Differential induction of 12-O-tetradecanoylphorbol-13-acetate sequence gene expression in murine melanocytes and melanoma cells.
We previously showed that growth of the nontumorigenic, immortal murine melanocyte line Mel-ab correlates with the depletion of protein kinase C (PKC), whereas quiescence is associated with elevated levels of this enzyme (Brooks G, et al., Cancer Res 51: 3281-3288, 1991). Here we report responses that occur in these cells downstream of PKC activation or downregulation. We examined induction of 12-O-tetradecanoylphorbol-13-acetate (TPA)-inducible sequence (TIS) gene expression in Mel-ab melanocytes and in their transformed counterparts, B16 melanoma cells. Exposure of quiescent Mel-ab cells to the PKC-activating phorbol esters TPA or sapintoxin A at 81 nM for 2 h increased levels of mRNA for six of seven TIS genes examined (twofold to 80-fold increase in steady-state RNA levels for TIS 1, 7, 8, 11, 21, and 28 (c-fos); TIS 10 expression was not affected). No induction of TIS gene expression was observed either in growing Mel-ab cells maintained in 324 nM phorbol 12,13-dibutyrate or in B16 cells previously unexposed to phorbol esters, in which normal PKC levels were endogenously depressed. The cAMP-elevating agents choleratoxin (10 nM) and dibutyryl cyclic AMP (2.5 mM) increased levels of TIS mRNA (with the exception of TIS 10) in both proliferating Mel-ab and B16 cells, suggesting that downregulation of the PKC pathway is specific and not a consequence of a general inhibition of all signalling pathways.
Brooks
G
G
Biology of Metastasis Laboratory, Imperial Cancer Research Fund, London, United Kingdom.
Goss
M W
MW
Hart
I R
IR
D016475:3T3 Cells; D000818:Animals; D015152:Blotting, Northern; D003994:Bucladesine / Q000494:pharmacology; D002461:Cell Line, Transformed; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D016762:Genes, fos; D008544:Melanocytes / Q000187:drug effects / Q000502:physiology*; D008546:Melanoma, Experimental / Q000235:genetics*; D051379:Mice; D008970:Molecular Weight; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects; D014407:Tumor Cells, Cultured
D012333:RNA, Messenger; D015240:Phorbol 12,13-Dibutyrate; D012313:RNA; D003994:Bucladesine; D003513:Cycloheximide; D013755:Tetradecanoylphorbol Acetate