Angiostatin anti-angiogenesis requires IL-12: the innate immune system as a key target.
BACKGROUND
Angiostatin, an endogenous angiogenesis inhibitor, is a fragment of plasminogen. Its anti-angiogenic activity was discovered with functional assays in vivo, however, its direct action on endothelial cells is moderate and identification of definitive mechanisms of action has been elusive to date. We had previously demonstrated that innate immune cells are key targets of angiostatin, however the pathway involved in this immune-related angiogenesis inhibition was not known. Here we present evidence that IL-12, a principal TH1 cytokine with potent anti-angiogenic activity, is the mediator of angiostatin's activity.


METHODS
Function blocking antibodies and gene-targeted animals were employed or in vivo studies using the subcutaneous matrigel model of angiogenesis. Quantitative real-time PCR were used to assess modulation of cytokine production in vitro.


RESULTS
Angiostatin inhibts angiogenesis induced by VEGF-TNFalpha or supernatants of Kaposi's Sarcoma cells (a highly angiogenic and inflammation-associated tumor). We found that function-blocking antibodies to IL-12 reverted angiostatin induced angiogenesis inhibition. The use of KO animal models revealed that angiostatin is unable to exert angiogenesis inhibition in mice with gene-targeted deletions of either the IL-12 specific receptor subunit IL-12Rbeta2 or the IL-12 p40 subunit. Angiostatin induces IL-12 mRNA synthesis by human macrophages in vitro, suggesting that these innate immunity cells produce IL-12 upon angiostatin stimulation and could be a major cellular mediator.


CONCLUSIONS
Our data demonstrate that an endogenous angiogenesis inhibitor such as angiostatin act on innate immune cells as key targets in inflammatory angiogenesis. Angiostatin proves to be anti-angiogenic as an immune modulator rather than a direct anti-vascular agent. This article is dedicated to the memory of Prof Judah Folkman for his leadership and for encouragement of these studies.
Albini
Adriana
A
Polo Scientifico e Tecnologico, IRCCS Multimedica, Milan, Italy. adriana.albini@mulitmedica.it
Brigati
Claudio
C
Ventura
Agostina
A
Lorusso
Girieca
G
Pinter
Marta
M
Morini
Monica
M
Mancino
Alessandra
A
Sica
Antonio
A
Noonan
Douglas M
DM
D020533:Angiogenesis Inhibitors / Q000276:immunology* / Q000627:therapeutic use; D043168:Angiostatins / Q000276:immunology*; D000818:Animals; D045744:Cell Line, Tumor; D018932:Chemokine CCL2 / Q000276:immunology; D006801:Humans; D007107:Immune System / Q000276:immunology*; D007113:Immunity, Innate / Q000276:immunology*; D018664:Interleukin-12 / Q000276:immunology*; D016209:Interleukin-8 / Q000276:immunology; D008264:Macrophages / Q000166:cytology / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008819:Mice, Nude; D009369:Neoplasms / Q000188:drug therapy / Q000276:immunology; D009389:Neovascularization, Pathologic; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology; D042461:Vascular Endothelial Growth Factor A / Q000276:immunology
D020533:Angiogenesis Inhibitors; D018932:Chemokine CCL2; D016209:Interleukin-8; D014409:Tumor Necrosis Factor-alpha; D042461:Vascular Endothelial Growth Factor A; D018664:Interleukin-12; D043168:Angiostatins