bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neoplastic transformation of a human bronchial epithelial cell line by a recombinant retrovirus encoding viral harvey ras
Authors: Amstad Paul , Reddel Roger R. , Pfeifer Andrea , Malan‐Shibley Louise , Mark George E. , Harris Curtis C. 
Published: February 2007

AbstractActivated ras oncogenes have previously been implicated in the pathogenesis of human lung carcinomas. A v‐Ha‐ras‐containing retrovirus, Zip‐ras, was generated by inserting the coding region of the v‐Ha‐ras oncogene into the Zip‐NeoSV(X) [Cepko et al., Cell 37:1053–1062, 1984] retroviral vector. Amphotrophic Zip‐ras retrovirus was used to infect an SV40 large T antigen‐positive immortalized cell line, BEAS‐2B, derived from normal bronchial epithelial cells, the predominant progenitor cells of human lung carcinomas. Zip‐ras—infected BEAS‐2B cells selected for G418 resistance formed anaplastic carcinomas in 12 of 15 athymic nude mice (latency 3 wk), whereas Zip‐NeoSV(X)—infected BEAS‐2B control cultures inoculated into 12 nude mice formed no tumors after a minimum of 7 mo. Tumor cell lines were established and demonstrated to be of human epithelial origin and to express v‐Ha‐ras p21 protein. A common feature of the tumor cell lines was an increase in ploidy. The increased efficiency of neoplastic transformation by v‐Ha‐ras of cell lines as compared with our previous results with normal bronchial epithelial cells [Yoakum et al., Science 227:1174–1179, 1985] is consistent with the hypothesis that the “immortalization” step is rate‐limiting in in vitro human epithelial cell carcinogenesis.
Isolation and characterization of the 5′ flanking region of the mouse C‐harvey‐ras gene
Authors: Brown Ken , Bailleul Bernard , Ramsden Martin , Krumlauf Frances Fee, Robb , Balmain Allan 
Published: February 2007

AbstractThe complete 5′ flanking region of the murine c‐Ha‐ras gene was cloned and sequenced. An untranslated exon (–1) was identified and the promoter region of the gene located. Like the rat and human homologues, the murine promoter is GC rich and contains several GC boxes together with a CAAT element, but lacks a TATA box, an arrangement similar to that found in many housekeeping genes. From primer extension studies, the gene was shown to have three transcriptional start sites, whose positions differ from those previously found for the human gene. No alterations in these start sites were detected between the normal gene and activated Haras genes from mouse skin tumors. A region of strong homology between mouse, rat, and human Ha‐ras genes exists within the large intron separating exon (‐1) from the first coding exon. In addition, from chloramphenicol acetyltransferase assays, the upstream region has promoter activity which appears to be enhanced by the inclusion of sequences within this intron.
Malignant progression of papilloma‐derived keratinocytes: Differential effects of the ras, neu, and p53 oncogenes
Authors: Dotto Gian Paolo , O'connell John , Patskan George , Conti Claudio , Ariza Aurelio , Slaga Thomas J. 
Published: February 2007

AbstractThe p117 keratinocyte cell line was derived in culture from chemically induced mouse papillomas. The benignly transformed nature of these cells was demonstrated by their ability to re‐form benign papillomas when grafted back onto the animal. Retroviral vectors were used to introduce into the p117 cells three distinct oncogenes: v‐Ha‐ras, p53, and neu. All three oncogenes were able to induce tumorigenic conversion of the p117 keratinocytes when assayed by subcutaneous injection into nude mice. However, grafting the oncogene‐transformed cells onto the back of the mouse revealed important differences in the ability of the three oncogenes to induce a fully malignant phenotype. While the ras‐transformed papilloma cells formed aggressive carcinomas, p53 and neu transformation yielded an intermediate phenotype, with formation of large exophytic tumors, not yet invasive but with highly dysplastic features remarkably similar to those of in situ carcinomas. These findings establish a homologous, genetically modifiable cell system in which various stages of malignant transformation can be directly compared.
Neoplastic transformation and lineage switching of rat liver epithelial cells by retrovirus‐associated oncogenes
Authors: Garfield Susan , Huber Brian E. , Nagy Peter , Cordingley Michael G. , Thorgeirsson Snorri S. 
Published: February 2007

AbstractTumors produced by a chemically transformed rat liver epithelial (RLE) cell line and its single cell‐derived clonal subpopulations demonstrate wide‐ranging morphological presentations including carcinomas, sarcomas, “mixed epithelial‐mesenchymal” tumors, and undifferentiated tumors [Am J Pathol 127:168–181, 1987]. To address the question of heterogeneity of tumors derived from transformed RLE cells, we have used recombinant retroviruses containing the following transforming oncogenes: v‐raf (3611‐MSV), v‐raf/v‐myc (J2), v‐myc (J5), and v‐Ha‐ras (pRNR16). All of the oncogenes, with the exception of v‐myc (J5), were efficient transforming agents in the RLE cells. Tumors derived from the v‐raf‐ and, to a lesser extent, those from v‐Ha‐ras—transformed RLE cells showed mixed epithelial‐mesenchymal morphology, whereas the combination of v‐raf/v‐myc (J2) consistently produced differentiated trabecular carcinomas. These data suggest that the lineage commitment of the RLE cells can be perturbed by a single transforming oncogene and that different tumor types derived from these cells may reflect the expression of a selective oncogene or a combination of oncogenes.
Activation of transcription as a general mechanism of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin action
Authors: Fisher Joan M. , Jones Keith W. , Whitlock James P. 
Published: February 2007

AbstractWe studied the response to 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) of mouse hepatoma cells that contain a single, integrated copy of a chimeric gene under the control of a dioxin‐responsive DNA domain, which was originally associated with the cytochrome P450IA1 gene. Our findings indicate that TCDD increases the RNA polymerase II‐catalyzed transcription rate of the chimeric gene and that the transcripts are initiated at the correct promoter. Therefore, the dioxin‐responsive DNA operates as a bona fide transcriptional enhancer. Other studies imply that the Ah receptor mediates the transcriptional response to TCDD. Our results indicate that the Ah receptor‐dependent, dioxin‐responsive enhancer can activate transcription when in a regulatory context and in a chromosomal location different from those of the cytochrome P450IA1 gene. Therefore, in principle, the receptor‐enhancer system represents a mechanism by which numerous genes can respond to aromatic hydrocarbons in the environment.
Cotransfection of plasmids with ras and myc oncogenes to diploid cells derived from rodent fetuses: Alteration of neoplastic transformation frequency depending on the gestation period
Authors: Yagi Takashi , Sasayama Satoshi , Sasai Hitoshi , Kakunaga Takeo 
Published: February 2007

AbstractTo analyze the mechanism of neoplastic transformation of rodent diploid cells by ras and myc oncogenes, human EJ c‐Ha‐ras and mouse c‐myc second and third exons promoted by SV40 promoter were connected to pSV2neo and pSV2gpt, respectively. Mouse and rat primary fetal cells cotransfected with both genes formed transformed and nontransformed colonies in a medium containing G418 and myc ophenolic acid (MPA). The proportion of transformed colonies in the total G418/MPA‐resistant colonies decreased dependent on the stage of the gestation period of rat fetuses from which primary cells had been obtained. Analysis of randomly isolated colonies showed that the transformed colonies had a high copy number and high amount of expression of the introduced genes, were anchorage independent, and were tumorigenic in nude mice. On the other hand, the nontransformed colonies had a low copy number, low amount of expression, and no tumorigenicity. This contrast indicated not only that the activated Ha‐ras and myc oncogenes had been integrated, but also that the amplification or overexpression (or both) of these genes was required for the rodent diploid cells to be transformed. We conclude that early‐stage rat fetal cells might have endogenous factors that promote cell transformation. Alternatively, late‐stage cells might have factors that suppress cell transformation by activated Ha‐ras and myc oncogenes.
Spontaneous progression of hyperplastic outgrowths of the D1 lineage to mammary tumors: Expression of mouse mammary tumor virus and cellular proto‐oncogenes
Authors: Knepper Janice E. , Kittrell Frances S. , Medina Daniel , Butel Janet S. 
Published: February 2007

