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Traditional bullying and cyberbullying at schools in Germany: Results of the HBSC study 2022 and trends from 2009/10 to 2022. JOURNAL OF HEALTH MONITORING 2024; 9:42-61. [PMID: 38559684 PMCID: PMC10977470 DOI: 10.25646/11872] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Accepted: 12/04/2023] [Indexed: 04/04/2024]
Abstract
Background Bullying is a form of violence that is carried out repeatedly, with the intention of causing harm and with an imbalance of power between those involved. Bullying has serious negative effects on the mental health of adolescents and thus represents a significant health risk in childhood and adolescence. Methods Based on data from the Health Behaviour in School-aged Children (HBSC) study from the survey year 2022 in Germany (N = 6,475), the prevalence of school bullying and cyberbullying among 11-, 13- and 15-year-olds in Germany was analysed. In addition, the prevalence of school bullying and cyberbullying was analysed as a trend from 2009/10 to 2022 (bullying) and from 2017/18 to 2022 (cyberbullying). Results Around 14 % of the learners surveyed reported direct experience of bullying at school, and around 7 % reported cyberbullying experiences as bullied and/or bullying victims. Adolescents who identified as gender diverse were particularly likely to report bullying experiences. School bullying decreased over time, but remained stable between 2017/18 and 2022. Cyberbullying, on the other hand, increased in 2022 compared to 2017/18. Conclusions Experiencing bullying at school and online is an everyday experience for many children and young people, so there is still a need for the broad implementation of effective anti-bullying measures in schools.
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Concept and methodology of the Health Behaviour in School-aged Children (HBSC) study - Insights into the current 2022 survey and trends in Germany. JOURNAL OF HEALTH MONITORING 2024; 9:99-117. [PMID: 38559683 PMCID: PMC10977469 DOI: 10.25646/11878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Accepted: 11/28/2023] [Indexed: 04/04/2024]
Abstract
Background Health Behaviour in School-aged Children (HBSC) is one of the largest international studies on child and adolescent health and cooperates with the World Health Organization (WHO). In Germany, adolescents aged 11, 13 and 15 are surveyed every four years about their health, health behaviour and social conditions. This article describes the HBSC study and in particular the methodology of the current 2022 survey and prior surveys conducted between 2009/10 and 2017/18. Method 174 schools with a total of 6,475 students participated in the 2022 survey. The survey was conducted using questionnaires and covered a wide range of topics (including mental health, physical activity, bullying experiences, social determinants of health and experiences related to COVID-19). The 2022 survey was complemented by a school principal survey (N = 160). In addition to the current sample, the samples of the three previous surveys with representative data for Germany are presented: 2009/10 (N = 5,005), 2013/14 (N = 5,961) and 2017/18 (N = 4,347). Discussion The health of children and adolescents is of great public health importance. The HBSC study makes a substantial contribution by providing internationally comparable results, analysing trends, and providing stakeholders with comprehensive and representative health monitoring data.
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Measuring Health Literacy in Childhood and Adolescence with the Scale Health Literacy in School-Aged Children – German Version. DIAGNOSTICA 2022. [DOI: 10.1026/0012-1924/a000296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Abstract. Health literacy can help explain health inequalities in childhood and adolescence. However, suitable instruments for assessing health literacy in this age group are rare, especially in the German-speaking countries. One economical measure is the 10-item Health Literacy in School-Aged Children (HLSAC) scale, developed and reviewed as part of the WHO Child and Adolescent Health Study (HBSC, Health Behavior in School-Aged Children). In the present study, we tested dimensionality, measurement invariance, and associations with health-related measures of the German version of the scale (HLSAC–German), using data from the 2018 national German HBSC study ( N = 4,347 students aged 11, 13, and 15 years). We also tested HLSAC–German with 11-year-olds, representing an expansion of the original scale. Exploratory and confirmatory factor analyses consistently demonstrated the unidimensionality of the scale (α = .88). Complete scalar measurement invariance was found for sex and partial scalar measurement invariance for age groups and school type, allowing for the comparison of means. Associations with indicators of health and health behavior further demonstrate the construct validity of the scale. The analyses show that the scale is suitable for the economic measurement of a general factor of health literacy in 11- as well as in 13- and 15-year-olds.
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A Consequential Partnership. ZEITSCHRIFT FUR PSYCHOLOGIE-JOURNAL OF PSYCHOLOGY 2022. [DOI: 10.1027/2151-2604/a000497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Abstract. Many studies have focused on the effects of teachers’ well-being on the development of students, in particular their academic achievement. To date, little is known about the association between teachers’ well-being and students’ well-being. In the present study, we analyzed this relationship and examined the mediating role of teacher support using linked data from 2,686 students and 805 teachers from 48 schools in Germany. Multilevel regression analyses showed a relationship between teachers’ emotional exhaustion and students’ subjective health complaints and between teachers’ psychological well-being and students’ satisfaction with school. The latter association was mediated by teacher support as perceived by students. This study extends current knowledge about the relevance of teachers’ well-being to their students’ socio-emotional development and the mechanisms that underlie this association. Implications for promoting of mental health in schools and for future research are discussed.
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[Digital health literacy of pupils. Level and associations with physical activity and dietary behavior]. Bundesgesundheitsblatt Gesundheitsforschung Gesundheitsschutz 2022; 65:784-794. [PMID: 35652921 PMCID: PMC9160509 DOI: 10.1007/s00103-022-03548-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Accepted: 05/03/2022] [Indexed: 11/30/2022]
Abstract
Hintergrund Während vermehrt Studienbefunde zur allgemeinen Gesundheitskompetenz (GK) vorliegen, mangelt es an Erkenntnissen zur digitalen GK im Jugendalter und deren Assoziationen mit Indikatoren des Gesundheitsverhaltens. Methodik Empirische Basis bildet eine von Oktober 2019 bis Februar 2020 im Bundesland Hessen durchgeführte Querschnittstudie mit 490 Schülerinnen und Schülern der Klassenstufe 8 und 9. Die digitale GK wurde mithilfe von 5 Subskalen des Digital Health Literacy Instrument (DHLI) erfasst, während der Verzehr von Obst, Gemüse und Softdrinks sowie die körperliche Aktivität als Indikatoren des Gesundheitsverhaltens herangezogen wurden. Als soziales Merkmal wurde neben dem Geschlecht und der Klassenstufe der subjektive Sozialstatus (SSS) berücksichtigt. Die Datenauswertung erfolgte uni-, bi- und multivariat, wobei binärlogistische Regressionen für das Geschlecht und den SSS adjustiert wurden. Ergebnisse Über alle Items hinweg berichten 15,3–37,5 % der befragten Jugendlichen Schwierigkeiten bei der Beschaffung von und im Umgang mit digitalen Informationen. Differenziert nach sozialen Merkmalen finden sich für 2 Dimensionen der digitalen GK Unterschiede zuungunsten der Mädchen sowie durchgehend ein sozialer Gradient zuungunsten von Befragten mit niedrigem SSS. Jugendliche mit mittlerer und geringer digitaler GK weisen ein höheres Maß an geringer körperlicher Aktivität, nichttäglichem Obstverzehr und täglichem Konsum von zuckerhaltigen Getränken auf. Diskussion Die Befunde weisen auf einen Interventionsbedarf zur Förderung der digitalen GK insbesondere bei Jugendlichen mit geringem SSS hin. Die differenziellen Zusammenhangsmuster mit dem Gesundheitsverhalten bieten Ansatzpunkte für die Entwicklung spezifischer Interventionen. Als Lehr- und Lernort stellt die Schule u. a. aufgrund der Passung mit verpflichtenden Strategien der schulischen Medienkompetenzbildung ein geeignetes Setting dar.
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Teachers’ empathy and likelihood of intervention in hypothetical relational and retrospectively reported bullying situations. EUROPEAN JOURNAL OF DEVELOPMENTAL PSYCHOLOGY 2020. [DOI: 10.1080/17405629.2020.1869538] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Traditional bullying and cyberbullying among children and adolescents in Germany - Cross-sectional results of the 2017/18 HBSC study and trends. JOURNAL OF HEALTH MONITORING 2020; 5:53-68. [PMID: 35146273 PMCID: PMC8734197 DOI: 10.25646/6902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Accepted: 05/25/2020] [Indexed: 11/22/2022]
Abstract
Bullying is a specific form of violence that can potentially lead to numerous and long-term negative health implications. Despite consistent coverage in the media, particularly on cyberbullying, as of yet there are only few representative findings on the frequency of (cyber)bullying in Germany. This article analyses how widespread bullying and cyberbullying were at schools in Germany in 2018, what differences exist between girls and boys, age groups and various types of schools, and changes in bullying trends between 2002 and 2018. Our findings are based on an analysis of the data provided by the 2017/18 cycle (N=4,347 students, 53.0% female) and previous cycles of the German Health Behaviour in School-aged Children (HBSC) study. In the 2018 cycle, boys reported having bullied other children more frequently than girls, but were bullied just as often. 15-year-olds reported having bullied other children more frequently than 11- to- 13-year-olds but reported being bullied less frequently. Students at grammar schools (Gymnasium) least frequently reported any involvement in bullying. Only few children and adolescents reported cases of cyberbullying. Compared to all previous survey years, 2018 saw the lowest number of children that reported having bullied others. However, reports of having been bullied have remained almost stable. The findings highlight the need for evidence-based prevention and intervention anti-bullying programmes and measures across all types of general education schools and age groups.
