Bone marrow CD8 T cells express high frequency of PD-1 and exhibit reduced anti-leukemia response in newly diagnosed AML patients

Acute myeloid leukemia (AML) is a devastating blood cancer with 5-year survival of only 25%. Novel effective leukemia therapy is an urgent unmet need. Immunotherapy is a promising strategy for cancer treatment. Targeting inhibitory mechanisms, such as the programmed cell death protein 1 (PD-1) pathway to unleash the patient’s own anti-tumor immune response has achieved major success 1 . Several studies including ours have demonstrated an involvement of PD-1 and other T cell inhibitory pathways in AML progression 2 , 3 , 4 , 5 , 6 , 7 . Strategies of blocking immune suppression for leukemia treatment are attractive due to their relatively simple administration and better tolerability profile. In fact, clinical studies applying anti-PD-1 in AML therapy have been initiated and are currently in early phase trials 8 . AML is a highly heterogeneous disease with multiple steps involved in the treatments. Determining the status of the immune response at each disease stage in individual patients is crucial for decision making of subsequent clinical management. In addition, immune characterization has great potential to identify predictive biomarkers of responsiveness to immunotherapy, thus providing pivotal information to optimize clinical trial design using strategies modulating anti-leukemia immunity for AML treatment.