The Distribution And Scintigraphy Of (188)~re Labeled Ngr-interferon- Alpha2a In Tumor Bearing Mice

Objective: To explore the method of the NGR-interferon alpha 2a labeled with ¹⁸⁸Re, and to investigate it's distribution and scintigraphy in tumor bearing mice.Methods:1 :Using SnCl2 as a reducing agent , NGR-IFN-α2a was labeled with ¹⁸⁸Re by directing method, then, determining the radio-labeling rate and the radiochemical purity, accrediting the bioactivities of NGR-IFN-α2a and ¹⁸⁸Re -NGR-IFN-α2a , carrying out the receptor competitive binding experiment at the same time.2: The tumor models were set up by liver cancer HEPG2 cells in the haunch subcutis of SCID mice, and then selected 40 models and normal mice each. The mice were divided into 8 groups,each group only five. ALL groups were injected by ¹⁸⁸Re - NGR-IFN-α2a 7.4 MBq (0.2 mL) through the mice vena caudalis .Next step ,killed the models and normal mice when the time is on 0.5,1,2,4,6,8,12 and 24h after injected, respectively. Collected the main organization;,the blood and the tumor ,then weighed the sample products ,and then measured the radioactive counts in each sample product , calculated the absorption rate of the injected dose in per gramme of sample product (%ID/g)of every model with the method of time-decay correction, selected the tumor as the target tissue(T), and selected the muscular tissue as the non-target tissue(NT) at the same time, compute the value of the T/NT in different time point.3: Selected five tumor model mice for scintigraphy,then, injected the ¹⁸⁸Re - NGR-IFN-α2a 7.4 MBq (0.2 mL) into each through the vena caudalis, after injected the radioactive marker on 0.5,1,2,4,6,8,12,24,48h,carried out the imaging with SPECT/CT ,respectively. Compute the value of the T/NT with region of interest (ROI) technique.Results:1,Radio-labeling: The radio-labeling rate of the ¹⁸⁸Re -NGR-IFN-α2a was higher than 80%,and the radiochemical purity was higher than 95%. Take the radioactive marker in room tempreture, the RCP of ¹⁸⁸Re -NGR-IFN-α2a was remain 57.3%±0.3% 24 h later, the max of the specificity cell conjugation rate was 44.80%. Statistical analysis showed that there is not any significant difference of optical density (OD)of wish cell treated by NGR-IFN-α2a and ¹⁸⁸Re -NGR-IFN-α2a, p value is more than 0.05. 2,The normal mice and the tumor-bearing mice distribution in vivo, 1 h after ¹⁸⁸Re -NGR-IFN-α2a was injected, increasing counts were detected in kidneys and the counts in alimentary canal began to increase 2h later, ¹⁸⁸Re -NGR-IFN-α2a was rapidly cleared from blood within 4h, furthermore, the crest-time was 6h after injection and radioactive counts in the tumor continued increasing till 24h after injection, the maxium T/NT value was 19.84, and the average was 12.39 (through %ID/g). 3,Imaging of the tumor bearing mice by SPECT/CT: Setting the acquisition condition of matrix:128×128, zoom:1.60, energy hump 155KeV,count:200k/frame,when the time at 0.5h after injection ,the tumor began to be imaged and become more clear at 4-8 h after injection, it still remain can be imaged at 48h.The highest T/NT value was 11.37, and the average was 7.37 according ROI technique. Conclusion:Firstly, NGR-IFN-α2a can be easily labeled by ¹⁸⁸Re,with high radio-labeling rate,radiochemical purity and good specificity cell conjugation rate.The radiolabelled compound is stable in vitro. Secondly, ¹⁸⁸Re -NGR-IFN-α2a is cleared from blood quickly and most of the residue radionuclide was excreted through urinary tract and partly through alimentary canal. The radioaction counts of other organs were reduced gradually. The tumor had high uptake rate and remained longer time. Thirdly, since ¹⁸⁸Re -NGR-IFN-α2a can specificity target tumor, it could be a good radionuclide pharmaceutical for tumor vessel target therapy.