Bcl-2 acts in a proangiogenic signaling pathway through nuclear factor-kappaB and CXC chemokines.
Vascular endothelial growth factor (VEGF) induces expression of Bcl-2 in tumor-associated microvascular endothelial cells. We have previously reported that up-regulated Bcl-2 expression in microvascular endothelial cells is sufficient to enhance intratumoral angiogenesis and to accelerate tumor growth. We initially attributed these results to Bcl-2-mediated endothelial cell survival. However, in recent experiments, we observed that conditioned medium from Bcl-2-transduced human dermal microvascular endothelial cells (HDMEC-Bcl-2) is sufficient to induce potent neovascularization in the rat corneal assay, whereas conditioned medium from empty vector controls (HDMEC-LXSN) does not induce angiogenesis. These results cannot be attributed to the role of Bcl-2 in cell survival. To understand this unexpected observation, we did gene expression arrays that revealed that the expression of the proangiogenic chemokines interleukin-8 (CXCL8) and growth-related oncogene-alpha (CXCL1) is significantly higher in HDMEC exposed to VEGF and in HDMEC-Bcl-2 than in controls. Inhibition of Bcl-2 expression with small interfering RNA-Bcl-2, or the inhibition of Bcl-2 function with small molecule inhibitor BL-193, down-regulated CXCL8 and CXCL1 expression and caused marked decrease in the angiogenic potential of endothelial cells without affecting cell viability. Nuclear factor-kappaB (NF-kappaB) is highly activated in HDMEC exposed to VEGF and HDMEC-Bcl-2 cells, and genetic and chemical approaches to block the activity of NF-kappaB down-regulated CXCL8 and CXCL1 expression levels. These results reveal a novel function for Bcl-2 as a proangiogenic signaling molecule and suggest a role for this pathway in tumor angiogenesis.
Karl
Elisabeta
E
Angiogenesis Research Laboratory, Department of Restorative Sciences, School of Dentistry, University of Michigan, Ann Arbor 48109-1078, USA.
Warner
Kristy
K
Zeitlin
Benjamin
B
Kaneko
Tomoatsu
T
Wurtzel
Lindsey
L
Jin
Taocong
T
Chang
Jia
J
Wang
Shaomeng
S
Wang
Cun-Yu
CY
Strieter
Robert M
RM
Nunez
Gabriel
G
Polverini
Peter J
PJ
Nör
Jacques E
JE
D000818:Animals; D002478:Cells, Cultured; D054360:Chemokine CXCL1; D019743:Chemokines, CXC / Q000096:biosynthesis / Q000502:physiology*; D016510:Corneal Neovascularization; D042783:Endothelial Cells; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis / Q000502:physiology*; D016209:Interleukin-8 / Q000096:biosynthesis / Q000502:physiology*; D016328:NF-kappa B / Q000502:physiology*; D018919:Neovascularization, Physiologic / Q000502:physiology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology; D014162:Transfection; D015854:Up-Regulation
C475829:CXCL1 protein, human; D054360:Chemokine CXCL1; D019743:Chemokines, CXC; D036341:Intercellular Signaling Peptides and Proteins; D016209:Interleukin-8; D016328:NF-kappa B; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering