bluuebunny/crossref_metadata_2025_split huggingface dataset:
Common target for 12‐O‐tetradecanoylphorbol‐13‐acetate and ras in the transcriptional enhancer of the growth factor—inducible JE gene
Authors: Koike Manabu , Kuroki Toshio , Nose Kiyoshi 
Published: February 2007

AbstractJE gene expression in the mouse osteoblast cell line MC3T3‐E1 is activated transiently by the tumor promoter 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA). In ras‐transformed MC3T3‐E1 cells the JE gene is constitutively expressed at a high level, whereas in their raf‐transformed counterparts it is not constitutively expressed or inducible by TPA. Using these cells, we investigated a specific sequence recognized by nuclear factors in the 5′‐upstream region of the rat JE gene. By gel‐mobility shift assays, we determined that the amount of nuclear factors that bind to the region ‐ 130 to ‐ 96 bp upstream from the cap site of the rat JE gene (JE‐1 probe) increased after TPA treatment of MC3T3‐E1 cells. However, in the ras transformants it was elevated constitutively, and in the raf transformants it was not detectable. Both unlabeled JE‐1 probe and a probe containing a TPA‐responsive element (TGACTCA) competed with the binding of these nuclear factors. Preincubation of the nuclear extracts with fos‐ or jun‐specific antibodies interfered with the binding of the factors to the JE‐1 probe. The essential sequence in the JE‐1 element for the binding of nuclear factors was found to be TTACTCA. c‐fos and c‐jun proteins synthesized in vitro could bind to the DNA fragment containing this sequence, but the binding was weaker than to the TPA‐responsive element (TGACTCA). These results suggest that the sequence TTACTCA in the JE‐1 element is a common target of TPA and ras and that protein complexes containing fos‐ and jun‐related proteins recognize the sequence.
Retinoic acid receptor and retinoid X receptor expression in retinoic acid—resistant human tumor cell lines
Authors: van der Leede Bas‐Jan M. , van den Brink Christina E. , Van der Saag Paul T. 
Published: February 2007

AbstractRetinoic acid (RA) has profound effects on cell proliferation and differentiation both in vitro and in vivo. Many human cell lines are known to be sensitive to the growth‐inhibitory action of RA. We analyzed established human solid tumor—derived cell lines for their RA sensitivity. Growth inhibition by RA in monolayer was examined by [3H]thymidine incorporation and cell proliferation. Here we report that 11 widely used human cell lines were RA resistant. The majority are carcinoma derived (A‐431, BT‐20, C‐41, ACHN, HCT116, 293, A549, and PA‐1); two are sarcoma derived (Saos‐2 and A673); and one is a melanoma cell line (A‐375). Since nuclear retinoid receptors are implicated in the biological effects of RA, we examined the expression of retinoic acid receptors (RARs) RARα, RARβ, RARγ, and the retinoid X receptors (RXRs) RXRα, RXRβ, and RXRγ in the RA‐resistant cell lines by northern blotting and by RNase protection analysis for RARβ. RARα transcripts were constitutively expressed in all cell lines. By contrast, RARβ was expressed in only seven RA‐resistant cell lines (Saos‐2, ACHN, 293, A549, A‐375, A673, and PA‐1), and its level was enhanced by RA in some cases. In most cell lines, RARγ expression was low and was not affected by RA. The RXR genes showed a very distinct expression pattern in the group of selected cell lines. In general, RXRα was the most abundantly expressed subtype, RXRβ was expressed at low levels, and RXRγ could not be detected. In none of the RA‐resistant cell lines was RXR expression modulated by RA. The results presented here indicate that the resistance of these human tumor cell lines to RA cannot be simply correlated with expression of RAR or RXR or both.
Toxicity of phorbol esters for human epithelial cells expressing a mutant ras Oncogene
Authors: Dawson Tim , Bond Jane , Eccles Neil , Wynford‐Thomas David 
Published: February 2007

