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PubMed1988

Neoplastic transformation of a human bronchial epithelial cell line by a recombinant retrovirus encoding viral Harvey ras.

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

Animals↗
PubMedDate not supplied

Spontaneous neoplastic regression: the significance of apoptosis.

In mammalian cells, neoplastic transformation has a direct relationship with the expression of oncogenes, the production of certain growth factors and with the mutation, loss or simple inactivation of the function of tumor suppressor genes. Genes for suppression of the development of the malignant immunophenotype, as well as inhibitory growth factors have regulatory functions within the normal processes of cell division and differentiation. Telomerase (a ribonucleoprotein polymerase) activation is frequently observed in various types of neoplastic cell transformation. Telomerase activation is regarded as essential for cell immortalization and its inhibition may result in spontaneous regression (SR) of neoplasms. SR of neoplasms occurs when the malignant tumor mass partially or completely disappears without any treatment or as a result of a therapy considered inadequate to influence systemic neoplastic disease. This definition makes it clear that the term SR applies to neoplasms in which the malignant disease is not necessarily cured, and to cases where the regression may not be complete or permanent. A number of possible mechanisms of SR are reviewed, with the understanding that no single mechanism can completely account for this phenomenon. The application of the newest immunological, molecular biological and genetic insights for more individualized anticancer immunotherapy (biotherapy) is also discussed. In conclusion, of all the possible mechanisms of SR of neoplasms, programmed cell death (PCD) or apoptosis is involved in each. The immunological mechanism is probably the main effector mechanism of SR in human neoplasms with its trigger being apoptosis. The treatments of the tumor, such as with various anti-neoplastic drugs or radiation or immunotherapy, all include the basic mechanism of programmed cell death or apoptosis. Without apoptosis, there is practically no tumor regression, none of any kind.

Adult↗
PubMed1995

Multiple mechanisms account for genomic instability and molecular mutation in neoplastic transformation.

Neoplastic cells typically possess numerous genomic mutations and chromosomal aberrations, including point mutations, gene amplifications and deletions, and replication errors. Acquisition of such genomic instability may represent an early step in the process of carcinogenesis. Proteins involved in DNA replication, DNA repair, cell cycle progression, and others are all components of complex overlapping biochemical pathways that function to maintain cellular homeostasis. Therefore, mutational alteration of genes encoding proteins involved in these cellular processes could contribute to genomic instability. Loss of normal cellular mechanisms that guard against genomic mutation and the ensuing genomic instability might lead to accumulation of multiple stable mutations in the genome of affected cells, perhaps resulting in neoplastic transformation when some critical number of transformation-related target genes become damaged. Thus, interactions of fundamental cellular processes play significant roles in sustaining cellular normality, and alteration of any of these homeostatic processes could entrain cells to the progressive genomic instability and phenotypic evolution characteristic of carcinogenesis. Here, we discuss possible molecular mechanisms governing DNA mutation and genomic instability in genetically normal cells that might account for the acquisition of genomic instability in somatic cells, leading to the development of neoplasia. These include (a) molecular alteration of genes encoding DNA repair enzymes, (b) molecular alteration of genes responsible for cell-cycle control mechanisms, and (c) direct molecular alteration of dominantly transforming cellular protooncogenes. We also discuss normal cellular processes involved with DNA replication and repair that can contribute to the mutational alteration of critical genes: e.g., slow repair of damaged DNA in specific genes, and the timing of normal gene-specific replication.

Animals↗
PubMed1990

Oncogenic potential of human herpesvirus-6 DNA.

The ability of human herpesvirus-6 (HHV-6, GS strain) DNA to neoplastically transform established NIH3T3 cells was examined. Transfection of NIH3T3 cells with the intact genomic DNA (170 Kb) or the subgenomic clone pZVH14 containing an 8.7 Kb insert followed by focal or G418 selection resulted in the formation of morphologically transformed cells. When injected subcutaneously into nude mice, these cell lines gave rise to rapidly growing tumors while cells transfected with control vector DNA did not grow in agarose and did not produce tumors in mice. By Southern blot analysis, HHV-6 DNA was detected in the G418 selected primary transfectants and tumor cell lines, but not in the focus derived transformed and tumor cell lines. The data suggest that HHV-6 DNA contains sequences which may contribute to neoplastic transformation, but are not likely to be required for maintenance of transformation.

Animals↗
PubMed2006

Molecular and cellular targets.

