RESUMO
The selenoprotein glutathione peroxidase-2 (GPx2) appears to have a dual role in carcinogenesis. While it protected mice from colon cancer in a model of inflammation-triggered carcinogenesis (azoxymethane and dextran sodium sulfate treatment), it promoted growth of xenografted tumor cells. Therefore, we analyzed the effect of GPx2 in a mouse model mimicking sporadic colorectal cancer (azoxymethane-treatment only). GPx2-knockout (KO) and wild-type (WT) mice were adjusted to an either marginally deficient (-Se), adequate (+Se), or supranutritional (++Se) selenium status and were treated six times with azoxymethane (AOM) to induce tumor development. In the -Se and ++Se groups, the number of tumors was significantly lower in GPx2-KO than in respective WT mice. On the +Se diet, the number of dysplastic crypts was reduced in GPx2-KO mice. This may be explained by more basal and AOM-induced apoptotic cell death in GPx2-KO mice that eliminates damaged or pre-malignant epithelial cells. In WT dysplastic crypts GPx2 was up-regulated in comparison to normal crypts which might be an attempt to suppress apoptosis. In contrast, in the +Se groups tumor numbers were similar in both genotypes but tumor size was larger in GPx2-KO mice. The latter was associated with an inflammatory and tumor-promoting environment as obvious from infiltrated inflammatory cells in the intestinal mucosa of GPx2-KO mice even without any treatment and characterized as low-grade inflammation. In WT mice the number of tumors tended to be lowest in +Se compared to -Se and ++Se feeding indicating that selenium might delay tumorigenesis only in the adequate status. In conclusion, the role of GPx2 and presumably also of selenium depends on the cancer stage and obviously on the involvement of inflammation.
Assuntos
Adenoma/enzimologia , Neoplasias do Colo/enzimologia , Glutationa Peroxidase/genética , Adenoma/induzido quimicamente , Adenoma/imunologia , Animais , Antioxidantes/administração & dosagem , Apoptose , Azoximetano , Carcinogênese/induzido quimicamente , Carcinogênese/metabolismo , Neoplasias do Colo/induzido quimicamente , Neoplasias do Colo/imunologia , Dieta , Suplementos Nutricionais , Células Epiteliais/fisiologia , Deleção de Genes , Glutationa Peroxidase/deficiência , Humanos , Mucosa Intestinal/imunologia , Mucosa Intestinal/patologia , Camundongos , Camundongos da Linhagem 129 , Camundongos Endogâmicos C57BL , Camundongos Knockout , Lesões Pré-Cancerosas/induzido quimicamente , Lesões Pré-Cancerosas/enzimologia , Antígeno Nuclear de Célula em Proliferação/metabolismo , Selênio/administração & dosagem , beta Catenina/metabolismoRESUMO
This paper is concerned with evaluating whether an interaction between two sets of risk factors for a binary trait is removable and, when it is removable, fitting a parsimonious additive model using a suitable link function to estimate the disease odds (on the natural logarithm scale). Statisticians define the term 'interaction' as a departure from additivity in a linear model on a specific scale on which the data are measured. Certain interactions may be eliminated via a transformation of the outcome such that the relationship between the risk factors and the outcome is additive on the transformed scale. Such interactions are known as removable interactions. We develop a novel test statistic for detecting the presence of a removable interaction in case-control studies. We consider the Guerrero and Johnson family of transformations and show that this family constitutes an appropriate link function for fitting an additive model when an interaction is removable. We use simulation studies to examine the type I error and power of the proposed test and to show that, when an interaction is removable, an additive model based on the Guerrero and Johnson link function leads to more precise estimates of the disease odds parameters and a better fit. We illustrate the proposed test and use of the transformation by using case-control data from three published studies. Finally, we indicate how one can check that, after transformation, no further interaction is significant.
Assuntos
Bioestatística/métodos , Doença/etiologia , Adenoma/enzimologia , Adenoma/etiologia , Análise de Variância , Aromatase/genética , Arilamina N-Acetiltransferase/metabolismo , Estudos de Casos e Controles , Neoplasias Colorretais/etiologia , Doença/genética , Neoplasias do Endométrio/enzimologia , Neoplasias do Endométrio/etiologia , Feminino , Humanos , Modelos Lineares , Modelos Logísticos , Modelos Estatísticos , Fatores de Risco , Fumar/efeitos adversos , Chá , Neoplasias da Bexiga Urinária/enzimologia , Neoplasias da Bexiga Urinária/etiologiaRESUMO
BACKGROUND: Elevated plasma total homocysteine (tHcy) is an accepted marker of functional folate deficiency but may have independent effects on colorectal neoplasia risk. It is uncertain whether plasma tHcy is associated with risk at the low levels common in a folate-fortified population. METHODS: Study subjects, about half of whom were recruited after fortification of grain products with folic acid in the United States and Canada, consisted of 871 individuals with a recent history of one or more colorectal adenomas who were randomized to receive either a 1 mg/day folic acid supplement or a placebo within one of three randomly assigned aspirin treatment groups (placebo, 81, or 325 mg/day). Nonfasting plasma tHcy was determined by a gas chromatograph mass chromatography method. We estimated adjusted risk ratios and 95% confidence intervals (95% CI) for one or more adenoma recurrences for each quartile of baseline plasma tHcy using generalized linear regression with an overdispersed Poisson approximation to the binomial. RESULTS: The Q4/Q1 adjusted risk ratio for any adenoma was 0.98 (95% CI, 0.70-1.38; P trend = 0.17) in the placebo group, and 0.81 (95% CI, 0.58-1.12; P-trend = 0.17) in the folic acid group. Results were similar for adenomas with advanced features. There was no modification by sex, aspirin treatment group or MTHFR 677C>T genotype. CONCLUSIONS: Plasma tHcy is not an independent marker for an increase in colorectal adenoma recurrence risk in postfortification populations in which plasma tHcy levels are in the lower range of values. IMPACT: Controlling plasma tHcy levels is unlikely to favorably modify adenoma recurrence risk in folate-fortified populations.
Assuntos
Adenoma/sangue , Aspirina/uso terapêutico , Neoplasias Colorretais/sangue , Ácido Fólico/uso terapêutico , Homocisteína/sangue , Recidiva Local de Neoplasia/sangue , Adenoma/enzimologia , Adenoma/prevenção & controle , Adulto , Idoso , Idoso de 80 Anos ou mais , Aspirina/sangue , Neoplasias Colorretais/enzimologia , Neoplasias Colorretais/prevenção & controle , Método Duplo-Cego , Ácido Fólico/sangue , Humanos , Metilenotetra-Hidrofolato Redutase (NADPH2)/genética , Pessoa de Meia-Idade , Recidiva Local de Neoplasia/enzimologia , Recidiva Local de Neoplasia/prevenção & controle , Inquéritos e Questionários , Adulto JovemRESUMO
Accumulating evidence suggests that grape seed and wine polyphenol extracts possess a diverse array of actions and may be beneficial in the prevention of inflammatory-mediated disease such as cardiovascular disease and cancer. This study aimed to determine whether the reported pleiotropic effects of several polyphenolic extracts from grape seed products or red wine would also include inhibition of cholesterol uptake and cell proliferation, and inhibit a known specific target of the inflammatory process, that is, 5-lipoxygenase (5-LOX). Incubation of HT29, Caco2, HepG2, or HuTu80 cells in a medium containing [(3)H]cholesterol in the presence of a grape seed extract (GSE) or red wine polyphenolic compounds (RWPCs) inhibited [(3)H]cholesterol uptake by up to 66% (which appeared maximal). The estimated IC(50) values were 60 and 83 microg/mL for RWPC and GSE, respectively. Similar cholesterol uptake inhibitory effects were observed using the fluorescent cholesterol analogue NBD cholesterol. The inhibition of cholesterol uptake was independent of the sample's (GSE and RWPC) potent antioxidative capacity. Red wine polyphenolic compound and GSE dose dependently inhibited HT29 colon adenocarcinoma cell proliferation, which was accompanied by an increase in apoptosis. In addition, RWPC and GSE inhibited 5-LOX activity with the IC(50) values being 35 and 13 microg/mL, respectively. Two of 3 other GSEs tested also significantly inhibited 5-LOX activity. Inhibition of cholesterol uptake and proinflammatory 5-LOX activity may be beneficial in preventing the development of chronic degenerative diseases such as cardiovascular disease and cancer.
Assuntos
Araquidonato 5-Lipoxigenase/metabolismo , Colesterol/metabolismo , Flavonoides/farmacologia , Fenóis/farmacologia , Extratos Vegetais/farmacologia , Sementes , Vitis , Vinho , Adenocarcinoma/enzimologia , Adenocarcinoma/metabolismo , Adenoma/enzimologia , Adenoma/metabolismo , Anticarcinógenos/farmacologia , Anticarcinógenos/uso terapêutico , Carcinoma Hepatocelular/enzimologia , Carcinoma Hepatocelular/metabolismo , Doenças Cardiovasculares/prevenção & controle , Divisão Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Neoplasias do Colo/enzimologia , Neoplasias do Colo/metabolismo , Neoplasias Duodenais/enzimologia , Neoplasias Duodenais/metabolismo , Flavonoides/uso terapêutico , Humanos , Inibidores de Lipoxigenase , Neoplasias Hepáticas/enzimologia , Neoplasias Hepáticas/metabolismo , Fenóis/uso terapêutico , Extratos Vegetais/uso terapêutico , PolifenóisRESUMO
Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme in folate metabolism. We assessed the association between two common MTHFR variants, 677C>T and 1298A>C, and adenoma recurrence in the context of a randomized double- blind clinical trial of aspirin use and folate supplementation. We used generalized linear regression to estimate risk ratios and 95% confidence intervals (95% CI) for recurrence, adjusting for age, sex, clinical center, follow-up time, and treatment status. Neither MTHFR polymorphism was associated with overall or advanced adenoma recurrence. Compared with those with two wild-type alleles, the relative risk for advanced adenoma was 0.75 (95% CI, 0.36-1.55) for the MTHFR 677 TT genotype and 1.16 (95% CI, 0.58-2.33) for the MTHFR 1298 CC genotype. The effect of folate supplementation on recurrence risk did not differ by genotype. Our findings indicate that the MTHFR genotype does not change adenoma risk in a manner similar to its effect on colorectal cancer, and does not modify the effect of folate supplementation on metachronous adenoma risk.
