Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The aim of this investigation was to determine the impact of dietary energy restriction (ER) with control (C) and high-fat (HF) diets on two-stage skin carcinogenesis and on the expression of specific isoforms of protein kinase C (PKC). Skin carcinogenesis was initiated on SENCAR mice with 10 nmol of 7,12-dimethylbenz[a]anthracene (DMBA) in 0.2 mL of acetone and then promoted with twice weekly treatments of 3.2 nmol of 12-O-tetradecanoylphorbol-13-acetate (TPA) in 0.2 mL of acetone for 18 wk. The experimental diets fed during TPA treatment and for 10 wk after the last TPA treatment were formulated with C (10% calories from fat) and HF (42% calories from fat) levels for freely fed groups. These diets were restricted by 20% (20% ER/C and 20% ER/HF) and by 40% (40% ER/C and 40% ER/HF). Papilloma incidence was reduced in the mice fed the 20% ER/C, 40% ER/C, and 40% ER/HF diets in comparison with the C, HF, and 20% ER/HF groups. Carcinoma incidence was also reduced in these groups. PKC alpha and zeta were assessed by western blot analysis in the epidermises of mice pre-fed the six diets for 8-10 wk (without DMBA or TPA treatment). PKC alpha was reduced in the particulate fraction by 32-44% in the 20% ER/C, 40% ER/C, and 40% ER/HF groups (P < 0.005). PKC zeta was reduced by 24-31% in the cytosol of mice fed the 20% ER/C diet and in the particulate fraction of mice fed the 40% ER/C diet (P < 0.05). The HF diet was able to block the inhibition of skin carcinogenesis and the reduction in the expression of PKC in the epidermis by 20% ER but not by 40% ER.
Mol Carcinog 1996 Jun
PMID:High-fat diet blocks the inhibition of skin carcinogenesis and reductions in protein kinase C by moderate energy restriction. 864 26

Cultured rat mammary cells express both CYP1A1 and CYP1B1 in response to polycyclic aromatic hydrocarbons (PAH) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in a cell type-specific manner. The expression of each P450 was determined functionally (regioselective PAH metabolism), as apoprotein (immunoblots) and as mRNA (Northern hybridization). The epithelial rat mammary cells (RMEC) expressed CYP1A1, however only after PAH or TCDD treatment. CYP1B1 protein was scarcely detected in these induced RMEC but was surprisingly active as a participant in 7,12-dimethylbenz[a]anthracene (DMBA) metabolism shown through selective antibody inhibition (40% of total activity). CYP1B1 was selectively expressed in the stromal fibroblast population of rat mammary cells to the exclusion of CYP1A1. In the rat mammary fibroblasts (RMF), CYP1B1 protein and associated activity were each present at low levels constitutively and were highly induced by benz[a]anthracene (BA) to a greater extent than by TCDD (12- versus 6-fold). However, BA (10 microM) and TCDD (10 nM) stimulated the 5.2-kb CYP1B1-specific mRNA equally. These increases are consistent with the involvement of the aryl hydrocarbon (Ah) receptor in the transcription of the CYP1B1 gene and with the additional stabilization of CYP1B1 protein by BA, previously observed in embryo fibroblasts. Exactly this regulation of CYP1B1-dependent activity was seen in RMEC suggesting that this arises from exceptionally active CYP1B1 in a small proportion (5%) of residual RMF. The constitutive expression and PAH inducibility of CYP1B1 and CYP1A1 proteins in RMF and RMEC, respectively, were each substantially decreased (approximately 75%) by a hormonal mixture (17 beta-estradiol (0.2 microM) progesterone (1.5 microM) cortisol (1.5 microM) and prolactin (5 micrograms/ml)). Progesterone and cortisol, added singly to RMF suppressed CYP1B1 protein expression (approximately 80%) in both untreated and BA-induced cells, while cortisol also suppressed the 5.2-kb CYP1B1 mRNA. In contrast, 17 beta-estradiol stimulated constitutive expression of CYP1B1 protein (50-75%) and mRNA level (2- to 3-fold), but did not affect CYP1B1 expression in BA-treated RMF. The expression of CYP1A1 and CYP1B1 is therefore highly cell specific even though each is regulated through the Ah receptor. Each P450 exhibits a surprisingly similar pattern of hormonal regulation even though expressed in different cell types.
Mol Cell Endocrinol 1995 Nov 30
PMID:Cytochromes CYP1A1 and CYP1B1 in the rat mammary gland: cell-specific expression and regulation by polycyclic aromatic hydrocarbons and hormones. 867 63

