Overexpression of insulin receptors in fibroblast and ovary cells induces a ligand-mediated transformed phenotype.
To investigate whether overexpression of the insulin receptor results in altered cell growth we used NIH 3T3 cells transfected with a bovine papilloma virus/insulin receptor cDNA construct (3T3/HIR). These cells expressed high numbers of insulin receptors (mean +/- sd, 631.0 +/- 16.7 ng receptors/10(6) cells). Insulin significantly stimulated the growth of 3T3/HIR cells maintained in serum-free medium. Moreover, in these cells, insulin induced marked phenotypic changes, including alterations in cell shape, loss of contact inhibition, and focal growth. In contrast to 3T3/HIR cells, insulin was without effect in either wild-type 3T3 cells (3T3/wt), 3T3 cells transfected with the neomycin resistance gene (3T3/NEO), or the bovine papilloma virus (3T3/BPV). To assess the presence of anchorage-independent growth, cells were seeded in soft agar and inspected for colony formation. 3T3/HIR cells showed absent or minimal colony growth in the absence of insulin. However, there was a dose-dependent insulin-stimulated increase in both colony size and number. Insulin-stimulated colony formation was specifically inhibited by an insulin antagonist, monoclonal antibody MA-10. In the presence of 100 nM insulin, about 3% of cells formed large colonies. Insulin neither stimulated growth nor induced colony formation in 3T3/wt cells or 3T3/NEO cells. Insulin also stimulated colony formation in CHO cells transfected with an insulin receptor cDNA construct. In conclusion, overexpression of normal insulin receptors induces a ligand-dependent transformed phenotype. This phenomenon may have clinical relevance by conferring a selective growth advantage to tumor cells with high numbers of insulin receptors.
Giorgino
F
F
Cattedra di Endocrinologia, Università di Catania, Ospedale Garibaldi, Italy.
Belfiore
A
A
Milazzo
G
G
Costantino
A
A
Maddux
B
B
Whittaker
J
J
Goldfine
I D
ID
Vigneri
R
R
D000362:Agar; D000818:Animals; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D004351:Drug Resistance / Q000235:genetics; D005260:Female; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D015870:Gene Expression; D007328:Insulin / Q000494:pharmacology; D051379:Mice; D008819:Mice, Nude; D009355:Neomycin / Q000494:pharmacology; D010053:Ovary / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D027383:Papillomaviridae / Q000235:genetics; D010641:Phenotype; D011972:Receptor, Insulin / Q000235:genetics*; D014162:Transfection; D014170:Transformation, Genetic
D007328:Insulin; D000362:Agar; D004247:DNA; D011972:Receptor, Insulin; D009355:Neomycin