Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P43146 (tumour suppressor)
 5,935 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In response to DNA damage, in particular DNA strand breaks, the proposed roles for normal tumour suppressor protein p53 are to increase the period of time available for DNA repair prior to replication, or to direct damaged cells into programmed cell-death. Since treatment of mammalian cells with (+/-)-anti-benzo[a]pyrene diolepoxide [(+/-)-anti-BPDE] --a mixture of metabolites comprising the most reactive (+)-anti-enantiomer of the full environmental carcinogen benzo[a]pyrene--has been shown to result in induction of DNA repair processes and consequently in DNA strand break formation, the aim of the present study was to investigate whether p53 accumulation is induced in (+/-)-anti-BPDE-treated phytohaemagglutinin-stimulated human peripheral blood lymphocytes (PBLs). Both immunocytochemical and immunoblot analysis indicated that treatment of PBLs with (+/-)-anti-BPDE results in p53 accumulation. Optimal accumulation was observed at 2.5 microM, while no increase of p53 levels was observed at concentrations < 2.5 microM and > 10 microM. Further, (+/-)-anti-BPDE-induced p53 accumulation in PBLs was found to be time-dependent with accumulation up to 24 h after the onset of treatment. Treatment of PBLs with 2.5 microM of (+/-)-anti-BPDE and 1 mM of 3-aminobenzamide, an inhibitor of the DNA strand break-dependent enzyme poly(ADP-ribose) polymerase, resulted in increased p53 levels, in comparison to cells treated with (+/-)-anti-BPDE alone. This combination also potentiated the frequency of (+/-)-anti-BPDE-induced micronuclei. These findings suggest that (+/-)-anti-BPDE-induced DNA strand break formation is responsible for the observed p53 accumulation. It is unlikely that poly(ADP-ribose) polymer formation is a prerequisite in the process of p53 accumulation, as triggered by DNA strand-break inducing agents like (+/-)-anti-BPDE. It is hypothesized that p53-dependent pathways may be activated in phytohaemagglutinin-stimulated human peripheral blood lymphocytes exposed ex vivo to (+/-)-anti-BPDE.
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PMID:Inhibition of poly(ADP-ribose) polymerase increases (+/-)-anti-benzo [a]pyrene diolepoxide-induced micronuclei formation and p53 accumulation in isolated human peripheral blood lymphocytes. 758 97

DNA damage may mediate birth defects caused by many drugs and environmental chemicals, therefore p53, a tumour suppressor gene that facilitates DNA repair, may be critically embryoprotective. We have studied the effects of the environmental teratogen, benzo[a]pyrene, on pregnant heterozygous p53-deficient mice. Such mice exhibited between 2- to 4-fold higher embryotoxicity and teratogenicity than normal p53-controls. Fetal resorptions reflecting in utero death were genotyped using the polymerase chain reaction and found to be increased 2.6-fold and 3.6-fold respectively with heterozygous and homozygous p53-deficient embryos. These results provide the first direct evidence that p53 may be an important teratological suppressor gene which protects the embryo from DNA-damaging chemicals and developmental oxidative stress.
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PMID:A teratologic suppressor role for p53 in benzo[a]pyrene-treated transgenic p53-deficient mice. 766 13

Mutation analysis of the tumour suppressor gene p53 in tumours induced in the peritoneal cavity of rats revealed differences in the mutational pattern with regard to the carcinogenic substances applied. In tumours induced by benzo[a]pyrene a considerable amount of p53 mutations resulting in an altered protein structure could be detected. For the development of these tumours an escape from the p53 mediated cell cycle control can be assumed. However, in tumours of the same tumour type induced by crocidolite asbestos no mutations could be observed. Since there were even no spontaneous p53 mutations detectable in this tumour group, it is obvious that in these tumours the escape from cell cycle control does not take place via inactivation of p53. Therefore, it is concluded that the molecular mechanisms of carcinogenesis and tumour development in this tumour type depend on the type of carcinogen applied.
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PMID:P53 mutations in tumours induced by intraperitoneal injection of crocidolite asbestos and benzo[a]pyrene in rats. 931 51

