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PubMed1985

Secretion of phosphoproteins associated with neoplastic transformation and with the action of transforming growth factors.

Incubation of conditioned media derived from mammary epithelial cells and from fibroblasts with [gamma-32P]ATP revealed much higher intensities of labeled polypeptides in transformed cells compared to normal cells. Conditioned media from human mammary carcinoma cells have in common the presence of characteristic phosphoproteins with molecular masses of about 37,22 and 19.5 kDa. Ehrlich Ascites Mammary Carcinoma Cells secrete a dominant 32 kDa phosphoprotein. Normal fibroblasts secrete elevated levels of phosphoproteins after treatment with transforming growth factors. A phosphoprotein with molecular mass of about 37 kDa becomes secreted preferentially if cell-conditioned media were labeled in vivo. The results indicate that the phosphoproteins comprise a family of secretory polypeptides associated with early steps of transformation.

Animals↗
PubMed1983

Comparison of intra- and extracellular transforming growth factors from nontransformed and chemically transformed mouse embryo cells.

Multiple transforming growth factors (TGFs) have been isolated from the serum-free conditioned media and acid-ethanol cell extracts of nontransformed AKR-2B and chemically transformed AKR-MCA mouse cells. The TGF activity was analyzed using Bio-Gel P-60 chromatography in 1 M acetic acid and tested for colony-stimulating activity in soft agar using AKR-2B, AKR-2B (clone 84A), NRK, and AKR-MCA cells as indicators. Both intracellular and extracellular TGF activity from AKR-MCA and AKR-2B cells show a major peak of AKR-2B and epidermal growth factor-potentiated NRK colony-stimulating activity that coelute in the 13,000 +/- 2,000 molecular weight region. In the 24,000 +/- 7,000 molecular weight range, AKR-MCA cells produce intracellular and extracellular NRK colony-stimulating activity that is not potentiated by epidermal growth factor, while the intracellular and extracellular NRK colony-stimulating activity produced by AKR-2B cells requires added epidermal growth factor for colony formation. Also important in determining the growth and morphological characteristics of a cell line, besides the production of a TGF, is the ability of a cell to respond to TGF activity. We have shown that the transformed AKR-MCA cells form more colonies than AKR-2B cells in response to certain TGF activities. This suggests that the increased responsiveness of AKR-MCA cells to TGFs may be important in determining its phenotype.

Animals↗
PubMed1983

Isolation and partial purification of a new class of transforming growth factors from an avian sarcoma virus-transformed rat cell line.

Transformation of rat cells by avian sarcoma viruses induced the release of growth factors into serum-free conditioned medium. An avian sarcoma virus-transformed rat cell line, 77N1, produced and released a polypeptide growth factor, classified as a transforming growth factor (TGF), which transiently promotes anchorage-dependent BALB3T3 A31 cells to form progressively growing colonies in soft agar. The TGF was isolated and partially purified from an extract of 77N1 cells by ion-exchange chromatography on a diethylaminoethyl Sephacel column followed by ammonium sulfate precipitation. The TGF was assumed to have a molecular weight of 11,000 from gel filtration on Sephadex G-50. This TGF did not compete with epidermal growth factor for binding to cell membrane receptors and was not potentiated by epidermal growth factor. The TGF was trypsin and dithiothreitol sensitive as well as heat and acid labile, indicating that it was different from previously reported TGFs of similar molecular weight and thus belonged to a new class of TGFs.

Animals↗
PubMed1984

[Characterization of a transforming growth factor produced in rat cells transformed by an avian sarcoma virus].

Transformation of rat cells by avian sarcoma viruses (ASVs) induced the release of transforming growth factors (TGFs), which transiently promote anchorage-dependent untransformed BALB3T3 clone A31 cells to form progressively growing colonies in soft agar, into serum-free conditioned medium. A new class of TGF, which is a heat and acid-labile protein with a molecular mass of 12,000 daltons, was isolated and purified from an ASV-transformed rat cell line, 77N1, derived from NRK cells. The TGF from 77N1 did not bind to epidermal growth factor membrane receptors. We observed specific in vitro phosphorylation of several membrane proteins from A31 cells in the presence of the TGF.

Animals↗
PubMed1978

Recovery of transforming EBV from non-producer cells after superinfection with non-transforming P3HR-1 EBV.

