Susceptibility To Carcinogens Research Articles

Space Microgravity Alters Neural Stem Cell Division: Implications for Brain Cancer Research on Earth and in Space.

Considering the imminence of long-term space travel, it is necessary to investigate the impact of space microgravity (SPC-µG) in order to determine if this environment has consequences on the astronauts' health, in particular, neural and cognitive functions. Neural stem cells (NSCs) are the basis for the regeneration of the central nervous system (CNS) cell populations and learning how weightlessness impacts NSCs in health and disease provides a critical tool for the potential mitigation of specific mechanisms leading to neurological disorders. In previous studies, we found that exposure to SPC-µG resulted in enhanced proliferation, a shortened cell cycle, and a larger cell diameter of NSCs compared to control cells. Here, we report the frequent occurrence of abnormal cell division (ACD) including incomplete cell division (ICD), where cytokinesis is not successfully completed, and multi-daughter cell division (MDCD) of NSCs following SPC-µG as well as secretome exposure compared to ground control (1G) NSCs. These findings provide new insights into the potential health implications of space travel and have far-reaching implications for understanding the mechanisms leading to the deleterious effects of long-term space travel as well as potential carcinogenic susceptibility. Knowledge of these mechanisms could help to develop preventive or corrective measures for successful long-term SPC-µG exposure.

Retinoblastoma protein regulates carcinogen susceptibility at heterochromatic cancer driver loci.

Carcinogenic insult, such as UV light exposure, creates DNA lesions that evolve into mutations if left unrepaired. These resulting mutations can contribute to carcinogenesis and drive malignant phenotypes. Susceptibility to carcinogens (i.e., the propensity to form a carcinogen-induced DNA lesion) is regulated by both genetic and epigenetic factors. Importantly, carcinogen susceptibility is a critical contributor to cancer mutagenesis. It is known that mutations can be prevented by tumor suppressor regulation of DNA damage response pathways; however, their roles carcinogen susceptibility have not yet been reported. In this study, we reveal that the retinoblastoma (RB1) tumor suppressor regulates UV susceptibility across broad regions of the genome. In particular, centromere and telomere-proximal regions exhibit significant increases in UV lesion susceptibility when RB1 is deleted. Several cancer-related genes are located within genomic regions of increased susceptibility, including telomerase reverse transcriptase, TERT, thereby accelerating mutagenic potential in cancers with RB1 pathway alterations. These findings reveal novel genome stability mechanisms of a tumor suppressor and uncover new pathways to accumulate mutations during cancer evolution.

Cell fate analysis of zone 3 hepatocytes in liver injury and tumorigenesis

Background & AimsLiver lobules are typically subdivided into 3 metabolic zones: zones 1, 2, and 3. However, the contribution of zonal differences in hepatocytes to liver regeneration, as well as to carcinogenic susceptibility, remains unclear.MethodsWe developed a new method for sustained genetic labelling of zone 3 hepatocytes and performed fate tracing to monitor these cells in multiple mouse liver tumour models.ResultsWe first examined changes in the zonal distribution of the Wnt target gene Axin2 over time using Axin2-CreERT2;Rosa26-Lox-Stop-Lox-tdTomato mice (Axin2;tdTomato). We found that following tamoxifen administration at 3 weeks of age, approximately one-third of total hepatocytes that correspond to zone 3 were labelled in Axin2;tdTomato mice; the tdTomato+ cell distribution closely matched that of the zone 3 marker CYP2E1. Cell fate analysis revealed that zone 3 hepatocytes maintained their own lineage but rarely proliferated beyond their liver zonation during homoeostasis; this indicated that our protocol enabled persistent genetic labelling of zone 3 hepatocytes. Using this system, we found that zone 3 hepatocytes generally had high neoplastic potential, which was promoted by constitutive activation of Wnt/β-catenin signalling in the pericentral area. However, the frequency of zone 3 hepatocyte-derived tumours varied depending on the regeneration pattern of the liver parenchyma in response to liver injury. Notably, Axin2-expressing hepatocytes undergoing chronic liver injury significantly contributed to liver regeneration and possessed high neoplastic potential. Additionally, we revealed that the metabolic phenotypes of liver tumours were acquired during tumorigenesis, irrespective of their spatial origin.ConclusionsHepatocytes receiving Wnt/β-catenin signalling from their microenvironment have high neoplastic potential, and Wnt/β-catenin signalling is a potential drug target for the prevention of hepatocellular carcinoma.Lay summaryLineage tracing revealed that zone 3 hepatocytes residing in the pericentral niche have high neoplastic potential. Under chronic liver injury, hepatocytes receiving Wnt/β-catenin signalling broadly exist across all hepatic zones and significantly contribute to liver tumorigenesis as well as liver regeneration. Wnt/β-catenin signalling is a potential drug target for the prevention of hepatocellular carcinoma.

