Endosialin Positive Tumor Derived Pericytes Promote Tumor Progression Through Impeding The Infiltration Of CD8~+ T Cells In Clear Cell Renal Cell Carcinoma

Background:Immune checkpoint inhibitor（ICI）therapy can effectively treat clear cell renal cell carcinoma（cc RCC）,but more than 50%of patients with renal cell carcinoma will develop initial or secondary resistance.Tumor-derived pericytes（TDPs）may promote tumor progression by inhibiting tumor infiltration and killing activity of T cells.They are an important part of the inhibitory immune microenvironment and an ideal target for immunotherapy.However,TDPs are a highly heterogeneous population of cells that may contain functionally distinct subtypes.The purpose of our study is to identify molecular markers of cancer-promoting TDPs and develop strategies to target TDPs to enhance the therapeutic effect of ICB on cc RCC.Methods:We analyzed the relationship between Endosialin expression and CD8⁺T cells infiltration in cc RCC tumor samples using flow cytometry and in cc RCC-bearing mice inhibited for Endosialin via knockout or antibody-mediated blockade.The function of Endosialin^highTDPs in CD8⁺T cells infiltration and tumor progression was analyzed using RNA-sequencing（RNA-seq）data from cc RCC tissue-derived TDPs and single-cell RNA-seq（sc RNA-seq）data from an online database.The role of Endosialin in TDP proliferation and migration and in CD8⁺T cells infiltration was examined in vitro.Finally,we examined the anti-tumor effect of combined anti-Endosialin and anti-programmed cell death protein 1（PD-1）antibodies in cc RCC-bearing mice.Results:In patients with cc RCC,we found that high expression of Endosialin was associated with low CD8⁺T cells infiltration.Animal experiments showed that inhibition of Endosialin significantly increased CD8⁺T cells infiltration in cc RCC tumor-bearing mice.RNA-seq and sc RNA-seq analysis showed that high expression of Endosialin represented the activation state of TDPs.In vitro experiments also confirmed that Endosialin can promote the proliferation and migration of TDPs and inhibit the infiltration of CD8⁺T cells.Finally,the combination of anti-EN and anti-PD1 antibodies synergistically enhanced anti-tumor efficacy.Conclusion:Endosialin^high TDPs are in an activated state and inhibit CD8⁺T cells infiltration into cc RCC tissues.Combined treatment with anti-EN and anti-PD1 antibodies may improve ICI therapy effectiveness against cc RCC.