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C Cerni

Publications and source records attributed to C Cerni.

At least 19 recordsLinked to original sources
PubMed1991

Immunization against human papillomavirus type 16 tumor cells with recombinant vaccinia viruses expressing E6 and E7.

Papillomaviruses are etiological agents of epithelial proliferative disease. In man, neoplastic transformation of the uterine cervix has been linked to infection with specific subtypes of human papillomavirus, particularly types 16 and 18. We previously reported that live vaccinia virus recombinants expressing early transforming proteins of other tumor viruses can immunize against challenge with cognate tumor cells and we have extended this approach to HPV16. Neoplastic transformation by papillomaviruses involves expression of early open reading frames (ORFs) E5, E6, and E7, and we report the construction of vaccinia recombinants separately expressing ORFs E5-E7 of HPV16. Primary rat cell lines cotransformed with HPV16 and an activated ras oncogene were established in order to evaluate the potential of the recombinants to elicit antitumor immunity. We report that inoculation of rats with vaccinia recombinants expressing E6 or E7 retarded or prevented tumor development in a proportion of animals challenged by subcutaneous seeding of tumor cells whereas the recombinant expressing E5 was inactive.

Animals↗
PubMed1990

Immortalization of primary rat embryo cells by human papillomavirus type 11 DNA is enhanced upon cotransfer of ras.

Transfer of human papillomavirus type 11 (HPV11) DNA and a neo(r) marker into primary rat embryo cells (REC) led to colony formation in G418-selective medium. About 20% of HPV11 clones were eventually established in culture but displayed low growth rates. Cotransfection of HPV11 DNA and an activated ras oncogene led to formation of both drug-resistant flat colonies and phenotypically transformed clones which grew efficiently when expanded in culture. A number of transformants reverted to a flat, "normal" morphology shortly after isolation. Nontransformed clones expressed only HPV11 genes, while those maintaining a transformed phenotype transcribed both ras and HPV11 genes efficiently and were highly tumorigenic. Expression of HPV11 thus seems, necessary for induction of colony formation, but efficient long-term growth seems to require at least the transient presence of ras.

Animals↗
PubMed1990

Non-selective analysis of the transformation of FR3T3 rat cells by bovine papillomavirus type 1: regulations of viral transcription associated with phenotypic transformation.

Drug-resistant clones selected from FR3T3 rat cells after transfer of neo-BPV1 (Bovine Papillomavirus Type 1) DNA constructs became phenotypically transformed (focal transformation, growth in suspension and tumor formation) soon after selection (approximately 5 generations in culture). A frameshift mutation in ORF E5 abolished transformation, but did not prevent the autonomous maintenance of the DNA construct. A more complex situation was observed when the E2 transactivating function was abrogated. A minority of the E2(-)-neor clones became phenotypically transformed shortly after drug selection, but the majority maintained normal growth properties for 30 to 50 generations. The rate of viral transcription was uniformly high in cells which exhibited transformed growth properties early after selection (the E2- minority class and all the wild type transformants) and low in phenotypically normal cells (the majority of the E2- lines). The same low transcriptional activity and delayed expression of transformed growth properties had been observed after transfection of a similar construct carrying a wild type viral early region (69-T fragment), but lacking the late region. The elevated rate of viral transcription, which correlates with the immediate expression of transformation, appears therefore to require at least two distinct elements, the E2 transactivator function and sequences in the late region of the viral genome. In their absence, high transcription rates and transformation could be established only in a minority of the transfected clones, by an unknown, E2-independent mechanism. Evidence was obtained for a third transformation route which, in the absence of either E2 or the late region, led to the focal occurrence of transformed derivatives after 30 to 50 generations of normal growth, but was not associated with an overall increase in viral expression.

Animals↗
PubMed1989

Successive steps in the process of immortalization identified by transfer of separate bovine papillomavirus genes into rat fibroblasts.

Transfer of neor and bovine papillomavirus type 1 (BPV1) DNA into rat embryo fibroblasts led to colony formation in G418-containing medium, with no detectable background in controls with neor DNA alone. More than 50% of the drug-resistant clones could be further propagated in culture. The genetic functions of BPV1 involved in colony formation and in long-term immortalization were investigated by both translation termination mutations in the full-length genome, which inactivate individual open reading frames, and constructs in which these open reading frames were separately expressed under control of long terminal repeat promoter enhancers. Expression of either open reading frame E2 or E5 was sufficient for formation of a drug-resistant colony, but long-term growth in culture required that of E6. No significant cooperative effect was observed upon cotransfection of BPV1 and ras oncogene DNAs. Expression of the early region of the human papillomavirus type 16 also led to immortalization of rat embryo fibroblast cells in the same assay, and, unlike what was previously reported in baby rat kidney cells, it required neither activation by a heterologous promoter, nor a cooperating ras oncogene.

Animals↗
PubMed1988

Tumorigenic transformation of rat FR3T3 fibroblasts carrying an activated myc oncogene requires subsequent mutational events.

