Cluster of differentiation 96 as a leukemia stem cell-specific marker and a factor for prognosis evaluation in leukemia

Resistance to chemotherapy is a major challenge for leukemia treatment. It has been suggested that leukemia stem cells (LSCs), a small pool of self-renewing leukemic cells, play important roles in development of chemotherapy resistance. The expression of cluster of differentiation 96 (CD96), a potential marker for LSCs, was investigated in CD34⁺CD38^- cells of 105 acute leukemia (AL) patients by flow cytometry. The data showed that all the CD34⁺, CD34⁺CD38^- and CD34⁺CD38^-CD96⁺ proportions were much higher in AL compared to the normal control (P<0.01), while a clear difference was identified in the CD34⁺CD38^- and CD34⁺CD38^-CD96⁺ proportions between acute lymphoid leukemia and acute myeloid leukemia (AML). However, all the AML patients with >15% CD34⁺CD38^- cells achieved complete remission (CR), suggesting that as an LSC-rich population, the amount of CD34⁺CD38^- cells may not be positively associated with the proportion of refractory LSCs. The mean percentage of the co-presence of CD96 expression itself was similar in AML patients with CR and non-CR (P>0.05). However, the CR rate was significantly higher in the AML population with <10% CD96 expressed, which indicated that a distinct sub-group of CD34⁺CD38^-CD96⁺ cells may still contribute to the drug resistance or poor prognosis.