bluuebunny/crossref_metadata_2025_split huggingface dataset:
Alterations in DMA‐restriction enzyme interactions by O4‐alkyldeoxythymidines
Authors: Richardson Frank C , Richardson Katherine K. 
Published: February 2007

AbstractO4‐Alkyldeoxythymidines have been extensively studied for their ability to cause mutations and to induce cancer. Since these adducts can change DNA conformation, they may also have a more immediate effect of altering DNA‐protein interactions. To address this issue, the effects of these adducts on restriction enzyme activity were examined. Oligodeoxyribonucleosides containing O4‐ethyldeoxythymidine (O4‐EtdT) or O4‐methyldeoxythymidine (O4‐MedT) at a unique site within the sequence 5′‐GAATGGATCCTAATGAGATC‐3′ were constructed by automated DNA synthesis. This sequence contains the recognition site for various restriction enzymes. These oligomers were annealed to various complementary strands and digested with restriction enzymes: BamHI or BstI (GGATCC); Sau3A, Ndell, or Mbol (GATC); Dpnl (GmATC); and BstYl, Mfll, or Xholl (PuGATCPy). Analysis of the digests demonstrated that the presence of either O4‐EtdT or O4‐MedT abolished the ability of Xholl, Mbol, Mfll, or Ndell to cut at the restriction site. Dpnl failed to cut any of the oligomers. BamHI, Sau3A, Bstl, and BstYI exhibited alterations in cutting specificity depending upon the oligomers used. These results demonstrated that O4‐alkyldeoxythymidine adducts alter DNA‐restriction enzyme interactions in a protein‐ and sequence‐dependent manner. Because of the importance of natural methylation in genetic regulation, it is possible that aberrant methylation in the form of DNA adducts could also alter protein‐DNA interactions in cells exposed to DNA‐modifying agents.
Suppression of adenovirus type 5 E1A‐mediated transformation and expression of the transformed phenotype by caffeic acid phenethyl ester (CAPE)
Authors: Su Zao‐Zhong , Grunberger Dezider , Fisher Paul B. 
Published: February 2007

AbstractViral transformation and DNA‐transfection assays were employed to investigate the differential toxic effect of caffeic acid phenethyl ester (CAPE), an extract of the honeybee hive product propolis, on adenovirus type 5 (Ad5)‐transformed cloned rat embryo fibroblast (CREF) cells. CAPE inhibited, in a dose‐dependent manner, both de novo and carcinogen‐enhanced transformation of CREF cells by H5hr1, the cold‐sensitive (cs) host‐range mutant of Ad5. CAPE had a selective inhibitory effect on Ad5‐induced transformation when a wild‐type (wt) Ad5 E1A gene or a es Ad5 E1A gene (at 37°C, but not at 32°C) was cotransfected into CREF cells with a dominant‐acting bacterial hygromycin‐resistance gene. A requirement for the expression of Ad5 E1A‐encoded mRNAs and transforming proteins and sensitivity to CAPE was demonstrated using CREF cells stably transformed by a cs Ad5 E1A gene and an Ad5 E1A gene under the transcriptional control of a mouse mammary tumor virus promoter. To distinguish between the effects of the two Ad5 E1A‐encoded proteins of 289 amino acids (aa) and 243 aa, CREF cells were stably transformed with cDNAs encoding either the 13S or the 12S E1A mRNA. CREF cells expressing the 13S E1A‐encoded 289‐aa protein were more sensitive to the growth‐suppressing effect of CAPE than cells producing only the 12S E1A‐encoded 243‐aa protein. However, the growth‐suppressing and toxic effects of CAPE were greatest in cells expressing both E1A‐encoded transforming proteins. Analysis of the effect of CAPE on E1A and β‐actin gene expression in wt and cs E1A and H5hr1‐transformed CREF cells indicated that low levels of CAPE, which were growth suppressive, did not selectively suppress E1A expression. These results demonstrated that cellular changes induced in CREF cells by the 13S E1A‐encoded 289‐aa protein of Ad5, when expressed alone or in combination with the 125 E1A‐encoded 243‐aa protein, rendered transformed cells sensitive to the growth‐suppressing and toxic effects of CAPE.
Possible involvement of c‐myc but not ras genes in hepatocellular carcinomas developing after spontaneous hepatitis in LEC rats
Authors: Fujimoto Yoshinori , Ishizaka Yukihito , Tahira Tomoko , Sone Hideko , Takahashi Hidetoshi , Enomoto Katsuhiko , Mori Michio , Sugimura Takashi , Nagao Minako 
Published: February 2007

AbstractLEC (Long‐Evans with a cinnamon‐like coat color) rats develop hepatocellular carcinomas (HCCs) spontaneously. We examined mutations of codons 12, 13, and 61 of the Ha‐ras, Ki‐ras, and N‐ras genes in four HCCs by the polymerase chain reaction (PCR)‐single‐stranded DNA direct sequencing method. No ras gene mutations were observed, suggesting that ras activation is not involved in spontaneous hepatocarcinogenesis in LEC rats. The expression of mRNAs for c‐myc, Ha‐ras, c‐raf, and the protein phosphatase 2Aα gene (PP‐2Aα) was also examined in the four HCCs by northern blot analysis. Three of the four HCCs had c‐myc expression levels approximately 30‐fold higher than that in the liver of control Long‐Evans rats with an agouti coat color (LEA), a sibling line of LEC rats, while the remaining HCC had an expression level sevenfold higher than that of control. In contrast, the expression levels of the Ha‐ras, c‐raf, and PP‐2Aα genes were the same as those in the livers of control rats. Studies of c‐myc expression and mitotic index in five other HCCs, two hyperplastic nodules, and two nontumorous portions of livers of HCC‐bearing LEC rats that had chronic‐phase hepatitis suggested that the high level of c‐myc gene expression was not due only to increased cell proliferation but might possibly be more integrally involved in hepatocarcinogenesis.
Activating point mutations of the gsp oncogene in human thyroid adenomas
Authors: O'Sullivan Catriona , Barton Claire M. , Staddon Susan L. , Brown Christopher L. , Lemoine Nicholas R. 
Published: February 2007

AbstractThe gene for the alpha polypeptide chain (αs) of the heterotrimeric G protein Gs can be activated to the putative oncogene gsp by specific point mutations at codons 201 and 227. Such mutations have been reported in 40% of human growth hormone‐secreting pituitary adenomas and in a single autonomously functioning thyroid adenoma. We examined an archival series of 45 differentiated human thyroid tumors by polymerase chain reaction amplification and oligonucleotide hybridization to identify point mutations at each of the affected codons. Successful amplification was achieved in 38 cases, and activating mutations were identified in 5 of 13 (38%) autonomously functioning adenomas, but in none of 16 nonfunctioning adenomas, six papillary carcinomas, or three follicular carcinomas. Our results confirm that the gsp oncogene is involved in the pathogenesis of autonomously functioning tumors but do not support a role in other thyroid tumors.
Analysis of ras DNA sequences in rat renal cell carcinoma
Authors: Recio Leslie , Lane Steven C. , Ginsler Julie , Walker Cheryl 
Published: February 2007

AbstractThe DNA sequences for Ha‐, Ki‐, and N‐ras were determined in six cell lines derived from independent rat hereditary renal cell carcinomas (RCC). Genomic regions encompassing codons 12, 13, and 61 of Ha‐ras, Ki‐ras, and N‐ras, and codon 117 of Ha‐ras were PCR amplified and directly sequenced. The DNA sequences of Ha‐ras and Ki‐ras were normal in all lines tested, as were the codon 12 and 61 sequences of N‐ras. However, DNA sequence variations that could code for amino acid substitutions were observed in codons 13, 14, and 18 of N‐ras in all the lines. The codon 13 Gly→Val alteration observed was consistent with activating N‐ras mutations previously reported. When normal kidney DNA from rats with the hereditary tumor syndrome was sequenced, the same N‐ras sequence variations observed in the tumor lines were found. DNA from outbred Long‐Evans and inbred Fischer rats also had the altered N‐ras sequences. The variant N‐ras sequence was not observed in PCR‐amplified N‐ras cDNA from the RCC lines. Thus, tumor‐associated activation of ras oncogene appears to be an infrequent event in spontaneous rat RCC. In addition, these data indicate that rats contain an N‐ras DNA polymorphism that appears to be a species‐specific anomaly.
Identification of RB and p53 mutations in mouse lymphoma cell lines
Authors: Murakami Akira , Tanaka Harutaka 
Published: February 2007

