Objective: To explore the immunophenotypic characteristics of CD7 and/or CD56 positive acute myeloid leukemic stem cells, and the relationship between minimal residual disease (MRD) and the leukemic stem cells (LSC).
Methods: The immunophenotype of leukemia cells from 51 CD34+ CD38+ CD7+ and/or CD34+ CD38+ CD56+ acute myeloid leukemia (AML) patients (exclude M3) at diagnosis was analyzed by using 4 - 6 panels of 4 color antibodies, and cells from 28 normal bone marrow (NBM) samples were served as control. The expression of CD7 and CD56 in the CD34+ CD38+ subpopulation was used as a leukemic cell marker for monitoring MRD of 53 samples from 26 CD7+ and (or) CD56+ patients.
Results: In CD7+ and/or CD56+ AML patients at diagnosis, the average positivity of CD7 in CD34+ CD38+ subpopulation and CD34+ CD38- Lin- stem cells subpopulation was (77.39 +/- 20.71)% and (44.57 +/- 22.70)%, and that of CD56 was (56.71 +/- 32.56)% and (33.51 +/- 29.64)%, respectively, all significantly higher than that of NBM (P < 0.01 and P < 0.05). Compared with that of NBM, the expression of CD90 in AML patients was significantly lower in the CD34+ CD38- Lin- subpopulation (P < 0.01), the expression of CD123 was significantly higher than NBM (P < 0.01), and the expression of CD117 was no significant difference (P > 0.05). In follow up of CD7+ and (or) CD56+ patients, the expression rate of CD7 and (or) CD56 in the CD34+ CD38- Lin- subpopulation MRD+ group was significantly higher than that in the MRD- group. The actual rate for CD7 was 71% (15/21) and 16% (4/25) (P = 0.001), and its relative rate was 81% (17/ 21) and 24% (6/25) (P = 0.000), respectively. The actual rate of CD56 is 100% (4/4) and 12% (3/25) (P = 0.001), and its relative rate was 75% (3/4) and 20% (5/25) (P = 0.031), respectively. A high CD7+ CD34+ CD38- Lin- subpopulation frequency at diagnosis in CD7+ AML patients predicted a high frequency of positive MRD in later detection (P < 0.05).
Conclusions: CD7 and CD56 are expressed on the stem cells in CD7+ and/or CD56+ AMLs and a high frequency of CD7 and CD56 in the CD34+ CD38- Lin- stem cell subpopulation predicts a high frequency of positive MRD in later detection.