Insulin Receptor (IR) Pathway Hyperactivity in IGF-IR Null Cells and Suppression of Downstream Growth Signaling Using the Dual IGF-IR/IR Inhibitor, BMS-754807

• Published in: Endocrinology (Philadelphia) 2010-09, Vol.151 (9), p.4123-4132
• Main Authors: Dinchuk, Joseph E, Cao, Carolyn, Huang, Fei, Reeves, Karen A, Wang, Jeanne, Myers, Fanny, Cantor, Glenn H, Zhou, Xiadi, Attar, Ricardo M, Gottardis, Marco, Carboni, Joan M
• Format: Article
• Language: English
• Subjects: AKT protein; Animals; Attention deficit disorders. Hyperactivity; Biological and medical sciences; Blotting, Western; Cell Proliferation - drug effects; Cells, Cultured; Child clinical studies; Cluster Analysis; Embryo fibroblasts; Embryo, Mammalian - cytology; Extracellular Signal-Regulated MAP Kinases - metabolism; Female; Fibroblasts - cytology; Fibroblasts - drug effects; Fibroblasts - metabolism; Fundamental and applied biological sciences. Psychology; Gene expression; Gene Expression Profiling; Hypersensitivity; Inhibitors; Insulin; Insulin - pharmacology; Insulin receptors; Insulin-like growth factor I; Insulin-Like Growth Factor I - pharmacology; Insulin-like growth factor I receptors; Insulin-like growth factor II; Insulin-Like Growth Factor II - pharmacology; Isoforms; Ligands; Male; Medical sciences; Mice; Mice, Inbred C57BL; Mice, Inbred Strains; Mice, Knockout; Null cells; Phosphorylation; Phosphorylation - drug effects; Proto-Oncogene Proteins c-akt - metabolism; Psychology. Psychoanalysis. Psychiatry; Psychopathology. Psychiatry; Pyrazoles - pharmacology; Receptor, IGF Type 1 - antagonists & inhibitors; Receptor, IGF Type 1 - genetics; Receptor, IGF Type 1 - metabolism; Receptor, Insulin - antagonists & inhibitors; Receptor, Insulin - genetics; Receptor, Insulin - metabolism; Receptors; Reverse Transcriptase Polymerase Chain Reaction; Signal transduction; Signal Transduction - drug effects; Stimulation; Triazines - pharmacology; Vertebrates: endocrinology
• ISSN: 0013-7227; 1945-7170
• DOI: 10.1210/en.2010-0032

The biology of IGF-IR/IR signaling was studied in normal mouse embryonic fibroblasts (MEFs) that were either wild type (wt), heterozygous (het), or null for the IGF-IR. The ability of IGF-I, IGF-II, or insulin to stimulate serum-starved MEFs was characterized by gene expression profiling and biochemical analyses for activation of downstream signals. Each genotypic group of MEFs exhibited distinct patterns of expression both while resting and in response to stimulation. The insulin receptor (IR) pathway in IGF-IR null MEFs was hypersensitive to insulin ligand stimulation resulting in greater AKT phosphorylation than in wt or het MEFs stimulated with the same ligand. Interestingly, the IR pathway hypersensitivity in IGF-IR null MEFs occurred with no observed changes in the levels of IR isoforms A or B. A new small molecule IGF-IR inhibitor (BMS-754807), having equipotent activity against both IGF-IR and IR, proved effective in suppressing both AKT and ERK phosphorylation from both the IGF-IR and IR pathways by all three ligands tested in wt, het, and null MEFs. The use of a dual IGF-IR/IR inhibitor addresses concerns about the use of growth inhibiting therapies directed against the IGF-IR receptor in certain cancers. Lastly, comparison of the antiproliferative effects (IC50s) of various compounds in wt vs. null MEFs demonstrates that genetically characterized MEFs provide a simple and inexpensive tool with which to define compounds as having mostly on-target or off-target IGF-IR activities because off-target compounds affect both wt and null MEFs equally. In murine embryonic fibroblasts with a genetic deletion of the IGF-IR, the insulin receptor (IR) growth pathway becomes hyperactivated in the absence of changes in IR protein levels, mRNA levels, or mRNA splicing.