bluuebunny/crossref_metadata_2025_split huggingface dataset:
Induction and progression of the transformed phenotype in cloned rat embryo fibroblast cells: Studies employing type 5 adenovirus and wild‐type and mutant Ha‐ras oncogenes
Authors: Boylan John F. , Shih Thomas Y. , Fisher Paul B. , Zimmer Stephen G. 
Published: February 2007

AbstractTransformation of cloned rat embryo fibroblast (CREF) cells with the wild‐type 5 adenovirus (wtAd5) transforming genes E1A and E1B (which extend from 0 to 11.2 map units) results in morphologically transformed cells that exhibit an increased saturation density in monolayer culture and display an anchorage‐independent phenotype. WtAd5‐transformed CREF (wtAd5 CREF) cells do not, however, induce tumors when injected subcutaneously into athymic nude mice or syngeneic Fischer rats. We have analyzed the effect of the ras oncogene and sitespecific mutants in the ras oncogene that result in p21 proteins with altered biochemical properties on the oncogenic and metastatic properties of singly (ras) and doubly (ras + wtAd5) transformed CREF cells. Transformants expressing the wild‐type ras p21 protein and ras mutants producing p21 proteins that retained GTP‐binding properties grew in agar, induced tumors in nude mice and syngeneic rats, and metastasized to the lungs of rats when injected into their tail veins. In contrast, cells transformed with the ras mutant 116K (which contains a mutation at residue 116 that produces a Lys instead of an Asn and does not bind GTP or induce CREF cells to grow in agar) did not become morphologically transformed and were not oncogenic when injected subcutaneously into either nude mice or Fischer rats; further, such cells were not metastatic when injected into the tail veins of Fischer rats. When the wild‐type ras or the ras mutants, including 116K, were expressed in nontumorigenic E1A‐plus‐E1B‐expressing wtAd5 CREF cells, transformed cells induced tumors in both types of animals. The CREF cells doubly transformed with 116K + wtAd5, unlike transformants containing the wild‐type ras and the other ras mutants that still retained GTP binding, were still unable to induce lung metastases. In addition, 116K + wtAd5—transformed CREF cells also did not display any alterations in morphology distinguishable from wtAd5 CREF cells and were not able to grow in agar with increased efficiency. These results indicate that the loss of GTP‐binding ability by this mutant p21 ras protein eliminated the ability of these proteins to induce an oncogenic phenotype in an immortal but normal CREF cell line. However, the mutant ras could cooperate with wtAd5 transforming genes in transformed CREF cells to make these cells progress to an oncogenic (but not metastatic) phenotype. © 1992 Wiley‐Liss, Inc.
Testicular adenoma and seminal vesicle engorgement in polyomavirus large‐T antigen transgenic mice
Authors: Chalifour Lorraine E. , Mes‐Masson Anne‐Marie , Gomes Margaret L. , Wang Nai‐Sang 
Published: February 2007

AbstractSix lines of transgenic mice harboring the cDNA for polyomavirus large‐T antigen (PVLT) linked to the mouse metallothionein‐1 promoter were isolated. The transgene was expressed in testes in all lines isolated and in testes and seminal vesicles in two lines. Three lines developed enlarged testes and seminal vesicles. Development of the phenotype was divided into three stages separable by age and pathology. In stage 1, birth to 6 mo, PVLT was expressed in testes but no pathology was noted; in stage 2, 6–10 mo, PVLT was expressed solely in testes and not in seminal vesicles, yet the seminal vesicles were enlarged; and in stage 3, 10 mo and older, both testes and seminal vesicles expressed PVLT and both were enlarged. Testes were up to sevenfold heavier and increased up to fourfold to fivefold in each dimension. Seminal vesicles were enlarged up to 20‐fold as the result of an accumulation of seminal vesicle fluid. In addition to the four major proteins of seminal vesicle fluid, extra proteins, initially found in stage 2, were increased in stage 3 seminal vesicle fluid. The Leydig cell was the dominant cell type in affected testes, there were few or no normal Sertoli cells or seminiferous tubules remaining by stage 3. The Leydig cells were physiologically active, as indicated by a 8.5‐fold higher testosterone level in sera from stage 3 affected mice compared with sera from age‐matched normal males. PVLT was present in the nuclei of the Leydig cells and was able to confer an immortal phenotype in vitro. Formation of the Leydig cell adenoma was dependent on PVLT expression, but since PVLT expression occurred much earlier than did pathology, additional secondary factors must determine the delay in phenotype development. © 1992 Wiley‐Liss, Inc.
Association of induction of a fully tumorigenic phenotype in murine radiation‐induced T‐lymphoma cells with loss of differentiation antigens, gain of CD44, and alterations in p53 protein levels
Authors: Gjerset Ruth A. , Arya Jyoti , Volkman Sarah , Haas Martin 
Published: February 2007

