Regulation of c-myc mRNA levels by insulin or platelet-poor plasma.
Cell lines have been permanently established from BALB/c3T3 cells that constitutively express either the murine p53, the human IGF-1 gene, or both (Gai et al., 1988). The derivative cell lines grow well in platelet-poor plasma or in serum-free medium supplemented with the appropriate growth factors, while BALB/c3T3 cells do not grow in platelet-poor plasma, nor do they grow in serum-free medium unless supplemented with both platelet-derived growth factor and insulin (or IGF-1). In BALB/c3T3 cells, steady-state levels of c-myc mRNA decrease promptly and sharply once the cells are transferred to platelet-poor plasma. In the derivative cell lines, constitutively expressing p53, IGF-1, or both, c-myc mRNA levels remain elevated and actually increase when the cells are transferred to platelet-poor plasma. In serum-free medium, the c-myc mRNA levels decreased in BALB/c3T3 cells, as well as in the derivative cell lines. However, in the latter cell lines, but not in BALB/c3T3, the addition of platelet-poor plasma or insulin again increased the expression of c-myc. The increase in c-myc mRNA levels could be partially explained by an increase in transcription. These results indicate that in certain cell lines the expression of c-myc mRNA can be induced by insulin or platelet-poor plasma.
Gai
X X
XX
Department of Pathology, Temple University Medical School, Philadelphia, Pennsylvania 19140.
Rizzo
M G
MG
Valpreda
S
S
Baserga
R
R
D000818:Animals; D001790:Blood Physiological Phenomena; D002455:Cell Division; D002460:Cell Line; D003470:Culture Media; D006736:Horses; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D010982:Platelet-Derived Growth Factor / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D016271:Proto-Oncogene Proteins c-myc; D011519:Proto-Oncogenes; D012333:RNA, Messenger / Q000032:analysis*; D014158:Transcription, Genetic
D003470:Culture Media; D007328:Insulin; D010982:Platelet-Derived Growth Factor; D011518:Proto-Oncogene Proteins; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger