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Updated: Jun 26, 2026
Modified Annexin V/Propidium Iodide Apoptosis Assay For Accurate Assessment of Cell Death
Published on: April 24, 2011
Radiolabeled annexin V for imaging apoptosis in radiated human follicular thyroid carcinomas--is an individualized
Jirka Grosse1, Daniela Grimm, Kriss Westphal
1Department of Nuclear Medicine, University of Regensburg, 93042 Regensburg, Germany. jirka.grosse@klinik.uni-regensburg.de
Introduction:
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.
Conclusion:
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.