AbstractWe investigated the mechanism of radiation induction of murine thymic lymphomas by studying the characteristics of primary x‐ray–induced thymic lymphoma (PXTL) cell lines and of their oncogene‐induced, progressed progeny. It is widely thought that proto‐oncogene alterations are associated with the induction of murine lymphomas; however, few, if any primary murine radiation‐induced lymphomas possess (proto‐)oncogene alterations. Independently derived cell lines grown directly (i.e., without in vivo transplantation) from thymic lymphomas of irradiated C57BL/6 mice possess the properties of immortalized pre‐T cells and lack many of the characteristics of “tumor cells”. PXTL cells are poorly tumorigenic upon transplantation, do not clone in methylcellulose cultures, are growth factor dependent and autocrine, and lack consistent chromosome and oncogene abnormalities. However, the thymic lymphomas are malignant and cause the death of each afflicted mouse. PXTL cells expressed two immunologically distinct forms of the tumor suppressor protein p53 that have moderately increased stability (t1/2 = 1 h) when compared with p53 of normal splenic T lymphocytes. Early PXTL cells could progress in vitro to a fully tumorigenic phenotype after infection with retroviruses encoding the c‐myc and v‐ras oncogenes. Progressed T‐lymphoma cells acquired growth factor independence, a highly transplantable and tumorigenic phenotype, and the ability to quantitatively clone in methylcellulose cultures. Progressed lymphoma cells coordinately downregulated the expression of five T‐cell differentiation markers, upregulated the expression of CD44 (Pgp‐1), and harbored vastly elevated levels of two immunologically distinct forms of p53. Our results suggest that the early thymic lymphomas consist of differentiation‐inhibited, immortal pre‐T cells that are precursors to progressed, fully tumorigenic T‐lymphoma cells. © 1992 Wiley‐Liss, Inc.
Overexpression of the c‐erbB‐2/neu–encoded p185 protein in primary lung cancer
Authors: Shi Daren , He Gongping , Cao Shilong , Pan Wensheng , Zhang Hua‐Zhong , Yu Dihua , Hung Mien‐Chie 
Published: February 2007

AbstractThe c‐erbB‐2/neu gene encodes a transmembrane protein of 185 kDa (p185) with tyrosine kinase activity and extensive sequence homology to epidermal growth factor receptor. Amplification and overexpression of the c‐erbB‐2/neu gene has been shown in certain human tumors and is postulated to be important in human carcinogenesis. High levels of expression of the c‐erbB‐2/neu gene have been reported in non‐small‐cell lung cancer (NSCLC) cell lines and primary tumors from the United States. Since geographical and cultural factors may contribute to the development of certain types of cancer, we examined p185 expression in 120 tumors from Chinese patients with lung cancers of different cell types and used immunohistochemical staining to determine the extent and general significance of p185 expression in human primary lung cancer. Our results demonstrate that 58.8% of the NSCLCs expressed p185 and that expression of p185 was observed only in NSCLC and not in small‐cell lung cancers. Thirty‐three of 41 adenocarcinomas and 24 of 55 squamous cell carcinomas among the NSCLCs examined were found to express p185 at levels different from those of normal lung. For the squamous cell carcinomas, p185 expression was correlated with lymph node metastasis (P < 0.01), but for the adenocarcinomas, it was not (P > 0.05). In addition, expression of p185 in NSCLC was significantly more frequent in patients in advanced clinical stages. Our findings indicate that p185 expression is a frequent event and a general phenomenon in NSCLC and is correlated with poor clinical prognostic indicators, suggesting that expression of p185 may be of potential prognostic importance in NSCLC. © 1992 Wiley‐Liss, Inc.
Induction of CYP1A1 gene expression in H4‐II‐E rat hepatoma cells by benzo[e]pyrene
Authors: Houser William H. , Raha Abhijit , Vickers Michelle 
Published: February 2007

AbstractIn the rat, expression of the CYP1A1 gene is closely associated with arylhydrocarbon hydroxylase (AHH) enzyme activity. AHH is an inducible enzyme activity known to play an important role in the bioactivation of polycyclic aromatic hydrocarbons (PAHs) to mutagenic and carcinogenic metabolites. PAH‐induced expression of the CYP1A1 gene appears to be regulated by several trans‐acting factors, including the Ah receptor and the 4S PAH‐binding protein. In this study, we used the PAH isomers benzo[a]pyrene (BaP) and benzo[e]pyrene (BeP) to further evaluate the role of the 45 PAH‐binding protein in induction of the CYP1A1 gene in H4‐II‐E rat hepatoma cells. Although BaP is believed to bind to both the Ah receptor and the 4S protein, BeP has been reported to bind exclusively to the 4S protein. The results of the study presented here indicate that BaP and BeP induce the expression of the CYP1A1 gene, as measured by ethoxyresorufin O‐deethylase (EROD) activity, in a concentration‐dependent manner. However, BaP is about 25 times as potent as BeP in inducing EROD activity in these cells. Slot‐blot analysis of total RNA isolated from these cells indicated that BeP, BaP, and 3‐methylcholanthrene increased the level of CYP1A1 mRNA expression. Sucrose‐gradient analysis of BeP binding activity indicated that BeP bound with high affinity to the 45 PAH‐binding protein, but not to the Ah receptor. These results suggest that the 45 protein may play a role in the PAH‐induced expression of the CYP1A1 gene in rat H4‐II‐E cells. © 1992 Wiley‐Liss, Inc.
Alterations in tumor angiogenesis associated with stable expression of the HIV tat gene
Authors: Huber Brian E. , Richards Cynthia A. , Martin J. Louise , Wirth Peter J. 
Published: February 2007

AbstractRecent evidence suggests that the human immunodeficiency virus type 1 (HIV) trans‐activator gene (tat) has transforming properties and may be a causative factor in the development of certain types of cancers, in particular Kaposi's sarcoma (i.e., Vogel J. et al. Nature 335:606–611, 1988). To help elucidate the potential role or roles of the HIV tat gene in neoplastic transformation, cell lines were constructed that constitutively express a functional tat gene product. HeLa cells were coelectroporated with two plasmids, one containing the HIV tat gene in an expression cassette and another containing the dominant selectable marker gene xanthine guanine phosphoribosyltransferase (XGPRT). After XGPRT selection, single‐cell clones that expressed a functional tat protein were identified by measuring chloramphenicol acetyltransferase (CAT) activity after electroporating a plasmid containing the CAT gene transcriptionally controlled by HIV trans‐activation‐responsive region (tar). Phenotypic alterations resulting from the expression of tat were then determined. Control cells and tat‐expressing cells grew at similar rates in culture. However, when grown as tumors in nude mice, tat‐expressing cells produced a lower percentage of tumors, and the tumors that were produced either regressed, stopped growing, or grew at a very reduced rate compared with cells not expressing tat. These differences may have resulted from a tat‐associated reduction in neovascularization in the tumors. A comparison of total cellular proteins by two‐dimensional polyacrylamide gel electrophoresis indicated only one reproducible alteration in a polypeptide of approximately 44 kDa and p1 of approximately 6.2 associated with tat expression. These cells may be very useful in future in vitro and in vivo studies designed to examine the effects of HIV tat on endothelial and vascular smooth‐muscle cells and the role of tat in the etiology of Kaposi's sarcoma. © 1992 Wiley‐Liss, Inc.
Expression of c‐erb B‐2/neu proto‐oncogene in human prostatic cancer tissues and cell lines
Authors: Zhau Haiyen E. , Wan De Sen , Zhou Jianxin , Miller Gary J. , von Eschenbach Andrew C. 
Published: February 2007

