Therefore, we first tested Pi-ATAC on an artificial mixture of mouse breast tumor cell line 4T1 and mouse splenocytes for (i) the sort efficiency of cells with comparable size differences as occurring in the primary tumors, (ii) lineage-specific antibodies, such as the mutually exclusive expression of EpCAM in the breast cancer cells and CD45 in splenocytes and tumor-infiltrating immune cells. Here, EPCAM is linked to breast cancer.