Osteopontin-induced migration of human mammary epithelial cells involves activation of EGF receptor and multiple signal transduction pathways.
Osteopontin (OPN) is a secreted, integrin-binding glycophosphoprotein that has been implicated in breast cancer. We previously showed that OPN-induced cell migration of mammary epithelial cells (MEC) depends on binding to cell surface integrins and involves activation of the hepatocyte growth factor (HGF) receptor, Met. Here, we show that OPN-induced migration of MEC also requires activation of the epidermal growth factor (EGF) pathway. Synergism was seen between EGF and OPN in inducing cell migration. Furthermore, incubation of cells with exogenous OPN increased ligand (TGFalpha> EGF) and EGF receptor (EGFR) mRNA expression, as well as EGFR kinase activity. Treatment of cells with anti-TGFalpha or anti-EGFR antibody, or with tyrphostin-25 (EGFR inhibitor), significantly impaired the cell migration response to OPN. Other more broad-spectrum tyrosine kinase inhibitors and the growth factor/ receptor interaction inhibitor, suramin, also inhibited OPN-induced migration. Using specific signal transduction pathway inhibitors, we have screened for involvement of MEK (MAP kinase kinase), phosphatidylinositol 3-kinase, phospholipase C (PLC), and protein kinase C (PKC). Results implicated all of these pathways in OPN-induced cell migration, the most pronounced effect being seen with PLC and PKC inhibitors. These results suggest that induction of MEC migration by OPN involves a cascade of events including at least two growth factor/receptor pathways and multiple downstream signal transduction pathways. A number of potential targets are thus provided for strategies aimed at blocking the malignancy-promoting effects of OPN.
Tuck
Alan B
AB
Department of Pathology, London Health Sciences Centre, University of Western Ontario, London, Ontario, Canada. atuck@uwo.ca
Hota
Charulata
C
Wilson
Sylvia M
SM
Chambers
Ann F
AF
D000230:Adenocarcinoma / Q000473:pathology; D001940:Breast / Q000166:cytology*; D001943:Breast Neoplasms / Q000473:pathology; D002465:Cell Movement / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects; D066246:ErbB Receptors / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects* / Q000502:physiology; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000502:physiology; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D053495:Osteopontin; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology; D019859:Proto-Oncogene Proteins c-met / Q000187:drug effects / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000502:physiology; D011994:Recombinant Proteins / Q000494:pharmacology; D012795:Sialoglycoproteins / Q000494:pharmacology* / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D016211:Transforming Growth Factor alpha / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000187:drug effects; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000502:physiology
D004791:Enzyme Inhibitors; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D009363:Neoplasm Proteins; D016376:Oligonucleotides, Antisense; D053495:Osteopontin; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C; D019859:Proto-Oncogene Proteins c-met; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D012795:Sialoglycoproteins; D016211:Transforming Growth Factor alpha; D010738:Type C Phospholipases; C506895:SPP1 protein, human