Inhibition of the biologic response to insulin-like growth factor I in MCF-7 breast cancer cells by a new monoclonal antibody to the insulin-like growth factor-I receptor. The importance of receptor down-regulation.
We developed a mouse monoclonal antibody (4G11) against insulin-like growth factor I receptor by immunizing mice with mouse embryo fibroblasts overexpressing the human insulin-like growth factor-I receptor. Not only did the 4G11 antibody inhibit the binding of [ (125)I]insulin-like growth factor-I to the fibroblast receptor, but 4G11 antibody also potently down-regulated the insulin-like growth factor-I receptor. 4G11 Fab fragment inhibited ligand binding, but did not down-regulate the receptor, suggesting that receptor aggregation is required for down-regulation. 4G11 antibody also down-regulated the receptor in MCF-7 breast cancer cells, a panel of colon cancer cells and MG-63 osteosarcoma cells. Receptor recovery in MCF-7 cells after down-regulation by 4G11 antibody was slow, requiring 32 - 48 h for full recovery. Receptor down-regulation in MCF-7 cells by 4G11 antibody was confirmed by FACS analysis of intact and permeabilized cells. In contrast to 4G11 antibody, insulin-like growth factor-I did not down-regulate the receptor in MCF-7 cells. Down-regulation of the receptor by 4G11 antibody in MCF-7 cells resulted in inhibition of Akt and MAPK activation by insulin-like growth factor-I. We conclude that the ability of a monoclonal antibody to down-regulate the receptor may be an important antibody property in targeting the insulin-like growth factor-I receptor for the treatment of certain cancers.
Jackson-Booth
P-G
PG
Metabolism Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 USA.
Terry
C
C
Lackey
B
B
Lopaczynska
M
M
Nissley
P
P
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000473:pathology*; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D005260:Female; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000235:genetics*; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000494:pharmacology; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D017526:Receptor, IGF Type 1 / Q000235:genetics* / Q000276:immunology*
D000911:Antibodies, Monoclonal; D007140:Immunoglobulin Fab Fragments; D011518:Proto-Oncogene Proteins; D017526:Receptor, IGF Type 1; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases