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At least 19 recordsLinked to original sources
PubMed1979

Proteolytic enzymes in normal and transformed cells.

Virally transformed cells show an increased production of proteolytic enzymes. These might be involved in transformation-dependent alterations of cell surface glycoproteins. The possibility arises that some of these proteases might be membrane-bound. To investigate this possibility, we have undertaken a comparative study of the reactivity of intact normal and transformed cells with the tritium labelled protease inhibitor diisopropylfluorophosphate, in parallel with fibrinolytic assays. Using these two approaches in concert, it was possible to identify and localize in the transformed cells several proteases which were present in the particulate cell fraction and were probably membrane bound. In particular, a diisopropylfluorophosphate-reactive polypeptide of 62,000 was increased 5--8-fold on transformation. It comigrated with a fibrinolytic activity. Other particle-bound activities were also detected. While diisopropylfluorophosphate-labelling can be useful for detecting proteases inside cells, it does not appear to be specific for surface proteases.

Animals↗
PubMed1978

Recognition of virally transformed cells by lymphocytes from patients with prostatic cancer.

Data presented describe the first assay using human peripheral blood lymphocytes (PBL) against two unique virally transformed cell lines in vitro. Human cells transformed by a cytomegalovirus (CMV-Mj) isolated from normal human prostate tissue were used as target cells in microcytoxicity assays with lymphocytes from 100 patients. Three target cell types were used: control human embryonic lung cells (HEL), transformed HEL cells (CMV-Mj-HEL-2), and transformed HEL cells retrieved from tumors induced in athymic nude mice (CMV-Mj-HEL-2, T-1) by injection of CMV-Mj-HEL-2 cells. PBL preparations from 84% of all patients tested significantly killed CMV-Mj-HEL-2, T-1 cells. However, only PBL from patients with prostatic carcinoma were cytotoxic for CMV-Mj-HEL-2 cells significantly more often than for control HEL. The implications of this approach are discussed.

Adult↗
PubMed1977

Lymphocyte reactivity against virally transformed cells in patients with urologic cancer.

Lymphocytes from patients with urologic cancer were tested in microcytotoxicity assays against human cells transformed by cytomegalovirus. Human lymphocytes were significantly cytotoxic against the transformed cell line when compared to a normal human control cell line. Patients with prostatic carcinoma demonstrated greater target cell reduction than those with benign prostatic hyperplasia.

Adenocarcinoma↗
PubMed1976

The chick chorioallantoic membrane as a model system for the study of tissue invasion by viral transformed cells.

The chick chorioallantoic membrane (CAM) was used as an assay system to investigate the the invasive properties of viral transformed NIH/3Y3 cells. Scanning electron microscopy demonstrated that single Kirsten sarcoma virus (KiSV)-transformed cells passed between the epithelial cells of the CAM ectoderm within 6 hr of application, while viable NIH/3T3 cells did not penetrate the ectoderm within 24 hr. The transformed cells entered the mesoderm of the CAM and formed tumors of proliferating cells. The application of 5 X 10(5) KiSV-transformed cells resulted in the formation of donor cells resulted in the formation of the donor cell tumors within 5 days in 43% of the membranes. No tumors were formed when as many as 5 X 10(6) NIH/3T3 cells were applied to the membrane. NIH/3T3 cells transformed by the Abelson leukemia virus or the Moloney sarcoma virus also ivaded the CAM and formed tumors of proliferating cells within the mesoderm, while cells infected with the Moloney leukemia virus did not. NIH/3T3 cells inoculated onto the CAM 8 days after infection and transformation with KiSV formed tumors with a frequency similar to that of KiSV transformed cells that have been passaged in culture for many generations. Cells that formed invasive tumors within the mesoderm also attracted loops of host blood vessels.

Animals↗
PubMed1978

An altered response of virally transformed 3T3 cells to ouabain.

