Increased expression of alpha6 integrin in endothelial cells unveils a proangiogenic role for basement membrane.
The integrin alpha6 subunit is part of the alpha6beta1 and alpha6beta4 integrin complexes, which are known to be receptors for laminins and to mediate several biological activities such as embryogenesis, organogenesis, and invasion of carcinoma cells. However, the precise role of alpha6 integrin in angiogenesis has not yet been addressed. We observed that both vascular endothelial growth factor-A and fibroblast growth factor-2 strongly upregulate alpha6 integrin in human endothelial cells. Moreover, alpha6 integrin was positively modulated in angiogenic vessels in pancreatic neuroendocrine carcinoma. In this transgenic mouse model of spontaneous tumorigenesis, alpha6 integrin expression increased in the angiogenic stage, while being expressed at low levels in normal and hyperplastic tissue. We studied the functional role of alpha6 integrin during angiogenesis by lentivirus-mediated gene silencing and blocking antibody. Cell migration and morphogenesis on basement membrane extracts, a laminin-rich matrix, was reduced in endothelial cells expressing low levels of alpha6 integrin. However, we did not observe any differences in collagen matrices. Similar results were obtained in the aortic ring angiogenesis assay. alpha6 integrin was required for vessel sprouting on basement membrane gels but not on collagen gels, as shown by stably silencing this integrin in the murine aorta. Finally, a neutralizing anti-alpha6 integrin antibody inhibited in vivo angiogenesis in chicken chorioallantoic membrane and transgenic tumor mouse model. In summary, we showed that the alpha6 integrin participated in vascular endothelial growth factor-A and fibroblast growth factor-2-driven angiogenesis in vitro and in vivo, suggesting that it might be an attractive target for therapeutic approaches in angiogenesis-dependent diseases such as tumor growth.
Primo
Luca
L
Department of Clinical and Biological Sciences and Oncological Sciences, University of Torino, and Institute for Cancer Research and Treatment, Candiolo, Turin, Italy. luca.primo@ircc.it
Seano
Giorgio
G
Roca
Cristina
C
Maione
Federica
F
Gagliardi
Paolo Armando
PA
Sessa
Roberto
R
Martinelli
Marianna
M
Giraudo
Enrico
E
di Blasio
Laura
L
Bussolino
Federico
F
D000818:Animals; D001485:Basement Membrane / Q000166:cytology / Q000378:metabolism*; D002465:Cell Movement / Q000502:physiology; D002642:Chick Embryo; D049033:Chorioallantoic Membrane / Q000098:blood supply; D015536:Down-Regulation; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism*; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism; D039503:Integrin alpha6 / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018919:Neovascularization, Physiologic / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D015854:Up-Regulation
D039503:Integrin alpha6; D012333:RNA, Messenger; D016222:Fibroblast Growth Factor 2