Fibronectin Fibrils and Growth Factors Stimulate Anchorage-Independent Growth of a Murine Mammary Carcinoma
Stromal cells are important regulators of mammary carcinoma growth and metastasis. We have previously shown that a 3T3-L1 adipocyte cell line secretes hepatocyte growth factor (HGF), which stimulates proliferation of a murine mammary carcinoma (SP1) in monolayer cultures (DNA Cell Biol.13, 1189–1897...
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Published in | Experimental cell research Vol. 222; no. 2; pp. 360 - 369 |
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Main Authors | , , , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
Elsevier Inc
01.02.1996
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Subjects | |
Online Access | Get full text |
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Summary: | Stromal cells are important regulators of mammary carcinoma growth and metastasis. We have previously shown that a 3T3-L1 adipocyte cell line secretes hepatocyte growth factor (HGF), which stimulates proliferation of a murine mammary carcinoma (SP1) in monolayer cultures (DNA Cell Biol.13, 1189–1897, 1994). We now examine the role of growth factors and the extracellular matrix protein fibronectin in stimulation of anchorage-independent growth of SP1 cells. Purified transforming growth factor-β (TGF-β) stimulated significant colony growth in soft agar cultures, whereas HGF had a lesser effect. Analysis by confocal microscopy revealed that carcinoma cell colonies contained extracellular microfibrils composed of fibronectin. Partial depletion of fibronectin from 7% FBS/agar cultures reduced the number of colonies; colony growth could be recovered by adding back exogenous fibronectin. Addition of the 70-kDa N-terminal fragment of fibronectin, which inhibits fibronectin fibril formation, reduced growth of SP1 cell colonies, but an 85-kDa fragment containing the cell binding domain did not inhibit colony growth. These findings indicate that deposition of extracellular fibronectin fibrils is necessary, but not sufficient, for anchorage-independent growth of SP1 mammary carcinoma cells; growth factors are also required. SP1 cells had less fibronectin mRNA and secreted less fibronectin protein under anchorage-independent conditions than under anchorage-dependent conditions, as determined by Northern blotting and immunoprecipitation analysis. Thus, both growth factors (HGF and TGF-β) and fibronectin may be important regulators of paracrine stimulation by stromal cells of anchorage-independent growth of mammary carcinoma cells. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0014-4827 1090-2422 |
DOI: | 10.1006/excr.1996.0045 |