AbstractWe analyzed the genomic structure and mRNA of the RB and p53 genes in four mouse lymphoid leukemia cell lines (DL‐1, DL‐5, DL‐8, and DL‐12). Although no gross structural alteration of the RB gene was observed in any cell line, abnormalities of RB mRNA were detected in at least two cell lines. RB mRNA expression was greatly reduced in DL‐12. In addition, cloning and sequencing analysis of the RB cDNA revealed that the RB mRNA in DL‐8 had a 276‐nucleotide deletion presumably consisting of exons 10, 11, and 12, suggesting that altered splicing resulted in the loss of these exons. Analysis of the p53 gene indicated that DL‐5 had a deletion in both alleles and expressed a smaller mRNA. These results suggest that mutations of the RB or p53 genes, or both, are associated with lymphoid leukemogenesis in mice.
Mutations in the p53 tumor suppressor gene in human cutaneous squamous cell carcinomas
Authors: Pierceall William E. , Mukhopadhyay Tapas , Goldberg Leonard H. , Ananthaswamy Honnavara N. 
Published: February 2007

AbstractIn this study, we analyzed 10 human squamous cell carcinomas (SCCs) for alterations in the p53 tumor suppressor gene in exons 4 through 9 by single‐strand conformation polymorphism (SSCP) analysis. We found that 2 of 10 SCCs displayed unusual SSC Pallelesat exon 7 of the p53 gene. Subsequent cloning and sequencing of PCR‐amplified exon 7 DNA from these two tumors revealed that one had a G→A transition at the first position of codon 244, predicting a glycine‐to‐serine amino acid change, while the other tumor exhibited a G→T base change at the second nucleotide of codon 248, predicting an arginine‐to‐leucine substitution. Because the mutations in the p53 tumor suppressor gene in both tumors were located opposite potential pyrimidine dimer sites (C‐C), it is consistent with these mutations having been induced by the ultraviolet radiation present in sunlight. These studies demonstrate that inactivation of the p53 tumor suppressor gene, as well as activation of ras oncogenes, may be involved in the pathogenesis of some human skin cancers.
v‐Ha‐ras‐induced mouse skin papillomas exhibit aberrant expression of keratin K13 as do their 7,12‐dimethylbenz[a]anthracene/12‐O‐tetradecanoylphorbol‐13‐acetate‐induced analogues
Authors: Sutter Christian , Strickland James E. , Welty David J. , Yuspa Stuart H. , Winter Hermelita , Schweizer Jürgen 
Published: February 2007

AbstractIntroduction of the v‐Ha‐ras gene into primary epidermal keratinocytes, followed by grafting of these cells to animals, leads to the formation of benign epidermal tumors that resemble papillomas induced chemically by a two‐stage carcinogenesis protocol. In this study, we investigated v‐Ha‐ras‐induced papillomas for aberrant expression of type I keratin K13, previously described in 7,12‐dimethylbenz[a]anthracene/12‐O‐tetradecanoylphorbol ‐13‐acetate (DMBA/TPA)‐induced mouse epidermal tumors. Papillomas produced from three independent infection series were removed 3 wk after grafting concomitant with control grafts originating from mock‐, neo‐, and v‐fos‐infected primary keratinocytes. Combined analysis of the grafts by western blotting of extracted keratins and immunofluorescence studies of frozen sections with a K13‐monospecific antibody revealed K13 expression in all v‐Ha‐ras‐induced papillomas and absence of this keratin in all control grafts. K13‐positive cells in papillomas were restricted to the suprabasal cell layers of the lesions and, at this stage of papilloma development, occurred as foci of varying extensions. Analysis of genomic DNA from v‐Ha‐ras‐induced papillomas for the methylation state of a CpG dinucleotide in the distant promoter region of the K13 gene revealed the occurrence of unmethylated DNA copies that were generated at the expense of methylated DNA copies ubiquitously present in normal epidermis. The ratio of unmethylated to methylated DNA copies correlated with the extent of suprabasal K13 protein expression. Thus, all features of aberrant K13 expression previously described in DMBA/TPA‐induced papillomas were shared by v‐Ha‐ras‐induced papillomas.
Expression of human O6‐methylguanine‐DNA methyltransferase in chinese hamster ovary cells and restoration of cellular resistance to certain N‐nitroso compounds
Authors: Wu Zining , Chan Chung‐Leung , Eastman Alan , Bresnick Edward 
Published: February 2007

