The mechanism of cancer-mediated conversion of plasminogen to the angiogenesis inhibitor angiostatin.
Angiostatin, a potent naturally occurring inhibitor of angiogenesis and growth of tumor metastases, is generated by cancer-mediated proteolysis of plasminogen. Human prostate carcinoma cells (PC-3) release enzymatic activity that converts plasminogen to angiostatin. We have now identified two components released by PC-3 cells, urokinase (uPA) and free sulfhydryl donors (FSDs), that are sufficient for angiostatin generation. Furthermore, in a defined cell-free system, plasminogen activators [uPA, tissue-type plasminogen activator (tPA), or streptokinase], in combination with one of a series of FSDs (N-acetyl-L-cysteine, D-penicillamine, captopril, L-cysteine, or reduced glutathione] generate angiostatin from plasminogen. An essential role of plasmin catalytic activity for angiostatin generation was identified by using recombinant mutant plasminogens as substrates. The wild-type recombinant plasminogen was converted to angiostatin in the setting of uPA/FSD; however, a plasminogen activation site mutant and a catalytically inactive mutant failed to generate angiostatin. Cell-free derived angiostatin inhibited angiogenesis in vitro and in vivo and suppressed the growth of Lewis lung carcinoma metastases. These findings define a direct mechanism for cancer-cell-mediated angiostatin generation and permit large-scale production of bioactive angiostatin for investigation and potential therapeutic application.
Gately
S
S
Department of Medicine, Division of Hematology/Oncology, Northwestern University School of Medicine, Chicago, IL 60611, USA.
Twardowski
P
P
Stack
M S
MS
Cundiff
D L
DL
Grella
D
D
Castellino
F J
FJ
Enghild
J
J
Kwaan
H C
HC
Lee
F
F
Kramer
R A
RA
Volpert
O
O
Bouck
N
N
Soff
G A
GA
D043168:Angiostatins; D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism*; D018827:Carcinoma, Lewis Lung / Q000378:metabolism / Q000473:pathology; D002474:Cell-Free System; D002846:Chromatography, Affinity; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009389:Neovascularization, Pathologic / Q000517:prevention & control*; D010446:Peptide Fragments / Q000096:biosynthesis* / Q000302:isolation & purification; D010958:Plasminogen / Q000096:biosynthesis* / Q000302:isolation & purification / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology
D000970:Antineoplastic Agents; D010446:Peptide Fragments; D043168:Angiostatins; D010958:Plasminogen