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PubMed1984

Expression of the transformation-sensitive protein "cyclin" in normal human epidermal basal cells and simian virus 40-transformed keratinocytes.

A cell population highly enriched in human epidermal basal cells has been obtained and characterized by using antibodies specific for various cell types in the epidermis. Quantitative two-dimensional gel electrophoretic analysis (isoelectric focusing) of [35S]methionine-labeled polypeptides from basal cells and simian virus 40-transformed keratinocytes showed that the basal cells synthesize very low amounts (less than 0.02% of the total protein) of the nuclear, transformation-sensitive protein cyclin as compared to the transformed cells, which synthesize this protein constitutively (0.15% of the total protein). Very low levels of cyclin were observed in total human epidermis, and preliminary studies of two basaliomas have shown a significant synthesis of this protein in these tumors. Immunofluorescence studies using antibodies to proliferating cell nuclear antigen that immunoprecipitate cyclin confirmed the above observations at least in the case of the cultured cells. Taken together, these results support the notion that cyclin may be a central component of the pathway(s) that controls cell proliferation.

Antigens, Neoplasm↗
PubMed1973

An enzymatic function associated with transformation of fibroblasts by oncogenic viruses. I. Chick embryo fibroblast cultures transformed by avian RNA tumor viruses.

Chick embryo fibroblast cultures develop fibrinolytic activity after transformation by Rous sarcoma virus (RSV). This fibrinolytic activity is not present in normal cultures, and it does not appear after infection with either nontransforming strains of avian leukosis viruses or cytocidal RNA and DNA viruses. In cultures infected with a temperature sensitive mutant of RSV the onset of fibrinolysis appears after exposure to permissive temperatures and precedes by a short interval the appearance of morphological evidence of transformation. See PDF for Structure The rate of fibrinolysis in transformed cultures depends on the nature of the serum that is present in the growth medium: some sera (e.g., monkey or chicken serum) promote high enzymatic activity, while others (calf, fetal bovine) do not. Some sera contain inhibitors of the fibrinolysin. Based on the effect of a small number of known inhibitors, at least one step of the fibrinolytic process shows specificity resembling that of trypsin. The sera of sarcoma-bearing chickens contain an inhibitor of the fibrinolysin, whereas normal chicken sera do not. For general discussion, conclusions, and summary see the accompanying paper, part II, (J. Exp. Med. 137:112).

Animals↗
PubMed1989

Enhanced plasminogen activator production of Syrian hamster embryo cells transformed by chemicals or the c-Ha-ras oncogene: type of plasminogen activators involved and their contribution to the transformed phenotype.

The plasminogen activator (PA) activity produced by Syrian hamster embryo (SHE) cells in different stages of neoplastic conversion was analysed. PA activity was characterized immunologically and by SDS-PAGE. Normal SHE cells had a very low PA activity. Although activity of either the tissue type of PA (t-PA) or the urokinase type (u-PA) or both were found to be increased in most immortal or transformed SHE cells, there was no correlation between enhanced production of a particular PA type and the development of the immortal or transformed phenotype. However, within a group of cell lines clonally derived from a culture of immortal cells, a positive correlation was found between extracellular t-PA, but not u-PA, activity and cellular growth rate. For the Syrian hamster PA species, crossreacting with anti-human u-PA, a mol. wt of 39 kd was observed. For the Syrian hamster PA species, crossreacting with anti-human t-PA, multiple species were found with mol. wts of 98, 72 and 59 kd respectively. Evidence was obtained that the 72-kd species represents the intact enzyme, the 59-kd species a partial digestion product thereof and the 98 kd species, which often appears as a doublet, a complex of either of these species with an inhibitor, likely to be secreted by the same cells. Finally, our data suggest a novel mechanism for the enhancement of t-PA activity of transformed cells, namely by a decrease in the effective extracellular amount of putative inhibitor.

Animals↗
PubMed1995

Malignantly transformed non-parenchymal liver epithelial cells and transformed oval cells suppress the homotypical gap junctional intercellular communication of co-cultured rat liver parenchymal cells.

