Systematic pan-cancer analysis reveals immune cell interactions in the tumor microenvironment

abstract AACR Cancer Research

 With the recent advent of immunotherapy, there is a critical need to understand immune cell interactions in the tumor microenvironment in both pan-cancer and tissue-specific contexts. Multi-dimensional datasets have enabled systematic approaches to dissect these interactions in large numbers of patients, furthering our understanding of the patient immune response to solid tumors. Using an integrated approach, we infered the infiltration levels of distinct immune cell subsets in 23 tumor types from The Cancer Genome Atlas. From these quantities, we constructed a co-infiltration network, revealing interactions between cytolytic cells and myeloid cells in the tumor microenvironment. By integrating patient mutation data, we show that while mutation burden was associated with immune infiltration differences between distinct tumor types, additional factors may explain immunogenic differences between tumors originating from the same tissue. Finally, we examined the prognostic value of individual immune cell subsets as well as how co-infiltration of functionally discordant cell types associated with patient survival. We showed in multiple tumor types that the protective effect of CD8+ T cell infiltration was heavily modulated by co-infiltration of macrophages and other myeloid cell types, suggesting the involvement of myeloid-derived suppressor cells in tumor development. Our findings illustrate complex interactions between different immune cell types in the tumor microenvironment and indicate these interactions play meaningful roles in patient survival. These results demonstrate the importance of personalized immune response profiles when studying the factors underlying tumor immunogenicity and immunotherapy response.