AbstractBoth amplification and overexpression of c‐erb B‐2/neu have been associated with the progression and possible prognosis of a number of human cancers. In this study, we demonstrated that c‐erb B‐2/neu may also play an important role in human prostate cancer. Our conclusion is based on the following observations: (1) A monoclonal antibody raised against a peptide sequence from the C‐terminal domain of the human c‐erb B‐2/neu gene product reacted positively with 68.7% (11 of 16) of the human prostatic cancer tissue extracts analyzed by western blot procedure. These results were supported by the immunohistochemical staining of the prostatic cancer specimens; 80% (12 of 15) showed positive staining, primarily around the plasma membranes of the prostatic cancer cells, c‐erb B‐2/neu oncoprotein was not detectable in normal prostate tissues (five examined by immunohistochemical staining and three by western blotting) or in human benign prostatic hyperplasia (two examined by immunohistochemical staining and six by western blotting) and was expressed less abundantly with lower intensity in “normal” human prostate tissues adjacent to cancerous prostate tissue (5 of 12 examined by immunohistochemical staining). We observed no evidence of c‐erb B‐2/neu gene amplification in 10 fresh human prostatic cancer specimens examined by Southern blotting and in the cultured human prostatic cancer cell lines PC‐3, DU‐145, and LNCaP. (2) The c‐erb B‐2/neu protein was detected in both androgen‐receptor‐positive (LNCaP) and ‐negative (PC‐3 and DU‐145) human prostate cancer cell lines. Positive immunostaining of c‐erb B‐2/neu protein was found to be associated predominantly with the plasma membranes of PC‐3 cells, but was also found to be widespread in the cytoplasmic region of the LNCaP cells and in the perinuclear region of the DU‐145 cells. (3) Like prostate‐specific antigen (PSA) expression, c‐erb B‐2/neu mRNA expression was also positively regulated by androgen in androgen‐receptor‐positive LNCaP cells in vitro and LNCaP tumors in vivo. When LNCaP tumors were grown in castrated male hosts, levels of c‐erb B‐2/neu and PSA mRNA expression decreased initially, but rebounded at 3 wk to levels comparable to those expressed by tumors maintained in intact adult male hosts. © 1992 Wiley‐List, Inc.
Resistance of adult keratinocytes to differentiation‐induced decrease in Ha‐ras mrna levels observed in newborn keratinocytes
Authors: Betz Natalie A. , Pelling Jill C. 
Published: February 2007

AbstractDuring two‐stage mouse skin tumorigenesis, the mouse c‐Ha‐ras oncogene undergoes activation by point mutation after initiation with polycyclic aromatic hydrocarbons. Furthermore, initiated epidermal cells containing an activated Ha‐ras oncogene have been shown to be resistant to calcium‐induced terminal differentiation. However, the relationship between Ha‐ras expression and the differentiation process is not well understood in either normal or initiated cells. Before attempting to explore the role of Ha‐ras expression in epidermal differentiation during tumorigenesis, we felt that investigation of Ha‐ras gene expression in normal primary epidermal cells undergoing differentiation was warranted, since primary cultures of normal newborn and adult keratinocytes presumably contain the stem cells from which skin tumors arise. In the present studies, northern blot analysis was used to compare Ha‐ras expression in normal newborn and adult epidermal cells undergoing differentiation. Steady‐state levels of Ha‐ras mRNA remained unchanged in primary cultures of normal adult epidermal cells during calcium‐induced differentiation, whereas steady‐state levels of Ha‐rastranscripts decreased during calcium‐induced differentiation in primary newborn epidermal cells. Differentiation was induced by switching the adult and newborn keratinocytes from medium containing 0.05 mM Ca2+ to medium containing one of three different calcium concentrations (0.15, 0.5, or 1.2 mM Ca2+). The decrease in Ha‐ras mRNA levels observed during differentiation in newborn keratinocytes occurred as an intermediate event in the differentiation process, was specific for the Ha‐ras gene, and was not due to a general decrease in transcriptional activity during differentiation. Characteristic patterns of keratin 14 gene expression and cornified envelope formation were observed, verifying that the differentiation process had been induced in both the primary adult and newborn epidermal cells. That adult keratinocytes are resistant to the differentiation‐induced reduction in Ha‐ras mRNA expression observed in newborn keratinocytes may explain the difference in in vivo tumorigenic potentials of newborn and adult skin. © 1992 Wiley‐Liss, Inc.
Relationship between the expression of differentiation‐specific keratins 1 and 10 and cell proliferation in epidermal tumors
Authors: Kartasova Tonja , Roop Dennis R. , Yuspa Stuart H. 
Published: February 2007

