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PubMed1996

Established cell lines transformed by E2F-1 overexpression contain wild-type p53.

Overexpression of genes encoding E2F transcription factors can transform some cultured cell lines and cause apoptosis of others. Apoptosis due to E2F overexpression requires the presence of wild-type p53. Cell lines in which stable E2F overexpression is possible might be expected, therefore, to contain mutant p53. In this report, it was asked whether endogenous p53 was mutant or wild-type in four established fibroblast cell lines that this laboratory previously showed stably overexpressed and were transformed by exogenous E2F-1. Unexpectedly, it was found that the p53 in these cells was wild-type by the criteria of immunoprecipitation with conformation-specific, p53 monoclonal antibodies and by transactivation of a p53-dependent reporter gene construct in transient transfection assays. These data indicate that stable overexpression of E2F-1 is possible in the presence of wild-type p53 and may result in cell transformation.

3T3 Cells↗
PubMed1983

Responses of mouse cell lines transformed by various means to histidinol/cytosine arabinoside treatment.

The responses of the phenotypically-normal BALB/c 3T3 mouse cell line A31 and three of its transformed derivatives, BP-A31 (a benzo(a)pyrene transformant), M-A31 and SV-A31 (Moloney murine sarcomavirus and SV-40 virus transformants, respectively) to L-histidinol and to L-histidinol/cytosine arabinoside (AraC) combinations were investigated. As observed in comparable studies with other normal cell lines, prior treatment of the A31 parental line with L-histidinol led to significant protection from AraC-mediated toxicity. However, in contrast to previous analyses of a number of other transformed cell lines which showed enhanced AraC-mediated toxicity upon prior exposure to L-histidinol, the three types of A31 transformants were afforded varying degrees of protection from AraC when treated with histidinol. These findings support the concept that transformed, tumorigenic cells may retain certain growth properties of their nontumorigenic parental cells.

Animals↗
PubMed1987

[Provirus structure and expression in rat cell lines transformed by the avian sarcoma virus].

Two type of exogenous action on transformed cells have been investigated. The first system includes clones of TWERC cells transformed by Rous sarcoma virus and cultivated in the presence of 5-bromodeoxyuridine. The second system consists of spontaneously transformed rat cells Sam IV superinfected with avian sarcoma virus B-77. In these cell lines and clones the structure of the provirus and its expression have been analyzed by different molecular probes.

Animals↗
PubMed1989

Structural analysis of proviruses in additional hamster tumour cell lines transformed by provirus II rescued from XC cells and definition of a new cell line harbouring amplified proviruses.

Additional 18 Syrian hamster tumour cell lines induced independently with the virus rescued from XC cells (provirus type II) have been analysed by restriction mapping. Taking into account the already published results of an analysis of other six tumour cell lines, altogether 24 tumour cell lines were characterized. In 62.5% of these lines a complete proviral unit has been integrated; 20.8% of the lines harbour altered proviral structures where the 3' end of the gag gene and the entire pol gene had been deleted; 8.3% of the lines carry both such a deleted provirus and a complete provirus. Apart from the already published cryptic provirus found in H-19 cells, no such provirus has been found in another cell line. Therefore the appearance of the cryptic provirus represents an infrequent event (4.16%). Similarly, the significant amplification of proviruses accompanied with a rearrangement in the env gene was found only in one tumour cell line. H-42, in the genome of which five proviral units are accommodated. The probable arrangement of amplified proviruses and the mechanism of their genesis are discussed.

Animals↗
PubMed1996

Constitutive cytokine release by simian T-cell lymphotrophic virus type I (STLV-I) and human T-cell lymphotrophic virus types I/II (HTLV-I/II) transformed cell lines.

