Basic fibroblast growth factor confers a less malignant phenotype in MDA-MB-231 human breast cancer cells.
Basic fibroblast growth factor (FGF-2) expression is associated with a more differentiated phenotype, earlier stage of disease, and a better prognosis in breast cancer patients. To determine whether expression of FGF-2 can cause a less malignant phenotype, we engineered MDA-MB-231 cells, a highly dedifferentiated, invasive breast cancer cell line, to express different isoforms of FGF-2. Cells expressed either cytoplasmic, nuclear, or a combination of both FGF-2 isoforms. Western blots of 2 M NaCl washes and of conditioned medium demonstrated that these cells did not export FGF-2. Cells expressing FGF-2 had levels of fibroblast growth factor receptors equivalent with those of control cells. Transformation was assayed by anchorage-independent colony formation and tumor formation in athymic mice. All of the constructs expressing various FGF-2 isoforms had a 60-70% reduction in colony formation in soft agar, but only cells expressing the Mr 18,000 FGF-2 isoform formed fewer and smaller tumors in mice. To determine potential mechanisms responsible for a less malignant phenotype, experiments measuring invasion in Matrigel, the secretion of matrix metalloprotease activity and migration in a modified Boyden chamber and in a patch wound motility assay were carried out. Cells expressing the Mr 18,000 cytoplasmic FGF-2 moiety had a 45% decrease in invasion in Matrigel compared to vector-transfected controls. Cells expressing Mr 18,000 FGF-2 had an increase in Mr 97,000 and Mr 48,000 collagenase, demonstrating that the decreased invasive potential was not due to a down-regulation of gelatinolytic or caseinolytic matrix metalloproteinases. However, motility was decreased in both assays, primarily in cells expressing Mr 18,000 FGF-2, whereas exogenous recombinant human FGF-2 had no effect. These studies demonstrate for the first time that FGF-2 expression can cause a less malignant phenotype in breast cancer cells, possibly as a result of decreased motility and invasion.
Korah
R M
RM
Division of Medical Oncology, University of Medicine and Dentistry of New Jersey-New Jersey Medical School, Newark 07103, USA.
Sysounthone
V
V
Golowa
Y
Y
Wieder
R
R
D000818:Animals; D001943:Breast Neoplasms / Q000473:pathology*; D002455:Cell Division; D005260:Female; D006801:Humans; D020782:Matrix Metalloproteinases / Q000096:biosynthesis; D051379:Mice; D008807:Mice, Inbred BALB C; D008970:Molecular Weight; D009361:Neoplasm Invasiveness; D010641:Phenotype; D017468:Receptors, Fibroblast Growth Factor / Q000502:physiology; D014162:Transfection
D017468:Receptors, Fibroblast Growth Factor; D020782:Matrix Metalloproteinases