis through inhibiting oxidative stress, inflammation, and cell proliferation in male golden Syrian hamster model.

In this study, we investigated the chemopreventive efficacy of usnic acid (UA), an effective secondary metabolite component of lichens, against 7,12-dimethylbenz[a]anthracene (DMBA)-induced oral squamous cell carcinoma (OSCC) in the hamster model. Initially, the buccal pouch carcinogenesis was induced by administering 0.5% DMBA to the HBP (hamster buccal pouch) region about three times a week until the 10th week. Then, UA was orally treated with different concentrations (25, 50, 100 mg/kg b.wt) on alternative days of DMBA exposure, and the experimental process ended in the 16th week. After animal experimentation, we observed 100% tumor incidence with well-differentiated OSCC, dysplasia, and hyperplasia lesions in the DMBA-induced HBP region. Furthermore, the UA treatment of DMBA-induced hamster effectively inhibited tumor growth. In addition, UA upregulated antioxidant levels, interfered with the elevated lipid peroxidation by-product of thiobarbituric acid reactive substances, and changed the activities of the liver detoxification enzyme (Phase I and II) in DMBA-induced hamsters. Furthermore, immunohistochemical staining of inflammatory markers (iNOS and COX-2) and proliferative cell markers (cyclin-D1 and PCNA) were upregulated in the buccal pouch part of hamster animals induced with DMBA. Notably, the oral administration of UA significantly suppressed these markers during DMBA-induced hamsters. Collectively, our findings revealed that UA exhibits antioxidant, anti-inflammatory, antitumor, and apoptosis-inducing characteristics, demonstrating UA's protective properties against DMBA-induced HBP carcinogenesis.

Physiologically-based pharmacokinetic model for evaluating gender-specific exposures of N-nitrosodimethylamine (NDMA).

N-nitrosodimethylamine (NDMA) is classified as a human carcinogen and could be produced by both natural and industrial processes. Although its toxicity and histopathology have been well-studied in animal species, there is insufficient data on the blood and tissue exposures that can be correlated with the toxicity of NDMA. The purpose of this study was to evaluate gender-specific pharmacokinetics/toxicokinetics (PKs/TKs), tissue distribution, and excretion after the oral administration of three different doses of NDMA in rats using a physiologically-based pharmacokinetic (PBPK) model. The major target tissues for developing the PBPK model and evaluating dose metrics of NDMA included blood, gastrointestinal (GI) tract, liver, kidney, lung, heart, and brain. The predictive performance of the model was validated using sensitivity analysis, (average) fold error, and visual inspection of observations versus predictions. Then, a Monte Carlo simulation was performed to describe the magnitudes of inter-individual variability and uncertainty of the single model predictions. The developed PBPK model was applied for the exposure simulation of daily oral NDMA to estimate blood concentration ranges affecting health effects following acute-duration (≤ 14 days), intermediate-duration (15-364 days), and chronic-duration (≥ 365 days) intakes. The results of the study could be used as a scientific basis for interpreting the correlation between in vivo exposures and toxicological effects of NDMA.