Assessment of antiangiogenic effect using 99mTc-EC-endostatin.
OBJECTIVE
Tumor vascular density may provide a prognostic indicator of metastatic potential or survival. The purpose of this study was to develop 99mTc-ethylenedicysteine-endostatin (99mTc-EC-endostatin) for the evaluation of anti-angiogenesis therapy.


METHODS
99mTc-EC-endostatin was prepared by conjugating ethylenedicysteine (EC) to endostatin, followed by adding pertechnetate and tin chloride. Radiochemical purity was > 95%. In vitro cell viability, affinity and TUNEL assays were performed. Tissue distribution and planar imaging of radiolabeled endostatin were determined in tumor-bearing rats. To assess anti-angiogenic treatment response, rats were treated with endostatin, paclitaxel and saline, followed by imaging with 99mTc-EC-endostatin. Tumor response to endostatin therapy in tumor-bearing animal models was assessed by correlating tumor uptake dose with microvessel density, VEGF, bFGF and IL-8 expression during endostatin therapy.


RESULTS
In vitro cell viability and TUNEL assays indicated no marked difference between EC-endostatin and endostatin. Cellular uptake assay suggests that endostatin binds to endostatin receptor. Biodistribution of 99mTc-EC-endostatin in tumor-bearing rats showed increased tumor-to-tissue count density ratios as a function of time. Tumor uptake (%ID/g) of 99mTc-EC-endostatin was 0.2-0.5. Planar images confirmed that the tumors could be visualized clearly with 99mTc-EC-endostatin. The optimal time for imaging using radiolabeled endostatin was 2 hrs. 99mTc-EC-endostatin could assess treatment response. There was a correlation between tumor uptake and cellular targets expression.


CONCLUSIONS
The results indicate that it is feasible to use 99mTc-EC-endostatin to assess efficiency of anti-angiogenesis therapy.
Yang
David J
DJ
Department of Nuclear Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas, USA. dyang@di.mdacc.tmc.edu
Kim
Kil-Dong
KD
Schechter
Naomi R
NR
Yu
Dong-Fang
DF
Wu
Peng
P
Azhdarinia
Ali
A
Roach
Jennifer S
JS
Kalimi
Saady K
SK
Ozaki
Kaoru
K
Fogler
William E
WE
Bryant
Jerry L
JL
Herbst
Roy
R
Abbruzzes
James
J
Kim
E Edmund
EE
Podoloff
Donald A
DA
D020533:Angiogenesis Inhibitors / Q000493:pharmacokinetics / Q000627:therapeutic use*; D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D003094:Collagen / Q000493:pharmacokinetics / Q000627:therapeutic use*; D003545:Cysteine / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000627:therapeutic use*; D043169:Endostatins; D016228:Endothelial Growth Factors / Q000378:metabolism; D005260:Female; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism; D020287:In Situ Nick-End Labeling; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D008222:Lymphokines / Q000378:metabolism; D008325:Mammary Neoplasms, Experimental / Q000098:blood supply* / Q000000981:diagnostic imaging; D009389:Neovascularization, Pathologic / Q000188:drug therapy* / Q000378:metabolism; D017239:Paclitaxel / Q000494:pharmacology; D010446:Peptide Fragments / Q000493:pharmacokinetics / Q000627:therapeutic use*; D011877:Radionuclide Imaging; D051381:Rats; D011916:Rats, Inbred F344; D013667:Technetium / Q000493:pharmacokinetics / Q000627:therapeutic use; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D020533:Angiogenesis Inhibitors; D043169:Endostatins; D016228:Endothelial Growth Factors; D036341:Intercellular Signaling Peptides and Proteins; D016209:Interleukin-8; D008222:Lymphokines; D010446:Peptide Fragments; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; C109063:ethylene dicysteine; D016222:Fibroblast Growth Factor 2; D013667:Technetium; D003094:Collagen; D003545:Cysteine; D017239:Paclitaxel