bluuebunny/crossref_metadata_2025_split huggingface dataset:
Alternative splicing of neurofibromatosis type 1 gene transcript in malignant brain tumors: PCR analysis of frozen‐section mRNA
Authors: Mochizuki Hiroshi , Nishi Toru , Bruner Janet M. , Lee Polly S. Y. , Levin Victor A. , Saya Hideyuki 
Published: February 2007

AbstractThe neurofibromatosis type 1 (NF1) gene encodes a 360‐residue region showing significant homology to the catalytic domains of both mammalian GTPase‐activating protein (GAP) and yeast IRA protein. The product of the GAP‐related domain of the NF1 gene (NF1‐GRD) has been shown to stimulate ras GTPase and consequently to inactivate ras protein. We previously reported that the NF1‐GRD has two types of transcripts, type I and type II, which are generated by an alternative splicing mechanism, and that the differential splicing of the NF1‐GRD may be related to differentiation of neuroectodermal cells. Here we examined the differential expression of type I and type II transcripts of NF1‐GRD in clinical samples of supratentorial malignant brain tumors by the RNA‐polymerase chain reaction (PCR) method using frozen tissue sections. Our observations revealed that normal cerebrum predominantly expressed the type II NF1‐GRD transcript, whereas primitive neuroectodermal tumors predominantly expressed the type I transcript. Additionally, although the type I/type II ratio in astrocytomas varied widely among tissue samples, all glioblastomas showed higher type I/type II ratios than adjacent brain samples. The RNA‐PCR analysis using frozen tissue sections is a useful and sensitive method for detecting genetic markers in clinical tissue samples. © 1992 Wiley‐Liss, Inc.
Molecular cloning, analysis, and chromosomal localization of a mouse genomic sequence related to the human papillomavirus type 18 E5 region
Authors: Kahn Tomas , Friesl Holger , Copeland Neal G. , Gilbert Debra J. , Jenkins Nancy A. , Gissmann Lutz , Kramer Judith , Hausen Harald Zur 
Published: February 2007

AbstractThe E5 open reading frame (ORF) from bovine papillomavirus type 1 (BPV 1) as well as the E5 ORFs from human papillomaviruses (HPV) type 6 and type 16 have been reported to transform immortalized rodent cells. In an analysis of murine and human tumors for the presence of putative papillomavirus‐related sequences, we cloned amplified cellular sequences from the mouse cell line Eb that cross‐hybridized with the E5 ORF of HPV 18. A 2.1‐kb fragment termed HC1 was sequenced. In normal murine cells, it was present as a single‐copy genomic sequence located on chromosome 8. A region of 213 nucleotides corresponded to the E5 gene (HC1 E5), based on the best alignments and on the presence of direct and inverted repeats bearing a central sequence motif. These structural elements are also present in the HPV 18 E5 ORF. HC1 E5 contained an ORF that was transcribed bidirectionally. The transcription in the E5 direction was enhanced in RNA obtained from organs and tumors from carcinogen‐treated animals and C127 cells. The polypeptide deduced from the sequence was related to E5 proteins from genital papillomaviruses, to the putative product of the Q300 mouse gene, and to several viral and human growth factors. The data suggest that there may be several cellular counterparts to the viral E5 proteins. © 1992 Wiley‐Liss, Inc.
Kinds of mutations induced by aflatoxin B1 in a shuttle vector replicating in human cells transiently expressing cytochrome P450IA2 cDNA
Authors: Trottier Yvon , Waithe William I. , Anderson Alan 
Published: February 2007

AbstractTransient expression of rat liver cytochrome P450IA2 cDNA was combined with the use of a shuttle vector as a mutational target to determine the frequency and types of mutation caused by the conversion of aflatoxin B, into genotoxic metabolites within human cells. Ad293 cells were first transfected with p91‐IA2, a rat liver P450lA2 cDNA expression vector, or with p91‐lA2(i) (a control vector that has the P450 cDNA in the inverted orientation) and incubated for 24 h to permit P450IA2 accumulation. Cells were then transfected with the pS189 shuttlevector plasmid, which carries the Escherichia coli supF gene as a mutational target, and incubated for a further 24 h in the presence of aflatoxin B, to permit promutagen activation and pS189 replication. In shuttle vectors replicated in p91‐lA2–transfected cells, the supF point‐mutation frequency increased with increasing concentration of aflatoxin β1. This frequency was nine to 23 times greater than the background point‐mutation frequency obtained with aflatoxin B1‐treated control (p91‐IA2(i)‐transfected) cells. The large majority of the aflatoxin B1–induced supF point mutations were base substitutions, mostly G:C ± T:A transversions. This mutagenesis system permits the molecular analysis of mutations induced by specific P450/promutagen pairs in a shuttle vector replicating in human cells and will permit the investigation of host cell mechanisms involved in the generation of these mutations. © 1992 wiley‐Liss, Inc.
Alterations in the structural gene and the expression of p53 in rat liver tumors induced by aflatoxin B1
Authors: Lilleberg Stan L. , Cabonce Marc A. , Raju Narayan R. , Wagner Lynne M. , Kier Larry D. 
Published: February 2007

