Clinical Significance of ABCB1 in Acute Myeloid Leukemia: A Comprehensive Study.

ABCB1 is a member of the ATP binding cassette transporter family and high ABCB1 activity is considered as a poor prognostic factor in acute myeloid leukemia (AML) treated with intensive chemotherapy, its direct relation with drug resistance remains unclear. We evaluated ABCB1 activity in relation with clinical parameters and treatment response to standard chemotherapy in 321 patients with de novo AML. We assessed multiple clinical relationships of ABCB1 activity-ex vivo drug resistance, gene expression, and the ABCB1 inhibitor quinine were evaluated. ABCB1 activity was observed in 58% of AML and was linked to low white blood cell count, high expression of CD34, absence of FLT3-ITD, and absence of mutant NPM1. Moreover, ABCB1 activity was associated with worse overall- and event-free survival. However, ABCB1 activity did not directly lead to ex vivo drug resistance to anthracyclines. We found that ABCB1 was highly correlated with gene expressions of BAALC, CD34, CD200, and CD7, indicating that ABCB1 expression maybe a passenger characteristic of high-risk AML. Furthermore, ABCB1 was inversely correlated to HOX cluster genes and CD33. Thus, low ABCB1 AML patients benefited specifically from anti-CD33 treatment by gemtuzumab ozogamicin in addition to standard chemotherapy. We showed prognostic importance of ABCB1 gene expression, protein expression, and activity. Furthermore, ABCB1 was not directly linked to drug resistance, ABCB1 inhibition did not improve outcome of high ABCB1 AML patients and thus high ABCB1 may represent a passenger characteristic of high-risk AML.

Prognostic value of multicenter flow cytometry harmonized assessment of minimal residual disease in acute myeloblastic leukemia.

The assessment of minimal residual disease (MRD) in acute myeloblastic leukemia is of growing interest as a prognostic marker of patients' outcome. Multiparameter flow cytometry (MFC), tracking leukemia-associated immunophenotypic patterns, has been shown in several studies to be a useful tool to investigate MRD. Here, we report a multicenter prospective study which allowed to define a harmonized analysis strategy, as well as the efficacy of MFC MRD to predict outcome. This study included 276 patients, in 10 different MFC centers, of whom 268 had at least 1 MRD check point. The combination of a CD45, CD34, and CD33 backbone, with the addition of CD117, CD13, CD7, and CD15 in 2 five-color tubes allowed to define each patient's multiparameter immunophenotypic characteristics at diagnosis, according to a Boolean combination of gates. The same individual diagnosis gating strategy was then applied at each MRD time point for each patient. MRD levels were stratified according to log by log thresholds, from 5 × 10-2 (the classical morphological threshold to define remission) down to <5 × 10-5 . MRD was found to be constantly negative (<5 × 10-5 ) for 148 patients. Survival analyses significantly associated MRD negativity with a good prognosis and any positive value with poorer outcome. All P values were <0.0001 both for disease-free and overall survival at the earliest time point (post-induction, MRD1) as well as when considering all time points together. Finally, MRD levels were independent of cytogenetics and allowed in fact to further stratify all cytogenetics risk groups. In summary, this multicenter study demonstrates that a simple combination of immunophenotypic markers successfully allows for the detection of MRD in acute myeloblastic leukemia patients, with a strong correlation to outcome.

Involvement of a common progenitor cell in core binding factor acute myeloid leukaemia associated with mastocytosis.

In core binding factor (CBF) acute myeloid leukaemia (AML), realtime quantitative PCR is useful to quantify the fusion transcript ratio (CBFß-MYH11 and AML1-ETO, in case of inv(16) and t(8;21) respectively) in peripheral blood and bone marrow during the courses of chemotherapy, in order to monitor minimal residual disease (MRD). In two cases of CBF AML associated with systemic mastocytosis (SM), the persistence of mast cells and the detection of a high ratio of fusion transcript, in bone marrow, during the courses of chemotherapy, led us to determine whether the mast cell component of the disease carried the same molecular alterations as leukaemic blasts. We demonstrate that sorted mast cells carried CBF abnormality. These observations point out the lack of specificity of MRD monitoring by RQ-PCR in these exceptional AML cases with SM. Moreover, this suggests that leukaemic blasts and mast cells derive from a common malignant progenitor.

A GEIL flow cytometry consensus proposal for quantification of plasma cells: application to differential diagnosis between MGUS and myeloma.