Isolated rat liver parenchymal cells (PC) were co-cultured with a non-parenchymal rat liver epithelial cell line (NEC) or with an oval cell line. The homotypical gap junctional intercellular communication (GJIC) between the liver PC was measured after microinjection of Lucifer Yellow by dye transfer. The rat liver PC were dye coupled between 87% and 100% for at least 1 week in both co-cultures, in contrast to PC In monoculture between which no dye coupling was left after 1 week. When liver PC were co-cultured with a transformed and tumorigenic NEC or with a transformed and tumorigenic oval cell line the homotypical GJIC between the liver PC was drastically decreased with culture time, and the PC were then compressed and displaced by the expansive growth of the transformed cell lines. The disturbance of the GJIC between normal cells by adjacent tumorigenic cells might be a new mechanism to explain the expansive growth of tumors.

Animals↗
PubMed1997

Computerized image analysis of morphologically transformed and nontransformed Syrian hamster embryo (SHE) cell colonies: application to objective SHE cell transformation assay scoring.

We have developed an automated image analysis system that provides comparable classification of morphologically transformed SHE cell colonies to the current visual classification method used in the in vitro SHE cell transformation assay. Visual classification of morphologic transformation in this assay has been shown to accurately predict the carcinogenic potential of chemical, biological and physical agents. The image analysis system is quantitative, based on measuring features of colony color, texture and growth patterns. A linear combination of feature measurements produces a classification process that agrees with visual assessment 93% of the time. All identifiable sources of error are explored and the method is found to be robust in analyzing nearly 500 colonies from a variety of studies performed over a one year period. The high degree of correlation between the visual classification and the objective measurements of the image analysis system validates the reproducibility of the visual scoring process and serves as a basis for automation of the assay.

Animals↗
PubMed1995

A specific chromosome change and distinctive transforming genes are necessary for malignant progression of spontaneous transformation in cultured Chinese hamster embryo cells.

Chinese hamster embryo (CHE) cell strains, each initiated from a separate cell stock obtained from different mothers, were transferred successively at intervals of 3 days and the changes in growth properties and karyotypes at various passages were examined. All nine cell strains proliferated at varying growth rates for 60 passages but only 2 (designated CHE A1 and CHE A2) of them expressed malignant phenotypes. The acquisition of tumorigenicity in nude mice was observed in CHE A1 and CHE A2 cells at passages 40 and 10, respectively. After 5 passages, 8 of 9 cell strains contained one or two common additional chromosomes, chromosome 3q and/or chromosome 5, although one cell strain (designated CHE A3) maintained a normal diploid karyotype for 60 passages. Trisomy of chromosome 3q was observed in all tumorigenic CHE A1 and A2 cells. One or two 3q chromosomes were detected in all tumor-derived cell lines established from tumors produced by these tumorigenic cells. DNA from tumorigenic cells and tumor-derived cell lines exhibited a high ability to transform mouse NIH3T3 cells, but we could not detect any activation of Ha-ras, Ki-ras, hst, erbB-2, mos, met or raf in any of the transformed NIH3T3 cells. These results suggest that even though cultured CHE cells can transform spontaneously, without any specific chromosome change, to immortal cells, activation of unknown oncogene(s) in addition to a specific chromosome change may be required for their malignant progression. Our results suggest that trisomy of chromosome 3q is this specific chromosome change.

3T3 Cells↗
PubMed1980

Localized blastoma preceding blastic transformation in Ph1-positive chronic myelogenous leukaemia: morphological and cultural studies of the transformation event.

In a patient with Ph1-positive chronic myelogenous leukaemia (CML), the development of a localized blastoma preceding generalized blastic transformation was accompanied by a reduction of granulocyte-macrophage (GM) colony forming capacity in agar of bone marrow cells as well as an increase in peripheral neutrophil alkaline phosphatase (NAP) scores. Successful transplantation of the blastoma cells into nude mice enabled extensive studies of the cell properties. The blastoma cells were double Ph1-positive cells which did not respond to human granulocyte-macrophage colony-stimulating factor (GM-CSF), and were similar to cells demonstrated in spleen and bone marrow at the terminal stage of the patient's illness. These observations clearly support the case for sequential studies of colony formation in vitro as a useful test for the early detection of disturbances in marrow function that may occur before generalized blastic transformation. Studies of the properties of the blastoma cells also provide some insight into possible mechanisms for the transformation event.

Aged↗
PubMed1985

Reversibility of progression of the transformed phenotype in Ad5-transformed rat embryo cells.

