Humanized NSG mice reconstituted with CD34+ hematopoietic stem cells have been developed to study the efficacy of PD1 blockade on the growth of PDXs in several cancer types.11 However, potential drawbacks of the CD34+ humanized mouse model include a lengthy period (>12 weeks) for the engrafted CD34+ cells to fully differentiate into functional immune cells, and requirements for human leukocyte antigen (HLA) matching to avoid allogenic effects on the tumors12; a problem that can be prevented by using a completely autologous system. Here, CD34 is linked to cancer.