Carcinogenesis is a multistage process consisting of initiation, promotion, and progression stages and each stage may be a possible target for chemopreventive agents. A significant outcome of these investigations on the elucidation of molecular and cellular mechanisms is the explication of signal transduction pathways induced by tumor promoters in cancer development. The current belief today is that cancer may be prevented or treated by targeting specific cancer genes, signaling proteins, and transcription factors. The molecular mechanisms explaining how normal cells undergo neoplastic transformation induced by tumor promoters are rapidly being clarified. Accumulating research evidence suggests that many of dietary factors, including tea compounds, may be used alone or in combination with traditional chemotherapeutic agents to prevent or treat cancer. The potential advantage of many natural or dietary compounds seems to focus on their potent anticancer activity combined with low toxicity and very few adverse side effects. This review summarizes some of our recent work regarding the effects of the various tea components on signal transduction pathways involved in neoplastic cell transformation and carcinogenesis.

Biflavonoids↗
PubMedDate not supplied

Human N-myc gene contributes to neoplastic transformation of mammalian cells in culture.

Proto-oncogenes represent a group of eukaryotic genes whose activated forms are implicated in the development of cancer. We have recently identified a human gene, N-myc, that is distantly related to the proto-oncogene c-myc. N-myc is expressed at abnormally high levels consequent to amplification in numerous human neuroblastoma cell lines and metastatic neuroblastoma tumours. In addition, enhanced expression of N-myc, often a result of amplification, has been found in retinoblastoma cell lines and tumours (refs 5, 7 and M.S., unpublished data) and in cell lines derived from small-cell carcinomas of the lung. Here, we show that enhanced expression of N-myc subsequent to co-transfections of an N-myc expression vector and the mutant c-Ha-ras-1(EJ) (from the human bladder carcinoma cell line EJ) is a factor in tumorigenic conversion of secondary rat embryo cells. The transformed cells elicit tumours in athymic mice and isogeneic rats. The ability of N-myc to contribute to neoplastic transformation of cultured mammalian cells raises the possibility that enhanced expression consequent to amplification of N-myc may be a factor in the aetiology of human neuroblastoma.

Animals↗
PubMed1996

[The membrane hetero-organic antigens of tumors of hepatocellular and myogenic origins].

Cell-surface antigens of some tumors and homologous definitive tissues were investigated with organospecific immunoserum against rat kidney membranes using methods of immunofluorescence and enzyme immunoassay. Myogenic cells were also tested to resolve the role of the membrane hetero-organic antigens in the process of proliferation. Membrane hetero-organic antigens, commonly attributed to definitive kidney tissue, were found on the cell surface of rat rhabdomyosarcoma RA-2 and cultured cells of rat hepatomas HTC and 27. However, hetero-organic antigens on the surface of active proliferating myogenic cells were not found. It is concluded that membrane hetero-organic antigens, usually attributed to definitive kidney tissue, represent one of characteristic manifestations of neoplastic cell transformation rather than results of intensive proliferation of the cells.

Animals↗
PubMed1980

Inhibition of chemically induced carcinogenesis of canine cells in vitro by infection with mouse xenotropic type C virus.

C57L mouse xenotropic type C virus infection inhibited N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced in vitro transformation of embryo cells from inbred beagles. Treatment with MNNG induced in vitro neoplastic transformation in uninfected canine cells but not in C57L virus-infected canine cells; the C57L virus-infected canine cells not treated with MNNG also remained untransformed. In this dog cell system, preinfection with a C57L mouse xenotropic type C virus inhibited in vitro neoplastic transformation induced by MNNG.

Animals↗
PubMed1988

Neoplastic transformation of osteogenic cells: quantitative morphometric analysis of an in vitro model for osteosarcoma.

Previously we have reported the development of a model in vitro system for the study of osteosarcoma. In this system, when chick periosteal explants are infected with Fujinami sarcoma virus (FSV), osteosarcoma-like tissue is formed. In the present study, a series of histopathologic parameters of neoplastic transformation and osteogenesis were quantitated, at a single cell level, by computer-assisted morphometry. Most significantly, it was found that compared to uninfected (control) cultures, in the FSV-infected (experimental) cultures, the bone to osteoid ratio per unit area was decreased due to a relative decrease in the area of bone and an increase in the area of osteoid. The cellularity of the FSV-infected tissues was significantly increased due to an increase in the number of unlabeled and [3H]thymidine-labeled cells, while the proportion of alkaline phosphatase (AP) positive cells decreased. Double-label immunohistochemistry (with anti-P140gag-fps) and histochemistry for AP activity was performed, to demonstrate production of the oncogene-encoded protein, and osteoblastic differentiation respectively. In an in vitro transformation assay, single cells derived from control, uninfected cultures did not grow, while those derived from FSV-infected cultures formed colonies in semisolid medium. Some of these colonies demonstrated AP staining. Taken together these data show that in this in vitro system (i) neoplastic transformation of osteogenic cells does occur, (ii) changes in osteoid and bone production are related to neoplastic transformation, and (iii) osteosarcoma-like changes can be quantitated at the individual cell level.

