The Distribution And Scintigraphy Of ^99mTc Labeled NGR-interferon-alpha2a In Tumor Bearing Mice

Objective: To investigate the method of technetium indirect radiolabeling the interferon–alpha2a-NGR fusion protein (^99mTc- NGR-IFN-α2a), observe its distribution and scintigraphy in tumor bearing mice.Methods:1 :Ethylenedicystein was used as a bifunctional chelating agent and MDP as a medium chelating agent, two-step method applied to label EC-NGR-IFN-α2a with ^99mTc,and then, the radio-labeling rate, radiochemical purity of^99mTc-EC-NGR-IFN-α2a (RCP), the bioactivities of EC-NGR-IFN-α2a and ^99mTc-EC-NGR-IFN-α2a were identified as well. 2 : Tumor models were established by transplanted liver cancer MHCC97-H cells in the two haunch subcutises of SCID mice,21 models were divided into 7 groups ;each group were injected ^99mTc- NGR-IFN-α2a 7.4 MBq (0.2 mL) through vena caudalis and then killed them in 1,2,4,6,8,12 and 24h after injection, respectively. The blood ,main organs and tumor specimens were collected and weighed ,then the radioactive count in each specimen was measured with the method of time-decay correction to calculate the uptake percentage of the injected dose in per gram of specimen (%ID/g)of every model; defined the tumor as the target tissue(T), all other organs as the non-target tissues(NT), calculate the T/NT in different time point.3: Three model mice were used for scintigraphy7.4 MBq (0.2 mL) ^99mTc- NGR-IFN-α2a was injected into each through vena caudalis , radionuclide imaging was performed with SPECT 0.5,1,2,4,6,8,12 and 24h after injection ,respectively. Calculate the T/NT value with region of interest (ROI) technique.Results:1,Synthesis and radilabeling: the productivity of EC-NGR-IFN-α2a was 87%,and the radio-labeling rate was 86%, in room temperature, 0,0.5,1,2,4 and 24 h after labeling, the RCP of ^99mTc-EC-NGR-IFN-α2a was 96.2%±0.4%,93.0%±0.7%,89.8%±0.6%,82.0%±0.8%,70.8%±0.8% and 49.0%±0.9%, respectively; statistical analysis showed that the difference of P value of optical density (OD) among EC-NGR-IFN-α2a,^99mTc- EC-NGR-IFN-α2a and NGR-IFN-α2a was 0.685,0.887,0.585 ,respectively. 2,In vivo distribution:4h after injection, ^99mTc-NGR-IFN-α2a in the blood decreased rapidly, 1 h after injection, increasing counts were detected in kidneys and 2 hours after injection the counts in alimentary canal began to increase, furthermore, radioactive counts in the tumor continued increasing till 24 hours after injection; the T/NT value was26.5, and 14.9 was the average(through %ID/g). 3,Imaging of tumor bearing mice: Under the acquisition condition of matrix: 128×128, zoom:1.33,count:200k/frame,0.5h after injection, the transplanted tumor began to be imaged, during 2⁸ h after injection, the tumor had the best image; the highest T/NT value was 14.5, and the average was 9.8 (from ROI).Conclusion:Firstly, the synthesis procedure of EC-NGR-IFN-α2a is relatively simple with mild reaction conditions and high productivity, and EC-NGR-IFN-α2a is easy to be labeled with ^99mTc; the radiolabelled compound had good stability in vitro. Secondly, ^99mTc-NGR-IFN-α2a can be quickly cleared from blood and mostly it was excreted through alimentary canal and urinary tract. Therefore it is a good candidate for tumor targeting. Thirdly, since the high T/NT can be acquired with ^99mTc-NGR-IFN-α2a, it can be a good pharmacon in radionuclide tumor vessel target imaging and therapy.