Inhibitory regulation of serum factor(s)-caused ornithine decarboxylase induction by the protein kinase C system in A431 human epidermoid carcinoma cells.
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.
Nakadate
T
T
Department of Pharmacology, School of Medicine, Keio University, Tokyo, Japan.
Yamamoto
S
S
Kamegaya
Y
Y
Ishihara
M
M
Aizu
E
E
Jiang
H
H
Kato
R
R
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
D011493:Protein Kinase C; D009955:Ornithine Decarboxylase; D013755:Tetradecanoylphorbol Acetate