Design And Antitumor Study Of Photo-immunotherapy Platform Via Self-assembled Nanoparticles Based On IDO Inhibitor

Cancer is one of the serious threats to human health worldwide.The conventional therapeutic methods almost all fail to inhibit tumor metastasis and recurrence,which are two huge challenges in tumor treatment and urgently needed to be solved.It has been confirmed that the supression of immune system is closely related to the currence of tumor.Therefore,cancer immunotherapy,attacking tumors by stimulating immune system,has attracted more and more attention recently.Immunotherapy could inhibit tumor metastasis and recurrence due to its systemic anti-tumor immune response and increasing memory T cells.Indoleamine 2,3-dioxygenase(IDO),an intracellular enzyme overexpressed in tumors,could catalyze the degradation of tryptophan(Trp)into kynurenine(Kyn).Depletion of Trp could cause anergy or apoptosis of T cells,and Kyn accumulation leads to the differentiation from naive CD4+T cells to regulatory T cells(Tregs),resulting in immunosuppressive tumor microenvironment.The IDO inhibitor 1-methyl-tryptophan(1MT)could convert the immunosuppressive tumor microenvironment.However,its clinical application is hindered by deficient potency,poor water solubility,inadequate target and various side effects to normal tissues.Photothermal therapy(PTT),killing tumors via heat by employing near-infrared(NIR)light to irradiate photothermal agent,has become an attractive strategy to cancer treatment.Moreover,as one of the therapeutics which could cause immunogenic cell death(ICD),PTT not only kill tumors directly but also bring about tumor-associated antigens(TAAs)and damaged-associated molecular patterns(DAMPs)to activate immune response.New indocyanine green(IR820),an organic photothermal agent,shows superior biological safety and high photothermal conversion efficiency.However,it has shortcomings such as short lifetime in vivo and absence of tumor-targeting ability.Based on this,we for the first time combined PTT and IDO inhibitor in a carrier-free,all-role-in-one molecule nanoplatform via self-assembled nanoscale system of amphiphilic small moleculeHerein,hydrophilic photothermal agent IR820 and hydrophobic IDO inhibitor 1MT were employed to synthesize IR820-1MT via pH-and enzyme-sensitive ester bond.And then IR820-1MT could self-assemble into nanoparticles with high dual-therapeutic agent loading of 88.8%.The shortcomings of IR820 and 1MT have been solved in the nanoplatform.The TEM image demonstrated that the nanoparticles were spherical and the DLS measurement indicated that the average diameter of the nanoparticles was about 105.7 nm.The in vitro release behavior of 1MT was investigated by dialysis method,and the results indicated that the drug release had the pH and enzyme-sensitive property.The in vitro temperature-increasing results showed the excellent properties of IR820-1MT nanoparticles in PTT.The B16F10 cells were selected as tumor cell models to study the cytotoxicity of the nanoparticles.The cellular uptake experiments and in vitro cytotoxicity experiments showed that IR820-1MT nanoparticles had higher cellular uptake rate and cytotoxicity than that of free drugs.The up-regulation of heat shock protein 70(HSP70)and exposure of calreticulin(CRT)proved the ICD induced by IR820-1MT nanoparticles.What's more,DCs maturation,T-cells proliferation and apoptosis analysis experiments indicated IR820-1MT nanoparticles could trigger immune response in vitro.B16F10 cells and female C57BL/6 mice were used to study in vivo anti-tumor effects.The results showed that the IR820-1MT nanoparticles could kill tumors directly by PTT and convert the "cold" immunosuppressive tumor microenvironment to the "hot"immunogenic tumor microenvironment by the combination of ICD and IDO inhibitation.The laser-triggered IR820-1MT nanoparticles remarkably enhanced accumulation of cytotoxic T cells(CTLs),helper T cells(Ths),memory T cells and simultaneously suppressed proportion of Tregs,resulting in excellent systemic anti-tumor immune response.Therefore,the IR820-1MT nanoparticles exhibited remarkably high efficacy toward inhibiting tumor growth,metastasis and recurrence To demonstrate the versatility of IR820-1MT nanoplatform applied as itself or in combination with other immunotherapy strategy,post-injected programmed death-ligand 1 antibody(?PD-L1)was further combined with IR820-1MT nanoparticles,resulting in excellent anti-tumor effect.Therefore,the amphiphilic molecular engineering strategy provides a promising alternative option for design of photo-immunotherapy against tumor growth,metastasis and recurrence.