Designing Multifunctional Nano-prodrugs Based On Tumor Microenvironments For Reversing Tumor Multidrug Resistance

In recent years,chemotherapy has been a vital stratergy for cancer treatment,which significantly improve the survival of patients in clinical practice.However,traditional drugs chemotherapy lacks selectivity and targeting,which easily cause drugs elimination in vivo and serious side effects to the body,thus seriously limiting the chemotherapeutic effect.With the development of nanotechnology,some nano-formulations have been designed to improve the above deficiency.Although these nanomedicine have achieved some progress,few of them have been applied in clinic therapy and achieved outstanding effects.The body barriers?such as blood circulation,clearance systems,etc.?and tumor heterogeneity?dense intercellular interstitium,fluid pressure,multidrug resistance,etc.?seriously hamper the clinical transformation of nano-formulations.Among them,the occurrence of tumor resistance easily leads to chemotherapy failure or cancer recurrence.To address above problems,researchers have developed some MDR inhibitors that can be co-encapsulated or co-binded with anticancer drugs into nanosystems to overcome or circumvent tumor resistance.However,most inhibitors are inefficient in vivo,and accompanied by severely intrinsic toxicity.In addition,these nanosystem both have some shortcomings,including complex preparation process,low reproducibility,poor stability,premature release or slow release,low uptake efficiency,etc.More importantly,single MDR reversal often cause limited therapy effect,because malignant tumors involve many resistance mechanisms?such as over-expression of efflux transporters,detoxification system,acidity isolation,hypoxia,inflammatory environment?.Therefore,developing multi-effects MDR inhibitors or rationally designing multi-functional nanoformulations are very important for overcoming tumor resistance and/or improving therapy efficacy.In this paper,we designed three multifunctional nano-prodrug system based on tumor microenvironments,which may achieve better cancer treatment through multiple synergistic effects and multi-mode therapy.The idea and methods of designs,and main results were as follows:?1?PBA-targeting and pH-sensitive pluronic prodrug micelles:preparation,characterization and antitumor evaluation in vivoTwo functionalized pluronic coploymers?F127-PBA and P123-CAD?were synthesized,then self-assembled into hybrid prodrugs micelles with suitable size by thin film hydration.In vitro tests suggested that this micellar particles remained stable in physiological environment,while triggering DOX release at low pH owing to the cleavage of?-carboxylic amides bonds.A series of cells experiments showed that PBA could increase the internalization of prodrugs particles,and P123 could trigger many biological effects?mitochondrial depolarization,ATP down-regulation,ROS up-regulation,etc.?to reverse tumor MDR.In vivo experiments demonstrated that prodrug micelles could prolong blood circulation time,and high-efficiently accumulated in tumor region,thereby leading to the highest tumor growth inhibition.Besides,there were no significant system damage or body loss in prodrugs micelles-treated mice,indicating the good biosafety.As a result,this nano-prodrug system may have more advanced therapeutic effects than SP1049C?phase III?,and is expected to be further used in clinical transformation.?2?Oxygen-producing catalase-based prodrug nanoparticles for overcoming hypoxia-mediated chemo-photodynamic therapy resistanceLA and CAD were pre-modified onto the side chain of CAT by EDC/NHS system to give amphiphilic biomolecules,then co-assembled with Ce6 to form smart LCC@Ce6nanoparticles.In vivo studies showed that this prodrugs system could trigger two agents release under mildly acid environment,and the hydrophilic outer layer of particles could prevent CAT degradation that keep high catalytic activity.Cells experiments verified that LA was capable of increasing cellular uptake,then this nano-enzyme particle could decompose H₂O₂ to produce O₂ in situ,followed by preventing the degradation of HIF-1?and reducing the expression of P-gp,eventually reversing chemotherapy resistance.Besides,O₂-regeneration further induced more ROS production by above nano-system,and greatly enhanced PDT-medicated cell-killing effects.In vivo tests further indicated that this nano-system could efficiently alleviate tumor hypoxia,thereby simultaneously sensitize chemotherapy-photodynamic therapy,resulting in the best antitumor efficacy?>90%?and/or ablate part of tumor mass.All above findings demonstrated that combined treatment strategy by O₂ helping may be effective in fighting malignant cancer,and was worth further to optimization or evaluatation in vivo.?3?Self-assembled ternary hybrid nano-prodrugs particles for overcoming tumor resistance and metastasisDOX and CXB dimer by disulfide linkage,amphiphilic PEI were synthesized,then co-self-assembled into ternary hybrid multifunctional nanoparticles.At pH 6.8,the surface potential of particles had an obvious phase transition?negative to positive?and exhibited distinct proton buffering capacity.Besides,this nano-system gradually disintegrated by DTT mediated disulfide cleavage,thus triggering quickly drugs release.In vivo cell experiments revealed that the charge reversal ability of particles efficiently enhanced cells endocytosis and PEI further broke acidity isolation,and what's more,CXB remarkably reduced P-gp expression.All above regulatory measures greatly increased DOX retention and toxicity in MDR cells.In addition,this nano-sized prodrugs could also significantly inhibit cells migration/invasion,as well as blocking cell cycle in G0/G1 phase,thereby inducing more cells apoptosis.In vivo tests showed that hybrid prodrugs particles could accumulate in tumour areas by passive targeting and reduce non-specific distribution,resulting in higher drug bioavailability and weak systemic toxicity.Subcutaneous tumor evaluation showed that this multi-effect prodrug system could remarkably inhibit solid tumor growth?⁸5%?,and also exhibited the outstanding therapeutic effect on the eradication of liver and lung metastatic tumors.Therefore,the regulation of inflammatory environments in tumor region can improve chemotherapy efficacy,and this idea of multiple hybridization may be applied to the synergistic treatment of malignant tumors in clinic.