Search PubMed⌕ Search

Biomedical subjects

S Gattoni-Celli

Publications and source records attributed to S Gattoni-Celli.

At least 37 records · Page 2Linked to original sources
PubMed1989

Modulation of the transformed and neoplastic phenotype of rat fibroblasts by MHC-I gene expression.

Transfection of the activated ras oncogene (Ha-ras) into second passage rat embryo fibroblasts can induce the metastatic phenotype, while cotransfection of Ha-ras with the adenovirus type 2 E1a gene (Ad2-E1a) yields cells which are tumorigenic but nonmetastatic in nude mice. Because of the presence in nude mice of natural killer cells and B-lymphocytes, which might account for the different metastatic behavior of single versus double transfectants, we used triple deficient mutants as recipient animals in tumorigenicity assays. These mice carry two additional mutations resulting in the deficiency of natural killer cells and activated B-lymphocytes. We observed that the rat embryo fibroblast transfectants exhibit the same metastatic behavior in nude as well as in triple deficient mice, indicating that natural killer and B-cells are not responsible for the observed difference in metastatic phenotype between Ha-ras and Ha-ras plus Ad2-E1a transfectants. Double transfectants were found to express higher levels of major histocompatibility complex class I genes and the degree of expression appeared to correlate inversely with in vitro and in vivo parameters such as the ability to grow in agar-containing semisolid media and rate of tumor formation in triple deficient mice. Our observations are consistent with the concept that expression of major histocompatibility class I genes may be involved in regulating and modifying cell behavior by mechanisms independent of their role in immune recognition.

Animals↗
PubMed1989

Altered growth of a human neuroendocrine carcinoma line after transfection of a major histocompatibility complex class I gene.

The major histocompatibility complex (MHC) class I molecules are known to serve as recognition elements for cytotoxic T cells in mediating the rejection of transplanted tumors. We demonstrate that MHC molecules may have nonimmune functions in modulating tumor cell growth in addition to their classical role in antitumor immunity. A human neuroendocrine carcinoma cell line, COLO 320, with low levels of endogenous class I expression was transfected with the murine H-2Ld gene. Eleven independent stable clones were established, four containing only pRSV-neo and seven also containing varying copy numbers of the transfected Ld gene. The ability of the different clones to grow as colonies in soft agar correlated strongly with the relative amounts of Ld antigen expression (r = 0.89; P less than 0.001). There was a weaker correlation between increased clonogenic ability and higher levels of Ld mRNA (r = 0.67; P less than 0.05). There was no correlation between clonogenic ability and relative expression of amplified c-myc gene or of integrated pRSV-neo. Furthermore, in nude mice, Ld antigen expression was associated with increased formation of metastatic lung colonies 6 weeks after intravenous injection of 10(5) cells. These observations are consistent with the concept that MHC class I antigens may have a role in modulating the growth potential of certain tumor cells independent of their involvement in immune responses.

Adenocarcinoma↗
PubMed1988

Partial suppression of anchorage-independent growth and tumorigenicity in immunodeficient mice by transfection of the H-2 class I gene H-2Ld into a human colon cancer cell line (HCT).

Many human tumors, particularly those of epithelial origin, appear to express greatly reduced levels of major histocompatibility complex class I antigens on their surface. It has been previously reported that the class I gene H-2Ld, introduced into adenovirus type 12-transformed mouse cells, induces reversal of oncogenesis in immunocompetent BALB/c mice. We have tested the hypothesis that the H-2Ld gene, when transfected into HCT colon cancer cells, may alter their transformed phenotype. Two H-2Ld transfectants, HCT-Ii and HCT-If, were found to exhibit a markedly reduced-to-virtually suppressed ability to form colonies in soft agar in comparison to a transfectant (HCTh) carrying only the neomycin-resistance gene. We also compared the tumorigenicity of HCTh vs. HCT-If cells in two different strains of immunodeficient mice: nude (T-) and triple-deficient mutants (T-, NK-, B-). At 28 days postinjection of 10(7) and 10(6) cells, the size and growth rate of HCT-If tumors were greatly reduced compared to HCTh cells. Therefore, as assayed in immunodeficient animals, expression of the class I H-2Ld gene in HCT cells appears to correlate with partial suppression of the tumorigenic phenotype, suggesting that the expression of a transfected class I gene may by itself alter the phenotype of the recipient cell and that such phenotypic changes may be independent of the immune system.