The effect of ouabain on K+ transport was examined in 3T3 and virally transformed 3T3 cells. A 10 min exposure to ouabain (10(-3) M) produced approximately 40% inhibition of the unidirectional K+ influx in all cell lines. In 3T3 cells the response was not significantly altered by up to 70 min exposure to the drug. In contrast, the continued exposure of transformed cells to ouabain produced a time-dependent increase in the K+ influx. This increased influx was shown to be accompanied by an increase in the K+ efflux. The results suggest that, in transformed cells, ouabain produces both an inhibition of Na+-K+ exchange and a stimulation of K+-K+ exchange. The latter was shown to be more readily reversible than the former.

Cell Line↗
PubMed1979

A rapid screening for the specific DNA sequence: analysis of transforming DNA segments in adenovirus-transformed cells.

The viral DNA sequences in cells transformed by adenovirus type-12 (Ad12) DNA fragments were investigated by spot hybridization, a detection by autoradiography of nucleic acid hybrids formed between cell DNAs spotted on a membrane filter and various nick-translated Ad12 DNA fragments. In CY1 cell line, a rat cell line transformed by the EcoRI-C fragment (left hand 16%), all of the HindIII fragments included in the EcoRI-C fragment are shown to be present. In GY1 cell line, a rat cell line transformed by the HindIII-G fragment (left hand 7%), both of the BpaI-H and a part of the BpaI-J, two components consisting of the HindIII-G fragment, were found. A dominant presence of the Ad12 BpaI-H fragment (left hand end 4.5%) of the Ad12 DNA molecule, approximately 60% of the Ad12 transforming DNA sequences (Ad12 HindIII-G), was also shown in GY1. Spot hybridization used in the experiment will be of general use for detecting viral nucleic acid sequences in cells and provides a simple and useful screening method for investigating viral etiology of tumors and transformed cells.

Adenoviruses, Human↗
PubMed1977

Immunologic selection against simian virus-40 transformed cells: concomitnat loss of viral antigens and early viral gene sequences.

A clonal line of highly oncogenic "spontaneously transformed" mouse cells (T AL/N clone 3) was transformed in tissue culture by simian virus 40 (SV40) and subsequently recloned. The clone of SV40-transformed cells (subclone 1) expressed SV40-specific T (nuclear) and transplantation antigens but was 100 times less tumorigenic than the parent T AL/N clone 3 cells. When large numbers of subclone 1 cells (10(4)-10(5)) were injected into syngeneic AL/N mice, tumors were produced. From the tumors, cell lines were established in culture, all of which were consistently negative for T antigen. Tumor lines tested were found not to contain SV40-specific transplantation antigen and had again become highly tumorigenic. The original subclone 1 cells contained about one copy of SV40 DNA per diploid amount of cell DNA, as well as RNA complementary to the early region of the SV40 genome. The T antigen-negative cells from tumor line 124 contained approximately 0.5 copy of SV40 DNA per diploid equivalent and did not synthesize any detectable virus-specific RNA. Reassociation kinetic analysis with restriction enzyme fragments of viral DNA demonstrated that the cells from tumor line 124 (and also the clones of this line) had lost DNA sequences predominantly from the early region of the SV40 genome. The results indicate that a set of stably integrated SV40 DNA sequences can be present in a cell without the expression of viral antigens.

Antigens, Viral↗
PubMed1977

Relationship between the methionine tryptic peptides of simian virus 40 and BK virus tumor antigens.

The monomer form of BK virus (BKV) tumor antigen (T Ag) was immunoprecipitated from extracts of BKV-transformed cells and had a molecular weight of approximately 113,000. This compared with 97,000 for the molecular weight of either BKV or simian virus 40 (SV40) T Ag from lytically infected cells. The SV40 and BKV T Ag's from productively infected cells were compared by examining their methionine-labeled tryptic peptides. Out of a total of 20 SV40-and 21 BKV-specific peptides, there were seven pairs of similar peptides on the basis of ion-exchange chromatography, These coeluting peptides contained approximately 25 to 30% of the total methionine radioactivity. Similar results were obtained when the tryptic peptides of SV40 T Ag from lytically infected cells were compared with those of BKV T Ag from virally transformed cells.

