Mechanism And Application Of Polymer Bonded Nano Drugs In Regulating Immune Microenvironment And Enhancing Tumor Therapy

Polymer drug conjugates(PDCs),also known as polymer bonded drugs,is a drug delivery system,which can attach one or more drugs directly or indirectly to the functional groups of polymers and dissociate under certain conditions,such as the change of p H value,the presence of esterase,dextranase or ROS,etc.Exposure to specific enzymes or the change of p H value after cell uptake leads to selective drug release at specific sites.Cancer is the second leading cause of human death.There are a variety of drugs for tumor treatment,among which chemotherapy is one of the most effective means to treat cancer,especially for metastatic and small invisible tumors.However,traditional small molecule therapeutic drugs,including some chemotherapeutic drugs,have some problems,such as short circulation time,large toxic and side effects,low bioavailability,poor selectivity and easy to produce multidrug resistance.On the contrary,nanomedicines have the advantages of long circulation time,more targeting and reducing systemic toxic and side effects.There are many differences between tumor microenvironment and normal tissues,such as the increased expression of reactive oxygen species(ROS);The value of p H is acidic and decreases;The expression level of hypoxia factor in tumor tissue increased.Based on the characteristics of solid tumor microenvironment,especially the host reaction produced by the tumor itself,the regulation of tumor immune microenvironment and the regulation of inflammation to promote tumor development,this paper designs stimulus responsive polymer-drug conjugates to enrich and trigger release at the tumor tissue,avoid the release caused by the drug in the process of circulation,reduce the toxicity and side effects of the whole body and realize efficient drug loading,improve the potency of drugs.The released or activated drugs can kill the tumor cells or regulate the tumor microenvironment,further activate the immune system in the body,and then use the host immune response mechanism generated by the body to attack and kill tumor cells.At the same time,this paper also explores the effect of combined use with different anti-tumor related drugs,hoping to solve a variety of problems in tumor treatment.The research content and main conclusions of this paper are as follows:(1)p H-responsive polymer-bonded nanodrug cisplatin nanoparticles(CDDP-NPs)were prepared by using poly(L-glutamic acid)-graft-methoxy poly(ethylene glycol)as carrier to support cisplatin.Based on the "EPR" effect of nanoparticles,CDDP-NPs has stronger tumor enrichment,lower systemic toxicity and longer circulation time in vivo.RNA-Seq was used to compare the differences of host immune responses induced by CDDP-NPs and CDDP in tumor-bearing mice.Compared with CDDP,CDDP-NPs significantly enhanced the invasion and activity of intratumor CD8+ T cells by promoting tumor antigen presentation and TCR pathway.Meanwhile,the expression of Cd8 a m RNA and Cd8b1 m RNA in different groups was analyzed.The results showed that the relative expression levels of Cd8 a in PBS group,CDDP group and CDDP-NPS group were 4.3,4,6.5,and the relative expression levels of Cd8b1 were 3.7,3.6,and 6.4,respectively.Single sample gene set enrichment analysis(ss GSEA)predicted CD8+ T cell activity of PBS,CDDP and CDDP-NPs groups to be 0.4,0.2 and 0.9,respectively.In addition,a OX40,a member of the tumor necrosis factor receptor superfamily 4(OX40)excitatory antibody,was highly expressed on activated T cells,and the percentage of OX40+ T cells in tumor-bearing mice treated with PBS,CDDP and CDDP-NPS was 0.3%,0.5% and 1.7%,respectively,indicating that compared with other treatment groups,The CDDP-NPs treatment group promoted the amplification of OX40+ T cells,and the combined tumor inhibition effect of cisplatin and a OX40 was verified in LLC animal model and B16F10 animal model(tumor inhibition rates were 89.2% and 92.1%,respectively;Q values were 1.4 and1.16,respectively.Synergies).This is the first study to demonstrate the superior host immune response of a cisplatin-based nanodrug and its synergistic effect with antitumor immune-therapy.