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PubMed1988

Anti-tumor surveillance of non-contact-inhibited transformed cell lines.

In order to determine if the correlated expression of transformation and tumorigenicity is affected by the agents used to induce transformants or by the immune status of the host used to test the tumorigenicity of transformants, we derived a series of cloned cell lines from foci of transformed cells induced by treatment of the contact-inhibited mouse cell line B/C-N7.ICI with the DNA demethylating agent 5-azacytidine (5-AZC) or the DNA demethylating and mutating agent benzo(a)pyrene dihydrodiol epoxide (BPDE). The transformed cell lines were injected into syngeneic nude and normal mice to determine their tumorigenicity. The results of this analysis showed that 93% of the transformants induced by 5-AZC treatment grew as tumors when injected into nude mice. Of those lines capable of growing as tumors in nude mice, 86% were also tumorigenic when injected into normal mice. In contrast, only 64% of BPDE-induced transformants grew as tumors in nude mice, and of those, only 44% were also tumorigenic in normal mice. The existence of non-contact-inhibited transformants that are tumorigenic only in nude mice indicates that host anti-tumor immune surveillance mechanisms are operative in normal mice. Further, the difference in both the percentage of transformed cell lines that are tumorigenic and the percentage of tumorigenic transformants that are susceptible to immune surveillance when transformants are induced by BPDE as compared to 5-AZC indicates that the transforming agent can affect both the correlation between the expression of transformation and tumorigenicity, and the interaction between the immune system and tumorigenic transformants.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1978

Lysosomal acid hydrolases in established lymphoblastoid cell lines, transformed by Epstein-Barr virus, from patients with genetic lysosomal storage diseases.

Lysosomal acid hydrolases were determined in established lymphoblastoid cell lines, transformed in vitro by Epstein-Barr virus (EBV) from lymphocyte-rich cell populations isolated from the peripheral blood of patients with genetic lysosomal storage diseases--Hurler syndrome, Scheie syndrome, GM1-gangliosidosis type 1 and type 2, Tay-Sachs disease, and I-cell disease--and from obligate heterozygotes for these diseases. The respective enzyme activity was undectectable in lymphoblastoid cells from the patients, but not from controls. Obligate heterozygotes could not always be distinguished from controls in lymphoblastoid cells as well as in leukocytes. These results suggest that established lymphoblastoid cell lines are useful material for the enzymatic study of genetic lysosomal storage diseases.

Cell Line↗
PubMed1981

Release of glycosyltransferase and glycosidase activities from normal and transformed cell lines.

The release of galactosyltransferase, sialyltransferase, and several glycosidase activities into the growth media from several normal and transformed cell lines was examined. Six of the seven cell lines released galactosyltransferase into their culture media. Only the human leukemia CCRF-CEM cells failed to release demonstrable galactosyltransferase activity. Release of galactosyltransferase activity into the media closely paralleled the growth curves for all but the BHKpy cells. These cells continued to release peak levels of galactosyltransferase activity into the culture media after their growth had plateaued. Media galactosyltransferase activity was unaffected by Triton X-100 treatment had remained in the supernatant fraction of a 100,000 X g, 12-hr centrifugation, suggesting that the cells release galactosyltransferase in a soluble form. In contrast to galactosyltransferase activity, only one of the cell lines (L1210) released sialyltransferase activity in appreciable amounts. Even this level of activity was 20-fold less than that observed for galactosyltransferase in the media from L1210 cells. Of the nine glycosidase activities assayed, only N-acetylglucosaminidase was observed in significant amounts in the media from all but the CCRF-CEM cells. However, N-acetylglucosaminidase release did not correlate closely with cell growth. These findings suggest a relatively specific release of galactosyltransferase and N-acetylglucosaminidase activities by cells in tissue culture. Moreover, the release of galactosyltransferase closely parallels cell growth. The significance of these released enzymes, especially to cell growth, has yet to be determined.

Acetylglucosaminidase↗
PubMed1982

Erythroblast cell lines transformed by a temperature-sensitive mutant of avian erythroblastosis virus: a model system to study erythroid differentiation in vitro.

A continuous chicken erythroblast cell line transformed by the temperature-sensitive mutant ts34 of avian erythroblastosis virus was developed. This cell line, designated HD3, could be induced to terminally differentiate by shift to the nonpermissive temperature. The differentiated cells resembled erythrocytes as judged by morphology, expression of hemoglobin as determined by benzidine staining and radioimmunoassay, and by the expression of differentiation-specific cell surface antigens. Terminal differentiation was dependent on an erythropoietin-like activity present in anemic chicken serum. In contrast, induction of differentiation in the same cells by butyric acid was erythropoietin independent and did not lead to the formation of erythrocytes. In addition, we found that the responsiveness to temperature inducibility and to butyric acid could be dissociated in variant sublines of HD3 and that both types of differentiation inducers appear to act via different pathways.

Alpharetrovirus↗
PubMed1983

Characterization of exogenous proviral sequences in hamster tumor cell lines transformed by Rous sarcoma virus rescued from XC cells.

Alterations in viral structural genes have been studied in five cell lines derived from Syrian hamster tumors which had been induced by the virus rescued from XC cells by transfection. Two cell lines, H-18 and H-20, have all the viral structural genes expressed, but a new EcoRI recognition site appeared in the region of the pol gene sequence. Provirus present in H-12 lacks the 3' part of the gag gene sequences as well as the pol gene, therefore, it gives rise to an anomalous 1.8 Md EcoRI fragment. This line also does not synthesize viral RNA of genomic size, and none of the subgenomic RNAs found hybridized with the DNApol probe. The H-19 cell line harbors only the src gene and LTR sequences, the U3 part of which seems incomplete or different from that of PR-RSV. The cryptic proviral structure in H-19 is transcribed into src mRNA. The degree of transcription of the src gene is about 25 viral RNA equivalents per cell. The H-9 cells harbor the complete provirus and, in addition, proviral structures having the deletion in gag-pol genes. The possible ways of development of provirus alterations and the role of cryptic proviral sequences in oncogenesis are discussed.

Animals↗
PubMed1986

Characterization of two related Epstein-Barr virus-encoded membrane proteins that are differentially expressed in Burkitt lymphoma and in vitro-transformed cell lines.

Two related but differentially expressed potential membrane proteins of Epstein-Barr virus are encoded by the same reading frame in the EcoRI D het region of the viral genome. Potential antigenic sites in the amino acid sequence of these proteins were selected by computer-aided prediction of the secondary structure and two oligopeptides corresponding to regions located in different parts of the proteins were synthesized chemically. Rabbit antisera to these peptides were used for immunoprecipitation of the native viral proteins from Epstein-Barr virus-positive cell lines from various sources. Both predicted membrane proteins could be precipitated from cell lines that had been transformed in vitro with EBV or from cell lines derived from infectious mononucleosis patients. In cell lines established from Burkitt lymphoma, only the smaller polypeptide, which lacks 138 amino acids from the amino terminus, could be identified. Using the synthetic peptides as antigens in ELISA, we detected elevated antibody titers in sera from patients with infectious mononucleosis and nasopharyngeal carcinoma.

Amino Acid Sequence↗
PubMed1980

Transcription of the viral genome in cell lines transformed by simian virus 40. I. Mapping of virus-specific nuclear RNAs.

Mapping of virus-specific nuclear transcripts was carried out in three lines of rat cells transformed by SV40. Each of these cell lines contained a single copy of integrated viral DNA with identified regions adjacent to cell DNA (1). The main virus-specific nuclear transcript in all of these cell lines was shown to be complementary to the minus strand of the early region in SV40 genome. Each cell nucleus contained approximately 50 copies of these RNAs. Transcripts complementary to both strands of the late region in viral genome were also detectable in all of these cell lines. Its content varied depending on the cell line and was 20-50-fold less than that of the main virus-specific transcript. All the regions of integrated SV40 genome in isolated nuclei of transformed cells were equally sensitive to pancreatic DNase I treatment suggesting that the whole viral genome served as a template for RNA synthesis in these cell lines.

