Constitutive expression of the c-fos protooncogene in murine keratinocytes: potentiation of the mitogenic response to insulin-like growth factor 1.
In order to determine the biological effects of activation of the c-fos protooncogene on growth and differentiation of BALB/MK mouse keratinocytes, these cells were transfected with the plasmid pMAN-fos, which encompasses the human c-fos coding region under transcriptional control of a mouse mammary tumor virus promoter, as well as the gene encoding neomycin phosphotransferase. Of approximately 70 individual clones obtained by selection in Geneticin, 5 clones that constitutively expressed c-fos mRNA as well as p55fos protein were selected for phenotypic analysis. Each of these clones displayed density-dependent growth arrest at confluency when deprived of serum and mitogens. DNA synthesis could be reinitiated in quiescent cultures by treatment with epidermal growth factor to a similar extent as in the parental line. In four of five fos transfectants, insulin-like growth factor 1 potentiated the mitogenic response to epidermal growth factor more than 10-fold, compared to only 2.5-fold in the parental cells. The enhanced response to insulin-like growth 1 could not be attributed to changes in the number or the affinity of receptors for the growth factor. Finally, the constitutive expression of c-fos did not interfere with the induction of terminal differentiation by calcium.
Reiss
M
M
Department of Medicine, Yale Comprehensive Cancer Center, Yale University School of Medicine, New Haven, Connecticut 06510.
Radin
A I
AI
Weisberg
T F
TF
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D004247:DNA / Q000378:metabolism; D015870:Gene Expression; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D015603:Keratinocytes / Q000166:cytology*; D051379:Mice; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D016760:Proto-Oncogene Proteins c-fos; D011519:Proto-Oncogenes; D012333:RNA, Messenger / Q000032:analysis; D011956:Receptors, Cell Surface / Q000032:analysis; D017451:Receptors, Somatomedin; D014162:Transfection
D011518:Proto-Oncogene Proteins; D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D007334:Insulin-Like Growth Factor I; D004247:DNA; D002118:Calcium