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In vitro study of HIF‐1 activation and VEGF release by bFGF in the T47D breast cancer cell line under normoxic conditions: involvement of PI‐3K/Akt and MEK1/ERK pathways
Author(s) -
Shi Yonghong,
Wang Yuxiang,
Bingle Lynne,
Gong Lihua,
Heng Wanjie,
Li Yan,
Fang Weigang
Publication year - 2005
Publication title -
the journal of pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.964
H-Index - 184
eISSN - 1096-9896
pISSN - 0022-3417
DOI - 10.1002/path.1734
Subject(s) - mapk/erk pathway , protein kinase b , cancer research , in vitro , pi3k/akt/mtor pathway , cancer , vegf receptors , cell culture , breast cancer , chemistry , medicine , phosphorylation , microbiology and biotechnology , biology , signal transduction , biochemistry , genetics
Hypoxia‐inducible factor (HIF) is critical in the modulation of tumour angiogenesis in response to hypoxia. In the present study, the mechanisms underlying basic fibroblast growth factor (bFGF)‐induced activation of HIF‐1 and the subsequent release of vascular endothelial growth factor (VEGF) in a human breast cancer cell line (T47D) under normoxic conditions were explored. The data show that HIF‐1α expression is induced by bFGF in a dose‐ and time‐dependent fashion, while increased HIF‐1α protein expression and transactivity of HIF‐1 are due to the phosphorylation of Akt by bFGF, as indicated by application of the phosphatidylinositol 3‐kinase (PI‐3K) inhibitor LY294002. The data also show that the MEK1 (mitogen‐activated protein kinase kinase‐1)/ERK (extracellular signal‐regulated kinase) pathway is only involved in bFGF‐induced transactivity of HIF‐1, but not HIF‐1α expression, indicating roles for both the PI‐3K/Akt and the MEK1/ERK pathways in bFGF activity. In addition, the translation inhibitor cycloheximide confirmed that bFGF‐induced HIF‐1α protein expression was due to de novo protein synthesis. In contrast, p38 was not required for the expression of HIF‐1α or HIF‐1 transactivity, although significant phosphorylation of p38 was observed after bFGF treatment. Treatment of the cells with bFGF increased the amount of VEGF release, and this could be suppressed by either PD98059 or LY294002, suggesting the presence of a HIF‐1α‐dependent pathway for bFGF‐induced VEGF production. In conclusion, the PI‐3K/Akt and MEK1/ERK pathways, in a potentially independent and co‐operative fashion, can modulate HIF‐1 activation by bFGF. Further studies will pinpoint whether HIF‐1 is the transcriptional factor responsible for the increased VEGF production following bFGF treatment of breast tumour cells. Copyright © 2005 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.