Synthesis And Performance Evaluation Of Ethisterone Based Radiopharmaceuticals For Breast Cancer Progesterone Receptor Targeting

Studies have shown that the loss of progesterone receptor(PR)expression in breast cancer is closely related to the high invasiveness and worse prognosis of tumors.Therefore,the construction of molecular probes targeting PR and the application of molecular imaging technology in early diagnosis and prognosis assessment of breast cancer are of great significance.In this thesis,ethisterone based radioprobes were designed and synthesized as potential breast cancer imaging agents via PR targeting.The main contents are summarized as follows:First,ethisterone was used as the targeted pharmacophor of PR,and its ethinyl group was coupled with azide modified PEG-OTs by click chemistry.Then[18F]FPTT was synthesized by one-step nucleophilic substitution reaction which the PEG terminal was labeled with 18F.The experimental results showed that the radiochemical yield of[18F]FPTT was 86%,the radiochemical purity was>98%,the specific activity was 16.65 GBq/?moL and good stability in vitro.The results of PET imaging showed that[18F]FPTT uptake in PR positive MCF-7 tumors(3.9±0.20%ID/g)was significantly higher than that in PR negative MDA-MB-231 tumors(1.3±0.11%ID/g)and could be specifically inhibited by excessive unlabeled progesterone(1.3±0.08%ID/g).A series of in vivo and in vitro biological evaluation of[18F]FPTT have verified the targeting ability of PR,and will be further applied to the diagnosis of PR-positive breast cancer.Then considering that PR was mainly located in the nucleus,the uptake of tumor could be enhanced by improving nucleus uptake ability of probes.We have successfully prepared 131I-labled ethisterone derivatives,[131I]EIPBA,which acetylene progesterone was conjugated with pegylated phenylboronic acid via click reaction and radiolabeled with 131I.Meanwhile,[131I]EIPB without boronate was prepared as control agent.After determining the physicochemical properties of the tracers,in vitro cell study and in vivo biodistribution experiments were carried out to verify that[131I]EIPBA enhanced nuclear uptake and PR targeting ability.The experimental results showed that the radiochemical yields of[131I]EIPBA and[131I]EIPB were 40.35%and 45.12%,respectively.Both of the[131I]EIPBA and[131I]EIPB displayed good stability in saline,but the stability in rat serum at 37 ? of[131I]EIPB was only 83%.Cell saturation assay showed that[131I]EIPBA had a high specific affinity with PR(Ka=39.58±3.47 nM),significantly higher than[131I]EIPB(Ka=46.83±5.21 nM).Cell internalization and nucleus uptake studies showed that the internalization rates of[131I]EIPBA and[131I]EIPB at 5 minutes of incubation were(0.64 ± 0.01%)and(0.04 ± 0.01%),respectively.Aromatic boronate motif can effectively increase the internalization rate by about 16 times.Obviously higher internalization of 131I-EIPBA than that of[131I]EIPB were observed at each subsequent time point of incubation.Nucleus uptake of[131I]EIPBA in MCF-7 cells was calculated as(0.59±0.02%),obviously higher than that of[131I]EIPB(0.13±0.01%).It is shown that the aromatic boronate motif can effectively improve nucleus targetingFinaly,in this study,two types of PR targeted probes were developed for the accurate typing of early breast cancer called[18F]FPTT and[131I]EIPBA.[18F]FPTT prepared by one-step simple and rapid labeling has high radiochemical yield and specific activity,and shows good PR targeting ability cell experiments and PET imaging,which is expected to become a new molecular probe targeting PR imaging.[131I]EIPBA has specific cell uptake and high PR binding affinity.Compared with the control compound[131I]EIPB without aromatic boronate motif,[131I]EIPBA has significantly enhanced nuclear accumulation.The ability and specificity of tumor uptake will be further evaluated and the scope of research will be expanded to provide a broader new strategy for targeted modification of other nuclear receptor drug molecules.