To identify more such surface immune molecules, we screened approximately 30 cell surface proteins expressed in immune systems, and found that several immune molecules, including IREM-1, BTLA, CD244, JAM3, B7-H1 and B7-H4, were highly expressed on MLL-AF9-induced human acute myeloid leukemia (AML) cells.6 Interestingly, one of the identified candidates B7-H4 was also expressed on one fraction of human LIC-enriched CD34+ AML cells as determined by flow cytometric analysis (Supplementary Figure 1a). Here, PROS1 is linked to acute myeloid leukemia.