Carcinogen susceptibility is regulated by genome architecture and predicts cancer mutagenesis.

The development of many sporadic cancers is directly initiated by carcinogen exposure. Carcinogens induce malignancies by creating DNA lesions (i.e., adducts) that can result in mutations if left unrepaired. Despite this knowledge, there has been remarkably little investigation into the regulation of susceptibility to acquire DNA lesions. In this study, we present the first quantitative human genome-wide map of DNA lesions induced by ultraviolet (UV) radiation, the ubiquitous carcinogen in sunlight that causes skin cancer. Remarkably, the pattern of carcinogen susceptibility across the genome of primary cells significantly reflects mutation frequency in malignant melanoma. Surprisingly, DNase-accessible euchromatin is protected from UV, while lamina-associated heterochromatin at the nuclear periphery is vulnerable. Many cancer driver genes have an intrinsic increase in carcinogen susceptibility, including the BRAF oncogene that has the highest mutation frequency in melanoma. These findings provide a genome-wide snapshot of DNA injuries at the earliest stage of carcinogenesis. Furthermore, they identify carcinogen susceptibility as an origin of genome instability that is regulated by nuclear architecture and mirrors mutagenesis in cancer.

CRISPR-Cas9 Technology as a Fledgling Avenue in the Therapeutics of Hepatocellular Carcinoma

Background and Aim: Since its inception in 2012, the prokaryotic immune-like clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein (Cas)9 (CRISPR-Cas9) system has revolutionised the realm of genome editing with visionary implementations in synthetic biology, functional genomic screening, transcriptional modulation and gene therapy. Hepatocellular carcinoma (HCC) with a globally heterogeneous genetic and epigenetic landscape, is a fatal human malignancy, and therefore forms the perfect platform for therapeutic interventions with CRISPR-Cas9. Here we embellish the state-of-the-art on the novel genome engineering utilizations of CRISPR-Cas9 in HCC with plausible future perspectives. Methods: PubMed, Medline, Embase and Cochrane databases were scrutinised for relevant publications in English with keywords “CRISPR-Cas9 and cancer”, “CRISPR-Cas9 and hepatocellular carcinoma,” “applications of CRISPR-Cas9 and hepatocellular carcinoma,” and “genome editing with CRISPR-Cas9 and hepatocellular carcinoma,” unsheathed till April 2017. Manuscripts relating to applications of CRISPR-Cas9 other than in cancers were excluded. Results: Recently, HBV-specific CRISPR-Cas9 systems have effectively mediated pro-oncogenic HBV cccDNA disruption thereby scripting a therapeutic promise in HBV-induced HCC. Evidence illustrate that inhibition of FGF19/FGFR4 by CRISPR-Cas9 signalling significantly overcomes sorafenib resistance in HCC. Data display a CRISPR-Cas9 regulated knockout of a component of SWItch/Sucrose Non-Fermentable (SWI/SNF) complex called ARID2 from human HCC cell lines, to correlate tightly with the disruption of DNA repair, resulting in carcinogen susceptibility and potential hypermutation. Mouse models of CRISPR/Cas9-induced HCC elucidate multiplexed CRISPR/Cas9 mediated functional genomic analyses of hepatobiliary cancers. Additionally, a genome-wide CRISPR screen has identified regulators of mitogen-activated protein kinase as suppressors of mice liver tumours. Conclusion: Despite pitfalls such as Cas9 activity, target site selection and short guide RNA design, delivery methods, off-target effects and the incidence of homology-directed repair affecting the efficiency and specificity of CRISPR-Cas9, this novel technology has ushered in a new era of cellular manipulation with newer vistas in the therapeutic management of HCC. The authors have none to declare.

Effect of amplification of xenobiotic detoxification pathways genes on survival in lung adenocarcinoma versus squamous cell carcinoma bases on the Cancer Genome Atlas provisional database.

e14093 Background: Ral interacting protein (RLIP76) is a stress-responsive anti-apoptotic efflux transporter of the mercapturic acid pathway (MPy). The MPy enzymes are an essential component of the broader xenobiotic detoxification pathways (XDP) that are regulated by p53 (TP53) in response to xenobiotic/oxidative stress. Homozygous Rlip knockout (Rlip-/-) mice are resistant to benzopyrene induced adenocarcinoma and have constitutive activation of p53. The cancer-resistant phenotype of Rlip-/- mice is the diametric opposite of p53 homozygous knockout mice (p53-/-) mice, which die before the age of 24 weeks of spontaneous malignancy. Methods: Our preliminary studies show that creating Rlip deficiency through pharmacological or genetic methods caused all p53-/- mice to remain cancer-free at an unprecedented age of 32 weeks. This degree of cancer prevention has never been observed with any previous pharmacological or genetic intervention in p53-/- mice. Transcriptomic and epigenomic profiling of the cancer-free p53-/- mice revealed that the direction of change in expression of a network of Rlip-linked XDP enzymes and signaling proteins was identical to that in the cancer-resistant Rlip-/- mice. Results: We hypothesized that the activity of this Rlip-linked subset of the XDP enzymes/signaling proteins (designated XMN1) is a determinant of carcinogenic susceptibility caused by p53 loss. To examine this possibility, we queried the TCGA (The Cancer Genome Atlas) database to determine whether components of XMN1 were differentially expressed in human malignancy, and whether this was associated with overall survival. We focused on non-small cell lung cancer because of the high incidence of p53 mutations in these cancers. To our surprise, we found amplification or upregulation of XMN1 components conferred a reduced survival in lung adenocarcinoma but prolonged survival in squamous cell carcinoma. Conclusions: The mechanisms underlying this remarkable diametrically opposite effect on prognosis of are unknown and suggest opposed functions of XMN1 in Squamous verses Adenocarcinoma.

Metachronous Basal Cell Carcinoma and Primary Plasmacytic Leukemia Associated With Dermatomyositis

Dermatomyositis is associated with cancer frequently. However, successive occurrence of two malignancies in one person is rare. In this article, we present a 71-year-old female patient who was diagnosed as dermatomyositis based on skin lesions, muscle weakness, elevated muscle enzymes, electromyography, and muscle biopsy. Two years later, the patient had an ulcer on the left nasolabial groove. A resection was performed after basal cell carcinoma was confirmed by tissue biopsy. Two years after resection, serum M protein, urinary l light chain, and neoplastic plasma cells infiltration in bone marrow biopsy of the patient were evaluated. Findings were compatible with the plasmacytic leukemia. Dermatomyositis patients may suffer from multiple tumors due to carcinogenic susceptibility. Therefore, physicians should continue to monitor dermatomyositis patients after the occurrence of the first tumor since they still have the possibility of developing another malignancy.

Age-Dependent Carcinogenic Susceptibility in Rat Liver Is Related to Potential of Gap Junctional Intercellular Communication

Connexin 32 (Cx32) is a major gap junction protein in the liver. The authors previously demonstrated that transgenic rats carrying a dominant negative mutant of Cx32 (Cx32ΔTg) have much decreased capacity for gap junctional intercellular communication (GJIC) and increased susceptibility to diethylnitrosamine (DEN)-induced hepatocarcinogenesis as compared to littermate wild-type (wt) rats. To evaluate the age-dependent susceptibility to DEN-induced hepatocarcinogenesis and alteration of GJIC function, male Cx32ΔTg and wt rats at 10, 30, or 85 weeks old were given a single intraperitoneal administration of DEN (40 mg/rat) and sacrificed 12 weeks later. The number and area of glutathione S-transferase placental form (GST-P)-positive preneoplastic foci were significantly increased in the liver of 10- and 30-wk-old Cx32ΔTg rats compared with age-matched wt. However, in the 85-wk-old rats, both Cx32ΔTg and wt rats had similarly large number and area of GST-P-positive foci, and the difference was not significant. Interestingly, function of hepatic GJIC was reduced and protein and mRNA expression of Cx32 were decreased with aging in wt rats. These results suggest that a decline of hepatic intercellular communication through gap junction results in increased susceptibility to DEN-induced hepatocarcinogenesis in aged rats.

Abstract 4419: The role of ABC transporters in PhIP-induced colon carcinogenesis

Abstract ABC transporters such as BCRP, P-gp, Mrp2 and Mrp3 are thought to protect organisms from xenobiotics, including dietary carcinogens and anticancer drugs. These multidrug transporters reduce the oral uptake, systemic availability and tissue or cellular accumulation of transported substrates by mediating their extrusion from cells and the body in general. Therefore, they could have very important roles in the distribution of carcinogens to certain tissues and cell types, and carcinogen susceptibility. In this study, we aimed to investigate the role of ABC transporters in the tumorigenicity of a dietary carcinogen, PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine), which is produced during high-temperature cooking of meat. We have performed a pharmacokinetic experiment in wild-type FVB and ABC transporter knockout strains (Bcrp;Mrp2;Mrp3-/- and Bcrp;Mdr1a/1b;Mrp2-/-) with 200 mg/kg orally administered PhIP and observed that ABC transporters have an impact on the distribution of PhIP metabolites to several organs. There was an accumulation of N-OH-PhIP, a potentially carcinogenic metabolite, in the liver of Bcrp;Mrp2;Mrp3-/- mice and a decrease in the levels of PhIP-5-sulfate, a surrogate marker for DNA exposure to reactive compound, in small intestine of Bcrp;Mrp2;Mrp3-/- and Bcrp;Mdr1a/1b;Mrp2-/- mice compared to wild-type FVB. For carcinogenesis experiments, we used a chemically-induced colon carcinogenesis model where wild-type FVB and ABC transporter compound knock-out mice received a single, oral administration of 200 mg/kg PhIP for initiation and seven days administration of Dextran Sodium Sulfate (DSS) in drinking water for promotion of the tumorigenesis process via colonic inflammation. During the whole experiment, mice were closely checked for their body weight loss, diarrhea and rectal bleeding. Our results showed that PhIP and DSS treatment together induced colonic tumors in all strains over 180 days. No tumor formation could be found in only PhIP-treated, only DSS-treated and negative control groups that received vehicle. Tumor incidence was lower in both knock-outs compared to the wild-type FVB when inflammation levels between the groups were corrected. Our results suggest that these ABC transporters are not protecting the intestinal tract from PhIP-induced carcinogenesis upon oral ingestion in mice, and perhaps even partially enhance PhIP-induced carcinogenesis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4419. doi:1538-7445.AM2012-4419

Abstract 4980: Age dependent carcinogenic susceptibility of rat liver is related to potential of gap junctional intercellular communication

Abstract Cancer incidence rises with age, thus, it seems that advancing age is one of the most important risk factors for malignancy. Several factors have been implicated, like DNA alterations. However, there is little experimental evidence to establish the link between aging and carcinogenesis. Gap junctions have important roles in the maintenance of tissue homeostasis and the control of cell growth and differentiation. Connexins are subunits of gap junction channels, which allow intercellular exchange of small molecules, such as ions, second messengers, and cellular metabolites between contacting cells. In the liver, connexin 32 (Cx32) is a major gap junction protein. We previously demonstrated that transgenic rats carrying a dominant negative mutant of Cx32 (Cx32ΔTg) have much decreased capacity for gap junctional intercellular communication (GJIC), and increased susceptibility to diethylnitrosamine (DEN)-induced hepatocarcinogenesis as compared to littermate wild-type (wt) rats. In order to evaluate the age-dependent susceptibility to DEN-induced hepatocarcinogenesis, male Cx32ΔTg and wt rats at 10, 30 or 85 week-old (wk-old) were given a single intraperitoneal administration of DEN (40 mg/rat) and sacrificed 12 weeks later. The number and area of glutathione S-transferase placental form (GST-P)-positive preneoplastic foci were significantly increased in the liver of 10 and 30 wk-old Cx32ΔTg rats compared with age-matched wt. However, in the 85 wk-old rats, both Cx32ΔTg and wt rats had similarly large number and area of GST-P-positive foci, and the difference was not significant. In accordance with these results, the lack of a difference at 85 weeks may be supposed to the initial lower levels of Cx32 and GJIC function in older wt rats. To confirm this hypothesis, we examined alteration of GJIC function with age in the livers of wt type rats at 10, 40, 70 and 100 wk-old. Interestingly, function of hepatic GJIC was gradually reduced, and protein and mRNA expression of Cx32 were also decreased with aging in wt rats. In summary, the present study shows that GJIC function is decreased with aging in rats, and it may cause promotion of hepatocarcinogenesis in older rats. In addition, Cx32ΔTg may be a good model to study roles of gap junctions in aged liver. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4980. doi:1538-7445.AM2012-4980

