VEGF165b, an inhibitory splice variant of vascular endothelial growth factor, is down-regulated in renal cell carcinoma.
Angiogenesis is essential for tumor growth. Vascular endothelial growth factor (VEGF) is the most potent growth factor of tumor neovasculature, has been shown to be up-regulated in every tumor studied thus far, and is correlated with tumor stage and progression. To determine whether specific VEGF splice variants were differentially expressed in renal cell carcinomas, 18 polar tumor samples were analyzed by reverse transcription-PCR using primers designed to differentiate between VEGF splice variants. Control tissue was derived from the opposite normal pole. An amplicon of length consistent with the previously described variant VEGF(148) was found in normal kidney tissue. Subsequent sequencing revealed a new VEGF isoform formed by differential splicing from the end of exon 7 into the 3' untranslated region of the mRNA. Cloning of this transcript showed that translation would result in a 165-amino acid peptide with an alternative terminal 6 amino acids, followed by a stop codon. We have termed this new isoform VEGF165b. This isoform was present in 17 of 18 normal kidney samples but only 4 of 18 cases from matched malignant tissue. VEGF165b was therefore expressed in a significantly higher proportion of normal tissue than malignant tissue from the same patients (P < 0.001). To determine the functional significance of this new isoform, we expressed the full-length protein in a heterologous expression system. Conditioned medium containing this isoform significantly and dose dependently inhibited VEGF165-mediated proliferation, migration of endothelial cells, and vasodilatation of mesenteric arteries. This novel isoform VEGF165b is therefore an endogenous inhibitory form of VEGF that is down-regulated in renal tumors and, therefore, may be anti-angiogenesis.
Microvascular Research Laboratories, Department of Physiology, Preclinical Veterinary School, University of Bristol, Bristol BS2 8EJ, United Kingdom.
David O
DO
Bates
Tai-Gen
TG
Cui
Joanne M
JM
Doughty
Matthias
M
Winkler
Marto
M
Sugiono
Jacqueline D
JD
Shields
Danielle
D
Peat
David
D
Gillatt
Steven J
SJ
Harper
D000368:Aged; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D001483:Base Sequence; D002292:Carcinoma, Renal Cell / Q000098:blood supply / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division / Q000502:physiology; D002465:Cell Movement / Q000502:physiology; D015536:Down-Regulation; D016228:Endothelial Growth Factors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D004730:Endothelium, Vascular / Q000166:cytology; D005091:Exons; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007680:Kidney Neoplasms / Q000098:blood supply / Q000235:genetics / Q000378:metabolism*; D008222:Lymphokines / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D008875:Middle Aged; D008969:Molecular Sequence Data; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D014664:Vasodilation / Q000502:physiology
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