Atlas of immune cell infiltration in breast cancer-high M2 macrophage and low native B cellproportions are associated with poor survival

Background: Knowledge of the tumor immune microenvironment is critical for developing new treatments targeting the immune system in breast cancer. However, no profile of immune cell infiltration in breast cancer has been provided. The aim of this study is to illustrate an atlas of the immune cell microenvironment of breast cancer. Methods: We obtained data for breast cancer control samples from the TCGA database. The CIBERSORT algorithm was used to calculate the tumor-infiltrating immune cell (TIIC) composition. Furthermore, we performed correlation analysis of clinical information and tumor-infiltrated immune cells. Results: We found that the adaptive immune system was generally suppressed. Compared with normal tissues, breast cancer tissues had a higher fraction of memory B cells, naive CD4 T cells, and regulatory T cells. Breast cancer tissues had a lower fraction of naive B cells and plasma cells. The innate immune system was activated in breast cancer tissue. Compared with normal tissues, breast cancer tissues had a higher fraction of M1 macrophages, monocytes, activated NK cells, and activated mast cells. Breast cancer tissues had a lower fraction of M2 macrophages. The same trends were found in Her2+, luminal and triple-negative subtypes. Furthermore, we found that high M2 macrophage and low native B cell counts were associated with poor survival. TIIC s were correlated with the primary tumor, lymph node, metastasis and stage. Conclusions: Breast cancer tissues suppress the adaptive immune system and activate the innate immune system. High M2 macrophage and low native B cell counts predict poor survival.