INHIBITION OF CELL-PROLIFERATION BY AN ADENOVIRUS VECTOR EXPRESSING THE HUMAN WILD TYPE-P53 PROTEIN
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We have developed human adenovirus 5 (Ad5) vectors expressing the wild type human p53 protein or a mutant p53 form under the control of the human cytomegalovirus immediate early gene promoter. Human cells infected with these vectors expressed high levels of p53, accumulating 20-40 fold more protein than found in normal human fibroblasts. The ability of the vectors to affect proliferation of cells in culture was assessed by measuring cell DNA synthesis and colony forming ability after infection with viruses. When the p53 deficient ovarian carcinoma cell line, SKOV-3, was infected with Adp53wt expressing the wild type (wt) p53 protein, a significant inhibition of cellular DNA synthesis was observed, relative to cells infected with Adp53m expressing mutant p53, or a control virus, AdLacZ, expressing bacterial beta-galactosidase. Inhibition was dependent on multiplicity of infection, with no significant effect below 5 pfu/cell, and maximal effect between 25 and 100 PFU/cell which resulted in approximately 95% inhibition of SKOV-3 cell DNA synthesis relative to mock infected cells. Infection of normal human fibroblasts with Adp53wt also inhibited DNA synthesis but to a significantly lesser degree. SKOV-3 cell survival, assayed by ability to form colonies, was reduced at least 10 fold after infection with Adp53wt compared to colony forming ability of cells after infection with either AdLacZ or Adp53m. The results of these studies indicate that p53 expressed by Ad vectors can inhibit proliferation in culture of p53 negative cells by at least 95%, and suggest that such vectors might similarly inhibit the proliferation of tumor cells in vivo.
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