Vascular endothelial growth factor, its receptor KDR/Flk-1, and pituitary tumor transforming gene in pituitary tumors.
Pituitary tumorigenesis is a poorly understood process involving dysregulation of the cell cycle, proliferation, and angiogenesis. The novel securin pituitary tumor transforming gene (PTTG) disrupts cell division and stimulates fibroblast growth factor (FGF)-2-mediated angiogenesis. We investigated expression of the angiogenic vascular endothelial growth factor (VEGF) and its receptor KDR/Flk-1 in 103 human pituitary tumors, and we assessed functional relationships between these genes in vitro. Nonfunctioning tumors (n = 81) demonstrated markedly raised VEGF mRNA (3.2-fold, P < 0.05) and protein concentrations, compared with normal pituitaries (n = 10). KDR was also highly induced in nonfunctioning tumors (14-fold, P < 0.001, n = 78) as well as in the whole cohort of pituitary tumors, compared with normal pituitary samples (14-fold, P < 0.0001, n = 100). In vitro, PTTG induced VEGF, but not KDR, expression in fetal neuronal NT2 cells (2.7-fold, P < 0.001, n = 8), MCF-7 breast carcinoma cells (1.9-fold, P = 0.03, n = 10), and choriocarcinoma JEG-3 cells (P = 0.0002, n = 8). A mutated PTTG construct that cannot be phosphorylated showed identical VEGF up-regulation (2.9-fold, P < 0.001, n = 8) in NT2 cells, compared with wild-type PTTG, but a further mutated construct with abrogation of the key protein:protein interaction domain of PTTG resulted in a significant reduction in VEGF stimulation, compared with wild-type (0.37-fold reduction, P < 0.001, n = 8). FGF-2 findings mirrored those of VEGF, although antibody depletion of secreted FGF-2 in the cell medium failed to influence VEGF up-regulation by PTTG. Overall, our findings implicate altered VEGF and KDR signaling in pituitary tumorigenesis, and we propose that PTTG stimulation of FGF-2 and VEGF expression in the presence of up-regulated growth factor receptors may account for angiogenic growth and progression of human pituitary tumors.
McCabe
C J
CJ
Division of Medical Sciences, University of Birmingham, Queen Elizabeth Hospital, Edgbaston, Birmingham, B15 2TH, United Kingdom. mccabcjz@bham.ac.uk
Boelaert
K
K
Tannahill
L A
LA
Heaney
A P
AP
Stratford
A L
AL
Khaira
J S
JS
Hussain
S
S
Sheppard
M C
MC
Franklyn
J A
JA
Gittoes
N J L
NJ
D000236:Adenoma / Q000098:blood supply / Q000235:genetics / Q000601:surgery; D019943:Amino Acid Substitution; D001483:Base Sequence; D017931:DNA Primers; D016228:Endothelial Growth Factors / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008222:Lymphokines / Q000235:genetics*; D016297:Mutagenesis, Site-Directed; D009363:Neoplasm Proteins / Q000235:genetics*; D009389:Neovascularization, Pathologic / Q000235:genetics; D010902:Pituitary Gland / Q000378:metabolism; D010911:Pituitary Neoplasms / Q000098:blood supply / Q000235:genetics* / Q000601:surgery; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics*; D017978:Receptors, Growth Factor / Q000235:genetics*; D040262:Receptors, Vascular Endothelial Growth Factor; D011994:Recombinant Proteins / Q000378:metabolism; D012044:Regression Analysis; D064249:Securin; D015534:Trans-Activators / Q000235:genetics; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D017931:DNA Primers; D016228:Endothelial Growth Factors; D008222:Lymphokines; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D017978:Receptors, Growth Factor; D011994:Recombinant Proteins; D064249:Securin; D015534:Trans-Activators; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; C578002:pituitary tumor-transforming protein 1, human; D020794:Receptor Protein-Tyrosine Kinases; D040262:Receptors, Vascular Endothelial Growth Factor