7,12-Dimethylbenz[a]anthracene (DMBA)-induced leukemias in Long-Evans rats consistently have an A --> T transversion at the second base of codon 61 in the N-ras gene. This mutation is also detected in the preleukemic stage. To determine when this specific N-ras mutation occurs in the early stages of leukemogenesis, we designed the mutant allele-specific amplification method, which was sensitive enough to detect one mutant cell among 10(6) normal cells. In the study reported here, N-ras mutation was found in bone-marrow cells 2 d after a single DMBA injection and thereafter throughout the preleukemic stage. These results show that DMBA induces a specific N-ras mutation soon after one DMBA injection and that this mutation is probably the first event in DMBA leukemogenesis.
Mol Carcinog 1996 Jul
PMID:Specific N-ras mutation in bone marrow within 48 H of 7,12-dimethylbenz[a]anthracene treatment in Huggins-Sugiyama rat leukemogenesis. 868 47

Treatment of female Sprague-Dawley rats with the potent mammary gland carcinogen 7,12-dimethylbenz[a]anthracene (DMBA) results in the formation of DNA adducts with dG and dA and in the induction of 6-thioguanine-resistant (TGr) lymphocyte mutants. In this study, we have examined the types of mutations induced in TGr lymphocytes from DMBA-treated rats. DNA from 263 TGr lymphocyte clones was screened for mutations in exons 2, 3, and 8 of the hprt gene by polymerase chain reaction (PCR) amplification of the exons followed by heteroduplex analysis using denaturing gradient-gel electrophoresis. Twenty-five of the clones produced heteroduplexes in exon 2, 35 produced heteroduplexes in exon 3, and 36 produced heteroduplexes in exon 8. Direct sequence analysis of the heteroduplexes revealed 96 mutations, and at least 74 of these mutations were produced independently. Eighty-five of the total mutations were simple base pair (bp) substitutions, with A --> T and G --> T transversions being the predominant types. Seven mutations were deletions, three were complex bp substitutions, and one was an insertion. The results suggest that the types of mutations produced by DMBA in rat lymphocytes are specific to the DNA adducts produced by this compound.
Environ Mol Mutagen 1996
PMID:DNA sequence analysis of hprt mutations in lymphocytes from Sprague-Dawley rats treated with 7,12-dimethylbenz[a]anthracene. 869 46

To confirm that the hamster cheek-pouch carcinogenesis model reflects development of human squamous cell carcinoma (SCC), we determined if and when p53 mutations occur in the development of SCC in this model by using immunohistochemical staining and polymerase chain reaction (PCR)-single-strand conformation polymorphism (SSCP) analysis plus direct DNA sequencing. Twenty-four hamster cheek-pouches were treated with a solution of 0.5% 7,12-dimethylbenz[a]anthracene in mineral oil three times a week for 16 wk. The malignant endophytic and exophytic tumors induced with this protocol are preceded by a sequence of premalignant lesions such as hyperplasia with or without dysplasia and carcinoma in situ, similar to the development of this cancer in humans. For this study, p53 protein accumulation was evaluated by immunostaining of various hamster cheek-pouch exophytic and endophytic SCCs as well as flat dysplastic hyperplasia and carcinomas in situ. A moderate percentage (33.3%) of exophytic lesions and most endophytic carcinomas (90%) showed positive p53 staining. In addition we also found p53-positive staining in a number of preneoplastic lesions, including areas of focal hyperplasia, dysplastic hyperplasia, and carcinomas in situ. To determine whether the alterations in p53 staining were due to p53 gene mutation, we used PCR-SSCP analysis and direct sequencing. PCR products corresponding to exons 5a, 6, 7, and 8 from 40 tumors with the highest percentage of p53-stained cells were analyzed. We detected shifted bands in 17 lesions. Direct sequencing of eight selected shifted bands revealed four mutations, including two G-->T transversions in codons 216 (tumor #1) and 252 (tumor #2) and one G-->C transversion in codon 282 (tumor #3). Tumor #4 contained a frameshift mutation in codon 251. These mutations are consistent with those reported in many human cancers. Therefore, we concluded that in the hamster cheek-pouch model, p53 protein accumulation occurs frequently and early in carcinogenesis, as it does in human SCCs, and some of these p53 alterations are due to p53 gene mutations. These findings may help us better define the mechanisms of carcinogenesis in the hamster cheek-pouch model, and p53 alterations may be an early biomarker of progression for chemoprevention studies.
Mol Carcinog 1996 Aug
PMID:p53 alterations in chemically induced hamster cheek-pouch lesions. 878 62

To determine whether p53 alterations, which are frequent in human breast cancers, are also common in rat mammary tumors, we examined 40 tumors from 24 rats treated with 7,12-dimethylbenz[a]anthracene (DMBA) and 34 tumors from 14 rats treated with N-nitroso-N-methylurea (NMU) (an N-nitroso compound). DMBA and NMU are known genotoxic mutagens. The entire coding regions of the p53 and Ha-ras genes were examined for mutations by polymerase chain reaction single-strand conformational polymorphism analysis and by direct sequencing. One of the 40 DMBA-induced mammary tumors had a p53 mutation, a single-base substitution (AGC-->GGC) at codon 307, resulting in an amino-acid change from Ser to Gly. No mutations were found in NMU-induced tumors. The incidence of Ha-ras gene mutation was 79% (27 of 34) at codon 12 in the NMU group and 23% (nine of 40) at codon 61 in the DMBA group. Thus, p53 mutation, in contrast to Ha-ras mutation, did not seem to be a prerequisite for carcinogenesis in chemically induced rat mammary tumors.
Mol Carcinog 1996 Oct
PMID:Incidence of p53 and Ha-ras gene mutations in chemically induced rat mammary carcinomas. 889 Sep 56

Loss of heterozygosity (LOH) is one of the most common genetic abnormalities in cancer. To define the role of LOH and chromosomal abnormalities at various stages of mouse mammary cancer progression, we analyzed the allelotypes and karyotypes of primary mammary tumors induced in CD2F, mice by two basic protocols, the classical multiple-dose 7,12-dimethylbenz[a]anthracene (DMBA) protocol and a novel protocol of combined medroxyprogesterone acetate (MPA) and DMBA. The advantage of the latter protocol is that its latency for tumor development is much shorter and its tumor incidence is higher than those of DMBA alone. To study more advanced stages of mammary tumor progression, we also analyzed mouse mammary tumors that had acquired autonomous growth and were transplantable into syngeneic hosts. The allelotypic studies were performed by means of microsatellite length polymorphism analysis with a minimum of two simple-sequence repeat markers per chromosome. We observed that MPA-DMBA-induced mammary adenocarcinomas, which in general arose earlier because of the growth promotion exerted by MPA, did not show any significant LOH and were essentially diploid. Tumors induced by DMBA alone, which on average took longer to develop, showed a higher frequency of allelic losses. LOH on chromosome 11 was observed in 30% of the cases. Chromosomes 4 and 8 were affected in 25% and 20% of the tumors, respectively. Interestingly, advanced stages of mammary tumor progression, represented by transplantable mammary tumors, showed a much higher level of genomic instability, specifically a very high frequency (66%) of LOH on chromosome 4. These findings indicate that chromosome 4 harbors a gene whose inactivation may play a role in the acquisition of more aggressive characteristics such as autonomous growth and transplantation ability.
Mol Carcinog 1996 Nov
PMID:Allelotypic and cytogenetic characterization of chemically induced mouse mammary tumors: high frequency of chromosome 4 loss of heterozygosity at advanced stages of progression. 894 72

To identify and compare the genetic lesions associated with tumorigenesis in rats carrying the mammary carcinoma suppressor (MCS) 1 gene, we induced mammary carcinomas in (Wistar Furth (WF) x Copenhagen (Cop))F1 rats by using either 7,12-dimethylbenz[a]anthracene (DMBA) or radiation. The tumors were screened for allelic imbalances by using polymerase chain reaction and 65 polymorphic microsatellite markers spanning the genome. No allelic imbalance was detected at the mapped location of MCS-1 on chromosome 2; however, a scan of the genome revealed random allelic imbalances in the radiation-induced tumors. In addition, non-random loss of heterozygosity (LOH) on chromosome 1 in the DMBA-induced tumors was documented. We then screened three other subsets of DMBA- and radiation-induced mammary carcinomas from (WF x Fischer (F344))F1, (Wistar Kyoto x F344)F1, and (F344 x Cop)F1 rats for imbalance on chromosomes 1 and 2. No allelic imbalance was detected in the MCS-1 region of chromosome 2 in any of the tumors screened. Nonrandom imbalance on chromosome 1 was detected but only in the DMBA-induced tumors from the (F344 x Cop)F1 rats. Thus, only Cop-derived F1 rats have mammary tumors with the chromosome 1 imbalance; however, the imbalance does not favor the Cop parental allele. We also analyzed the DMBA-induced tumors with LOH at chromosome 1 for Ha-ras codon 61 mutation and found no association. These results suggest that loss of the MCS-1 Cop allele is not required for tumor formation, that the genetic background of the F1 rat appears to influence the type of genetic lesion identified in the mammary tumors, and that there is no association between Ha-ras codon 61 mutation and chromosome 1 imbalance in our model system.
Mol Carcinog 1996 Nov
PMID:Allelic imbalance in mammary carcinomas induced by either 7,12-dimethylbenz[a]anthracene or ionizing radiation in rats carrying genes conferring differential susceptibilities to mammary carcinogenesis. 894 73

We investigated the Ha-ras and Ki-ras gene status, tumorigenicity, pathology, line derivation, and intercellular communication of 7,12-dimethylbenz[a]anthracene-initiated papilloma-, carcinoma-, and hyperplastic skin-producing cell lines to further characterize them. Six of nine tumor cell lines grown in vitro expressed both mutant and normal Ha-ras proteins, and three lines expressed only normal Ha-ras. However, when grown subcutaneously in nude mice, seven of the nine lines expressed both mutant and normal Ha-ras, one line expressed normal Ha-ras, and one line did not grow subcutaneously. One papilloma line, P2/15, appeared to have an inducible mutant Ha-ras gene, as it was expressed only in vivo. These findings suggest that mutant Ha-ras genes may be lost in only a minor population of tumor lines during growth in culture. Finally, we found that mutant Ha-ras gene expression was strongly correlated with tumorigenicity in nude mice and that intercellular communication was strongly correlated with the derivation of the lines.
Mol Carcinog 1996 Dec
PMID:Characterization of mutant HA-ras gene expression in transformed murine keratinocyte lines grown under in vitro and in vivo conditions. 898 13

7,12-Dimethylbenz[a]anthracene (DMBA), a potent carcinogen, requires metabolic activation by cytochrome P450s (P450s) to electrophilic metabolites that result in DNA modification, mutagenicity, and carcinogenicity. In this study, we used eight human forms, four rodent forms, and one rabbit form of P450 expressed from recombinant vaccinia or baculovirus vectors to define their specificity for metabolizing DMBA. Of the eight human P450s, 1A1 was the most active (specific activity = 14.7 nmol/min/nmol of P450) in total metabolism of DMBA and showed approximately 6- to 33-fold more activity than other P450s, 2B6, 2C9, and 1A2 were also capable of metabolizing DMBA (2.0-2.5 nmol/min/nmol of P450), whereas 2C8, 2E1, 3A4, and 3A5 exhibited relatively low activities. Among animal P450s, mouse 1A1 exhibited activity similar to that of human 1A1 and had 5.0- to 37-fold more activity than other rodent and rabbit P450s. In regard to enzyme regioselectivity, most human and rodent P450s predominantly formed the 8,9-diol, but human 2B6 and rat 2B1 preferentially formed the 5,6-diol. In the production of monohydroxymethyl metabolites, all the enzymes yielded more 7-hydroxymethyl-12-methylbenz[a]anthracene (7HOM12MBA) than 12-hydroxymethyl-7-methylbenz[a]anthracene (7M12HOMBA), except for human 1A1, which presented the reverse selectivity. Human liver microsomes from 10 organ donors were shown to metabolize DMBA and in most circumstances generated the metabolic profile DMBA trans-8,9-dihydrodiol > 7HOM12MBA > or = DMBA trans-5,6-dihydrodiol > or = 7,12-dihydroxymethylbenz[a]anthracene > 7M12HOMBA > DMBA trans-3,4-dihydrodiol. Thus, the combined activity of hepatic microsomal 2C9, 1A2, and 2B6 may contribute to the metabolic activation and the metabolism of DMBA in normal human liver.
Mol Carcinog 1996 Dec
PMID:Specificity of cDNA-expressed human and rodent cytochrome P450s in the oxidative metabolism of the potent carcinogen 7,12-dimethylbenz[a]anthracene. 898 18


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