AbstractMammary cancer in mice is characterized by progression through defined stages of preneoplasia, with the most common preneoplastic stage being the hyperplastic alveolar nodule (HAN). We determined the relative levels of RNA expression of various cellular proto‐oncogenes and endogenous mouse mammary tumor virus genes in outgrowths and tumors of three sublines of the transplantable D1 HAN preneoplastic outgrowth line. The three sublines differed in relative tumor‐producing capabilities. Subline D1B produced a high incidence of tumors with short latency periods, whereas sublines D1C and D1D produced low incidences of tumors with long latency periods. No consistent alteration in proto‐oncogene expression correlated with relative tumorigenicity, although tumors frequently contained higher levels of one or more proto‐oncogene transcripts as compared with preneoplastic tissue. Slightly elevated (2‐ to 6‐fold) levels of different oncogene transcripts were detected in 13 of 17 tumors as compared with outgrowth tissue, including abl (2 tumors), fps (5 tumors), Ha‐ras (6 tumors), and Ki‐ras (8 tumors). One tumor contained 45 times more Ki‐ras‐specific RNA than outgrowth tissue because of a comparable amplification of Ki‐ras DNA sequences. Elevated levels of Ha‐ras occurred more frequently in tumors of a high‐incidence subline than in a less‐aggressive subline (5/10 vs 1/7), but this difference was not statistically significant. However, consistent changes in MMTV expression accompanied progression from preneoplastic tissues to mammary tumors. All 17 tumors displayed reduced levels of the MMTV‐specific long terminal repeat (LTR) transcript (1.6 kb) as compared with HAN tissue; tumors with moderate levels of LTR transcript expressed the 3.8‐kb envelope message as well, one not detected in HANs. Expression of the LTR transcript is apparently influenced by factors in addition to the methylation status of endogenous mouse mammary tumor virus genes, which was similar in outgrowths and tumors. As the survey of representative proto‐oncogenes failed to identify a uniform change between HAN and tumors, it is likely that other genes are involved in tumor progression in the mammary gland.
Preferential modification of GC boxes by benzo[a]pyrene‐7,8‐diol‐9,10‐epoxide
Authors: Kootstra Arend , Lew Linda Kao , Nairn Rodney S. , Macleod Michael C. 
Published: February 2007

AbstractThe distribution of binding sites for the ultimate carcinogen anti‐benzo[a]pyrene‐7,8‐diol‐9, 10‐epoxide(BPDE‐l) in the 5′ region of the Chinese hamster ovary aprt gene has been determined. A plasmid (pGAL) containing the entire hamster aprt gene including the 3′ and 5′ flanking regions was inserted into the BamHl site of the multiple cloning site of pGEM so that the T7 promoter was 5′ to the aprt gene. In vitro transcription of BPDE‐l‐modified pGAL, using the T7 RNA polymerase, revealed two prominent transcriptional stop sites. One of these sites was located in the first exon of the aprt gene, whereas the second transcriptional stop was located approximately 150 bp upstream from the translational start site. This latter region contains two perfect GC‐box consensus sequences that are potential Sp1 binding sites. Using a specific laser cutting technique to map BPDE‐I DNA binding sites in the 5′ flanking region of the aprt gene, we found that the DNA region containing the GC‐box consensus sequences was indeed a hot spot for BPDE‐I modification.
Normal human chromosome 11 suppresses tumorigenicity of human cervical tumor cell line SiHa
Authors: Koi Minoru , Morita Hiroyuki , Yamada Hideto , Satoh Hitoshi , Barrett J. Carl , Oshimura Mitsuo 
Published: February 2007

AbstractWe examined the ability of human chromosome 11 derived from normal fibroblast cells to suppress the tumorigenicity of SiHa cells, a human cervical tumor cell line. Using DNA transfertion, the human chromosome was tagged with a selectable marker (the pSV2neo gene, which encodes resistance to the antibiotic G418), transferred to mouse A9 cells by cell hybridization and microcell transfer techniques, and then transferred to SiHa cells by microcell transfer. These procedures resulted in the appearance of 15 independent, G418‐resistant clones, 5 of which had one or two extra copies of an intact human chromosome 11. In situ chromosomal hybridization of these clones with the pSV2neo plasmid revealed the presence of a neo‐tagged human chromosome 11 in all of the five SiHa‐microcell hybrids. Two SiHa‐microcell hybrids that contained a single copy of neo‐tagged human chromosome 12 were also isolated by the same methods. The tumorigenicities of SiHa clones with one or two extra copies of chromosome 11 (SiHa‐11) were suppressed; four of the five SiHa‐11 clones formed no tumors in nude mice, whereas both parental SiHa cells and SiHa cells with an extra chromosome 12 formed tumors within 30 d. One SiHa‐11 cell clone formed a single tumor 90 d after injection. This rare tumor had lost one copy of chromosome 11 and rapidly formed tumors when reinjected. These results indicate that the introduction of a single copy of normal human chromosome 11, but not chromosome 12, suppresses the tumorigenicity of SiHa cells, indicating the presence on human chromosome 11 of a putative tumor‐suppressor gene (or genes) for human cervical tumors.
Sequential trisomization of chromosomes 6 and 7 in mouse skin premalignant lesions
Authors: Aldaz C. Marcelo , Trono David , Larcher Fernando , Slaga Thomas J. , Conti Claudio J. 
Published: February 2007

AbstractUsing a direct cytogenetic technique, we identified a nonrandom trisomy of chromosome 6 in 12 of 12 aneuploid mouse skin papillomas and in 10 of 11 squamous cell carcinomas induced by chemical carcinogenesis. The second most common abnormality observed was trisomy of chromosome 7 found in most dysplastic papillomas and in 10 of 11 carcinomas. The two trisomies were the only abnormalities found in all aneuploid papillomas and in several carcinomas. Mutation at codon 61 of the Ha‐ras gene, which resides on chromosome 7, was also a common feature of the tumors sampled.Extensive homology exists between mouse chromosome 6 and human chromosome 7, the trisomy of which was recently suggested as a primary cytogenetic event in several human epithelial cancers. We propose a multistep model of tumor progression in which a sequence of specific nonrandom chromosomal abnormalities appear to be required for malignant transformation.
Activation of the cellular harvey ras gene in mouse skin tumors initiated with urethane
Authors: Bonham Keith , Embry Travis , Gibson David , Jaffe Debbie R. , Roberts Robin A. , Cress Anne E. , Bowden G. Tim 
Published: February 2007

AbstractMouse skin tumors, benign papillomas, and squamous cell carcinomas (SCCs) were initiated by a single topical application of urethane followed by repeated promotion with 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA). Using the NIH 3T3 focus forming assay, dominant transforming activity was detected in DNA isolated from SCC samples. Rearranged and amplified copies of the c‐Ha‐ras gene were detected in NIH 3T3 transformant cell lines, indicating that an activated Ha‐ras gene had been transferred to the NIH 3T3 recipient cells. Analysis of p21ras from the transformant cell lines suggested that the activating ras mutation was present in codon 61. Ultimately, the Ha‐ras gene was shown to be activated by a specific A → T transversion at the second position of codon 61. This mutation was detected in both benign papillomas and SCCs, suggesting the activation occurred early in tumor development. The results demonstrate a highly consistent activation of the Ha‐ras oncogene by a specific point mutation, suggesting a functional role for an activated ras gene in the initiation of mouse skin tumors by urethane.
Expression of c‐raf‐1 and A‐raf‐1 during regeneration of rat liver following surgical partial hepatectomy
Authors: Silverman Jeffrey A. , Zurlo Joanne , Watson Michael A. , Yager James D. 
Published: February 2007

AbstractThe major objective of this study was to investigate the expression of members of the raf family of protooncogenes during rat liver regeneration. The steady‐state level of expression of both c‐raf‐1 and A‐raf‐1 increased three‐ to fivefold 18–24 h following partial hepatectomy, and it returned to basal levels by 72 h. Expression of c‐myc and Ha‐ras mRNA was increased at 3 and 18–24 h, respectively, confirming previous reports. Increased steady‐state levels of c‐raf‐1, A‐raf‐1, and Ha‐ras mRNA were also detected in hepatocytes isolated from rat liver 24 h after partial hepatectomy. Thus, elevated expression of the raf genes closely correlated with that of Ha‐ras, beginning at 12 h and reaching maximal levels during the first peak of DNA synthesis following partial hepatectomy.
Interleukin‐1 alpha gene intron containing variable repeat region coding for the SP1 transcription factor recognition sequence is polymorphic
Authors: Haugen Aage , Mann Dean , Murray Christine , Weston Ainsley , Willey James C. 
Published: February 2007

AbstractInterleukin‐1 alpha (IL‐1α) is a cytokine produced by a number of cell types including macrophages, fibroblasts, keratinocytes, and mesangial cells. We were interested in identifying a DNA restriction fragment length polymorphism (RFLP) for the IL‐1α gene for use in studies of genetic alteration in various human cancers. Human genomic DNA from 32 unrelated individuals was digested with various restriction enzymes, alone and in combination, and subjected to Southern blot analysis. Hybridization to 32P‐labeled IL‐1α cDNA revealed an insertion deletion‐type polymorphic pattern. After digestion with Rsal, insertion‐deletion‐type polymorphic bands with sizes of 3.4 kb, 3.1 kb, and 2.8 kb and one invariant band of 0.8 kb were observed. These three alleles, designated A1, A2, and A3, had relative frequencies of 0.18, 0.06, and 0.78 with heterozygosity observed in 38% of the unrelated individuals studied. Evaluation of nine related individuals for this Rsal polymorphism was consistent with a Mendelian inheritance.Comparison of restriction patterns following Southern analysis of DNA digested with several different enzymes showed that the polymorphic region resides within the sixth intron. Furthermore, this RFLP results from a variable length region containing multiple copies of a recognition sequence for SP1, an imperfect copy of viral enhancer elements, and an inverse and complementary sequence of the glucocorticoid receptor binding site. The identified polymorphism may be of value in analyses of chromosome 2 and may help to elucidate mechanisms by which IL‐1α transcription is regulated.
Activation of the c‐Ha‐ras‐1 proto‐oncogene by methylation in vitro with α‐acetoxy‐N‐nitrosodimethylamine
Authors: Hirani‐Hojatti Samin , Milligan Jamie R. , Kovnat Asya , Brown Ken , Archer Michael C. 
Published: February 2007

Abstractα‐Acetoxy‐N‐nitrosodimethylamine, an activated derivative of the carcinogen N‐nitrosodimethylamine, methylated in vitro a plasmid containing the human c‐Ha‐ras‐1 proto‐oncogene, resulting in the generation of a transforming oncogene, assayed by transfection into NIH 3T3 cells. The resulting transformed cells were tumorigenic and metastatic in immune‐deprived mice. Further transfection using tumor DNA led to the formation of three secondary NIH 3T3 transformants. DNA from these secondary transformants contained human ras gene sequences. Two of the three secondary transformants contained G→A mutations at guanine 35 in codon 12, and the third secondary transformant retained the wild‐type sequence at codons 12 and 61. For the latter, the activating mutation was not determined. These results demonstrate that a simple methylating agent can activate a normal human ras proto‐oncogene to a transforming oncogene.
Potential role of the human Ha‐ras oncogene in the inhibition of gap junctional intercellular communication
Authors: El‐Fouly Mohamed H. , Trosko James E. , Chang Chia‐Cheng , Warren Stephen T. 
Published: February 2007

AbstractThe modulation of gap junctional intercellular communication (GJIC) plays an important role during tumor promotion. Several tumor‐promoting agents are known to inhibit this form of cellular coupling. In addition, tumor cells and cells expressing certain oncogenic products have been shown to exhibit inhibited or reduced GJIC. The Ha‐ras oncogene is expressed in a wide variety of human tumors from different tissues. Its p21 product is a membrane‐bound polypeptide, the function of which is not fully characterized. We tested the effects of the expression of the human c‐Ha‐ras‐1 oncogene, derived from the EJ/T4 bladder carcinoma cell line, on the ability of the Chinese hamster V79 cells to conduct gap Junctional communication. The Junctional competence was studied by two different methods, the scrape‐loading/dye transfer technique and the metabolic cooperation assay. The results indicate a strong correlation between the expression of p21 ras protein and the inhibition of gap Junctional function. Assuming that reversible inhibition of intercellular communication plays a role during tumor promotion and stable inhibition during the tumor progression phase of carcinogenesis, our data suggest that, while chemical tumor promoters and the ras oncogenes might work by different biochemical mechanisms, they both affect a critical cellular function; namely, GJIC.
Permanent conversion of mouse and human cells transformed by activated ras or raf genes to apparently normal cells by treatment with the antibiotic azatyrosine
Authors: Shindo‐Okada Nobuko , Makabe Osamu , Nagahara Hikaru , Nishimura Susumu 
Published: February 2007

AbstractAzatyrosine [L‐sβ‐(5‐hydroxy‐2‐pyridyl)‐alanine], an antibiotic isolated from Streptomyces chibanensis, inhibited the growth of NIH 3T3 cells transformed by the activated human c‐Ha‐ras gene but did not significantly inhibit the growth of normal NIH 3T3 cells. Surprisingly, upon treatment with azatyrosine most of the transformed cells apparently became normal. These apparently normal cells, named revertant cells, grew in the presence of azatyrosine and stopped growing when they reached confluency, and their normal phenotype persisted during prolonged culture in the absence of azatyrosine. The revertant cells did not grow in soft agar and scarcely proliferated in nude mice.The human c‐Ha‐ras gene present in transformed NIH 3T3 cells was still present in the revertant cells and was expressed to the same extent as in the original transformed cells, producing the same amount of activated p21.Treatment with azatyrosine caused similar conversion of NIH 3T3 cells transformed by activated c‐Ki‐ras, N‐ras, or c‐raf to apparently normal cells, but NIH 3T3 cells transformed by hst or ret were not exclusively converted by azatyrosine. Human pancreatic adenocarcinoma cells, which are known to contain an amplified activated c‐Ki‐ras gene and an amplified c‐myc gene, were also converted to flat and giant revertant cells by treatment with azatyrosine.