Small-molecule inhibitors targeting INK4 protein p18INK4C enhance ex vivo expansion of haematopoietic stem cells

Among cyclin-dependent kinase inhibitors that control the G1 phase in cell cycle, only p18 and p27 can negatively regulate haematopoietic stem cell (HSC) self-renewal. In this manuscript, we demonstrate that p18 protein is a more potent inhibitor of HSC self-renewal than p27 in mouse models and its deficiency promoted HSC expansion in long-term culture. Single-cell analysis indicated that deleting p18 gene favoured self-renewing division of HSC in vitro. Based on the structure of p18 protein and in-silico screening, we further identified novel small-molecule inhibitors that can specifically block the activity of p18 protein. Our selected lead compounds were able to expand functional HSCs in a short-term culture. Thus, these putative small-molecule inhibitors for p18 protein are valuable for further dissecting the signalling pathways of stem cell self-renewal and may help develop more effective chemical agents for therapeutic expansion of HSC. The cyclin-dependent kinase inhibitors p18 and p27 confer advantage to the propagation of haematopoietic stem cells (HSCs). In this manuscript, the authors demonstrate that p18 is a potent negative regulator of HSC self-renewal, and identify novel small molecules putatively inhibiting p18 that promote HSC growth in culture and mouse transplant assays.