Scatter factor stimulates tumor growth and tumor angiogenesis in human breast cancers in the mammary fat pads of nude mice.
Scatter factor (SF) (also known as hepatocyte growth factor) is a plasminogen-related growth factor that induces tumor cell motility, invasion, and angiogenesis. Its receptor is a tyrosine kinase encoded by c-met, a protooncogene. Human breast cancer cells express SF and c-met in vivo; but human breast cancer cell lines do not produce SF in vitro. To determine whether SF can modulate the in vivo growth of human breast cancers within a natural mammary environment, we studied the orthotopic growth of SF-transfected (SF+) versus control (SF-) clones of MDAMB231 human mammary carcinoma cells in the mammary fat pads of athymic nude mice. SF+ clones expressed SF mRNA and produced very high titers of SF protein, whereas SF- clones did not express SF mRNA or produce detectable SF protein. Two SF+ clones (21 and 29) showed significantly increased tumor growth rates, reaching 3- to 4-fold larger primary tumor volumes and weights by time of killing (p < 0.001), as well as higher rates of axillary lymph node metastasis (p < 0.02), as compared with two SF- clones (32 and 34). In contrast, in vitro proliferation rates, two-dimensional colony formation, and soft agar colony formation were no greater in SF+ than in SF- clones. We performed further studies to investigate the discrepancy between the in vivo and in vitro growth results. Tumor extracts from SF+ clone (21 + 29) tumors had 50-fold higher SF content than did SF- clone (32 + 34) tumors, confirming high-level SF expression in vivo in SF+ tumors. Immunostaining of tumor sections for proliferating cell nuclear antigen revealed only a modest increase in the proportion of cycling cells in SF+ versus SF- tumors (70% versus 60%, respectively). The terminal deoxytransferase-labeling index was equally low (approximately 1%) in SF+ and SF- tumors, suggesting that apoptosis was not responsible for the slower growth of SF- tumors. However, SF+ tumors had significantly higher tumor microvessel densities than SF- tumors (p < 0.001). Moreover, there were much higher titers of chemotactic activity for microvascular endothelial cells in cell-conditioned media and primary tumor extracts from SF+ clones as compared with SF- clones. As demonstrated using the rat cornea assay, there was more angiogenic activity in SF+ tumor extracts than in SF- extracts. The increased chemotactic and angiogenic activities in SF+ tumor extracts were not explained by secondary alterations in the content of the angiogenic mediator, vascular endothelial growth factor, or the antiangiogenic glycoprotein, thrombospondin-1; and those activities were neutralized using an anti-SF monoclonal antibody. These findings suggest that SF promotes the orthotopic growth of human breast cancers, at least in part, by stimulating tumor angiogenesis.
Lamszus
K
K
Department of Radiation Oncology, Long Island Jewish Medical Center, New Hyde Park, New York 11040, USA.
Jin
L
L
Fuchs
A
A
Shi
E
E
Chowdhury
S
S
Yao
Y
Y
Polverini
P J
PJ
Laterra
J
J
Goldberg
I D
ID
Rosen
E M
EM
D000273:Adipose Tissue / Q000098:blood supply* / Q000473:pathology; D000818:Animals; D015415:Biomarkers; D001943:Breast Neoplasms / Q000098:blood supply* / Q000473:pathology*; D002455:Cell Division; D002999:Clone Cells; D003315:Cornea / Q000098:blood supply; D005260:Female; D017228:Hepatocyte Growth Factor / Q000096:biosynthesis / Q000494:pharmacology / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D008175:Lung Neoplasms / Q000473:pathology / Q000556:secondary; D008207:Lymphatic Metastasis; D051379:Mice; D008819:Mice, Nude; D008833:Microcirculation / Q000473:pathology*; D009389:Neovascularization, Pathologic; D018809:Proliferating Cell Nuclear Antigen / Q000032:analysis; D019859:Proto-Oncogene Proteins c-met; D051381:Rats; D020794:Receptor Protein-Tyrosine Kinases / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000096:biosynthesis; D014158:Transcription, Genetic; D014162:Transfection; D014183:Transplantation, Heterologous; D014568:Urokinase-Type Plasminogen Activator / Q000096:biosynthesis
D015415:Biomarkers; D018809:Proliferating Cell Nuclear Antigen; D011994:Recombinant Proteins; D017228:Hepatocyte Growth Factor; D019859:Proto-Oncogene Proteins c-met; D020794:Receptor Protein-Tyrosine Kinases; D014568:Urokinase-Type Plasminogen Activator