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At least 19 recordsLinked to original sources
PubMed1978

Growth control in simian virus 40-transformed rat cells: temperature-independent expression of the transformed phenotype in tsA transformants derived by agar selection.

Fisher rat fibroblasts (FR 3T3), transformed with the tsA30 mutant of simian virus 40 and selected by colony formation in soft agar, maintained the transformed phenotype at high temperature, whereas most transformants isolated from foci were found to undergo a phenotypic reversion toward the normal state in their saturation density, ability to grow in soft agar, and rate of 2-deoxyglucose transport. The temperature-independent phenotype observed in agar-selected transformants was not due to a reversion of the viral mutation. These results, similar to those previously obtained with polyoma virus tsa mutants, further suggest that two distinct mechanisms may operate in both cases for maintaining the transformed phenotype. Immunofluorescence studies suggested a different regulation of T antigen synthesis in these two classes of transformants.

Agar↗
PubMed1978

Expression of transformation in cell hybrids. II. Nonsuppression of the transformed phenotype in hybrids between a chemically transformed and nontransformed derivatives of Balb/3T3.

Hybrid clones derived from a nitrosocarbaryl-transformed Balb/3T3 cell line, Clone H, and a nontransformed cell line THO2 resemble the transformed parent in the clone morphology, higher saturation density, colony formation in medium with reduced serum concentration, growth in agarose and ability to form clones on Balb/3T3 monolayer. Results are discussed in the framework of genetic models which permit or require dominant mutations for the expression of transformed phenotype.

Animals↗
PubMed1978

Transformation of BALB/c-3T3 cells by tsA mutants of simian virus 40: temperature sensitivity of the transformed phenotype and retransofrmation by wild-type virus.

The function of the A gene of simian virus 40 (SV40) in transformation of BALB/c-3T3 cells was investigated by infecting at the permissive temperature with wild-type SV40 and with six tsA mutants whose mutation sites map at different positions in the early region of the SV40 genome. Cloned transformants were then characterized as to the temperature sensitivity of the transformed phenotype. Of 16 tsA transformants, 15 were temperature sensitive for the ability to overgrow a monolayer of normal cells, whereas three of three wild-type transformants were not. This pattern of temperature sensitivity of the transformed phenotype was also observed when selected clones were assessed for the ability to grow in soft agar and in medium containing low concentration of serum. The temperature resistance of the one exceptional tsA transformant could be attributed neither to the location of the mutation site in the transforming virus nor to transformation by a revertant virus. This temperature-resistant tsA transformant, however, was demonstrated to contain a higher intracellular concentration of SV40 T antigen than a temperature-sensitive line transformed by the same tsA mutant. A tsA transformant displaying the untransformed phenotype at the nonpermissive temperature was found to be susceptible to retransformation by wild-type virus at this temperature, demonstrating that the temperature sensitivity of the tsA transformants is due to the viral mutation and not to a cellular defect. These results indicate that continuous expression of the product of the SV40 A gene is required to maintain the transformed phenotype in BALB/c-3T3 cells.

Animals↗
PubMed1978

Monovalent antibodies directed to transformation-sensitive membrane components inhibit the process of viral transformation.

