The experimental study of 99Tcm-EC-MN in tumor hypoxia imaging

Objective: To study the biological distribution of 99Tcm-EC-MN in tumor models bearing nasopharyngeal carcinoma in vivo and that in vitro, and to explore the clinical significance of 99Tcm-EC-MN in tumor hypoxia imaging. Methods: EC-MN was labeled with technetium-99m, and the labeling efficacy was determined by paper chromatography. 99Tcm-EC-MN was added into the cell strains of nasopharyngeal carcinoma under the normal and hypoxia condition respectively, difference of distribution was examined in different periods of time. Tumor nude mice models bearing nasopharyngeal carcinoma was developed. 99Tcm-EC-MN(3.7 MBq) was injected into caudal vein in eight nude mice, and planar scanning was performed to observe the concentration of the 99Tcm-EC-MN in tumors after 0.5,1,2,4,6,8 h. The tumor-bearing nude mice were sacrificed in different phases after injection, and radioactive counts in tissue samples from various organs were measured to calculate %ID/g. The immunohistochemical study of tumor tissue was observed by using CD34 MoAb and VEGF McAb. Results: Significant difference (P<0.01) was detected in the absorption of 99Tcm-EC-MN between the cells of nasopharyngeal carcinoma under the normal conditions and those under the hypoxia condition. All of the tumor-bearing nude mice showed positive imaging, especially in 4 h after injection. The ratio between tumor and muscle in 1, 2, 4 h after injection was 2.24, 4.75 and 6.41. 99Tcm-EC-MN was rapidly removed from the normal tissue, mainly by the discharge from intestinal and urinary system. The results of immunohistochemical analysis was correlated with the radioactivity counts in tumor tissue (r>0.9, P<0.01). Conclusion: As a hypoxia imaging agent, 99Tcm-EC-MN has good prospects of exploitation. (authors)