Abstract
The rapidly proliferating cells of the regenerating liver after partial hepatectomy (PH) present a reproducible in vivo model to study the functional role of the tumor suppressor gene p53. The present study uses the rat 70% PH model along with systemic administration of three different structural types of antisense oligonucleotides (ODNs) designed to suppress p53 expression. We tested the hypothesis that antisense ODNs can inhibit the expression of p53, resulting in the loss of the G1-S cell cycle checkpoint and an altered pattern of liver regeneration. Intraperitoneal administration of 5 mg/kg/day antisense phosphorothioate ODN after 70% PH resulted in reduced expression of the p53 protein in the regenerating liver. There were concomitant increases in weight gain of remnant-regenerating liver and expression of proliferating cell nuclear antigen and p21waf-1 compared with either saline or 5 mg/kg/day mispaired phosphorothioate ODN treatment. Flow cytometric analysis of DNA content of isolated hepatocytes revealed a reduction in the G0/G1 cell population and accumulation of cells with more than 4n DNA in antisense-treated rats. The regenerating livers had significantly diminished cytochrome P-450 (CYP) enzyme activities. Rats treated with p53 antisense ODNs, but not saline or mispair ODN controls, had significantly elevated CYP activities. These observations functionally link the expression of p53 with diminished expression of several CYP isoforms in the liver regeneration model.
Footnotes
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Send reprint requests to: Dr. Patrick L. Iversen, AVI Biopharma, Inc., 4575 S.W. Research Way, Suite 200, Corvallis, OR 97333. E-mail: piversen{at}avibio.com
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This study was supported in part by USPHS Grant GM54871. V.A. received fellowship support from Nebraska Research Initiative in Biotechnology.
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1 Present address: AVI Biopharma, 4575 S.W. Research Way, Suite 200, Corvallis, OR 97333.
- Abbreviations used are::
- PH
- partial hepatectomy
- ODN
- oligodeoxynucleotide
- PS-ODN
- phosphorothioate ODN
- C-5-P
- cytosine C-5 propynyl
- PCNA
- proliferating cell nuclear antigen
- MI
- mitotic index
- CYP
- cytochrome P-450
- TBARS
- thiobarbituric acid-reactive substances
- rcf
- relative centrifugal force
- Received June 10, 1999.
- Accepted October 12, 1999.
- The American Society for Pharmacology and Experimental Therapeutics
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