bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of serum growth factors and phorbol ester on growth and survival of human thyroid epithelial cells expressing mutant ras
Authors: Bond Jane , Dawson Tim , Lemoine Nick , Wynford‐Thomas David 
Published: February 2007

AbstractWe previously demonstrated a high incidence of ras mutation in thyroid follicular (epithelial) cell neoplasms and showed that expression of mutant ras is a potent mitogenic stimulus for normal human follicular cells in culture. Here we show that induction of cell proliferation in primary follicular cells by a mutant human Ha‐ras (val 12) expressed from a retroviral vector was absolutely dependent on the presence of serum growth factors. Induction of DNA synthesis showed partial dependence. Mutant ras‐induced growth was also inhibited by exposure to phorbol ester at concentrations sufficient to downregulate protein kinase C. More importantly, we observed an unexpected toxic effect of phorbol ester in this system that was specific to cells expressing mutant ras. This has potential significance both for elucidating the basic mechanism of ras action in epithelial cells and also as a pointer to a novel therapeutic strategy. © 1992 wiley‐list, Inc.
Isolation and partial characterization of murine O6‐alkyiguanine‐DNA‐alkyltransferase: Comparative sequence and structural properties
Authors: Santibanez‐Koref Mauro , Elder Rhoderick H. , Fan Chun‐Yang , Cawkwell Lynn , McKie James H. , Douglas Kenneth T. , Margison Geoffrey P. , Rafferty Joseph A. 
Published: February 2007

AbstractA cDNA encoding murine O6‐alkylguanine‐DNA‐alkyltransferase (ATase) has been sequenced after isolation from total liver RNA by the polymerase chain reaction using oligonucleotide primers derived from the rat ATase cDNA sequence. Functionally active murine ATase protein has been expressed in Escherichia coli at high levels (about 2% of total protein) and purified to apparent homogeneity (molecular mass 26 kDa). In liquid hybridization experiments, anti‐human ATase polyclonal antibodies inhibited human but not rat or mouse ATase, whereas anti‐rat polyclonal antibodies inhibited rat and mouse but not human ATase. Both antibodies detected all mammalian ATases tested by western analysis so far. These results indicate some common epitopes and at least one unique human epitope. We compared the amino‐acid sequence of the murine ATase with those of other mammalian and bacterial ATases. The proteins of this family all have a large domain (approximately 70 amino acids) of highly conserved residues flanking the sequence PCHRV, which contains the alkyl‐accepting cysteine residue of the active site. No evidence was found in the sequences for helix‐turn‐helix, leucine‐zipper, or zinc‐finger motifs for DNA recognition and binding. Nuclear localization signals (basic‐residue‐rich regions) could not be uniquely identified in the mammalian members of the family. Outside of the conserved PCHRV region, there were major differences between prokaryotic and eukaryotic proteins at the primary structure level: there was a series of proline‐rich motifs, but these also varied between sequences. © 1992 wiley‐Liss, Inc.
Effects of N‐Methyl‐N‐nitrosourea on transcriptionally active and inactive nucleosomes: Macromolecular damage and DNA repair
Authors: Boffa Lidia C. , Mariani Maria R. , Carpaneto Elisabetta M. 
Published: February 2007

AbstractWe previously reported a separation, on an organomercurial column, of transcriptionally inactive nucleosomes (class 1) from those containing active gene sequences (classes 2 and 3). In this paper, we analyzed nucleosomal damage caused by exposure of HeLa S3 cells in suspension culture to the directly alkylating carcinogen N‐methyl‐N‐nitrosourea (MNU). The extent and site of methylation induced by the compound in nucleosomal DNA and RNA were determined by cell incubation in the presence of [3H]MNU. The highest amount of damage was detected in DNA of class 3 nucleosomes, while RNA alkylation was comparable in all nucleosomal classes. Cellular capacity for repair of MNU‐induced DNA strand breaks (estimated after a short pulse with [3H]thymidine) was found to be higher in active nucleosomal fractions (classes 2 and 3) than in the inactive fraction (class 1). Our data support the postulate that chromatin primary structure plays a role in modulating carcinogen damage to chromosomal macromolecules and in DNA strand breakage and repair mechanisms. Some of these initial steps are believed to be critical in the process of carcinogenesis. © 1992 Wiley‐Liss, Inc.
Genetic linkage between copper accumulation and hepatitis/hepatoma development in LEC rats
Authors: Sone Hideko , Maeda Mitsuaki , Gotoh Masahiro , Wakabayashi Keiji , Ono Takao , Yoshida Michihiro C. , Takeichi Noritoshi , Mori Michio , Hirohashi Setsuo , Sugimura Takashi , Nagao Minako 
Published: February 2007

AbstractThe concentration of copper in the livers of Long‐Evans rats with cinnamon‐like coat color (LEC), in which hepatitis and then hepatomas develop spontaneously, was recently found to be abnormally high. Therefore, we examined the copper concentrations in the livers of LEC F1 backcrosses (LEC F1 × LEC) to determine the linkage of copper accumulation with development of hepatitis. Consistent with a previously reported ratio of rats with hepatitis to rats without hepatitis of about 1:1, hepatitis developed in 14 of 30 F1 backcrosses. The copper concentrations in the livers of all LEC F1 backcrosses with hepatitis were abnormally high and comparable to those of LEC rats. In contrast, the concentrations in all backcrosses without hepatitis were similar to those in normal Long‐Evans with agouti coat color or Brown‐Norway rats. Copper accumulation was shown to be closely linked with the development of hepatitis in LEC rats and appeared to be a possible cause of hepatitis. The concentrations of copper in the livers of Fischer 344 rats after carbon tetrachloride treatment were in the range for normal liver, indicating that a high copper concentration in the liver is specific to LEC rats and not a specific characteristic of hepatitis. Furthermore, we found that the size and level of ceruloplasmin mRNA in the livers of LEC rats were the same as those in LEA rats and that the size and level of ceruloplasmin polypeptide in their livers and plasma were almost the same as those in LEA rats. Therefore, these results suggest that the copper accumulation is not due to alteration of expression or to gross alteration of the ceruloplasmin gene. © 1992 Wiley‐Liss, Inc.
Elevated expression of the ribosomal protein S2 gene in human tumors
Authors: Chiao Paul J. , Shin Dong M. , Sacks Peter G. , Hong Waun K. , Tainsky Michael A. 
Published: February 2007

AbstractDifferential screening of a cDNA library was used to isolate genes differentially expressed in a nontumorigenic clone and a ras‐transformed variant of the human teratocarcinoma cell line PA‐1. The RNA transcript for one of the cDNA clones that we identified was expressed at a 25‐fold higher level in the ras‐transformed PA‐1 cells than in the nontumorigenic PA‐1 cells. DNA sequence analysis of this clone showed that it had 86% nucleic acid homology to the mouse LLRep3 gene and only differed at a single amino acid codon (codon 198), which is changed from serine in LLRep3 to threonine in this cDNA clone. The rat ribosomal S2 protein is closely related to the yeast omnipotent informational suppressor SUP44, which encodes the yeast ribosomal protein 54; to the mouse protein LLRep3; and to the human cDNA clone we describe in this report. We therefore concluded that this clone codes for the human ribosomal S2 protein. In situ hybridization experiments revealed that expression of this gene was elevated in cultured human head and neck squamous cell carcinomas compared with normal keratinocytes. In situ hybridization experiments also demonstrated that expression of this gene was elevated in histological sections of human premalignant leukoplakia, head and neck squamous cell carcinomas, and colon and breast cancers compared with the adjacent normal tissues. S2 expression may be a useful diagnostic or prognostic marker for grading human tumors. © 1992 Wiley‐Liss, Inc.
p53 gene mutations in human endometrial carcinoma
Authors: Risinger John I. , Dent Georgette A. , Ignar‐Trowbridge Diane , McLachlan John A. , Tsao Ming‐Sound , Senterman Mary , Boyd Jeff 
Published: February 2007

AbstractAlthough carcinoma of the uterine endometrium is the most frequently diagnosed malignancy of the female reproductive tract, the molecular genetic features of this tumor have yet to be described in significant detail. Since mutations of the p53 tumor suppressor gene are the single most common genetic alteration found in human malignancies, we examined the hypothesis that p53 mutations occur in human endometrial carcinoma. Sequencing analysis of exons 5–8 revealed point mutations in 3 of 21 (14%) tumors; one mutation was an unusual single‐base insertion at codons 176–177, resulting in a premature stop codon, whereas the other two were CGG→TGG transitions at codon 248. Two of these tumors showed reduction to homozygosity at the p53 allele, but one tumor apparently retained heterozygosity. These data indicate that p53 mutations occur in human endometrial carcinoma, although relatively infrequently, and that loss of the normal p53 allele does not necessarily occur with point mutation of the p53 gene in this tumor type. © 1992 Wiley‐Liss, Inc.
Activating mutation of the Ha‐ras gene in chemically induced tumors of the hamster cheek pouch
Authors: Gimenez‐Conti Irma B. , Bianchi Albert B. , Stockman Sharon L. , Conti Claudio J. , Slaga Thomas J. 
Published: February 2007

AbstractThe presence of an activating mutation in the Ha‐ras gene in hamster cheek pouch tumors induced by 7,12‐dimethylbenz[a]anthracene (DMBA) complete carcinogenesis was investigated. The normal sequence of a fragment of genomic DNA encompassing codon 61 of the Ha‐ras gene was amplified by the polymerase chain reaction using primers designed for a highly conserved region of the mouse Ha‐ras‐1 gene. The sequence of the amplified fragment was determined by a direct sequencing technique and exhibited 83.3% and 87.5% homology with the corresponding human and mouse sequences, respectively. At the amino acid level, the sequence was identical among the three species. Paraffin sections of 11 squamous cell carcinomas of the cheek pouch were used to detect mutated Ha‐ras alleles. DNA sequencing of the tumors showed that six of 11 tumors presented an A→T transversion in the second position of codon 61, resulting in an amino acid change from glycine to leucine. As has been demonstrated in other systems, we have shown a specific mutation of the Ha‐ras gene in chemically induced tumors of the hamster cheek pouch, further supporting the role of this oncogene in chemical carcinogenesis. © 1992 Wiley‐Liss, Inc.
Differential retention of tumor‐ and differentiation‐suppressor functions in cells derived from a human squamous cell carcinoma
Authors: Jaffe Deborah R. , Montero‐Puerner Yvonne , Beckett Michael A. , Cowan Janet M. , Weichselbaum Ralph R. , Diamond Alan M. 
Published: February 2007

AbstractThree morphologically distinct cell lines—F.2a, V, and B.2—were isolated from a single human squamous cell carcinoma. Although all three cell lines can grow indefinitely in culture, they differ in a number of important transformation‐related phenotypes. Only B.2 is strongly tumorigenic when injected into the flanks of nude mice, and only V can efficiently grow in semisolid media. The dominance of these traits was investigated by generating somatic cell hybrids among the three cell lines. F.2a was able to suppress the tumorigenicity of B.2 cells, whereas B.2 inhibited the capacity for anchorage‐independent growth of V, the latter trait being a function of the ability of these epithelial cells to differentiate when deprived of support. The influence of exogenously added growth factors was also evaluated. This study indicates that the particular tumor we examined consisted of a heterogeneous population of cells with distinct growth and differentiation capacities. © 1992 Wiley‐Liss, Inc.
Differential effect of tumor necrosis factor on proliferation of primary human keratinocytes and cell lines containing human papillomavirus types 16 and 18
Authors: Villa Luisa Lina , Vieira Katia Brito Lins , Pei Xu‐Fang , Schlegel Richard 
Published: February 2007

AbstractKeratinocytes immortalized by human papillomaviruses (HPV) 16 and 18 are partially resistant to the inhibition of proliferation exerted by transforming growth factor‐β (TGF‐β). To determine if this finding reflects a generalized resistance to inhibitory cytokines, we studied the effect of tumor necrosis factor‐α (TNF‐α) on subconfluent cultures of both normal and HPV‐immortalized human foreskin keratinocytes. Whereas primary and HPV‐16‐immortalized keratinocytes were sensitive to TNF‐α, HPV‐18‐immortalized keratinocytes (and those immortalized by simian virus 40) were resistant to the inhibitory effects of this cytokine. The ability of HPV‐18 to induce a more resistant phenotype correlated with its more potent in vitro transforming activity and its apparent association with more aggressive tumors. Interestingly, the state of TNF‐induced growth inhibition in normal or HPV‐16—immortalized keratinocytes was not accompanied by a reduction in the expression of c‐myc RNA or protein. This contrasts sharply with the ability of TGF‐β to inhibit c‐myc RNA expression in normal cells. Evidently, the resistance of HPV‐immortalized keratinocytes to TNF‐β and TGF‐β proceeds along different regulatory pathways. © 1992 Wiley‐Liss, Inc.
Activation of the Ki‐ras gene in spontaneous and chemically induced lung tumors in CD‐1 mice
Authors: Manam Sujata , Storer Richard D. , Prahalada Srinivasa , Leander Karen R. , Kraynak Andrew R. , Hammermeister Christine L. , Joslyn Dennis J. , Ledwith Brian J. , Van Zwieten Matthew J. , Bradley Matthews O. , Nichols Warren W. 
Published: February 2007

