Osteopontin induces increased invasiveness and plasminogen activator expression of human mammary epithelial cells.
Osteopontin (OPN) has been associated with enhanced malignancy in breast cancer, but its functional role in this disease is poorly understood. To study the effect of OPN on cellular invasiveness, basal OPN expression was first assessed in members of a progression series of human mammary epithelial cell lines (21PT: immortalized, non-tumorigenic; 21NT: weakly tumorigenic; 21MT-1: tumorigenic, weakly metastatic; MDA-MB-435 cells: tumorigenic, highly metastatic). The two lines which expressed lowest basal levels of OPN (21PT, 21NT) were then examined for up-regulation of invasive behavior in response to exogenous or transfected (endogenous) OPN. Both 21PT and 21NT showed increased invasiveness through Matrigel when human recombinant (hr)OPN was added to the lower chamber of transwells. Both also showed a cell migration response to hrOPN. Populations of 21PT and 21NT cells stably transfected with an OPN-expression vector showed higher levels of cell invasiness than control vector transfectants. Examination of transfectants for mRNA of a number of secreted proteases showed that only urokinase-type plasminogen activator (uPA) expression was closely associated with OPN expression and cellular invasiveness. Treatment of the parental 21PT and 21NT cells with exogenous hrOPN resulted in increased uPA mRNA expression and increased urokinase activity of the conditioned media. Both increased cell migration and induction of uPA expression are thus potential mechanisms of increased invasiness of breast epithelial cells in response to OPN.
Tuck
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Department of Pathology, London Health Sciences Centre, University of Western Ontario, Canada.
Arsenault
D M
DM
O'Malley
F P
FP
Hota
C
C
Ling
M C
MC
Wilson
S M
SM
Chambers
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AF
D001940:Breast / Q000166:cytology*; D001943:Breast Neoplasms / Q000473:pathology*; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D003094:Collagen; D017077:Culture Media, Conditioned; D018450:Disease Progression; D004338:Drug Combinations; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D005109:Extracellular Matrix; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D007797:Laminin; D009361:Neoplasm Invasiveness / Q000503:physiopathology*; D009362:Neoplasm Metastasis / Q000503:physiopathology*; D009363:Neoplasm Proteins / Q000378:metabolism*; D053495:Osteopontin; D011509:Proteoglycans; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D012334:RNA, Neoplasm / Q000096:biosynthesis / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000494:pharmacology / Q000502:physiology; D012795:Sialoglycoproteins / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D014162:Transfection; D014407:Tumor Cells, Cultured; D014568:Urokinase-Type Plasminogen Activator / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*
D017077:Culture Media, Conditioned; D004338:Drug Combinations; D007797:Laminin; D009363:Neoplasm Proteins; D011509:Proteoglycans; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D011993:Recombinant Fusion Proteins; C506895:SPP1 protein, human; D012795:Sialoglycoproteins; D053495:Osteopontin; C059485:matrigel; D003094:Collagen; D014568:Urokinase-Type Plasminogen Activator