bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tissue‐specific activating mutations of Ha‐ and Ki‐ras oncogenes in skin, lung, and liver tumors induced in mice following transplacental exposure to DMBA
Authors: Loktionov Alexandre , Hollstein Monica , Martel Nicole , Galendo Dominique , Cabral J. Ricardo P. , Tomatis Lorenzo , Yamasaki Hiroshi 
Published: February 2007

AbstractTransplacental carcinogenesis represents a good model in which to study the involvement of tissue‐specific oncogene activation in carcinogenesis because a single exposure to a carcinogen induces tumors at various sites. We tested tumors of the skin, liver, and lung produced in mice after transplacental 7, 12‐dimethylbenz[a]‐anthracene (DMBA) exposure for possible activation of ras genes. Xbal restriction fragment‐length polymorphism analysis has shown that exposure to DMBA in utero may result in appearance of A → T transversion at the second position of codon 61 of Ha‐ras oncogene in skin and liver tumors but not in lung tumors. Moreover, DNA samples isolated from spontaneous and DMBA‐induced lung and liver tumors were analyzed for mutations at the same position of Ki‐ras oncogene using differential hybridization with specific oligonucleotides. Among five spontaneous lung tumors, three cases of A → G transition, and one case of A → T transversion were found, whereas four of ten lung tumors of DMBA‐treated animals were positive for A → T mutation. No Ki‐ras mutation was detected in one spontaneous and four DMBA‐induced hepatomas. In two cases, we revealed Ki‐ras A → T mutation in the lung tumor and Ha‐ras mutation in the liver tumor taken from the same animal. These results indicate first that DMBA treatment may induce A → T mutation at the second position of codon 61 both in Ha‐ras and in Ki‐ras and, second, that the role of different activated oncogenes in carcinogenesis may differ, depending on the tissue in which the tumor develops.
Activation of c‐Ki‐ras not detectable in adenomas or adenocarcinomas arising in rat pancreas
Authors: Schaeffer Barbara K. , Zurlo Joanne , Longnecker Daniel S. 
Published: February 2007

AbstractThe objective of this study was to determine whether activation of c‐Ki‐ras occurs in carcinogen‐induced rat pancreatic tumors. DNAs from 27 samples, which included adenomas, carcinomas in situ, and adenocarcinomas arising in azaserine‐treated rats and corn oil‐gavaged rats along with a nafenopin‐induced rat pancreatic adenocarcinoma were examined for mutation of c‐Ki‐ras at codons 12, 13, and 61 by using the polymerase chain reaction. Our results indicate that activation of c‐Ki‐ras is not a common event during pancreatic carcinogenesis in the rat.
Point mutation in codons 12 and 61 of the ha‐ras gene in rat urinary bladder carcinomas induced by N‐[4‐(5‐nitro‐2‐furyl)‐2‐thiazolyl]formamide
Authors: Masui Tsuneo , Mann Angela M. , Garland Emily M. , Okamura Takehiko , Johansson Patrik L. , Cohen Samuel M. 
Published: February 2007

AbstractMale F344 rats were fed N‐[4‐(5‐nitro‐2‐furyl)‐2‐thiazolyl]formamide (FANFT) for up to 4 wk, then were given the basal diets (Prolab 3200 or AIN‐76A) with or without 5% sodium saccharin for up to 100 wk. Eleven transitional cell carcinomas (TCCs), one undifferentiated carcinoma, and two sarcomas of the urinary bladder were examined for the expression of ras gene product, p21, by immunohistochemical staining and western blot analysis. Point mutation in codons 12 or 61 of the Ha‐ras genes amplified by polymerase chain reaction was examined by a slot‐blot screening procedure using allele‐specific oligonucleotide probes. Immunohistochemical staining showed enhanced immunoreactivity with the antibody to ras p21 in seven TCCs and one undifferentiated carcinoma. Western blot analysis showed faster migration of the p21 band in 6 of 11 TCCs. Oligonucleotide hybridization revealed the point mutation in codon 12 of Ha‐ras gene (GGA → GTA in 1 TCC) and in codon 61 (CAA → CGA in 5 TCCs and CAA → CTA in 1 TCC). Two mutations in codons 12 and 61 coexisted in one tumor, which were found to be present in different Ha‐ras alleles. The incidence of Ha‐ras gene mutations were similar in groups treated with (3 of 6) or without (3 of 8) sodium saccharin. These results suggest the involvement of activated Ha‐ras gene in rat urinary bladder carcinogenesis induced by FANFT.
DNA sequence analysis of gamma radiation—induced deletions and insertions at the APRT locus of hamster cells
Authors: Miles Carol , Sargent Geoffrey , Phear Geraldine , Meuth Mark 
Published: February 2007