AbstractPhorbol esters and related compounds provide a promising source of potential anticancer agents. The mechanism of their toxicity, however, is unclear, and interpretation has been complicated by the conflicting responses exhibited by different transformed cell lines. Previously we showed that in primary thyroid follicular cells, expression of mutant p21ras conferred a striking sensitivity to the toxic effects of phorbol esters. We have now extended this work using a thyroid cell line with an inducible mutant ras gene to exclude the possibility that this result was a trivial consequence of the marked growth stimulation induced in these cells by mutant p21ras. Furthermore, by assessing the action of a panel of phorbol esters and a potential chemotherapeutic agent, bryostatin, we demonstrated that this phenomenon was only a function of biologically active phorbol esters. These results provide a molecular rationale for the development of phorbol ester analogues as chemotherapeutic agents.
Ras protein p21 processing enzyme farnesyltransferase in chemical carcinogen—induced murine skin tumors
Authors: Agarwal Rajesh , Khan Sikandar G. , Athar Mohammad , Zaidi Syed I. A. , Bickers David R. , Mukhtar Hasan 
Published: February 2007

AbstractFarnesylation of ras protein p21 is crucial for the protein's membrane localization, which is essential for its cell‐transforming activity, which in turn is thought to be critical for the ultimate induction of cancer. The cytosolic enzyme farnesyltransferase plays a major role in posttranslational modification of p21, but the level of farnesyltransferase activity in mammalian tumors and its relationship to the processing of cytosolic p21 that leads to tumorigenesis are unknown. We report here that farnesyltransferase activity was significantly higher in chemical carcinogen—induced benign skin papillomas in SENCAR mice than in the epidermises of control animals. The enzyme is primarily epidermal in origin, and kinetic studies with cytosol from epidermis and papillomas showed that the reaction was linear with respect to time, substrate concentration, and protein content. Skin papillomas showed significantly elevated levels of both cytosolic and membrane‐bound Ha‐ras p21, whereas far lesser cytosolic and almost negligible amounts of membrane‐bound p21 were present in the epidermis of control mice. There was a positive correlation between increased enzyme activity in papilloma cytosol and the processing of overexpressed cytosolic Ha‐ras p21 for its localization to membrane.
Correlation of p53 mutations with epidermal growth factor receptor overexpression and absence of mdm2 amplification in human esophageal carcinomas
Authors: Esteve Asuncion , Montesano Ruggero , Hollstein Monica , Lehman Theresa , Harris Curtis C. , Jiang Wei , Weinstein I. Bernard , Ruol Alberto , Peracchia Alberto 
Published: February 2007

AbstractEsophageal carcinomas from 24 patients, most of whom were smokers and consumed alcoholic beverages daily, were analyzed for mutations in exons 5–8 of the p53 tumor suppressor gene. Mutations were identified by polymerase chain reaction amplification and direct sequencing in 12 of 24 (50%) of the samples; almost half of the mutations were at A:T base pairs. Nuclear accumulation of p53 protein, determined by immunohisto‐chemistry with the CM‐1 polyclonal antibody, was observed in all cases in which a missense mutation in the p53 gene was detected. None of the 24 carcinomas had amplification of the mdm2 gene, an alternate pathway to p53 loss of function. Alterations involving three other cancer‐related genes associated with human esophageal carcinogenesis, c‐erbB‐1/epidermal growth factor receptor (EGFR), c‐myc, and retinoblastoma (Rb), were examined by Southern blot or immunohistochemical analysis in the same sample set to explore the possibility of a link between oncogene activation and loss of tumor suppressor function. While no associations were observed between amplification of the c‐myc or EGFR genes and p53 abnormalities, a significant correlation (P < 0.01) was seen between the presence of p53 mutation and EGFR overexpression. Absence of Rb protein, measured immunohistochemically, was observed in four tumors, none of which had aberrations of the p53 gene.
Evidence of two separate mechanisms for the decrease in aryl sulfotransferase activity in rat liver during early stages of 2‐acetylaminofluorene–induced hepatocarcinogenesis
Authors: Ringer David P. , Howell Boyd A. , Norton Tom R. , Woulfe Gary W. , Duffel Michael W. , Kosanke Stanley D. 
Published: February 2007

AbstractEnzymatic and immunohistochemical experiments were conducted to evaluate the mechanistic basis for the downregulation of the important detoxication/bioactivation enzyme aryl sulfotransferase IV (AST IV) during 2‐ acetylaminofluorene (2AAF)–induced hepatocarcinogenesis. To distinguish between possible genotoxic and cytotoxic actions of 2AAF, three different dietary protocols were used in these experiments: group 1 received 2AAF for 12 wk, group 2 received 2AAF for 3 or 6 wk and then a control diet lacking xenobiotics for 3 or 6 wk, and group 3 received 2AAF for 3 or 6 wk and then phenobarbital for 3 or 6 wk. When hepatic AST IV activity was assessed, N‐hydroxy‐2AAF sulfotransferase activity was found to decrease 80–90% in response to 2AAF feeding, but activity recovered to essentially normal levels in the livers of rats subsequently placed on either control diets or diets with phenobarbital, suggesting a reversible cytotoxic mechanism for loss of AST IV activity. However, when liver sections from the rats were evaluated immunohistochemically, two distinct patterns were detected for the downregulation of AST IV expression was observed throughout the liver and among most but not all newly developed nodules. In tissue sections from rats initially fed 2AAF and then placed on a control diet (group 2) or a diet with phenobarbital (group 3), the nodules continued to show low levels of AST IV expression, while expression in the areas surrounding nodules returned to the normal, high levels. In addition, among those rats fed 2AAF for just 3 wk and then control diet or diet containing phenobarbital for 6 wk, only rats fed phenobarbital developed altered foci that stained weakly for AST IV expression. These results show that there were two kinds of 2AAF‐mediated decrease in hepatic AST IV activity: a general overall loss of AST IV expression dependent on administration of 2AAF and reversible upon removal of 2AAF from the diet and a loss of AST IV expression among newly developed liver foci and nodules that persisted in the absence of 2AAF administration and appeared to be a property of 2AAF‐induced subpopulations of cells. These patterns may correspond, respectively, to cytotoxic and genotoxic mechanisms of 2AAF action. © 1994 Wiley‐Liss, Inc.
Increased expression of stromelysin‐3 in basal cell carcinomas
Authors: Majmudar Gopa , Nelson Bruce R. , Jensen Timothy C. , Voorhees John J. , Johnson Timothy M. 
Published: February 2007

AbstractWe examined the expression of two groups of matrix metalloproteinases (MMPs), stromelysin and interstitial collagenase, in human skin cancer by northern blot analysis and in situ hybridization. Stromelyins‐3 (ST‐3) mRNA was overexpressed more than tenfold in 17 of 19 (89%) specimens of basal cell carcinoma (BCC) but in only three of 13 (23%) cutaneous squamous cell carcinomas (SCCs). Stromelysin‐1 and ‐2 (ST‐1/2) mRNA was overexpressed in three of 19 (16%) BCC and three of 13 (23%) SCC. Collagenase mRNA was overexpressed in nine of 19 (47%) BCC and three of 13 (23%) SCC. No mRNA for ST‐3, ST‐1/2, or collagenase was detected by northern analysis in 21 specimens of adjacent normal skin. Because of these findings, we examined the specific location of the ST‐3 mRNA in BCC specimens by in situ hybridization. ST‐3 mRNA was particular abundant in the characteristic stroma adjacent to the invasive basaloid tumor islands of the BCC and absent in the malignant cells. Moreover, ST‐3 mRNA was expressed and induced by phorbol ester treatment in adult dermal fibroblasts but not in keratinocytes. In vitro studies have shown that MMPs are involved in the degradation of extracellular matrix molecules. Our finding of ST‐3 mRNA overexpression in 17 of 19 (89%) BCC specimens is consistent with a role for this molecule in local invasion of stroma by BCC. Our in situ hybridization data suggested that while ST‐3 is not expressed by malignant basal cells themselves, these tumor cells may induce the expression of ST‐3 in adjacent nonmalignant stromal elements such as fibroblasts. © 1994 Wiley‐Liss, Inc.
G→A mutations in p53 and Ha‐ras genes in esophageal papillomas induced by N‐nitrosomethylbenzylamine in two strains of rats
Authors: Lozano Jean‐Claude , Nakazawa Hisayoshi , Cros Marie‐Pierre , Carbral Ricardo , Yamasaki Hiroshi 
Published: February 2007

