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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A line of mouse mammary epithelial cells (NMuMG) has been characterized for its ability to be stably transfected with exogenous DNA. A transfection frequency of at least 1 cell per 1,000 was obtained with the pSV2neo plasmid. Several thousand G418-resistant NMuMG cell clones can easily be generated in cotransfection of genomic DNA and pSV2neo. The NMuMG cells were isolated from normal mammary glands and do not form malignant lesions when injected into nude mice. We have cotransfected NMuMG cells with pSV2neo and genomic DNA from the human EJ bladder carcinoma line, a cell line which contains an activated c-rasH oncogene. When a pool of 4,700 G418-resistant colonies was injected into nude mice, tumors were obtained. These tumors contain a transfected human rasH gene. Genomic DNA transfection into a line of mouse epithelial cells, in combination with the selection of stable transfectants and tumor induction in nude mice, can be used to screen human tumor DNA for the presence of activated oncogenes.
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PMID:New acceptor cell for transfected genomic DNA: oncogene transfer into a mouse mammary epithelial cell line. 398 19

Mouse Lewis Lung tumor DNA was ligated to a cosmid containing a geneticin (G418)/kanamycin resistance gene and transferred into NIH3T3 cells. Recipient cells were first selected for geneticin resistance and subsequently for their ability to grow as a tumour when injected into nude mice. By repeating this transfection procedure with DNA from resultant tumours, geneticin-resistant NIH3T3 cells were obtained which were tumorigenic and contained approximately 1-5 copies of the transferred cosmid. The functional oncogene was cloned by preparing cosmid libraries of third round tumour DNAs, using a cosmid which does not contain a kanamycin resistance gene. Due to the original linkage of the oncogene with the cosmid containing the kanamycin resistance gene, a series of kanamycin-resistant cosmids were isolated, five of which contained an active oncogene. Subsequent analysis showed that the oncogene present was highly related to the human N-ras gene. Using a DNA probe from the MLL N-ras gene, a non-transforming counterpart was isolated from mouse liver DNA. A comparison between the two N-ras genes showed that a mutation at the amino acid position corresponding to 61 in the human gene is responsible for transforming activity of the rescued gene.
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PMID:Use of gene transfer and a novel cosmid rescue strategy to isolate transforming sequences. 405 98

In the experiments reported here, I was unable to detect any fusion between host cells and transplanted tumor cells; however, spontaneous hybridization between tumor cells appears to occur in the B16 melanoma. This hybridization was demonstrated by mixing together B16-F10RR cells (universal fusers) and B16-F10 cells, allowing them to grow in close juxtaposition, and recovering putative hybrids in the appropriate selection media. The tumor cell-tumor cell composition of the resultant hybrids is inferred from the relative frequency of fusions, compared with the infrequency of tumor cell-host cell fusion when single populations of B16-F10RR cells were used, and by the chromosomal content of the hybrids. Definitive proof that hybridization occurs between both types of tumor cell rather than between a tumor cell and some other type of cell would require the use of a third biochemical marker on the unmarked tumor cells. I am now repeating these experiments using B16-F10 cells that exhibit resistance to the neomycinlike antibiotic G418. Nonetheless, it is not surprising to find that such closely related tumor cells fuse with one another. The efficiency of in vitro hybridization mediated by polyethylene glycol is increased when the hybridizing cells are histologically or developmentally related, so that B16 melanoma cells fuse more readily with one another than they do with unrelated cells such as UV-2237 cells (I. Hart, unpublished observations). Moreover, early hybridization protocols did not call for the use of fusogens, but merely the cocultivation of participating cells in the two-dimensional constraints of a tissue culture dish (e.g., Barski et al. 1961, Silagi 1967). Presumably, the increased contact between cells within a growing tumor mass would increase the likelihood of such spontaneous fusion. In vivo hybridization could play a significant role in neoplastic progression and variation in metastatic efficiency by at least two separate, but not necessarily mutually exclusive, mechanisms. First, fusion of two contiguous tumor cells would increase the chromosome content of the resultant single cell; this increase in ploidy could facilitate and heighten the apparent inherent genetic instability of neoplastic cells (Nowell 1976). Although segregation and chromosome loss may or may not be random or preferential in nature (Campbell and Worton 1981), the mere occurrence of such a phenomenon could also cause chromosomal disjunction and the possible extinction and reexpression of specific genes, which would lead to the independent variation and progression of different tumor cell characteristics in the manner cited by Foulds (1969).(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Tumor cell hybridization and neoplastic progression. 638 3

The mouse embryonal stem cell line BLC 1 growing on feeder layer was treated with a calcium phosphate/DNA precipitate prepared with DNA of plasmid pAG60 which harbors the Tn5-derived neo gene, thus encoding resistance to G418, an aminoglycoside antibiotic. Transfection performed on feeder layer resulted in the formation of G418-resistant clones T1 and T2/K26. The stable integration of the transformed neo gene was confirmed by dot hybridization in all descendant cultures of clones T1 and T2/K26 as well as in the tumors derived from them. In vivo and in vitro differentiation revealed the pluripotent status of the transformants. Tumors derived from T1 and T2/K26 contained various tissues with derivatives of all three primary germ layers.
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PMID:DNA transformation of a pluripotent mouse embryonal stem cell line with a dominant selective marker. 659 77

We show that a new rat chondrosarcoma (RCS) cell line established in long-term culture from the Swarm tumor displayed a stable differentiated chondrocyte-like phenotype. Indeed, these cells produced the collagen types II, IX, and XI and alcian blue-stainable cartilage-specific proteoglycans, but no type I or type III collagen. To functionally characterize their chondrocytic nature, the cells were stably transfected with a type II collagen/beta geo chimeric gene which confers essentially perfect chondrocyte-specific expression in transgenic mice. RCS cells expressed both beta-galactosidase and G418 resistance, in comparison with similarly transfected 10T1/2 and NIH/3T3 fibroblasts which did not. These cells were then used to perform a systematic deletion analysis of the first intron of the mouse type II collagen gene (Col2a1) using transient expression experiments to determine which segments stimulated expression of a luciferase reporter gene in RCS cells but not in 10T1/2 fibroblasts. Cloning of two tandem copies of a 156-base pair (bp) intron 1 fragment (+2188 to +2343) in a construction containing a 314-bp Col2a1 promoter caused an almost 200-fold increase in promoter activity in RCS cells but no increase in 10T1/2 cells. DNase I footprint analysis over this 156-bp fragment revealed two adjacent protected regions, FP1 and FP2, located in the 3'-half of this segment, but no differences were seen with nuclear extracts of RCS cells and 10T1/2 fibroblasts. Deletion of FP2 to leave a 119-bp segment decreased enhancer activity by severalfold, but RCS cell specificity was maintained. Further deletions indicated that sequences both in the 5' part of the 119-bp fragment and in FP1 were needed simultaneously for RCS cell-specific enhancer activity. A series of deletions in the promoter region of the mouse Col2a1 gene progressively reduced activity when these promoters were tested by themselves in transient expression experiments. However, these promoter deletions were all activated to a similar level in RCS cells by a 231-bp intron 1 fragment that included the 156-bp enhancer. The RCS cell-specific activity persisted even if the Col2a1 promoter was replaced by a minimal adenovirus major late promoter. This 231-bp intron 1 fragment also had strong enhancing activity in transiently transfected mouse primary chondrocytes. Our experiments establish the usefulness of RCS cells as an experimental system for studies of the control of chondrocyte-specific genes, provide an extensive delineation of segments in the Col2a1 first intron involved in chondrocyte-specific activity, and show that promoter sequences are dispensable for chondrocyte specificity.
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PMID:Use of a new rat chondrosarcoma cell line to delineate a 119-base pair chondrocyte-specific enhancer element and to define active promoter segments in the mouse pro-alpha 1(II) collagen gene. 749 38