Animals↗
PubMed2005

Stepwise neoplastic transformation of a telomerase immortalized fibroblast cell line.

We have described recently a human fibroblast cell line immortalized through ectopic telomerase expression (cen3tel), in which the extension of the life span was associated with the appearance of chromosomal aberrations and with the ability to grow in the absence of solid support. As reported in this article, on further propagation in culture, cen3tel cells became neoplastically transformed, being able to form tumors in nude mice. The analysis of the cells, during the gradual transition toward the tumorigenic phenotype, allowed us to trace cellular and molecular changes associated with different phases of transformation. At the stage in which they were able to grow in agar, cen3tel cells had lost contact growth inhibition but still retained the requirement of serum to proliferate and were not tumorigenic in immunocompromised mice. Moreover, they showed a down-regulation of the INK4A locus and were resistant to oncogenic Ras-induced senescence but still retained a functional p53. Subsequently, cen3tel cells became tumorigenic, lost p53 function because of a mutation in the DNA-binding motif, and overexpressed c-myc. Interestingly, tumorigenic cells did not carry activating mutations either in the ras proto-oncogenes (H-ras, N-ras, and K-ras) or in B-raf. Cen3tel cells gradually became hyperdiploid but did not display centrosome abnormalities. To our knowledge, cen3tel is the first telomerase immortalized fibroblast line, which became neoplastically transformed. In this system, we could associate a down-regulation of the INK4A locus with anchorage-independent growth and with resistance to Ras-induced senescence and link p53 mutations and c-myc overexpression with tumorigenicity.

Animals↗
PubMed1986

Enhanced protein phosphorylation of carcinogen-initiated 10T1/2 cells accompanies their neoplastic transformation.

Retinyl acetate (RAC) prevents neoplastic transformation of carcinogen-exposed C3H/10T1/2 C18 cells, and has allowed the isolation of cells having the properties expected of initiated cells. After removal of RAC from logarithmically growing initiated cells, cultures first become confluent and growth arrested, as occurs with their normal counterparts. This is followed by an increase in thymidine labelling index and finally by morphological transformation on days 15 and 23, respectively, after seeding and drug removal. The increase in labelling index is the earliest indication yet seen of transformation taking place in these cultures. Phosphorylation of three nonionic detergent-soluble proteins was observed to be correlated with the increase in labelling index. Using two-dimensional gel electrophoresis, a protein of 35 kd (pp35(1)) and one of 38 kd (pp38) were seen to become more heavily phosphorylated in association with the increase in labelling index. A second protein of 35 kd (pp35(2)) was only detected in isolated transformed cells and is phosphorylated in an alkali-resistant manner consistent with phosphorylation of tyrosine residues. Alkali-resistant phosphorylation of pp35(2)) could be eliminated in transformed cells by treatment with RAC. Phosphorylation of pp35(1)) appears to be a permanently acquired characteristic of these cells, and cannot be made to revert. Phosphorylation of pp38, as indicated by isoelectric point, is reduced by RAC treatment. These studies implicate changes in protein phosphorylation in loss of growth control, and suggest that the cancer chemopreventive action of retinoids may also be mediated at this level.

Animals↗
PubMed2003

12-O-tetradecanoylphorbol-13-acetate and UV radiation-induced nucleoside diphosphate protein kinase B mediates neoplastic transformation of epidermal cells.

The molecular changes associated with early skin carcinogenesis are largely unknown. We have previously identified 11 genes whose expression was up- or down-regulated by 12-O-tetradecanoylphorbol-13-acetate (TPA) in mouse skin keratinocyte progenitor cells (Wei, S.-J., Trempus, C. S., Cannon, R. E., Bortner, C. D., and Tennant, R. W. (2003) J. Biol. Chem. 278, 1758-1768). Here, we show an induction of a nucleoside diphosphate protein kinase B (NDPK-B) gene in response to TPA or UV radiation (UVR). TPA or UVR significantly induced the expression of NDPK-B both in vivo hyperplastic mouse skin and in vitro mouse JB6 Cl 41-5a epidermal cells. Indeed, this gene was also up-regulated in TPA or UVR-mediated skin tumors including papillomas, spindle cell tumors, and squamous cell carcinomas, relative to adjacent normal skins. Functional studies by constitutive expression of nm23-M2/NDPK-B in TPA susceptible JB6 Cl 41-5a and TPA-resistant JB6 Cl 30-7b preneoplastic epidermal cell lines showed a remarkable gene dosage-dependent increase in foci-forming activity, as well as an enhancement in the efficiency of neoplastic transformation of these cells in soft agar but no effect on proliferation in monolayer cultures. Interestingly, stable transfection of the nm23-M2/NDPK-B del-RGD or G106A mutant gene in JB6 Cl 41-5a cells selectively abrogated NDPK-B-induced cellular transformation, implicating a possible Arg105-Gly106-Asp107 regulatory role in early skin carcinogenesis.

