A Study On The Application And Mechanism Of Natural Polypeptides In Anti-tumor Drug Development

Natural polypeptides have a variety of biological activities,such as anti-tumor,antibacterial,anti-inflammatory,antiviral and anti-thrombotic,so they can provide important precursor molecules for drug development.Although the molecular structure of many natural polypeptides has been successfully analyzed,their molecular and cellular mechanism in vivo is still poorly understood,which seriously limits their application in clinical drug research and development.Therefore,screening and discovering natural peptides with anti-tumor activity and elucidating the corresponding molecular and cellular mechanisms can greatly promote the development of novel anti-tumor drugs based on natural peptides.In this study,we focused on the anti-tumor mechanism of the natural peptide Gymnopeptides A(GA)from mushrooms and the targeting effect of Chlorotoxin on glioma,providing important theoretical basis and technical support for the research and development of new anti-tumor drugs with natural polypeptides as lead compounds.1.The mechanism of natural mushroom polypeptides of anticancerGymnopeptide A,a natural cyclic peptide purified from the mushroom Gymnopus fusipes,inhibits the proliferation of multiple tumor cells in vitro.However,the mechanism remains unknown.We firstly obtained GA by chemical synthesis,and demonstrated that GA can significantly inhibit the growth and metastasis of various tumor cells at very low concentration in BALB/c xenograft tumor modes without producing obvious toxic and side effects.Further studies showed that GA could induce tumor cell apoptosis and inhibit tumor metastasis.Preliminary studies on the tumor inhibition mechanism of GA have shown that GA is a peptide that targets mitochondria and its most significant effect is to induce mitochondrial fragmentation.However,significant effects on the basic biological structure of mitochondria were not observed.The molecular mechanism of GA leads to mitochondrial fragmentation is that it inhibits the normal fusion between mitochondria,resulting in relatively excessive mitochondrial division.The research on mitochondrial fusion related proteins showed that GA could inhibit the splicing of OPA1 protein closely related to mitochondrial fusion,which further confirmed that GA was a novel mitochondrial fusion inhibitor at the molecular level.Targeting mitochondrial fusion/division is considered to be an effective anti-tumor strategy,but there has not been a single drug applied to the clinic so far due to the lack of low toxicity and high efficiency inhibitors.Based on the results of our study,GA,as a natural product that inhibits mitochondrial fusion,has great potential to be applied in clinical anti-tumor therapy due to its significant anti-tumor effect and extremely low toxic and side effects.2.Effect and mechanism of Chlorotoxin-derived bicyclic peptides targeting glioma.Chlorotoxin(CTX)is a cyclic peptide extracted from the scorpion venom of Leiurus quinquestriatus.A number of studies have confirmed that CTX is highly effective and specific for the targeting of glioma,and it has been successfully applied in clinical imaging diagnosis of glioma.However,the folding of CTX structure is completely dependent on the correct formation of four pairs of disulfide bonds inside CTX,resulting in a very low yield of correct synthesis in vitro.Therefore,further study of the structure-activity relationship of CTX can contribute to develop simpler and more effective drug synthesis strategies,and ultimately promote the large-scale clinical application of CTX.In this study,we established a new chemical linker to replace the disulfide bond in CTX.Based on this strategy,we synthesized 5 dicyclic peptide derivatives of CTX(P1-P5).Compared with linear CTX polypeptides,these five bicyclic derivatives showed good plasma stability close to that of natural CTX.In vitro studies showed that compared with normal nerve cells,all five CTX derivatives could be more efficiently endocytosis by glioma cells,among which P3 showed the highest uptake rate.We further tested the tumor targeting properties of the synthesized CTX derivatives using an orthotopic tumor transplantation model.The results showed that P2 and P3 had significant tumor targeting properties in vivo.The results of tissue section staining showed that both P2 and P3 could accurately target the glioma tumor tissue.These results suggest that the N-terminal sequences(P2 and P3)of CTX,but not the intermediate sequences(P4)or C-terminal sequences(P5),are the core elements that dominate the targeting of glioma cells.Subsequent studies on the targeting molecular mechanism of CTX derivatives showed that the target receptor of P3 was the same as that of natural CTX,both targeting glioma cells through the MMP2 protein on the cell surface.In conclusion,this study successfully analyzed the structure-activity relationship of CTX targeting glioma,and on this basis,a new CTX derivative that can be chemically synthesized in vitro was developed for the targeting of glioma,which is expected to be quickly introduced into the clinic to replace natural CTX in the future.3.The inhibition of natural product Romidepsin on SARS-COV2 infected cells.Using ACE2 as the target,we performed virtual screening from FDA-approved drug library,and finally proved that Romidepsin,a natural product,could effectively inhibit SARS-COV2 infected cells by pseudovirus system.