Establishing a Laboratory Animal Model From a Transgenic Animal

Transgenic animal models have been used in small numbers in gene function studies in vivo for a period of time, but more recently, the use of a single transgenic animal model has been approved as a second species, 6-month alternative (to the routine 2-year, 2-animal model) used in short-term carcinogenicity studies for generating regulatory application data of new drugs. This article addresses many of the issues associated with the creation and use of one of these transgenic models, the rasH2 mouse, for regulatory science. The discussion includes strategies for mass producing mice with the same stable phenotype, including constructing the transgene, choosing a founder mouse, and controlling both the transgene and background genes; strategies for developing the model for regulatory science, including measurements of carcinogen susceptibility, stability of a large-scale production system, and monitoring for uniform carcinogenicity responses; and finally, efficient use of the transgenic animal model on study. Approximately 20% of mouse carcinogenicity studies for new drug applications in the United States currently use transgenic models, typically the rasH2 mouse. The rasH2 mouse could contribute to animal welfare by reducing the numbers of animals used as well as reducing the cost of carcinogenicity studies. A better understanding of the advantages and disadvantages of the transgenic rasH2 mouse will result in greater and more efficient use of this animal model in the future.

Long-lived Inflammatory Signaling in Irradiated Bone Marrow Is Genome Dependent

Ionizing radiation is carcinogenic, but genotype is a key determinant of susceptibility. Mutational DNA damage is generally attributed to cause disease, but irradiation also affects multicellular interactions as a result of poorly understood bystander effects that may influence carcinogenic susceptibility. In this study, we show that the bone marrow of irradiated mice will retain the ability to kill hemopoietic clonogenic stem cells and to induce chromosomal instability for up to 3 months after irradiation. Chromosomal instability was induced in bone marrow cells derived from CBA/Ca mice, a strain that is susceptible to radiation-induced acute myeloid leukemia (r-AML), but not in C57BL6 mice that are resistant to r-AML. Similarly, clonogenic cell lethality was exhibited in C57BL/6 mice but not CBA/Ca mice. Mechanistic investigations revealed that these genotype-dependent effects involved cytokine-mediated signaling and were mediated by a cyclooxygenase-2-dependent mechanism. Thus, our results suggested that inflammatory processes were responsible for mediating and sustaining the durable effects of ionizing radiation observed on bone marrow cells. Because most exposures to ionizing radiation are directed to only part of the body, our findings imply that genotype-directed tissue responses may be important determinants of understanding the specific consequence of radiation exposure in different individuals.

Continuous carcinogenic susceptibility monitoring of CB6F1 TG RASH2 mice

Continuous carcinogenic susceptibility monitoring of CB6F1 TG RASH2 mice

Prenatal exposure to bisphenol A promotes angiogenesis and alters steroid-mediated responses in the mammary glands of cycling rats

Prenatal exposure to BPA disturbs mammary gland histoarchitecture and increases the carcinogenic susceptibility to chemical challenges administered long after BPA exposure. Our aim was to assess the effect of prenatal BPA exposure on mammary gland angiogenesis and steroid hormone pathways in virgin cycling rats. Pregnant Wistar rats were exposed to either 25 or 250μg/kg/day (25 and 250 BPA, respectively) or to vehicle. Female offspring were autopsied on postnatal day (PND) 50 or 110. Ovarian steroid serum levels, the expression of steroid receptors and their co-regulators SRC-3 and SMRT in the mammary gland, and angiogenesis were evaluated. At PND 50, all BPA-treated animals had lower serum levels of progesterone, while estradiol levels remained unchanged. The higher dose of BPA increased mammary ERα and decreased SRC-3 expression at PND 50 and PND 110. SMRT protein levels were similar among groups at PND 50, whereas at PND 110, animals exposed to 250 BPA showed a lower SMRT expression. Interestingly, in the control and 25 BPA groups, SMRT increased from PND 50 to PND 110. At PND 50, an increased vascular area associated with higher VEGF expression was observed in the 250 BPA-treated rats. At PND 110, the vascular area was still increased, but VEGF expression was similar to that of control rats. The present results demonstrate that prenatal exposure to BPA alters the endocrine environment of the mammary gland and its angiogenic process. Increased angiogenesis and altered steroid hormone signals could explain the higher frequency of pre-neoplastic lesions found later in life.This article is part of a Special Issue entitled ‘Endocrine disruptors’.

