Endosialin positive tumor derived pericytes promote tumor progression through impeding the infiltration of CD8 + T cells in clear cell renal cell carcinoma

Abstract Background: Clear cell renal cell carcinoma (ccRCC) is considered to be an immunogenic tumor, and immune checkpoint blockade (ICB) therapy provides effective option for RCC treatment. However, a large proportion of patients do not benefit from ICB therapy. Tumor derived pericytes (TDPs) are an important component in tumor microenvironment (TME), and may promote tumor progression through the regulation on T cells. TDPs has been considered as ideal target for tumor treatment. However, like CAFs, TDPs are also heterogeneous, different subclusters may have distinct function. Here, we aimed to identify new specific marker for tumor promoting TDPs and to develop novel TDPs targeting therapeutic strategies to enhance the efficacy of ICB therapy in ccRCC.Methods: To analyze the relationship between endosialin (EN) expression and the infiltration of CD8+ T cells in ccRCC, we performed flow cytometry using freshly isolated tumor specimens from ccRCC patients. Then, their correlation was verified in ccRCC-bearing wildtype and endosialin knockout mice, and also by antibody mediated blockade of endosialin. RNA-sequencing (RNA-seq) using EN-high and EN-low TDPs from ccRCC tissues and published single-cell RNA-sequencing (scRNA-seq) data of ccRCC were analyzed to figure out the potential functions of EN-high TDPs in CD8+ T cell infiltration and tumor progression. Function of endosialin in the regulation of cell proliferation and migration of TDPs, and CD8+ T cells infiltration was examined in vitro. Combined treatment with endosialin antibody and PD-1 blockade was applied to treat ccRCC-bearing mice and the anti-tumor effect was examined.Results: We found that high endosialin expression was associated with low infiltration of CD8+ T cells in clinical ccRCC tissues. Endosialin knockout or antibody blockade could significantly increase the infiltration of CD8+ T cells in ccRCC-bearing model. RNA-seq and scRNA-seq analysis indicated that high EN-high TDPs represent an activated state of TDPs. We also demonstrated that endosialin could promote the proliferation and migration of TDPs and impede the infiltration of CD8+ T cells in vitro. At last, we showed that combined treatment with anti-endosialin antibody could enhance the anti-tumor efficacy of PD-1 blockade.Conclusion: We reported EN-high TDPs represent an activated state of TDPs and inhibit the infiltration of CD8+ T cells into ccRCC tissues. Combined treatment with anti-endosialin antibody and PD-1 antibody provided a rational strategy to improve effect of ICB therapy in ccRCC.