S-Adenosylmethionine decarboxylase gene expression is regulated by the cAMP signal transduction pathway in H-ras transformed fibrosarcoma cells capable of malignant progression.
The hypothesis that H-ras transformed cells contain alterations in signalling pathways important in controlling the expression of S-adenosylmethionine decarboxylase, (SAMDC) a highly regulated activity in the biosynthesis of polyamines was tested. Mouse 10 T1/2 fibroblasts and H-ras transformed cell lines of varying degrees of malignant potential were treated with agents which affect cAMP levels within cells. Elevations in SAMDC expression were noted in H-ras transformed metastatic C3 cells, which were not observed in either parental, non-transformed 10 T1/2 fibroblast cells, or in ras transformed NR3 cells, which are only capable of benign tumour formation. Forskolin, a stimulator of cAMP synthesis, was able to increase SAMDC enzyme activity but the response which occurred was dependent upon the cellular phenotype expressed. Actinomycin D pre-treatment of C3 cells prior to exposure to forskolin did not abrogate the elevation observed in SAMDC gene expression suggesting that this was not a transcriptional process mediated event. Forskolin pre-treatment of C3 cells did result in a marked increase in the half-life of SAMDC mRNA transcripts suggesting a role for post-transcriptional stabilization. Furthermore, cycloheximide treatment of malignant C3 cells resulted in elevated SAMDC mRNA levels. Treatment of malignant C3 cells with both cycloheximide and forskolin together resulted in a further additive elevation in SAMDC message levels. Cycloheximide treatment alone was found to affect the half-life of SAMDC mRNA through a mechanism of post-transcriptional stabilization. Additionally, altered SAMDC gene expression in C3 cells which occurred in response to cAMP alterations, was enhanced by stimulation of a protein kinase C pathway suggesting possible interactions between protein kinase C-and cAMP-mediated pathways which affect the regulation of SAMDC expression in highly malignant C3 cells. These results demonstrate aberrant regulation of signalling pathways involved in controlling SAMDC gene expression in H-ras transformed cells capable of malignant progression and provide further insight into the altered growth regulatory program associated with H-ras mediated cellular transformation and malignant progression. J. Cell. Biochem. Suppl. 36: 209-221, 2001.
Hurta
R A
RA
Department of Laboratory Medicine and Pathobiology, St. Michael's Hospital, 38 Shuter St., Toronto, Ontario, Canada, M5B 1A6. hurtar@smh.toronto.on.ca
D012437:Adenosylmethionine Decarboxylase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D015152:Blotting, Northern; D002461:Cell Line, Transformed; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D011905:Genes, ras; D051379:Mice; D009362:Neoplasm Metastasis; D011493:Protein Kinase C / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction
D012333:RNA, Messenger; D005576:Colforsin; D000242:Cyclic AMP; D011493:Protein Kinase C; D012437:Adenosylmethionine Decarboxylase