| Objective:A micro-molecule polypeptide TP1623 of 99Tcm-human epithelial growth factor receptor 2(HER2)was prepared and the feasibility of used it as a HER2-positive molecular imaging agent for breast cancer was evaluated in vivo and vitro.Methods:1.Prepared and Identified of 99Tcm-TP1623: TP1623 was synthesized by chemosynthesis,and then labeled with 99 Tcm.The labeling rate and specific activity of the labeled mixture were measured by chromatography,and then tested stability in vitro.2.Identified the vitro activity of 99Tcm-TP1623: HER2 expression levels of breast cancer cells(SKBR3 and MDA-MB-231)were measured by cell immunohistochemistry,the vitro activity of 99Tcm-TP1623 was being analyzed by saturation and competition binding assay.3.set up and identified the model of nude mice bearing breast tumor with high/low expressions of HER2: SKBR3/MDA-MB-231-bearing nude mice models with high/low expressions of HER2 were established.Tumor tissues were stained with pathologic and measured by immunohistochemistry to confirm the formation of tumors and HER2 expression.4.SPECT imaged and competitive imaged of 99Tcm-TP1623 in tumor bearing nude mice: 99Tcm-TP1623 was injected into the caudal vein of the mice and SPECT imaging was conducted for HER2-overexpressing SKBR3-bearing nude mice,The T/NT ratio was calculated and compared with that of MDA-MB-231-bearing nude mice with low HER2 expression.After three days in the study of competitive imaging,500 folds peptide was injected through caudal vein in same animals,the99Tcm-TP1623 was injected and imaged at the same way in 1h later,The competitive inhibition image was used to discuss the specific binding of 99Tcm-TP1623 and the tumor.Results:1.Prepared and Identified of 99Tcm-TP1623: The labeling ratio and specific activity of 99Tcm-TP1623 were(97.39 ± 0.23)% ?(24.61 ± 0.06)TBq/mmol.And radiochemical purity(RCP)in 0h,2h,4h and 6h at room temperature were(97.39±0.23)%,(94.66±1.49)%,(93.28±1.08)%,(93.25±0.06)%,respectively.And RCP in serum were(97.14±0.45)%,(93.36 ±1.78)%,(92.81 ±0.32)%,(90.57 ±0.67)%,(86.02±1.34)%?2.Identified the vitro activity of 99Tcm-TP1623: HER2 of SKBR3 and MDA-MB-231 cells showed high and low expression levels by cell immunohistochemistry,respectively.The in vitro receptor assays indicated that specific binding of TP1623 and HER2 was retained.3.established and identified the model of nude mice bearing breast tumor: HE staining showed that tumor cells were observed in SKBR3 and MDAMB-231-bearing nude mice,with significant heteromorphism and increased mitotic count.HER2 of SKBR3 and MDA-MB-231 bearing nude mice showed high and low expression levels by immunohistochemistry.4.imaged study of 99Tcm-TP1623 in tumor bearing nude mice: The imaging of mice showed that targeted images could be made of 99Tcm-TP1623 in high HER2-expressing tumors,And most radioactivities were eliminated through kidneys.while no obvious development was shown in tumors in low HER2-expressing nude mice.No development was visible in tumors in competitive inhibition of imaging,which indicated the combination of 99Tcm-TP1623 with overexpressed HER2 tumor was mediated by HER2.Conclusions:1.99Tcm-TP1623 could be successfully prepared with high labeling rate and specific activity,its stability well in vitro and still had a high affinity and specificity with HER2 receptors.The preparation method was simple and cheap,and its the benefit of to be one-step freeze-dried kit for the clinical application.2.99Tcm-TP1623 could concentrated in the tumor tissue with specificity in tumorbearing nude mice with high T/NT,and it indicated the combination of 99Tcm-TP1623 and tumor was mediated by HER2.99Tcm-TP1623 had showed its bright future in the field of molecular imaging in HER2 positive tumor,and it had not been reported at domestic and international. |
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