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A recombinant human angiostatin protein inhibits experimental primary and metastatic cancer
B K Sim1, M S O'Reilly, H Liang
1EntreMed, Inc., Rockville, Maryland 20850, USA.
Abstract:
Endogenous murine angiostatin, identified as an internal fragment of plasminogen, blocks neovascularization and growth of experimental primary and metastatic tumors in vivo. A recombinant protein comprising kringles 1-4 of human plasminogen (amino acids 93-470) expressed in Pichia pastoris had physical properties (molecular size, binding to lysine, reactivity with antibody to kringles 1-3) that mimicked native angiostatin. This recombinant Angiostatin protein inhibited the proliferation of bovine capillary endothelial cells in vitro. Systemic administration of recombinant Angiostatin protein at doses of 1.5 mg/kg suppressed the growth of Lewis lung carcinoma-low metastatic phenotype metastases in C57BL/6 mice by greater than 90%; administration of the recombinant protein at doses of 100 mg/kg also suppressed the growth of primary Lewis lung carcinoma-low metastatic phenotype tumors. These findings demonstrate unambiguously that the antiangiogenic and antitumor activity of endogenous angiostatin resides within kringles 1-4 of plasminogen.
Insights
Endogenous angiostatin, a plasminogen fragment, inhibits tumor growth. Recombinant kringles 1-4 of human plasminogen mimic this antiangiogenic and antitumor activity, demonstrating their therapeutic potential.
Area of Science:
- Biochemistry
- Molecular Biology
- Oncology
Background:
- Endogenous angiostatin, a plasminogen fragment, is known to inhibit neovascularization and tumor growth.
- The specific domains responsible for angiostatin's activity require further elucidation.
Purpose of the Study:
- To characterize a recombinant protein comprising kringles 1-4 of human plasminogen.
- To evaluate the in vitro and in vivo antiangiogenic and antitumor efficacy of this recombinant protein.
Main Methods:
- Recombinant protein expression in Pichia pastoris.
- In vitro proliferation assays using bovine capillary endothelial cells.
- In vivo tumor growth suppression studies in C57BL/6 mice using Lewis lung carcinoma models.
Main Results:
- The recombinant protein exhibited physical properties similar to native angiostatin.
- Recombinant Angiostatin inhibited endothelial cell proliferation in vitro.
- Systemic administration significantly suppressed Lewis lung carcinoma metastases and primary tumor growth in vivo.
Conclusions:
- The antiangiogenic and antitumor activity of endogenous angiostatin is localized to kringles 1-4 of plasminogen.
- Recombinant kringles 1-4 represent a promising therapeutic agent for cancer treatment.