Interleukin-3 receptor α chain (CD123) is preferentially expressed in immature T-ALL and may not associate with outcomes of chemotherapy.

Interleukin-3 (IL-3) receptor α chain (CD123) plays an essential role in regulating the proliferation of hematopoietic stem cells. In the hematopoietic malignancies, CD123 expression has been found in acute myeloid leukemia (AML), B-precursor acute lymphoblastic leukemia (B-ALL), as well as dendritic cell malignancies. However, whether CD123 is also expressed in T-acute lymphoblastic leukemia (T-ALL) remains unknown. Using multi-parameter flow cytometry, we analyzed CD123 expression in 160 consecutive diagnostic T-ALL patients, including 88 pediatric T-ALL cases and 72 adult T-ALL cases. The minimal residual disease (MRD) was detected after one course of induction therapy to evaluate the treatment effects. CD123 expression was detected in 24 out of 88 (27 %) pediatric T-ALLs and 30 out of 72 (42 %) adult T-ALLs. Further analysis revealed that CD123 expression is associated with the maturation stage of T-ALLs. The frequencies of CD123-positive cases decreased from 83 to 40 % and 21 % in early T-precursor ALLs, T-precursor ALLs, and mature T-ALLs, respectively. Interestingly, we detected the CD4+CD8+ double-positive leukemic cells in 22 immature and 34 mature T-ALL patients. Of note, only 4 % of these patients expressed CD123. In addition, we found that 79 % of CD33+ and 64 % of CD117+ immature T-ALL patients also expressed CD123. However, CD123 expression did not predict the outcomes of the first course of induction therapy in T-ALL patients. In conclusion, we found that CD123 is preferentially expressed in immature T-ALL. Moreover, CD123 expression is strongly associated with cross-lineage expression of myeloid markers in early T-precursor ALL.