AbstractWe have constructed a plasmid in which the expression of human O6‐methylguanine‐DNA methyltransferase (MGMT) cDNA is driven by the Rous sarcoma virus promoter sequence. Transfection of this plasmid into Chinese hamster ovary (CHO) cells results in expression of MGMT and in cellular resistance to N‐methyl‐N′‐nitro‐N‐nitrosoguanidine (MNNG) and 1‐(2‐chloroethyl)‐1‐nitrosourea (CNU), but not to N‐nitroso‐N‐ethylurea. The specific activity of MGMT in transfected CHO cells correlated well with their resistance to MNNG and CNU. Southern analysis showed that the plasmid had been integrated into the CHO cell genome. Western analysis of extracts from transfected CHO cells using an antibody against a peptide corresponding to the carboxyl‐terminal end of the human MGMT protein demonstrated a single band with a molecular size of 24–25 kDa; no such band was observed in extracts from wild‐type CHO cells. These transfected cells may therefore be used to study the role of MGMT in the repair of alkylating DNA lesions and to determine its importance in carcinogenesis as well as in chemotherapy.
Regulation of 2‐acetylaminofluorene‐and 3‐methylcholanthrene‐mediated induction of multidrug resistance and cytochrome P450IA gene family expression in primary hepatocyte cultures and rat liver
Authors: Gant Timothy W. , Silverman Jeffrey A. , Bisgaard Hanne Cathrine , Burt Richard K. , Marino Pamela A. , Thorgeirsson Snorri S. 
Published: February 2007

AbstractPrevious studies by this laboratory have indicated that expression of the multidrug resistance (mdr) gene can be increased in vivo by exposure to a variety of xenobiotics. Because of the nature of these compounds, it was proposed that mdr gene expression might, at least in part, be regulated by the arylhydrocarbon (Ah) receptor. In the present study, we used a primary hepatocyte culture model to examine the relationship between induction of cytochrome P450IA and mdr expression in vitro. Both 3‐methylcholanthrene (MC) and 2‐acetylamino‐fluorene (AAF) were efficient inducers of mdr expression in this model. Induction of mdr gene expression by both MC and AAF obeyed a log10 concentration/response relationship. In contrast, 2,3,7,8‐tetrachlorodibenzo‐P‐dioxin did not induce mdr expression at concentrations that yielded maximum induction of cytochrome P450IA expression. These data suggest that mdr induction was not mediated via the Ah receptor. Nuclear run‐off analysis indicated that both AAF and MC induced mdr expression by increasing transcription. Primer extension analysis indicated that mdr gene transcription was initiated at one major site 151 bp upstream of the ATG site in both the uninduced and induced state in vivo and in vitro. The sequence of the primer and the site of initiation of gene transcription indicate that the main gene induced was the mdr1b gene.
Ultraviolet stimulation of intermolecular homologous recombination in Chinese hamster ovary cells
Authors: Nairn Rodney S. , Adair Gerald M. , Christmann Cynthia B. , Humphrey Ronald M. 
Published: February 2007

AbstractWe previously showed that ultraviolet (UV) irradiation of cotransfected plasmid DNA molecules stimulated genetic transformation that depended on intermolecular homologous recombination in Chinese hamster ovary (CHO) cells. Repair‐proficient cells and an excision repair complementation class 1 (ERCC1) UV‐sensitive DNA repair‐deficient mutant responded similarly to UV stimulation in cotransfections with plasmids containing linker insertion‐disrupted copies of the herpes simplex virus thymidine kinase (HSV‐TK) gene. In this study, we cotransfected homologous DNA molecules containing nonoverlapping deletions of the hamster adenine phosphoribosyltransferase (APRT) gene into APRT‐deficient CHO ERCC1 (UVL‐10) and ERCC2 (UVL‐1) excision‐repair mutants and parental repair‐proficient CHO cells. UV damage in cotransfected circular plasmid molecules stimulated transformation in repair‐proficient cells and an ERCC1 mutant, but not in an ERCC2 mutant. Linearization of plasmids prior to cotransfection greatly enhanced transformation frequencies in all three cell lines, but UV stimulation using linear recombination substrates was no longer evident. Our results suggest (i) that the ERCC1 gene defect in CHO UVL‐10 cells does not affect UV stimulation of homology‐dependent extra‐chromosomal recombination, and (ii) that a CHO cell ERCC2 excision‐repair mutant, although recombination proficient, may exhibit altered recombination in response to UV damage.
Expression and localization of the matrix metalloproteinase pump‐1 (MMP‐7) in human gastric and colon carcinomas
Authors: McDonnell Susan , Navre Marc , Coffey Robert J. , Matrisian Lynn M. 
Published: February 2007