The carcinogenic process is extremely complex and is affected by diverse environmental and host factors. The mechanism for the gradual development of the transformed phenotype (a process termed "progression") was studied in type 5 adenovirus (Ad5)-transformed rat embryo cells. Progression was not correlated with major changes in the pattern of integration of viral DNA sequences. Instead, it was associated with an increased methylation of integrated viral sequences other than those corresponding to the E1 transforming genes of Ad5. A single exposure of progressed cells to the demethylating agent 5-azacytidine (Aza) resulted in a stable reversion to the unprogressed state of the original parental clone. A further selection of cells after growth in agar allowed the isolation of Aza-treated clones that had regained the progressed phenotype. These observations indicate that progression is a reversible process and suggest that progression may be associated with changes in the state of methylation of one or more specific genes.

Adenoviruses, Human↗
PubMed1991

Transformation system for an asporogenous methylotrophic yeast, Candida boidinii: cloning of the orotidine-5'-phosphate decarboxylase gene (URA3), isolation of uracil auxotrophic mutants, and use of the mutants for integrative transformation.

An integrative transformation system was established for an asporogenous methylotrophic yeast, Candida boidinii. This system uses a uracil auxotrophic mutant of C. boidinii as the host strain in combination with its URA3 gene as the selectable marker. First, the C. boidinii URA3 gene coding for orotidine-5'-phosphate decarboxylase (ODCase) was cloned by using complementation of the pyrF mutation of Escherichia coli. Next, the host ODCase-negative mutant strains (ura3 strains) were isolated by mutagenesis and selection for 5-fluro-orotic acid (5-FOA) resistance. Five ura3 host strains that exhibited both a low reversion rate and good methylotrophic growth were obtained. All of these strains could be transformed to Ura+ phenotype with a C. boidinii URA3-harboring plasmid linearized within the Candida DNA. The transformants had a stable Ura+ phenotype after nonselective growth for 10 generations. These results and extensive Southern analysis indicated that the linearized plasmid was integrated into the host chromosomal DNA by homologous recombination at the URA3 locus in C. boidinii.

Blotting, Southern↗
PubMed1970

Mechanism of oncogenic transformation by Rous sarcoma virus. I. Intracellular inactivation of cell-transforming ability of Rous sarcoma virus by 5-bromodeoxyuridine and light.

Chick embryo fibroblasts brought into stationary phase of growth by maintenance in serum-free Eagle's MEM medium were infected with the Bryan strain of Rous sarcoma virus (B-RSV) and incubated for 18 hr in the presence of 5-bromo-deoxyuridine (BUdR). The cells were then allowed to resume growth and deoxyribonucleic acid (DNA) synthesis by addition of an enriched F12 medium containing serum and RSV antibody to prevent spread of viral infection. After 48 hr, the cultures were exposed for various periods to visible light, overlaid with solid culture medium, and observed for the appearance of foci of transformed cells. In cultures treated with BUdR at the time of infection, exposure to light resulted in a suppression of focus formation of from 50 to 90% in various experiments. Treatment with BUdR for 18 hr before infection or on the day after infection, followed by exposure to light, had no effect on focus formation. In cultures in which almost all cells were infected, treatment with BUdR followed by exposure to light did not result in cell death. This suggests that suppression of transformation is not due to selective killing of infected cells by this treatment but rather to the intracellular inactivation of the transforming ability of Rous sarcoma proviral DNA.

Animals↗
PubMed1985

Membrane association of the transforming protein of avian sarcoma virus UR2 and mutants temperature sensitive for cellular transformation and protein kinase activity.

The localization of the transforming protein P68gag-ros of avian sarcoma virus UR2, which has a hydrophobic region at the N terminus of its ros-specific tyrosine kinase-encoding sequence, was examined by subcellular fractionation. P68 behaved as an integral membrane protein associated with the plasma membrane of transformed cells. P68 became membrane associated very rapidly in its biogenesis. Three temperature-sensitive mutants of UR2 were isolated and characterized. Cells infected with the mutants were temperature sensitive for morphological alteration and colony formation. The mutant P68 proteins were membrane associated in mutant-infected cells regardless of the temperature but were active as protein kinases only at the permissive temperature. The results suggest that P68 is a membrane-associated protein whose kinase activity plays a crucial role in UR2-mediated cell transformation.

Animals↗
PubMed1987

MC29 deletion mutants which fail to transform chicken macrophages are competent for transformation of quail macrophages.

A number of MC29 mutants with deleted myc genes have been previously characterized. Many of these mutants have been found to be defective for transformation of chicken macrophages in vitro and for tumor induction in chickens. Such mutants are capable of transforming Japanese quail macrophages in vitro and inducing a high incidence of tumors in Japanese quail. Thus, Japanese quail may contain a factor(s) capable of complementing the defective transforming proteins encoded by some deleted v-myc genes.

Animals↗
PubMed1988

p59v-rel, the transforming protein of reticuloendotheliosis virus, is complexed with at least four other proteins in transformed chicken lymphoid cells.

Previous studies have identified the protein product of v-rel, the oncogene carried by reticuloendotheliosis virus (REV), as a 59,000-dalton phosphoprotein located predominantly in the cytosol of transformed chicken lymphoid cells. In immune precipitates of p59v-rel, there is a closely associated protein kinase activity. In chicken lymphoid cells that do not contain REV, p68c-rel is found free in the cytosol not associated with other proteins and not detectably phosphorylated. In this study, we found that immune precipitates of 59v-rel from REV-transformed cells contain at least four other proteins, of approximate molecular weights 124, 115, 68, and 36 kilodaltons (kDa). The 124-, 115-, and 36-kDa proteins are apparently unrelated to p59v-rel in sequence, and their coprecipitation suggests that they are complexed with p59v-rel. The coprecipitating 68-kDa protein was found to be p68c-rel, which, like the other three proteins, precipitates by virtue of its association with p59v-rel. Glycerol gradient analysis suggested the presence of more than one type of complex: one containing p115, p68c-rel, p59v-rel, and p36, and another containing p124, p115, p59v-rel, and possibly p68c-rel. In vitro kinase activity was found in all size classes, coinciding with the distribution of p115 and p59v-rel. The complex(es) was stable under a variety of conditions, including a wide range of ionic strengths, chelators, and detergents, and through multiple cycles of immune precipitation and elution. This suggests a specific and functionally significant interaction among the members that may be of direct relevance to the mechanism of REV-induced transformation.

Animals↗
PubMed1983

Dissociation between transformed and differentiated phenotype in rat thyroid epithelial cells after transformation with a temperature-sensitive mutant of the Kirsten murine sarcoma virus.

Differentiated rat thyroid epithelial cells, infected in vitro with a temperature-sensitive mutant of the Kirsten murine sarcoma virus, expressed at the permissive temperature (33 degrees C) some phenotypic properties typical of transformed cells, including morphological features, colony formation in agar, and induction of tumors in newborn animals. Specific functional markers of these differentiated cells, i.e., synthesis/secretion of thyroglobulin, synthesis of thyroglobulin mRNA and iodide uptake, were blocked during growth at 33 degrees C. Normal morphology, failure to grow in agar, and the requirement of hormones for optimal growth were all restored after shifting to the temperature nonpermissive for transformation (39 degrees C), though the typical differentiated functions remained blocked. Infection with a leukemia helper virus clone (Moloney or Kirsten murine leukemia virus) did not lead to the loss of the differentiated phenotype of rat epithelial thyroid cells, thus demonstrating that the loss of the differentiated phenotype is caused by the sarcoma virus component. These results indicate that the expression of some of the phenotypic properties of transformed differentiated rat thyroid epithelial cells is under the direct control of the p21 thermosensitive activity, whereas the block in the expression of two typical differentiation markers of thyroid epithelial cells is irreversible and probably controlled by different mechanisms.

Animals↗
PubMedDate not supplied

Presence of herpesvirus-associated antigens on the surfaces of transformed, tumor, and metastatic cells and enhanced antigenicity of transformed cells using 5-iodo-2'-deoxyuridine.

Using a direct immunofluorescence technique, herpes simplex virus type 1 (HSV-1)-transformed cells and cell lines subsequently derived from tumors and metastases were examined for the presence of HSV-1-associated surface antigens. Fluorescein-labeled immunoglobulins derived from antisera were used and included anti-HSV-1 (from hamsters), sera from tumor-bearing hamsters, and antibodies prepared in rabbits against cell material shed early into the medium after infection of rabbit kidney cells with HSV-1. All immunoglobulins showed the greatest reactivity with cell lines derived from tumors and metastatic lesions. There appeared to be little or no reactivity on the surfaces of the transformed cells. Transformed cells treated with 5-iodo-2'-deoxyuridine for 48 h, however, showed an enhanced reactivity which approached that seen with the tumor-derived cell lines.