Cells of the Raji and NC37 lines can be induced by chemical inducers, such as BrdUrd and IdUrd, or the tumor-promoter TPA to EA-expression only, but do not reveal any VCA synthesis. After superinfection by nontransforming P3HR-1 EBV, however, a varying percentage of the cell population shows VCA synthesis and releases infectious viral particles. The recovered virus differs biologically from P3HR-1 EBV since it transforms human umbilical cord blood lymphocytes into EBNA-positive lymphoblastoid cell lines. Cells of these established lines are susceptible to renewed infection by P3HR-1 EBV which results in EA induction and VCA synthesis. Only cells of one line, NC37-R1, spontaneously produce VCA and EBV particles, which reveal transforming properties and do not induce EA upon superinfection of Raji cells. Infection of P3HR-1 EBV-converted BJA-B cells also leads to EA and VCA induction and the release of viral particles. In contrast to particles recovered from Raji and NC37 cells, no transforming activity was detectable in these virus preparations. According to these data, we propose that viral genomes persisting within Raji and NC37 cells are defective and become complemented by the superinfecting P3HR-1 virus.

Antigens, Viral↗
PubMed1979

Decreased sensitivity to interferon associated with in vitro transformation of X-ray-transformed C3H/10T1/2 cells.

We have compared the interferon sensitivity of parental 10T1/2 cells, having a phenotype characteristic of normal cells, with that of transformed cells isolated after X-irradiation of treatment with methylcholanthrene. Transformed cells were 10- to 20-fold less sensitive than the parental untransformed cells to the antiviral action of interferon and were also less sensitive to the inhibitory effect of interferon on cell multiplication. The decreased sensitivity of these cells to interferon is a useful marker of the transformed phenotype.

Animals↗
PubMed1979

Cell cycle dependence of transformation expression in mouse cells transformed by a thermosensitive mutant (Ts-121) of polyoma virus.

Change in division capability as a phenotypic expression of cellular transformation was investigated by using one of the temperature-sensitive (ts) mutants of the polyoma virus-transformed cell line, the 121-6-5 cells of BALB/3T3. When contact -inhibited cells were treated with hyaluronidase at 39 degrees C, a single round of cell division was induced after which cell growth was inhibited by cell density. However, if the cells were incubated at 35 degrees C, after the enzyme treatment, density-inhibition block disappeared and the cells entered a second division. This indicates that the release of cells from density-inhibition depends on the low temperature incubation. The ability of cells to complete a second division was examined by shifting the cells from 39 degrees C to 35 degrees C during different phases of the first division cycle after the enzyme-treatment. A 6-hour incubation of S phase cells at 35 degrees C resulted in a second cycle of division, while the 24-hour incubation of G1 cells at 35 degrees C did not induce a second round of division. These results suggest that expression of the transformed phenotype in 121-6-5 cells is clearly dependent upon both the temperature and the phase of the division cycle.

Animals↗
PubMed1984

Cell growth and differentiation in vitro in mouse macrophages transformed by a tsA mutant of simian virus 40. II. Changes in the distribution of DNA content during the reversible transition between macrophage and nonmacrophage states in the cultures of tsA640-transformed macrophages.

Cultures of mouse macrophage cell lines transformed by wild-type or the tsA640 mutant of simian virus 40 (SV40) show a reversible phenotypic transition between the nonmacrophage (proliferating phase) and the macrophage (stationary phase) states (Takayama, 1980; Tanigawa et al., 1983). Distribution of DNA content in the cultures of the tsA640-transformed macrophage lines in the process of the phenotypic transition was determined by flow cytometry. Taking the mean DNA content of mouse peritoneal macrophages as 1 unit in the scale of fluorescence intensity in the flow cytogram, the transformed macrophages showed, at 33 degrees C, two peaks, one located around the 1.0-unit position (peak 1.0) and the other around the 1.6-unit position (peak 1.6), and a plateau distribution continuing to 3.2 units. Peak 1.0 was predominant in the stationary-phase culture, whereas peak 1.6 was predominant in the proliferating-phase culture. Almost the entire population of the strictly resting culture, which was obtained by culturing the stationary-phase culture for a further 5 days at nonpermissive temperature (39 degrees C), was phagocytic, and had accumulated at peak 1.0. Cells in peak 1.0 moved to peak 1.6 and to higher positions, after the strictly resting culture was sparsely reseeded and incubated at 33 degrees C. In contrast, the DNA content distribution of the successively proliferating cells, which were obtained by repeated passage of an extensively proliferating culture and none of which were phagocytic, was similar to that of proliferating hypotetraploid BALB/c3T3 fibroblasts with a G1 peak at 1.6 unit followed by a plateau containing S- and G2-phase cells. The peak 1.0 cell population appeared from the recloned population of the successively proliferating cells in company with the restoration of the culture condition-dependent phagocytic ability when cocultured with primary macrophages. Each peak in the flow cytogram reflected fairly well DNA content per cell as determined by other methods.

Animals↗
PubMed1985

Potassium-induced reverse transformation of cells infected with a temperature-sensitive transformation mutant virus.

High potassium concentrations altered the morphology and the ability to grow in soft agar in 6m2 cells, a clone of rat kidney cells infected with a temperature-sensitive mutant of Moloney sarcoma virus. Approximately 60% of cells exhibited normal morphology in the presence of 94.8 mM potassium in isotonic medium at the temperature permissive for transformation, whereas 100% were normal at 72 mM potassium in hypertonic media. A significant reduction of growth in soft agar was also induced with these conditions. However, the synthesis ratio of virus-specified transforming protein to marker viral protein was not altered. Na+K+-ATPase might play a role in this reverse-transformation process.

Animals↗
PubMed1989

Stimulation of cartilage-matrix proteoglycan synthesis by morphologically transformed chondrocytes grown in the presence of fibroblast growth factor and transforming growth factor-beta.

The effects of transforming growth factor-beta (TGF-beta) on the synthesis of cartilage-matrix proteoglycan by cultured rabbit chondrocytes were examined. Rabbit chondrocytes were seeded at low density and exposed to a 1:1 mixture of Dulbecco's modified Eagle's medium and Ham's F-12 medium supplemented with 0.5% fetal bovine serum, 1% bovine serum albumin, 50 micrograms/ml ascorbic acid, and 2 x 10(-7) M hydrocortisone (Medium A). Various combinations of TGF-beta, insulin-like growth factor-I (IGF-I), and fibroblast growth factor (FGF) were also added to Medium A, and the chondrocytes were grown to confluency. Chondrocytes grown with TGF-beta or FGF alone became flat or fibroblastic, those grown with FGF and TGF-beta became very elongated and formed distinct foci, and those grown with FGF and IGF-I showed the spherical configuration characteristic of overtly differentiated chondrocytes. Nevertheless, the incorporation of 3H with glucosamine into the large, chondroitin sulfate proteoglycan synthesized by cultures with FGF and TGF-beta was similar to that in cells grown with FGF and IGF-I and five times that in cells cultured with FGF alone. The increases in incorporation of 3H reflected real increases in proteoglycan synthesis, because chemical analyses showed an increase in the accumulation of macromolecules containing uronic acid in cultures with FGF and TGF-beta or with FGF and IGF-I. However, FGF in combination with either TGF-beta or IGF-I had little effect on the incorporation of 3H into small proteoglycans or hyaluronic acid. These results indicate that chondrocytes morphologically transformed with TGF-beta and FGF fully express the differentiated proteoglycan phenotype rather than the transformed glycosaminoglycan phenotype.

Animals↗
PubMed1989

Transformation of an established mouse mammary epithelial cell line following transfection with a human transforming growth factor alpha cDNA.

To determine whether the enhanced expression of transforming growth factor alpha (TGF alpha) is sufficient to induce the neoplastic transformation of an immortalized population of mammary epithelial cells, we cotransfected NOG-8 cells, a cloned mouse mammary epithelial cell line, with a simian virus 40-human TGF alpha cDNA expression vector plasmid and a pSV2neo plasmid. After cotransfection, nine G418-resistant NOG-8 colonies were cloned and expanded. All clones were subsequently analyzed for TGF alpha mRNA expression by northern blot analysis, TGF alpha secretion, anchorage-dependent growth in serum-free medium, anchorage-independent growth in soft agar, and tumorigenicity in nude mice. Three TGF alpha-transfected NOG-8 clones expressed high levels of a specific TGF alpha mRNA, secreted elevated levels of TGF alpha into the culture medium (177-595 ng/10(8) cells/48 h), exhibited an enhanced growth rate, grew aggressively as colonies in soft agar, and formed undifferentiated, invasive carcinomas in nude mice. A neutralizing mouse monoclonal antibody generated against the low molecular weight human TGF alpha peptide was able to inhibit colony formation in soft agar by TGF alpha-transfected NOG-8 clones that produced high levels by TGF alpha. This inhibition suggested that TGF alpha acted through an external autocrine loop. NOG-8 cells and NOG-8 cells transfected with a pSV2neo plasmid alone secreted very low levels of TGF alpha, failed to grow as colonies in soft agar and did not form tumors in nude mice. These results demonstrate that overexpression of a human TGF alpha cDNA in immortalized, nontransformed mouse mammary epithelial cells can induce a transformed phenotype in vitro and can facilitate tumor formation in vivo.