AbstractIn normal epidermis, the expression of keratins 1 and 10 is associated with the loss of proliferative capacity and the onset of terminal differentiation. Keratins 1 (K1) and 10 (K10) are commonly expressed in the differentiating layer of benign tumors, but are lost during progression from the benign to the malignant state in skin carcinogenesis. Active gene constructs of mouse K1 and K10 were introduced into papilloma and carcinoma cell lines derived from keratinocytes to analyze the consequences of the expression of these keratins on the organization of the endogenous cytoskeletal network and on the mitotic activity of the recipient cells. Exogenous K1 integrated into the preexisting keratin K5/K14 network of both SLC‐1 carcinoma and 308 papilloma cells. The formation of a recombinant cytoskeleton was more restricted for K10 than for K1 and appeared to be related to a requirement for cessation of cell division before K10 could integrate. The integration of exogenous K1 filaments into the endogenous keratin network was compatible with sustained proliferation of SLC‐1 carcinoma cells in vitro. However, the exogenous gene was not expressed in tumor grafts in vivo. In contrast, stable K1 or K10 transfectants could not be selected in 308 cells, suggesting that benign tumor cells expressing suprabasal keratins cannot sustain proliferation. Published 1992 Wiley‐liss. Inc.
Mutagenesis by apurinic sites in normal and ataxia telangiectasia human lymphoblastoid cells
Authors: Klinedinst Donna K. , Drinkwater Norman R. 
Published: February 2007

AbstractWe used a shuttle vector based on the Epstein‐Barr virus origin of plasmid replication (oriP) to determine the types of mutations induced by depurination in human cells. Plasmid DNA was incubated at pH 2 at 40°C for various times to induce up to 20 apurinic (AP) sites per 9.7‐kb plasmid and electroporated into lymphoblastoid cells derived from either a normal individual or an ataxia telangiectasia patient. After replication of the vector in the human cells, plasmid DNA was isolated and analyzed for mutations induced in the plasmid‐encoded herpes simplex virus type 1‐thymidine kinase gene. Both the frequencies and types of mutations induced by depurination were essentially identical for normal and ataxia telangiectasia cells. The mutant frequency at 20 AP sites/plasmid was 10‐fold to 13‐fold greater than that observed for untreated DNA. Deletion and frameshift events accounted for 46–55% of the mutants induced by depurination. The induced deletions were relatively small (median size, 100–150 bp) and characterized by short (1–5 bp) regions of sequence homology at the end‐points. These mutations and the frameshifts, a majority of which occurred in runs of identical nucleotides, are consistent with a model involving AP‐site‐induced template dislocation during DNA synthesis. A broad spectrum of base‐substitution mutations, which accounted for 19–36% of the induced mutants, was observed. The apparent preference for insertion opposite AP sites in human cells was G (43–55%) > A°C (18–21%) > T (9–14%). Our results in human cells contrast markedly with those published previously for the mutational specificity of AP sites in Escherichia coli, in which a large majority of the mutants resulted from insertion of an A opposite the abasic site.© 1992 Wiley‐Liss, Inc.
Analysis of point mutations in murine c‐Ha‐ras of skin tumors initiated with dibenz[a,j]anthracene and derivatives
Authors: Gill Rosalynn D. , Beltrán Linda , Nettikumara Anusha N. , Harvey Ronald G. , Kootstra Arend , Digiovanni John 
Published: February 2007

AbstractThis study was designed to evaluate the point mutations in the murine c‐Ha‐ras gene of skin papillomas induced by initiation with dibenz[a,j]anthracene(DB[a,j]A), its bay‐region anti‐diol epoxide ((± anti‐DB[a,j]A‐DE), and a 7,14‐dimethyl analogue (7,14‐diMeDB[a,j]A). Recent studies (Nair RV, et al., Chem Res Toxicol 4:115–122, 1991) in our laboratory have revealed both deoxyguanosine (dGuo) and deoxyadenosine (dAdo) adducts formed from the anti‐ and syn‐diol epoxides of DB[a,j]A in cultured mouse epidermal cells after exposure to this hydrocarbon. Using PCR amplification and direct sequencing, we found specific A182±T transversion mutations (eight of 10 tumors) in codon 61 of c‐Ha‐ras in papillomas induced by initiation with DB[a,j]A. Analysis of papillomas generated by initiation with the more biologically potent analogue 7,14‐diMeDB[a,j]A revealed that five of five tumors exhibited A182±T transversions in codon 61. The nature of the changes in the two DB[a,j]A tumors not showing codon 61 mutations in Ha‐ras is currently not known since these tumor DNAs also did not possess c‐Ha‐ras mutations at codons 12,13, or 59. Interestingly, papillomas produced by initiation with (±)anti‐DB[a,j]A‐DE also possessed A182±T transversion mutations in codon 61 of c‐Ha‐ras (five of five tumors). These data suggest that dAdo adducts derived from both parent hydrocarbons may play an important role in their tumor‐initiating activity and possibly implicate a specific diol epoxide‐dAdo adduct in this process. © 1992 Wiley‐Liss, Inc.