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Interventionsstrategien und Interventionserfolg von Lehrkräften bei Cybermobbing und traditionellem Mobbing aus Schülersicht. KINDHEIT UND ENTWICKLUNG 2020. [DOI: 10.1026/0942-5403/a000306] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Zusammenfassung. In dieser Studie wird der Frage nachgegangen, ob Lehrkräfte auf unterschiedliche Mobbingarten unterschiedlich reagieren. Dazu werden Angaben von 1.996 Schülerinnen und Schülern aus Sachsen zu tatsächlich stattgefundenen Mobbingsituationen ausgewertet. Sie schätzten neben der dominierenden Mobbingform in der Situation die Reaktion ihrer Lehrkräfte auf die Situation, die gewählte Interventionsstrategie und den Interventionserfolg ein. Am häufigsten werden Fälle verbalen Mobbings berichtet, Cybermobbingfälle hingegen vergleichsweise selten. Die Jugendlichen berichten, dass die meisten Lehrkräfte in den Mobbingsituationen intervenieren, vor allem wenn es sich um Cybermobbing handelt. Aus ihrer Sicht sind Lehrkräfte besonders erfolgreich darin, Cybermobbing zu beenden. Unterstützend-kooperierenden Interventionsstrategien wird von den Schülerinnen und Schülern ein höherer Interventionserfolg bescheinigt als autoritär-strafenden und unterstützend-individuellen Strategien.
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Teachers' self‐efficacy in bullying interventions and their probability of intervention. PSYCHOLOGY IN THE SCHOOLS 2019. [DOI: 10.1002/pits.22229] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Die Genauigkeit des Lehrerurteils bei der Identifikation von an Mobbing beteiligten Schülerinnen und Schülern. PSYCHOLOGIE IN ERZIEHUNG UND UNTERRICHT 2016. [DOI: 10.2378/peu2016.art08d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Strain differences and solvent effects in mouse skin carcinogenesis experiments using carcinogens, tumor initiators and promoters. PROGRESS IN EXPERIMENTAL TUMOR RESEARCH 2015; 26:85-109. [PMID: 6844649 DOI: 10.1159/000407254] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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Abstract
Skin tumors in mice can be induced by the sequential application of a subthreshold dose of a carcinogen (initiation phase) followed by repetitive treatment with a noncarcinogenic tumor promoter. The initiation phase requires only a single application of either a direct-acting carcinogen or a procarcinogen which has to be metabolized before being active; it is essentially an irreversible step which probably involves a somatic cell mutation as evidenced by a good correlation between the carcinogenicity of many chemical carcinogens and their mutagenic activities. There is a good correlation between the skin-tumor-initiating activities of several polycyclic aromatic hydrocarbons (PAH) and their ability to bind covalently to epidermal DNA. Results from our laboratory as well as others suggest that "bay region" diol-epoxides are the ultimate carcinogenic form of PAH carcinogens. Potent inhibitors and stimulators of PAH tumor initiation appear to affect the level of the PAH diol-epoxide reacting with specific DNA bases. REcent data suggest that the tumor-promotion stage involves at least 3 important steps: (1) the induction of embryonic-looking cells (dark cells) in adult epidermis; (2) an increased production of epidermal prostaglandins and polyamines; (3) sustained proliferation of dark cells. Retinoic acid specifically inhibits step 2, whereas the anti-inflammatory steroid fluocinolone acetonide is a potent inhibitor of steps 1 and 3. The mechanism and the importance of a specific sequence for each step in chemical carcinogenesis in mouse skin will be discussed in detail.
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Mitochondrial respiratory uncoupling promotes keratinocyte differentiation and blocks skin carcinogenesis. Oncogene 2012; 31:4725-31. [PMID: 22266853 DOI: 10.1038/onc.2011.630] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Decreased mitochondrial oxidative metabolism is a hallmark bioenergetic characteristic of malignancy that may have an adaptive role in carcinogenesis. By stimulating proton leak, mitochondrial uncoupling proteins (UCP1-3) increase mitochondrial respiration and may thereby oppose cancer development. To test this idea, we generated a mouse model that expresses an epidermal-targeted keratin-5-UCP3 (K5-UCP3) transgene and exhibits significantly increased cutaneous mitochondrial respiration compared with wild type (FVB/N). Remarkably, we observed that mitochondrial uncoupling drove keratinocyte/epidermal differentiation both in vitro and in vivo. This increase in epidermal differentiation corresponded to the loss of markers of the quiescent bulge stem cell population, and an increase in epidermal turnover measured using a bromodeoxyuridine (BrdU)-based transit assay. Interestingly, these changes in K5-UCP3 skin were associated with a nearly complete resistance to chemically-mediated multistage skin carcinogenesis. These data suggest that targeting mitochondrial respiration is a promising novel avenue for cancer prevention and treatment.
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IKKα represses a network of inflammation and proliferation pathways and elevates c-Myc antagonists and differentiation in a dose-dependent manner in the skin. Cell Death Differ 2011; 18:1854-64. [PMID: 21566664 DOI: 10.1038/cdd.2011.56] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Inhibitor of nuclear factor κB kinase-α (IKKα) is required for maintaining skin homeostasis and preventing skin tumorigenesis. However, its signaling has not been extensively investigated. In the present study, we generated two mouse lines that expressed different levels of transgenic IKKα in the basal epidermis under the control of keratin-5 promoter and further evaluated their effects on the major pathways of inflammation, proliferation, and differentiation in the skin. Regardless of the transgenic IKKα levels, the mice develop normally. Because IKKα deletion in keratinocytes blocks terminal differentiation and induces epidermal hyperplasia and skin inflammation, we depleted the endogenous IKKα in these transgenic mice and found that the transgenic IKKα represses epidermal thickness and induces terminal differentiation in a dose-dependent manner. Also, transgenic IKKα was found to elevate expression of Max dimer protein 1 (Mad1) and ovo-like 1, c-Myc antagonists, but repress activities of epidermal growth factor receptor (EGFR), extracellular signal-regulated kinase (ERK), Jun-amino-terminal kinases, c-Jun, signal transducer and activator of transcription 3 (Stat3), and growth factor levels in a dose-dependent fashion in the skin. Moreover, EGFR reduction represses IKKα deletion-induced excessive ERK, Stat3 and c-Jun activities, and skin inflammation. These new findings indicate that elevated IKKα expression not only represses epidermal thickness and induces terminal differentiation, but also suppresses skin inflammation by an integrated loop. Thus, IKKα maintains skin homeostasis through a broad range of signaling pathways.
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Abstract
We previously showed that the EP2 knockout mice were resistant to chemically induced skin carcinogenesis. The purpose of this study was to investigate the role of the overexpression of the EP2 receptor in mouse skin carcinogenesis. To determine the effect of overexpression of EP2, we used EP2 transgenic (TG) mice and wild-type (WT) mice in a DMBA (7,12-dimethylbenz[alpha]anthracene)/TPA (12-O-tetradecanoylphorbol-13-acetate) two-stage carcinogenesis protocol. EP2 TG mice developed significantly more tumors compared with WT mice. Overexpression of the EP2 receptor increased TPA-induced keratinocyte proliferation both in vivo and in vitro. In addition, the epidermis of EP2 TG mice 48 h after topical TPA treatment was significantly thicker compared to that of WT mice. EP2 TG mice showed significantly increased cyclic adenosine monophosphate levels in the epidermis after prostaglandin E2 (PGE2) treatment. The inflammatory response to TPA was increased in EP2 TG mice, as demonstrated by an increased number of macrophages in the dermis. Tumors and 7 x TPA-treated and DMBA-TPA-treated (6 weeks) skins from EP2 TG mice produced more blood vessels than those of WT mice as determined by CD-31 immunostaining. Vascular endothelial growth factor (VEGF) protein expression was significantly increased in squamous cell carcinoma (SCC) samples from EP2 TG mice compared that of WT mice. There was, however, no difference in the number of apoptotic cells in tumors from WT and EP2 TG mice. Together, our results suggest that the overexpression of the EP2 receptor plays a significant role in the protumorigenic action of PGE2 in mouse skin.
