To more broadly quantify this hematopoiesis-supporting gene expression pattern of stromal cells, we aggregated gene programs of hematopoiesis-supporting factors (Cxcl12, Kitl, Il7, and Igf1) and observed a significant increase in this gene expression signature in the most primitive CAR cells upon engraftment with MDS than in those with HY (Figure 1F). Here, IGF1 is linked to myelodysplastic syndrome.