Basic Research On The Application Of Photodynamic Therapy For Hypoxic Solid Tumors

Cancer is seriously threated human health.Therefore,it is of great significance to seek methods and drugs for effective treatment of cancer.Solid tumors have a unique abnormal blood supply system that presents insufficient oxygen and nutrient supply.Photodynamic therapy(PDT)is a new type for cancer treatment.Reactive oxygen species(ROSs)is generated from photosensitizer(PS)actived by light under the participation of O2,and induces tumor cell damage/death.PDT has the characteristics of low drug resistance and limited side effects compared with traditional tumor treatment methods.Due to rapid growth and abnormal blood supply system and metabolism,tumor microenvironment(TME)presents high expression of hypoxia,hyperacidity,hydrogen peroxide(H2O2)and glutathione(GSH).Some TME characteristics(such as hypoxia and high expression of GSH with antioxidant capacity)significantly reduce PDT efficacy.Therefore,in the design of PDT drugs,the characteristics of solid tumor microenvironment must be combined to overcome adverse factors to achieve the goal of efficient anti-tumor.To achieve efficient PDT treatment for solid tumors,the following research was conducted in this paper:1.Screening and optimization of ZnPc with H2O2-burst capabilityCatalyzing the endogenous hydrogen peroxide(H2O2)of tumor cells to produce oxygen and enrich O2 in hypoxic tumors is one of the most widely used strategies for solving hypoxia in solid tumors.However,the concentration of H2O2 in tumor cells is limited(less than 50 ?M),and with varies huge difference due to the type of tumor cells,so,it is difficult to achieve an effective increase O2 in the hypoxia tumor by catalysis endogenous H2O2.The previous study of our research group,we found that tumor cell will generate abundant H2O2 after photosensitivity damaged and killed by zinc phthalocyanin(ZnPc)modified with specific structure,which means that tumor cells would gradually produce a large amount of H2O2 in the process of apoptosis.We found that ZnPc modified with carboxyl is best candidate for our goal.Therefore,we design and systheis ZnPcs modified with different numbers of carboxyl,and the optimization results show that 2,3,9,10,16,17,23,24-octa-(3,5-two dicarboxylic acid phenoxy)zinc phthalocyanine(hexadecarboxylate zinc phthalocyanine,ZnPc 12)not only has ideal photosensitivity and antitumor activity,but also has an efficient H2O2 burst effect.What's more,ZnPc 12 induced H2O2 burst effect was detected in various tumor cell lines,indicating that this effect has a broad spectrum.The mechanism of ZnPc12 induced H2O2 outbreaks was discussed.Preliminary results showed that there were two sources of H2O2,one was the direct production of H2O2 by photosensitized ZnPc12 via Type ? pathway,the other was the activation of two endogenous H2O2 production pathways(mitochondrial respiratory chain and NADPH oxidase)after PDT damage,which induced cells to further produce large amounts of H2O2.2.ZnPc&CAT@CaP oxygen-self-produced nano-system for enhanced hypoxia photodynamic therapyIn order to utilize the explosive effect of hydrogen peroxide induced by ZnPc12 to catalyze oxygen production,alleviate hypoxia in solid tumors and improve the curative effect of PDT,nano-calcium phosphate(CaP)was selected to transport ZnPcl2 and catalase(CAT)with high catalytic activity of hydrogen peroxide to tumors simultaneously.CaP has good biocompatibility and is characterized by acid pH induced dissolution and release.In this chapter,nano-drug(ZCCN)containing ZnPc12 and CAT with the size of about 100 nm was obtained by coprecipitation.In vitro studies have shown that ZCCN can catalyze oxygen production and alleviate hypoxia in tumor cells by using ZnPc12-induced H2O2 burst effect(using three-gas incubator to construct hypoxic environment artificially)and improve the efficacy of PDT.The cell survival rate of ZCCN treated cells was only 25.31%,ZnPc12 and ZnPc12@CaP damaged cells was more than 50%.In vivo antitumor experiments showed that compared with ZnPc,ZCCN inhibited tumor markedly.3.A H-Fe3O4C@ZnPc@PEG oxygen-self-produced PDT system with deep tumor penetration abilityThe transmission efficiency of nano drugs and the penetration properties of solid tumors are closely related to their size.It has been reported in the literature that the half-life of blood transported by nano-drugs with too small size is shorter,but the permeation effect of nano-drugs with too large size is poor in the tight cell space of solid tumors.Histidine-modified nano-Fe3O4(H-Fe3O4)is a kind of nano-enzyme with good catalytic activity for hydrogen peroxide production.In addition,it has the functions of magnetic targeting and magnetic resonance imaging.Ultra small size H-Fe3O4 nanoparticles were prepared by hydrothermal method,and they were aggregated into large size particles in water.ZnPc12 nanoparticles coated with H-Fe3O4 and coated with polyethylene glycol(PEG)were used to obtain HFZP nanoparticles.TEM,particle size analysis and simulated enzyme catalytic experiments show that HFZP(about 183.6 nm in diameter)has the ability to catalyze the formation of oxygen from hydrogen peroxide,and rapidly decomposes into ultrasmall particles(about 8.8 nm in diameter)driven by hydrogen peroxide.The results of 3D cell sphere experiment showed that HFZP could penetrate into the deep part of the cell sphere better in the presence of H2O2.The experimental results of fluorescence imaging and magnetic resonance imaging in small animals show that magnetic field can significantly enhance the enrichment of HFZP in tumor tissues.In addition,in vitro and in vivo experiments showed that H-Fe3O4 could catalyze oxygen production,alleviate hypoxia of solid tumors and improve the efficacy of PDT by using the explosive effect of H2O2 induced by ZnPc12.4.Enhance the therapeutic effect of hypoxia photodynamic therapy by educing the antioxidant capacity of cellsAs one of the most important antioxidants in cells,GSH concentration in tumor cells is up to 10 mM,which can consume ROS produced during PDT and significantly reduce the efficacy of PDT.The GSH synthesis pathway is the two continuous reaction depending on ATP.Reducing ATP content will inevitably affect the synthesis of GSH in tumor cells and destroy the antioxidant capacity of cells,thus enhancing the sensitivity of tumor cells to PDT treatment and improving the therapeutic effect of PDT under hypoxic conditions.In addition,the decrease of ATP concentration also affects the normal physiological functions of cancer cells(such as nucleic acid replication),thus synergistically inhibiting tumors.Based on the above principles,a novel nanoparticle(ZPCN)composed of CuU+and carboxyl-modified zinc phthalocyanine(ZPCN)was designed and synthesized to enhance the PDT effect in hypoxic environment by reducing the antioxidant capacity of tumor cells.The results showed that after ZPCN was uptake by tumor cells,intracellular ATP could deprive Cu2+ of ZPCN to form Cu-ATP complex and release ZnPc.Copper-mediated Fenton reaction can destroy ATP in the copper-ATP complex.ATP depletion can affect GSH synthesis in cells,enhance the sensitivity of tumor cells to PDT therapy,and achieve efficient treatment of hypoxic tumor PDT.