Delineation of target expression profiles in CD34¹/CD38² and CD34¹/CD38¹ stem and progenitor cells in AML and CML

In an attempt to identify novel markers and immunological targets in leukemic stem cells (LSCs) in acute myeloid leukemia (AML) and chronic myeloid leukemia (CML), we screened bone marrow (BM) samples from patients with AML (n 5 274) or CML (n 5 97) and controls (n 5 288) for expression of cell membrane antigens on CD34¹/CD38² and CD34¹/CD38¹ cells by multicolor flow cytometry. In addition, we established messenger RNA expression profiles in purified sorted CD34¹/CD38² and CD34¹/CD38¹ cells using gene array and quantitative polymerase chain reaction. Aberrantly expressed markers were identified in all cohorts. In CML, CD34¹/CD38² LSCs exhibited an almost invariable aberration profile, defined as CD25¹/CD26¹/CD56¹/CD93¹/IL-1RAP¹. By contrast, in patients with AML, CD34¹/CD38² cells variably expressed “aberrant” membrane antigens, including CD25 (48%), CD96 (40%), CD371 (CLL-1; 68%), and IL-1RAP (65%). With the exception of a subgroup of FLT3 internal tandem duplication–mutated patients, AML LSCs did not exhibit CD26. All other surface markers and target antigens detected on AML and/or CML LSCs, including CD33, CD44, CD47, CD52, CD105, CD114, CD117, CD133, CD135, CD184, and roundabout-4, were also found on normal BM stem cells. However, several of these surface targets, including CD25, CD33, and CD123, were expressed at higher levels on CD34¹/CD38² LSCs compared with normal BM stem cells. Moreover, antibody-mediated immunological targeting through CD33 or CD52 resulted in LSC depletion in vitro and a substantially reduced LSC engraftment in NOD.Cg-Prkdc^scid Il2rg^tm1Wjl/SzJ (NSG) mice. Together, we have established surface marker and target expression profiles of AML LSCs and CML LSCs, which should facilitate LSC enrichment, diagnostic LSC phenotyping, and development of LSC-eradicating immunotherapies.