Animals↗
PubMed1988

Evidence for expression of the facilitated glucose transporter in rat hepatocytes.

The eukaryotic facilitated glucose transporter (GT) is expressed by many cell types, with the notable exception of hepatocytes; however, GT is expressed by several hepatoma cell lines, including the well-differentiated lines Fao, Hep3B, and HepG2. We report on studies carried out to determine the aspect(s) of the transformed phenotype that might be responsible for activating GT expression. Using RNA blot analysis with probes derived from rat GT cDNA, we found that GT was expressed by rat hepatocytes under two conditions (i) in vitro, when isolated hepatocytes were placed in cell culture, and (ii) in vivo, when rats were subjected to starvation for greater than or equal to 2 days. However, GT expression was not an obligatory feature of hepatomas, since two primary hepatocellular carcinomas did not express any GT mRNA. GT expression in hepatocytes was reduced by addition of dimethyl sulfoxide or sodium butyrate to the culture medium. Since these reagents are known to promote differentiation in some cell culture systems, their effect on hepatocytes may be to maintain the GT repression normally observed in vivo. Inclusion or exclusion in the culture medium of several other agents that enhance hepatocyte viability (serum, insulin, corticosteroids, epidermal growth factor, or triiodothyronine) did not affect GT expression. It is unclear whether the two conditions that led to GT expression in hepatocytes are related by a common signaling mechanism. Possibly, both cases involve a "stress" response: in vivo, a normal physiological response to starvation; in vitro, a response to a major alteration in the cellular environment.

Animals↗
PubMed1987

Productive, persistent infection of human colorectal cell lines with human immunodeficiency virus.

Thirteen adherent human non-lymphocyte cell lines were tested for their susceptibility to infection by human immunodeficiency virus. Productive infection could be demonstrated in three of five colorectal carcinoma cell lines examined; the other eight human non-lymphocyte cell lines were uninfectible. A susceptible colon carcinoma cell line (HT29), as well as normal colonic mucosa, was shown to contain a 3.0-kilobase species of poly(A)+ CD4 RNA, whereas uninfectible colon carcinoma and rhabdomyosarcoma cell lines synthesized no detectable T4 RNA. A persistently infected colon carcinoma cell line was established that continued to produce progeny human immunodeficiency virus for more than 10 weeks postinfection.

Cell Line↗
PubMed1986

Expression of type C-related endogenous retroviral sequences in human colon tumors and colon cancer cell lines.

Type C-related human endogenous retroviral sequences have been previously discovered and characterized [Martin, M. A., Bryan, T., Rasheed, S. & Khan, A.S. (1981) Proc. Natl. Acad. Sci. USA 78, 4892-4896]. We investigated the transcriptional pattern of these sequences to determine whether and to what extent their expression is altered in colon tumors and colon cancer cell lines as compared to normal colon mucosa (NCM). Of two long terminal repeat (LTR)-specific transcripts [3.6 and 2.1 kilobases (kb)], the 3.6-kb RNA was particularly abundant in NCM but strikingly decreased in most primary colon cancers tested. In NCM we identified three envelope gene (env)-related transcripts--namely, 3.0, 1.7, and 0.6 kb. Colon tumors appeared to express higher levels of these transcripts, especially the 1.7-kb species. In one case of dysplasia and in one benign tumor, this 1.7-kb transcript was clearly increased. We also examined the pattern of transcription in colon cancer cell lines HCT and Caco2. The LTR-homologous 3.6-kb transcript, very abundant in NCM, was decreased in primary tumors and in HCT cells and virtually absent in Caco2 cells. The latter, however, appeared to produce the transcript when growing exponentially, indicating that Caco2 cultures provide an inducible system susceptible to in vitro manipulation. Both cell lines also contained higher amounts of the 1.7-kb env-related transcript. The decrease of the 3.6-kb RNA in colon tumors versus NCM may be the result of an altered pattern of differentiation, whereas the increase of the 1.7-kb RNA in tumors may represent an early marker of colon neoplasia.

Base Sequence↗
PubMed1986

Carcinogen induced asynchronous replication of polyoma DNA is mediated by a trans-acting factor.

We have demonstrated that carcinogen damage to DNA induces the production of cellular factors that act in trans to enhance the asynchronous replication of polyoma viral DNA. Exposure of a polyoma virus-transformed rat cell line to benzo[a]pyrene-7,8-diol-9,10-oxide (BPDE), the ultimate carcinogenic metabolite of benzo[a]pyrene, led to the accumulation of heterogeneously sized free viral DNA molecules which contain polyoma origin sequences as well as cellular sequences that flank the integrated viral DNA. When the sequence gpt was linked to the polyoma early region and transfected into rat cells, it underwent asynchronous replication in response either to direct treatment of the transfected cells with BPDE, or to fusion of untreated transfected cells with normal cells previously exposed to BPDE. Transient arrest of the cell cycle by hydroxyurea, isoleucine deprivation or methotrexate caused a slight enhancement of viral DNA replication when compared with BPDE. Both aphidicolin, an inhibitor of DNA polymerase alpha, and 3-aminobenzamide, an inhibitor of poly[ADP]ribosyl transferase, caused marked inhibition of BPDE-induced viral DNA synthesis. The induction of a trans-acting factor in response to damage of cellular DNA may be relevant to synergistic interactions between environmental chemicals and DNA viruses in cell transformation and to the general phenomenon of gene amplification.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1986

Effects of 5-azacytidine on expression of endogenous retrovirus-related sequences in C3H 10T1/2 cells.

In a previous study (22) we found that transient exposure of C3H 10T1/2 mouse embryo fibroblasts to 5-azacytidine (5-azaC) induced several changes in growth properties. The treated cells showed progressive changes in morphology, saturation density, growth rate, and serum dependence. By passage 5, the cells had acquired the ability to grow in 0.3% agarose, and by passage 30, they had given rise to fully transformed foci that grew in agarose, agar, and liquid suspension. This progression was rapidly accelerated if the cultures derived from 5-azaC-treated cells were exposed for 48 h to the carcinogen benzo[a]pyrene. The present studies demonstrate that both type C and type A, but not type B, retrovirus-related sequences were expressed in the 5-azaC-treated cells. There was negligible expression of these sequences in the control 10T1/2 cells. The level of expression of the related RNAs tended to correlate with loss of anchorage dependence and other markers of an increase in the transformed phenotype. These changes were associated with hypomethylation of the corresponding cellular DNA sequences, as revealed by differential digestion with the restriction enzymes HpaII and MspI. These studies provide evidence that aberrations in DNA methylation and induction of expression of certain endogenous retroviruses may be one of a series of critical events during the course of multistage carcinogenesis, thus enhancing the evolution of malignant tumor cells.

Animals↗
PubMed1986

Expression of retroviral sequences and oncogenes in murine hepatocellular tumors.

The expression of endogenous retroviral sequences and of three cellular oncogenes was examined in three hepatocellular adenomas and in four carcinomas induced in male C57BL/6JDp X C3Hf/Dp F1 (hereafter called B6C3F1) mice by a single dose of nitrosodiethylamine, in five carcinomas that arose spontaneously in male C3Hf mice, and in the livers of normal age-matched control mice. In all of these adenomas and carcinomas, there was increased expression of Moloney murine leukemia virus- and intracisternal A particle-related sequences. The retrovirus-like VL30 sequence was expressed at significant levels in the normal liver of these mice and increased expression of this sequence was found in only 4 of the 12 tumors examined. Expression of endogenous mouse mammary tumor virus-related sequences was not detected in the normal livers or in any of the liver tumors. With respect to cellular oncogenes, increased expression of c-myc was seen in all of the B6C3F1 tumors. Two of five normal liver samples and all of the tumors of the C3Hf mice displayed significant expression of c-myc. There was a slight increase in expression of c-Ha-ras in some of the tumors. Increased expression of c-fos was found in only 1 of the 12 tumors. Taken together, these studies indicate that both carcinogen-induced and spontaneous liver tumor formation in mice is associated with abnormalities in the expression of endogenous retrovirus-related DNA sequences and also specific cellular oncogenes.

Animals↗
PubMed1985

Effects of 5-azacytidine on the progressive nature of cell transformation.

C3H 10T1/2 mouse embryo fibroblasts were exposed to 3 microM 5-azacytidine for 24 h and then serially passaged in the absence of 5-azacytidine and examined for subsequent changes in growth properties. The treated cells showed changes in morphology, saturation density, growth rate, and serum dependence. By the 5th passage they acquired the ability to grow in 0.3% agarose, and by the 30th passage they gave rise to fully transformed foci that grew in agarose, in agar, and in liquid suspension. This progression was rapidly accelerated if the cultures derived from 5-azacytidine-treated cells were exposed for 48 h to the carcinogen benzo[a]pyrene. Results of these studies provide evidence that aberrations in DNA methylation may be one of a series of critical events during the course of multistage carcinogenesis and thus enhance the evolution of tumor cells.

Animals↗
PubMed1985

Mechanisms of multistage chemical carcinogenesis and their relevance to respiratory tract cancer.

The evolution of a fully malignant tumor is a multistep process resulting from the action of multiple factors, both environmental and endogenous, and involves alterations in the function of multiple cellular genes. Chemical carcinogens that initiate this process appear to do so by damaging cellular DNA. In addition to producing simple point mutations, this damage appears to induce the synthesis of a transacting factor that can induce asynchronous DNA replication. This response may result in gene amplification and/or gene rearrangement. This phenomenon may also play a role in synergistic interactions between chemicals and viruses in the causation of certain cancers. The primary target of the tumor promoters TPA, teleocidin, and aplysiatoxin appears to be cell membranes. All three of these agents act, at least in part by, enhancing the activity of the phospholipid-dependent enzyme PKC. We have proposed a stereochemical model to explain the interaction of these amphiphilic compounds with the PKC system. We have found that TPA and teleocidin markedly enhance the transformation of C3H10T1/2 mouse fibroblasts when these cells are transfected with the cloned H-ras human bladder cancer oncogene. Thus, tumor promoters can act synergistically with an activated oncogene to enhance cell transformation. Furthermore, carcinogen-transformed rodent cells display aberrations in the expression of various endogenous retrovirus-related sequences. Activation of some of these sequences may lead to insertion mutations and further aberrations in gene expression. These findings are discussed in terms of a multistep model that involves progressive changes in cellular oncogenes and aberrations in the function of DNA transcription enhancer sequences. It will be of interest to determine to what extent these concepts apply to the etiology of cancers of the respiratory tract.

Animals↗
PubMed1984

Oncogene-induced transformation of C3H 10T1/2 cells is enhanced by tumor promoters.

