Studies Of The Anti-glioma Efficacy And Preliminary Mechanism Of Action Of Sea Cucumber Saponin Prepared From Holothuria Moebii And Tripolinolate A

Glioma is the most common and high mortality brain tumor.Because glioma invasively grows and usually locates at important brain function areas,which make surgical resection extremely difficult.Therefore,chemotherapy has played a more important role in the treatment and prevention of glioma.Currently,temozolomide is the only first-line drug recommended for glioma treatment and there is an urgent need to develop new drugs for the treatment of gliomas.Natural products,especially marine natural products,are important sources of novel anti-tumor lead compounds.Sea cucumber saponins from Holothuria moebii and tripolinolate A(TLA)from a beach halophyte Tripolium vulgare are two different types of compounds,which were proved to have anti-glioma activity recently.This thesis was to investigate the anti-glioma efficacy and preliminary mechanism of action of sea cucumber saponins and TLA.The investigation included four specific aims:(1)to determine the activities of total saponins(SPT)and its four monomeric saponins SP1-SP4 and TLA against the proliferation of different glioma cells by sulforhodamine B(SRB)assay;(2)to analyze the effects of SPT and its main component SP3 and TLA on apoptosis and cell cycle in glioma cells by flow cytometry analysis using Annexin V-FITC/PI double staining and PI staining,respectively;(3)to detect the effects of SPT,SP3 and TLA on the expression levels of apoptotic proteins,cell cycle proteins,key enzymes in different metabolic pathways,and transcription factors that were related to the tumor metabolism by western blot analysis;(4)to evaluate the in vivo anti-glioma effects of SPT and TLA in the animal model of glioma U87MG cell xenografts nude mice.The results from this study demonstrated that:(1)both sea cucumber saponins and TLA had significant inhibitory activity against the proliferation of different glioma cells;(2)both sea cucumber saponins and TLA induced apoptosis in glioma cells by downregulating the expressions of anti-apoptotic proteins Bcl-2,Mcl-1,and survivin;(3)both sea cucumber saponins and TLA significantly reduced the expression levels of the cell cycle regulators of cyclin A,cyclin D1,CDK4,CDK6,and p-Rb and blocked the cell cycle at S phase and G2/M phase in glioma cells,respectively;(4)both sea cucumber saponins and TLA showed a unique anti-tumor mechanism by significantly downregulating the expression levels of key enzymes and transcription factors in different metabolic pathways of glioma cells;(5)SPT and TLA showed significant anti-glioma effects in the U87MG cell xenograft nude mice.All data from this study provided a scientific basis for the further study of the anti-glioma efficacy,full mechanism of action,and potential applications of sea cucumber saponins and TLA.