AbstractRat hepatocellular carcinomas (HCCs) induced by aflatoxin B1 (AFB) treatment were examined for changes in the p53 tumor suppressor gene and in p53 suppressor gene expression. A high proportion of HCCs (nine of 11 tumors in six of eight animals) exhibited new p53 restriction fragments, indicating genomic alterations of one of the p53 alleles. Each tumor with an altered p53 restriction‐fragment pattern exhibited a new fragment in one of two size classes (3 kb or 7 kb with EcoRl digestion) that were missing portions of the 3' end of the p53 gene. These findings indicate that apparently similar genomic rearrangements or deletions occurred independently in AFB‐induced tumors. When compared with nontumor liver tissue from the same animal, the tumors with p53 gene alterations showed dramatically reduced levels of p53 mRNA and protein and greatly increased levels of histone H2B and retinoblastoma tumor suppressor (Rb) mRNA. In two HCCs showing no evidence of p53 restriction‐fragment alterations, mutant p53 protein was detected. Mutant protein was also detected in two liver samples containing an adenoma and altered foci. These data suggest that alterations of the p53 tumor suppressor gene are involved in the induction of rat HCC by AFB. © 1992 Wiley‐Liss, Inc.
Cellular pattern of multidrug‐resistance gene expression during chemical hepatocarcinogenesis in the rat
Authors: Nakatsukasa Harushige , Evarts Ritva P. , Burt Richard K. , Nagy Peter , Thorgeirsson Snorri S. 
Published: February 2007

AbstractIncreased expression of multidrug‐resistance (mdr) gene transcripts and of the encoded protein, P‐glycoprotein, is found in many types of tumors. The biological significance of mdr overexpression during the stepwise process of neoplastic development, however, is not well understood. To assess the possible significance of mdr overexpression in carcinogenesis, we examined the cellular distributions of both mdr gene transcripts and P‐glycoprotein during hepatocarcinogenesis induced in rats by the Solt‐Farber protocol and then compared them to the distributions of the placental form of glutathione S‐transferase (GST‐P), a known marker of preneoplastic and neoplastic lesions in the liver. In situ hybridization and immunohistochemical techniques were employed. Neither mdr transcripts nor P‐glycoprotein was expressed in oval cells that appeared early in the carcinogenic process. GST‐P was strongly expressed in the early focal lesions, whereas the levels of mdr transcripts and P‐glycoprotein expressed were low and heterogeneous. Expression of mdr transcripts and P‐glycoprotein was increased and became more uniform in hyperplastic nodules and carcinomas, although considerable heterogeneity of expression was still found, particularly at the nodular stage. These data suggest that increased expression of mdr is associated with later stages of neoplastic development in the liver. Furthermore, that no chemical treatment of the animals was employed when the expression of mdr was increasing in the preneoplastic and neoplastic lesions suggests that the enhanced mdr expression is intrinsic to the carcinogenic process. © 1992 Wiley‐Liss, Inc.
Differential susceptibility to carcinogen‐induced amplification of sv40 and dhfr sequences in sv40‐transformed human keratinocytes
Authors: Rossman Toby G. , Wolosin Dora 
Published: February 2007