AbstractGamma radiation–induced gene rearrangements at the Chinese hamster ovary cell locus coding for the purine salvage enzyme adenine phosphoribosyl transferase (APRT) consist of both simple deletions and more complex alterations that are presumably the result of multiple strand breaks. To characterize these mutations at the DNA sequence level, fragments altered by deletion and insertion mutations were obtained by cloning in λ phage vectors or by using the polymerase chain reaction. The radiation‐induced deletions characterized here eliminate 3–4 kb and have at least one breakpoint in an AT‐rich region or near short direct or inverted repeats. Insertions involve small fragments (102 and 456 bp) of repetitive DNA that appear to be related to B2 (short interspersed repetitive) and long interspersed repeat families. The novel fragments bear little resemblance to each other or to sequences at the integration sites, and their introduction is accompanied by a small target site deletion.
Deletion mapping of tumor promotion–susceptibility gene pro1 implicates an RNA polymerase III transcription unit
Authors: Garrity Robert R. , Hegamyer Glenn A. , Seed John L. , Colburn Nancy H. 
Published: February 2007

AbstractThe murine gene pro1 has been cloned from JB6 epidermal cell lines that are sensitive to neoplastic transformation by tumor promoters. Insensitive JB6 variants acquire susceptibility to neoplastic transformation by tumor promoters when transfected with pro1. The repetitive nature of pro1 was indicated by sequence and Southern analysis. In contrast, northern analysis of RNA from promotion‐sensitive cells revealed the presence of a small pro1‐hybridizing transcript. Strand‐specific RNA probes implicated an RNA polymerase III (RNAPIII) coding domain in pro1 as the source of this hybridization signal. Ribonuclease protection of gel‐purified pro1 RNA from JB6 variant cell lines identified a 130‐nucleotide transcript. The size of this transcript is compatible with in vitro RNAPIII transcription of pro1. Deletion mapping of pro1 by exonuclease III demonstrated that the biologically active domain included the RNAPIII transcription unit. RNA probes map pro1 RNA within the activity domain. These results delineate an activity domain of 597 nucleotides and suggest that a small RNA is the product of promotion‐sensitivity gene pro1.
Amplification and expression of the c‐erb B‐2/neu proto‐oncogene in human bladder cancer
Authors: Zhau Haiyen E. , Zhang Xin , Von Eschenbach Andrew C. , Scorsone Kathleen , Babain R. Joseph , Ro Jae Y. , Hung Mien‐Chie 
Published: February 2007

AbstractThe c‐erb B‐2/neu gene encodes a cell‐surface glycoprotein with extensive homology to, but distinct from, the epidermal growth‐factor receptor. In this study, we compared the c‐erb B‐2/neu gene amplification and expression of tissue specimens obtained from the bladders of normal controls and patients with high‐grade transitional cell bladder carcinoma. Southern blot analysis of DNAs from 24 patients and 5 controls showed 2 cases of c‐erb B‐2/neu gene amplification in patients and none in controls. Western blot analysis demonstrated that c‐erb B‐2/neu was expressed in 67.6% (23/34) of patient specimens but in none of the controls (0/5). This finding agreed with the result of immunohistochemical staining, which showed that tissue from 74.3% (26/35) of the patients and none of the controls (0/7) showed positive immunofluorescence staining. This is the first report suggesting that c‐erb B‐2/neu gene amplification and expression may be associated with human bladder carcinogenesis.
Aberrant expression of gap junction gene in primary human hepatocellular carcinomas: Increased expression of cardiac‐type gap junction gene connexin 43
Authors: Oyamada Masahito , Krutovskikh Vladimir A. , Mesnil Marc , Partensky Christian , Berger Françoise , Yamasaki Hiroshi 
Published: February 2007

AbstractThe expression of connexin 32 (the major liver gap junction protein) and connexin 43 (the major cardiac gap junction protein) was examined in six surgically removed human hepatocellular carcinoma tissues and the surrounding nontumorous livers using specific rat connexin probes. No decrease in connexin 32 mRNA expression was found in carcinomas compared with the surrounding nontumorous tissue. Morphometrical analysis also showed that in most of the carcinomas the number of gap junction spots stained with connexin 32 antibody was not less than that in the surrounding livers. These results are in striking contrast to the significant reductions in connexin 32 mRNA and protein expression observed in rat primary liver tumors induced by chemicals. On the other hand, all of the six human hepatocellular carcinomas exhibited elevated levels of connexin 43 mRNA, which was expressed at a very low level in the surrounding nontumorous livers. These carcinomas exhibited no detectable amplification of the connexin 43 gene. The present study suggests that gap junctional intercellular communication is altered in human hepatocellular carcinomas by molecular mechanisms different from those in rat hepatocarcinogenesis.
Ki‐ras activation and expression in transformed mouse lung cell lines
Authors: Pan Y. H. Laurie , Nuzum Edwin O. , Hanson Laurie A. , Beer David G. 
Published: February 2007