Assuntos
Adenoma/genética , Neoplasias Colorretais/genética , Metilenotetra-Hidrofolato Redutase (NADPH2)/genética , Recidiva Local de Neoplasia/genética , Adenoma/enzimologia , Adenoma/prevenção & controle , Alelos , Aspirina/uso terapêutico , Distribuição de Qui-Quadrado , Neoplasias Colorretais/enzimologia , Neoplasias Colorretais/prevenção & controle , Método Duplo-Cego , Feminino , Ácido Fólico/uso terapêutico , Genótipo , Humanos , Modelos Lineares , Masculino , Pessoa de Meia-Idade , Recidiva Local de Neoplasia/enzimologia , Recidiva Local de Neoplasia/prevenção & controle , Placebos , Polimorfismo GenéticoRESUMO
BACKGROUND: Epidemiologic and animal studies provide evidence for a chemopreventive effect of selenium on colorectal cancer, which may be mediated by the antioxidative and anti-inflammatory properties of selenoenzymes. We therefore investigated whether genetic variants in selenoenzymes abundantly expressed in the colon are associated with advanced colorectal adenoma, a cancer precursor. METHODS: Cases with a left-sided advanced adenoma (n = 772) and matched controls (n = 777) screen negative for polyps based on sigmoidoscopy examination were randomly selected from participants in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. The underlying genetic variation was determined by resequencing. We genotyped 44 tagging single nucleotide polymorphisms (SNP) in six genes [glutathione peroxidase 1-4 (GPX1, GPX2, GPX3, and GPX4), selenoprotein P (SEPP1), and thioredoxin reductase 1 (TXNRD1)] to efficiently predict common variation across these genes. RESULTS: Four variants in SEPP1 were significantly associated with advanced adenoma risk. A rare variant in the 5' region of SEPP1 (-4166C>G) was present in nine cases but in none of the controls (exact P = 0.002). Three SNPs located in the 3' region of SEPP1, which is overlapping with the promoter region of an antisense transcript, were significantly associated with adenoma risk: homozygotes at two SEPP1 loci (31,174 bp 3' of STP A>G and 43,881 bp 3' of STP G>A) were associated with increased adenoma risk [odds ratio (OR), 1.48; 95% confidence interval (95% CI), 1.00-2.19 and OR, 1.53; 95% CI, 1.05-2.22, respectively] and the variant SEPP1 44,321 bp 3' of STP C>T was associated with a reduced adenoma risk (CT versus CC OR, 0.85; 95% CI, 0.63-1.15). Furthermore, we observed a significant 80% reduction for advanced colorectal adenoma risk for carriers of the variant allele at TXNRD1 IVS1-181C>G (OR, 0.20; 95% CI, 0.07-0.55; P trend = 0.004). Consistent with the individual SNP results, we observed a significant overall association with adenoma risk for SEPP1 and TXNRD1 (global P = 0.02 and 0.008, respectively) but not for the four GPX genes. CONCLUSION: Our study suggests that genetic variants at or near the SEPP1 and TXNRD1 loci may be associated with advanced colorectal adenoma. As this is the first study to comprehensively investigate this hypothesis, confirmation in independent study populations is needed.
Assuntos
Adenoma/enzimologia , Adenoma/genética , Neoplasias Colorretais/enzimologia , Neoplasias Colorretais/genética , Variação Genética , Selênio , Idoso , Estudos de Casos e Controles , Genótipo , Glutationa Peroxidase/genética , Haplótipos , Humanos , Modelos Logísticos , Pessoa de Meia-Idade , Fosfolipídeo Hidroperóxido Glutationa Peroxidase , Polimorfismo de Nucleotídeo Único , Risco , Selenoproteína P/genética , Inquéritos e Questionários , Tiorredoxina Redutase 1/genética , Glutationa Peroxidase GPX1RESUMO
One of the liabilities of the Apc(Min) mouse as a model for colon cancer is its lack of a robust tumor response in the large bowel. In our protocol, we treated the Apc(Min) mouse with azoxymethane, a colon-selective carcinogen. This protocol induced a 4-fold increase in the number of colon tumors. We utilized this protocol to investigate the possible mechanisms of inhibition of colorectal carcinogenesis by green tea. Mice received water or a 0.6% (w/v) solution of green tea as the only source of beverage. Green tea treatment commenced at the eighth week of age and lasted for either 4 or 8 weeks. Green tea significantly inhibited the formation of new adenomas, but was ineffective against larger tumors. Mechanistically, we investigated the effects of green tea on the expression of biomarkers involved in colon carcinogenesis. Western blotting analysis showed that green tea decreased the total levels of the early carcinogenesis biomarker beta-catenin and its downstream target cyclin D1. In contrast, the expression of COX-2 was not altered. Immunohistochemical analysis showed that green tea inhibited the formation of adenomas overexpressing beta-catenin and cyclin D1, but did not reduce the number of COX-2-expressing adenomas. Our results suggest that green tea specifically targets initial stages of colon carcinogenesis; the time of administration of green tea is pivotal for effective chemoprevention. Beverage levels of green tea do not inhibit the progress of any large adenomas or adenocarcinomas existing prior to the tea administration.