AbstractThe expression of members of the family of matrix‐degrading metalloproteinases (MMPs) is believed to contribute to the complex process of invasion and metastasis. In this study, specific cDNA probes for three members of the stromelysin subfamily of MMPs–stromelysin (MMP‐3), stromelysin‐2 (MMP‐10), and pump‐1 (MMP‐7)–were used to examine the expression of these three different MMPs in human gastric and colonic carcinomas and in adjacent normal mucosa. The expression of pump‐1 mRNA in malignant colon and stomach samples was striking. In a total of 10 gastric carcinoma samples examined, eight (80%) expressed pump‐1 transcripts; similarly, 6 of 8 (75%) colon carcinoma samples were also positive. Stromelysin and stromelysin‐2 mRNAs were not detected in any of these samples. Expression of the MMPs examined was not detected in any of the adjacent, grossly normal tissue samples. Using in situ hybridization and affinity purified anti‐pump‐1 antibodies, the expression of pump‐1 mRNA and protein was localized to tumor cells and was not detected in stromal or lymphocytic cells. This data suggests that the inappropriate expression of pump‐1 by malignant cells may contribute to the neoplastic phenotype.
Detection of extrachromosomal circular DNA sequences from tumor cells by an alkaline lysis, Alu‐polymerase chain reaction technique
Authors: Sen Subrata , Rani Sudha , Freireich Emil J. , Hewitt Roger , Stass Sanford A. 
Published: February 2007

AbstractExtrachromosomal circular DNAs ranging in size from submicroscopic molecules of approximately 100 kb to cytogenetically resolvable structures of 1000+ kb called minute and double‐minute chromosomes have been shown to harbor amplified genes in primary tumor cells, tumor cell lines, and drug‐resistant cells grown in vitro. The presence of these molecules in transformed and malignant cells tends to reflect genetic instability and also suggests their role in tumor progression. Using a colon carcinoma cell line, we developed a technique to detect extrachromosomal circular DNA‐specific sequences by Alu‐polymerase chain reaction. Circular DNA was enriched by selective alkaline denaturation of genomic DNA. We have successfully performed this procedure with a minimum of 5 × 105 cells. The technique does not require any prior knowledge of the sequences located on the covalent circular DNA molecules for their detection. The procedure should be useful as a routine screen of primary tumor cells for the presence of extrachromosomal circular DNA and should permit the preparation of specific probes to aid in their detailed characterizations. © 1992 Wiley‐Liss, Inc.
Influence of poly(ADP ribose) polymerase depletion on promotion of liver carcinogenesis
Authors: Cesarone Carmelo F. , Suzuki Hisanori , Scovassi Anna I. , Scarabelli Linda , Izzo Raffaella , Giannoni Paolo , Mariani Cristina , Miwa Masanao , Orunesu Mauro , Bertazzoni Umberto 
Published: February 2007

AbstractIn previous studies we demonstrated that liver poly(ADP ribose) polymerase (pADPRP) activity was lost in animals exposed to N‐2‐acetylaminofluorene (2AAF) according to the Teebor and Becker experimental model (Cancer Res 31:1–3, 1971). In addition, we used the resistant hepatocyte model of Solt and Farber (Nature 263:702–703, 1976) to further investigate pADPRP activity during the multistep process of liver carcinogenesis. A marked depletion of the catalytic protein was evidenced after 2AAF exposure, confirming previous results and indicating a specific effect of 2AAF on this nuclear enzyme that controls conformational changes of chromatin and regulates several catalytic activities in the nucleus. The levels of pADPRP mRNA, measured by northern blot analysis using both experimental models, indicate that the enzyme depletion is not due to a loss of transcript. Moreover, these data indicate that pADPRP depletion, caused by 2AAF, was also maintained during liver compensatory growth, which is known to induce a rapid and marked increase in pADPRP activity and protein level. Treatment of 2AAF‐exposed animals with N‐acetyl‐L‐cysteine not only efficiently protected against DNA damage, but also prevented a rapid depletion of the catalytic protein. Interestingly, these data indicate that the marked loss of liver pADPRP occurred during the promotion step induced by 2AAF feeding and that this loss was observed using different models for experimental hepatocarcinogenesis. This phenomenon can be ascribed to a highly defective transcript that cannot be correctly translated into the specific protein or to a rapid degradation of the translated protein. © 1992 Wiley‐Liss. Inc.