CD8A and neoplasm: Myeloid-derived suppressor cells (MDS) and Treg cells both play important roles in facilitating the anti-tumor phenotype for PDAC by suppressing host immune responses against tumor cells, including decreasing anti-tumor cytotoxic CD8 T cell recruitment and upregulating PD1-PDL1 expression in tumor cells, which is a crucial step in facilitating tumor growth, distant metastasis, and increased drug resistance [144,145].