Direct targeting of tumor cell F(1)F(0) ATP-synthase by radioiodine angiostatin in vitro and in vivo.
Recent discoveries have identified endothelial cell-surface F(1)F(0) adenosine triphosphate (ATP) synthase as the key target for angiostatin (AST) action. As this enzyme is also present on tumor cells, we investigated whether radiolabeled AST may directly target cancer cell-surface ATP synthase in vitro and in vivo.


METHODS
Cell-binding characteristics of (125)I-AST was evaluated on human umbilical vein endothelial (HUVE) and SNU-C5 colon carcinoma cells. The molecular target for binding was investigated with anti-ATP synthase antibodies and RGDyV. Biodistribution and imaging experiments were performed in mice xenografted with carcinoma and sarcoma tumors. Tumor localization of ATP synthase and exogenous AST was compared via double immunostaining.


RESULTS
Both HUVE and SNU-C5 cells showed specific (125)I-AST binding that was dose-dependently inhibited by excess AST, with IC(50) values of 3.5 and 0.2 microM, respectively. Both cell types stained positive for ATP synthase and demonstrated an approximately 50% reduction in AST binding by antibodies against the alpha- and beta-subunit of the enzyme. (123)I-AST injected in mice allowed for the clear tumor visualization with significant tumor accumulation and uptake ratios. Immunostaining revealed a localization of exogenous AST to closely correlate to that of tumor-cell ATP synthase.


CONCLUSIONS
AST can directly target tumor-cell ATP synthase, and AST imaging may thus be useful for monitoring tumor ATP synthase expression.
Jung
Kyung-Ho
KH
Department of Nuclear Medicine, Samsung Medical Center, and Sungkyunkwan University School of Medicine, Seoul, Korea.
Song
Sung-Hee
SH
Paik
Jin-Young
JY
Koh
Bong-Ho
BH
Choe
Yearn Seong
YS
Lee
Eun Jung
EJ
Kim
Byung-Tae
BT
Lee
Kyung-Han
KH
D015119:Aminocaproic Acid / Q000494:pharmacology; D043168:Angiostatins / Q000737:chemistry / Q000378:metabolism* / Q000493:pharmacokinetics; D000818:Animals; D000906:Antibodies / Q000276:immunology / Q000494:pharmacology; D002460:Cell Line; D045744:Cell Line, Tumor; D042783:Endothelial Cells / Q000378:metabolism; D006801:Humans; D007457:Iodine Radioisotopes / Q000737:chemistry*; D007553:Isotope Labeling; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009369:Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology; D011485:Protein Binding / Q000187:drug effects; D006180:Proton-Translocating ATPases / Q000276:immunology / Q000378:metabolism*; D011877:Radionuclide Imaging; D051381:Rats; D014018:Tissue Distribution; D023041:Xenograft Model Antitumor Assays
D000906:Antibodies; D007457:Iodine Radioisotopes; D043168:Angiostatins; D006180:Proton-Translocating ATPases; D015119:Aminocaproic Acid