Evaluation Of^99mTc And⁶⁸Ga Labeled TMTP1and TMVP1as A Tumor-homing Molecular Imaging Agent

Objective:1. Evaluation of99mTc-HYNIC-TMTP1as a tumor-homing imaging agent targeting metastasis with SPECT2. Evaluation of99mTc-HYNIC-TMVP1for SPECT imaging of vascular endothelial growth factor receptor3.3. Evaluation of68Ga-DOTA-TMVP1for PET imaging of vascular endothelial growth factor receptor3Methods:1.99mTc-HYNIC-TMTP1,99mTc-HYNIC-TMVP1and68Ga-DOTA-TMVP1were synthesized, and purified by Sep-pak c18catridges. Then the RCP of three radiotracers were analyzed by iTLC-sg and HPLC. 2. The stability of three radiotracers in saline, cysteine and human serum was analyzed by iTLC-sg and HPLC.3. Tumor-bearing mice were established. The radiotracer was injection into the mouse models by vein. Then, the mice were subjected to examination of SPECT imaging or microPET imaging at different time points. The blocking experiments were also performed by co-injection of excess corresponding peptide.4. The biodistribution of three radiopharmacetics was achieved in corresponding tumor-bearing mice. Meanwhile, the receptor of peptide were examined by western blot or IHC.Results:1.99mTc-HYNIC-TMTP1was successfully synthesized. The radiotracer also exhibited high hydrophilicity and excellent stability in vitro and in vivo. It has strong affinity to highly metastatic cancer cell lines but not to poorly metastatic cell lines. After mice were injected with99mTc-HYNIC-TMTP1, non-invasive SPECT imaging detected SKOV3.ip and MNK-45xenograft tumors but not SKOV3xenograft tumors. This result can be inhibited by excess HYNIC-TMTP1. The uptake of99m Tc-HYNIC-TMTP1in SKOV3.ip xenograft tumors was0.182±0.017%ID/g at2h p.i. with high renal uptake (74.32±15.05%ID/g at2h p.i.).2.99mTc-HYNIC-TMVP1and68Ga-DOTA-TMVP1were obtained in>95%labeling yield with favorably stability. In vitro studies demonstrated that the RCP of99mTc-HYNIC-TMVP1in saline, human normal serum and cysteine was>90%after four hours; the RCP of68Ga-DOTA-TMVP1in saline and human normal serum were also>95%after three hours. Then, the SPECT images showed that the tumors and the kidney were obviously seen after injection of99mTc-HYNIC-TMVP1at2h and4h. the PET images could detected the xenograft tumors. The biodistribution showed that the uptake of4T1tumors of99mTc-HYNIC-TMVP1was0.31±0.055%ID/g, the kidney was 8.35±1.46%ID/g, the blood was0.07±0.03%ID/g and the muscle was0.014±0.001%ID/g. For the68Ga-DOTA-TMVP1, the uptake of C33A tumors was2.00±0.24%ID/g, the the kidney was2.74±0.30%ID/g, the blood was0.66±0.01%ID/g and the muscle was0.26±0.28%ID/g.Conclusion:1.99mTc-HYNIC-TMTP1biodistribution and SPECT imaging demonstrated its ability to target highly metastatic tumors. Meanwhile, this radiotracer has some shortages in the low%ID/g of tumors and high accumulation in the kidney.2.99mTc-HYNIC-TMVP1and68Ga-DOTA-TMVP1could be two potential radiotracers for VEGFR3imaging and detection of tumors...