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MESH Headings
- Animals
- Animals, Newborn
- Bromodeoxyuridine/metabolism
- Carcinoma, Squamous Cell/blood supply
- Carcinoma, Squamous Cell/metabolism
- Carcinoma, Squamous Cell/pathology
- Cattle
- Cell Culture Techniques
- Cell Proliferation/drug effects
- Female
- Humans
- Hyperplasia
- Inflammation/chemically induced
- Keratinocytes/metabolism
- Keratins/genetics
- Mice
- Mice, Transgenic
- Neovascularization, Pathologic/genetics
- Polymerase Chain Reaction
- Receptors, Prostaglandin E/genetics
- Receptors, Prostaglandin E/metabolism
- Receptors, Prostaglandin E, EP2 Subtype
- Skin Neoplasms/blood supply
- Skin Neoplasms/metabolism
- Skin Neoplasms/pathology
- Tetradecanoylphorbol Acetate/pharmacology
- Up-Regulation
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Abstract
Ultraviolet radiation of mouse skin leads to epidermal hyperplasia, inflammation, and subsequent tumor development. In this study we determined to what extent the cell cycle machinery is altered during epidermal proliferation after ultraviolet B radiation. A minimal erythema dose, 90 mJ per cm2, increased the protein expression of the G1 phase cyclins, cyclin D1 and E, by 12 h. The majority of epidermal cells entered S phase between 18 and 24 h as determined by 5'-bromo-2'-deoxyuridine incorporation, proliferating cell nuclear antigen, and cyclin A immunohistochemistry. An increase in cyclin-dependent kinase 2 (cdk-2) protein expression occurred after 12 h, but no changes in cdk-4 or cdk-6 protein levels were observed. The increase in cyclin D1, E, and A protein expression was associated with an increase in cyclin D1-cdk-4, cyclin E-cdk-2, and cyclin A-cdk-2 complex formation. p53 protein expression was elevated through 48 h, and the cdk inhibitor protein p21(Cip1/WAF1) was elevated 6-fold to 7.5-fold between 12 and 24 h. The elevated p21(Cip1/WAF1) protein contributed to an enhanced association with cdk-2 and cdk-4 at 3-24 h and 6-24 h post-ultraviolet B irradiation, respectively. These data indicate that 90 mJ per cm2 of ultraviolet B irradiation induces a DNA damage response, by increasing p53 and p21(Cip1/WAF1) protein expression, but also induces a rapid and sustained increase in S phase by 18 h.
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Alignment delays in the N = Z nuclei (72)Kr, (76)Sr, and (80)Zr. PHYSICAL REVIEW LETTERS 2001; 87:132501. [PMID: 11580578 DOI: 10.1103/physrevlett.87.132501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2001] [Indexed: 05/23/2023]
Abstract
The ground state rotational bands of the N = Z nuclei (72)Kr, (76)Sr, and (80)Zr have been extended into the angular momentum region where rotation alignment of particles is normally expected. By measuring the moments of inertia of these bands we have observed a consistent increase in the rotational frequency required to start pair breaking, when compared to neighboring nuclei. (72)Kr shows the most marked effect. It has been widely suggested that these "delayed alignments" arise from np-pairing correlations. However, alignment frequencies are very sensitive to shape degrees of freedom and normal pairing, so the new experimental observations are still open to interpretation.
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Distribution of conjugated linoleic acid and metabolites in different lipid fractions in the rat liver. J Lipid Res 2001; 42:1056-61. [PMID: 11441132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2023] Open
Abstract
Conjugated linoleic acid (CLA) is known to provide certain health benefits in experimental animal models. The major CLA isomer in food is c 9,t11-CLA. A primary objective of this study was to investigate the uptake of c 9,t11-CLA and its downstream metabolites into various lipid fractions in the liver of rats fed either a high or low CLA diet (containing 0.1 or 0.8 g CLA/100 g diet, respectively). As expected, the levels of all conjugated diene (CD) fatty acids (CD 18:2 + CD 18:3 + CD 20:3 + CD 20:4) were elevated about 8-fold in the high CLA diet group. However, there was no change in the distribution of CLA and CLA metabolites into various lipid fractions due to CLA intake. Unlike linoleic acid or gamma-linolenic acid, which were distributed mainly in phospholipids, CD 18:2, CD 18:3, and CD 20:3 were incorporated primarily in neutral lipid. Furthermore, the incorporation of all nonconjugated unsaturated fatty acids was not perturbed by CLA. Regardless of the level of CLA in the diet, CD 20:4 was predominantly enriched in phosphatidylserine and phosphatidylinositol. In contrast, arachidonic acid was primarily enriched in phosphatidylcholine and less so in phosphatidylethanolamine. The above findings may have potential implication regarding the role of CLA in modulating eicosanoid metabolism.
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Nonsteroidal anti-inflammatory drugs induce apoptosis in esophageal cancer cells by restoring 15-lipoxygenase-1 expression. Cancer Res 2001; 61:4879-84. [PMID: 11406566] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Abstract
In previous studies, we have found that expression of 15-lipoxygenase-1 (15-LOX-1) and its main product, 13-S-hydroxyoctadecadienoic acid, are decreased in human colorectal cancers and that nonsteroidal anti-inflammatory drugs (NSAIDs) can therapeutically induce 15-LOX-1 expression to trigger apoptosis in human colorectal cancer cells. NSAIDs similarly induce apoptosis in esophageal cancer cells, although the mechanisms of these effects remain to be defined. In the present study, we tested whether 15-LOX-1 is down-regulated in human esophageal cancers using paired normal and tumor human surgical samples and whether NSAIDs can up-regulate 15-LOX-1 to restore apoptosis in esophageal cancer cells. We found that: (a) 15-LOX-1 was down-regulated in human esophageal carcinomas; (b) NSAIDs induced 15-LOX-1 expression during apoptosis in esophageal cancer cells; and (c) 15-LOX-1 inhibition suppressed NSAID-induced apoptosis, which was restored by 13-S-hydroxyoctadecadienoic acid but not by its parent compound, linoleic acid. These findings demonstrate that 15-LOX-1 is down-regulated in human esophageal carcinomas and that NSAIDs induce apoptosis in esophageal cancer cells via up-regulation of 15-LOX-1. They also support the concept that the loss of the proapoptotic role of 15-LOX-1 in epithelial cancers is not limited to human colorectal cancers.
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Abstract
Although MK886 was originally identified as an inhibitor of 5-lipoxygenase activating protein (FLAP), recent data demonstrate that this activity does not underlie its ability to induce apoptosis [Datta, Biswal and Kehrer (1999) Biochem. J. 340, 371--375]. Since FLAP is a fatty-acid binding protein, it is conceivable that MK886 may affect other such proteins. A family of nuclear receptors that are activated by fatty acids and their metabolites, the peroxisome-proliferator-activated receptors (PPARs), have been implicated in apoptosis and may represent a target for MK886. The ability of MK886 to inhibit PPAR-alpha, -beta and -gamma activity was assessed using reporter assay systems (peroxisome-proliferator response element--luciferase). Using a transient transfection system in monkey kidney fibroblast CV-1 cells, mouse keratinocyte 308 cells and human lung adenocarcinoma A549 cells, 10--20 microM MK886 inhibited Wy14,643 activation of PPAR alpha by approximately 80%. Similar inhibition of PPAR alpha by MK886 was observed with a stable transfection reporter system in CV-1 cells. Only minimal inhibitory effects were seen on PPAR beta and PPAR gamma. MK886 inhibited PPAR alpha by a non-competitive mechanism as shown by its effects on the binding of arachidonic acid to PPAR alpha protein, and a dose-response study using a transient transfection reporter assay in COS-1 cells. An assay assessing PPAR ligand-receptor interactions showed that MK886 prevents the conformational change necessary for active-complex formation. The expression of keratin-1, a protein encoded by a PPAR alpha-responsive gene, was reduced by MK886 in a culture of mouse primary keratinocytes, suggesting that PPAR inhibition has functional consequences in normal cells. Although Jurkat cells express all PPAR isoforms, various PPAR alpha and PPAR gamma agonists were unable to prevent MK886-induced apoptosis. This is consistent with MK886 functioning as a non-competitive inhibitor of PPAR alpha, but may also indicate that PPAR alpha is not directly involved in MK886-induced apoptosis. Although numerous PPAR activators have been identified, the results show that MK886 can inhibit PPAR alpha, making it the first compound identified to have such an effect.