In this study we show that benzo[a]pyrene (B[a]P) and the cyclopenta polycyclic aromatic hydrocarbons (CP-PAH) cyclopenta[c,d]pyrene (CPP), benz[j]aceanthrylene (B[j]A) and benz[l]aceanthrylene (B[l]A) induce apoptosis in Hepa1c1c7 cells, as measured by fluorescence microscopy and flow cytometry. The compounds induced formation of the active form of caspase-3, cleavage of its intracellular substrate, poly(ADP-ribose)polymerase (PARP), and DNA fragmentation. B[j]A was found to be the most potent in inducing apoptosis, followed by B[a]P, CPP and B[l]A. All compounds increased expression of CYP1A1 with relative potencies B[j]A > B[a]P >> CPP > B[l]A, corresponding well with their relative apoptotic responses. alpha-Naphthoflavone (alphaNF), an inhibitor of CYP1A1, reduced the induced apoptosis. B[a]P and CP-PAH exposure also resulted in an accumulation of the tumour suppressor protein p53. No changes were observed in the protein levels of Bax and Bcl-2, whereas the anti-apoptotic Bcl-xl protein was down-regulated, as judged by western blot analysis. Fluorescence microscopic analysis revealed a translocation of p53 to the nucleus and of Bax to the mitochondria. Furthermore, caspase-8 was activated and Bid cleaved. Interestingly, the levels of anti-apoptotic phospho-Bad (Ser155 and Ser112) had a biphasic increase after B[a]P or CPP treatment. Whereas alphaNF markedly reduced the activation of B[a]P to reactive metabolites, as measured by covalent binding to macromolecules, it did not inhibit the up-regulation of phospho-Bad. Neither of the compounds triggered apoptosis in primary cultures of rat lung cells (Clara cells, type 2 cells and lung alveolar macrophages), possibly due to a lack of CYP1A1 induction. In conclusion, B[a]P and the CP-PAH induced apoptotic as well as anti-apoptotic signals in Hepa1c1c7 cells.
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PMID:Polycyclic aromatic hydrocarbons induce both apoptotic and anti-apoptotic signals in Hepa1c1c7 cells. 1472 87

Mutations in the p53 tumour suppressor gene lead to uncontrolled cell division and are found in over 50% of all human tumours, including 60% of lung cancers. Research published in 1996 by Denissenko and colleagues demonstrated patterned in-vitro mutagenic effects on p53 of benzo[a]pyrene, a carcinogen present in tobacco smoke. We investigated the tobacco industry's response to p53 research linking smoking to cancer. We searched online tobacco document archives, including the Legacy Tobacco Documents Library and Tobacco Documents Online, and archives maintained by tobacco companies such as Philip Morris and R J Reynolds. Documents were also obtained from the British American Tobacco Company depository in Guildford, UK. Informal correspondence was carried out with scientists, lawyers, and tobacco control experts in the USA and Europe. We found that executives and scientists at the highest levels of the tobacco industry anticipated and carefully monitored p53 research. The tobacco industry's own scientists conducted research which appeared to cast doubt on the link between smoking and p53 mutations. Researchers and a journal editor with tobacco industry ties participated in the publication of this research in a peer-reviewed journal without clear disclosure of their tobacco industry links. Tobacco industry responses to research linking smoking to carcinogenic p53 mutations mirror prior industry efforts to challenge the science linking smoking and lung cancer. The extent of tobacco industry involvement in p53 research and the potential conflict of interest discussed here demonstrate the need for consistent standards for the disclosure and evaluation of such potential conflicts in biomedical research.
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PMID:The p53 tumour suppressor gene and the tobacco industry: research, debate, and conflict of interest. 1578 Oct 91

Human colon carcinoma cells (HCT116) differing in p53 status were exposed to benzo(a)pyrene (BaP) or anti-benzo(a)pyrene-trans-7,8-dihydrodiol-9,10-epoxide (BPDE) and their gene expression responses compared by complementary DNA microarray technology. Exposure of cells to BPDE for up to 24 h resulted in gene expression profiles more distinguishable by duration of exposure than by p53 status, although a subset of genes were identified that had significantly different expression in p53 wild-type (WT) cells relative to p53-null cells. Apoptotic signalling genes were up-regulated in p53-WT cells but not in p53-null cells and, consistent with this, reduced viability and caspase activity were also p53 dependent. BPDE modulated cell cycle and histone genes in both cell lines and, in agreement with this, both cell lines accumulated in S phase. In p53-WT cells, G(2) arrest was also evident, which was associated with accumulation of CDKN1A. Regardless of p53 status, exposure to BaP for up to 48 h had subtle effects on gene transcription and had no influence on cell viability or cell cycle. Interestingly, DNA adduct formation after BaP, but not BPDE, exposure was p53 dependent with 10-fold lower levels detected in p53-null cells. Other cell lines were investigated for BaP-DNA adduct formation and in these the effect of p53 knockdown was also to reduce adduct formation. Taken together, these results give further insight into the role of p53 in the response of human cells to BaP and BPDE and suggest that loss of this tumour suppressor can influence the metabolic activation of BaP.
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PMID:Identification through microarray gene expression analysis of cellular responses to benzo(a)pyrene and its diol-epoxide that are dependent or independent of p53. 1794 61

The p53 tumour suppressor protein plays a pivotal role in the response of mammalian cells to DNA damage. In addition to its regulatory role in cell cycle progression, p53 regulates apoptosis and can therefore influence cellular survival in response to DNA damage. More recent work has revealed that p53 is also involved in the nucleotide excision repair (NER) of structurally diverse types of DNA damage. The relative influence of p53 on NER and cellular sensitivity to DNA damage was investigated in this study using cells that differ in p53 status. Two cell models were selected: 041 TR fibroblasts in which the expression of p53 is regulated by a tetracycline-inducible promoter, and WI38 primary lung fibroblasts together with their isogenic derivative VA13, in which p53 is abrogated post-translationally by SV40 transformation. Cells were exposed to the clinically and environmentally relevant DNA-damaging agents cisplatin (0-5 microM, 2 h), (+/-)-anti-benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide (0-0.5 microM, 30 min) and UV-C (0-5 J/m2), each of which induce structurally distinct types of DNA damage known to be subject to p53-dependent NER. Sensitivity of the p53-proficient and p53-deficient cells to this DNA damage was then compared at each dose of DNA-damaging agent using the clonogenic survival assay and the colorimetric MTT assay. p53-proficient cells were more sensitive than p53-deficient cells to cisplatin, (+/-)-anti-benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide and UV-C; these differences in cellular sensitivity were more apparent in the 041 TR cells (up to 3.6-, 5.8- and 1.9-fold, respectively) than the WI38/VA13 cells (up to 2.3-, 1.4- and 1.4-fold, respectively). Thus, despite the well-documented persistence of DNA damage in p53-deficient fibroblasts due to impaired NER, loss of p53 results in reduced DNA damage-mediated cytotoxicity.
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PMID:The role of p53 in DNA damage-mediated cytotoxicity overrides its ability to regulate nucleotide excision repair in human fibroblasts. 1800 26

One of the most useful tools for investigating the aetiopathology of cancer is the mutation spectrum, which comprises the type and distribution of mutations within a gene sequence. Many studies have generated mutagen-induced spectra using in vitro or in vivo model systems in an attempt to find correlations with those observed in cancer-associated genes such as the TP53 tumour suppressor gene. Consequently, meaningful similarities in the types of mutation found in induced and human spectra have been demonstrated. However, it is more difficult to draw such conclusions about the distribution or sequence context of mutations when they arise in different target sequences. We have developed an analytical approach for base substitution spectra that capture information for both sequence context and mutation type simultaneously. The resulting mutation signature is a fixed set of data points that allows comparison of multiple mutation spectra regardless of sequence. We have applied this method to a mixed set of mutation spectra observed in exons 5, 7 and 8 of TP53 from cancers of brain, breast, skin, colon, oesophagus, liver, head and neck, stomach and lung (smokers and non-smokers) and spectra induced by benzo[a]pyrene diol epoxide, ultraviolet (UV) B, UVC, simulated sunlight and hydroxyl radicals in the cII, supF and yeast p53 model systems. We demonstrate that this approach allows human cancer and mutagen-induced signatures to be grouped together according to similarity. Specifically, the analysis reveals key differences between smoking- and non-smoking-related lung cancer for TP53 mutations and the mutability of CpG sites between exons in skin cancer.
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PMID:Comparison of induced and cancer-associated mutational spectra using multivariate data analysis. 1829 83

