title: Inhibitory regulation of serum factor(s)-caused ornithine decarboxylase induction by the protein kinase C system in A431 human epidermoid carcinoma cells.
abstract: Replacement of the culture medium with fresh medium containing 10% fetal calf serum caused ornithine decarboxylase (ODC) induction in A431 human epidermoid carcinoma cells. Two peaks of ODC activity were observed at 5 and 14 hr after the medium replacement. The peak activity observed at 5 hr was more prominent than that at 14 hr. The first peak of ODC induction was suppressed by a potent protein kinase C activator, 12-O-tetradecanoylphorbol-13-acetate (TPA), in a concentration-dependent manner. The second peak, however, was not suppressed by TPA. Other potent protein kinase C activators, such as mezerein and 12-O-retinoylphorbol-13-acetate, also suppressed the first peak of ODC induction. Synthetic diacylglycerols, 1,2-dioctanoyl-sn-glycerol and 1-oleoyl-2-acetylglycerol, did not inhibit the serum factor(s)-caused ODC induction. Phorbol-13-acetate, an inactive phorbol ester, also failed to inhibit the ODC induction. The growth of A431 cells was slightly suppressed by TPA. In protein kinase C down-regulated cells, TPA failed to inhibit the serum factor(s)-caused ODC induction. These results suggest that the serum factor(s)-caused ODC induction in A431 cells is negatively regulated by the protein kinase C system, which may not be activated by exogenous diacylglycerols.
authors.affiliation: Department of Pharmacology, School of Medicine, Keio University, Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Nakadate
authors.forename: S
authors.initials: S
authors.lastname: Yamamoto
authors.forename: Y
authors.initials: Y
authors.lastname: Kamegaya
authors.forename: M
authors.initials: M
authors.lastname: Ishihara
authors.forename: E
authors.initials: E
authors.lastname: Aizu
authors.forename: H
authors.initials: H
authors.lastname: Jiang
authors.forename: R
authors.initials: R
authors.lastname: Kato
mesh_terms: D001769:Blood; D002294:Carcinoma, Squamous Cell / Q000201:enzymology*; D015536:Down-Regulation; D004789:Enzyme Activation; D004790:Enzyme Induction / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D009955:Ornithine Decarboxylase / Q000096:biosynthesis*; D011493:Protein Kinase C / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D011493:Protein Kinase C; D009955:Ornithine Decarboxylase; D013755:Tetradecanoylphorbol Acetate