Antigens, Neoplasm↗
PubMed1979

On the reduced intercellular adhesiveness of virally transformed BHK21 cells.

Baby hamster kidney fibroblasts (BHK21 cells) transformed by polyoma or Rous sarcoma viruses aggregate less than the untransformed parental cells when incubated in growth medium in a gyratory shaker for 18-24 h. This difference can be measured by electronic particle counting, or by filtering aggregated suspensions of 32P-labelled cells through bolting fabric. The aggregation of transformed derivatives is not enhanced by the presence, during aggregation of epsilon-amino caproic acid, an inhibitor of plasmin activation. Some lines of transformed BHK21 cells do not appear less adhesive than untransformed cells in a short-term aggregation assay, and none adheres markedly less well when seeded onto homotypic cell sheets. The decreased aggregation of transformed cells is consistent with suggestions that LETS protein is involved in intercellular adhesion of fibroblasts as well as in attachment of cells to non-cellular substrates. If so, the short-term aggregation of freshly trypsinized cells may depend on secretion of LETS from an intracellular pool.

Aminocaproates↗
PubMed1978

Effects of cocultivation with transformed cells on surface proteins of normal cells.

Virally transformed fibroblasts do not have on their surface a major protein (large external transformation-sensitive, LETS) which is present in normal cells. Cocultivation of the transformed cells with normal cells whose surface proteins have been prelabelled induces an accelerated release of the LETS protein from the normal cells. We have investigated various conditions which affect this phenomenon. Our results show that alteration of cell surface proteins by cocultivation with the transformed cells is time and dose-dependent and requires cell contact. Serum was depleted at least 99% of plasminogen by affinity chromatography and used in the cocultivation experiments. It was found that activation of plasminogen was not required for the accelerated turnover of the LETS protein. Other diffusible proteases are also unlikely to be involved. The possibility that transformed cells have a membrane bound activity is discussed. The role of plasminogen activation was also tested for its relevance in transformation related proteolysis, growth and morphology of cells.

Cell Line↗
PubMedDate not supplied

Chromosome abberations in rat embryo cells transformed after infection with ultraviolet-irradiated herpes simplex virus.

Two rat embryo cell lines (TR1 and TR2) transformed after infection with ultaviolet-inactivated herpes simplex virus type 2 showed modal chromosome numbers in the tetraploid range. In the TR1 cell line a near-diploid cell population replaced during subcultivation the hypotetraploid cells thus explaining the loss of immunofluorescent viral antigens. Both transformed cell lines showed frequent achromatic gaps. In the TR1 cell line such gaps were preferentially located in specific chromosome regions. The occurrence of achromatic gaps is presumably associated with the activity of a viral gene.

Animals↗
PubMed1977

State of the viral DNA in rat cells transformed by polyma virus. II. Identification of the cells containing nonintegrated viral DNA and the effect of viral mutations.

F2408 rat cells transformed by polyoma virus contained integrated and nonintegrated viral DNA. The presence of nonintegrated viral DNA is under control of the A early viral function. Polyoma ts-a-transformed rat cells lose the free viral DNA when growth at the nonpermissive temperature (40 degrees C), but they reexpress it 1 to 3 days after they are shifted back to the permissive temperature. In contrast, rat cells transformed by a late viral mutant, ts-8, contain free viral DNA at both permissive and nonpermissive temperatures. Treatment of the transformed rat cells with mitomycin C produces a large increase in the quantity of free viral DNA and some production of infectious virus. Experiments of in situ hybridization, with 3H-labeled polyoma complementary RNA as a probe, show that only a minority (approximately 0.1%) of the transformed cells contain nonintegrated viral DNA at any given time. These results suggest that the presence of free viral DNA in polyoma-transformed rat cells is caused by a spontaneous induction of viral DNA replication, occurring with low but constant probability in the transformed cell population, and that the free viral DNA molecules originate from the integrated ones, probably through a phenomenon of excision and limited replication.

