GBA-05类化合物抗肿瘤作用机理研究和基于PIN1的结构修饰

Boswellic acids have been shown to have antitumor activities and a series of compounds were designed and synthesized based on their active groups. GBA-05 is a modified derivative of boswellic acid with significantly improved antitumor effects in pancreatic cancer with degradation of cyclin D1, a key regulator of cell cycle progression. The requirement of cyclin D1 degradation by GBA-05 to inhibit cancer cell growth will be determined using cells transfected with mutant cyclin D1 defecting proteolysis. The signaling pathway of GBA-05-induced cyclin D1 down-regulation will be determined by testing inhibition of Pin1, a key enzyme stabilizing cyclin D1. Based on the crystal structure of the Pin1/EGCG complex, a series of new boswellic acids derivatives will be designed and synthesized utilizing AKBA and ATA as the lead compounds. Antiproliferative activities of these compounds will be determined in pancreatic, breast and prostate cancer cell lines. The quantitative structure-activity relationships (QSAR) of antiproliferative and inhibiting Pin1 activities of boswellic acid derivatives will be determined. Through these approaches we hope to develop a novel group of anticancer agents with a specific target.

在研究确定GBA-05和AKBA等乳香酸类等化合物具有抑制胰腺癌细胞系生长活性的基础上，进行深入的作用机理研究。以转染cyclin D1(T286A)的AsPC-1细胞为研究对象，考察降解cyclin D1水平与这类化合物抑制胰腺癌细胞生长的关系；研究GBA-05等化合物通过降解cyclin D1抑制胰腺癌细胞生长的具体通路；探讨抑制Pin1活性与降解cyclin D1之间的关系。开展基于Pin1结构的化合物设计，对天然乳香酸类化合物AKBA和ATA进行系统的结构修饰和改造，扩展化学结构上的多样性；进行体外抗肿瘤细胞增殖活性筛选和Pin1抑制试验，探讨结构和活性之间的关系。寻找具有特异性抑制Pin1、降解cyclin D1的抗肿瘤活性化合物，为自主创制新药奠定基础。

Pin1是一种肽基脯酰氨顺反同分异构酶，可以在一个亚型蛋白的两种完全不同的构象间催化其特定的磷酸化位点的转变，在致癌信号传导通路中发挥着不可缺少的翻译和放大作用。Pin1可以直接靶向于cyclin D1的p-Thr286-pro位点，稳定cyclin D1。研究发现Pin1小分子抑制剂，可能有效地降低cyclin D1的水平从而抑制肿瘤细胞生长。本研究发现GBA-05、GBA-15和GBA-20 等乳香酸类化合物通过不同的作用机制发挥抑制肿瘤细胞增殖作用，GBA-15通过抑制Pin1的活性，降低Cyclin D1的表达，从而使胰腺癌细胞AsPC-1细胞发生G1期周期阻滞，化合物GBA-05和 GBA-20不仅能够通过抑制Pin1引起细胞周期阻滞，还可以通过内源性和外源性凋亡途径诱导AsPC-1细胞发生凋亡；GBA-05在低浓度可以浓度依赖性的上调p21蛋白，下调Cyclin D1蛋白的表达，引起PC-3的细胞周期阻滞，在高浓度时通过上调促凋亡蛋白NOXA的表达水平，诱导PC-3肿瘤细胞凋亡。对AKBA和EA两种乳香酸类化合物进行基于Pin1的结构修饰，设计和合成65个结构类似物，并进行抑制Pin1活性和抑制AsPC-1、PC-3和LNCaP细胞增殖活性筛选，发现LBA-09、LBA-28、LEA-16和LEA-28等活性化合物。初步体内活性研究结果，GBA-05对小鼠Lewis肺癌模型和人乳腺癌MDA-MB-231裸鼠肿瘤模型表现出一定的活性。研究发现活性化合物抑制Pin1活性与生长抑制活性之间的相关性差，Pin1是否为重要的抗肿瘤特异性靶点尚待深入研究。.