AbstractThe Ki‐ras proto‐oncogene is activated by specific point mutations and is the transforming gene often identified in rodent and human lung tumors. An in vitro model to aid in the study of the consequences of Ki‐ras activation and expression in mouse lung is needed. Accordingly, we have examined cell lines derived from chemically induced mouse lung tumors as well as spontaneous transformants of untreated mouse lung epithelial cells. The specific Ki‐ras‐activating gene mutations and the level of mRNA expression were examined for each cell line. Polymerase chain reaction and oligonucleotide hybridization were used to demonstrate that five of seven transformed lung cell lines contain codon 61 Ki‐ras‐activating mutations, resulting in an arginine substitution for wild‐type glutamine. One transformed line contained this activating mutation and had also lost, or contained an altered, wild‐type codon 61 Ki‐ras allele. No codon 12 Ki‐ras mutations were observed. Two transformed and two nontransformed epithelial lung cell lines contained only the wild‐type codon 12 and 61 Ki‐ras alleles. Northern blot analysis demonstrated that the Ki‐ras mRNA was present in all the cell lines and was overexpressed in some, but not all, of the transformed lung cell lines. Those transformed lines with the highest levels of Ki‐ras mRNA also expressed more H4‐histone mRNA, suggesting that these cells have a greater proliferation rate. The level of Ki‐ras mRNA increased during the proliferation of the nontransformed lung cells but then decreased upon reaching confluency. In contrast, the level of Ki‐ras mRNA in the transformed lung cells was high during both growth and confluency, suggesting a potential defect in the regulation of Ki‐ras in these cells. These lung cell lines will help provide a better understanding of the regulation of both the Ki‐ras proto‐oncogene and oncogene in the lung.
Elevated expression of secondary, but not early, responding genes to phorbol ester tumor promoters in papillomas and carcinomas of mouse skin
Authors: Hashimoto Yu , Tajima Osamu , Hashiba Hiroki , Nose Kiyoshi , Kuroki Toshio 
Published: February 2007

AbstractA single topical treatment of mouse skin with the potent tumor promoter 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) results in transient inductions of a variety of genes. Based on the time courses of their inductions, these genes can be classified into two main groups: “early” response genes whose mRNA expression reaches a maximum 0.5‐2h after TPA treatment and “secondary” response genes whose mRNA expression is maximal 4 h or more after treatment. The nuclear oncogenes c‐fos, c‐myc, and c‐jun belong to the early response group, whereas the metallothionein, osteopontin, and urokinase genes belong to the secondary response group. The steady‐state expressions of these early and secondary response genes are all very low in normal skin, except that of c‐jun, which is relatively high. Steady‐state levels of expression and inducibility of these genes by TPA were not altered in initiated skin or in apparently normal skin during tumor promotion. We examined the expressions of these genes in papillomas and carcinomas produced by two‐stage (initiator‐promoter) and three‐stage (initiator‐promoter‐initiator) protocols in mouse skin. Steady‐state expression of the early responding nuclear oncogenes in papillomas and carcinomas was found to remain at the same low level as in normal skin. However, all the secondary responding genes were found to be expressed constitutively at high levels in these tumors. Elevated expressions of the genes for transforming growth factor α and β were also observed in papillomas and to varying extents in carcinomas. These observations suggest that the regulatory machinery for transcription by the protein kinase C‐me‐diated pathway through nuclear oncogenes is altered during the processes of tumor promotion and progression. The genes whose expression is elevated may be associated directly or indirectly with tumor promotion and progression.
Effects of ionizing radiation on expression of genes encoding cytoskeletal elements: Kinetics and dose effects
Authors: Woloschak Gayle E. , Shearin‐Jones Pocahontas , Chang‐Liu Chin‐Mei 
Published: February 2007

