VEGF165b, an inhibitory vascular endothelial growth factor splice variant: mechanism of action, in vivo effect on angiogenesis and endogenous protein expression.
Growth of new blood vessels (angiogenesis), required for all tumor growth, is stimulated by the expression of vascular endothelial growth factor (VEGF). VEGF is up-regulated in all known solid tumors but also in atherosclerosis, diabetic retinopathy, arthritis, and many other conditions. Conventional VEGF isoforms have been universally described as proangiogenic cytokines. Here, we show that an endogenous splice variant, VEGF(165)b, is expressed as protein in normal cells and tissues and is circulating in human plasma. We also present evidence for a sister family of presumably inhibitory splice variants. Moreover, these isoforms are down-regulated in prostate cancer. We also show that VEGF(165)b binds VEGF receptor 2 with the same affinity as VEGF(165) but does not activate it or stimulate downstream signaling pathways. Moreover, it prevents VEGF(165)-mediated VEGF receptor 2 phosphorylation and signaling in cultured cells. Furthermore, we show, with two different in vivo angiogenesis models, that VEGF(165)b is not angiogenic and that it inhibits VEGF(165)-mediated angiogenesis in rabbit cornea and rat mesentery. Finally, we show that VEGF(165)b expressing tumors grow significantly more slowly than VEGF(165)-expressing tumors, indicating that a switch in splicing from VEGF(165) to VEGF(165)b can inhibit tumor growth. These results suggest that regulation of VEGF splicing may be a critical switch from an antiangiogenic to a proangiogenic phenotype.
Woolard
Jeanette
J
Microvascular Research Laboratories, Department of Physiology, Preclinical Veterinary School, University of Bristol, Southwell Street, Bristol, United Kingdom.
Wang
Wen-Ying
WY
Bevan
Heather S
HS
Qiu
Yan
Y
Morbidelli
Lucia
L
Pritchard-Jones
Rowan O
RO
Cui
Tai-Gen
TG
Sugiono
Marto
M
Waine
Elizabeth
E
Perrin
Rachel
R
Foster
Rebecca
R
Digby-Bell
Jonathon
J
Shields
Jacqueline D
JD
Whittles
Cheryl E
CE
Mushens
Rosey E
RE
Gillatt
David A
DA
Ziche
Marina
M
Harper
Steven J
SJ
Bates
David O
DO
D000818:Animals; D016466:CHO Cells; D045744:Cell Line, Tumor; D006224:Cricetinae; D006801:Humans; D008297:Male; D009389:Neovascularization, Pathologic / Q000209:etiology*; D011471:Prostatic Neoplasms / Q000378:metabolism; D012326:RNA Splicing; D011817:Rabbits; D051381:Rats; D015398:Signal Transduction; D042461:Vascular Endothelial Growth Factor A / Q000037:antagonists & inhibitors* / Q000235:genetics*
C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A