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Abstract
In a previous study (Cancer Res 51, 907, 1991) in which we found an inverse relationship between quantity of dietary corn oil and saturated fat, in a constant 15% fat diet, on the tumor promotion stage of skin carcinogenesis, it was not clear whether one or both types of fat played a modulatory role. The purpose of the present study therefore was to compare the effect of 1) increasing corn oil in corn oil-only diets and 2) increasing saturated fat, with a constant level of 5% corn oil, on tumor promotion. In the first study, the effects of five levels of dietary corn oil (5%, 10%, 15%, 20%, and 25%) on the incidence and rat of papilloma and carcinoma development were determined in female Sencar mice fed these diets one week after initiation with 7,12-dimethylbenz[a]anthracene and three weeks before the start of promotion with 12-O-tetradecanoylphorbol-13-acetate. A papilloma incidence of 100% was reached first in the 5% corn oil group, at 10 weeks, followed by the 10% group at 13 weeks and the 15% and 20% group at 16 weeks. The highest corn oil group achieved a 90% incidence. There were marked differences in latency of carcinoma development among the diet groups. At Week 29, the cumulative carcinoma incidence was 56% and 32%, respectively, in the 5% and 10% corn oil groups, whereas the incidence in the two highest corn oil (20% and 25%) groups was only 8% and 4%, respectively. In the second study, the effects of diets containing 5% corn oil and increasing levels of coconut oil (5%, 10%, 15%, and 20%) on the incidence and rat of papilloma and carcinoma development were determined, as described above. No significant difference in latency or incidence of papillomas or carcinomas was noted among these saturated fat diet groups. It thus appears that higher levels of dietary corn oil are associated with a reduced cancer incidence in this model system.
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Transcriptional regulation of intracellular IL-1 receptor antagonist gene by IL-1 alpha in primary mouse keratinocytes. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2001; 166:6149-55. [PMID: 11342635 DOI: 10.4049/jimmunol.166.10.6149] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The inflammatory cytokine IL-1alpha mediates inflammatory reactions in skin and up-regulates the expression of other proinflammatory genes. We previously found that IL-1alpha also increases steady state mRNA levels for intracellular IL-1 receptor antagonist (icIL-1Ra) in primary mouse keratinocytes; however, the mechanism for this was unknown. Here we show that increased expression in primary keratinocytes is due to increased rates of transcription. To study the transcriptional regulation of icIL-1Ra expression induced by IL-1alpha, we functionally characterized 4.5 kb of the 5'-flanking region of the human icIL-1Ra gene. Deletion analysis showed that regulatory elements were contained in the -598- and -288-bp region upstream of the transcription start site. Then we investigated cis- and trans-acting factors required for icIL-1Ra expression and found that a NF-IL-6 site and a NF-kappaB site in the icIL-1Ra promoter were responsible for IL-1alpha-induced icIL-1Ra expression. Moreover, gel shift assays and cotransfection experiments showed that CCAAT/enhancer-binding proteins alpha, beta, and p65 bind to the NF-IL-6 site and NF-kappaB site, respectively, and functionally trans-activate the icIL-1Ra promoter. Finally, mutational analysis confirmed that these elements were both essential for maximal transcription induced by IL-1alpha.
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Abstract
The rates of metabolism of the carcinogenic 2-hydroxybenzo[a]pyrene (2-OH-B[a]P) and the non-carcinogenic 3- and 9-hydroxybenzo[a]pyrenes in cultured cell systems have been studied and compared. While 70-80% of the non-carcinogens are converted to water-soluble derivatives by hamster embryo fibroblasts in 24 h, carcinogenic 2-OH-B[a]P is metabolized at a slower rate (45% in 24 h), comparable to that for the parent hydrocarbon, benzo[a]pyrene (B[a]P). Analysis of extracellular organic solvent-soluble metabolites of 2-OH-B[a]P in cultured hamster embryo fibroblasts, using h.p.l.c., indicates the presence of a single major metabolite, which has been identified by mass spectroscopy as a dihydroxy derivative of B[a]P. At least one additional major organic solvent-soluble metabolite is formed in cultures of either mouse epidermal epithelial cells or human foreskin fibroblasts, indicating a different balance of metabolic pathways in these cell systems. The greater persistence of carcinogenic 2-OH-B[a]P in cells and its higher concentration in the cell cytoplasm compared with the non-carcinogenic phenols may be related to its relatively high biological activity. Differences in metabolism of 2-OH-B[a]P in several cultured cell systems indicate the importance of an appropriate choice of activating system in understanding the relationship between metabolism and carcinogenesis.
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Abstract
Interleukin 1 (IL-1) is a major mediator of inflammation and exerts pleiotropic effects on many systems. To elucidate the role of its endogenous inhibitor, intracellular IL-1 receptor antagonist (icIL-1Ra), in mouse skin, we produced an icIL-1Ra-overexpressing skin carcinoma cell line (icIL-1Ra-JWF2). Altered expression of icIL-1Ra did not change IL-1alpha mRNA levels in these transfected cells. In icIL-1Ra-JWF2 cells, however, cyclooxygenase-2 mRNA levels were dramatically reduced and shown to be transcriptionally regulated by icIL-1Ra. To determine the effect of icIL-1Ra on cell proliferation, cell counts were done 24 h after plating equal numbers of cells. Cells from three icIL-1Ra-JWF2 clones showed significantly reduced growth rates compared with parental JWF2 cells. We subcutaneously injected five independent clones of icIL-1Ra-JWF2 cells into nude mice and measured the tumor doubling time by weekly measurements of tumor volume. IcIL-1Ra appeared to significantly slow the growth of tumors in vivo. Collectively these observations suggest that IL-1Ra has antiproliferative effects in murine skin carcinoma cells.
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Difluoromethylornithine is effective as both a preventive and therapeutic agent against the development of UV carcinogenesis in SKH hairless mice. Carcinogenesis 2001; 22:83-8. [PMID: 11159745 DOI: 10.1093/carcin/22.1.83] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Targeting specific events associated with tumor development represents a rational approach to chemoprevention as well as therapeutic intervention. In this study the ability of difluoromethylornithine (DFMO) to inhibit UV-induced skin carcinogenesis when administered before or after the appearance of tumors was examined. SKH hairless mice were irradiated 3 times per week with 90 mJ/cm(2); this dose was increased by 10% weekly to a maximum of 175 mJ/cm(2). Mice supplied 0.4% DFMO in the drinking water continuously throughout the experiment had an average of 2.0 tumors/mouse (72% incidence) at 30 weeks while controls had an average of 8.2 tumors/mouse (100% incidence). DFMO started after 12 weeks of UV, a time prior to tumor appearance, yielded 3.6 tumors and 100% incidence at 30 weeks. Starting DFMO at 22 weeks, when an average of 2.5 tumors were present, caused regression of tumors for several weeks, followed by a slight rebound. The final tumor number at 30 weeks was 3.0 (96% incidence). Thus, DFMO has strong chemopreventive efficacy, as well as therapeutic activity, against UV-induced skin tumors. Histological and proliferative markers support this conclusion.
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Abstract
Several recent reports have suggested that peroxisome proliferator-activated receptors (PPARs) may be involved in the development of neoplasias in different tissue types. The present study was undertaken to determine whether PPARs play a role in skin physiology and tumorigenesis. In an initiation-promotion study, SENCAR mice treated topically with the PPARalpha ligands conjugated linoleic acid and 4-chloro-6-(2,3-xylidino)-2-pyrimidinylthioacetic acid (Wy-14643) exhibited an approximately 30% lower skin tumor yield compared with mice treated with vehicle. The PPARgamma and PPARdelta activators troglitazone and bezafibrate, respectively, exerted little, if any, inhibitory activity. PPARalpha was detected in normal and hyperplastic skin and in papillomas and carcinomas by immunohistochemistry. In addition, PPARalpha, PPARdelta/PPARbeta, and PPARgamma protein levels were analyzed by immunoblotting in normal epidermis and papillomas. Surprisingly, the levels of all three isoforms were increased significantly in tumors as opposed to normal epidermis. In primary keratinocyte cultures, protein levels of PPARalpha and, to a lesser extent, PPARgamma were markedly increased when the cells were induced to differentiate with high-calcium (0.12 mM) conditions. In addition, we observed that Wy-14643 enhanced transcriptional activity of a peroxisome proliferator-response element-driven promoter in a mouse keratinocyte cell line. These results demonstrate that keratinocytes express functional PPARalpha, that PPARalpha may play a role in differentiation, and that ligands for PPARalpha are moderately protective against skin tumor promotion. We conclude that selective PPARalpha ligands may exert their protective role against skin tumor promotion by ligand activation of PPARalpha.
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15-Lipoxygenase-1 mediates nonsteroidal anti-inflammatory drug-induced apoptosis independently of cyclooxygenase-2 in colon cancer cells. Cancer Res 2000; 60:6846-50. [PMID: 11156377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
We previously found (I. Shureiqi et al., Carcinogenesis (Lond.), 20: 1985-1995, 1999; I. Shureiqi et al, J. Natl. Cancer Inst., 92: 1136-1142, 2000) that (a) 15-lipoxygenase-1 (15-LOX-1) protein and its product 13-S-hydroxyoctadecadienoic acid (13-S-HODE) are decreased; and (b) nonsteroidal anti-inflammatory drug (NSAID)-induced 15-LOX-1 expression is critical to NSAID-induced apoptosis in colorectal cancer cells expressing cyclooxygenase-2 (COX-2). We used the NSAIDs sulindac sulfone (COX-2-independent) and NS-398 (a COX-2 inhibitor) to assess NSAID upregulation of 15-LOX-1 in relation to COX-2 inhibition during NSAID-induced apoptosis in the DLD-1 (COX-2-negative) colon cancer cell line. We found that: (a) NSAIDs up-regulated 15-LOX-1, which preceded apoptosis; and (b) 15-LOX-1 inhibition blocked NSAID-induced apoptosis, which was restored by 13-S-HODE but not by its parent, linoleic acid. NSAIDs can induce apoptosis in colon cancer cells via up-regulation of 15-LOX-1 in the absence of COX-2.
