The effect of intracellular protein delivery on the anti-tumor activity of recombinant human endostatin
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Published on: January 4, 2012
Junghee Lim1, Tam Duong, Guewha Lee
1ProCell R&D Institute, ProCell Therapeutics, Inc., Seoul 151-050, Republic of Korea.
Abstract:
Endostatin (ES), a 20 kDa protein derived from the carboxy-terminus of collagen XVIII is a potent angiogenesis inhibitor, but clinical development has been hindered by poor clinical efficacy and insufficient functional information from which to design agents with improved activity. The present study investigated protein uptake by cells as a determinant of ES activity. We developed a cell-permeable ES protein (HM73ES) with enhanced capacity to enter cells by adding a macromolecule transduction domain (MTD). HM73ES inhibited angiogenesis-associated phenotypes in cultured endothelial cells [as assessed by tube formation, wound-healing, cell proliferation and survival assays]. These effects were accompanied by reductions in MAPK signaling (ERK phosphorylation), and in β-Catenin, c-Myc, STAT3, and VEGF protein expression. The cell-permeable ES displayed greater tissue penetration in mice and suppressed the growth of human tumor xenografts to a significantly greater extent than ES protein without the MTD sequence. Our results suggest that anti-angiogenic activities of native ES are limited at the level of protein uptake and/or subcellular localization, and that much of the activity of ES against tumors depends on one or more intracellular functions. This study will inform future efforts to understand ES function(s) and suggest strategies for improving ES-based cancer therapeutics.
Insights
Cell permeability enhances endostatin (ES) protein activity against tumors. Modifying ES to enter cells improved its anti-angiogenic effects and tumor suppression, suggesting intracellular functions are key for cancer therapeutics.
Area of Science:
- Biochemistry
- Molecular Biology
- Cancer Research
Background:
- Endostatin (ES), an angiogenesis inhibitor derived from collagen XVIII, has potential in cancer therapy.
- Clinical efficacy of ES is limited by poor cellular uptake and insufficient understanding of its mechanisms.
- Improving protein delivery and intracellular targeting is crucial for enhancing ES activity.
Purpose of the Study:
- To investigate cellular uptake as a key determinant of endostatin (ES) activity.
- To develop a cell-permeable ES variant with enhanced anti-angiogenic and anti-tumor properties.
- To elucidate the intracellular mechanisms underlying ES anti-cancer effects.
Main Methods:
- Engineered a cell-permeable ES variant (HM73ES) by incorporating a macromolecule transduction domain (MTD).
- Assessed HM73ES effects on endothelial cell phenotypes (tube formation, migration, proliferation, survival) in vitro.
- Analyzed downstream signaling pathways (MAPK, β-Catenin, c-Myc, STAT3, VEGF) affected by HM73ES.
- Evaluated tissue penetration and tumor growth suppression in mouse xenograft models.
Main Results:
- HM73ES demonstrated potent inhibition of angiogenesis-associated endothelial cell behaviors.
- HM73ES treatment led to reduced MAPK signaling and suppressed key proteins (β-Catenin, c-Myc, STAT3, VEGF).
- The cell-permeable ES exhibited superior tissue penetration and significantly suppressed tumor xenograft growth compared to native ES.
Conclusions:
- Cellular uptake and subcellular localization significantly limit the anti-angiogenic activity of native endostatin.
- The enhanced anti-tumor efficacy of HM73ES highlights the importance of intracellular ES functions.
- This study provides a foundation for developing improved endostatin-based cancer therapeutics by optimizing protein delivery and targeting.