AbstractIn human esophageal cancers, no ras gene mutations but a relatively high prevalence of p53 gene mutations have been reported. We found a high prevalence of point mutations in Ha‐ras and p53 genes in N‐nitrosomethylbenzylamine (NMBA)‐induced esophageal tumors in two strains of rats (BD VI and F344). Our analysis showed the point mutation GGA←GAA (expected from the known mechanisms of action of NMBA) at Ha‐ras codon 12 in 22 of 46 (48%) and 22 of 38 (58%) papillomas from BD VI and F344 rats, respectively. There was no significant difference in the prevalence of ras mutations in tumors induced by high doses (5.0 mg/kg) and low doses (2.5 mg/kg) of NMBA. Eleven papillomas from each strain were analyzed for p53 mutations. The prevalent mutations found were G←A and C←T transitions. The frequency of p53 mutation was 36% (four of 11) for each strain. No apparent hot‐spot codon or exon was found in the p53 gene, and two papillomas contained double mutations in this gene. The high prevalence of G←A mutations in the rat Ha‐ras gene contrasts with that in the human gene, in which no ras mutations have been found in primary tumors, and suggests either that the biology of esophageal carcinogenesis differs in humans and rats or that nitrosamines are not the major etiological risk factor for human esophageal cancers. © 1994 Wiley‐Liss, Inc.
Mutation and altered expression of p53 genes in experimental rat bladder tumor cells
Authors: Jones Richard F. , Matuszyk Janusz , Debiec‐Rychter Maria , Wang Ching Y. 
Published: February 2007

Abstractp53 genes were analyzed for mutations and expression in a series of 24 tumors or hyperplastic lesions of the urinary bladder induced in F344 rats by carcinogen treatment. Of these, 18 were analyzed as short‐term urothelial cultures. Polymerase chain reaction–single‐strand conformation polymorphism analysis and DNA sequencing were used to detect alterations in p53 genes or cDNAs, and the relative amounts of p53 protein per cell were estimated by immunohistochemical staining. Missense substitutions were found in the exon 5–9 region of two of five cell cultures analyzed from lesions induced by the bladder carcinogen N‐butyl‐N‐(4‐hydroxybutyl)nitrosamine. One of these was a papillary nodular hyperplasia, indicating that p53 mutations can be present in low‐ as well as high‐stage/grade bladder lesions. p53 mutations were not found in the exon 5–9 region in cells of any of eight bladder lesions induced by N‐[4‐(5‐nitro‐2‐furyl)‐2‐thiazolyl]formamide (FANFT), including five transitional cell carcinomas (TCCs), or either of two TCCs induced by N‐methylnitrosourea. Two of nine TCCs induced by the N‐glucuronide of N‐hydroxy‐2‐aminofluorene were found to have p53 mutations. One of these was evidently altered by three genetic events: a missense substitution in exon 8, a nonsense mutation in exon 6, and silencing of the “nonsense” allele (i.e., only the p53 missense mutation was detected). Immunohistochemical analysis with monoclonal antibody PAb240 (which preferentially binds to mutant p53 protein) detected p53 antigen only in those samples in which missense p53 mutations were found. With monoclonal antibody PAb421 (which detects mutant and wild‐type p53), p53 antigen was also detected in cells from F542, a bladder tumor induced by FANFT in which no p53 mutations were found. Northern blot hybridization analysis showed that p53 transcripts were elevated twofold to threefold in several cases, including F542, suggesting that constitutive overexpression of wild‐type p53 may occur in some bladder neoplasias. These data support the view that p53 may be involved in multiple rate‐limiting steps in neoplastic transformation and may be a continuing target during bladder carcinogenesis. The data also contribute to evidence that certain chemical carcinogens may directly alter p53 genes during tumorigenesis. © 1994 Wiley‐Liss, Inc.
Expression in lung tumors and genetic mapping of the novel murine protein kinase Cη
Authors: Canzian Federico , Gariboldi Manuela , Manenti Giacomo , De Gregorio Laura , Osada Shin‐Ichi , Ohno Shigeo , Dragani Tommaso A. , Pierotti Marco A. 
Published: February 2007

AbstractProtein kinase Cη (nPKCη) is a member of the protein kinase C family with a unique tissue distribution in skin and lung. We analyzed nPKCη expression in normal murine lung and in 36 lung tumors induced by urethane in AC3 F1 and F2 mice. The nPKCη‐related transcript was present at fivefold to tenfold lower levels in tumors than in normal lung controls. We mapped two distinct loci for nPKCη on murine chromosome 12, using linkage analysis in an interspecific test cross. The results indicate that the mouse Pkcn‐rs1 and Pkcn‐rs2 loci were about 30 cM from the centromere and about 2 cM from each other. © 1994 Wiley‐Liss, Inc.
Influence of DNA repair by ada and ogt alkytransferases on the mutational specificity of alkylating agents
Authors: Roldán‐Arjona Teresa , Luque‐Romero Francisco L. , Ariza Rafael R. , Jurado Juan , Pueyo Carmen 
Published: February 2007