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Abstract
Several recent reports have suggested that peroxisome proliferator-activated receptors (PPARs) may be involved in the development of neoplasias in different tissue types. The present study was undertaken to determine whether PPARs play a role in skin physiology and tumorigenesis. In an initiation-promotion study, SENCAR mice treated topically with the PPARalpha ligands conjugated linoleic acid and 4-chloro-6-(2,3-xylidino)-2-pyrimidinylthioacetic acid (Wy-14643) exhibited an approximately 30% lower skin tumor yield compared with mice treated with vehicle. The PPARgamma and PPARdelta activators troglitazone and bezafibrate, respectively, exerted little, if any, inhibitory activity. PPARalpha was detected in normal and hyperplastic skin and in papillomas and carcinomas by immunohistochemistry. In addition, PPARalpha, PPARdelta/PPARbeta, and PPARgamma protein levels were analyzed by immunoblotting in normal epidermis and papillomas. Surprisingly, the levels of all three isoforms were increased significantly in tumors as opposed to normal epidermis. In primary keratinocyte cultures, protein levels of PPARalpha and, to a lesser extent, PPARgamma were markedly increased when the cells were induced to differentiate with high-calcium (0.12 mM) conditions. In addition, we observed that Wy-14643 enhanced transcriptional activity of a peroxisome proliferator-response element-driven promoter in a mouse keratinocyte cell line. These results demonstrate that keratinocytes express functional PPARalpha, that PPARalpha may play a role in differentiation, and that ligands for PPARalpha are moderately protective against skin tumor promotion. We conclude that selective PPARalpha ligands may exert their protective role against skin tumor promotion by ligand activation of PPARalpha.
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8S-lipoxygenase products activate peroxisome proliferator-activated receptor alpha and induce differentiation in murine keratinocytes. CELL GROWTH & DIFFERENTIATION : THE MOLECULAR BIOLOGY JOURNAL OF THE AMERICAN ASSOCIATION FOR CANCER RESEARCH 2000; 11:447-54. [PMID: 10965849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
To determine the function and mechanism of action of the 8S-lipoxygenase (8-LOX) product of arachidonic acid, 8S-hydroxyeicosatetraenoic acid (8S-HETE), which is normally synthesized only after irritation of the epidermis, transgenic mice with 8-LOX targeted to keratinocytes through the use of a loricrin promoter were generated. Histological analyses showed that the skin, tongue, and stomach of transgenic mice are highly differentiated, and immunoblotting and immunohistochemistries of skin showed higher levels of keratin-1 expression compared with wild-type mice. The labeling index, however, of the transgenic epidermis was twice that of the wild-type epidermis. Furthermore, 8S-HETE treatment of wild-type primary keratinocytes induced keratin-1 expression. Peroxisome proliferator activated receptor alpha (PPARalpha) was identified as a crucial component of keratin-1 induction through transient transfection with expression vectors for PPARalpha, PPARgamma, and a dominant-negative PPAR, as well as through the use of known PPAR agonists. From these studies, it is concluded that 8S-HETE plays an important role in keratinocyte differentiation and that at least some of its effects are mediated by PPARalpha.
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15-LOX-1: a novel molecular target of nonsteroidal anti-inflammatory drug-induced apoptosis in colorectal cancer cells. J Natl Cancer Inst 2000; 92:1136-42. [PMID: 10904086 DOI: 10.1093/jnci/92.14.1136] [Citation(s) in RCA: 122] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Nonsteroidal anti-inflammatory drugs (NSAIDs) appear to act via induction of apoptosis-programmed cell death-as potential colorectal cancer chemopreventive agents. NSAIDs can alter the production of different metabolites of polyunsaturated fatty acids (linoleic and arachidonic acids) through effects on lipoxygenases (LOXs) and cyclooxygenases. 15-LOX-1 is the main enzyme for metabolizing colonic linoleic acid to 13-S-hydroxyoctadecadienoic acid (13-S-HODE), which induces apoptosis. In human colorectal cancers, the expression of this enzyme is reduced. NSAIDs can increase 15-LOX enzymatic activity in normal leukocytes, but their effects on 15-LOX in neoplastic cells have been unknown. We tested the hypothesis that NSAIDs induce apoptosis in colorectal cancer cells by increasing the protein expression and enzymatic activity of 15-LOX-1. METHODS We assessed 15-LOX-1 protein expression and enzymatic activity, 13-S-HODE levels, and 15-LOX-1 inhibition in association with cellular growth inhibition and apoptosis induced by NSAIDs (primarily sulindac and NS-398) in two colorectal cancer cell lines (RKO and HT-29). All P values are two-sided. RESULTS Sulindac and NS-398 progressively increased 15-LOX-1 protein expression in RKO cells (at 24, 48, and 72 hours) in association with subsequent growth inhibition and apoptosis. Increased 13-S-HODE levels and the formation of 15-hydroxyeicosatetraenoic acid on incubation of the cells with the substrate arachidonic acid confirmed the enzymatic activity of 15-LOX-1. Inhibition of 15-LOX-1 in RKO cells by treatment with caffeic acid blocked NS-398-induced 13-S-HODE production, cellular growth inhibition, and apoptosis (P =. 007, P<.0001, and P<.0001, respectively); growth inhibition and apoptosis were restored by adding exogenous 13-S-HODE (P<.0001 for each) but not its parent compound, linoleic acid (P = 1.0 for each). Similar results occurred with other NSAIDs and in HT-29 cells. CONCLUSIONS These data identify 15-LOX-1 as a novel molecular target of NSAIDs for inducing apoptosis in colorectal carcinogenesis.
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Prostaglandin E(2) regulation of cyclooxygenase expression in keratinocytes is mediated via cyclic nucleotide-linked prostaglandin receptors. J Lipid Res 2000; 41:873-81. [PMID: 10828079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023] Open
Abstract
Inflammatory responses are thought to be mediated in part by the prostaglandins derived from arachidonic acid (AA) by the action of prostaglandin H synthase, also referred to as cyclooxygenase (COX). The mitogen-inducible isoform, COX-2, is over-expressed in numerous chronic inflammatory disease conditions and in neoplasms from both human and experimental animal models. COX-1 expression, on the other hand, has been referred to as constitutive or non-inducible. In this study, we present evidence demonstrating autoregulation of prostaglandin (PG) production by the PGs themselves and their precursor, AA. We observed that AA and PGs induced COX-2, as well as COX-1, expression in cultured murine keratinocytes approximately 3 h after treatment. In primary keratinocytes transiently transfected with a full-length COX-2 promoter linked to a luciferase reporter gene, we observed enhanced transcription by AA, PGE(2), and the other prostaglandins. Forskolin, a known activator of adenylate cyclase, and dibutryl-cAMP, a cAMP analog, induced COX-1 and COX-2 mRNA, suggesting that cAMP is a second messenger for COX expression. SQ 22536, an adenylate cyclase inhibitor, inhibited COX-2 mRNA induction by PGE(2) in a dose-dependent manner suggesting that PGE(2)-induced expression may be through one of the cAMP-linked PGE(2) receptors. The results of this study demonstrate that both COX-1 and COX-2 are inducible. Further, both COX isoforms can be up-regulated by their products, the PGs, and this autoregulation probably occurs via prostaglandin receptors linked to a cAMP signal transduction pathway.
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Evidence for collective oblate rotation in N = Z 68Se. PHYSICAL REVIEW LETTERS 2000; 84:4064-4067. [PMID: 10990611 DOI: 10.1103/physrevlett.84.4064] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/1999] [Indexed: 05/23/2023]
Abstract
A gamma-ray spectroscopic measurement of the N = Z nucleus 68Se has been made following the 12C(58Ni,2n) reaction at 185 and 220 MeV using Gammasphere and the Argonne Fragment Mass Analyzer. Despite a very low production cross section of 200(50) &mgr;b, two distinct rotational bands were found; the ground state band consistent with oblate collective rotation, and an excited band consistent with prolate rotation. These observations support long-standing predictions that nuclear ground states with substantial oblate (beta(2) approximately -0.3) deformation should exist in this region.
