Construction Of DNAzyme Based Nanoplatform Targeting VEGF Signal Pathway For Inhibiting Metastasis Of Triple Negative Breast Cancer

As one of the most difficult subtypes of breast cancer to be cured,and the incidence of triple-negtive breast cancer has been increasing in recent years.Although surgery,chemotherapy and radiotherapy have been used to treat TNBC,they can not solve the problem of TNBC metastasis completely.It is recognized that vascular system plays an important role in tumor growth and metastasis.The rapid proliferation of tumor cells breaks the balance between angiogenic factors and anti-vascular factors,and causes a surge in the tumor-promoting angiogenesis signal,resulting in the abnormality in the vasculature of tumor tissues and promoting the forming of an immunosuppressive microenvironment.The mechanism of angiogenesis is very complicated,involving a variety of angiogenic factors and signal pathways.Current studies indicate that vascular endothelial growth factor(VEGF)signal pathway plays a key role in tumor neovascularization,where VEGF binds to its specific receptor VEGFR2,thereby activating the signaling pathway in endothelial cells,promoting the invasion and migration of endothelial cells.Therefore,the anti-angiogenic treatment by targeting VEGF signaling pathway,which has become an important strategy for tumor treatment,can be used to block the formation of tumor blood vessels for cutting off the nutrient supply of tumor cells.The target drugs,which are mainly used to target at VEGF or VEGFR,are currently produced for antiangiogenesis.However,the existing studies show that single target drugs are not sufficient to completely inhibit the angiogenesis of the tumor,while simultaneous administration of multiple target drugs may lead to increased toxicity and drug resistance.Therefore,simultaneously inhibiting VEGF and VEGFR would be the most reliable strategy for tumor antiangiogenic therapy by targeting the VEGF signal pathway.In recent years,with the development of molecular biology,gene therapy has gained much attention.DNAzyme,with specific catalytic cleavage activity,is widely used in cancer research due to its characteristics of easy modification and synthesis,high stability,and low cost.In this thesis,a nanoplatform loaded with dual-target silencing DNAzyme(V-RDzs)was constructed.The rolling circle amplification technology was used to synthesize multiple DNAzyme repeating units.Then the DNAzymes were connected with the biosafety gold nanorods to block both the upstream and downstream of the VEGF/VEGFR signal pathway,thoroughly cutting off the blood vessel growth of tumors.The excellent photothermal conversion ability of gold nanorods could also assist gene therapy to achieve enhanced tumor suppression effects.Experiment results showed that Au@V-RDzsNRs+LR could effectively inhibit the expression of VEGF in tumor cells and VEGFR2 in HUVEC,inhibited the invasion and migration ability of tumor cells.The combining strategy could effectively inhibit angiogenesis,increase the killing ability of tumor cells,and activated immune cells,resulting in significant metastasis inhibition in tumor-bearing mice.Therefore,the double target DNAzyme nanoplatform based on VEGF signaling pathway constructed in this study provides a new idea for the treatment of TNBC,and provides a theoretical basis for gene therapy towards clinical treatment.