Study for Preparation of 99mTc-Annexin V and Its Application to Image Chemotherapy-Induced Apoptosis of Tumor-Bearing Animal Model with MicroSPECT (II)

Apoptosis, also known as programmed cell death, plays a crucial role in both normal and various diseases processes. One of the earliest events in apoptosis is the externalization of phosphotidylserine (PS) that normally locates in the inner side of the cell membrane. It is known that Annexin V possesses high affinity for membrane-bound PS. This property has been employed to detect apoptosis. Annexin V labeled with radionuclides allows detection of apoptosis in vivo and provides real-time nuclear imaging in experimental animals for monitoring anti-tumor efficacy of potential anti-neoplasmic agents, and for developing imaging approach to evaluate apoptosis in human. 99mTc is the most widely used radionuclide in nuclear medicine. The first objective of this project is to develop technique for preparation of 99mTc-labeled Annexin V in a simple manner. It has been demonstrated that nuclear imaging of tumor cell metabolic activity with 18F-FDG is a sensitive approach to detect tumors in vivo. However, measurement of tumor cell apoptosis in vivo using microSPECT imaging has not yet been reported. Accordingly, the second objective of this project is to establish a nuclear imaging technique for detection of tumor cell apoptosis in syngeneic tumor models. Tumor apoptosis will be induced by chemotherapeutic agents. The changes of tumor metabolic activity and apoptotic progress will be monitored by 18F-FDG microPET and 99mTc-Annexin V microSPECT, respectively. This project employs the two powerful techniques of nuclear imaging presently known and via corroboration with the Institute of Nuclear Energy Research to develop imaging techniques for real-time in vivo detection of tumor apoptosis. In the first year (2004) of this project, following topics are underwent: (1) to develop reliable methods for labeling annexin V with 99mTc and for determination of radiochemical purity for the imaging tracer; (2) to establish B16 and CT-26 syngenic tumor models; (3) to develop imaging techniques for detection of tumor metabolic activity using 18F-FDG microPET in B16 and CT-26 animal models. The specific aims of this project in the second year (2005) are as follows: 1. Establish a kit formulation that allows preparation of 99mTc-Annexin V in a simple manner, and determine the radiochemical purity of the imaging tracer. 2. Develop imaging techniques for detection of tumor apoptosis using 99mTc-Annexin V microSPECT in B16 and CT-26 animal models. 3. Confirm tumor apoptosis with in situ TUNEL assays using tumor tissue sections. 4. Characterize the expression profile of genes associated with apoptosis employing RNase protection assays.

Project ID:PC9402-0020
External Project ID:NSC94-2623-7182-005