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Development and initial characterization of several new inbred strains of SENCAR mice for studies of multistage skin carcinogenesis. Carcinogenesis 2000; 21:641-6. [PMID: 10753198 DOI: 10.1093/carcin/21.4.641] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The development and initial characterization of five new inbred strains of SENCAR mice are described in this paper. Ten randomly selected pairs of outbred SENCAR mice were mated and offspring from each separately maintained parental line were sib mated at each successive generation to result in inbred strains. Due to poor reproductive performance only five of the original 10 lines were bred to homogeneity. Initial characterization of the five remaining lines (referred to as SL2/sprd, SL5/sprd, SL7/sprd, SL8/sprd and SLl0/sprd) at F12 for their responsiveness to a two-stage carcinogenesis protocol (10 nmol 7,12-dimethylbenz[a]anthracene and 0.25 microg 12-O-tetradecanoylphorbol-13 acetate) revealed three groups of responders in terms of the number of papillomas per mouse: SL2/sprd and SL8/sprd > SL7/sprd and SL10/sprd >> SL5/sprd. The papilloma responses in SL2/sprd and SL8/sprd were very similar to SENCAR B/Pt compared at the same doses. Papillomas induced on SL2/sprd had the highest propensity to progress to squamous cell carcinomas, similar to that observed in outbred SENCAR and SENCAR B/Pt mice. More detailed comparison of the responsiveness of SL2/sprd and SL5/sprd at Fl5 showed that these two inbred strains differed in their sensitivity to TPA-induced epidermal hyperplasia and that the dose of TPA required to produce a tumor response in SL5/sprd in comparison with that in SL2/sprd was 4-20 times higher. Overall, the availability of the different inbred SENCAR strains will greatly aid mechanistic studies of multistage skin carcinogenesis as well as studies to understand the underlying genetic basis of resistance to tumor promotion and progression in this model system.
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Abstract
Several types of epithelial neoplasms exhibit high expression of transforming growth factor beta1 (TGFbeta-1), indicating that they have acquired tolerance to this normally growth inhibitory cytokine. Since cyclin D1 is expressed at high levels in murine skin tumors coincident with high levels of TGFbeta-1 expression, we hypothesized that cyclin D1 may override TGFbeta-1 induced growth arrest. We observed that in primary murine keratinocytes treated with TGFbeta-1, cyclin D1 is quickly suppressed at both the mRNA and protein level. Since changes in other cell cycle proteins occur at a later time during TGFbeta-1 treatment, the early suppression of cyclin D1 suggests that this gene is a critical target for TGFbeta-1 growth suppression. Using primary keratinocytes from transgenic mice that overexpress cyclin D1 (K5-D1 mice), we observed partial resistance to TGFbeta-1 growth inhibition. This resistance involves changes in the cyclin/cdk/inhibitor complexes rather than differences in expression of the TGFbeta receptors or signaling. Comparison of cdk associated kinase activity between wild-type and K5-D1 cells shows differential regulation. We conclude that deregulated cyclin D1 and subsequent alterations in cell cycle machinery provides keratinocytes the ability to at least partially override growth inhibitory signals.
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Mechanism(s) of activation of secretory phospholipase A(2)s in mouse keratinocytes. J Lipid Res 1999; 40:1701-9. [PMID: 10484618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/13/2023] Open
Abstract
The differential activation of different members of the phospholipase A(2) (PLA(2)) superfamily and their regulation are important as one or more of them regulates the production of eicosanoids and others may contribute to the formation of other lipid mediators. We previously reported the existence of two forms of secretory or sPLA(2) in mouse keratinocytes, namely type I and type II sPLA(2). We show here that mouse keratinocyte sPLA(2)s were potently activated by protease treatment and inhibited by protease inhibitors. We also observed that G protein effectors induced substantial release of oleic acid (OA) from prelabeled mouse keratinocytes. A G(i)/G(0) protein activator significantly enhanced the hydrolysis of OA and this increase was not responsive to either pertussis toxin or cholera toxin treatment. Although there was a significant negative correlation between intracellular cAMP levels and OA hydrolysis, experimentally increasing cAMP with forskolin treatment had no effect on sPLA(2) activity. Arachidonic acid but not its metabolites was also shown to marginally activate keratinocyte sPLA(2) by 1.5-fold. These results lead to the conclusion that mouse keratinocyte sPLA(2)s can be regulated primarily by proteolytic activation and a G protein pathway.
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Chemopreventive activity of celecoxib, a specific cyclooxygenase-2 inhibitor, and indomethacin against ultraviolet light-induced skin carcinogenesis. Mol Carcinog 1999; 25:231-40. [PMID: 10449029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/13/2023]
Abstract
Epidemiological and dietary studies suggest that nonsteroidal anti-inflammatory drugs (NSAIDs) reduce the risk of colon cancer, possibly through a mechanism involving inhibition of cyclooxygenase (COX)-2, which is overexpressed in premalignant adenomatous polyps and colon cancer. Because ultraviolet light (UV) can induce COX-2 and nonspecific NSAIDs can decrease UV-induced skin cancer, we evaluated the ability of two compounds, celecoxib (a specific COX-2 inhibitor) and indomethacin (a nonspecific NSAID), to block UV-induced skin tumor development in SKH:HR-1-hrBr hairless mice. Mice fed 150 or 500 ppm celecoxib showed a dose-dependent reduction (60% and 89%, respectively) in tumor yield. Indomethacin (4ppm) reduced tumor yield by 78%. Although both acute and chronic UV exposure increased cell proliferation and edema, neither compound reduced these parameters. In contrast, UV-induced prostaglandin synthesis in the epidermis was effectively blocked by both compounds. UV-induced increases in COX-2 expression in skin were also not altered in any of the treatment groups. Similarly, tumors that constitutively express high levels of COX-2 displayed no reduction by treatment with celecoxib or indomethacin. The dramatic protective effects of celecoxib suggests that specific COX-2 inhibitors may offer a way to safely reduce the risk of skin cancer in humans.
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Altered expression of interleukin-1 receptor antagonist in different stages of mouse skin carcinogenesis. Mol Carcinog 1999; 24:276-86. [PMID: 10326864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
Interleukin-1 receptor antagonist (IL-1Ra) is an endogenous inhibitor of interleukin-1. The expression of IL-1Ra and interleukin-1alpha (IL-1alpha) was measured in murine epidermis after treatment with tumor promoters and in tumor cell lines. A single treatment with three different tumor promoters (12-O-tetradecanoylphorbol-13-acetate (TPA), anthralin, and thapsigargin) induced IL-1Ra mRNA with different kinetics in mouse skin. The expression of IL-1Ra mRNA also was induced by TPA and IL-1alpha in a dose-related and time-dependent manner in cultured mouse keratinocytes. Expression of IL-1Ra mRNA peaked 6 h after treatment. Both IL-1Ra and IL-1alpha protein and IL-1Ra and IL-1alpha mRNA were measured in various keratinocyte tumor cell lines (C50, MT1/2, HEL30, JWF2, CH72, and BPCC2). The expression of IL-1alpha was increased in papilloma and squamous cell carcinoma cell lines. IL-1Ra protein also was increased in nontumorigenic and papilloma cell lines; however, the expression was dramatically reduced in some carcinoma cell lines. Finally, we detected IL-1alpha and IL-1Ra protein in mouse skin tumors by western blot analysis, and localization was assessed by immunohistochemical analysis. Positive staining for both IL-1alpha and IL-1Ra was observed in the cytoplasm and was most prominent in the suprabasal layer. Although IL-1Ra protein increased in papillomas and carcinomas, IL-1alpha protein was not significantly increased above basal level in most tumors.
