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

Robert Wieder, Eyal Fenig, Huisheng Wang, Qin Wang, Shoshana Paglin, Thomas Menzel, Janice Gabrilove, Zvi Fuks, Joachim Yahalom

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

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/ΔA(FGF(18)) cells) and cells that express both the 18-kD along with the 22- and 24-kD nucleus-localizing 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 G0/G1 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 125I-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/ΔA(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/ΔA(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 n 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 G1 phase of the cell cycle, MCF-7/NCF(FGF(18,22,24)) cells retained active isoforms of cdk2 and the hyperphosphorylated form of Rb. These data suggest that high molecular weight forms of bFGF overexpressed in MCF-7 cells do not activate the receptor-mediated MAP kinase pathway, and do not induce p21(WAF1/CIP1) in an autocrine manner, but inhibit proliferation through other, possibly direct nuclear signalling mechanisms.

Original languageEnglish (US)
Pages (from-to)411-425
Number of pages15
JournalJournal of Cellular Physiology
Volume177
Issue number3
DOIs
StatePublished - Dec 1998

All Science Journal Classification (ASJC) codes

  • Physiology
  • Clinical Biochemistry
  • Cell Biology

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