Scientific Publications by FDA Staff

Biologicals 2008 May;36(3):184-97

Oncogenicity of DNA in vivo: Tumor induction with expression plasmids for activated H-ras and c-myc.

Sheng L, Cai F, Zhu Y, Pal A, Athanasiou M, Orrison B, Blair DG, Hughes SH, Coffin JM, Lewis AM, Peden K

Peden, K (reprint author), US FDA, Div Viral Prod, OVRR, CBER, Bldg 29A,Room 3D08 29 Lincoln Dr, Bethesda, MD 20892 USA US FDA, Div Viral Prod, OVRR, CBER, Bethesda, MD 20892 USA NCI, Frederick Canc Res Facil, Frederick, MD 21701 USA Tufts Univ, Dept Microbiol & Mol Biol, Boston, MA 02111 USA

All vaccines and other biological products contain contaminating residual DNA derived from the production cell substrate. Whether this residual cell-substrate DNA can induce tumors in vaccine recipients and thus represent a risk factor has been debated for over 50years without resolution. As a first step in resolving this issue, we have generated expression plasmids for the activated human H-ras oncogene and for the murine c-myc proto-oncogene. Their oncogenic activity was confirmed in vitro using the focus-formation transformation assay. Two strains of adult and newborn immune-competent mice were inoculated with different amounts of either plasmid alone or with a combination of the H-ras and c-myc plasmids. Tumors developed only in mice inoculated with both plasmids and only at the highest amount of DNA (12.5mug of each plasmid). The NIH Swiss mouse was more sensitive than the C57BL/6 mouse, and newborn animals were more sensitive than adults. Cell lines were established from the tumors. PCR and Southern hybridization analyses demonstrated that both inoculated oncogenes were present in all of the tumor-derived cell lines and that the cells in the tumors were clonal. Western analysis demonstrated that both oncoproteins were expressed in these cell lines. These results demonstrate that cellular oncogenes can induce tumors following subcutaneous inoculation. Such information provides a possible way of evaluating and estimating the theoretical oncogenic risk posed by residual cell-substrate DNA in vaccines.