Inhibition of initiator‐induced SV40 gene amplification in SV40‐transformed Chinese hamster cells by infection with a defective parvovirus

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Abstract
Amplification of SV40 genes in SV40‐transformed Chinese hamster embryo cells (CO631) by chemical carcinogens as well as by herpes simplex virus infection can be inhibited by infection with the defective parvovirus, AAV‐5. This is shown by in situ hybridization with SV40 DNA of AAV‐5‐infected CO631 cells after treatment with herpes simplex virus type I or with chemical carcinogens: the initiator‐induced selective amplification of SV40 sequences is prevented in the presence of the parvovirus. During HSV‐infection and also in the presence of carcinogens, in CO631 cells parvovirus DNA is synthesized and AAV‐5‐specific antigens are expressed as revealed by hybridization with cloned AAV‐5 DNA or by immuno‐fluorescence with monoclonal antibodies, respectively. The inhibition of initiator‐induced gene amplification could point to the mechanism of parvovirus‐mediated inhibition of tumor development and may indicate an important role of selective gene amplification in oncogenesis.