Differentiated genotoxic response of carcinogenic and non-carcinogenic benzacridines and metabolites in rat hepatoma cells.

Two closely related hepatoma cell lines were examined for their genotoxic response to benacridines and their metabolites by the appearance of alkaline labile DNA sites: H5, a dedifferentiated line expressing cytochrome P-448-dependent mono-oxygenase(s); and HF1-4, a differentiated line expressing cytochrome P-450-dependent monooxygenase(s). The parent heterocycles had no effect on both cell lines. In contrast to the 3,4-dihydrodiol of benz[c]acridine the 3,4-dihydrodiol of benz[a]acridine induced no DNA strand breaks in both cell lines.

Inactivation of the thymidine kinase gene after in vitro modification with benzo(a)pyrene-diol-epoxide and transfer to LTK- cells as a eukaryotic test for carcinogens.

A recombinant plasmid containing the thymidine kinase (TK) gene (pAGO; 6.36 kilobases) was reacted in vitro with (+/-)-7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene, an ultimate carcinogenic metabolite of benzo(a)pyrene. The covalent binding of the metabolite to the circular forms of pAGO was visible by a drastic change in their mobility during agarose gel electrophoresis.

Enhanced production of hepatitis B surface antigen in NIH 3T3 mouse fibroblasts by using extrachromosomally replicating bovine papillomavirus vector.

We have constructed a recombinant pBR322 plasmid composed of a subgenomic transforming fragment of bovine papillomavirus DNA and the hepatitis B surface antigen gene from cloned hepatitis B virus DNA and used it for transfection of NIH 3T3 mouse fibroblasts. The transformed cells retain the plasmids in extrachromosomal form with a copy number of about 50 to 100 per cell. Expression of the hepatitis B surface antigen gene linked to bovine papillomavirus DNA is independent of its orientation relative to the bovine papillomavirus vector.

Liposomes as gene carriers: efficient transformation of mouse L cells by thymidine kinase gene.

Stable transformation of mouse L cells deficient in thymidine kinase was achieved by liposome-mediated transfer of a recombinant plasmid carrying the thymidine kinase gene. Ten percent of the recipient cells expressed thymidine kinase activity. The transformed phenotype (for example, 200 out of 10(6) cells) was stable under selective and nonselective conditions.