Animals↗
PubMed1979

Neoplastic transformation of cultured Syrian hamster embryo cells by DNA of herpes simplex virus type 2.

Syrian hamster embryo cells were transformed to a neoplastic phenotype after exposure to herpes simplex virus type 2 (S-1) DNA at concentrations (less than or equal to 0.01 microgram per 60-mm dish) at which infectivity was no longer demonstrable. Transformed cells manifested in vitro phenotypic properties characteristic of the neoplastic state, expressed herpes simplex virus-specific antigens, and induced invasive tumors in vivo. Transfection and transformation of Syrian hamster embryo cells with herpes simplex virus type 2 DNA or its fragments is a suitable system for investigating the structure and function of herpes simplex virus-transforming gene(s).

Animals↗
PubMed1982

Human proteins sensitive to neoplastic transformation in cultured epithelial and fibroblast cells.

We resolved the [35S]methionine polypeptides synthesized by normal [lung fibroblasts (WI-38), amnion cells] and transformed [SV40 transformed WI-38, AMA (spontaneously transformed amnion cells)] cultured human cells, using two-dimensional gel electrophoresis under conditions in which about 1300 polypeptides could be reproducibly separated. These studies demonstrated important changes in the relative proportions of several polypeptides that are present both in normal and transformed cells. Of a total of 400 common polypeptides that we quantitated for each cell type, 53 (22 basic and 31 acidic) varied by 40% of more in both cell pairs. Among these, we have identified vimentin (IEF 26), cyclin (IEF 49), and a tropomyosin-related polypeptide (IEF 52). No new major polypeptide was detected in the transformed cells, at least at the level of resolution currently achieved by this technique. Similar but qualitative studies of [32P]orthophosphate-labeled proteins revealed that, of 250 analyzed, only seven common phosphoproteins, including phosphovimentin (IEF 26e), varied consistently in both cell pairs. These results strengthen our previous conclusion that transformation results in changes in the relative proportions of polypeptides synthesized in normal and transformed cells rather than in the appearance of new polypeptides in transformed cells.

Amnion↗
PubMed1983

Carcinogen-induced phenotypic alterations in mammary epithelial cells accompanying the development of neoplastic transformation.

Epithelial cells isolated from the mammary glands of virgin Sprague-Dawley rats and treated with 7,12-dimethylbenz[a] anthracene (DMBA) acquire an indefinite life span and anchorage-independent (AI) growth and form carcinomas in athymic nu/nu mice. Epithelial cells separated from fibroblasts and lipocytes by density-gradient centrifugation after collagenase digestion of the fat pads are grown in a hormone-supplemented medium. Control mammary epithelial cells survived approximately 30 days. After 2 days in culture, the mammary epithelial cells were treated with DMBA (1 microM) for 24 hr allowing for maximum oxidative metabolism of the hydrocarbon. DMBA-treated cells acquired an extended life span and grew in AI medium; however, in most cases, they were nontumorigenic and eventually ceased dividing. A pool of mammary epithelial cells, ME 10CL1, treated with DMBA has grown indefinitely, exhibited AI growth, and after 195 days in culture formed adenocarcinomas when 5 X 10(6) cells were injected into athymic nu/nu mice. When the tumor promoter, 12-O-tetra-decanoylphorbol-13-acetate (100 ng/ml), was added to another pool (ME 11CL2) of DMBA-treated mammary epithelial cells which had been in culture for 110 days, an irreversible increase in cell growth rate and a significant morphological alteration resulted. The 12-O-tetradecanoylphorbol-13-acetate-treated cells also formed colonies in AI medium after 140 days and poorly differentiated carcinomas in athymic nu/nu mice. Inhibition of tumor cell proliferation by tamoxifen is consistent with the mammary origin of the epithelial cells and suggests the presence of a viable estrogen receptor. The results demonstrate in vitro neoplastic transformation of rat mammary epithelial cells by DMBA or promotion of DMBA-initiated cells by 12-O-tetradecanoylphorbol-13-acetate resulting in two different epithelial tumor cell lines.

9,10-Dimethyl-1,2-benzanthracene↗