title: Differential insulin-like growth factor I receptor signaling and function in estrogen receptor (ER)-positive MCF-7 and ER-negative MDA-MB-231 breast cancer cells.
abstract: The insulin-like growth factor I receptor (IGF-IR) is a ubiquitous and multifunctional tyrosine kinase that has been implicated in breast cancer development. In estrogen receptor (ER)-positive breast tumors, the levels of the IGF-IR and its substrate, insulin-receptor substrate 1 (IRS-1), are often elevated, and these characteristics have been linked with increased radioresistance and cancer recurrence. In vitro, activation of the IGF-IR/IRS-1 pathway in ER-positive cells improves growth and counteracts apoptosis induced by anticancer treatments. The function of the IGF-IR in hormone-independent breast cancer is not clear. ER-negative breast cancer cells often express low levels of the IGF-IR and fail to respond to IGF-I with mitogenesis. On the other hand, anti-IGF-IR strategies effectively reduced metastatic potential of different ER-negative cell lines, suggesting a role of this receptor in late stages of the disease. Here we examined IGF-IR signaling and function in ER-negative MDA-MB-231 breast cancer cells and their IGF-IR-overexpressing derivatives. We demonstrated that IGF-I acts as a chemoattractant for these cells. The extent of IGF-I-induced migration reflected IGF-IR levels and required the activation of phosphatidylinositol 3-kinase (PI-3K) and p38 kinases. The same pathways promoted IGF-I-dependent motility in ER-positive MCF-7 cells. In contrast with the positive effects on cell migration, IGF-I was unable to stimulate growth or improve survival in MDA-MB-231 cells, whereas it induced mitogenic and antiapoptotic effects in MCF-7 cells. Moreover, IGF-I partially restored growth in ER-positive cells treated with PI-3K and ERK1/ERK2 inhibitors, whereas it had no protective effects in ER-negative cells. The impaired IGF-I growth response of ER-negative cells was not caused by a low IGF-IR expression, defective IGF-IR tyrosine phosphorylation, or improper tyrosine phosphorylation of IRS-1. Also, the acute (15-min) IGF-I activation of PI-3 and Akt kinases was similar in ER-negative and ER-positive cells. However, a chronic (2-day) IGF-I exposure induced the PI-3K/Akt pathway only in MCF-7 cells. The reactivation of this pathway in ER-negative cells by overexpression of constitutively active Akt mutants was not sufficient to significantly improve proliferation or survival (with or without IGF-I), which indicated that other pathways are also required to support these functions. Our results suggest that in breast cancer cells, IGF-IR can control nonmitogenic processes regardless of the ER status, whereas IGF-IR growth-related functions may depend on ER expression.
authors.affiliation: Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
authors.forename: M
authors.initials: M
authors.lastname: Bartucci
authors.forename: C
authors.initials: C
authors.lastname: Morelli
authors.forename: L
authors.initials: L
authors.lastname: Mauro
authors.forename: S
authors.initials: S
authors.lastname: Andò
authors.forename: E
authors.initials: E
authors.lastname: Surmacz
mesh_terms: D001943:Breast Neoplasms / Q000201:enzymology / Q000235:genetics / Q000473:pathology*; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D004789:Enzyme Activation; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D017526:Receptor, IGF Type 1 / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D011960:Receptors, Estrogen / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014162:Transfection; D014407:Tumor Cells, Cultured; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D007334:Insulin-Like Growth Factor I; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D017526:Receptor, IGF Type 1; D011960:Receptors, Estrogen; D048051:p38 Mitogen-Activated Protein Kinases; C494918:AKT1 protein, human