Transfer of cytokine genes into tumor cells has proven a valuable approach for cancer treatment. In order to generate a more effective cancer vaccine, we transfected the human interleukin-6 (IL-6) gene into B16 melanoma cells. A B16 cell clone secreting the highest level of IL-6 was obtained by G418-resistant selection, limiting dilution and IL-6 assay. The IL-6-gene-transfected tumor cells exhibited in vitro growth inhibition, reduced tumorigenicity and decreased metastatic competence. After immunization with the inactivated IL-6-gene-transfected vaccine, the murine cytotoxic T lymphocyte activity, natural killer activity and lymphokine-activated killer activity increased markedly. After treatment with the vaccine, the tumor-bearing mice showed significant growth inhibition of subcutaneous tumor, reduction in pulmonary metastases and extension of survival time. The above therapeutic effect was better when low-dose IL-2 was administered simultaneously, although this dosage of IL-2 had no in vivo antitumor effect. These data demonstrated that IL-6-gene-transfected cancer vaccine has a potent antitumor effect via efficient induction of antitumor immunity, and a better therapeutic effect could be achieved when the vaccine is combined with low-dose IL-2 as adjuvant.
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PMID:Induction of antitumor immunity and treatment of preestablished tumor by interleukin-6-gene-transfected melanoma cells combined with low-dose interleukin-2. 749 43

The human osteosarcoma cell line, MG63, responds both to GM-CSF and to G-CSF in vitro. To assess the significance of these observations to tumor growth in vivo, MG63 cells were engineered by retroviral infection to produce human GM-CSF or G-CSF. These retrovirally infected cells become autostimulatory as measured by increased [3H]-thymidine incorporation (3- to 7-fold) and anchorage-independent colony formation (7- to 10-fold) as compared with uninfected MG63 cells or cells infected with control (neor) retrovirus. The increased proliferation induced by exogenous GM-CSF or G-CSF on uninfected MG63 cells in both assays could be completely inhibited by anti-GM-CSF or anti-G-CSF antibodies, while the same antibodies only partially abrogated proliferation by the growth-factor-producing cells. None of 34 nude or SCID mice developed tumors when injected s.c. with uninfected or neor-virus-infected cells. In contrast, all 30 mice injected with GM-CSF- or G-CSF-producing MG63 cells developed tumors which were G418-resistant and factor-producing. Tumor cell DNA showed a polyclonal retroviral integration pattern indistinguishable from that in the DNA of cells injected into mice. Tumors that formed following injection of a mixture of G418-resistant, GM-CSF-producing cells and cells infected with virus containing only the hygror gene contained hygromycin-resistant cells in the same proportion as was present in the original cell mixture. These data indicate that GM-CSF and G-CSF can support the growth of an osteosarcoma cell line both in vitro and in vivo whether the factor is supplied by autocrine production or from exogenous sources.
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PMID:The effect of GM-CSF and G-CSF on the growth of human osteosarcoma cells in vitro and in vivo. 750 89