Animals↗
PubMed1991

Isolation of cellular revertants from a rat cell line transformed by the E6 and E7 genes of human papillomavirus type 16.

Three revertants defective in the ability to form colonies in semisolid medium were isolated from a rat cell line transformed by the E6 and E7 genes of human papillomavirus type 16 (HPV16). These revertants appeared to be defective in a cellular factor(s) necessary for transformation by HPV16-E6E7 genes since they still expressed a comparable amount of HPV16-E6E7 mRNA and E7 protein to the parental cells, harbored rescuable transforming virus, and were resistant to retransformation by HPV16-E6E7 genes. All these reverted phenotypes of the three mutants were recessive on somatic cell hybridization with normal cells, because all the hybrids showed transformed phenotypes.

Animals↗
PubMed1997

Expression of estrogen receptors in a normal human breast epithelial cell type with luminal and stem cell characteristics and its neoplastically transformed cell lines.

Although approximately two-thirds of breast cancers are estrogen receptor (ER)-positive, only a small proportion of epithelial cells in the mammary gland express the ER. The origin of the ER-positive breast cancers is unknown. Recently, we have developed a culture method to grow two morphologically and antigenically distinguishable types of normal human breast epithelial cells (HBEC) derived from reduction mammoplasty. In this report, we studied the expression of ER in these two types of cells and their transformed cell lines. The results indicate that Type I HBEC with luminal and stem cell characteristics expressed a variant ER (approximately 48 kd) by Western blot analysis. This variant ER contains a deletion in the DNA binding domain (exon 2) as revealed by RT-PCR analysis. The lack of the DNA-binding domain of the variant ER was also confirmed by the ER-estrogen responsive element binding assay, as well as by the immunofluorescence staining of the ER using anti-ER antibodies which recognize either the C-terminal or N-terminal region. In contrast, Type II HBEC with basal epithelial phenotype are ER-negative. Simian virus 40 (SV40) transformed Type I and Type II HBEC lines also expressed the variant ER. Tumors formed in athymic nude mice by in vitro transformed tumorigenic Type I cell lines, however, expressed a high level of wild type ER which was undetectable in these cells grown in vitro before and after tumor formation. Thus, there appears to be a differential ER mRNA splicing between the in vitro and in vivo mileu.

Adult↗
PubMed1979

Establishment and characterization of Indian muntjak cell lines transformed with simian virus 40.

Kidney cells of an Indian muntjak were transformed with simian virus 40 (SV40). The transformation efficiency of the tertiary cultures was very high when estimated by the agar suspension culture method. The efficiency was about 0.015% when infected at an input multiplicity of 0.4 p.f.u./cell. Clonal cell lines were established from the colonies in soft agar medium. Most of the cell lines and their subclones produced a small amount of infectious SV40. The SV40 virion antigen-positive cells in a clone increased from 0.2% to about 40% by the treatment with mitomycin C. More than 70% of the cells in two cell lines were normal in G- and C-banded karyotypes, indicating that chromosomal change is not a necessary step in the process of transformation of the Indian muntjak cells with SV40.

Animals↗
PubMed2006

The use of monoreassortants and reverse genetics to map reovirus lysis of a ras-transformed cell line.