AbstractGene amplification contributes to carcinogenesis by enhancing proto‐oncogene activity and causing chromosomal instability. The ease of detecting amplified tumor‐virus sequences has encouraged use of this system as a surrogate for studying the molecular events involved in endogenous gene amplification. We report here a new system for studying carcinogen‐induced amplification of both endogenous and viral sequences in the SV40‐transformed human keratinocyte line AG06. Treatment with carcinogens induced a transient dose‐dependent amplification of the integrated SV40 sequences. The amplified sequences appeared in the extra‐chromosomal fraction. Treatment of these cells with carcinogens prior to methotrexate (MTX) selection increased the frequency of MTX‐resistant colonies, 67% of which exhibited dihydrofolate reductase (dhfr) amplification. The abilities of five carcinogens with different DNA‐damaging activities (the DNA‐damaging agents N‐methyl‐N‐nitro‐N‐nitrosoguanidine, mitomycin C (MMC), ultraviolet light C, and X‐rays and the non‐DNA‐damaging agent arsenite) to induce SV40 and dhfr amplification at concentrations that result in 50% clonal survival were compared. All four DNA‐damaging carcinogens (as well as growth arrest) were able to elicit some SV40 amplification, but responses varied markedly, from 1.8‐fold for X‐rays to sevenfold to eightfold for MMC. There was no correlation between the ability to elicit the two amplification responses. Arsenite, which did not induce SV40 amplification, was the best inducer of MTX resistance. These results point to different controls involved in the induction of viral and dhfr amplification. The signal for amplification of viral genes may be triggered by DNA damage and growth arrest, whereas amplification of dhfr, and perhaps other endogenous sequences, seems to be triggered by other signals as well. © 1992 Wiley‐Liss, Inc.
Mutational specificities of n‐nitrosamines in a host‐mediated assay: comparison with direct‐acting n‐nitroso compounds in vitro and an approach to deducing the nature of ultimate mutagens in vivo
Authors: Liu Yu‐Xin , Guttenplan Joseph B. 
Published: February 2007

AbstractThe mutational activities and specificities of several N‐nitrosamines in Salmonella recovered from mouse liver in the host‐mediated assay (HMA) were compared with the specificities of related direct‐acting N‐nitroso compounds in vitro. The specificities of the direct‐acting methyl, ethyl, propyl, and 2‐hydroxypropyl compounds were all different and presumably are attributable to the DNA adducts resulting from the corresponding alkyldiazonium or carbonium ions. Introduction of a 2‐hydroxyl group greatly influenced the mutational specificity. The 2‐oxopropyl compound showed the same specificity as the methyl compound. This result is consistent with one of the known breakdown pathways of the oxopropyl diazonium ion (or related reactive species), which leads to a methyl diazonium ion. The N‐nitrosodialkylnitrosamines N‐nitrosodimethylamine (NDMA), N‐nitrosodiethylamine (NDEA), and N‐nitrosodipropylamine (NDPA), which all require metabolic activation, showed specificities in the HMA similar to those of their direct‐acting counterparts. The cyclic nitrosamine N‐nitro‐sopyrrolidine was weakly active in the HMA, although its direct‐acting derivative was a potent mutagen in vitro. The results for NDMA and NDEA were consistent with most previous studies of the metabolism of these compounds in vivo. However, NDPA can yield methylating, and probably hydroxypropylating, species in addition to propyldiazonium ion. As the specificity of NDPA was similar to that of a propylating agent, NDPA appears to lead to genotoxic products in the mouse liver mainly by direct α‐hydroxylation. The initial results described here indicate that mutational specificity in the HMA can be used to deduce metabolic pathways leading to genotoxic products when the appropriate proximate mutagens are available as standards. Furthermore, we observed a reasonable correlation between potency in the HMA and hepatocarcinogenesis. © 1992 Wiley‐Liss, Inc.
Partial suppression of tumorigenicity in a human lung cancer cell line transfected with Krev‐1
Authors: Caamano Jorge , Dirado Marion , Lizasa Toshihiko , Momiki Shigeru , Fernandes Elma , Ashendel Curt , Noda Makoto , Klein‐Szanto Andres J. P. 
Published: February 2007

AbstractA human non‐small‐cell lung carcinoma cell line, Calu‐6 (from an anaplastic carcinoma), was transfected with the Ki‐ras‐related anti‐oncogene Krev‐1. Several transfectant lines were obtained that showed a reduced tumorigenicity in nude mice with respect to the parental and control transfected cell lines. This decrease was approximately 50% in tumor incidence at 4 wk after subcutaneous inoculation of the transfected cells. In addition, the volume of the Calu‐6 revertant‐derived tumors was three to 10 times smaller than that of the equivalent tumors produced by inoculation of the control cell line transfected with the neomycin‐resistance gene. Krev‐1‐transfected cells that exhibited reduced tumorigenicity expressed Krev‐1 mRNA and had variable numbers of copies of the Krev‐1 gene. Moreover, Krev‐1 ‐transfected cells exhibited a more differentiated squamous epithelial morphology than the parental and control cell lines did. Moderately elevated levels of protein kinase C activity were detected in some revertant clones. Such activity correlated with the level of expression of Krev‐1 mRNA in most cases. In summary, Krev‐1 induced important morphological and biological changes in transfected Calu‐6 cells that we interpreted as partial reversion of the malignant phenotype. © 1992 Wiley‐Liss, Inc.
Growth and transformation suppressor genes for BHK syrian hamster cells on human chromosomes 1 and 11
Authors: Annab Lois A. , Dong Jin‐Tang , Futreal P. Andrew , Satoh Hitoshi , Oshimura Mitsuo , Barrett J. Carl 
Published: February 2007

