title: Tumors induced in mice by direct inoculation of plasmid DNA expressing both activated H-ras and c-myc.
abstract: Vaccines contain residual DNA derived from the cells used to produce them. As part of our investigation to assess the risk of this cellular DNA, we are developing a quantitative in vivo assay to assess the oncogenicity of DNA. In an earlier study, we had generated expression plasmids for two oncogenes--human activated T24-H-ras and murine c-myc--and had shown that these two plasmids, pMSV-T24-H-ras and pMSV-c-myc, could act in concert to induce tumors in mice, although the efficiency was low. In this study, we took two approaches to increase the oncogenic efficiency: 1) both oncogene-expression cassettes were placed on the same plasmid; 2) transfection facilitators, which increase DNA uptake and expression in vitro, were tested. The dual-expression plasmid, pMSV-T24-H-ras/MSV-c-myc, is about 20-fold more efficient at tumor induction in newborn NIH Swiss mice than the separate expression plasmids, with tumors being induced with 1 microg of the dual-expression plasmid DNA. However, none of the transfection facilitators tested increased the efficiency of tumor induction. Based on these data, the dual-expression plasmid pMSV-T24-H-ras/MSV-c-myc will be used as the positive control to develop a sensitive and quantitative animal assay that can be used to assess the oncogenic activity of DNA.
authors.affiliation: Division of Viral Products, OVRR, CBER, FDA, Bethesda, MD 20892, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Sheng-Fowler
authors.forename: Fang
authors.initials: F
authors.lastname: Cai
authors.forename: Haiqing
authors.initials: H
authors.lastname: Fu
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhu
authors.forename: Brian
authors.initials: B
authors.lastname: Orrison
authors.forename: Gideon
authors.initials: G
authors.lastname: Foseh
authors.forename: Don G
authors.initials: DG
authors.lastname: Blair
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Hughes
authors.forename: John M
authors.initials: JM
authors.lastname: Coffin
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Lewis
authors.forename: Keith
authors.initials: K
authors.lastname: Peden
mesh_terms: D000818:Animals; D004247:DNA / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D041681:NIH 3T3 Cells; D009369:Neoplasms / Q000378:metabolism*; D009857:Oncogenes; D010957:Plasmids / Q000378:metabolism*; D016133:Polymerase Chain Reaction / Q000379:methods; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D051381:Rats; D014162:Transfection; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D016271:Proto-Oncogene Proteins c-myc; D004247:DNA; D018631:ras Proteins