Combined Temozolomide With PD-1 Antibody Therapy For Mice With Glioma In Situ

Purpose:Glioma is the most common primary brain tumor in adults,and temozolomide is the most frequent chemotherapy drugs.Currently immunotherapy is a promising treatment,such as programmed-death-1(PD-1)and its ligands PDL1 play critical roles in tumor immune suppression.PDL1 was expressed on a variety of tumors,including glioma.Tumors which highly PDL1 expression were significantly correlated with tumor suppressive immune response and poor prognosis.This study was to evaluate potential for anti-PD-1 immunotherapy combined with temozolomide in a mouse GL261 orthotopi glioma model.Methods and Materials:We performed stereotactic intracranial implantation of mouse glioma cell line GL261 into C57BL/6 mice,mice were divided into four groups randomly using the randomized block design method:1)control group;2)temozolomide group;3)anti-PD-1 antibody group;4)temozolomide combined with anti-PD-1 antibody group.The dose of anti-PD-1 antibody was 200ug each time,and the dose of temozolomide was 50ug/kg.The combined treatment group were treated with the same dose of PD 1 and temozolomide.The control group was given the same dose of terile saline.Using 7.0 T MRI and immunohistochemical to assess the volume of glioma and using immunohistochemical to evaluate the amount of CD4 and CD8 infiltrating cells in brain tumor and spleen of mice.Then western blot and spectrophotometric method were used to evaluate the expression of PDL1 and the apoptosis.Furthermore,Overall survival of each group mice was also evaluated.Results:Overall survival was significantly improved in combined group(anti-PD-1 therapy&temozolomide)compared with single therapy group(?2 = 32.043,P<0.01).The area of tumor was significantly decreased in combined group compared with other groups(the combined group:0.69±0.11mm2,the control group:11.40±2.36mm2,F=42.771,P<0.01).And the amount of CD4+T and CD8+T infiltrating cells in brain tumor were also obviously increased in combined group(the amount of CD4+T and CD8+T in the combined group were 533±87.68/mm2 and 273±14.14/mm2 respectively,the control group were 133.5±28.99/mm2 and 41.5±12.02/mm2 respectively(CD4+T cells F=45.67,P<0.01;CD8+T cells F=53.75,P<0.01).Conclusions:PD1 antibody combined with temozolomide therapy could significantly improve the survival time in mice with orthotopic glioma.Thus,this study provides effective preclinical evidence to support clinical chemotherapy combined with immunotherapy for glioma patients.