Detection of apoptotic tumor response in vivo after a single dose of chemotherapy with 99mTc-annexin V.
Annexin V, a human protein with a high affinity for phosphatidylserine, has been labeled with (99m)Tc to detect apoptosis in vivo. To determine the effectiveness of imaging with this agent as a reflection of the degree of apoptosis after the first dose of chemotherapy, we studied rats with an engrafted hepatoma.


METHODS
Annexin V was labeled with (99m)Tc (specific activity, 3.0 MBq/ micro g protein). Eleven days after being inoculated with allogenic hepatoma cells (KDH-8) in the left calf muscle, the rats were randomized to receive a single dose of cyclophosphamide (150 mg/kg intraperitoneally) or to serve as controls. (99m)Tc-annexin V was injected 20 h later. Radioactivity in tissues was determined 6 h after injection of (99m)Tc-annexin V. Tumor uptake of (14)C-iodoanitpyrine was determined as a marker of tumor blood flow. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) of tissue harvested at necropsy was performed to detect apoptosis in the tumor.


RESULTS
Cyclophosphamide treatment significantly increased the tumor uptake (percentage activity of injected dose per gram of tissue after normalization to the animal's weight [%ID/g/kg]) of (99m)Tc-annexin V (0.070 +/- 0.007 %ID/g/kg for treated rats and 0.046 +/- 0.009 %ID/g/kg for controls, P < 0.001). (14)C-iodoantipyrine uptake was similar in the treated and untreated groups. The number of TUNEL-positive cells in the tumor was significantly larger in the treated rats (297.70 +/- 50.34 cells/mm(2)) than in the control rats (168.45 +/- 23.60 cells/mm(2), P < 0.001). Tumor uptake of (99m)Tc-annexin V correlated with the number of TUNEL-positive cells in the tumor (r = 0.712; P < 0.001).


CONCLUSIONS
Tumor uptake of (99m)Tc-annexin V was significantly increased by a single dose of cyclophosphamide treatment, and the increase was concordant with the number of TUNEL-positive cells in the tumor. The current results are suggestive of the utility of (99m)Tc-annexin V as a noninvasive means to assess tumor response, although further testing, including clinical evaluation, is required.
Mochizuki
Takafumi
T
Department of Radiology, Nikko Memorial Hospital, Muroran, Japan.
Kuge
Yuji
Y
Zhao
Songji
S
Tsukamoto
Eriko
E
Hosokawa
Masuo
M
Strauss
H William
HW
Blankenberg
Francis G
FG
Tait
Jonathan F
JF
Tamaki
Nagara
N
D000818:Animals; D017304:Annexin A5 / Q000493:pharmacokinetics*; D017209:Apoptosis / Q000187:drug effects*; D003520:Cyclophosphamide / Q000627:therapeutic use*; D004305:Dose-Response Relationship, Drug; D020287:In Situ Nick-End Labeling; D008114:Liver Neoplasms, Experimental / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D008297:Male; D009368:Neoplasm Transplantation; D015609:Organotechnetium Compounds / Q000493:pharmacokinetics*; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D051381:Rats; D017208:Rats, Wistar; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution; D016896:Treatment Outcome; D014407:Tumor Cells, Cultured
D017304:Annexin A5; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; C417036:technetium Tc 99m annexin V; D003520:Cyclophosphamide