基于小肠寡肽转运蛋白PepT1提高喜树碱小肠吸收和肿瘤靶向性的研究

Camptothecin (CPT) is a naturally occurred pentacyclic indole alkaloid, enriched in Camptotheca acuminate. CPTs have gained much attention for its broad-spectrum anticancer activities. But the practical use was limited due to its poor solubility, high toxicity and unstable active site. In our previous studies, series of CPT esterification derivatives were synthesized to improve water solubility and stability, and the oral bioavailability of these compounds were also significantly higher than that of CPT, which might be related to Oligopeptide transporter 1 (PepT1) according our further studies. PepT1 plays an essential role in the oral absorption of di-and tripeptides as well as peptidomimetic drugs. Moreover, PepT1 was also highly expressed in various types of cancer cells to improve substrate delivery to the tumor site. Thus, to develop the oral alternative and tumor targeted for CPT, CPT peptidomimetic derivatives were designed and synthesized in this project. This will provide significant improvements for the therapeutic efficacy of CPTs as well as the further application of CPT drugs.

喜树碱是从我国特有植物喜树中分离得到的一种生物碱，因具有广谱抗癌活性而备受重视，但因其溶解性差、活性结构不稳定、体内易开环、不具有肿瘤靶向性而限制了应用。早期实验室基于提高水溶性和稳定内酯环的目的，合成系列喜树碱及10-甲氧基喜树碱的氨基酸酯化前药，发现这些化合物在一定程度上能够改善喜树碱的小肠吸收，进一步的研究发现这种提高小肠吸收的机制可能与小肠寡肽转运蛋白PepT1有关。PepT1是一种广泛分布于小肠上皮细胞和多种肿瘤细胞的膜转运蛋白，介导多种二肽、三肽及拟肽化合物在小肠和肿瘤细胞的吸收转运。因此，本项目拟将喜树碱与氨基酸结构相连合成以PepT1为靶点的拟肽化衍生物，能够被PepT1识别，以达到提高喜树碱小肠吸收和肿瘤靶向的目的；同时，E环的修饰也能起到稳定内酯环、降低体内毒性的作用。这对于研究喜树碱口服制剂、提高喜树碱类药物的疗效、促进喜树碱类药物的进一步开发应用具有重要意义。

喜树碱是从我国特有植物喜树中分离得到的一种生物碱，因具有广谱抗癌活性而备受重视，但因其溶解性差、活性结构不稳定、体内易开环、不具有肿瘤靶向性而限制了应用。PEPT1是一种广泛分布于小肠上皮细胞和多种肿瘤细胞的膜转运蛋白，介导多种二肽、三肽及拟肽化合物在小肠和肿瘤细胞的吸收转运。本项目旨在将喜树碱与氨基酸结构相连，合成以PEPT1为靶点的拟肽化衍生物，能够被PEPT1识别，以达到提高喜树碱小肠吸收和肿瘤靶向的目的。这对于研究喜树碱口服制剂、提高喜树碱类药物的疗效、促进喜树碱类药物的进一步开发应用具有重要意义。具体的研究结果如下：.（1）以氨基酸作为连接基团，设计合成了29种喜树碱拟肽化衍生物。分子对接模型及竞争性抑制摄取实验的结果表明，本项目合成的多数喜树碱拟肽化衍生物与PEPT1具有较强的亲和作用。.（2）利用免疫荧光与Western blot方法检测了PEPT1在多种肿瘤细胞系的表达情况，通过体外细胞毒活性实验考察了合成的喜树碱拟肽化衍生物对于高低表达PEPT1的肿瘤细胞系的抗肿瘤效果。结果表明，多数合成的喜树碱拟肽化衍生物在PEPT1高表达的肿瘤细胞系中较PEPT1低表达的肿瘤细胞系具有更强的抗肿瘤活性。.（3）综合（1）（2）的研究结果，筛选出与PEPT1亲和性较好、抗肿瘤活性较强的喜树碱拟肽化衍生物C6。建立了Caco-2小肠吸收转运模型，评价了化合物C6与喜树碱在Caco-2细胞模型中的吸收效率，结果表明，C6具有较强的吸收转效率，表明其小肠吸收优于喜树碱。