Assuntos
Adenoma/patologia , Adenoma/prevenção & controle , Camellia sinensis , Neoplasias do Colo/patologia , Neoplasias do Colo/prevenção & controle , Genes APC , Camundongos Knockout , Extratos Vegetais/uso terapêutico , Adenoma/enzimologia , Adenoma/genética , Animais , Azoximetano/farmacologia , Carcinógenos , Neoplasias do Colo/induzido quimicamente , Neoplasias do Colo/enzimologia , Neoplasias do Colo/genética , Ciclo-Oxigenase 2/genética , Feminino , Regulação Neoplásica da Expressão Gênica , Masculino , Camundongos , Camundongos Endogâmicos C57BLRESUMO
The transmembrane protein-tyrosine phosphatase (PTP) DEP-1 (density-enhanced phosphatase) is a candidate tumor suppressor in the colon epithelium. We have explored the function of DEP-1 in colon epithelial cells by inducible re-expression in a DEP-1-deficient human colon cancer cell line. Density-enhanced phosphatase-1 re-expression led to profound inhibition of cell proliferation and cell migration, and was associated with cytoskeletal rearrangements. These effects were dependent on the PTP activity of DEP-1 as they were not observed with cells expressing the catalytically inactive DEP-1 C1239S variant. shRNA-mediated suppression of DEP-1 in a colon epithelial cell line with high endogenous DEP-1 levels enhanced proliferation, further supporting the antiproliferative function of DEP-1. Nutrients, which are considered to be chemoprotective with respect to colon cancer development, including butyrate, green tea and apple polyphenols, had the capacity to elevate transcription of endogenous DEP-1 mRNA and expression of DEP-1 protein. Upregulation of DEP-1 expression, and in turn inhibition of cell growth and migration may present a previously unrecognized mechanism of chemoprevention by nutrients.
Assuntos
Adenocarcinoma/patologia , Adenoma/patologia , Anticarcinógenos/farmacologia , Colo/citologia , Neoplasias do Colo/patologia , Células Epiteliais/efeitos dos fármacos , Proteínas de Neoplasias/fisiologia , Proteínas Tirosina Fosfatases/fisiologia , Adenocarcinoma/enzimologia , Adenoma/enzimologia , Butiratos/farmacologia , Divisão Celular/efeitos dos fármacos , Linhagem Celular Tumoral/citologia , Linhagem Celular Tumoral/efeitos dos fármacos , Linhagem Celular Tumoral/enzimologia , Movimento Celular/efeitos dos fármacos , Células Cultivadas/citologia , Células Cultivadas/efeitos dos fármacos , Células Cultivadas/enzimologia , Quimiocina CXCL12 , Quimiocinas CXC/farmacologia , Colo/enzimologia , Neoplasias do Colo/enzimologia , Regulação para Baixo , Indução Enzimática/efeitos dos fármacos , Células Epiteliais/citologia , Células Epiteliais/enzimologia , Flavonoides/farmacologia , Humanos , Lisofosfolipídeos/farmacologia , Malus/química , Proteínas de Neoplasias/biossíntese , Proteínas de Neoplasias/genética , Fenóis/farmacologia , Extratos Vegetais/farmacologia , Polifenóis , Proteína Fosfatase 1 , Proteínas Tirosina Fosfatases/biossíntese , Proteínas Tirosina Fosfatases/genética , Interferência de RNA , RNA Mensageiro/biossíntese , RNA Mensageiro/genética , RNA Neoplásico/biossíntese , RNA Neoplásico/genética , RNA Interferente Pequeno/farmacologia , Proteínas Tirosina Fosfatases Classe 3 Semelhantes a Receptores , Proteínas Recombinantes de Fusão/biossíntese , Proteínas Recombinantes de Fusão/genética , Chá/química , Transcrição Gênica/efeitos dos fármacos , Transfecção , Regulação para Cima/efeitos dos fármacosRESUMO
BACKGROUND: Signaling networks promoting cell growth and proliferation are frequently deregulated in cancer. Tumors often are highly dependent on such signaling pathways and may become hypersensitive to downregulation of key components within these signaling cascades. The classical mitogenic cascade transmits stimuli from growth factor receptors via Ras, Raf, MEK and ERK to the cell nucleus and provides attractive molecular targets for cancer treatment. For example, Ras and Raf kinase inhibitors are already in a number of ongoing phase II and phase III clinical trials. In this study the effect of the Raf kinase inhibitor BAY 43-9006 and of the MEK inhibitor CI-1040 (PD184352) on a Raf dependent lung tumor mouse model was analyzed in detail. METHODS: We have generated a lung cancer mouse model by targeting constitutively active C-Raf kinase to the lung. These mice develop adenomas within 4 months of life. At this time-point they received daily intraperitoneal injections of either 100 mg/kg BAY 43-9006 or CI-1040 for additional 21 days. Thereafter, lungs were isolated and the following parameters were analyzed using histology and immunohistochemistry: overall lung structure, frequency of adenoma foci, proliferation rate, ERK activity, caspase-3 activation, and lung differentiation. RESULTS: Both inhibitors were equally effective in vitro using a sensitive Raf/MEK/ERK ELISA. In vivo, the systemic administration of the MEK inhibitor CI-1040 reduced adenoma formation to a third and significantly restored lung structure. The proliferation rate of lung cells of mice treated with CL-1040 was decreased without any obvious effects on differentiation of pneumocytes. In contrast, the Raf inhibitor BAY 43-9006 did not influence adenoma formation in vivo. CONCLUSION: The MEK inhibitor CI-1040 may be used for the treatment of Ras and/or Raf-dependent human malignancies.
