Nonresponsiveness of an SV40-transformed BALB/C-3T3 cell line to PDGF mitogenicity is correlated with an irreversible reduction in PDGF receptor number

The effect of SV40 transformation on the mitogenic responsiveness of Balb/c-3T3 cells to platelet-derived growth factor was examined. The SV40 transformed cell line (SV40-3T3) did not require exogenous PDGF for growth in a serum-free medium containing insulin, transferrin and high density lipoprotein as macromolecular supplements. The SV40-3T3 cells were found to have undetectable PDGF-stimulated PDGF receptor autophosphorylation and markedly reduced PDGF binding. PDGF-induced PDGF receptor autophosphorylation and PDGF binding of the normal 3T3 cells were not reduced by incubation with conditioned medium from SV40 transformed cells; nor could PDGF binding to SV40-3T3 be increased by an 8-hour incubation with 0.5 mM suramin, a compound known to prevent the binding of PDGF to its receptor. These data suggest that SV40-3T3 cells do not produce PDGF in quantities that are sufficient to down regulate their PDGF receptor and suggest that the reduced PDGF responsiveness and PDGF receptor number in SV40-3T3 cells may be a reflection of a more permanent, perhaps genetic, alteration.