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 M(r) 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 M(r) 18,000 cytoplasmic FGF-2 moiety had a 45% decrease in invasion in Matrigel compared to vector-transfected controls. Cells expressing M(r) 18,000 FGF-2 had an increase in M(r) 97,000 and M(r) 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 M(r) 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.
|Original language||English (US)|
|Number of pages||8|
|State||Published - Feb 1 2000|
ASJC Scopus subject areas
- Cancer Research