Tumors induced in mice by direct inoculation of plasmid DNA expressing both activated H-ras and c-myc.
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.
Sheng-Fowler
Li
L
Division of Viral Products, OVRR, CBER, FDA, Bethesda, MD 20892, USA.
Cai
Fang
F
Fu
Haiqing
H
Zhu
Yong
Y
Orrison
Brian
B
Foseh
Gideon
G
Blair
Don G
DG
Hughes
Stephen H
SH
Coffin
John M
JM
Lewis
Andrew M
AM
Peden
Keith
K
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*
D016271:Proto-Oncogene Proteins c-myc; D004247:DNA; D018631:ras Proteins