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MESH Headings
- 9,10-Dimethyl-1,2-benzanthracene
- Animals
- Anthralin
- Blotting, Northern
- Blotting, Western
- Carcinogens
- Carcinoma, Squamous Cell/chemically induced
- Carcinoma, Squamous Cell/genetics
- Carcinoma, Squamous Cell/metabolism
- Cell Polarity
- Cytoplasm/chemistry
- Disease Progression
- Epidermis/drug effects
- Epidermis/metabolism
- Epidermis/pathology
- Gene Expression Regulation, Neoplastic
- Hyperplasia
- Inflammation
- Interleukin 1 Receptor Antagonist Protein
- Interleukin-1/biosynthesis
- Interleukin-1/genetics
- Keratinocytes/drug effects
- Keratinocytes/metabolism
- Mice
- Mice, Inbred SENCAR
- Neoplasm Proteins/biosynthesis
- Neoplasm Proteins/genetics
- Papilloma/chemically induced
- Papilloma/genetics
- Papilloma/metabolism
- Precancerous Conditions/chemically induced
- Precancerous Conditions/genetics
- Precancerous Conditions/metabolism
- RNA, Messenger/metabolism
- RNA, Neoplasm/metabolism
- Sialoglycoproteins/biosynthesis
- Sialoglycoproteins/genetics
- Skin Diseases/chemically induced
- Skin Diseases/genetics
- Skin Diseases/metabolism
- Skin Neoplasms/chemically induced
- Skin Neoplasms/genetics
- Skin Neoplasms/metabolism
- Tetradecanoylphorbol Acetate
- Thapsigargin
- Tumor Cells, Cultured
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Mechanism-based cancer prevention approaches: targets, examples, and the use of transgenic mice. J Natl Cancer Inst 1999; 91:215-25. [PMID: 10037099 DOI: 10.1093/jnci/91.3.215] [Citation(s) in RCA: 119] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Humans are exposed to a wide variety of carcinogenic insults, including endogenous and man-made chemicals, radiation, physical agents, and viruses. The ultimate goal of carcinogenesis research is to elucidate the processes involved in the induction of human cancer so that interventions may be developed to prevent the disease, either in the general population or in susceptible subpopulations. Progress to date in the carcinogenesis field, particularly regarding the mechanisms of chemically induced cancer, has revealed several points along the carcinogenesis pathway that may be amenable to mechanism-based prevention strategies. The purpose of this review is to examine the basic mechanisms and stages of chemical carcinogenesis, with an emphasis on ways in which preventive interventions can modify those processes. Possible ways of interfering with tumor initiation events include the following: i) modifying carcinogen activation by inhibiting enzymes responsible for that activation or by direct scavenging of DNA-reactive electrophiles and free radicals; ii) enhancing carcinogen detoxification processes by altering the activity of the detoxifying enzymes; and iii) modulating certain DNA repair processes. Possible ways of blocking the processes involved in the promotion and progression stages of carcinogenesis include the following: i) scavenging of reactive oxygen species; ii) altering the expression of genes involved in cell signaling, particularly those regulating cell proliferation, apoptosis, and differentiation; and iii) decreasing inflammation. In addition, the utility for mechanism-based cancer prevention research of new animal models that are based on the overexpression or inactivation of specific cancer-related genes is examined.
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Abstract
Differentiation of cells is typically marked by a cessation of proliferation with a concurrent entrance into a distinct metabolic state marked by tissue specific gene expression. The mechanism by which the cell exits the cell cycle in this process is poorly understood. To determine the potential roles of the cell cycle machinery in the regulation of the terminal differentiation process of epidermal cells, we selected a well characterized in vitro model in which primary mouse keratinocytes are induced to differentiate in response to a raised calcium ion concentration in the medium. The withdrawal from the cell cycle correlates very well with a number of changes in the cell cycle machinery. Changes in the phosphorylation status of the Rb family of proteins occurs coordinately with an increased association of p21, p27 and p57 with cdk2. Furthermore, we find that inhibition of cdk2 activity is not sufficient to elicit changes that occur during keratinocyte differentiation. Finally, the previously described v-Ha-ras block of keratinocyte differentiation correlates with altered regulation of both cyclin D1 and cdk2 suggesting that these genes may play a role in the Ha-ras transformation of a keratinocyte.
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Abstract
Despite the benefits of sunscreens, ultraviolet (UV) exposure can still lead to skin cancer. In this study we investigated the effect of topical application of the antioxidant vitamin E acetate (VEA) on the inhibition of UV-induced carcinogenesis. Hairless SKH-1 mice received 5.2 mg of VEA 30 min before (VEA/UV) or after (UV/ VEA) a single minimal erythemic dose of UV light. Vehicle-control animals received acetone 30 min before UV exposure (Ace/UV). After 24 h, cyclobutane dimer repair was twofold and 1.5-fold greater in the UVNEA and VEA/UV groups, respectively. Expression of p53 protein in the UV/VEA group was maximum at 12 h after UV exposure, whereas in the Ace/UV- and VEA/UV-treated mice, maximum p53 immunostaining was statistically higher at 15 h (P = 0.03). DNA synthesis as determined by 5-bromo-2'-deoxyuridine incorporation was twofold higher after 15 h in all groups but was not statistically different among treatment groups. Protein levels of cyclin D1 and p21 were increased in both VEA groups by 6 h. In addition, VEA treatments delayed tumor formation and yield for the first 20 wk, although this difference was lost by 30 wk. The telomerase activity of carcinomas from the UV/VEA-treated mice was statistically lower than that of the Ace/UV-treated mice (P = 0.05). This study showed that although VEA may mitigate some of the initial events associated with UV irradiation such as DNA damage and p53 expression, it has limited potential in preventing UV-induced proliferation and tumor formation.
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Transcriptional regulation of cyclooxygenase-2 in mouse skin carcinoma cells. Regulatory role of CCAAT/enhancer-binding proteins in the differential expression of cyclooxygenase-2 in normal and neoplastic tissues. J Biol Chem 1998; 273:27686-94. [PMID: 9765305 DOI: 10.1074/jbc.273.42.27686] [Citation(s) in RCA: 168] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Many studies have suggested that overexpression of cyclooxygenase-2 (COX-2) contributes to the development of tumors in several tissues. COX-2 expression tends to be up-regulated in various types of tumors and transformed cell lines, and the overexpression of COX-2 is caused by enhanced transcription of the gene. In an attempt to characterize the signaling pathway leading to the overexpression of COX-2 in the mouse skin carcinoma cell line JWF2, we investigated cis- and trans-acting factors required for COX-2 expression and demonstrated a molecular mechanism by which COX-2 is expressed differentially in normal and neoplastic tissues. Two regions of the COX-2 promoter containing an E-box and nuclear factor IL6 site were identified as the positive regulatory elements through transient transfections with luciferase reporter vectors containing the various 5'-flanking regions of the promoter. Moreover, electrophoretic mobility shift assays and cotransfection experiments showed that upstream stimulatory factors and CCAAT/enhancer-binding proteins (C/EBPs) bind to the E-box and nuclear factor IL6 site, respectively, and functionally transactivate the COX-2 promoter. We also found that C/EBP isoforms are expressed differentially during mouse skin carcinogenesis, suggesting that overexpression of COX-2 in tumors may be caused by a change in C/EBP expression levels.
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Suppression or elevation of cytosolic phospholipase A2 alters keratinocyte prostaglandin synthesis, growth, and apoptosis. Cancer Res 1998; 58:4624-31. [PMID: 9788614] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Prostaglandins and other arachidonic acid (AA) metabolites are synthesized by keratinocytes in response to tumor promoters and are produced at very high levels in tumors. After phorbol ester treatment, AA is hydrolyzed from keratinocytes primarily by the cytosolic form of phospholipase A2 (cPLA2), which exhibited a strong substrate preference for phosphatidylcholine over phosphatidylethanolamine and AA over other fatty acids. Phorbol esters increase cPLA2 activity but not the level of expression. To dissociate increased cPLA2 activity from other phorbol ester effects and thus determine the effects of altered AA release on cell growth, the murine keratinocyte cell line, HEL-30, was stably transfected with the sense or antisense cDNA for cPLA2. The resulting cell lines displayed corresponding over- or underexpression and up to 23-fold differences in cPLA2 activity between them. Phorbol ester caused a 15-fold difference in AA release between sense and antisense transfectants. Prostaglandin E2 levels correlated with AA release levels. The sense transfectants showed an enhanced proliferative capacity, based on increased cell number over time and [3H]thymidine incorporation. The antisense transfectants had significantly (>60%) reduced growth rates, compared with both parental cells and sense transfectants. The extent of apoptosis was determined in tumors from cell lines grown in graft chambers in vivo. The number of apoptotic cells was significantly greater in tumors from the sense transfectants, based on terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling staining, compared with the parental or antisense lines. These data are in agreement with a recent study (M. C. Stern et al., Mol. Carcinog., 20: 137-142, 1997) showing a correlation between increased apoptosis and tumor progression in this model system. These results suggest that the elevated eicosanoid synthesis that is observed in skin carcinomas contributes to the growth and progression of these tumors.
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Regulation of arachidonic acid release and metabolism by tumor promoters. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1998; 400A:433-8. [PMID: 9547587 DOI: 10.1007/978-1-4615-5325-0_58] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Identification and characterization of several forms of phospholipase A2 in mouse epidermal keratinocytes. J Lipid Res 1998; 39:569-82. [PMID: 9548589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA) stimulated the release of arachidonic acid (AA) from mouse keratinocytes. A distinct difference was observed between the fatty acid release profile elicited by TPA and other stimuli. These findings led to the investigation of keratinocyte phospholipase A2 (PLA2), which catalyzes the release of sn-2 fatty acids from membrane phospholipids and regulates the production of eicosanoids. We characterized and identified several forms of PLA2 in mouse keratinocytes, a cytosolic or cPLA2 and two secretory or sPLA2s in the membrane. The PLA2 in keratinocyte cytosol is sensitive to heating and acid treatment, while resistant to reducing reagent. The PLA2 in keratinocyte membrane is resistant to heating and acid treatment, while sensitive to reducing reagent. These characteristics suggested the presence of a cPLA2 and at least one type of sPLA2. Inhibitor data further confirmed the identities of these PLA2s. The cPLA2 was activated by TPA, and appeared to be responsible for the majority of the specific release of AA observed in mouse keratinocytes treated with TPA. The calcium ionophore A23187, and 4alpha-TPA did not elicit the selectivity towards AA observed with TPA. The release of linoleic acid (LA) and oleic acid (OA) from A23187- and 4alpha-TPA-treated keratinocytes suggests activation of sPLA2. These activities may be due to the existence of both type I and type II sPLA2, as both were identified by polymerase chain reactions. In conclusion, keratinocytes express several forms of phospholipase A2 that differ in their substrate specificities and mechanisms of activation, resulting in distinct agonist-specific fatty acid release profiles.