AbstractWe examined the modulation in expression of genes encoding three cytoskeletal elements (β‐actin, γ‐actin, and α‐tubulin) in Syrian hamster embryo (SHE) cells following exposure to ionizing radiations. Early‐passage SHE cells were irradiated in plateau phase with various low doses (12‐200 cGy) of neutrons, γ‐rays, or x‐rays. RNA samples were prepared from cells at different times postexposure and were analyzed for levels of specific transcripts by northern blots. The results revealed that α‐tubulin was induced by both high‐linear energy of transfer (LET) (neutrons) and low‐LET (γ‐rays and x‐rays) radiations with similar kinetics. The peak in α‐tubulin mRNA accumulation occurred between 1 and 3 h postexposure; for γ‐actin mRNA, accumulation was similarly induced. For both γ‐actin and α‐tubulin, the higher the dose during the first hour postexposure (up to 200 cGy γ‐rays), the greater the level of mRNA induction. In contrast, mRNA specific for β‐actin showed decreased accumulation during the first hour following radiation exposure, and remained low up to 3 h postexposure. These results document the differential modulation of genes specific for cytoskeletal elements following radiation exposure. In addition, they demonstrate a decrease in the ratio of β‐actin:γ‐actin mRNA within the first 3 h following γ‐ray exposure. These changes in mRNA accumulation are similar to those reported in some transformed cell lines and in cells treated with tumor promoters, which suggests a role for changes in actin‐ and tubulin‐mRNA expression in radiation‐mediated transformation.
Activated Ki‐ras proto‐oncogene in spontaneously transformed and chemical tumor‐derived cell lines related to the mouse lung alveologenic carcinoma
Authors: Leigh Don A. , Ferguson Vicki , Bentel Jacqueline M. , Miller Juliet O. , Smith Garry J. 
Published: February 2007

AbstractAn in vitro cell model of mouse lung alveologenic carcinoma consisting of preneoplastic nonmalignant cells, spontaneously transformed cells, and urethane‐induced malignant cells was analyzed for phenotypic and genotypic changes associated with the transition to neoplasia. The polymerase chain reaction (PCR) was used to amplify the cDNA derived from the c‐Ki‐ras mRNA corresponding to exons 1 and 2 of the proto‐oncogene. This approach allowed analysis of the gene transcription product rather than potentially unexpressed DNA. Direct sequencing of the PCR product identified a common single point mutation, alone or together with wild‐type mRNA for c‐Ki‐ras, in all of the malignant clones. An A → G transition in the second base position of codon 61 was common to spontaneously malignant and chemical tumor‐derived cell lines and to lines selected for lung metastatic behavior. The absence of the mutation in the nonmalignant cells suggests that the Ki‐ras mutation may be a factor in onset or maintenance of the malignant phenotype and, at least in vitro, may be a late event in the transformation process.
Detection of loss of heterozygosity in the p53 gene in renal cell carcinoma and bladder cancer using the polymerase chain reaction
Authors: Oka Koji , Ishikawa Jiro , Bruner Janet M. , Takahashi Rei , Saya Hideyuki 
Published: February 2007

AbstractThe human p53 gene, a putative tumor suppressor gene, has a polymorphism in amino acid residue 72. We recently developed a method of detecting codon 72 polymorphism in this gene by digestion of polymerase chain reaction–amplified DNA using an allele‐specific restriction endonuclease. This polymorphism allows the identification of loss of heterozygosity for the coding region of the p53 gene in limited tissue samples in a short time without using radioactive materials. We examined 33 patients with renal cell carcinoma and 29 with bladder cancer; heterozygosity in the p53 gene was lost in 60% (6 of 10 cases) and 73% (8 of 11 cases) of the renal and bladder tumors, respectively. Additionally, the assay's sensitivity could be improved by using DNA extracted from frozen sections of the tumors. Because the proportions of tumor cells and nontumor cells could be assessed by microscopic evaluation of the frozen sections, we were able to minimize contamination from nontumor cells, which occasionally causes false readings of retained heterozygosity. This simple and sensitive method for detecting loss of heterozygosity in the p53 gene makes it possible to rapidly screen a large number of tissue samples and has the potential to be a useful diagnostic tool for a wide variety of human neoplasms.
Transformation of Human Breast Epithelial Cells by c‐Ha‐ras Oncogene
Authors: Basolo Fulvio , Elliott James , Tait Larry , Chen Xiao Qin , Maloney Terry , Russo Irma H. , Pauley Robert , Momiki S. , Caamano Jorge , Klein‐Szanto Andres J. P. , Koszalka Maria , Russo Jose 
Published: February 2007