MicroRNAs (miRNAs) are small non-coding RNA molecules that negatively control the expression of target genes post-transcriptionally. In this study, transformed human bronchial epithelial cells induced by anti-benzo[a]pyrene-7,8-diol-9,10-epoxide were characterized for miRNA involved in carcinogenesis. We found miR-22, which was highly expressed in transformed cells, concomitant with downregulation of the tumour suppressor gene PTEN protein. Using computer-generated and experimental analysis, PTEN was identified as one of the targets of miR-22. Over-expression and inhibition studies of miRNA showed decreased and increased PTEN protein, respectively, with no alteration of PTEN mRNA levels. These findings suggest that miR-22 regulates PTEN expression through translational repression. A dual-reporter assay confirmed these findings and provided evidence to suggest that miR-22 regulates PTEN expression by binding with a target site in the PTEN 3'-untranslated region. A mutated seed sequence in the PTEN binding site can abrogate the regulatory role of miR-22 on PTEN. Moreover, we found that anti-miR-22 promoted cell apoptosis, decreased colony formation and reduced the motility of malignant cells. Together, the results indicate that miR-22 functions as a micro-oncogene that can invert the functionality of PTEN. Furthermore, the binding site for miR-22 might provide insight into a potential target for gene therapy.
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PMID:miR-22 functions as a micro-oncogene in transformed human bronchial epithelial cells induced by anti-benzo[a]pyrene-7,8-diol-9,10-epoxide. 2017 Jul 24

Polycyclic aromatic hydrocarbons are ubiquitous environmental pollutants formed during incomplete combustion of organic material. For example benzo[a]pyrene (B[a]P) is a constituent and contaminant of cigarette smoke, automobile exhaust, industrial waste and even food products. B[a]P is carcinogenic to rodents and humans. B[a]P induces its own metabolism, which generates different metabolites such as the highly reactive electrophilic genotoxin and ultimal carcinogen B[a]P-7,8-dihydrodiol-9,10-epoxide (BPDE). BPDE can bind to nucleophilic macromolecules such as proteins and DNA and causes mutations. Multiple defence mechanisms have evolved to protect the cell from DNA damage. Specific signalling pathways operate to detect and repair different kinds of lesions. In case, the damage is poorly removed expansion of damaged cells can be counteracted, e.g., by the inhibition of proliferation or triggering apoptosis. Examples of damage sensors and transducers are stress-activated protein kinases (SAPKs) and the tumour suppressor protein p53. Here, we studied the role of p53 and the pro-apoptotic protein BAX in BPDE-induced cell death by using wild-type- or knock-out-human colon carcinoma cells. As reported previously, we could reconfirm a critical role of p53 in BPDE-induced apoptosis. Furthermore, induced levels of total p53 and its transcriptional target p21 declined at higher BPDE concentrations correlating with reduced rates of apoptosis. Interestingly, increased phosphorylation of p53 at serine 15 remained elevated at higher BPDE concentrations thus disconnecting p53 phosphorylation from downstream apoptosis. Hence, phosphorylation of p53 seems not only to be a more sensitive biomarker of BPDE exposure but might serve other functions unrelated to apoptosis. In addition, we identify BAX as a novel and essential factor to trigger the intrinsic pathway of apoptosis in response to BPDE. Furthermore, BPDE in parallel activates the SAPKs p38 and JNK, which are as well involved in apoptosis. Although several routes of mutual regulation of p53 and SAPK have been described, we present evidence that the SAPK pathway in response to genotoxic stress can unexpectedly operate independently of p53 and controls apoptosis by a novel mechanism possibly downstream of caspases.
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PMID:Role and interaction of p53, BAX and the stress-activated protein kinases p38 and JNK in benzo(a)pyrene-diolepoxide induced apoptosis in human colon carcinoma cells. 2198 85


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