Combination of Photodynamic Therapy and Immune Checkpoint Inhibitors in Treatment of Lung Cancer:An Experimental Study
Objective To evaluate the efficacy of liposome-encapsulated dihydroporphyrin e6 photodynamic therapy(Lip@Ce6-PDT)combined with immune checkpoint inhibitor PD-L1 antibody in the treatment of Lewis lung cancer model.Methods Lip@Ce6 was synthesized with membrane evaporation method,and the encapsulation rate and drug loading rate were measured.Forty C57BL/6 Lewis lung cancer model mice were randomly divided into 5 groups:the model control group(group A),PD-L1 antibody group(group B),Lip@Ce6-PDT group(group C),Lip@Ce6-PDT+PD-L1 antibody group(group D)and normal control group(group E),8 mice in each group.PD-L1 antibody was injected intraperitoneally to the mice in group B at a dose of 100μg/mouse.For group C,fiber was introduced into the percutaneous puncture after 1h of tail vein administration,and laser irradiation was then performed inside the tumor.The mice in group D were injected intraperitoneally PD-L1 antibody after Lip@Ce6-PDT treatment.The mice in the blank control group and group A were injected with the same amount of phosphate buffered solution(PBS)once every 3 d for a total of 5 treatments.During the treatment,the tumor volume was measured every day and the tumor inhibitory rate was calculated.Three days after the end of the fifth treatment,the tumor tissue was taken for HE staining,Bax and Bcl-2 immunohistochemistry.Immunofluorescence was used to detect the infiltration of CD4+T cells,CD8+T cells and Foxp3 in tumor tissues,and real-time polymerase chain reaction(RT-PCR)was used to detect the expression of PD-1 and PD-L1 mRNA.The experimental results were analyzed.Results(1)The particle size of Lip@Ce6 was about 103.2 nm and the dispersibility and stability were good.The encapsulation rate of Ce6 was 68.3％,and the drug loading rate was 8.2％.(2)The anti-tumor effect of Lip@Ce6-PDT mediated PDT therapy combined with PD-L1 antibody on mice and the effect on the immune microenvironment.The tumor inhibition rates of group B,C and D were 25.1％,55.4％and 68.3％respectively.(3)The results of HE staining showed that,compared with group A,the degree of tumor cell necrosis in group B,group C and group D increased in turn.(4)The positive expression rate of Bcl-2 of the groups climbed in the following order:group D,group C,group B and group A.The positive expression rate of Bax of the groups climbed in the following order:group A,group B,group C and group D.(5)The immunofluorescence results showed that,compared with those of group A,the expression levels of CD4+T cells and CD8+T cells in groups B,C and D successively increased,and the expression levels of Foxp3 successively decreased.(6)The RT-PCR test results showed that,compared with those of group A,the mRNA expression levels of PD-1 and PD-L1 in tumor tissues of group C after treatment increased relatively.Conclusions Lip@Ce6 mediated PDT and immune checkpoint inhibitors have significant combined therapeutic effect on Lewis lung cancer model,and will effectively inhibit tumor cell growth.
Photodynamic therapyImmune checkpoint inhibitorsCombination therapyLung cancer
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