Considering that Treg cells express high levels of PD-1, combined with our results showing that interruption of the PD-L1/PD-1 axis leads to expansion of HSPCs in tumor-bearing mice, it is plausible that Treg cells may co-ordinate the cancer-associated emergency myelopoiesis through the PD-1 axis. Here, PDCD1 is linked to neoplasm.