For proof of concept, we initially used CD34+ cells from granulocyte colony stimulating factor (G-CSF)-mobilized peripheral blood samples that were collected from patients with metastatic melanoma enrolled in a dendritic cell vaccine trial.16 Consistent with the data in figure 1 using HSPCs from healthy adults, this showed that engrafting fewer cells yielded higher levels of human engraftment in MISTRG6 compared with MISTRG mice, and that efficient engraftment was feasible with 100,000 to 300,000 CD34+ cells (figure 2A). Here, CSF3 is linked to metastatic melanoma.