Regulation of vascular endothelial growth factor expression by insulin-like growth factor-I in endometrial adenocarcinoma cells.
Angiogenesis is crucial for tumor growth and dissemination. Vascular endothelial growth factor (VEGF) is a potent angiogenic factor that promotes endothelial cell proliferation and chemotaxis. VEGF occurs as 5 isoforms, as a result of an alternatively spliced transcript that originates from one gene, of which the 2 majors are the VEGF 121 and 165 isoforms. Our aim was firstly to determine the role of Insulin-like Growth Factor-I (IGF-I) in the regulation of VEGF expression in endometrial adenocarcinoma cells and then the mechanism by which this regulation occurs. IGF-I treatment of HEC-1A cells provoked an increase of VEGF mRNA expression that peaked at 48 hr with a 165 isoform mRNA more abundant than the 121 isoform. The IGF-I action was confirmed at the protein level, whose concentration was increased in the conditioned media. In experiments using transient transfection of VEGF promoter-luciferase constructs, the IGF-I failed to increase the activity of the VEGF promoter after a 24-hr period of IGF-I treatment, while the addition of Actinomycin D showed an increase of the VEGF mRNA half-life. Most interestingly, Northern blot analysis showed a different stability of the 2 major VEGF isoform mRNAs (VEGF 121 and 165), of which the 121 isoform was more stable than the 165 isoform. The IGF-I treatment prolonged the half-life of both of the VEGF isoform mRNAs. Our results suggest that IGF-I regulates VEGF expression in endometrial adenocarcinoma cells at the post-transcriptional level by enhancing the stabilization of the 2 major VEGF isoform mRNAs (VEGF(121) and VEGF(165)). In addition to its proliferative functions, IGF-I induces VEGF expression and participates in the maintenance of an angiogenic phenotype.
Bermont
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Service d'Oncologie et d'Endocrinologie Moléculaire (C.H.U. Besançon and IETG) and C.R.I 96.01, Besançon, France.
Lamielle
F
F
Fauconnet
S
S
Esumi
H
H
Weisz
A
A
Adessi
G L
GL
D000230:Adenocarcinoma / Q000235:genetics / Q000378:metabolism*; D017398:Alternative Splicing; D015152:Blotting, Northern; D003609:Dactinomycin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D016889:Endometrial Neoplasms / Q000235:genetics / Q000378:metabolism*; D016228:Endothelial Growth Factors / Q000096:biosynthesis*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D017930:Genes, Reporter / Q000235:genetics; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008222:Lymphokines / Q000096:biosynthesis*; D011401:Promoter Regions, Genetic / Q000235:genetics; D020033:Protein Isoforms / Q000096:biosynthesis; D020871:RNA Stability / Q000187:drug effects; D012333:RNA, Messenger / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014162:Transfection; D014407:Tumor Cells, Cultured; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D016228:Endothelial Growth Factors; D008222:Lymphokines; D020033:Protein Isoforms; D012333:RNA, Messenger; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D003609:Dactinomycin; D007334:Insulin-Like Growth Factor I