Simian T-cell lymphotrophic virus type I (STLV-I) and human T-cell lymphotrophic virus types I/II (HTLV-I/II) contain the tax gene which can transactivate the transcription of viral and cellular genes including several cytokines. These investigations used two STLV-I and four different HTLV-I/II transformed cell lines to quantitate constitutive cytokine release, p24 antigen production, and to correlate gag p24 antigen and cytokine release. These investigations are the first to report 1) quantitative comparison of constitutive release of multiple cytokines by several STLV-I and HTLV-I/II transformed cell lines and to determine the cytokines constitutively released by STLV-I transformed cell lines as IL-6, b-FGF, and GM-CSF (and TNF-beta, and PDGF in a higher viral producing line); 2) statistically significant differences in levels of cytokines produced by STLV-I and HTLV-I/II transformed cell lines, dependent on the method of results quantification; and 3) a correlation between levels of STLV-I and HTLV-I/II and gag p24 antigen production and cytokine production.

Animals↗
PubMed1995

Identification of MIP-1 alpha/LD78 as a monocyte chemoattractant released by the HTLV-I-transformed cell line MT4.

It is known that the HTLV-I-transformed cell line MT4 releases chemotactic activity for monocytes spontaneously. The MT4 monocyte chemoattractant was purified to homogeneity and sequencing of 25 amino acids revealed identity with the C-C chemokine macrophage inflammatory protein-1 alpha (MIP-1 alpha/LD78). An anti-MIP-1 alpha/LD78 rabbit antiserum substantially inhibited chemotaxis of the MT4 chemoattractant. MT4 cells constitutively expressed MIP-1 alpha/LD78 but not the C-C chemokines MCP-1, RANTES, and MIP-1 beta/Act2 and the C-X-C chemokines IL-8, gro alpha, and gro beta. MT4-derived MIP-1 alpha/LD78 was active on monocytes but was a weak chemoattractant for polymorphonuclear leukocytes. Thus, MIP-1 alpha/LD78 is a major monocyte chemoattractant released by HTLV-I-transformed T cells. Expression of MIP-1 alpha/LD78, a leukocyte chemotactic and myelosuppressive molecule, may play an important role in the manifestations of HTLV-I-related diseases.

Amino Acid Sequence↗
PubMed1969

In vitro transformation by the adenovirus-simian virus 40 hybrid viruses. V. Virus-specific ribonucleic acid in cell lines transformed by the adenovirus 2-simian virus 40 and adenovirus 12-simian virus 40 transcapsidant hybrid viruses.

The ribonucleic acid-deoxyribonucleic acid hybridization technique was utilized to determine the presence of adenovirus (ad) and SV40 genetic information and to determine which ad genomes were present in clones of hamster cells transformed with the ad 2-SV40 and ad 12-SV40 transcapsidant hybrid virus populations. The results were correlated with the morphology of the transformed cells and colonies. It was found that cells transformed by either transcapsidant virus which had an SV40 morphology contained the ad 7 and SV40 genomes, whereas cells with a typical ad morphology contained only ad genetic information. Cells and colonies with morphological features of both ad- and SV40-transformed cells contained either the ad 2, or ad 12 genomes, depending on the transcapsidant used, together with the ad 7 and SV40 genomes. The results indicate the following: at least three different events occurred during transformation of hamster cells by the transcapsidant virus populations; the morphology of the resulting clones is determined by the viral genome(s) present; the linkage of the ad 7-SV40 genomes is confirmed since the ad 7- SV40 genomes were never found to be dissociated; the defective ad 7-SV40 genomes are capable of causing transformation; and the transcapsidant particle is probably composed of only ad 7 and SV40 genetic information.

Adenoviridae↗
PubMed1993

Clonal growth and origin of two human keratinocyte cell lines transformed by human papillomavirus type 16 DNA.

