Two Chitotriose-Specific Lectins Show Anti-Angiogenesis, Induces Caspase-9-Mediated Apoptosis and Early Arrest of Pancreatic Tumor Cell Cycle

The antiproliferative activity of two chito- specific agglutinins purified from Benincasa hispida (BhL) and Datura innoxia (DiL9) of different plant family origin was investigated on various cancer cell lines. Both lectins showed chitotriose specificity, by inhibiting lectin hemagglutinating activity. On further studies, it was revealed that these agglutinins caused remarkable concentration-dependent antiproliferative effect on human pancreatic cancerous cells but not on the normal human umbilical vein endothelial cells even at higher doses determined using MTT assay. The GI50 values were approximately 8.4 μg ml-1 (0.247 μM) and 142 μg ml-1(14.8 μM) for BhL and DiL9, respectively, against PANC-1 cells. The growth inhibitory effect of these lectins on pancreatic cancer cells were shown to be a consequence of lectin cell surface binding and triggering G0/G1 arrest, mitochondrial membrane depolarization, sustained increase of the intracellular calcium release and the apoptotic signal is amplified by activation of caspases executing cell death. Interestingly, these lectins also showed anti-angiogenic activity by disrupting the endothelial tubulogenesis. Therefore, we report for the first time two chito-specific lectins specifically binding to tumor glycans; they can be considered to be a class of molecules with antitumor activity against pancreatic cancer cells mediated through caspase dependent mitochondrial apoptotic pathway.

本研究针对两种分别源自不同植物科的冬瓜（Benincasa hispida，BhL）与曼陀罗（Datura innoxia，DiL9）纯化得到的几丁质特异性凝集素（chito-specific agglutinins），在多种癌细胞系中的抗增殖活性展开了探究。两种凝集素均表现出几丁三糖（chitotriose）结合特异性，通过几丁三糖可抑制其血凝活性。进一步研究显示，经MTT比色法（MTT assay）检测结果表明，此类凝集素对人胰腺癌细胞具有显著的浓度依赖性抗增殖效应，但即便在较高剂量下，对正常人脐静脉内皮细胞亦无此类作用。针对PANC-1细胞，BhL与DiL9的生长抑制半数浓度（GI50）分别约为8.4 μg·ml⁻¹（0.247 μM）与142 μg·ml⁻¹（14.8 μM）。研究证实，此类凝集素对胰腺癌细胞的生长抑制效应，源于其与细胞表面结合后触发的一系列事件：细胞周期G0/G1期阻滞、线粒体膜去极化、细胞内钙释放持续升高，同时通过激活半胱天冬酶（caspases）放大凋亡信号，最终执行细胞死亡程序。值得注意的是，此类凝集素还可通过破坏内皮管形成过程，发挥抗血管生成活性。综上，本研究首次报道了两种可特异性结合肿瘤糖链的几丁质特异性凝集素；它们可被视为一类通过半胱天冬酶依赖性线粒体凋亡通路，发挥抗胰腺癌细胞肿瘤活性的分子。