In Myelodysplastic Syndrome (MDS), the expression of PD-1 in hematopoietic stem/progenitor cells and PD-L1 in MDSC are increased, and c-Myc is necessary for S100a9 to up-regulate PD-1/PD-L1 expression [46]. The gene discussed is PDCD1; the disease is myelodysplastic syndrome.