Assuntos
Adenoma/tratamento farmacológico , Benzamidas/farmacologia , Neoplasias Pulmonares/tratamento farmacológico , Proteínas Proto-Oncogênicas c-raf/antagonistas & inibidores , Adenoma/enzimologia , Adenoma/patologia , Animais , Apoptose/efeitos dos fármacos , Benzenossulfonatos/farmacologia , Diferenciação Celular/efeitos dos fármacos , Divisão Celular/efeitos dos fármacos , Neoplasias Pulmonares/enzimologia , Neoplasias Pulmonares/patologia , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Camundongos , Camundongos Transgênicos , Proteínas Quinases Ativadas por Mitógeno/antagonistas & inibidores , Niacinamida/análogos & derivados , Compostos de Fenilureia , Proteínas Proto-Oncogênicas c-raf/fisiologia , Piridinas/farmacologia , SorafenibeRESUMO
Selenoproteins such as glutathione peroxidases (GPx), thioredoxin reductases (TrxR), and selenoprotein P (SePP) contain molecular selenium in form of selenocysteines within their active center. They are involved in the defense of reactive oxygen species, which otherwise may cause DNA damage and alterations of protein function. Selenium intake has been linked to colon carcinogenesis in epidemiological and interventional studies. In a double-blinded, placebo-controlled trial, we demonstrate that carriers of colon adenomas present with low basal serum levels of selenium and plasma glutathione peroxidase (pGPx) activity before treatment, but both parameters can be normalized by interventional selenium supplementation. GPx activity in colon mucosa was enhanced in the verum group, albeit this had only borderline significance. No change of activity was observed for mucosal TrxR activity on selenium supplementation. In summary, our results confirm the existence of low selenium levels in patients prone to colon adenomas and show that by selenium supplementation this can be normalized. If prospective trials confirm that selenium supplementation reduces colon cancer incidence rates, it may be concluded that selenium supplementation should be recommended for patients at risk.
Assuntos
Adenoma/enzimologia , Colo/enzimologia , Neoplasias do Colo/enzimologia , Glutationa Peroxidase/sangue , Selênio/administração & dosagem , Selênio/sangue , Neoplasias do Colo/prevenção & controle , Suplementos Nutricionais , Método Duplo-Cego , Humanos , Mucosa Intestinal/enzimologia , Placebos , Selenito de Sódio/administração & dosagem , Tiorredoxina Dissulfeto Redutase/metabolismoRESUMO
The G protein-coupled receptor (GPCR) activation has been demonstrated to affect the ERK1/2 cascade in different cell lines. We investigated the effects of hypothalamic neuropeptides acting via GPCR on this pathway in GH-secreting (GH-oma) and nonsecreting (NFPA) pituitary adenomas. GHRH increased ERK1/2 activity (236 +/- 80%) in both gsp- and gsp+ GH-omas, this effect being almost completely abolished by protein kinase C (PKC) blockade. Both GnRH and pituitary adenylate-activating peptide caused a similar PKC-dependent activation of ERK1/2 in most NFPA. Increasing cAMP by forskolin caused a protein kinase A-dependent increase of ERK activity (287 +/- 37%) in GH-omas and had no effect in NFPA. ERK cascade blockade in GH-omas did not affect basal and GHRH-stimulated GH release, whereas it totally prevented the 3-fold increase in cyclin D1 protein expression induced by GHRH. In conclusion, this study demonstrated that in pituitary adenomas the activation of GPCR by neurohormones caused a PKC-dependent activation of ERK1/2 cascade that, at least in GH-omas, resulted to be involved in cyclin D1 induction by GHRH. Moreover, a stimulatory effect of the protein kinase A-dependent pathway on ERK1/2 cascade occurred selectively in GH-omas, probably contributing to the mitogenic potential of the cAMP pathway in this cell type.