Prenatal Preview: Early Bisphenol A Exposure May Spawn Late-Life Reproductive Problems

Vol. 117, No. 6 EnvironewsOpen AccessPrenatal Preview: Early Bisphenol A Exposure May Spawn Late-Life Reproductive Problemsis corrected byErrata Angela Spivey Angela Spivey Search for more papers by this author Published:1 June 2009https://doi.org/10.1289/ehp.117-a256aCited by:3AboutSectionsPDF ToolsDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InReddit Scientists increasingly find that exposure to toxicants during critical periods of pre- and perinatal development can have long-lasting effects that increase the risk of reduced fertility, reproductive tumors, and breast cancer later in life. Some animal studies have suggested that very low doses of bisphenol A (BPA) in a range relevant to human exposures can cause abnormalities in the uterus, vagina, and ovary when those exposures occur during early development. To date, however, evidence for a carcinogenic effect of low-dose BPA on the female reproductive tract has been lacking; studies examining carcinogenic susceptibility to BPA have focused only on the mammary and prostate glands. Now a report from researchers at the NIEHS indicates that low prenatal doses of BPA in mice may cause potentially carcinogenic alterations in female reproductive tissues [EHP117:879–885; Newbold et al.].Widespread human exposure to BPA is a cause for concern because of the compound’s chemical similarity to diethylstilbestrol (DES), an antinausea drug that caused harmful reproductive effects in women whose mothers took it during pregnancy. This study used an experimental animal model (the CD-1 mouse) that has been useful in studying the effects of prenatal exposure to DES.On gestational days 9–16, pregnant mice were injected with relatively low dosages of BPA—0.1, 1, 10, 100, or 1,000 μg/kg/day, which are considered by the authors and other researchers to be within an environmentally relevant range. When the dams’ offspring reached late adulthood (16–18 months), their reproductive tissues were evaluated.Some of the BPA-exposed offspring developed both benign and malignant lesions in late adulthood. In the pups that received 1 μg/kg/day, the incidence of benign ovarian cysts was 67%—similar to what the same team had previously observed for neonatal exposure to BPA. In addition, more severe ovarian lesions were found in the groups that received 10, 100, or 1,000 μg/kg/day but not in control animals. The occurrence of progressive proliferative lesions of the oviduct seemed to increase following BPA exposure, similar to effects seen in previous studies following prenatal exposure to DES. Because DES appears to delay the expression of genes that guide the development of the reproductive tract, the authors suggest that molecular “misprogramming” is the most likely reason for both DES- and BPA-induced lesions of the oviduct.Malignant changes in the uterus also were found in exposed mice, although the incidence of those lesions was not statistically different from that seen in controls. In addition, more severe pathologies were observed in exposed animals but not in controls. These included atypical hyperplasia and stromal polyps of the uterus, sarcoma of the uterine cervix, and mammary adenocarcinoma.According to the authors, this study is the first to find both benign and malignant lesions in reproductive tissues of senescent female mice exposed prenatally to BPA over a wide dosage range thought to be relevant to human exposure. The study adds to the growing body of literature showing adverse effects following developmental exposure to low doses of BPA and suggests that exposure during critical periods of fetal development may result in adverse reproductive and carcinogenic changes over the long term.FiguresReferencesRelatedDetailsCited by Beydoun H, Beydoun M, Jeng H, Zonderman A and Eid S (2016) Bisphenol-A and Sleep Adequacy among Adults in the National Health and Nutrition Examination Surveys, Sleep, 10.5665/sleep.5466, 39:2, (467-476), Online publication date: 1-Feb-2016., Online publication date: 1-Feb-2016. Beydoun H, Khanal S, Zonderman A and Beydoun M (2014) Sex differences in the association of urinary bisphenol-A concentration with selected indices of glucose homeostasis among U.S. adults, Annals of Epidemiology, 10.1016/j.annepidem.2013.07.014, 24:2, (90-97), Online publication date: 1-Feb-2014. Dietert R, DeWitt J, Germolec D and Zelikoff J (2010) Breaking Patterns of Environmentally Influenced Disease for Health Risk Reduction: Immune Perspectives, Environmental Health Perspectives, 118:8, (1091-1099), Online publication date: 1-Aug-2010.Related articlesErrata1 August 2009Environmental Health Perspectives Vol. 117, No. 6 June 2009Metrics About Article Metrics Publication History Originally published1 June 2009Published in print1 June 2009 Financial disclosuresPDF download License information EHP is an open-access journal published with support from the National Institute of Environmental Health Sciences, National Institutes of Health. All content is public domain unless otherwise noted. Note to readers with disabilities EHP strives to ensure that all journal content is accessible to all readers. However, some figures and Supplemental Material published in EHP articles may not conform to 508 standards due to the complexity of the information being presented. If you need assistance accessing journal content, please contact [email protected]. Our staff will work with you to assess and meet your accessibility needs within 3 working days.

