The roles of integrins and extracellular matrix proteins in the insulin-like growth factor I-stimulated chemotaxis of human breast cancer cells.

The effects of insulin-like growth factor I (IGF-I) on the migration of two human breast cancer cell lines, MCF-7 and MDA-231, were examined using a modified Boyden chamber. 10 ng/ml was the optimal IGF-I concentration for stimulation of migration. The majority of IGF-I-stimulated migration in both cell types was due to chemotaxis. MCF-7 cells failed to migrate on membranes coated with gelatin or fibronectin and migrated only in small numbers on laminin. In contrast, when vitronectin- or type IV collagen-coated membranes were used, the MCF-7 cells migrated in large numbers specifically in response to IGF-I but not to 10% fetal calf serum, epidermal growth factor, fibroblast growth factor, or platelet derived growth factor-BB. An IGF-I receptor-blocking antibody inhibited IGF-I-stimulated migration in both cell types. In addition, a blocking antibody to the alpha v beta 5 integrin (a vitronectin receptor) inhibited migration of MCF-7 cells in response to IGF-I through vitronectin but not through type IV collagen. Similarly, blocking antibodies specific for alpha 2 and beta 1 integrins significantly inhibited migration of both cell types through type IV collagen-coated membranes but not through vitronectin-coated membranes. We conclude that: 1) IGF-I stimulates migration of these two cell types through the IGF-I receptor; 2) interaction of vitronectin with the alpha v beta 5 integrin or collagen with the alpha 2 beta 1 integrin is necessary for the complete IGF-I response in MCF-7 cells, and 3) because migration represents an in vitro model for metastatic spread, integrins, extracellular matrix proteins, and IGF-I may play coordinated roles in the metastasis of breast cancer in vivo.

ACTH-secreting islet cell tumor: appearances on dynamic gadolinium-enhanced MRI.

Adrenocorticotropic hormone (ACTH) secreting islet cell tumors of the pancreas are extremely rare. A case of an ACTH producing islet cell tumor with multiple liver metastases is reported and the magnetic resonance imaging (MRI) findings are described.

Cell migration: interactions among integrins, IGFs and IGFBPs.

The migratory behaviour of cells is fundamental to diverse biologic processes such as tumor metastasis, development of atherosclerotic plaques, embryonic development and wound healing. We have examined the effects of IGF-I and IGFBPs on the migration of Chinese Hamster ovary (CHO) cells, smooth muscle cells (SMC) and human breast cancer cells (HBC) and have studied the involvement of integrin receptors in migration induced by IGF-I and by IGFBPs. Using a monolayer wounding assay, we determined the effect of IGFBP-1 on SMC to be qualitatively similar to its effect we reported earlier on CHO cells, in that there is a direct stimulation of migration mediated by the alpha 5 beta 1 integrin. IGFBP-2 has no direct effect on SMC migration, and although it also contains the Arg-Gly-Asp sequence, we can detect no integrin binding. Unlike CHO cells, SMC are stimulated to migrate by IGF-I. IGFBP-2 and IGFBP-1 both inhibit this IGF-I receptor-mediated stimulation. We have also studied the migration of HBC using a Boyden chamber apparatus and have shown a potent chemotactic effect of IGF-I. We have investigated the mechanisms for IGF-I stimulation of SMC and HBC migration. IGF-I stimulation of SMC migration requires the presence of either 0.2% serum or vitronectin, because of a requirement for ligand binding by the alpha V beta 3 integrin (vitronectin receptor). MCF-7 HBC migrate toward a concentration gradient of IGF-I, the only growth factor that was able to stimulate these cells to migrate. Integrin ligand binding was also necessary for MCF-7 cells to migrate in response to IGF-I; alpha V beta 5 integrin was required for migration on vitronectin and alpha 2 beta 1 was required on collagen. These studies demonstrate that the stimulation of cell migration by IGFBP-1 and IGF-I involves signaling by members of the integrin family of receptors. The mechanisms by which the IGF-I receptor and integrin receptors interact are not yet known.