Two human keratinocyte cell lines transformed by human papillomavirus type 16, designated Vp and Up, were compared for their clonal growth potential and clonal origin. Up showed greater anchorage-independent growth in soft agar and higher efficiency of single-cell colony formation than Vp (24.3% compared to approximately 10%). The clonal growth potential of these two cell lines was not related to the level of HPV16 gene expression. Fourteen single cell clones of the Vp and 24 of the Up were selected, propagated and analyzed by Southern and Northern blot analysis. Clonal variations existed among subclones of each cell line and between the two cell lines. These variations included cell morphology, growth potential, and expression levels of involucrin (a differentiation marker of keratinocytes) and of HPV16 mRNAs. The Vp and Up cell lines also showed different patterns of HPV16-DNA integration and RNA transcription. However, all subclones of Vp and subclones of Up displayed identical HPV16 DNA integration and RNA expression patterns. The results suggest that both cell lines were monoclonal in origin and that the host genetic factors play an essential role in determining cell clonality.

Cell Differentiation↗
PubMed1985

Human monoclonal antibodies produced by Epstein-Barr virus transformed cell lines bind protein A.

Epstein-Barr virus (EBV) is a polyclonal T-independent activator of viral receptor positive human B lymphocytes. Lymphocytes infected in vitro with the virus are transformed into immortalized cell lines [Nilsson, K, and Klein, G. (1982) Adv. Cancer Res. 37, 319]. In this way human cell lines that secrete specific IgM, IgG and IgA monoclonal antibodies are established. Protein A is also a polyclonal T-independent B cell activator [Langone, J. J. (1982) Adv. Immunol. 32, 157], the targets of which are surface immunoglobulin and C3d receptor positive cells, as are the targets of EBV. We found that almost all (16 out of 17) of the specific monoclonal antibodies (IgM, IgG and IgA) produced in vitro by EBV cell lines bind protein A. Unlike these in vitro produced antibodies, a substantial fraction of the immunoglobulins in human serum does not bind protein A. Thus, those plasma cells which in vivo secrete protein A nonbinding immunoglobulins originate from precursors of B cell that were EBV noninfective. Alternatively, during in vivo B differentiation some immunoglobulins undergo a change from protein A binding to protein A nonbinding molecules.

Adult↗
PubMed1977

[Tumor specific surface antigen in the culture medium of a rat cell line transformed by Rous sarcoma virus].

TSSA is detected on transformed cells by a mixed hemadsorption reaction. The medium of cultures of Rat cells transformed by Rous sarcoma virus (Prague strain, sub-group C) contains a soluble factor which specifically inhibits this reaction. This factor thus possesses the antigenic activity of TSSA which is associated with the presence of a component of molecular weight 42,000 by polyacrylamide gel electrophoresis.

Antigens, Neoplasm↗
PubMed1982

Cell surface properties of HLA antigens on Epstein-Barr virus-transformed cell lines.

A number of monoclonal antibodies have been used to investigate the distributions and rates of lateral motion of the HLA-A,B, and-DR antigens on several Epstein--Barr virus-transformed B-cell lines. The lateral diffusion coefficients (D) of fluorescein conjugates of the monoclonal antibodies bound to the cell surface were determined by fluorescence recovery after pattern photobleaching. Ds of HLA-A and-B were found to be comparable and of the order of 10(-9) to 10(-10) cm2/sec for each of the seven monoclonal antibodies and four cell lines examined. The HLA antigens appear to be monomeric on the cell surface based on experiments using mixtures of arsanilic acid-conjugated and fluorescein-conjugated antibodies. Four monoclonal antibodies against DR antigens were examined. Two of these, Genox 3.53 and L243, labeled the cell surface uniformly and gave Ds comparable to those obtained for the HLA-A and -B antigens. The other two, DA2 and 2.06, rapidly patched on the cell surface and were immobile. The DA2, L243, and Genox 3.53 antibodies bound outside of the caps formed with the arsanilic acid-conjugated 2.06 antibody and a second-step rhodamine-conjugated rabbit anti-arsanilate antibody. This is consistent with recent biochemical evidence that there are multiple distinct antigens coded for by the HLA-DR region.

Antibodies, Monoclonal↗
PubMed1980

Persistence of human adenovirus 5 in human cord blood lymphoblastoid cell lines transformed by Epstein-Barr virus.

