Dissociation of carcinogen-induced SV40 DNA-amplification and amplification of AAV DNA in a Chinese hamster cell line.

Time kinetics of AAV-5 DNA amplification induced by MNNG in cells of a Chinese hamster line (CO631) and a Syrian hamster line (Elona) were compared to kinetics of SV40 DNA amplification in these cells. AAV-5 DNA amplification starts in both lines about 8 hr following treatment of AAV-infected cells with MNNG. SV40 DNA amplification is induced only in CO631 cells. The time it becomes detectable varies but in no case was before 23 hr after MNNG treatment. In CO631 cells a second round of AAV DNA amplification takes place. It starts at times paralleling the MNNG-induced synthesis of SV40 DNA but appears to be independent of genotoxic treatment. Elona cells amplify neither SV40 DNA after exposure to chemical carcinogens nor AAV-5 DNA in untreated cells. In both lines combined treatment with MNNG and AAV-5 resulted in marked cytopathogenic changes and cell death. In the test systems used here viral DNA amplification did not lead to synthesis of infectious virus, thus, the viral cycle remained abortive.