TPO signals in HSCs. TPO is essential for the maintenance of HSCs mediated by regulation of a variety of signaling molecules that are involved in cell cycle, survival, cellular metabolism, and integrin-mediated signal transduction. ERK and NF-κB collaborate to repair IR-induced DNA damage under TPO stimulation, preventing aging and tumorigenesis. These TPO signals working in harmony support the maintenance of HSCs. Professional illustration by Alice Y. Chen.