Monovalent antibodies (Fab) directed to two classes of transformation-sensitive cell surface components, ganglioside and galactoprotein a (Gap a), inhibit the process of oncogenic viral transformation of cells. Mouse 3T3 cells infected with murine sarcoma virus were not transformed in terms of morphology change and enhancement of sugar uptake when the infected cells were cultured in the presence of monovalent antibodies directed to GM(1) ganglioside or to Gap a. Transformation inhibitory activity of these cell surface ligands was not related to cell growth inhibition because the monovalent antibodies to globoside and divalent Con A were growth inhibitory but did not inhibit oncogenic transformation. Neither anti-GM(1) Fab nor anti-Gap a Fab inhibited virus production. The transformation inhibitory activity of antiganglioside and anti-Gap a Fab was additionally assessed by inhibiting the transformed phenotype in NRK cell lines with mutants of avian sarcoma virus that are temperature sensitive for expression of the transformation phenotype (NRK/LA25). In this cell line, the GM(3) ganglioside (not GM(1)) and Gap a were transformation-sensitive cell surface components. The expression at permissive temperature of transformed phenotypes, such as morphology change and capability of growth in 0.3% agar, was inhibited by preincubation of the cells with anti-GM(3) Fab or anti-Gap a Fab.GM(3) labeling of NRK/LA25 cells decreased at permissive temperature, whereas preincubation of cells with anti-Gap a, which induces the inhibition of transformation after a temperature shift, prevented the decline of GM(3) label on the cell surface. The data suggest a possible correlation between GM(3) and Gap a expression. Application of monovalent antibodies to these transformation-sensitive components may prevent changes of these components on cell surfaces, and thus may result in abortion of phenotypic expression of transformation, although the transforming gene (src) has been set active. These results indicate that pericellular structures influence gene expression.

Antigen-Antibody Reactions↗
PubMed1979

Simian virus 40 small t antigen is not required for the maintenance of transformation but may act as a promoter (cocarcinogen) during establishment of transformation in resting rat cells.

Simian virus 40 deletion mutants affecting the 20,000-dalton (20K) t antigen and tsA mutants rendering the 90K T antigen temperature sensitive, as well as double mutants containing both mutations, induced host DNA synthesis in resting rat cells at the restrictive temperature. Nonetheless, the deletion mutants and double mutants did not induce transformation in resting cells even at the permissive temperature. On the other hand, the deletion mutants did induce full transformants when actively growing rat cells were infected; the transformants grew efficiently in agar and to high saturation densities on platic. The double mutants did not induce T-antigen-independent (temperature-insensitive) transformants which were shown previously to arise preferentially from resting cells. Thus, small t antigen was dispensable for the maintenance of the transformed phenotype in T-antigen-dependent rat transformants (transformants derived from growing cells) and may play a role in the establishment of T-antigen-independent transformants. We attempt to establish a parallel between transformation induced by chemical carcinogens and simian virus 40-induced transformation.

Animals↗
PubMed1979

Effects of nucleoside analogs on Epstein-Barr virus-induced transformation of human umbilical cord leukocytes and Epstein-Barr virus expression in transformed cells.

Two methods of assay, measuring (i) stimulation of host cell DNA synthesis by [(3)H]thymidine incorporation and (ii) morphological transformation in microtiter plates, were employed to determine what effect treatment during infection with adenine arabinoside or 5-iodo-5'-amino-2',5'-dideoxyuridine has on Epstein-Barr virus (EBV) (B95-8)-induced transformation of human umbilical cord leukocytes. It was found that adenine arabinoside inhibited EBV-induced transformation in a dose-dependent manner in both assays, beginning at drug concentrations (<2 mug/ml) which had little effect on either spontaneous or phytohemagglutinin-induced host cell DNA synthesis. Adenine arabinoside was more effective in inhibiting morphological transformation than EBV-induced host DNA synthesis. Adenine arabinoside treatment was also effective in reducing both EB viral capsid antigen expression and production of biologically active extracellular transforming virus in EBV-transformed cells. In contrast, 5-iodo-5'-amino-2',5'-dideoxyuridine, which inhibited herpes simplex virus replication, had little effect on EBV-induced transformation as measured by either method of assay. However, 5-iodo-5'-amino-2',5'-dideoxyuridine was found to be effective in inhibiting viral capsid antigen expression and production of extracellular transforming virus in EBV-transformed cells.

Cell Transformation, Viral↗
PubMed1978

Transformation of normal diploid cells by isolated metaphase chromosomes of virus-transformed or spontaneous tumor cells.

