An endogenous inhibitor of angiogenesis derived from a transitional cell carcinoma: clipped beta2-glycoprotein-I.
BACKGROUND
Invasive cell carcinoma of the bladder often develops after complete transurethral excision of superficial transitional cell carcinoma. It has been postulated that primary tumors release angiogenesis-blocking proteins which suppress distant metastases. We have identified an endogenous protein which might be responsible for tumor dormancy.


METHODS
A transitional cell carcinoma cell line was developed (UMUC-3i) which inhibits the growth of a tumor implant at a distant site in SCID mice. Conditioned media of UMUC-3i cultured cells was first pooled and then fractioned, and the capacity of individual components to block endothelial cell growth was tested. The protein fraction responsible for blocking endothelial cell growth was identified by N-terminal amino acid sequencing as well as by mass-spectrometry. The effects of the purified protein in preventing endothelial cell proliferation and tube formation in an in vitro angiogenesis assay was investigated.


RESULTS
The plasma protein beta(2)-glycoprotein-I (beta(2)gpI) was isolated and identified from conditioned medium of UMUC-3i cultured cells. Based on the in vitro angiogenesis assay, beta(2)gpI strongly inhibited endothelial cell growth and tube formation, whereby the inhibitory activity corresponded to the clipped version of beta(2)gpI (cbeta(2)gpI). Clipping was induced by adding plasmin at a molar ratio 1:15 (plasmin:substrate). Further analysis indicated that cbeta(2)gpI effects were mediated by annexin II surface receptors expressed on endothelial cells.


CONCLUSIONS
cbeta2gpI may be involved in blocking angiogenic processes and bladder cancer progression. In this case, cbeta2gpI may be a promising tool in bladder cancer therapy.
Beecken
Wolf-Dietrich C
WD
Department of Urology, JW Goethe University, Frankfurt am Main, Germany.
Engl
Tobias
T
Ringel
Eva M
EM
Camphausen
Kevin
K
Michaelis
Martin
M
Jonas
Dietger
D
Folkman
Judah
J
Shing
Yuen
Y
Blaheta
Roman A
RA
D020533:Angiogenesis Inhibitors / Q000627:therapeutic use*; D000818:Animals; D017306:Annexin A2 / Q000378:metabolism; D002295:Carcinoma, Transitional Cell / Q000098:blood supply / Q000378:metabolism / Q000628:therapy*; D049109:Cell Proliferation; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D005341:Fibrinolysin / Q000378:metabolism; D006023:Glycoproteins / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D013058:Mass Spectrometry; D051379:Mice; D016513:Mice, SCID; D009389:Neovascularization, Pathologic / Q000378:metabolism / Q000517:prevention & control*; D014471:Umbilical Veins / Q000166:cytology / Q000378:metabolism; D001749:Urinary Bladder Neoplasms / Q000098:blood supply / Q000378:metabolism / Q000628:therapy*; D053482:beta 2-Glycoprotein I
D020533:Angiogenesis Inhibitors; D017306:Annexin A2; D017077:Culture Media, Conditioned; D006023:Glycoproteins; D053482:beta 2-Glycoprotein I; D005341:Fibrinolysin