Basic fibroblast growth factor-mediated overexpression of vascular endothelial growth factor in 1F6 human melanoma cells is regulated by activation of PI-3K and p38 MAPK.
BACKGROUND
1F6 human melanoma xenografts overexpressing either the 18 kD (18kD) form or all (ALL) forms of human basic fibroblast growth factor (bFGF) demonstrate an abundant number of microvessels and accelerated growth. We now examined whether bFGF mediates vascular endothelial growth factor (VEGF) expression.


METHODS
Quantitative RT-PCR was used to determine bFGF and VEGF mRNA, VEGF protein secretion was measured by ELISA and VEGF promoter activation was assessed by a dual luciferase activity assay. Western blot was carried out to detect phosphorylation of bFGF-regulated target proteins.


RESULTS
In 1F6-18kD and 1F6-ALL clones VEGF mRNA was increased 4- to 5-fold and VEGF protein secretion was highly stimulated due to activation of the VEGF promotor. PI-3K, p38 MAPK and ERK1/2 MAPK pathways were activated, while inhibition of PI-3K or p38 resulted in, respectively, 55% and up to 70% reduction of VEGF mRNA overexpression. A concurrent 60% decrease in VEGF protein secretion was mostly apparent upon inhibition of PI-3K. Inhibition of ERK1/2 hardly affected VEGF mRNA or protein secretion. Two unselected human melanoma cell lines with high metastatic potential contained high bFGF and VEGF, while three non- or sporadically metastatic cell lines displayed low bFGF and VEGF.


CONCLUSIONS
These data indicate that stimulation of VEGF protein secretion in response to bFGF overexpression may contribute to increased vascularization and enhanced aggressiveness in melanoma.
Fontijn
Dennis
D
Department of Medical Oncology, VU University Medical Center, Amsterdam, The Netherlands.
Bosch
Linda J W
LJ
Duyndam
Monique C A
MC
van Berkel
Maria P A
MP
Janmaat
Maarten L
ML
Boven
Epie
E
D045744:Cell Line, Tumor; D004789:Enzyme Activation; D016222:Fibroblast Growth Factor 2 / Q000235:genetics / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008545:Melanoma / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics* / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*
D042461:Vascular Endothelial Growth Factor A; D016222:Fibroblast Growth Factor 2; D019869:Phosphatidylinositol 3-Kinases; D048051:p38 Mitogen-Activated Protein Kinases