The murine anti-tenascin monoclonal antibody 81C6, following iodination, has been shown to be an efficient localizing and therapeutic agent in both subcutaneous and intracranial human glioma xenograft models in athymic mice and rats. Similarly, effective monoclonal antibody 81C6 localization has been demonstrated in glioma patients, and Phase I trials with the intact murine IgG2b kappa molecule are currently in progress. In order to maximize the potential for repeated administration by minimizing murine Fc-mediated immunogenicity and reducing Fc-mediated immune effects, we created murine 81C6 variable region/human IgG2 chimeric monoclonal antibodies by the molecular cloning of the variable region genes of mouse 81C6 and their genetic linkage to human constant region exons. The resulting chimeric constructs were introduced into SP2/0 cells, and stable transfectomas were selected by G418 and mycophenolic acid resistance. The resistant clones were screened for anti-tenascin activity on tenascin-coated plates by enzyme-linked immunosorbent assay. The N-terminal amino acid sequence of both heavy and light chains of the purified chimeric 81C6 antibody matched exactly with that of the native mouse 81C6 as well as with that deduced from the nucleotide sequence. The production level of chimeric 81C6 (13.9 mg/ml) from ascites in the highest expressing transfectoma was much higher than that of native mouse 81C6 (2.5 mg/ml). The chimeric antibody showed the same specificity and equivalent affinity for human intact tenascin or tenascin-expressing cells as the native mouse 81C6 antibody. Direct comparison of radioiodinated chimeric and radioiodinated mouse 81C6 biodistribution in subcutaneous and intracranial xenograft-bearing mice showed higher tumor-to-normal tissue ratios for chimeric 81C6 as compared with native mouse 81C6. The improved localizing and clearance characteristics of chimeric 81C6 in xenograft model systems suggests that chimeric 81C6 would be an improved reagent for intracompartmental therapy of tenascin-expressing tumors in the human central nervous system.
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PMID:Generation and characterization of a mouse/human chimeric antibody directed against extracellular matrix protein tenascin. 751 71

Presumptive tumor suppressor genes may be localized to specific chromosomes by the procedure of microcell fusion, whereby individual chromosomes derived from normal human cells are introduced into tumor cells. Allelic loss on chromosome 18 is commonly seen in endometrial carcinoma, and the DCC gene on chromosome 18q is a potential human tumor suppressor gene. In this study, we investigated the hypothesis that a gene on chromosome 18, possibly DCC, is capable of suppressing the tumorigenicity of endometrial carcinoma cells. Microcells from the mouse A9 cell clone containing one human chromosome 18 tagged with the pSV2-neo plasmid were fused with the highly tumorigenic endometrial carcinoma cell lines HHUA and Ishikawa, and G418-resistant microcell hybrids containing and extra copy of chromosome 18 were isolated. Clones isolated from the HHUA cell line were completely suppressed for tumorigenicity in nude mice, and clones from the Ishikawa line were suppressed or inhibited for tumorigenicity. In contrast, growth rates in vitro were not significantly affected in clones from either parental cell line. DCC expression was elevated in most of the suppressed hybrids. These results indicate that a gene on human chromosome 18 is capable of suppressing the tumorigenicity of endometrial carcinoma cells, and that DCC is a candidate for this endometrial carcinoma tumor suppressor gene.
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PMID:Suppression of endometrial carcinoma cell tumorigenicity by human chromosome 18. 754 39

Gene therapy with cytokine cDNA will provide a new tool for cancer treatment. We have already reported that immunization with interleukin-2 (IL2) cDNA transfected Lewis lung carcinoma (LLC) cells induced anti-tumor immunity, which, however, was not strong enough to eradicate an established tumor. In an attempt to develop more effective gene therapy methods, we have used tumor cells co-transfected with IL-2 and tumor necrosis factor (TNF) cDNAs. These cDNAs were introduced into pBMG-Neo and pcDV-X819 vectors, respectively, and then co-transfected into LLC cells. The co-transfectants were selected by incubating them in a medium containing G418 followed by the limiting dilution method twice to obtain IL2 and TNF cDNA co-transfected LLC (LLC-TNF-IL2) cells. When 5 x 10(5)/ml LLC-TNF-IL2 cells were incubated for 48 h, they secreted 7.56 U/ml TNF and 527.0 U/ml IL2 into the culture supernatant. When C57BL/6 mice were transplanted with 1 x 10(6) LLC-TNF-IL2 cells, all the tumors were rejected. The growth of transplanted LLC, but not B16F10 melanoma cells, was retarded in mice inoculated with LLC-TNF-IL2 on their contralateral sides, which suggests specific immunity was induced. The immunization effect by the co-transfectant was superior to that of the IL2- and TNF-transfectants alone.
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PMID:Gene therapy for Lewis lung carcinoma with tumor necrosis factor and interleukin 2 cDNAs co-transfected subline. 758 91


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