Overexpression of basic fibroblast growth factor in MCF-7 human breast cancer cells: Lack of correlation between inhibition of cell growth and MAP kinase activation
✍ Scribed by Robert Wieder; Eyal Fenig; Huisheng Wang; Qin Wang; Shoshana Paglin; Thomas Menzel; Janice Gabrilove; Zvi Fuks; Joachim Yahalom
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 606 KB
- Volume
- 177
- Category
- Article
- ISSN
- 0021-9541
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✦ Synopsis
Basic fibroblast growth factor (bFGF, FGF-2) is progressively lost from mammary epithelial cells as they become malignant. To investigate the effects of restoring the expression of bFGF in breast cancer cells, we constructed MCF-7 cells that permanently overexpress 18-kD cytoplasm-localizing bFGF (MCF-7/DA FGF(18) cells) and cells that express both the 18-kD along with the 22-and 24-kD nucleuslocalizing bFGF peptides (MCF-7/NCF FGF(18,22,24) cells), using retroviral transduction. These stable cell constructs grew more slowly and had a larger fraction of their populations in the G 0 /G 1 phase of the cell cycle than control cells. All forms of bFGF were eluted from MCF-7/NCF FGF(18,22,24) cell monolayers with 2 M NaCl, in contrast to fibroblasts that were demonstrated to secrete only the 18-kD bFGF isoform. High-affinity binding of 18-kD 125 I-bFGF to these cells was significantly decreased, probably because of competitive binding by the autocrine-secreted bFGF. Recombinant 18-kD bFGF that was previously demonstrated in our laboratory to inhibit proliferation, activate MAP kinase, and induce the cyclin-dependent kinase inhibitor p21 WAF1/CIP1 in MCF-7 cells, further inhibited MCF-7/DA FGF(18) cells but had no effect on MCF-7/NCF FGF (18,22,24) cells. The total cellular content of the high-affinity FGF receptors 1-3 was unchanged, but FGF receptor 4 was decreased in MCF-7/NCF FGF(18,22,24) cells. Both cell types overexpressing bFGF isoforms had elevated levels of the cyclin-dependent kinase inhibitor p27 Kip1 but not that of p21 WAF1/CIP1 . In MCF-7/DA FGF(18) cells, FGFR1 and MAP kinase were constitutively phosphorylated. Exogenous recombinant 18-kD bFGF did not accentuate these effects but did induce an increase in the levels of p21 WAF1/CIP1 corresponding to the further inhibition induced by exogenous bFGF in these cells. In MCF-7/NCF FGF(18,22,24) cells, FGFR1 and MAP kinase were not phosphorylated at baseline nor upon stimulation with recombinant bFGF, and exogenous bFGF only had a minimal effect on low steady-state p21 WAF1/CIP1 levels. However, stimulation of these cells with phorbol ester or insulin did result in MAP kinase phosphorylation. While growth-inhibited in the G 1 phase of the cell cycle, MCF-7/