AbstractTo map putative tumor suppressor genes for the near‐diploid baby hamster kidney fibrosarcoma cell line BHK, we transferred five different normal human chromosomes (1, 3, 7, 11, and 12) into these tumor cells by microcell‐mediated chromosome transfer. Transfer of human chromosome 1 into BHK cells resulted in suppression of cell growth both on plastic and in soft agar, indicating that chromosome 1 has a generalized effect on cell growth and thereby suppresses anchorage‐independent growth. Selection against cells with an intact chromosome 1 was observed. In contrast, the introduction of chromosome 11 into BHK cells resulted in suppression of anchorage independence but not growth on plastic. Most chromosome‐11 growth‐suppressed BHK hybrids retained intact copies of human chromosome 11. Tumorigenic derivatives of chromosome 11 hybrids had lost this chromosome. Transfer of human chromosome 3, 7, or 12 into BHK cells did not correlate with growth suppression of BHK cells on plastic or in soft agar. Thus, we conclude that genes that suppress BHK‐cell growth in general or in agar reside on human chromosomes 1 and 11, respectively. © 1992 Wiley‐Liss. Inc.
Lack of mutations of the p53 tumor suppressor gene in hepatocellular carcinomas induced in rats by a peroxisome proliferator
Authors: Smith Martin L. , Yeleswarapu Lakshmi , Lombardi Benito , Shinozuka Hisashi 
Published: February 2007

AbstractImmunohistochemical, immunoblotting, and DNA‐sequencing analyses were performed on hepatocellular carcinomas induced in rats chronically fed BR931, a peroxisome proliferator, to determine whether the tumors carried mutations or other alterations of the p53 gene. None were detected. Inactivation of this tumor suppressor gene does not appear, therefore, to be involved in the carcinogenicity of BR931, a nongenotoxic chemical hepatocarcinogen.
Low frequency of codon 61 Ha‐ras mutations and lack of keratin 13 expression in 7,12‐dimethylbenz[a]‐anthracene—induced hamster skin tumors
Authors: Robles Ana I. , Gimenez‐Conti Irma B. , Roop Dennis , Slaga Thomas J. , Conti Claudio J. 
Published: February 2007

AbstractAlterations in the pattern of keratin expression are a common feature of skin‐tumor development. In this study, we investigated whether the loss of epidermal keratin 1 (K1) and its replacement by mucosal keratin 13 (K 13) is unique to mouse skin tumors induced by 7,12‐dimethylbenz[a]anthracene (DMBA) and 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA), since it has been reported that human epidermal tumors do not exhibit aberrant expression of K13. With that purpose, we analyzed the keratin profiles of 16 DMBA‐induced hamster skin tumors using monospecific antibodies against K1 and K13. Although all the tumors expressed K1, they also showed an overall tendency towards loss of this keratin; furthermore, none of the tumors expressed K13. Previous studies have suggested that the induction of K13 in mouse skin is related to the mutation of the Ha‐ras gene by the initiating agent DMBA, a mutation consistently found in murine DMBA/TPA‐induced tumors and rarely found in human skin tumors. Therefore, we also evaluated the tumors for the presence of codon‐61 mutations by direct sequencing of DNA extracted from paraffin‐embedded tissue sections. Only three tumors showed an A→T transversion in the second nucleotide of Ha‐ras codon 61. However, presence of the mutation did not correlate with K1 staining. Although hamster skin tumors were induced by the same initiator as were mouse skin tumors, hamster skin tumors did not show the same keratin profile. Moreover, their immunohistochemical expression of K1 and K13 and their codon 61 sequences resembled that of their human counterparts. These results suggest that the aberrant expression of K13 may be unique to murine skin. Furthermore, although codon 61 Ha‐ras mutation appears to be related to keratin alterations in the mouse model, this mutation is not sufficient to produce the same biochemical changes in other species.
Application of denaturing gradient gel blots to detect p53 mutations in X‐ray—transformed mouse C3H 10T1/2 clones
Authors: Krolewski Bozena , Little John B. 
Published: February 2007

