The growth-stimulatory effect of simian virus 40 T antigen requires the interaction of insulinlike growth factor 1 with its receptor.
We have used a plasmid expressing a temperature-sensitive (ts) mutant of simian virus 40 (SV40) T antigen, stably transfected into 3T3 cells, to study the role of insulinlike growth factor 1 (IGF-1) and its receptor in T-antigen-mediated growth. While 3T3 cells do not grow in serum-free medium, in 1% serum, or with the sole addition of either platelet-derived growth factor (PDGF) or IGF-1, cells expressing the tsA T antigen (BALB 58 cells) grow at 34 degrees C in either PDGF or 1% serum but not in IGF-1. At the restrictive temperature (39.6 degrees C), these cells can only grow in 10% serum. We show that BALB 58 cells, at 34 degrees C, have a markedly increased expression of IGF-1 and IGF-1 mRNA and that their growth in 1% serum (at 34 degrees C) is inhibited by an antisense oligodeoxynucleotide to the IGF-1 receptor RNA. When this tsA plasmid is stably transfected into cells constitutively overexpressing the human IGF-1 receptor cDNA, the resulting cell lines show a constitutively phosphorylated IGF-1 receptor and grow in serum-free medium at 34 degrees C (but not at 39.6 degrees C). A functional SV40 T antigen also increases the expression of a plasmid in which the reporter luciferase gene is under the control of a rat IGF-1 promoter. We conclude (i) that the SV40 T antigen induces the expression of IGF-1 and IGF-1 mRNA, at least in part by a transcriptional mechanism, thus altering the growth factors requirements, and (ii) that, in BALB/c3t3 cells, the SV40 T antigen necessitates a functional IGF-1 receptor for its growth-stimulating effect in low serum (or PDGF).
Porcu
P
P
Jefferson Cancer Institute, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
Ferber
A
A
Pietrzkowski
Z
Z
Roberts
C T
CT
Adamo
M
M
LeRoith
D
D
Baserga
R
R
D016475:3T3 Cells; D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000502:physiology*; D001483:Base Sequence; D002455:Cell Division; D002472:Cell Transformation, Viral; D004247:DNA; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D015183:Restriction Mapping; D013696:Temperature
D000952:Antigens, Polyomavirus Transforming; D007334:Insulin-Like Growth Factor I; D004247:DNA; D017526:Receptor, IGF Type 1