CD274 and neoplasm: PD-1 signaling has been intensively studied with a focus on the PD-1-expressed immune cells, including activated T cells.8 Recently, functional roles of PD-1 signaling have been extended to non-immune cell types, such as tumor cells,31–33 retinal ganglion cells,34 and stem cells.35 In particular, Shi group demonstrated that SHED express PD-1, which regulates cell proliferation and differentiation.35 However, the potential functions and expressional patterns of PD-L1 and PD-1 during the differentiation of hDPSCs into the odontogenic lineage are unknown.