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Analysis of two inbred strains of mice derived from the SENCAR stock with different susceptibility to skin tumor progression. Carcinogenesis 1998; 19:125-32. [PMID: 9472703 DOI: 10.1093/carcin/19.1.125] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The SENCAR stock of mice has proved to be a useful model in dissecting out the multistage nature as well as the critical mechanisms involved in skin tumorigenesis. This outbred stock was selectively bred to be susceptible to initiation with 7,12-dimethylbenz[a]anthracene (DMBA) and promotion with 12-O-tetradecanoylphorbol-13-acetate (TPA). In order to obtain mice more suitable for genetic analyses of tumor susceptibility and tissue transplantation studies, several inbred lines of mice were derived from the SENCAR stock. One of these lines, the SSIN mice, has a higher susceptibility to tumor promotion compared to the SENCAR stock but is very resistant to tumor progression. On the other hand, the SENCAR B/Pt mice, derived also from the outbred stock, not only have a tumor promotion susceptibility almost identical to the SSIN mice, but they also have a high susceptibility to tumor progression. In order to understand the nature of the phenotypic differences between these two inbred lines we have characterized them using several parameters and markers that are associated with the progression of papillomas to squamous cell carcinoma (SCC). In this sense we analysed the tumor multiplicity and SCC incidence, and the expression of markers of progression and cell cycle related proteins in papillomas derived from both strains. Our results showed that while both strains have a similar papilloma multiplicity and incidence the SENCAR B/Pt mice have 67% incidence of SCC, compared to 0% in the SSIN. SENCAR B/Pt papillomas at 30 weeks of promotion have a higher and aberrant expression of K13, and loss of connexin 26. TGF-beta1 was found to be over-expressed in the suprabasal and superficial cells in the SENCAR B/Pt papillomas, while it was only expressed in the superficial cell layer in those derived from SSIN. The SENCAR B/Pt papillomas also showed an enlarged proliferative compartment with overexpression of cyclin D1 and PCNA as seen by immunohistochemistry and Western blot.
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Abstract
The scatter plot is a commonly used assessment tool for identifying temporal patterns in the occurrence of behavior problems. However, the extent to which such patterns are frequently observed is unknown because little research has evaluated the general utility of the scatter plot. We conducted a large-scale analysis of within- and across-day occurrences of problem behavior by conducting continuous observations of 20 individuals living in four residential facilities. Data were recorded during 30-min intervals throughout participants' waking hours for 30 days by direct care staff and were converted into scatter plot formats. Five sets of data were excluded from further analysis due to poor interobserver agreement (below 80%). Visual analysis of the remaining 15 scatter plots indicated that none showed any reliable temporal pattern of responding. However, when the data were transformed into aggregate "control charts" based on statistical process control procedures, 12 of the 15 sets of data revealed one or more 30-min intervals during which problem behavior was more likely to occur. Results are discussed in terms of the practicality of applying statistical analyses to scatter plot data and of collecting data for the length of time needed to show statistical significance. It was concluded that detailed functional or descriptive analyses, which would reveal cause-effect or correlational relationships between behavior and specific environmental events, may be both more precise and more efficient forms of assessment.
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Differential activation of keratinocyte phospholipase A2S by tumor promoters and other irritants. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1997; 407:117-21. [PMID: 9321941 DOI: 10.1007/978-1-4899-1813-0_18] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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Abstract
Prostaglandins (PGs) are lipids produced enzymatically and nonenzymatically from 20 carbon fatty acids, particularly arachidonic acid. Prostaglandins and related metabolites (collectively referred to as eicosanoids), including the thromboxanes, prostacyclins, hydroperoxy and hydroxy fatty acids, and leukotrienes are produced by most tissues of the body by oxidation of arachidonic acid, although the amount and class of product varies with cell type. The biological action of many of these eicosanoids as key regulators of cell processes that range from proliferation to adhesion and migration are currently being elucidated. An association of high levels of PGs and their synthetic enzymes, the PG synthases/cyclooxygenases, have been noted for many of the major types of cancer. Prostaglandins may contribute to the cancer processes through one or more of several mechanisms including increased proliferation, apoptosis, enhanced carcinogen metabolism or modulation of the immune system. The recent understanding of the regulation of substrate availability and of the regulation (or dysregulation in many neoplasias) of the synthetic enzymes has opened avenues leading to the design of isozyme specific inhibitors and better cancer prevention strategies. However, the apoptosis caused by these inhibitors as well as other drugs has raised some question concerning the relative importance of PGs. This is an issue that remains to be resolved.
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Epidermal proliferation but not quantity of DNA photodamage is correlated with UV-induced mouse skin carcinogenesis. J Invest Dermatol 1997; 109:340-7. [PMID: 9284102 DOI: 10.1111/1523-1747.ep12335984] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The hairless SKH-1 mouse strain has a higher skin tumor incidence, shorter tumor latency, and higher tumor yield in response to ultraviolet (UV) irradiation than the SENCAR strain. In this study we assessed the differences in UV susceptibility of both strains by measuring DNA photodamage and epidermal proliferation after one UV treatment and after 1, 3, 6, and 9 wk of chronic UV irradiation. Induction rates for cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts [(6-4) PDs] were significantly greater in the SKH-1 strain than the SENCAR strain, but no strain differences in repair kinetics were detected for CPDs or (6-4) PDs. With chronic UV exposure we observed the following: (i) there was an equal amount of DNA photodamage in both strains; (ii) the number of (6-4) PDs was significantly greater than the CPDs after 6 wk; (iii) there were a significantly greater number of epidermal cells (1.5-fold increase) in the SKH-1 strain; (iv) the number of cycling cells, as measured by 5-bromo-2'-deoxyuridine (BrdU), were located both basally and suprabasally and were significantly greater in the SKH-1 strain; and (v) the number of cells immunoreactive to p53 was equivalent in both strains, but immunoreactive cells were located suprabasally in the SKH-1 strain after 9 wk of UV. These results show that the etiologic role of UV in tumorigenesis is dependent on events other than the amount of DNA photodamage in mouse epidermis.
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Changes in protein expression during multistage mouse skin carcinogenesis. Mol Carcinog 1997; 20:125-36. [PMID: 9328443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
To directly compare the expression patterns of different proteins known to be altered during mouse skin carcinogenesis, serial sections of normal and hyperplastic skin and tumors from various stages of 7,12-dimethylbenz[a]anthracene-initiated, 12-O-tetradecanoylphorbol-13-acetate-promoted female SENCAR mice were examined by immunohistochemistry. In untreated, normal mouse skin, keratin 1 (K1) and transforming growth factor-beta1 (TGFbeta1) were strongly expressed in the suprabasal layers, whereas integrin alpha6beta4 was expressed only in basal cells and only moderate staining for transforming growth factor-alpha (TGFalpha) was seen. In hyperplastic skin, TGFalpha expression became stronger, whereas expression of another epidermal growth factor (EGF) receptor ligand, heparin-binding EGF-like growth factor (HB-EGF), was strongly induced in all epidermal layers from no expression in normal skin. Likewise, the gap-junctional protein connexin 26 (Cx26) became highly expressed in the differentiated granular layers of hyperplastic skin relative to undetectable expression in normal skin. Expression of cyclin D1 in the proliferative cell compartment was seen in all benign and malignant tumors but not in hyperplastic skin. Beginning with very early papillomas (after 10 wk of promotion), expression of alpha6beta4 in suprabasal cells and small, focal staining for keratin 13 (K13) were seen in some tumors. Later (after 20-30 wk), focal areas of gamma-glutamyl transpeptidase (GGT) activity appeared in a few papillomas, whereas TGFbeta1 expression began to decrease. Cx26 and TGFalpha staining became patchier in some late-stage papillomas (30-40 wk), whereas suprabasal alpha6beta4, K13, and GGT expression progressively increased and K1 expression decreased. Finally, in squamous cell carcinomas (SCCs), there was an almost complete loss of K1 and a further decline in TGFalpha, HB-EGF, TGFbeta1, and Cx26 expression. On the other hand, almost all SCCs showed suprabasal staining for alpha6beta4 and widespread cyclin D1 and K13 expression, whereas only about half showed positive focal staining for GGT activity.
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