Reovirus has been shown to lyse most transformed cells while establishing a persistent or abortive infection in non-transformed cells. Developing methods to identify the reovirus genes associated with oncolysis is an important step toward understanding the mechanisms involved. This report is the first to develop and apply the use of monoreassortants and reverse genetics to identify an individual reovirus gene associated with reovirus oncolysis. Infection with reovirus serotypes 1/Lang, 2/Jones or 3/Dearing of cells transformed with a normal copy of c-Ha-RAS (N1 cells) or with a normal copy of c-Myc (Myc-3 cells), produces large amounts of progeny virus of all three serotypes and results in lysis of both these cell lines. Infection of cells transformed with a mutant c-Ha-RAS gene (T1 cells) with either serotype 1/Lang and 2/Jones results in the production of large amounts of virus and lysis of the cells. In sharp contrast, serotype 3/Dearing virus infection of these cells produced small amounts of virus and resulted in limited lysis of these cells. Using monoreassortants and reverse genetics we exploited this phenotypic difference between the three serotypes to identify a single reovirus gene linked to the preferential lysis of the T1 cells, the S4 gene.

Cell Line, Transformed↗
PubMed1984

Morphological correlates of transformation in cultured C3H/10T1/2 mouse embryo cells.

In efforts to determine common and consistent morphological parameters of transformation in C3H/10T1/2 cells, 15 cell lines transformed by different carcinogens were examined with the scanning electron microscope (SEM) and compared to non-transformed cells. Cell lines were studied at different passages, at different cell densities, and after growth as anchorage dependent or independent cultures. The transformed cell lines could be distinguished in the SEM from non-transformed cultures by the expression of one or more of the following morphological characteristics: formation of mini- or macro-foci (random piling of cells on top of each other), pleiomorphism in cell size and shape, and cell surface complexity. The extent to which these characteristics were expressed varied widely in the different transformed cell lines. Light microscopic scoring for different types of foci also revealed broad variability among the different transformed lines. At the SEM level, cell lines could not be characterized as transformed on an individual cell basis. However, all transformed cell lines could be definitively characterized as transformed on a population basis due to the presence of mini-foci. The various transformed cell lines were classified semi-quantitatively into categories based on the extent of expression of the different morphological characteristics. There was broad correspondence between the morphological classification and the relative plating efficiencies of the cell lines in soft agarose.

Animals↗
PubMedDate not supplied

[Characteristics of rat kidney cell lines transformed by the DNA of human adenovirus type 6].

The data on the transforming activity of intact DNA of human adenovirus type 6 and that fragmented by restrictases Bam H I (31.3% of the genome), Bgl 2 (9.3% of the genome), and Hind 3 (7.6% of the genome) in a primary culture of rat kidney cells are presented. The activity of the specimens varied within 1.1-2.1 foci per 1 microgram of DNA. From the transformation foci 5 cell lines were derived and their properties (T-antigen production, integration of adenovirus genome, phenotypic features) were studied.

Adenoviruses, Human↗
PubMed1985

Selective cytotoxicity of AIDS virus infection towards HTLV-I-transformed cell lines.

Previously, we reported that cells of the human T-cell lymphotropic virus type I (HTLV-I)-transformed lines MT-2 and MT-4 were extensively killed by infection with AIDS retrovirus HTLV-III. We have investigated this phenomenon more systematically using light and electron microscopy as well as immunofluorescence. The cell lines used in the present studies included 14 of those carrying not only human HTLV-I but also related simian agents and 6 HTLV-I-negative T- and B-cell lines. The results showed that the cytocidal effects occurred in the HTLV-I-transformed cell lines exclusively and were not present in further subcultures. In these cell lines the cytotoxic response was closely correlated with the induction of HTLV-III antigens after virus infection. However, cells of 6 HTLV-I-free lines were not killed to a marked extent by HTLV-III and were passaged as continuous producers of AIDS virus. Only 2 cell lines were resistant to the cytocidal effect of HTLV-III among 14 HTLV-I carrying cell lines. They were also resistant to the replication of infected HTLV-III. This AIDS virus-specific cytotoxic effect observed in HTLV-I-transformed cell lines did not appear to be associated with gene expression of the gag and pXs region of HTLV-I genomes. This result may indicate that HTLV-III specifically interferes with some steps of HTLV-I transformation.

Acquired Immunodeficiency Syndrome↗