Annexin A5 for Early Detection of Response to Chemotherapy

Tc-HYNIC-annexin A5 can be considered as a benchmark in the field of apoptosis imaging. However, Tc-HYNICannexin A5 has characteristics of high uptake and long retention in non-target tissues such as kidney and liver. To minimize this problem, we developed a novel Tc-labeled annexin A5 using a bis(hydroxamamide) derivative [C3(BHam)2] as a bifunctional chelating agent, and evaluated its usefulness as an imaging agent for detecting apoptosis. The amino group of C3(BHam)2 was converted to a maleimide group, and was coupled to thiol groups of annexin A5 pretreated with 2iminothiolane. Tc labeling was performed by a ligand exchange reaction with Tc-glucoheptonate. Biodistribution experiments for both Tc-C3(BHam)2-annexin A5 and Tc-HYNIC-annexin A5 were performed in normal mice. In addition, in tumor-bearing mice, the relationship between the therapeutic effects of chemotherapy (5-FU) and the tumor accumulation of Tc-C3(BHam)2-annexin A5 just after the first treatment of 5-FU was evaluated. Tc-C3(BHam)2-annexin A5 was prepared with a radiochemical purity of over 95%. In biodistribution experiments, Tc-C3(BHam)2-annexin A5 had a much lower kidney accumulation of radioactivity than Tc-HYNIC-annexin A5. In the organs for metabolism, such as liver and kidney, radioactivity after the injection of Tc-HYNIC-annexin A5 was residual for a long time. On the other hand, radioactivity after the injection of Tc-C3(BHam)2-annexin A5 gradually decreased. In therapeutic experiments, tumor growth in the mice treated with 5-FU was significantly inhibited. Accumulation of Tc-C3(BHam)2-annexin A5 in tumors significantly increased after 5-FU treatment. The accumulation of radioactivity in tumor correlated positively with the counts of TUNEL-positive cells. These findings suggest that Tc-C3(BHam)2-annexin A5 may contribute to the efficient detection of apoptotic tumor response after chemotherapy. Citation: Ogawa K, Ohtsuki K, Shibata T, Aoki M, Nakayama M, et al. (2013) Development and Evaluation of a Novel Tc-Labeled Annexin A5 for Early Detection of Response to Chemotherapy. PLoS ONE 8(12): e81191. doi:10.1371/journal.pone.0081191 Editor: Francisco X. Real, Centro Nacional de Investigaciones Oncológicas (CNIO), Spain Received February 21, 2013; Accepted October 16, 2013; Published December 4, 2013 Copyright: 2013 Ogawa et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported in part by Grants-in-Aid for Young Scientists (B) (KAKENHI Grant Number 18790879) from the Ministry of Education, Culture, Sports, Science and Technology of Japan. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. No additional external funding received for this study. Competing Interests: Kazuma Ogawa received annexin A5 as a donation from Kowa Co. Ltd. The other authors have declared that no competing interests exist. This does not alter the authors’ adherence to all the PLOS ONE policies on sharing data and materials. * E-mail: [email protected]