Lymphoblastoid cell lines derived from human cord blood leukocytes were persistently infected with human adenovirus 5. These cell lines expressed the Epstein-Barr nuclear antigen, but no other Epstein-Barr virus-related antigen. They continually produced infectious adenovirus 5 particles, but this production could be inhibited by the presence of specific neutralizing antibody to adenovirus 5. This suggests that the persistent infection might be due to the continual reinfection of susceptible cells by complete virus.

Adenovirus Infections, Human↗
PubMedDate not supplied

[Isolation of cell lines transformed by highly oncogenic simian adenovirus SA7 and nononcogenic human adenovirus type 6 and their DNAs].

Methods for generation of cell lines transformed by highly oncogenic simian adenovirus SA7, nononcogenic human adenovirus type 6 and their DNAs are described. WAG rat kidney cells were used for transformation. To produce 1 focus of transformation, 1.7 X 10(6) PFU of SA7 virus is required. Intact and fragmented DNA of both viruses may be quite effectively used for transformation. For production of 1 transformation focus 1.2 microgram SA7 DNA and 1.1 microgram type 6 adenovirus DNA is required. In most cases, DNA fragmentation increases the transforming activity which has been shown to be associated with the left genome region of both viruses under study.

Adenoviridae↗
PubMed1977

Characteristics of a human cell line transformed by DNA from human adenovirus type 5.

Human embryonic kidney cells have been transformed by exposing cells to sheared fragments of adenovirus type 5 DNA. The transformed cells (designated 293 cells) exhibited many of the characteristics of transformation including the elaboration of a virus-specific tumour antigen. Analysis of the polypeptides synthesized in the 293 cells by labelling with 35S-methionine and SDS PAGE showed a variable pattern of synthesis, different in a number of respects from that seen in otheruman cells. On labelling the surface of cells by lactoperoxidase catalysed radio-iodination, the absence of a labelled polypeptide analogous to the 250 K (LETS) glycoprotein was noted. Hybridization of labelled cellular RNA with restriction fragments of adenovirus type 5 DNA indicated transcription of a portion of the adenovirus genome at the conventional left hand end.

Adenoviruses, Human↗
PubMed1979

Characterization of human TK- cell lines transformed to a TK+ phenotype by herpes simplex virus type 2 DNA.

Human TK- cells carrying the HSV-2 TK gene as a result of transformation with virus DNA express a TK activity of virus origin and maintain the TK+ phenotype when grown in HAT medium. Under non-selective conditions, however, reversion to a TK- phenotype occurs with a significant frequency characteristic of each transformed line. Once reversion has occurred the TK- phenotype appears to be stable, since only very rare instances of TK- to TK+ reversion have been observed. TK- revertants were susceptible to re-transformation by virus DNA, but no reactivation of a silent virus TK gene could be obtained by superinfecting them with a TK- virus mutant. The data presented are consistent with the hypothesis that acquisition of the TK- phenotype is brought about by loss of the virus sequences coding for TK.

Cell Line↗
PubMed1990

Generation of cell-mediated cytotoxicity against bovine-papilloma-virus-transformed primary mouse cell lines.

The immunogenicity and immunosensitivity of primary mouse cell lines transformed by bovine papilloma virus 1 (BPV1) DNA were studied in a syngeneic mouse model by determining cell-mediated cytotoxicity in the spleens of mice immunized with the transformed cells. One of the cell lines induced the generation of cell-line-specific Thy1.2-positive cytotoxic effector cells. However, most of the cell lines tested induced the generation of Thy1.2-positive effector cells, which in addition to BPV1-transformed cells were able to lyse a syngeneic cell line transformed by methylcholanthrene. The lysis of BPV1- and methylcholanthrene-transformed cell lines was mediated by recognition of the same antigenic determinants expressed on these cells, and all the BPV1-transformed cell lines were sensitive to lysis by these nonspecific effector cells of the lymphokine-activated killer (LAK) type.

Animals↗