Normal diploid human cells with a limited life-span in culture, as well as primary or secondary cell cultures of mouse or rat embryos, can be transformed in vitro (i.e. grow in soft-agar or low-serum medium) after a single exposure to metaphase chromosomes from SV40-transformed human or rat cells, Ad5-transformed human cells and several spontaneous human or mouse tumor cells. Chromosomes from normal diploid cells do not show any such transforming activity. As judged from the number of colonies formed in selective medium, the efficiency of transformation is, with some exceptions, of the order of 10(-5)--10(-6) and is generally higher for homologous than for heterologous transfers. A fraction of the colonies demonstrate abortive transformation. Nevertheless, using chromosomes from all but one donor cell population, at least one transferent cell line expressing a stable transformed phenotype has been established. Our results demonstrate that transformation of normal diploid cells by a presumptive chromosome-mediated gene transfer can be obtained with a variety of donor and recipient cells.

Adenoviridae↗
PubMed2026

Genomic Profiling, Risk Stratification, and Post-Transformation Treatment Outcomes in Patients with Transformed Small-Cell Lung Cancer: A Multicenter Analysis.

BACKGROUND: Transformed small-cell lung cancer (T-SCLC) is an increasingly recognized resistance mechanism in EGFR-mutant lung adenocarcinoma. This study aimed to identify early predictors of histologic transformation and evaluate post-transformation treatment outcomes. METHODS: We retrospectively collected 163 T-SCLC patients from five Chinese centers. Next-generation sequencing was performed on 60 EGFR-mutant patients, including 47 paired primary-transformed samples. Integrated genomic and clinical analyses were conducted to delineate molecular features and survival outcomes. RESULTS: Among 150 EGFR-mutant patients, the median time to SCLC transformation was 25.8 months and median post-transformation overall survival (OS) was 14.2 months. Clinical and survival data for the 13 EGFR wild-type patients are reported descriptively given the limited sample size. Among 108 treatment-evaluable patients, first-line EGFR-TKI plus chemotherapy, chemotherapy alone, and immune checkpoint inhibitors (ICIs) plus chemotherapy yielded median progression-free survival (PFS) of 6.2, 5.30, and 4.07 months (P = 0.041) and median OS of 21.2, 27.6, and 13.6 months (P = 0.193). In later-line therapy, taxane-based regimens achieved a median PFS of 6.93 months, outperforming camptothecin-based (1.13 months) and other regimens (1.90 months; P = 0.049). High evolutionary diversity was associated with shorter post-transformation OS (6.77 vs. 11.10 months), with restricted cubic spline analysis showing a nonsignificant trend toward a nonlinear association (P = 0.055).Age, RB1/NTRK1 mutation, and secondary T790M mutation were identified as independent risk factors and integrated into a predictive model with high accuracy. CONCLUSIONS: This study establishes a clinically applicable model for early prediction and risk stratification of SCLC transformation. Taxane-based regimens emerge as a promising later-line therapeutic option for T-SCLC.

Humans↗
PubMed1978

Expression of simian virus 40 early genes in transformed rat cells is correlated with maintenance of the transformed phenotype.

Early viral polypeptides synthesized in simian virus 40 rat transformants were identified by immunoprecipitation using anti-T (tumor) antigen immune serum. Four polypeptide classes could be identified, which were not detectable in extracts of nontransformed cells and were not precipitated from transformed cell extracts by nonimmune serum. Their apparent M(r) were 92,000, 63,000, 56,000, and 19,000. A similar pattern was observed in extracts from lytically infected cells, but the relative rate of radioactive labeling of the M(r) 63,000 and 56,000 species was in this case significantly lower than in transformed cells. In tsA30 transformants of type A, which maintain the transformed phenotype at high temperature, only minor quantitative variations of this pattern were observed when the cultures were shifted from 33 degrees to 40.5 degrees . In contrast, the rate of labeling of the four virus-specific polypeptides was decreased by 90% or more at high temperature in the temperature-sensitive N transformants. In all cases, a coordinated variation of the radioactivity associated with the different polypeptide classes was observed. These results suggest that the synthesis or processing, or both, of the viral early proteins may be controlled by different mechanisms in various types of simian virus 40 transformants and, furthermore, that it may be under the positive control of a virus-coded protein in transformed cells of type N.

Antigens, Neoplasm↗
PubMed1979

Reversion to methionine independence in simian virus 40-transformed human and malignant rat fibroblasts is associated with altered ploidy and altered properties of transformation.

Many transformed and malignant cells, unlike normal cells, do not grow when methionine in the growth medium is replaced by its immediate precursor homocysteine [Chello, P. & Bertino, J. (1973) Cancer Res. 33, 1898-1904 and Hoffman, R. & Erbe, R. (1976) Proc. Natl. Acad. Sci. USA 73, 1523-1527]. Rare cells from those populations revert to methionine independence [Hoffman, R., Jacobsen, S. & Erbe, R. (1978) Biochem. Biophys. Res. Commun. 82, 228-234]. We report here that methionine-independent revertants of both human fibroblasts transformed by simian virus 40 and malignant rat fibroblasts concomitantly revert for some of the properties associated with the transformed state. Of the 13 methionine-independent revertants described here, 5 showed increased anchorage dependence as reflected by reduced cloning efficiences in methylcellulose; 8 showed an increased serum requirement for optimal growth; 8 showed decreased cell density in medium containing high serum; and 3 altered their cell morphology significantly. Eight of the 13 have increased chromosome numbers. All lines tested contained immunologically identifiable tumor antigen of simian virus 40. Thus by selecting for methionine independence it is possible to select for heterogeneous transformation revertants, indicating further a relationship between altered methionine metabolism and oncogenic transformation. Therefore a positive metabolic method to select for transformation revertants has been developed, and its use has resulted in selection of human transformation revertants.

Animals↗
PubMed1979

Variant lines of mouse kidney cells transformed by an SV40tsA mutant with growth properties of wild-type transformed cells at nonpermissive temperature.

MKSA207 cells, a BALB/c mouse kidney line transformed by a tsA mutant of SV40, are temperature-dependent for the expression of the 'standard transformed phenotype'. At the permissive temperature (33.5 degrees C), the mKSA207 cells resembled wild-type (wt) SV40 transformants; they contained the intranuclear SV40 T antigen, grew to high saturation density in monolayer culture in either 10% or 0.5% serum, and also in methylcellulose suspension culture and became multinucleate in cytochalasin B. At the nonpermissive temperature (39.8 degrees C), the mKSA207 cells lost some of their transformed properties; they grew only to low density in 10% serum, hardly grew at all in 0.5% serum or in methylcellulose suspension culture, and remained mono- or binucleate in cytochalasin B. At 40 degrees C in low serum, mKSA207 cells lost the intranuclear T antigen and when fed 10% serum at 39.8 degrees C, accumulated large amounts of T antigen in the cytoplasm. Derivatives of mKSA207 have been selected at 39.8 degrees C in liquid medium and methylcellulose suspension culture. The heat adapted lines, like wt SV40 transformants, exhibited the standard transformed phenotype at both 33.5 and 39.8 degrees C. It is unlikely that acquisition of temperature-independence for the transformed phenotype was due to reversion of the tsA gene to wild-type because the heat-adapted cell lines displayed the cytoplasmic T antigen at 39.8 degrees C, characteristic of the parental mKSA207 cells and SV40 rescued from one of the heat-adapted lines was temperature sensitive for growth. The T antigen levels (complement fixation units per 10(6) cells) of heat-adapted lines grown at 39.8 degrees C were comparable to those of mKSA207 cells grown at 33.5 or 39.8 degrees C.

Animals↗
PubMed1979

Tumor antigens of human Ad5 in transformed cells and in cells infected with transformation-defective host-range mutants.

We have studied the polypeptides associated with the expression of the transforming region of the Ad5 genome by immunoprecipitating antigens (using the double antibody and protein A-Sepharose techniques) from cells infected with wild-type (wt) Ad5 or transformation-defective host range (hr) mutants and from cells transformed by Ad5. Three different antisera were used: P antiserum specific for early viral products (Russell et al., 1967) and two different hamster tumor antisera. Immunoprecipitation of antigens from wt-infected KB cells followed by SDS-polyacrylamide gel electrophoresis of precipitated proteins revealed that a major polypeptide having a molecular weight of approximately 58,000 was detected with all three antisera and with both the double antibody and the protein A-Sepharose techniques, while P antiserum also precipitated polypeptides of molecular weights 72,000, 67,000 and 44,000, which probably represent the DNA binding protein and related polypeptides, respectively. With the double antibody technique, in addition to the proteins mentioned above, P antiserum and the hamster tumor antisera precipitated a 10,500 dalton polypeptide which was not detected when the protein A-Sepharose procedure was used. Using either the double antibody or the protein A-Sepharose technique, we found that hr mutants from complementation group II failed to induce the synthesis of the 58,000 dalton protein, whereas mutants from complementation group I produced normal or near normal amounts. Using the double antibody technique, we found that the 10,500 dalton protein was absent or made in reduced amounts by group I mutants. A 58,000 dalton protein was detected in a number of different Ad5-transformed cell lines, including the 293 human line, the 14b hamster line and several transformed rat cell lines. This observation and the fact that transformation negative group II mutants fail to induce the synthesis of a 58,000 dalton polypeptide suggest that this protein is one of the Ad5-specific products necessary for cell transformation.

Adenoviruses, Human↗
PubMed1977

Cyclic AMP-induced morphological transformation of cells infected by temperature-sensitive mouse sarcoma virus. Expression of transformation-associated markers.

Normal rat kidney (NRK) cells infected with a temperature-sensitive (ts) mutant of mouse sarcoma virus (NRK [MSV-1b]) express the transformed phenotype when grown under permissive conditions, but acquire the normal phenotype when grown under restrictive conditions. Addition of 3', 5' cyclic adenosine monophosphate (cAMP) to NRK (MSV-1b) cells grown at the restrictive temperature results in morphological transformation. To determine whether other markers associated with the transformed phenotype were coordinately expressed after cAMP exposure, concanavalin A (Con A) agglutinability, hexose transport rate, and incorporation of radioactively labeled fucose into fucolipid III and fucolipid IV (FL III and FL IV ) of the cells were examined. NRK cells transformed by wild-type MSV or NRK(MSV- 1b) grown under permissive conditions were agglutinated by low concentrations of Con A and exhibited relatively high maximal agglutination levels which were specifically inhibited by alpha-methyl-D-mannoside. In contrast, NRK (MSV-1b) cells grown under restrictive conditions were weakly agglutinated by Con A and exhibited reduced maximal agglutination levels, similar to uninfected NRK cells. Treatment of NRK (MSV-1b) cells at the restrictive temperature with cAMP resulted in morphological transformation and a change in the pattern of incorporation of labeled fucose inot FL III and FL IV to one comparable to that of NRK (MSV-1b) cells at the permissive temperature or to NRK cells transformed by wild-type MSV. In contrast, cAMP treatment resulted in no increase in Con A agglutinability or 2 deoxy-D- [(3)H]glucose transport relative to mock treated cultures. The results demonstrate that cAMP-induced morphological transformation and altered fucolipid composition of NRK (MSV-1b) cells are not correlated with alterations in hexose transport rate or Con A agglutinability.

Agglutination↗
PubMed1977

Continued presence of similar transformation-associated antigens related to murine oncornavirus proteins in -ransformed cells, morphological revertants, and cells restricted in the expression of transformation.

The possible alteration of transformation-related antigens in cells that revert to a normal phenotype but that continue to retain the viral genome, has been investigated in [3H]glucosamine-labeled extracts of rat cells exhibiting a reversible temperature-dependent restriction in the expression of transformation and in a comparison of a morphologically altered mouse cell transformed by the Kirsten sarcoma virus with a flat revertant mouse cell derived from the morphologically transformed cells. With the use of normal goat serum in the presence of dibutyryl cyclic 3':5'-adenosine monophosphate, some differences became obvious in the rat cells restricted in the expression of transformation. However, use of specific antiserum to murine leukemia virus revealed in every case the presence of major components that exhibited an electrophoretic mobility corresponding to about 100,000 daltons both in the parent and revertant mouse cells and in the rat cells exhibiting either untransformed or transformed growth properties. The glycoprotein components detected only by the immune serum may represent a cellular macromolecule antigenically related to an interspecies C-type viral species whose concentration is increased in transformed cells.

