Radiolabeled annexin V for imaging apoptosis in radiated human follicular thyroid carcinomas--is an individualized protocol necessary?
BACKGROUND
Induction of apoptosis is a widely used strategy for cancer therapy, but evaluating the degree and success of this therapy still poses a problem. Radiolabeled annexin V has been proposed to be a promising candidate for detecting apoptotic cells in tumors following chemotherapy in vivo. In order to see whether radiolabeled annexin V could be a suitable substance for the noninvasive in vivo detection of apoptosis in thyroid tissue and to establish an optimized study protocol, we investigated two poorly differentiated thyroid carcinoma cell lines: ML-1 and FTC-133.


METHODS
Apoptosis was evaluated before as well as 2 and 4 days after in vitro irradiation with 30 Gy X-rays. In this study, binding of FITC- and of (125)I-labeled annexin V was measured in comparison to other apoptosis markers such as Bax, caspase-3 and Fas, which were determined by flow cytometry and Western blot analysis with densitometric evaluation.


RESULTS
ML-1 and FTC-133 cells showed a significant increase in annexin V binding 48 h after irradiation. Ninety-six hours after irradiation, the annexin V absorption capability of ML-1 cells was still maximal, while the living fraction of FTC-133 increased significantly. The amount of caspase-3 and Bax was clearly increased 48 h after irradiation and had normalized after 96 h in both cell lines. Fas protein concentrations remained unchanged in ML-1 cells but were significantly enhanced in FTC-133 cells.


CONCLUSIONS
The binding of FITC- and (125)I-labeled annexin V showed a significant accordance. A reliable evaluation of apoptosis induced by radiotherapy in thyroid tumors was possible 48 h after irradiation, when binding of radiolabeled annexin V is most significantly enhanced. Using two poorly differentiated cell lines of thyroid carcinoma, one may expect to find a nearly similar response to external irradiation. In contrast, the cell lines showed a completely contrary response. However, an individualized study protocol for each type of tumor and probably within each type is necessary.
Grosse
Jirka
J
Department of Nuclear Medicine, University of Regensburg, 93042 Regensburg, Germany. jirka.grosse@klinik.uni-regensburg.de
Grimm
Daniela
D
Westphal
Kriss
K
Ulbrich
Claudia
C
Moosbauer
Jutta
J
Pohl
Fabian
F
Koelbl
Oliver
O
Infanger
Manfred
M
Eilles
Christoph
C
Schoenberger
Johann
J
D000328:Adult; D017304:Annexin A5 / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism*; D017209:Apoptosis / Q000528:radiation effects*; D014408:Biomarkers, Tumor / Q000737:chemistry / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D002454:Cell Differentiation / Q000528:radiation effects; D045744:Cell Line, Tumor; D004789:Enzyme Activation / Q000528:radiation effects; D005260:Female; D005434:Flow Cytometry; D016650:Fluorescein-5-isothiocyanate / Q000737:chemistry; D006801:Humans; D007457:Iodine Radioisotopes / Q000737:chemistry; D008297:Male; D008875:Middle Aged; D013194:Staining and Labeling; D013964:Thyroid Neoplasms / Q000175:diagnosis / Q000473:pathology* / Q000532:radiotherapy*; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D019014:fas Receptor / Q000378:metabolism
D017304:Annexin A5; D014408:Biomarkers, Tumor; C491901:FAS protein, human; D007457:Iodine Radioisotopes; D051028:bcl-2-Associated X Protein; D019014:fas Receptor; D053148:Caspase 3; D016650:Fluorescein-5-isothiocyanate