Assuntos
Adenoma/enzimologia , Hipotálamo/química , Proteína Quinase 1 Ativada por Mitógeno/metabolismo , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Neuropeptídeos/farmacologia , Neoplasias Hipofisárias/enzimologia , Adenoma/metabolismo , Colforsina/farmacologia , AMP Cíclico/metabolismo , Proteínas Quinases Dependentes de AMP Cíclico/farmacologia , Ciclina D1/análise , Inibidores Enzimáticos/farmacologia , Hormônio do Crescimento/metabolismo , Hormônio Liberador de Hormônio do Crescimento/farmacologia , Proteínas Heterotriméricas de Ligação ao GTP/fisiologia , Humanos , MAP Quinase Quinase 1 , MAP Quinase Quinase 2 , Proteína Quinase 3 Ativada por Mitógeno , Quinases de Proteína Quinase Ativadas por Mitógeno/antagonistas & inibidores , Fosforilação , Neoplasias Hipofisárias/metabolismo , Proteína Quinase C/antagonistas & inibidores , Proteínas Serina-Treonina Quinases/antagonistas & inibidores , Proteínas Tirosina Quinases/antagonistas & inibidores , Células Tumorais CultivadasRESUMO
AIM: To investigate the chemo preventive effects of vanadium on rat colorectal carcinogenesis induced by 1,2-dimethylhydrazine (DMH). METHODS: Male Sprague-Dawley Rats were randomly divided into four groups. Rats in Group A received saline vehicle alone for 16 weeks. Rats in Group B were given DMH injection once a week intraperitoneally for 16 weeks; rats in Group C, with the same DMH treatment as in the Group B, but received 0.5-ppm vanadium in the form ammonium monovanadate ad libitum in drinking water. Rats in the Group D received vanadium alone as in the Group C without DMH injection. RESULTS: Aberrant crypt foci (ACF) were formed in animals in DMH-treated groups at the end of week 16. Compared to DMH group, vanadium treated group had less ACF (P<0.001). At the end of week 32, all rats in DMH group developed large intestinal tumors. Rats treated with vanadium contained significantly few colonic adenomas and carcinomas (P<0.05) compared to rats administered DMH only. In addition, a significant reduction (P<0.05) in colon tumor burden (sum of tumor sizes per animal) was also evident in animals of Group C when compared to those in rats of carcinogen control Group B. The results also showed that vanadium significantly lowered PCNA index in ACF (P<0.005). Furthermore, vanadium supplementation also elevated liver GST and Cyt P-450 activities (P<0.001 and P<0.02, respectively). CONCLUSION: Vanadium in the form of ammonium monovanadate supplemented in drinking water ad libitum has been found to be highly effective in reducing tumor incidence and preneoplastic foci on DMH-induced colorectal carcinogenesis. These findings suggest that vanadium administration can suppress colon carcinogenesis in rats.
Assuntos
Neoplasias do Colo/prevenção & controle , Lesões Pré-Cancerosas/prevenção & controle , Vanadatos/farmacologia , 1,2-Dimetilidrazina/toxicidade , Adenoma/induzido quimicamente , Adenoma/enzimologia , Adenoma/patologia , Adenoma/prevenção & controle , Animais , Carcinógenos/toxicidade , Carcinoma/induzido quimicamente , Carcinoma/enzimologia , Carcinoma/patologia , Carcinoma/prevenção & controle , Colo/efeitos dos fármacos , Colo/enzimologia , Colo/patologia , Neoplasias do Colo/induzido quimicamente , Neoplasias do Colo/enzimologia , Neoplasias do Colo/patologia , Sistema Enzimático do Citocromo P-450/metabolismo , Glutationa Transferase/metabolismo , Masculino , Lesões Pré-Cancerosas/induzido quimicamente , Lesões Pré-Cancerosas/enzimologia , Lesões Pré-Cancerosas/patologia , Antígeno Nuclear de Célula em Proliferação/metabolismo , Ratos , Ratos Sprague-DawleyRESUMO
A 30-year-old male was referred for the rapid development of gynecomastia, and dramatic hyperestrogenemia was assessed: plasma estrone, estradiol but also cortisol were not suppressed by high-dose dexamethasone, while gonadotropin pulsatility was completely abolished. A 60-mm right adrenal tumor was evidenced on computed tomography-scan, and the patient underwent adrenalectomy. The tumor was found to express a moderate increase in aromatase activity compared with adjacent non-neoplastic adrenal tissue. Quantitative RT-PCR also showed a weak and non-significant increase in total aromatase mRNA in the tumor compared with normal adrenal tissue. Aromatase transcripts were mainly promoter PII-derived, but different patterns of aromatase minor transcripts were found: promoter I.3- and I.6-derived transcripts were identified in the tumor, while only promoter I.4-derived transcripts were found in normal adrenal. This case report demonstrates that a sharp aromatase overexpression is not a prerequisite for clinical and biochemical hyperestrogenism, and further characterizes the aromatase promoter utilization in this feminizing adrenocortical tumor and in the normal adrenal cortex.
Assuntos
Adenoma/complicações , Neoplasias do Córtex Suprarrenal/complicações , Aromatase/genética , Estrogênios/sangue , Feminização/etiologia , Expressão Gênica , 17-alfa-Hidroxiprogesterona/análise , Adenoma/enzimologia , Adenoma/cirurgia , Córtex Suprarrenal/química , Neoplasias do Córtex Suprarrenal/enzimologia , Neoplasias do Córtex Suprarrenal/cirurgia , Adrenalectomia , Adulto , Androstenodiona/análise , Aromatase/metabolismo , Estradiol/análise , Estrona/análise , Ginecomastia/etiologia , Humanos , Masculino , RNA Mensageiro/análise , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Testosterona/análiseRESUMO
The aim of the present work was to clarify whether the activities of selenoenzymes can serve as markers for different tumors or goiters, as classified by histological criteria. The following parameters were determined: 1) selenium content of plasma (Se), 2) activities of the selenoenzymes: plasma glutathione peroxidase (plGSHPx), cytosolic glutathione peroxidase (cGSHPx), type I and type II iodothyronine deiodinases (ID-I, ID-II), thioredoxin reductase (THRR) in human thyroid tissues. The material came from follicular neoplasm, papillary carcinoma, struma nodosa, struma lymphomatosis Hashimoto, other thyroid surgery specimens, and normal tissues. There was no difference in Se nor in plGSHPx between patients and healthy volunteers. No significant differences were found for any parameter in thyroid carcinoma versus normal or goitrous thyroid tissue. In the whole group of thyroid surgery specimens the statistically significant correlations were found between ID-I and ID-II and between THRR and selenoperoxidases. Principal components analysis confirmed the above correlation and moreover revealed correlation between Se and plGSHPx, but did not detect any clear distinction between patients with the different diagnoses.
Assuntos
Proteínas/análise , Glândula Tireoide/química , Glândula Tireoide/enzimologia , Neoplasias da Glândula Tireoide/química , Neoplasias da Glândula Tireoide/enzimologia , Adenoma/química , Adenoma/enzimologia , Adulto , Idoso , Carcinoma Papilar/química , Carcinoma Papilar/enzimologia , Glutationa Peroxidase/sangue , Glutationa Peroxidase/metabolismo , Humanos , Iodeto Peroxidase/metabolismo , Pessoa de Meia-Idade , Valores de Referência , Selênio/sangue , Selenoproteínas , Tiorredoxina Dissulfeto Redutase/metabolismo , Tireoidite Autoimune/enzimologia , Tireoidite Autoimune/metabolismoRESUMO
It is generally accepted that protein kinase C-alpha (PKC-alpha) is an important enzyme in the cellular regulation of growth and differentiation by phosphorylating proteins. Recent studies have described a point mutation of PKC-alpha (position 908 of the genetic sequence, codon GAC becoming GGC) in invasive human pituitary tumours which leads to an exchange of amino acids in the protein. We investigated 11 human pituitary tumours to evaluate the data obtained previously. cDNA was subcloned and up to ten individual clones were sequenced from each tumour, resulting in 85 clones analyzed in total. All of the pituitary adenomas showed a normal wild-type sequence of PKC-alpha DNA. Even if the tumour was 'invasive' (infiltration of the dura mater) no mutation at position 908 of the sequence was found. Moreover, using Western blot analyses we did not observe any differences in PKC-alpha protein expression in invasive as compared with noninvasive pituitary adenomas. Until now we have been unable to confirm the data of other investigators, suggesting that mutated PKC-alpha is an inconsistent feature of invasive pituitary tumours.
Assuntos
Adenoma/enzimologia , Isoenzimas/genética , Neoplasias Hipofisárias/enzimologia , Proteína Quinase C/genética , Adenoma/genética , Adenoma/patologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Western Blotting , DNA Complementar/análise , Humanos , Pessoa de Meia-Idade , Invasividade Neoplásica , Neoplasias Hipofisárias/genética , Neoplasias Hipofisárias/patologia , Mutação Puntual , Reação em Cadeia da Polimerase , Proteína Quinase C-alfaRESUMO
BACKGROUND & AIMS: We recently showed that dietary supplementation with an analogue of 1alpha,25-dihydroxy-vitamin D3, 1alpha,25-dihydroxy-16-ene-23-yne-26,27 F6-vitamin D3 (RO24-5531), reduced the incidence of colonic tumors in rats treated with azoxymethane (AOM). The aim of this study was to determine whether alterations in specific isoforms of protein kinase C (PKC) are involved in this phenomenon. METHODS: Protein abundance and subcellular distribution of several PKC isoforms were examined and compared in AOM-induced tumors of rats fed control and RO24-5531-supplemented diets. RESULTS: In both AOM-induced colonic adenomas and carcinomas, a significant down-regulation of PKC-alpha, -delta, and -zeta and an up-regulation of PKC-beta11 were found compared with control colonocytes. Dietary RO24-5531 preserved the expression of PKC-zeta and increased the abundance of PKC-epsilon in carcinogen-induced adenomas. CONCLUSIONS: Because identical changes in specific isoforms of PKC were found in AOM-induced adenomas and carcinomas, these alterations may be involved in the early stage(s) of colonic malignant transformation. Moreover, the ability of RO24-5531 to block the changes in PKC-zeta induced by AOM, as well as to up-regulate PKC-epsilon, may underlie its ability to prevent adenomas from progressing to carcinomas.
