PTPRC and neoplasm: To investigate whether tumor-derived factors directly influence tumor-infiltrated immune cell survival, we isolated freshly immune cells from either pancreas tumor tissues or the blood or spleen of tumor-bearing KPC mice at 15 weeks old and sorted neutrophils including PMN-MDSC (CD45+CD11b+Ly6G+), cytotoxic T cells (CD45+CD3+CD8+) and DCs (CD45+ CD11c+), respectively.