AbstractTo determine whether the c‐Ha‐ras oncogene plays a role in the initiation of mammary carcinogenesis, an immortalized human breast epithelial cell line, MCF‐10A, was transfected with the plasmid vector pHo6T1 containing the T24 Ha‐ras oncogene and the aminoglycoside phosphotransferase gene, which confers resistance to geneticin. Transfected cells exhibited an altered pattern of growth and tridimensional morphology in collagen gel. They also exhibited anchorage‐independent growth and loss of requirement for hormones and epidermal growth factor; in addition, they expressed invasiveness and increased collagenolytic activity in an in vitro system and became tumorigenic in irradiated nude mice, all properties indicative of malignant transformation. Transformed cells contained the mutated c‐Ha‐ras oncogene and expressed the p21 mutated protein. These data indicate that the c‐Ha‐ras oncogene is capable of inducing malignant phenotypes in immortalized human breast epithelial cells.
Expression of ras genes in rainbow trout liver
Authors: Mangold Kathy , Chang Yung‐Jin , Mathews Catherine , Marien Koenraad , Hendricks Jerry , Bailey George 
Published: February 2007

AbstractMembers of the ras gene family have been studied in a variety of species. Two ras genes expressed in the normal liver of rainbow trout, ras‐1 and ras‐2, as well as a portion of a genomic ras‐1 allele, are described for the first time in this report. Over 500 bp of trout ras‐1 and at least 300 bp of trout ras‐2 genes expressed in normal liver have been sequenced; DNA homology to the human ras genes ranges from 76.8% to 87.1%. The base changes resulting from over 400 million years of evolutionary divergence between the species were primarily silent, with few changes in protein sequence. The partial DNA sequence of the genomic ras‐1 allele has 86.8% homology to the first two exons of human c‐Ha‐ras, and its intron has several conserved sequences characteristic of vertebrate intron‐exon junctions. However, the predicted amino acid sequence of trout ras‐1 differs at only one of the first 172 amino acid residues from human c‐Ki‐ras with the alternate exon 4b. Since trout ras‐1 differs at 17 and 18 residues from the human c‐N‐ras and c‐Ha‐ras proteins, respectively, over this region, we conclude that trout ras‐1 is a c‐Ki‐ras gene. The highly conserved nature of this gene suggests that the ras p21 protein has identical functions in normal and neoplastic cells among higher and lower vertebrates.
Structural analysis of the mouse c‐HA‐ras gene promoter
Authors: Plumb Mark , Telliez Jean‐Baptiste , Fee Frances , Daubersies Pierre , Bailleul Bernard , Balmain Allan 
Published: February 2007

AbstractPrevious studies have demonstrated that the mouse c‐Harvey ras proto‐oncogene (c‐Ha‐ras,) promoter sequences are GC rich and contain several potential transcription factor SP1 binding sites. We investigated the endonuclease hypersensitivity of this region in nuclei in vitro and whole mouse tissues in vivo and identified a very strong, ubiquitous hypersensitive site covering the proximal promoter sequences. Footprint protection studies using nuclear extracts from various cell types including fibroblasts, erythroid cells, and both normal and transformed epithelial cells revealed a consistent protein‐binding pattern. Five protein binding sites were observed, four of which correlated with potential SP1 binding sites. Competition experiments using an oligonucleotide corresponding to a consensus SP1 binding site confirmed that these sequences were indeed bound by the SP1 (or SP1‐like) trans‐acting factor. In addition, no differences were observed between the footprint patterns obtained using extracts from cells of different lineages or between normal and transformed epithelial cells carrying activated ras genes. The controlling elements responsible for differential c‐Ha‐ras transcription between cell types or at different stages of carcinogenesis therefore probably lie in other regions of the gene.
Dietary N‐3 fatty acids do not affect induction of Ha‐ras mutations in mammary glands of NMU‐treated rats
Authors: Ronai Zeev , Lau Yoyen , Cohen Leonard A. 
Published: February 2007

AbstractThe purpose of this study was to determine whether dietary n‐3 polyunsaturates (PUFA) can affect the frequency of N‐nitrosomethylurea (NMU)‐induced Ha‐ras mutations in virgin female F344 rat mammary glands. Two groups of 15 rats each were fed isocaloric diets containing either 23% w/w corn oil or corn oil plus menhaden oil (1:1) at starting 14 d before NMU administration (day 50 of age) and continuing for 13 wk. Mammary gland samples were taken serially at 3, 5, 9, and 13 wk post‐NMU treatment. Total cellular DNA was isolated and analyzed by a newly devised enriched amplification procedure that involves predigestion of normal Ha‐ras alleles at codon 12, amplification of the mutant alleles, and restriction fragment length polymorphism analysis. Selective amplification enabled the detection of Ha‐ras mutations as early as 3 wk post–NMU treatment. Approximately 40‐50% of all glands and 75% of all rats tested had the Ha‐ras codon 12 mutation. No significant differences were found between the two dietary groups at any time point, indicating that the mammary tumor‐inhibiting effect of n‐3 PUFA is probably not exerted at the level of the Ha‐ras activation step in NMU tumorigenesis.