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Basic fibroblast growth factor confers growth inhibition and mitogen-activated protein kinase activation in human
1Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
Abstract:
The effect of basic fibroblast growth factor (bFGF) on human breast cancer cells was studied in vitro. Exposure to bFGF resulted in significant growth inhibition, decreased DNA synthesis, and accumulation of cells in G0-G1. The IC50 for growth inhibition in MCF-7 cells was 50 pg/ml, and it was abrogated by neutralizing antibodies against bFGF. Inhibition of growth by bFGF was predominant over the growth stimulatory effects of 17beta-estradiol, insulin, or epidermal growth factor. Binding and cross-linking studies of 125I-labeled bFGF in intact MCF-7 cells demonstrated 5.2 x 10(3) saturable bFGF binding sites per cell, a dissociation constant of 57 pm, and a Mr 142,000 (125)I-labeled bFGF cross-linked protein. Stimulation of MCF-7 cells with bFGF at concentrations which effected growth inhibition also resulted in activation of p42(mapk) (ERK2) and p44(mapk) (ERK1) mitogen-activated protein kinases. These data demonstrate that whereas bFGF inhibits the growth of several breast cancer cell lines, it concomitantly activates ERK1 and ERK2, generally considered to signal mitogenic rather than growth inhibitory responses. Whether there is association between these phenomena remains unknown.
Insights
Basic fibroblast growth factor (bFGF) inhibits human breast cancer cell growth and DNA synthesis. Paradoxically, bFGF also activates ERK1 and ERK2, signaling pathways typically associated with cell growth.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- Basic fibroblast growth factor (bFGF) is a signaling protein involved in various cellular processes.
- The role of bFGF in human breast cancer, particularly its impact on cell proliferation and signaling pathways, requires further elucidation.
Purpose of the Study:
- To investigate the in vitro effects of bFGF on human breast cancer cell growth and DNA synthesis.
- To characterize bFGF binding sites and signaling events in MCF-7 breast cancer cells.
- To explore the relationship between bFGF-induced growth inhibition and mitogen-activated protein kinase (MAPK) activation.
Main Methods:
- Cell culture of human breast cancer cell lines, including MCF-7.
- Treatment with bFGF and assessment of cell growth, DNA synthesis, and cell cycle distribution.
- Use of neutralizing antibodies to confirm bFGF specificity.
- Radioligand binding and cross-linking studies to identify bFGF receptors.
- Western blot analysis to detect MAPK activation (ERK1/ERK2).
Main Results:
- bFGF significantly inhibited the growth and DNA synthesis of human breast cancer cells, causing cell cycle arrest in G0-G1.
- The IC50 for bFGF-induced growth inhibition in MCF-7 cells was 50 pg/ml, and this effect was blocked by specific antibodies.
- bFGF demonstrated growth inhibitory effects that predominated over growth-promoting signals from 17beta-estradiol, insulin, and EGF.
- MCF-7 cells possess approximately 5.2 x 10^3 high-affinity bFGF binding sites per cell (Kd = 57 pM).
- bFGF treatment led to the activation of p42(mapk) (ERK2) and p44(mapk) (ERK1) in MCF-7 cells, despite causing growth inhibition.
Conclusions:
- Basic fibroblast growth factor exhibits potent in vitro growth-inhibitory effects on human breast cancer cells.
- bFGF signaling in breast cancer cells involves high-affinity receptor binding and activation of the ERK1/ERK2 MAPK pathway.
- The concurrent observation of growth inhibition and MAPK activation by bFGF presents a paradox that warrants further investigation into the underlying mechanisms.