The tumor promoters 12-O-tetradecanoyl-phorbol-13-acetate and teleocidin markedly enhanced the transformation of C3H 10T1/2 mouse fibroblasts when these cells were transfected with the cloned human bladder cancer c-rasH oncogene. Transfection studies with the drug resistance marker gpt and time course studies indicate that this enhancement is not simply an effect on the process of DNA transfection. These findings, together with parallel studies with NIH 3T3 fibroblasts, also indicate that the competence of animal cells for DNA transfection is a function of the recipient cell line, the transfected marker, and the growth conditions. Our findings suggest that during multistage carcinogenesis tumor promoters may complement the function of activated cellular oncogenes.

Animals↗
PubMed1984

Cellular targets and host genes in multistage carcinogenesis.

Recent studies indicate that although cellular DNA is the critical target in the action of initiating carcinogens, specific membrane-associated receptors mediate the actions of certain tumor promoters. A stereochemical model is presented to explain how three different types of tumor promoters (phorbol esters, indole alkaloids, and polyacetates) can interact with the same class of cellular receptors. Multistage chemical carcinogenesis might involve progressive alterations in the expression of cellular DNA sequences homologous to oncogenes and regulatory sequences in certain retroviruses. We found that the oncogene c-mos is not rearranged or expressed in a series of carcinogen-transformed murine C3H 10T112 cells. These cells do express, however, a unique set of poly(A)+ RNAs that contain sequences homologous to the Moloney leukemia virus long terminal repeat sequence. Studies are in progress to determine the significance of this finding with respect to the carcinogenic process.

Animals↗
PubMed1984

Effects of 5-azacytidine on methylation and expression of specific DNA sequences in C3H 10T1/2 cells.

The present study indicates that the transient exposure of C3H 10T1/2 mouse embryo fibroblasts to 5-azacytidine leads to extensive loss of methylation of the protooncogene c-mos and the beta-globin locus at the cell population level and in at least 40 isolated subclones. These changes persisted, even when the cells were serially passaged for many generations without further exposure to the drug. Even though the amount of demethylation, assessed through differential digestion by the restriction enzymes HpaII and MspI, was quite extensive, neither locus was transcribed at a detectable level. This nonselective analysis suggests, therefore, that loss of DNA methylation is not sufficient per se to induce the expression of certain loci. Presumably, the expression of these loci requires additional factors, some of which may be related to cell lineage and differentiation.

Animals↗
PubMed1983

Benzo[a]pyrene induction of extrachromosomal viral DNA synthesis in rat cells transformed by polyoma virus.

The effect of the carcinogen benzo[a]pyrene (BP) on the production of specific extrachromosomal DNAs has been studied in transformed rat cells containing integrated polyoma virus DNA. Exposure of cells previously transformed by the polyoma virus mutant ts-a, which codes for a temperature sensitive T antigen, to a non-toxic dose of BP (0.25 micrograms/ml) enhanced the production of free polyoma DNA at the population level. This occurred at 33 degrees C (the permissive temperature) but not at 39 degrees C, indicating that the BP effect was dependent on the function of the T antigen of polyoma virus. In the same cell system, BP did not induce the production of extrachromosomal copies of two endogenous rat retrovirus genomes, the 30S RNA virus and rat leukemia virus. Thus, the effects on integrated polyoma DNA are quite specific and do not reflect a generalized increase in asynchronous DNA replication and excision. Further studies utilizing a carcinogenic metabolite of BP, benzo[a]pyrene trans-7,8-dihydrodiol-9,10-epoxide (anti) (BPDE), on a rat cell line transformed by wild type (WT) polyoma virus demonstrate that the enhancement of polyoma DNA synthesis persists for at least 5 days after a single exposure to BPDE, despite the rapid decay of this compound. In addition, enhanced synthesis of polyoma DNA can be induced by fusion of normal rat fibroblasts previously exposed to BPDE with polyoma transformed rat fibroblasts not exposed to BPDE. It appears, therefore, that the effects we have observed are not due solely to direct carcinogen damage at the level of the integrated polyoma virus DNA, but may instead involve the induction of cellular factor(s) that act indirectly to enhance asynchronous replication of polyoma DNA.

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