Assuntos
Anticarcinógenos/farmacologia , Calcitriol/análogos & derivados , Neoplasias do Colo/prevenção & controle , Proteína Quinase C/metabolismo , Adenocarcinoma/enzimologia , Adenocarcinoma/patologia , Adenocarcinoma/prevenção & controle , Adenoma/enzimologia , Adenoma/patologia , Adenoma/prevenção & controle , Animais , Azoximetano , Calcitriol/farmacologia , Quimioprevenção , Colo/efeitos dos fármacos , Colo/enzimologia , Colo/patologia , Neoplasias do Colo/enzimologia , Neoplasias do Colo/patologia , Regulação para Baixo , Isoenzimas/metabolismo , Masculino , Ratos , Ratos Endogâmicos F344 , Regulação para CimaRESUMO
An altered protein expression of Ca(2+)-dependent protein kinase C (PKC) isoforms and a point mutation in the PKC alpha cDNA (position 908 of the nucleotide sequence, position 294 of the amino acid sequence, substitution of an aspartic acid by a glycine) have been previously described in a subpopulation of human pituitary tumors. In this work, we screened 16 thyroid tissue samples (four follicular adenomas, five colloid adenomas, three papillary carcinomas, one follicular carcinoma and three normal tissues adjacent to the tumors) for the presence of the PKC alpha point mutation and for PKC alpha, beta 1, beta 2, epsilon and delta protein expression. Screening for the presence of the PKC alpha mutant was performed by a subcloning technic. The polymerase chain reaction products were generated using reverse-transcribed cDNAs, subcloned and sequenced (10 clones were routinely sequenced). The PKC alpha point mutation at position 908 of the cDNA sequence was found in four out of the nine adenomas and in the follicular carcinoma. It was neither detected in the papillary carcinomas nor in the adjacent normal tissues (one was the adjacent normal tissue of the follicular carcinoma; in this sample, genomic DNA and cDNA were used to look for the presence of the mutant), demonstrating the somatic nature of this mutant. Western blot analysis of PKC isoforms showed that the expression of all isoforms was higher in the thyroid neoplasms as compared with their adjacent normal tissue (n = 3). It was also higher in the samples containing the PKC mutant (two follicular adenomas, two colloid adenomas and the follicular carcinoma) as compared with the tumors where it was not detected (three papillary carcinomas and five adenomas). Samples could be ordered according to their increasing PKC expression as follows: normal adjacent tissue < follicular adenomas without PKC alpha mutant < or = papillary carcinoma < follicular adenomas with PKC mutant < follicular carcinoma with PKC mutant. In conclusion, the discovery of the PKC alpha mutant in thyroid neoplasms demonstrates that this mutant is not particular to human pituitary tumors where it was originally detected. It is a somatic mutation and its presence is concomitant with high levels of all of the PKC isoforms analysed. The presence of the PKC mutant in thyroid neoplasms raises the question of its importance in thyroid tumorigenesis.
Assuntos
Isoenzimas/genética , Mutação Puntual , Proteína Quinase C/genética , Neoplasias da Glândula Tireoide/enzimologia , Neoplasias da Glândula Tireoide/genética , Adenocarcinoma Folicular/enzimologia , Adenocarcinoma Folicular/genética , Adenocarcinoma Mucinoso/enzimologia , Adenocarcinoma Mucinoso/genética , Adenoma/enzimologia , Adenoma/genética , Sequência de Bases , Carcinoma/enzimologia , Carcinoma/genética , Carcinoma Papilar/enzimologia , Carcinoma Papilar/genética , Clonagem Molecular , Primers do DNA , DNA Complementar , DNA de Neoplasias/análise , DNA de Neoplasias/genética , Humanos , Dados de Sequência Molecular , Reação em Cadeia da PolimeraseRESUMO
Neoplastic conversion induced in rat liver by diethylnitrosamine (DEN) was quantified by measuring preneoplastic and neoplastic lesions over a 34 week period in the beginning of which the carcinogen was given at three dose levels and two dose rates for the first 10 weeks, after which animals were maintained for 24 weeks with either no further exposure or were fed phenobarbital (PB) to promote neoplastic development of cells converted by DEN. DEN was injected s.c. in male F344 rats at weekly or biweekly intervals for total doses of 1, 2 or 4 mmol/kg body wt and then the rats were maintained on basal diet alone or diet containing 0.05% PB. At the end of exposure, DEN had produced a dose-related decrease in centrilobular glutamine synthetase-expressing (GS+) hepatocytes which is indicative of mild cytotoxicity. All doses induced foci that were gamma-glutamyltranspeptidase-positive and iron storage-deficient. The multiplicity of foci in the middle dose exceeded that in the low dose by about a factor of two and, in the high dose, was > 10-fold greater. A few GS+ foci were found in the high dose group only. At 34 weeks, neoplasms were present in the middle and high dose groups. Administration of PB after DEN increased the multiplicity of foci in all dose groups, most substantially in the low dose group. The effect of PB on liver neoplasm yield was marginal in the low non-carcinogenic dose, whereas it enhanced the multiplicity in the weakly carcinogenic middle dose by approximately 10-fold. Four principal findings were made: (i) even at the low doses used, a mild cytotoxic response not evidenced by morphological changes in conventional histopathology was manifested in the GS+ centrilobular subpopulation of hepatocytes; (ii) the dose response over a 4-fold dose range of DEN alone and when followed by PB was non-linear; (iii) the precursor role of foci in the evolution of liver neoplasms was evident and was most conspicuous in the case of GS+ foci; and (iv) a high level of foci induction was required for the evolution of neoplasms, even with PB promotion. The finding of non-linearity with increasing doses of DEN raises questions about the assumption that effects of carcinogens at high doses can be quantitatively extrapolated to low doses.