S15: Possible risk assessment using human ras gene transgenic rat

A variety of transgenic mice, such as v-Ha-ras transgenic mice, pim-1 transgenic mice, mice carrying the human c-Ha-ras proto-oncogene, and mice deficient for tumor-suppressor gene p53, have been shown to exhibit increased carcinogen susceptibility. Therefore, studies designed to test the practical application of these animal models for use in medium-term screening of environmental carcinogens have been conducted. As test animals, however, rats have several advantages over mice: larger organ size, abundant information regarding characteristics of preneoplasias, and virus-free constitution. We have generated transgenic rats bearing the human c-Ha-ras proto-oncogene (strain Hras128) and shown that the females are highly susceptible to chemically-induced mammary carcinogenesis, and males, to a lesser extent, urinary bladder, oesophagus and skin carcinogenesis. The tumors which develop in these animals’ exhibit mutations in the ras gene, and in most of these tumors the ras gene mutations were found exclusively in the transgene and not in the endogenous gene. These mutations appeared to occur early in the process of carcinogenesis, which involves proliferation of cells in terminal end buds (TEBs) and intraductal hyperplasia before carcinomas develop. Based on our findings of high susceptibility to N-methyl-N-nitrosourea (MNU), dimethylbenzo[a]anthracene (DMBA), and 2-amino-1-methl-6-phenylimidazo[4,5-b]pyridine (PhIP) in inducing mammary carcinomas in a short time (6–12 weeks), we examined various known carcinogens which do not normally induce mammary carcinomas using famale Hras128 rats. Significant increases in mammary carcinomas was observed in groups administered 3-MC, B[a]P, anthracene, IQ, MeIQx, and azoxymethane (AOM). With 3-MC, B[a]P, IQ, and AOM, mutations of the transgene in codons 12 and 61 were observed in the induced carcinomas. Thus various carcinogens, not necessarily limited to those normally targeting the mammary gland, were found to induce mammary carcinomas, pointing to the potential use of c-Ha-ras transgenic rats for use in medium-term screening.

Inheritance of susceptibility to induction of nephroblastomas in the Noble rat

Noble (Nb) strain rats are susceptible to nephroblastoma induction with transplacental exposure to direct-acting alkylating agent N-nitrosoethylurea (ENU), while F344 strain rats are highly resistant. To study the inheritance of susceptibility to induction of these embryonal renal tumors, fetal Nb and F344 rats and F1, F2 and reciprocal backcross hybrids were exposed transplacentally to ENU once on day 18 of gestation. Nephroblastomas developed in 53% of Nb offspring with no apparent gender difference, while no nephroblastomas developed in inbred F344 offspring. F1 and F2 hybrid offspring had intermediate responses, 28% and 30%, respectively. Nephroblastoma incidence in the offspring of F1 hybrids backcrossed to the susceptible strain Nb was 46%, while that in F1 hybrids backcrossed to resistant strain F344 was much lower (16%). Carcinogenic susceptibility is therefore consistent with the involvement of one major autosomal locus; the operation of a gene dosage effect; and a lack of simple Mendelian dominance for either susceptibility or resistance. Since established Wilms tumor-associated suppressor genes, Wt1 and Wtx, were not mutated in normal or neoplastic tissues, genomic profiling was performed on isolated Nb and F344 metanephric progenitors to identify possible predisposing factors to nephroblastoma induction. Genes preferentially elevated in expression in Nb rat progenitors included Wnt target genes Epidermal growth factor receptor, Inhibitor of DNA binding 2, and Jagged1, which were further increased in nephroblastomas. These studies demonstrate the value of this model for genetic analysis of nephroblastoma development and implicate both the Wnt and Notch pathways in its pathogenesis.