Early passage FR3T3 rat cells were co-transfected with a neo resistance gene and pSVc-myc-1, an SV40-driven expression vector carrying an activated murine myc oncogene. Selection in G418 medium produced clones expressing the exogenous myc gene at various levels, with a concomitant loss of expression of the normal c-myc allele. These clones were phenotypically normal, but, in fluctuation tests performed according to Luria and Delbrück (1943) on subcultures independently derived from the same clone, transformed foci appeared as stochastic events with a wide range of fluctuation. These results indicate that expression of the oncogene was not sufficient to induce the appearance of transformed growth properties, and that secondary genetic changes are required, most likely mutations in cellular proto-oncogenes. Within a single clone, independent transformants exhibited different tumorigenic potentials, spanning from high efficiency to no detectable tumor induction, without any clear correlation with their degree of in vitro transformation. Tumors and cell lines established from independent tumors, while maintaining the exogenous myc gene without gross rearrangement of its structure, no longer expressed the oncogene and resumed the expression of the normal allele.

Animals↗
PubMed1987

Transfer of 'immortalizing' oncogenes into rat fibroblasts induces both high rates of sister chromatid exchange and appearance of abnormal karyotypes.

Cell lines established after transfer into FR3T3 rat fibroblast cells of 'immortalizing' oncogenes (plt gene (large T protein) of polyoma virus, v-myc gene of MC29 virus, rearranged forms of c-myc) exhibited increased rates of sister chromatid exchange (SCE). This was observed neither in cells which expressed one of the oncogenes responsible for the terminal stages of tumorigenic transformation (polyoma virus pmt (middle T protein), mutated ras genes), nor in cell lines carrying oncogenes of both types. Abnormal chromosome numbers were observed in cell lines expressing plt or myc, but not after transformation by pmt or ras oncogenes.

Animals↗
PubMed1987

Elevated expression of an exogenous c-myc gene is insufficient for transformation and tumorigenic conversion of established fibroblasts.

Two established rat fibroblast lines, differing only by their number of generations in culture, show dramatically different responses to the elevated c-myc expression delivered by an efficient murine c-myc retrovirus vector. Thus, a late passage (60 generation) FR3T3 line acquires a transformed and tumorigenic phenotype upon introduction of this activated c-myc gene as indicated by its altered morphology, high efficiency of focus formation, soft agar clonability, saturation density in monolayer culture, and short latency of tumorigenicity in syngeneic hosts. Remarkably, none of these characteristics, except for an increased refractility in monolayers and an epidermal growth factor (EGF)-dependent agar clonability, were observed in a variety of early passage (10 generation) FR3T3 c-myc clones. BALB/c A31 fibroblasts transfected with this c-myc retroviral vector behaved essentially the same as the FR3T3 early line except for their inability to grow in suspension in response to EGF. However, transformation and tumorigenic conversion of each of these three fibroblast lines was achieved by an activated ras oncogene. Hence, elevated c-myc expression is insufficient for transformation of established fibroblasts but depends upon other acquired cooperating functions which are not necessary for ras induced transformation. We also demonstrate that endogenous c-myc expression remains unaffected even in clones expressing a 100-fold excess of exogenous c-myc RNAs demonstrating that c-myc autoregulation is not operative in these cells.

Animals↗
PubMed1984

Effect of tissue culture variables on sister chromatid exchange in a nontransformed rat cell line.

The frequency of sister chromatid exchange (SCE) was determined in a nontransformed diploid rat cell line, FR3T3 , under several tissue culture variables such as cultivation temperature, growth conditions of cells, and concentrations of 5-bromo-2'-deoxyuridine (BrdU). The conclusions to be drawn from these experiments are: (a) The cell growth and mechanisms(s) of SCE formation in FR3T3 cells are largely temperature independent (or efficiently regulated) in the range between 33 and 40.5 degrees C. (b) The concentration limits for BrdU incorporation are 5 to 100 microM; baseline frequency is about 11 SCE/metaphase (constant up to 20 microM BrdU) and increases only moderately at higher BrdU concentrations. (c) Toxic levels of BrdU (150 microM) cause a decrease of SCE rates below that found at 100 microM, presumably due to selective cell death. (d) Keeping cells growth arrested over a long period causes substantial SCE induction after replating. (e) Induced increase of SCEs probably occurs in this manner during the first cell cycle after release from growth arrest. It is no longer detectable after the fourth consecutive cell division.

Animals↗
PubMed1984

Sister chromatid exchange in FR3T3 rat fibroblasts transformed by Simian virus 40.

The frequency of Sister Chromatid Exchange (SCE) was determined at low (33 degrees C) and high (40.5 degrees C) temperatures in cell lines derived from FR3T3 rat fibroblast cells after transformation either with Wild-Type Simian Virus 40 (SV40-WT), with an origin-defective SV40 (SV40-ori-), or with the early temperature-sensitive mutant tsA30. Of these cell lines, SV40-WT-, SV40-ori--, and one class of tsA30-transformants (A-type) express the transformed phenotype both at 33 and 40.5 degrees C. The other tsA30-transformants (N-type) revert to a normal phenotype at high temperature. As compared with normal FR3T3 cells, all transformants exhibited, at 33 degrees C, increased numbers of metaphases with high SCE rates. At 40.5 degrees C, all cell lines which expressed a transformed phenotype (SV40-WT, tsA30 type A, SV40-ori-) exhibited substantially increased SCE rates. That this increase was not related to a possible induction of viral replication by BrdU, was proven by Southern blot analysis and by SCE data on SV40-ori--transformed cells. By contrast, no such temperature-induced increase of SCE rates was observed in tsA30-transformants of type N.

Animals↗
PubMed1984

Increase of sister chromatid exchange formation induced by diethylstilbestrol.

The latent appearance of genital tract tumors in young women is highly correlated with prenatal exposure to synthetic estrogens such as diethylstilbestrol (DES). To extend the information on the mutagenic effect of DES, the frequency of sister chromatid exchange (SCE) was determined in bone marrow cells of Sprague-Dawley rats and in cultured FR3T3 rat fibroblasts. In this study a significant increase of SCE frequency after the application of different concentrations of DES could be observed both in vivo and in vitro.

Animals↗
PubMed1984

Chronic application of a tumor promoter to confluent nontransformed rat cells induces the irreversible expression of transformed phenotype.

The hypothesis was put foreward that 'immortalisation' of an established nontransformed cell line might represent one type of 'initiation' in the process of malignant transformation. Therefore, a nontransformed rat fibroblast cell line, FR3T3, was investigated as to whether or not it could be irreversibly transformed by exposure to the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). TPA was applied in different treatment schedules at varying growth phases of the cells (logarithmic or stationary growth). The cells' acquisition of transformation-associated properties was studied by means of various transformation assays (saturation densities and formation of dense foci both at low and high serum concentrations, as well as growth in agarose and production of plasminogen activator, PA). We found that a phase of stationary growth plus TPA treatment was decisive for the induction of transformed cell clones. Growth in 0.5% serum was used as the selection procedure. Several isolated foci manifested, in vitro, highly transformed phenotypes. However, only 1 of 12 clones produced PA. All cell lines derived from these clones, proved to be tumorigenic in syngeneic animals. Since the nontransformed, but 'immortal' rat cell line is susceptible (at certain growth conditions) to the tumor promoting activity of TPA, we conclude that induction of 'immortalisation' may, from an operational point of view, correspond to 'initiation', at least in this particular cell line.

Animals↗
PubMed1984

The transformation of a rat cell line induced by a tumor promoter occurs without affecting sister chromatid exchange.

Malignant transformation of cells of an established rat cell line, FR3T3, can be achieved by the exclusive treatment of the cells with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) over a stationary growth period. In the course of the transformation process, sister chromatid exchange (SCE) rates of treated cells were examined at various key-points and compared to control cells. It was found that neither a single TPA treatment nor repeated TPA application during 16-22 consecutive cell-doubling times (which induces substantial alterations of the phenotypes) increased SCE rates in the rat cells. Furthermore, transformed cell clones, which were selected from low-serum cultures and which were found to be tumorigenic in vivo, had SCE rates in the same range as the parental nontransformed FR3T3 cells. It is, therefore, concluded that malignant transformation of the rat cells - induced by TPA - occurs without affecting such large-scale DNA rearrangements as are detectable by means of the SCE method.

Animals↗
PubMed1983

Indication of reduced doxorubicin-induced cardiac toxicity by additional treatment with antioxidative substances.

The influence of antioxidative substances on doxorubicin-induced cardiac toxicity was studied in C 57 BL mice. Tocopherol (500 mg/kg), glutathione (1000 mg/kg), cysteamine (15 mg/kg) and L-cysteine (1000 mg/kg), injected i.p. 24 h before doxorubicin treatment (15 mg/kg i.p.) were able to reduce malonaldehyde production in cardiac tissues significantly. SH-containing substances with high reducing activity, such as vitamin E, could be a useful tool in clinical trials to prevent doxorubicin induced cardiac damage.

Animals↗
PubMed1983

Lymphocyte transformation and isovolemic hemodilution with hydroxyethylstarch 450,000.

The effect of hemodilution upon lymphocyte transformation was studied in vivo. 20 p.c. of circulating blood volume was replaced by Hydroxyethylstarch 450,000 6%, (HES 450) and 24 hours later but prior to surgery lymphocyte transformation using PHA was not substantially changed. These findings were in accord with previous in vitro studies. There appeared to be no significant change of the total lymphocyte count, alteration of serum proteins seemed to be proportional presenting a mere dilutional phenomenon. It can thus be concluded that hemodilution does not impair cellular immune defense nor increase the risk for patients prone to sepsis or spread of malignancy.

Blood Cell Count↗
PubMed1983

[Effect of dextran 60,000(D 60) and hydroxyethyl starch 450,000 (HES 450) on lymphocyte transformation].

Lymphocytes of volunteers were recovered, isolated and H3 thymidine incorporation was measured in the presence of D 60 and HES 450 with and without PHA. Without mitogen dextran caused only a marginal increase of incorporation whereas HES brought about no change. When PHA-stimulation was used, both compounds seemed not to influence H3-thymidine incorporation. It is concluded that in vitro even in molar concentrations corresponding to clinical haemodilution these solutions appear not to suppress lymphocytic activity.

Adult↗