Antigens, Neoplasm↗
PubMed1979

Fibronectin expression is determined by the genotype of the transformed parental cells in heterokaryons between normal and transformed fibroblasts.

The expression of fibronectin, a cell surface-associated transformation-sensitive glycoprotein, was studied in hetero- and homokaryons of normal and SV40-transformed human fibroblasts. In immunofluorescence, fibroblast homokaryons had an intense surface-associated and intracelluar fibronectin fluorescence similar to that of normal fibroblasts. Transformed cells and their homokaryons had a minimal surface-associated and a weak intracellular fibronectin fluorescence. In heterokaryons formed between transformed and normal fibroblasts, the expression of fibronectin fell within 24 h to the level of the transformed cell homokaryons. The change was detectable already at 3 h after fusion and was gene-dose dependent. These results show that the transformed genotype determines fibronectin expression in the heterokaryons.

Cell Fusion↗
PubMed1976

Transformation-enhancing factor(s) produced by virus-transformed and established cells.

Chick embryo fibroblasts (CEF) and hamster BHK21 cells transformed by the Schmidt-Ruppin strain of Rous sarcoma virus (SR-RSV) release into the culture medium a factor or factors which enhance 2- to 7-fold the formation of transformed foci by chich embryo fibroblasts infected with the Bryan strain of RSV (B-RSV). The factor(s) also increase the number of foci failing to revert to normal phenotype at restrictive temperature (41 degrees C) in cultures infected with a temperature-sensitive mutant (FU-19) of SR-RSV which is defective for transformation. The factor(s) is produced also by BHK21 cells transformed by other tumor viruses and by BHK21 cells passaged for a long time, but not by normal CEF, CEF transformed by B-RSV, CEF infected by FU-19 at 41 degrees C, normal hamster embryo fibroblasts, established but density-inhibited mouse fibroblasts, or BHK21 cells of early passages. The relative enhancement of the number of B-RSV foci can be more than 100-fold when the medium contains fetal calf serum which suppresses focus formation in controls. The focus-enhacing factor(s) appears to act after infection and has been termed, operationally, transformation-enhancing factor(s) or TEF. The factor produced by RS2/3 cells which enhances the formation of B-RSV foci is non-dialyzable and thermolabile, and is presumably a protein. Its molecular weight is between 10(5) and 2 X 10(5) daltons.

Animals↗
PubMed1977

Transformation of human cystinotic fibroblasts by SV40: characteristics of transformed cells with limited and unlimited growth potential.

Human skin fibroblasts derived from patients with nephropathic cystinosis were transformed with SV40 virions, cloned and permitted to enter the degenerative stage of growth termed "crisis," characteristic of SV40 transformed human cells. Nephropathic cystinosis is an autosomal recessively inherited metabolic disorder resulting in the intracellular accumulation of the amino acid cystine. A transformed cystinotic cell line which was recovered from the crisis stage was indistinguishable from its transformed precrisis parental cell strain in growth rate in media containing either 1% or 10% serum, cloning efficiency on plastic, in semisolid media, or upon confluent monolayers of normal skin fibroblasts, expression of SV40 T antigen, or production of virus. However, the modal DNA content of the recovered postcrisis transformed cystinotic cell line was different from that of the cloned parental precrisis transformed cell strain, suggesting that the postcrisis line was derived from a small subpopulation of the precrisis strain. The DNA content of the established cystinotic cell line continued to be unstable during subsequent subculturing and gave rise to subclones with both more and less DNA per cell. This line now has an apparently infinite growth potential and still has the hallmark of the cystinotic parental line, the storage of abnormally large amounts of intracellular nonprotein cystine.

Antigens, Viral↗