Animals↗
PubMed1998

Protein kinase C isoform expression and function in transformed and non-transformed pancreatic acinar cell lines.

Members of the protein kinase C (PKC) family of multifunctional serine/threonine phosphorylating enzymes are believed to play a role in regulating cellular differentiation and proliferation in many cell types. In the present study, we examined the expression of PKC isoforms in non-transformed (BMRPA.430) and transformed (TUC3) rat pancreatic acinar cell lines and compared this to PKC expression in freshly dispersed acini from rat pancreas. BMRPA.430 cells maintain characteristics of normal acini and are not tumorigenic, whereas TUC3 cells do not express tight junctions or polygonal morphology and are tumorigenic. As reported previously, PKC alpha, delta, epsilon, and zeta are expressed in freshly prepared acini. Likewise, these isoforms were detected in both the BMRPA.430 and TUC3 cell lines. In addition, PKC theta, a novel isoform, was detected in all three cell types at low levels. We used two PKC inhibitors to examine the role of PKC in acinar cell proliferation. CGP 41 251, a selective PKC inhibitor, and Go 6976, an agent which specifically inhibits calcium-dependent PKC isoforms, inhibited cell proliferation of both cell lines. Translocation of PKC alpha to the membrane was not observed in either cell line. Hence, our data indicate that ras-induced transformation does not alter PKC isoform expression in pancreatic acinar cells and that activation of PKC alpha is involved with acinar cell growth.

Animals↗
PubMed1977

Transformation in Bacillus subtilis: biological and physical evidence for a novel DNA-intermediate in synchronously transforming cells.

Competent B. subtilis cells exposed to transforming DNA in the presence of EDTA bind, but do not take up DNA. Rapid and almost synchronous uptake of the bound DNA is achieved by the addition of Mg2+ ions in excess of the EDTA. At 30 degrees and at 17 degrees comparable numbers of transformants are produced from cells pre-loaded with DNA at 30 degrees (after termination of uptake by the addition of DNA ase the samples were incubated at 37 degrees). However, almost no transformants are produced when cells are exposed to DNA at 17 degrees, although binding does take place then. Because DNA is taken up at 17 degrees after having loaded the cells at 30 degrees, whereas no uptake occurs after binding at 17 degrees, it is suggested that binding of DNA to the cellular surface involves at least two steps. In DNA re-extracted from cells at 17 degrees, pre-loaded with DNA at 30 degrees, little recombinant type activity is present, indicating that integration is blocked at 17 degrees. However, physico-chemical analysis of the re-extracted DNA indicates that a complex between single-stranded donor DNA and the recipient chromosome is formed at 17 degrees. This complex has a higher buoyant density than donor-recipient complexes formed at 30 degrees.

Bacillus subtilis↗
PubMed1989

Efficient transformation of Bacillus thuringiensis and B. cereus via electroporation: transformation of acrystalliferous strains with a cloned delta-endotoxin gene.

Electroporation was used as a method to transform intact cells of Bacillus thuringiensis and B. cereus. With our optimized method a range of plasmid vectors could be transformed into strains of B. thuringiensis at frequencies of up to 10(7) transformants/micrograms DNA. This high frequency allows cloning experiments to be done directly in B. thuringiensis. A bifunctional vector capable of replicating in Escherichia coli and in Bacillus spp. was constructed. The kurhd1 protoxin gene was cloned into this shuttle vector to produce plasmid pX193, then transformed into B. thuringiensis HD1 cryB and B. cereus 569K. The cloned protoxin gene was expressed in sporulating cultures of both strain HD1 cryB (pX193) and 569K (pXI93), producing crystal protein active in biotests against larvae of Heliothis virescens. This demonstrates the usefulness of the electroporation method for the introduction of cloned toxin genes, in either their native or modified form, into a variety of host strains.

Bacillus cereus↗
PubMed1985

SV40 transformed fibroblasts recognize the same 140 kD fibronectin chemotactic fragment as non-transformed cells.

SV40-virus-transformed human embryonal fibroblasts show an enhanced chemotactic response to the glycoprotein fibronectin. However, they recognize the same chemotactic active region as non-transformed fibroblasts. The result suggests that an enhancement of chemotaxis by fibroblasts which have been transformed with Simian Virus 40 is due not to the utilization of further chemotactic domains in the molecule, but to an increased sensitivity of the cells to the chemoattractant.

Cell Transformation, Viral↗
PubMed1977

Transformation in Bacillus subtilis. Initial stages of the transformation process and their energy dependence.

NaN3 was found to inhibit transformation but not the irreversible binding of donor 3H-DNA in competent cells of the original low-transformable strain Bacillus subtilis 168 trp2. Addition of NaN3 to cells of two mutants Bacillus subtilis HT39 and HT46 with an increased transformability decreased substantially the irreversible binding of the donor DNA to the competent cells. The decreased irreversible binding of DNA is caused by an increased osmotic sensitivity of competent cells of the mutants HT39 and HT46 in the presence of NaN3, leading preferentially to lysis of the competent cells.

Azides↗
PubMedDate not supplied

Characterization of cryptic plasmids from marine cyanobacteria and construction of a hybrid plasmid potentially capable of transformation of marine cyanobacterium, Synechococcus sp., and its transformation.

Among forty strains of marine cyanobacteria isolated in our laboratory, five strains had 1-3 different plasmids. The unicellular marine cyanobacterium, Synechococcus sp. NKBG 042902, contains at least three plasmids (pSY09, pSY10, and pSY11). However, these plasmids are cryptic. Therefore, a hybrid plasmid pUSY02 containing the 1.4-kb HindIII fragment of pSY11 and Escherichia coli plasmid pUC18 was constructed. The plasmid pUSY02 transformed both marine Synechococcus sp. NKBG042902-YG1116, which is a cured strain, and fresh water Anacystis nidulans R2 by dark incubation or Ca2+ treatment. However, the plasmid pSG111 constructed from the plasmid DNA of A. nidulans R2 failed to transform marine Synechococcus sp. Electroporation was also applicable to transformation of marine Synechococcus sp. and fresh water A. nidulans R2. The plasmid pUSY02 was rapidly introduced into marine Synechococcus sp.

Aspergillus nidulans↗
PubMed1976

Biosynthesis of plasma membrane components by SV40-virus-transformed 3T3 mouse cells temperature sensitive for expression of some transformed cell properties.

We have studied the plasma membranes of an SV40-transformed 3T3 cell line temperature sensitive for the transformed growth phenotype (ts H6-15 cells), and have found that they vary little as a function of temperature of cultivation. Analysis by polyacrylamide gel electrophoresis was performed on plasma membranes prepared from ts H6-15 cells cultured at the permissive (32 degrees C) and non-permissive (39 degrees C) temperatures and radioactively-labelled in several ways. No significant differences were seen when the electrophoretic patterns of polypeptides of the plasma membranes of ts H6-15 cells, grown through 3-4 generations in medium containing radioactive leucine (32 degrees C and 39 degrees C temperatures) were compared. Plasma membranes derived from cells similarly grown in medium with radioactive glucosamine indicated that extensive alterations in the intrinsic glycopeptides occurred in association with alteration in growth phenotype. A shift towards decreased synthesis of large molecular weight (congruent to 100 000-160 000) glycopeptides occurred in cells grown at the temperature of non-transformed growth (39 degrees C). A decrease in amount of a 120 000 molecular weight glycopeptide at 39 degrees C was the most prominent of these alterations. We have studied the surface exposure of polypeptides and glycopeptides of intact cells grown at 32 and 39 degrees C, using lactoperoxidase-catalyzed iodination, NaBH4 reduction of galactose oxidase-treated cells, and metabolic-labelling with glucosamine of trypsin-sensitive molecules. We found no major qualitative differences between whole cell extracts or between plasma membrane preparations of cells cultivated at the permissive and non-permissive temperatures. Of special interest was the observation that the formation and surface exposure of a trypsin-sensitive, 240 000 molecular weight polypeptide appeared not to be ts in ts H6-15 cells. The significance of these observations will be discussed.

Cell Fractionation↗