靶向肽结合131I-PAMAM(G5.0) 抑制甲状腺髓样癌细胞增殖的研究

目的研究131I标记靶向肽丝氨酸-精氨酸-谷氨酸-丝氨酸-脯氨酸-组氮酸-脯氨酸（SRESPHP）（简称SR）修饰的第五代聚酰胺-胺（PAMAM（G5.0））的体外性质及其作为甲状腺髓样癌细胞靶向探针的可行性。方法用氯胺T法进行PAMAM（G5.0）-SR和PAMAM（G5.0）的131I标记，通过薄层层析法分别测定所制备的两种探针的标记率及稳定性，并考察131I标记物的脂水分配系数；通过阻断摄取实验分别考察两种探针的靶向性；计算两种探针对细胞的半数致死剂量并分析其对细胞生长的影响。采用GraphPad Prism 5.01分析软件对符合正态分布及方差齐性的数据进行样本t检验。结果 131I-PAMAM（G5.0）-SR和131I-PAMAM（G5.0）的标记率均大于70%，纯化后的放化纯度均大于90%。两种探针在体外PBS体系中的稳定性好，且均显示出良好的水溶性。细胞阻断实验结果显示，加入PAMAM（G5.0）-SR阻断的131I-PAMAM（G5.0）-SR细胞摄取率明显降低，差异均有统计学意义（t=7.315、22.590和22.570，均P < 0.01），提示131I-PAMAM（G5.0）-SR对细胞具有较好的靶向性。131I-PAMAM（G5.0）-SR的细胞半数致死剂量为513.6 kBq/mL。细胞摄取实验结果显示，随着时间的延迟，细胞对半数致死剂量下的131I-PAMAM（G5.0）-SR的摄取逐渐降低，但在48 h细胞摄取出现上升的现象，随后细胞摄取再次下降。结论 131I-PAMAM（G5.0）-SR具有良好的生物学性质，可靶向甲状腺髓样癌细胞并抑制细胞增殖。

Effects of targeted peptide-conjugated 131I-PAMAM (G5.0) on the inhibition of medullary thyroid carcinoma cells proliferation

Objective To incorporate 131I into the fifth generation polyamidoamine(PAMAM (G5.0)) with the targeting peptide Ser-Arg-Glu-Ser-Pro-His-Pro(SRESPHP)(SR for short) and observe the in vitro properties for the targeting probe of medullary carcinoma cells (MTCs).Methods PAMAM (G5.0)-SR and PAMAM(G5.0) were radiolabeled with 131I by chloramine T.Labeling yield and stability were determined by thin layer chromatography.Lipid-water partition coefficients were also evaluated.The targeting of the two types of 1nI-radiotracers(1nI-PAMAM(G5.0)-SR and 131I-PAMAM(G5.0))was determined in a blocking uptake study where TF tumor cells were used.The median lethal dose of the two probes was then calculated.GraphPad Prism 5.01 analysis software was used to conduct a t-test for the data that fit the normal distribution and homogeneity of variance.Results The labeling yields of the two types of 131I radiotracers all exceeded 70％,and the radiochemical purity levels were higher than 90％ after purification.The stability of the two probes in the PBS system was satisfactory,and both probes showed excellent water solubility.The results of the blocking uptake study on the TT cells showed that the cell uptake rate decreased significantly (t=7.315,22.590,22.570,all P＜0.01) after the PAMAM (G5.0)-SR blocked the 131I-PAMAM (G5.0)-SR.This result indicated that 131I-PAMAM (G5.0)-SR achieved excellent targeting and that its median lethal dose was only 513.6 kBq/mL.The cell uptake results showed that the cell uptake rate of 131I-PAMAM (G5.0)-SR with a median lethal dose gradually decreased with time.However,cell uptake rate increased for 48 h before it decreased again.Conclusion 131I-PAMAM (G5.0)-SR can target medullary thyroid carcinoma cells and thus inhibit cell proliferation.