Animals↗
PubMed1979

Antiserum to murine leukemia virus recognizes novel cell surface molecules associated with growth control and transformation.

Antiserum directed against murine leukemia virus also reacts with several external proteins present in rat cells transformed by a temperature-sensitive Rous sarcoma virus. Reaction of iodinated cell extracts with anti-MLV (murine leukemia virus) serum revealed the presence of a 200,000 dalton iodinated component detectable also by metabolic labelling with glucosamine only in serum-starved cultures restricted in the expression of transformation. A similar assay with iodinated cells that express the transformed phenotype revealed the preferential recognition of two components with an approximate molecular weight of 100,00 daltons as well as an additional 65,000-dalton external component. Growth of the transformed non-producer NT3-KR cells in the presence of inducers of C-type viruses leads to an increased synthesis of a 100,000-dalton glycoprotein (gp100) recognized by the anti-MLV serum which is also recognized by the antiserum in NRK-MSV-MLV transformed producer cells, in addition to a virus-like glycoprotein of 71,000 dalton (gp71). Absorption of the anti-MLV serum with monolayers of NT3-KR cells eliminated the ability of the serum to recognize the gp100 but not the gp71 from NRK-MSV-MLV-transformed producer cells. The mediation of post-translational changes in growth control is suggested by the transformation-dependent alteration in the molecular weight of the non-virion surface proteins recognized by anti-MLV serum in the rat cells used in this study.

Animals↗
PubMed1978

Fluorescent antibodies and lectins stain intracellular structures in fixed cells treated with nonionic detergent.

Nonionic detergent (NP40) treatment of paraformaldehyde-fixed normal and SV40-transformed human fibroblasts resulted in intracellular penetration of two chosen fluorescent antibodies and Concanavalin A (Con A). After the detergent treatment nuclear SV40 T antigen, cytoplasmic fibronectin glycoprotein and Con A binding sites could be visualized in fluorescence microscopy. The lowest NP40 concentration which made fixed cells permeable was 0.05%. The morphology of cells was preserved better by this new method than by conventional fixation methods, such as acetone treatment. In scanning electron microscopy the surface of the fixed NP40-treated cells had only small rugosities and fine pores. The subsurface cytoskeleton especially was well preserved and had a more distinct fine structure. The improved morphology made it possible to detect a similar distribution of fibronectin and Con A binding sites in the perinuclear endoplasmic reticulum regions.

Antigens, Viral↗
PubMed1979

Possible role of fibronectin in malignancy.

Frozen sections of tumors induced by injecting virally transformed cells into animals were stained for fibronectin by immunofluorescence. Many tumor cell lines do not express fibronectin in tumors in situ even though some of them express fibronectin in culture. Cell shape and hormones appear to influence the expression of fibronectin in culture; however, it is unclear how fibronectin expression is regulated in vivo.

Animals↗
PubMed1979

Defective interfering particles modulate VSV infection of dissociated neuron cultures.

Infection of dissociated neuron cultures of mice with VSV and its defective particle DI-T was studied using fluorescent light microscopy as well as transmission and scanning electron microscopy. When cultures are infected with wild virus, VSV replicates selectively in neurons, producing cell death within 24-48 hr. Sensory and immature neurons express viral antigen most rapidly. Viral antigen and viral budding sites are detected along the neuron soma and dendrites. When large amounts of DI-T particles are added to the wild virus inoculum, viral growth is completely suppressed in mature neurons, the cell killing effects of VSV are considerably delayed and co-infected cultures survive for 5-16 days. Viral antigen accumulates in cytoplasmic inclusions and on the membrane of neuron cell somas and dendrites in the virtual absence of viral assembly. Identical modulation of VSV infection in mature neuron cultures is obtained when DI-T particles are added before or after the wild virus, but ultraviolet inactivation of DIs completely abolishes their protective effect. Immature neurons or Vero cells cannot be protected from acute cytopathic changes by an equivalent amount of DI particles. Thus DIs interfere with replication and assembly of the wild virus and attenuate cell killing effects in mature neurons in vitro.

Animals↗