In a heterogeneous cohort of 61 patients (MDS, CMML and AML) treated with HMAs (the majority (87%) in combination with other agents) up-regulation (≥2-fold) of PD-1 gene expression in PBMNCs was observed during the first cycle of therapy in 58% of the patients. The gene discussed is PDCD1; the disease is myelodysplastic syndrome.