title: c-Myc antisense limits rat liver regeneration and indicates role for c-Myc in regulating cytochrome P-450 3A activity.
abstract: Expression of c-myc protein is associated with cell proliferation. The present study uses antisense oligomers to inhibit c-myc expression in the regenerating rat liver after 70% partial hepatectomy (PH). Antisense phosphorodiamidate morpholino oligomers (novel DNA analogs) were administered i.p. immediately after surgery to block expression of c-myc within the first 24 h after PH. A 20-mer PMO complimentary to the c-myc mRNA at the translation start site was an effective sequence (AVI-4126, 5'-ACGTTGAGGGGCATCGTCGC-3'). A single i.p. dose of 0.5 mg/kg AVI-4126 caused reduction of the regenerating liver c-myc protein in a sequence-specific and dose-dependent manner. Inhibition of c-myc expression resulted in reduction of proliferating cell nuclear antigen and arrested cells in the G(0)/G(1) phase of the cell cycle. The ratio of G(2):G(0) cell populations in the regenerating liver 24 h after PH dropped from 29.1 in saline vehicle-treated rats to 18.0 in rats treated with 2.5 mg/kg AVI-4126. The expression of cell cycle checkpoint protein p53 was inhibited with increasing doses of AVI-4126, but expression of p21(waf-1) was unaffected. The activity of cytochrome P-450 3A2 (CYP3A2) was evaluated by immunoblot analysis and erythromycin N-demethylation. AVI-4126 did not alter CYP3A activity in nonhepatectamized animals but showed a dose-dependent decrease in PH rats. We conclude that AVI-4126, antisense oligomer to c-myc, can reduce cell proliferation in the regenerating rat liver. Furthermore, inhibition of c-myc may indirectly influence the expression of CYP3A.
authors.affiliation: AVI BioPharma, Corvallis, Oregon, USA.
authors.forename: V
authors.initials: V
authors.lastname: Arora
authors.forename: D C
authors.initials: DC
authors.lastname: Knapp
authors.forename: B L
authors.initials: BL
authors.lastname: Smith
authors.forename: M L
authors.initials: ML
authors.lastname: Statdfield
authors.forename: D A
authors.initials: DA
authors.lastname: Stein
authors.forename: M T
authors.initials: MT
authors.lastname: Reddy
authors.forename: D D
authors.initials: DD
authors.lastname: Weller
authors.forename: P L
authors.initials: PL
authors.lastname: Iversen
mesh_terms: D000818:Animals; D016375:Antisense Elements (Genetics) / Q000494:pharmacology*; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000032:analysis; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D016195:G2 Phase; D016259:Genes, myc / Q000502:physiology*; D006498:Hepatectomy; D008099:Liver / Q000201:enzymology*; D008115:Liver Regeneration / Q000187:drug effects*; D018809:Proliferating Cell Nuclear Antigen / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D013250:Steroid Hydroxylases / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000032:analysis
chemical_list: D016375:Antisense Elements (Genetics); C493958:Cdkn1a protein, rat; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D018809:Proliferating Cell Nuclear Antigen; D016159:Tumor Suppressor Protein p53; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; C022657:steroid hormone 6-beta-hydroxylase