We found a detectable PD-1 expression in leukemic cells in 9 of the 14 (64%) Pax5+/− B-ALL samples, and also in 2 of the 3 (67%) Sca1-ETV6-RUNX1+ B-ALL samples (Figure 1B and Table S1). The gene discussed is PDCD1; the disease is acute lymphoblastic leukemia.