CD8A and neoplasm: Irinotecan treatment in murine models of cancer have provided evidence that the drug may affect the tumor immune environment in several ways, including (a) increased proliferation of tumor-specific CD8+ T cell, (b) increase in immunostimulatory IFNγ production, (c) decreased amount of FOXP3+ regulatory T cells [91], and (d) myeloid-derived suppressor cells (MDSCs) that are normally responsible for immunosuppressive effects with (e) an accompanying overall increase in MHC class I and PD-L1 expression in tumor cells.