AbstractWe investigated the influence of the alkyltransferases (ATases) encoded by the ada and ogt genes of Escherichia coli on the mutational specificity of alkylating agents. A new mutational assay for selection of supF‐ mutations in shuttle‐vector plasmids was used. Treating plasmid‐bearing bacteria with N‐methyl‐N‐nitrosourea (MNU), N‐ethyl‐N‐nitrosourea (ENU), and ethyl methanesulfonates (EMS) dramatically increased the muttation frequency (from 33‐fold to 789‐fold). The vast majority of mutations (89–100%) were G:C←A:T transitions. This type of mutation increased in ada‐ (MNU) or ogt‐ (ENU) bacteria, suggesting that repair of O6‐methylguanine by ada ATase and repair of O6‐ethylguanine by ogt ATase contribute mainly to the decrease in G:C←A:T transitions. The analysis of neighboring base sequences revealed an overabundance of G:C←A:T transitions at 5′‐GG sequences. The 5′‐PuG bias increased in ATase‐defective cells, suggesting that these sequences were not refractory to repair. G:C←A:T transitions occurred preferentially in the untranscribed strand after in vivo exposure. That this strand specificity was detected even in bacteria devoid of ATase activity (ada‐ ogt‐) and not after in vitro mutagenesis suggests a bias for damage induction rather than for DNA repair. Highly significant differences were found between the in vivo and in vitro incidences of G:C←A:T substitutions at the two major hotspots, positions 123 (5′‐GGG‐3′; antisense strand) and 168 (5′‐GGA‐3′; sense strand). These results are explained by differences in the probability of formation of stem‐loop structures in vivo and in vitro. © 1994 Wiley‐Liss, Inc.
Infrequent loss of heterozygosity and mutation of the p53 gene in immortal and transformed mouse embryo fibroblasts
Authors: Tokumitsu Masayuki , Kadohama Takayuki , Ogawa Katsuhiro 
Published: February 2007

AbstractSome of the progeny of isolated mouse embryo fibroblasts acquire the ability to grow indefinitely during cultivation, presumably through some mutational events. The relevance of p53 mutations and loss of heterozygosity to the mechanism of such immortal growth capability remains controversial. Since four bases in intron 1 of the p53 gene in C3H/HeJ mice are replaced by 13 different bases in DBA/2J mice, it is possible to distinguish maternal and paternal p53 alleles in the cells of F1 hybrids of these strains (C3D2F1) by electrophoresis of polymerase chain reaction fragments including the region. We established 23 spontaneously immortalized fibroblast cell lines from C3D2F1 mouse embryos and 29 transformed cell lines induced from one of the immortal cell lines, either by treatment with chemical carcinogens or by transfection with the c‐Ha‐ras gene. Of these 52 cell lines, only one, derived from fibroblasts unpassaged for 4 mo, showed p53 gene loss of heterozygosity and a structural alteration in the remaining allele. Our results demonstrated that p53 mutations are not a strict requirement for immortalization and transformation of mouse embryo fibroblasts in Vitro. © 1994 Wiley‐Liss, Inc.
Transcriptlonal activation by viral enhancers: Critical dependence on extracellular matrix‐cell interactions in mammary epithelial cells
Authors: Schmidhauser Christian , Casperson Gerald F. , Bissell Mina J. 
Published: February 2007

AbstractExtracellular matrix (ECM)‐cell interactions are essential for the regulation of many genes in differentiated cell types. A number of expression vectors that work well in cells cultured on tissue‐culture plastic appear to be inactive or sporadically active in vivo. We reasoned that these responses also may be influenced by the ECM. We therefore examined three commonly used viral enhancers and found that they all responded either positively or negatively to the presence of exogenous ECM. Using mouse mammary epithelial cells, we found that a mouse mammary tumor virus enhancer linked to its own promoter or to a truncated (and by itself inactive) β‐casein promoter drove transcription efficiently only when the cells were in contact with an ECM (more than a 100‐fold induction over tissue‐culture plastic). Similarly, the cytomegalovirus enhancer was more active in cells in contact with ECM. In contrast, the simian virus 40 enhancer, linked to the β‐casein promoter, was 12‐fold more active in cells on tissue‐culture plastic. This activity was strongly reduced when the cells interacted with ECM. Thus, we conclude that different enhancers can respond to ECM by either activating or suppressing transcription. This observation has important implications for understanding the mechanisms of promoter action and for designing expression systems for use in gene therapy. © 1994 Wiley‐Liss, Inc.