Angiostatin II is the predominant glycoform in pleural effusates of rabbit VX-2 lung tumors.

Abstract

Angiostatin (AST), a polypeptide with potent antiangiogenic properties, is released proteolytically from plasminogen in vivo. Plasminogen exists naturally in plasma as two glycoforms (PLGs), I and II. Recently it was shown with the use of a chick-embryo chorioallantoic membrane (CAM) assay that rabbit PLG-I and -II yield distinct ASTs-AST-I and -II, respectively-with different antiangiogenic activities. AST glycoforms were of similar molecular weight, approximately 30 to 32,000 kD, and probably consisted of kringles 1 to 3 only. AST has now been identified in the interpleural effusate released from VX-2 lung tumors in rabbits. Effusate was collected from six rabbits with high tumor burdens and fractionated by means of lysine-Sepharose chromatography. The epsilon-aminohexanoic acid-eluted protein of all effusates contained AST (kringles 1-3) at a mean concentration of 1.2 microg/mL of effusate; with regard to AST content, 97% was AST-II. A CAM assay revealed that the lysine-Sepharose-bound fraction from all interpleural effusates contained potent antiangiogenic activity. Blood and urine from rabbits with high burdens of VX-2 contained essentially only AST-II, at mean concentrations of 145 and 4 ng/mL, respectively. AST was absent from the blood of control rabbits. In an attempt to compare their uptake by VX-2, iodine 125-labeled AST-I and iodine 131-labeled AST-II were injected intravenously into tumor-bearing rabbits. AST-I entered the tumor 1.6 times faster than AST-II. As a means of accounting for the preponderance of AST-II in the interpleural effusate, we postulate that VX-2 cells release proteolytic activity to activate plasminogen but that of the two PLGs, PLG-II may be the preferred substrate for AST formation in vivo.

• Authors: Mark W C Hatton, Suzanne M R Southward, Bonnie L Ross, Kimberly Legault, Lindsay Marien, Darren Korbie, Mary Richardson, Gurmit Singh, Bryan J Clarke, Morris A Blajchman
• Journal: The Journal of laboratory and clinical medicine (J Lab Clin Med) Vol. 139 Issue 5 Pg. 316-23 (May 2002) ISSN: 0022-2143 [Print] United States
• PMID: 12032493 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Iodine Radioisotopes
• Peptide Fragments
• Protein Isoforms
• Angiostatins
• Plasminogen

Topics

• Angiostatins
• Animals
• Blotting, Western
• Chickens
• Chromatography, Affinity
• Electrophoresis, Polyacrylamide Gel
• Humans
• Iodine Radioisotopes
• Lung Neoplasms (metabolism, pathology)
• Molecular Weight
• Neoplasm Transplantation
• Peptide Fragments (analysis, metabolism)
• Plasminogen (analysis, metabolism)
• Pleural Effusion (chemistry)
• Protein Isoforms (analysis, metabolism)
• Rabbits
• Tumor Cells, Cultured