Application of CD123 in detection of minimal residual disease in acute promyelocytic leukemia

The study was aimed to investigate the role and significance of CD123 with other immunological markers in detecting minimal residual disease (MRD) of APL patients. The immunophenotypes of 186 newly diagnosed APL patients and the percentages of cells identical with APL cell immunophenotypes in 20 normal bone marrow samples were analyzed using four-color flow cytometry. MRD in 172 specimens were monitored by mainly using CD34/CD117/CD123/HLA-DR four-color antibody panels, meanwhile 18 specimens were analyzed with the second antibody combination: CD9/CD117/CD34/CD33, simultaneously and the results were compared with real-time PCR. One hundred and sixteen of 172 bone marrow (BM) or peripheral blood (PB) specimens were from follow-up 19 newly diagnosed APL patients and the rest 56 samples were from 47 patients treated 3 to 24 months later. Among them, 117 samples and 55 samples were collected after achieving morphologic complete remission (mCR) and before achieving mCR respectively. The results of immunophenotyping demonstrated that except CD9, CD33 and CD117 were high-expressed and CD34 and HLA-DR were rarely expressed, the CD123 was expressed in 30/30 (100%) APL patients. The percentages of CD117(+)CD34(-)CD123(+)HLA-DR(-) and CD117(+)CD34(-)CD9(+)CD33(+) cells in nucleated cells were 0.066% +/- 0.012% and 0.089% +/- 0.066% in 20 normal bone marrow samples. The median time of achieving morphology complete remission in 19 APL patients was 4 weeks (3 - 6 weeks). The median time of FCM and PCR results turned to be negative in 13 APL patients was 7.5 weeks (5 - 11) and the median time of PCR results turned to be negative in 11 APL patients was 8 weeks (5 - 12). 41/117 (35.04%) samples were MRD positive by FCM after achieving mCR. The ratio of CD117(+)CD34(-)CD123(+)HLA-DR(-) cells was < 5% in 33 specimens, but > 5% in another 8 specimens, their median percentages of CD117(+)CD34(-)CD123(+)HLA-DR(-) cells were 0.48% (range 0.02% - 4.70%) and 9.02% (range 5.26% - 18.14%) respectively. The median relative percentages of CD123(+)HLA-DR(-) cells in CD117(+)CD34(-) population were 63.59% (range 15.11% - 98.36%) and 86.77% (range 63.29% - 92.62%) respectively. In FCM MRD positive samples, 95.9% (93/97) were PCR positive, the false positive rate of FCM and the false negative rate of PCR were 4.1% (4/97) and 8.75% (7/93) respectively. In FCM negative samples, 92% (69/75) were PCR negative and 8% (6/75) were PCR positive. The percentages of CD117(+)CD34(-)CD123(+)HLA-DR(-) cells in 116 consecutive specimens and 117 specimens of mCR were related to PML/RARalpha quantified by real-time PCR (r = 0.824, P < 0.001 and r = 0.754, P < 0.001 respectively). It is concluded that the detection of APL patients by means of two sets of antibody panels is simple and suitable, which is complementary to PCR in monitoring MRD of APL patients.PubMed03427-321