Basic FGF augments hypoxia induced HIF-1-alpha expression and VEGF release in T47D breast cancer cells.
OBJECTIVE
Both hypoxia inducible factor 1 (HIF-1) and basic fibroblast growth factor (bFGF) play important roles in tumour angiogenesis. This study was designed to clarify the cooperative effect of these two mediators in induction of vascular endothelial cell growth factor (VEGF) release from breast cancer and probe possible mechanisms involved.


METHODS
Release of VEGF from a breast cancer cell line (T47D) was quantitated by enzyme linked immunosorbent assay (ELISA). Expression of HIF-1 and ERK was assayed using Western blotting. Transient transfection and dual luciferase reporter assay were used to study HIF-1 transactivity.


RESULTS
The data showed that hypoxia induced the expression of HIF-1alpha protein, the transactivity of HIF-1 and the release of VEGF. bFGF further augmented these hypoxic inductions. The PI3K pathway was required for these processes as demonstrated by application of PI3Kinase inhibitor (LY294002) or mutant construct transfections. In contrast, the MEK1 inhibitor PD98059 showed no effect on either activation of HIF-1 or VEGF release, which is in agreement with our finding that ERK1/2 was not activated by hypoxia. Under hypoxic conditions, bFGF activated the MEK1/ERK pathway. PD98059 blocked the activation of ERK1/2 and suppressed bFGF-induced HIF-1 transactivity, yet the protein expression of HIF-1alpha or VEGF release was not affected by PD98059.


CONCLUSIONS
bFGF augments hypoxia induced VEGF release mainly through the PI3K pathway and partly depending on HIF-1 activity. Elucidation of this mechanism may provide a new target for anti-angiogenesis in cancer therapy.
Department of Pathology, Inner Mongolia Medical College, Huhhot, China.
Yong-Hong
YH
Shi
Lynne
L
Bingle
Li-Hua
LH
Gong
Yu-Xiang
YX
Wang
Kevin P
KP
Corke
Wei-Gang
WG
Fang
D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology; D015687:Cell Hypoxia / Q000502:physiology*; D045744:Cell Line, Tumor; D002867:Chromones / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D005260:Female; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism*; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors / Q000502:physiology; D009025:Morpholines / Q000494:pharmacology; D009389:Neovascularization, Pathologic / Q000503:physiopathology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D015398:Signal Transduction / Q000502:physiology; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*
D002867:Chromones; D004791:Enzyme Inhibitors; D048049:Extracellular Signal-Regulated MAP Kinases; D016222:Fibroblast Growth Factor 2; D005419:Flavonoids; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D048369:MAP Kinase Kinase 1; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D042461:Vascular Endothelial Growth Factor A; C497442:HIF1A protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C482125:MAP2K1 protein, human; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one