AbstractThe denaturing‐gradient gel electrophoresis (DGGE) blot technique is a highly sensitive method developed to detect sequence differences (e.g., single base changes and small deletions) in genomic DNA. We used this method to screen for mutations within the p53 locus of independent X‐ray—transformed C3H 10T1/2 cell clones. Genomic DNA from 29 transformed clones was digested with Haell and Hinfl endonucleases, electrophoresed on denaturing gradient gels, electroblotted onto nylon membranes, and hybridized to a radioactive p53 cDNA probe. Changes in the melting pattern of p53 were observed in DNAs from 9 of 29 X‐ray—transformed clones examined. No changes were found in untransformed, wild‐type 10T1/2 cell clones. These results indicate that X‐ray—induced p53 mutations may contribute to cell transformation.
Novel variants of CD44 arising from alternative splicing: Changes in the CD44 alternative splicing pattern of MCF‐7 breast carcinoma cells treated with hyaluronidase
Authors: Tanabe Kenneth K. , Nishi Toru , Saya Hideyuki 
Published: February 2007

AbstractCD44 is a cell‐surface glycoprotein postulated to play a role in a variety of biological processes, including lymphocyte homing and tumor‐cell metastasis. Several isoforms of CD44 have been identified in human cells, and the genesis of some of these isoforms has been attributed to alternative splicing. In the study presented here we amplified three novel transcript variants of CD44 from human cell lines using a reverse transcriptase‐polymerase chain reaction strategy. Two of the novel isoforms differed from previously described CD44 isoforms as a result of alternative splicing that occurred at previously reported splice junctions. The third novel CD44 isoform was generated from a previously unreported alternative splice junction near the 5′ end of the open reading frame. Southern blot analysis of genomic DNA revealed that these novel isoforms and all of the previously described CD44 isoforms arose from alternative splicing. The capability of cells to modify their CD44 alternative splicing pattern was demonstrated in MCF‐7 cells, which altered their CD44‐isoform expression pattern in response to treatment with hyaluronidase. A better understanding of mechanisms regulating CD44 alternative splicing may provide insights into diverse processes, including tumor‐cell metastasis and lymphocyte homing.
Association of protein kinase C activation with induction of ornithine decarboxylase in murine but not human keratinocyte cultures
Authors: Fischer Susan M. , Lee Marilyn L. , Maldve Regina E. , Morris Rebecca J. , Trono David , Burow David L. , Butler Andrew P. , Pavone Amy , Warren Barbour 
Published: February 2007

AbstractThe goal of this study was to compare the response of mouse epidermal keratinocytes (MEKs) and human epidermal keratinocytes (HEKs) to 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) with respect to the activation and downregulation of protein kinase C (PKC), the expression of c‐jun and c‐fos, and the expression and induction of ornithine decarboxylase (ODC) activity. Keratinocytes from adult CD‐1 mice and from discarded adult human skin were grown in primary culture in a high‐calcium serum‐free medium that supported proliferation and differentiation. Immunoblotting of freshly isolated and cultured MEKs and HEKs for isozymes of protein kinase C revealed that fresh HEKs contained PKCα, PKCβ, and PKCδ; no PKCγ, PKCϵ, or PKCζ were detected. In fresh MEKs, PKCα, PKCβ, PKCΔ, and PKCζ were observed, but not PKCγ or PKCζ. After 2 wk in culture, the isozyme profiles of MEKs and HEKs were similar except that PKCγ was noticeably present in HEK cultures. Activation of partially purified total PKC by TPA was similar in freshly isolated and cultured MEKs and HEKs, indicating that the two species were similar in this regard and that 2 wk of culture did not alter this characteristic. When MEK and HEK cultures were treated with TPA for 3 h, less than 30% of the control level of PKC activity was detected, indicating that TPA‐induced downregulation of PKC was similar in MEKs and HEKs. After treatment with TPA, MEK cultures produced a large induction of both c‐jun and c‐fos mRNA by 60 min, as determined by northern blot analysis, and a large induction of ODC mRNA and enzyme activity by 6 h. TPA treatment of cultured HEKs, however, did not induce ODC activity; in fact, less activity, compared with that of control cultures, was observed. Northern blot analysis also revealed no increase in c‐jun, c‐fos, and ODC mRNA in HEKs. However, c‐jun and c‐fos mRNA and both ODC mRNA and enzyme activity were induced in HEKs fed growth factors after several days of deprivation. This suggests that the lack of ODC induction by TPA in HEKs is probably due to species differences in downstream steps in PKC signal transduction.