Hepatocarcinogenic Susceptibility of Fenofibrate and Its Possible Mechanism of Carcinogenicity in a Two-Stage Hepatocarcinogenesis Model of rasH2 Mice

Fenofibrate (FF) has previously been shown to induce hepatocellular neoplasia in a conventional mouse bioassay (NDA 1993), but there has been no report to examine the carcinogenic susceptibility of rasH2 mice to this chemical. In the present study, male rasH2 mice were subjected to a two-thirds partial hepatectomy (PH), followed by an N-diethylnitrosamine (DEN) initiation twenty-four hours after PH, and given a diet containing 0, 1200, or 2400 ppm FF for seven weeks. The incidences of preneoplastic foci were significantly increased in mice from the FF-treated groups. Immunohistochemistry revealed that significant increases in proliferating cell nuclear antigen (PCNA)-positive cells and cytokeratin 8/18 positive foci were observed in FF-treated groups. In addition, the transgene and several downstream molecules such as c-myc, c-jun, activating transcription factor 3 (ATF3), and cyclin D1 were overexpressed in these groups. These results suggest that the hepatocarcinogenic activity of rasH2 mice to FF can be detected in this hepatocarcinogenesis model and that up-regulation of genes for the ras/MAPK pathway and cell cycle was probably involved in the hepatocarcinogenic mechanism of rasH2 mice.

Early development of histiocytic sarcomas in p53 knockout mice treated with N-bis(2-hydroxypropyl)nitrosamine

p53 knockout mice have been utilized for the functional analysis of p53 in carcinogenic processes and for the evaluation of the carcinogenic potential of chemicals. In this study, we established that p53 knockout mice have an elevated susceptibility to the induction of histiocytic sarcoma (HS) by N-bis(2-hydroxy-propyl)nitrosamine (BHP). p53 heterozygous (+/-) and wild-type (+/+) mice were treated with 20 or 200 ppm BHP in their drinking water for 15 weeks or with 20 ppm BHP for 40 weeks. An additional group of p53 nullizygous (-/-) mice were treated with 20 ppm BHP for 15 weeks. In a 15-week experiment, hepatic HSs were unexpectedly observed in BHP-treated p53 (-/-) mice (30.8%) but not in p53 (+/-) and (+/+) mice and untreated (-/-) mice, indicating that a complete loss of p53 dramatically accelerates the genesis of HS. In a 40-week experiment, HSs were significantly increased in female p53 (+/-) mice (37.5%) as compared with female (+/+) mice (5.0%). Additionally, PCR-SSCP and sequencing analysis revealed a high frequency of p53 gene mutations in HSs, demonstrating the involvement of p53 gene mutations in HS development. Our data add to the understanding of the carcinogenic susceptibility of p53 knockout mice, and may help to elucidate the pathogenesis of HS development.

Carcinogenic susceptibility of rasH2 mice to troglitazone

To evaluate the carcinogenicity of troglitazone in rasH2 mice, 7-week-old male and female rasH2 mice were fed a diet containing 0, 3,000 or 6,000 ppm troglitazone for 26 weeks. An increased tendency in the incidence of vascular tumors was observed in females of the 6,000 ppm group. The preliminary analysis using a high-density oligonucleotide microarray on a splenic hemangiosarcoma of a high dose female that could be obtained as a fresh sample showed that several genes related to the ras/MAPK pathway activation, angiogenesis, cell cycle and cell multiplication were up-regulated. In addition, most of the genes up-regulated were confirmed by the reverse transcriptase-polymerase chain reaction (RT-PCR). These results may suggest that the carcinogenic susceptibility of rasH2 mice to troglitazone is relatively low and up-regulations of the ras/MAPK pathway and angiogenesis-related genes are probably involved in the production of splenic hemangiosarcomas in rasH2 mice given troglitazone.