(2)Dextran,is a polysaccharide composed of glucose as monosaccharide,and its repeating units are connected by glycosidic bonds.Glucoside bonds can be divided into ? and ? types,among which ?-glucan has been widely used as X carrier materials for anti-tumor drugs due to its good biocompatibility,degradability and easy functionalization of side chain groups.Glycyrrhizin(GL)is the bioactive component of glycyrrhizin glycyrrhizin.GL is metabolized into glycyrrhizin(GA)in vivo.In order to solve the problem of low bioavailability of GL,an enzyme responsive polymer bonded nano drug for the treatment of liver cancer,DEX-CBX(CBX,a GA derivative)nano drug was developed.Through oral administration,specific metabolic enzymes in the intestine(such as dextranase in the colon)were used to control the release of drugs.In the presence of enzymes and esterase,DEX-CBX releases GA,which is then transferred to the liver via the enterohepatic axis.Biological distribution results confirmed that DEX-CBX could reach the colon 4 hours after oral administration and remain there for more than 24 hours.In addition,quantitative analysis of GA biological distribution showed that oral DEX-CBX significantly increased the content of GA in liver compared with oral free GL.Therefore,DEX-CBX had a stronger tumor inhibition effect than GL in the mouse H22 tumor model(tumor inhibition rate: 85.4% vs 53.3 %).At the same time,further analysis of the host immune microenvironment showed that DEX-CBX mainly treated liver cancer by improving the immune microenvironment.Flow cytometry detected fewer M2 tumor-associated macrophages and bone marrow derived inhibitory cells(MDSCs),more NKT cells and CD8+ T cells.NKT cells in particular function through tumor-associated cytokines in the liver and have been shown to be the main cell type for liver protection and anti-tumor immunity.This study illustrates a promising strategy for high-efficiency immunotherapy using specific metabolic enzymes of intestinal microbe to activate nanomedicine and to deliver immunomodulators to liver tissues along the gut-liver axis.(3)Aspirin,a nonsteroidal anti-inflammatory drug,has been shown to prevent cancer in small doses.Targeted therapy for tumor-promoting inflammation has become one of the important means to prevent and treat cancer.Using carrier technology to regulate the absorption pathway of drugs in the intestinal tract to achieve targeted therapy for colon cancer may be a meaningful new way to treat colon cancer.An oral ROS responsive polymer bonded nanodrug(P3C-Asp)was constructed by combining reactive oxygen species sensitive aspirin prodrug with dextran.Oral administration of P3C-Asp has several functions: first,active dextran is a prebiotic that promotes the proliferation of beneficial bacteria;second,P3C-Asp can be enriched in colon cancer tissue due to the advantages of nanodrugs;third,the design of sensitive connectives can simultaneously consume ROS and release Aspirin,thus synergistic anti-inflammatory,improve the microenvironment of colon cancer,and achieve the therapeutic goal.P3C-Asp alone can effectively regulate the tumor microenvironment and intestinal microbiota in colon tumor tissue in situ,which is characterized by decreased levels of regulatory T cells,M2 macrophages and MDSCs,and increased infiltration of CD8+ T cells;Consistent with the changes of immune cells,after oral administration of P3C-Asp,T cell subgroup 1(Th1)cytokine interferon-?(IFN-?),the content of Th2 cytokines PGE2,CXCL12 and CXCL8 decreased significantly.In addition,the combined treatment with P3C-Asp and ?PD-L1 can prolong the survival time of mice with in-situ colon cancer.According to this paper,we based on the host reaction produced by the tumor itself,the regulation of tumor immune microenvironment and the regulation of inflammation to promote tumor development,and taking polyamino acid or dextran as nano carrier materials,three different stimulus responsive polymer bonded nano drugs were designed to verify the therapeutic effect and mechanism of polymer bonded nano drugs on tumor.By further studying the host changes caused by treatment,and designing the treatment scheme and combined treatment strategy according to the host changes,we can realize the regulation of polymer bonded nano drugs on the tumor host response,so as to achieve the purpose of better treatment of tumor.