CD8A and neoplasm: However, a dismal response to ICI therapy by PDAC in comparison with other solid tumors (12, 15, 16) may accounting for merely 4% of tumor cells with the expression of PD-L1 (17); most of PDAC tumors present intermediate to high expression of infiltrating T cells that are mainly CD4+ T cells rather than CD8+ T cells (17) and the relatively low mutational burden (18).