Our results indicate that the upregulation of PD-L1 expression induced by romidepsin treatment suppresses cellular immune functions in colon cancer, including downregulating the ratio of Th1/Th2 cells (shown as IFN-γ/IL-4) and the secretion of IFN-γ in CD8+ T cells, as well as upregulating the percentage of Foxp3+ Tregs. This evidence concerns the gene CD8A and malignant colon neoplasm.