Animals↗
PubMed2005

Pituitary tumor transforming gene binding factor: a novel transforming gene in thyroid tumorigenesis.

CONTEXT: There are currently no clear markers for the detection of differentiated thyroid cancer and its recurrence. Pituitary tumor transforming gene (PTTG) is a protooncogene implicated in the pathogenesis of multiple tumor types, which stimulates fibroblast growth factor-2 secretion via PTTG binding factor (PBF). OBJECTIVE: The aim of this study was to ascertain whether PBF expression is associated with thyroid cancer outcome. DESIGN: PBF expression was measured at the mRNA and protein level. Tissue was collected during surgery, with normal samples being taken from the contralateral lobe. In vitro studies ascertained the ability of PBF to transform cells and form tumors in nude mice and its subcellular localization. SETTING: The study was conducted at a primary care/referral center. PATIENTS: Thyroid tumors were collected from a series of 27 patients undergoing surgical excision of papillary and follicular thyroid tumors. INTERVENTION: No intervention was conducted. MAIN OUTCOME MEASURE: The expression of PBF in thyroid cancers compared with normal thyroid, hypothesized before the investigation to be raised in tumors, was the main outcome measure. RESULTS: PBF mRNA expression was higher in differentiated thyroid carcinomas than in normal thyroid (P < 0.001; n = 27) and was independently associated with tumor recurrence (P = 0.002; R(2) = 0.49). PTTG was able to up-regulate PBF mRNA expression in vitro (P < 0.001; n = 12), and stable overexpression of PBF in NIH3T3 cells resulted in significant colony formation (P < 0.001; n = 12). In vivo, stable sc overexpression of PBF induced tumor formation in athymic nude mice. CONCLUSIONS: PBF is an additional prognostic indicator in differentiated thyroid cancer that is transforming in vitro and tumorigenic in vivo.

Adult↗
PubMed1979

[Spontaneous transformation characteristics of Bacillus subtilis bacteria. I. The relatively low transforming activity of spontaneously released DNA for markers located close to the origin and termination points of chromosome replication].

Relative efficiencies of spontaneous Bacillus subtilis transformation for markers placed in different areas of the cell chromosome were studied. As donor of genetic material, an untransformable strain BD224 trpC2 thr5 rec4 was used during its early log-phase. It was found that for markers placed near points of origin and termination of the chromosome replication the relative transformation efficiencies are significantly lower than those in the case of transformation with DNA extracted from the same donor cells. If a contact of spontaneously released DNA with the recipient cells was delayed for about 60 minutes ("separate" experiment) this difference proved to be less pronounced for ade16 placed near the origin, but remained practically unchanged for metB placed near the termination point. The results obtained can be explained by permanent attachment of chromosome regions, carrying "origin" and "termination" points, to a cytoplasmic membrane. During spontaneously release of cellular genetic material, "origin" and "terminal" DNA fragments carrying ade16 and metB respectively, can retain the contact with components of cell membrane. Hence, their penetration in the recipient cell and (or) participation in recombination can be violated. The first of two fragments becomes free from structurating substances more easy.

Bacillus subtilis↗
PubMed1992

Transforming growth factor-beta and transforming growth factor beta-receptor expression in human meningioma cells.

The transforming growth factor-beta (TGF beta) family in mammals includes three closely related peptides that influence proliferation and numerous physiologic processes in most mesenchymal cells. In this study, Northern blots, immunohistochemistry, TGF beta radioreceptor assays, TGF beta receptor affinity labeling and [3H] thymidine incorporation were used to evaluate whether primary cell cultures of human meningiomas synthesize the three TGF beta isoforms, bear TGF beta receptors, and respond to TGF beta. Transcripts for TGF beta 1 and 2 were detected in the three cases analyzed. Transforming growth factor-beta 1 immunoreactivity was detected in three of six cases, and TGF beta 2 and 3 immunoreactivity were detected in each case analyzed. Media conditioned by cells cultured from six meningiomas also contained latent TGF beta-like activity. Transforming growth factor-beta receptor cross-linking studies identified TGF beta binding sites corresponding to the type 1, type 2, and type 3 receptors on meningioma cells. Treatment with active TGF beta 1 produced a statistically significant reduction in [3H] thymidine incorporation after stimulation with 10% fetal calf serum and epidermal growth factor in all six cases studied.

Blotting, Northern↗