AbstractAs part of an evaluation of the effectiveness of using ras mutation analysis for distinguishing carcinogen‐induced from spontaneous tumors, we examined the profile of ras gene point mutations in spontaneous, 7,12‐dimethylbenz[a]anthracene (DMBA)‐induced, and N‐nitrosodiethylamine (DEN)‐induced lung tumors from Crl:CD‐1(ICR)BR (CD‐1) mice. Although all of the lung tumors were assayed for mutations in the Ha‐ras, Ki‐ras, and N‐ras genes (codons 12, 13, and 61), only Ki‐ras mutations were found, which is consistent with other studies that have noted a strong preference for Ki‐ras gene activation in mouse, rat, and human lung tumors. We found that spontaneous CD‐1 mouse lung tumors had a very high frequency of Ki‐ras gene activation (17 of 20 tumors; 85%), distributed among codons 12 (5 of 20), 13 (1 of 20), and 61(11 of 20). DMBA‐induced lung tumors had a slightly higher frequency of Ki‐ras gene mutations (16 of 16; 100%), again distributed among codons 12(5 of 16), 13 (2 of 16), and 61(9 of 16). However, seven of the DMBA tumors had mutations qualitatively different from those found in spontaneous tumors. In contrast to DMBA‐induced tumors, DEN‐induced tumors had a lower frequency of Ki‐ras mutations (36%) when compared with spontaneous lung tumors, suggesting that DEN primarily induces lung carcinogenesis by a mechanism other than ras gene activation. Thus, although spontaneous and induced CD‐1 mouse lung tumors have a strong tissue‐specific preference for carrying an activated Ki‐ras gene, the nature of the initiating carcinogen can influence the frequency or profile of Ki‐ras mutations. © 1992 wiley‐Liss, inc.
Regulation of growth and gene expression in human papillomavirus‐transformed keratinocytes by transforming growth factor‐β: Implications for the control of papillomavirus infection
Authors: Braun Lundy , Dürst Matthias , Mikumo Ryoko , Crowley Annette , Robinson Mava 
Published: February 2007

AbstractCervical carcinogenesis is a multistep process that appears to be initiated by infection of squamous epithelial cells in the cervix with one of a limited number of human papillomavirus (HPV) types. However, the mechanisms involved in the evolution of benign, HPV‐induced lesions to malignancy have not yet been fully elucidated. Transforming growth factor‐β (TGF‐β), a multifunctional growth factor produced by cells in the skin, inhibits the proliferation of foreskin and cervical keratinocytes in vitro. We examined the effects of TGF‐β on growth and virus early‐gene expression in cell lines immortalized by two HPV types associated with cervical carcinogenesis as well as the expression of TGF‐β1 mRNA transcripts in normal and HPV‐positive cells in vivo and in vitro. We found that normal and HPV‐positive cells expressed similar levels of TGF‐β1 mRNAs and exhibited similar patterns of responsiveness to three isoforms of TGF‐β in both monolayer and modified organotypic cultures. Of particular interest is our finding that the expression of the E6 and E7 early viral transforming regions of both HPV16 and HPV18 was reversibly and rapidly inhibited by TGF‐β. In one HPV16‐positive cell line examined in detail, inhibition of HPV expression required protein synthesis and occurred at the level of transcription. HPV‐immortalized cells selected for resistance to in vitro differentiation signals remained sensitive to TGF‐β‐mediated growth inhibition. These results, showing that both growth and virus gene expression in HPV‐transformed cells were responsive to TGF‐β, suggest that endogenous growth factors produced by different cell types in squamous epithelium may play a role in the progression of cervical neoplasia. © 1992 Wiley‐Liss, Inc.
Aberrant expression of the simple epithelial type II keratin 8 by mouse skin carcinomas but not papillomas
Authors: Larcher Fernando , Bauluz Cristina , Diaz‐Guerra Margarita , Quintanilla Miguel , Conti Claudio J. , Ballestin Claudio , Jorcano José L. 
Published: February 2007

AbstractKeratins have been demonstrated to be suitable markers of changes taking place during epithelial neoplasia. Therefore, we analyzed 18 mouse skin tumors (nine papillomas and nine squamous cell carcinomas), induced either by two‐stage carcinogenesis with 7,12‐dimethylbenz[a]anthracene(DMBA)/12‐O‐tetradecanoylphorbol‐13‐acetate or complete carcinogenesis with DMBA, by immunofluorescence with a monoclonal antibody to keratin (K) 8 (TROMA‐1). Immunoperoxidase staining and immunoblotting were also used on selected tumor samples to further explore for the presence of K8. All of the papillomas tested were negative for the presence of K8, whereas the carcinomas were positive. The level of K8 expression in carcinomas showed a positive correlation with the degree of malignancy. Northern blot analysis using a K8 cDNA probe suggested that control of K8 expression in mouse skin tumors occurs at the transcriptional level. Double‐label immunofluorescence staining using TROMA‐1 and RK13 antibodies demonstrated that K8 did not generally colocalize with K13, a keratin normally found in internal stratified epithelia but aberrantly expressed in mouse epidermal tumors. Furthermore, tumors expressing high levels of K8 showed a reduced expression of K13. Histological examination of immunoperoxidase‐stained tumors demonstrated that K8‐positive cells were mainly found in anaplastic areas, whereas K13 foci were restricted to well‐differentiated regions. Our results demonstrate that K8 expression is a marker of late stages of carcinoma progression in the mouse skin carcinogenesis model. © 1992 Wiley‐Liss, Inc.
Stepwise transformation of primary thyroid epithelial cells by a mutant Ha‐ras oncogene: An in vitro model of tumor progression
Authors: Burns Jorge S. , Blaydes Jeremy P. , Wright Pat A. , Lemoine Louise , Bond Jane A. , Dillwyn Williams E. , Wynford‐Thomas D. 
Published: February 2007

AbstractActivating mutations of the ras oncogene family occur at high frequency in all stages of thyroid tumorigenesis, both human and experimental. To test the causal nature of this association, and to investigate the biological role of ras mutation, we introduced a mutant c‐Ha‐ras gene into normal rat thyroid follicular cells using an ecotropic retroviral vector. The major immediate effect was to greatly extend the proliferative lifespan of these cells in culture from less than 3 to more than 15 doublings, without any observable loss of growth‐factor dependence or differentiated functions. This in vitro phenotype strongly supports an initiating role for ras mutation in the genesis of benign thyroid tumors (adenomas) in vivo. Spontaneous transformation was observed at low frequency on continuous culture of mutant ras‐expressing cells, giving rise to fully immortalized, growth factor‐independent, highly tumorigenic lines. Transformation was associated with (i) loss of responsiveness to the growth inhibitor TGF‐β1, and (ii) greatly increased nuclear levels of p53 protein, which unexpectedly was not due to point mutation in the conserved regions of the p53‐coding sequence. We postulate that these two phenomena are causally related to each other and to the transformed phenotype. © 1992 Wiley‐Liss, Inc.
Mutational analysis of a dominant oncogene (c‐Ki‐ras‐2) and a tumor suppressor gene (p53) in hamster lung tumorigenesis
Authors: Oreffo Victor I. C. , Lin Hsiu‐Wei , Gumerlock Paul H. , Kraegel Susan A. , Witschi Hanspeter 
Published: February 2007

AbstractIn human lung cancers, alterations of both a dominant oncogene (ras) and a tumor suppressor gene (p53) have been identified. Polymerase chain reaction (PCR) analysis of mRNA was used to amplify the c‐Ki‐ras‐2 andp53genes from Syrian golden hamsters. The PCR products were confirmed by predicted‐size analysis, probing with nonradioactive (biotin‐labeled) oligonucleotides, and direct sequencing. Lung tumors were produced in hamsters by repeated injections of 4‐(methylnitrosamino)‐1‐(3‐pyridyl)‐1‐butanone (NNK). Of six tumors examined, three (50%) had mutations in codon 12 of Ki‐ras. Examination of the conserved regions ofp53revealed no mutations. We conclude that NNK‐induced carcinogenesis in the hamster results in characteristic alterations of Ki‐rasbut may not necessarily involve thep53gene. © 1992 Wiley‐Liss, Inc.
Sequence analysis of the int‐2/fgf‐3 gene in aggressive human breast carcinomas
Authors: Meyers Shari L. , Dudley Jaquelin P. 
Published: February 2007

AbstractA number of primary human breast carcinomas exhibit amplification of the chromosome 11 region containing the int‐2/fgf‐3 proto‐oncogene, and progression of breast cancer has been correlated with int‐2 amplification or with certain restriction fragment length polymorphisms (RFLPs) of the int‐2 gene. Using the polymerase chain reaction (PCR), we obtained the int‐2 coding sequences from six primary tumors, four of which exhibited amplification of the int‐2 gene and one of which exhibited amplification of the neu gene. The majority of these tumors (five of six) were aggressive, as judged by their early recurrence, metastasis, or both. Nucleotide sequencing of PCR products revealed that previously described BamHl and Pstl RFLPs of the int‐2 gene, as well as a new polymorphism at position 9154, were located within the intron between the second and third exons. A seventh tumor was used to localize one of the Pstl RFLPs 5 bp from the splice‐acceptor site of the third exon. However, none of the tumor DNAs analyzed showed differences in the int‐2 protein coding regions when compared with normal placenta DNA. These results imply that aggressive human breast cancers encode an unaltered form of the int‐2 protein. © 1992 Wiley‐Liss, Inc.