Endorepellin in vivo: targeting the tumor vasculature and retarding cancer growth and metabolism.
BACKGROUND
The antiangiogenic approach to controlling cancer requires a better understanding of angiogenesis and the discovery of new compounds that modulate this key biological process. Here we investigated the role of endorepellin, an angiostatic protein fragment that is derived from the C-terminus of perlecan, a heparan sulfate proteoglycan, in controlling tumor angiogenesis in vivo.


METHODS
We administered human recombinant endorepellin systemically to mice bearing orthotopic squamous carcinoma xenografts or syngeneic Lewis lung carcinoma tumors. We monitored tumor growth, angiogenesis, metabolism, hypoxia, and mitotic index by using quantitative immunohistochemistry and positron emission tomography scan imaging. In addition, we determined the localization of injected endorepellin using near-infrared labeling and immunohistochemistry of frozen tumor sections. Finally, we isolated tumor-derived endothelial cells and tested whether endorepellin could interact with these cells and disrupt in vitro capillary morphogenesis. All statistical tests were two-sided.


RESULTS
Endorepellin specifically targeted the tumor vasculature as determined by immunohistochemical analysis and accumulated in the tumor perivascular zones where it persisted for several days as discrete deposits. This led to inhibition of tumor angiogenesis (as measured by decreased CD31-positive cells, mean control = 1902 CD31-positive pixels, mean endorepellin treated = 343.9, difference between means = 1558, 95% confidence interval [CI] = 1296 to 1820, P<.001), enhanced tumor hypoxia, and a statistically significant decrease in tumor metabolism and mitotic index (as measured by decreased Ki67-positive cells, mean control Ki67 pixels = 5970, mean endorepellin-treated Ki67 pixels = 3644, difference between means = 2326, 95% CI = 1904 to 2749, P<.001) compared to untreated controls. Endorepellin was actively internalized by tumor-derived endothelial cells causing a redistribution of alpha2beta1 integrin such that both proteins colocalized to punctate deposits in the perivascular region. Endorepellin treatment inhibited in vitro capillary morphogenesis of both normal and tumor-derived endothelia.


CONCLUSIONS
Our results provide support for the hypothesis that endorepellin is an effective antitumor vasculature agent that could be used as a therapeutic modality to combat cancer.
Bix
Gregory
G
Department of Pathology, Anatomy and Cell Biology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107, USA.
Castello
Remedios
R
Burrows
Michelle
M
Zoeller
Jason J
JJ
Weech
Michelle
M
Iozzo
Rex A
RA
Cardi
Christopher
C
Thakur
Mathew L
ML
Barker
Christopher A
CA
Camphausen
Kevin
K
Iozzo
Renato V
RV
D020533:Angiogenesis Inhibitors / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D000818:Animals; D017209:Apoptosis; D018827:Carcinoma, Lewis Lung / Q000098:blood supply / Q000188:drug therapy / Q000378:metabolism; D002294:Carcinoma, Squamous Cell / Q000098:blood supply / Q000188:drug therapy / Q000378:metabolism; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D042783:Endothelial Cells / Q000187:drug effects* / Q000378:metabolism; D005260:Female; D019812:Heparan Sulfate Proteoglycans / Q000008:administration & dosage / Q000378:metabolism / Q000627:therapeutic use*; D006801:Humans; D007150:Immunohistochemistry; D007263:Infusions, Parenteral; D038982:Integrin alpha2beta1 / Q000378:metabolism; D008297:Male; D051379:Mice; D008819:Mice, Nude; D008940:Mitotic Index; D009369:Neoplasms / Q000098:blood supply / Q000188:drug therapy* / Q000378:metabolism*; D009389:Neovascularization, Pathologic / Q000188:drug therapy*; D010446:Peptide Fragments / Q000008:administration & dosage / Q000378:metabolism / Q000627:therapeutic use*; D049268:Positron-Emission Tomography; D011897:Random Allocation; D011994:Recombinant Proteins / Q000627:therapeutic use; D014057:Tomography, X-Ray Computed; D014183:Transplantation, Heterologous
D020533:Angiogenesis Inhibitors; D019812:Heparan Sulfate Proteoglycans; D038982:Integrin alpha2beta1; D010446:Peptide Fragments; D011994:Recombinant Proteins; C071927:perlecan