BACKGROUND: Flow cytometry is the sole available technique for quantification of tumor plasma-cells in plasma-cell disorders, but so far, no consensus technique has been proposed. Here, we report on a standardized, simple, robust five color flow cytometry protocol developed to characterize and quantify bone marrow tumor plasma-cells, validated in a multicenter manner. METHODS: CD36 was used to exclude red blood cell debris and erythroblasts, CD38 and CD138 to detect plasma-cells, immunoglobulin light chains, CD45, CD56, CD19, and CD117 + CD34 to simultaneously characterize abnormal plasma-cells and quantify bone marrow precursors. This approach was applied in nine centers to 229 cases, including 25 controls. RESULTS: Tumor plasma-cells were detected in 96.8% of cases, all exhibiting an immunoglobulin peak over 1g/L. Calculation of a plasma-cells/precursors (PC/P) ratio allowed quantification of the plasma-cell burden independently from bone marrow hemodilution. The PC/P ratio yielded the best results in terms of sensitivity (81%) and specificity (84%) for differential diagnosis between MGUS and myeloma, when compared with other criteria. Combination of both the PC/P ratio and percentage of abnormal plasma-cells allowed the best differential diagnosis, but these criteria were discordant in 25% cases. Indirect calculation of CD19 negative PC/R ratio gave the best results in terms of sensitivity (87%). CONCLUSION: This standardized multiparameter flow cytometric approach allows for the detection and quantification of bone marrow tumor plasma-cell infiltration in nearly all cases of MGUS and myeloma, independently of debris and hemodilution. This approach may also prove useful for the detection of minimal residual disease.

Extended diagnostic criteria for plasmacytoid dendritic cell leukaemia.

The diagnosis of plasmacytoid dendritic cell leukaemia (pDCL) is based on the immunophenotypic profile: CD4(+) CD56(+) lineage(neg) CD45RA(+)/RO(neg) CD11c(neg) CD116(low) CD123(+) CD34(neg) CD36(+) HLA-DR(+). Several studies have reported pDCL cases that do not express this exact profile or expressing some lineage antigens that could thus be misdiagnosed. This study aimed to validate pDCL-specific markers for diagnosis by flow-cytometry or quantitative reverse transcription polymerase chain reaction on bone marrow samples. Expression of markers previously found in normal pDC was analysed in 16 pDCL, four pDCL presenting an atypical phenotype (apDCL) and 113 non-pDC - lymphoid or myeloid - acute leukaemia. CD123 was expressed at significantly higher levels in pDCL and apDCL. BDCA-2 was expressed on 12/16 pDCL and on 2/4 apDCL, but was never detected in the 113 non-pDC acute leukaemia cases. BDCA-4 expression was found on 13/16 pDCL, but also in 12% of non-pDC acute leukaemia. High levels of LILRA4 and TCL1A transcripts distinguished pDCL and apDCL from all other acute leukaemia (except B-cell acute lymphoblastic leukaemia for TCL1A). We thus propose a diagnosis strategy, scoring first the CD4(+) CD56(+/-) MPO(neg) cCD3(neg) cCD79a(neg) CD11c(neg) profile and then the CD123(high), BDCA-2 and BDCA-4 expression. Atypical pDCL can be also identified this way and non-pDC acute leukaemia excluded: this scoring strategy is useful for diagnosing pDCL and apDCL.

Predictive factors of response and survival in myelodysplastic syndrome treated with erythropoietin and G-CSF: the GFM experience.

We analyzed prognostic factors of response, response duration, and possible impact on survival of epoetin alpha, epoetin beta, or darbepoetin alpha (DAR) with or without granulocyte colony-stimulating factor in 403 myelodysplastic syndrome (MDS) patients. Sixty-two percent (40% major and 22% minor) and 50% erythroid responses were seen, and median response duration was 20 and 24 months according to IWG 2000 and 2006 criteria, respectively. Significantly higher response rates were observed with less than 10% blasts, low and int-1 International Prognostic Scoring System (IPSS), red blood cell transfusion independence, serum EPO level less than 200 IU/L, and, with IWG 2006 criteria only, shorter interval between diagnosis and treatment. Significantly longer response duration was associated with major response (IWG 2000 criteria), IPSS low to INT-1, blasts less than 5%, and absence of multilineage dysplasia. Minor responses according to IWG 2000 were reclassified as "nonresponders" or "responders" according to IWG 2006 criteria. However, among those IWG 2000 minor responders, response duration did not differ between IWG 2006 responders and nonresponders. Multivariate adjusted comparisons of survival between our cohort and the untreated MDS cohort used to design IPSS showed similar rate of progression to acute myeloid leukemia in both cohorts, but significantly better overall survival in our cohort, suggesting that epoetin or DAR treatment may have a favorable survival impact in MDS.

Multi-drug resistance mediated by P-glycoprotein overexpression is not correlated with ZAP-70/CD38 expression in B-cell chronic lymphocytic leukemia.

ZAP-70 and CD38 expression can identify B-cell chronic lymphocytic leukemia with an inferior clinical outcome. Many groups have investigated the meaning of the expression of these two proteins and the correlation with the bad prognosis in B-CLL. But nobody has investigated the relation between the multidrug resistance mediated by Pgp overexpression (MDR1) and ZAP-70/CD38 coexpression. Forty-one untreated and stage A patients, either ZAP-70(+)CD38(+) or ZAP-70(-)CD38(-), were tested to determine the MDR1 status. MDR1 was observed in 41% of CLL ZAP-70(+)CD38(+) and in 37% of CLL ZAP-70(-)CD38(-). The difference was not significant (p = 0.745). Patients with ZAP-70 and CD38 positive CLL can not be candidates for MDR1 antagonists.

NF-kappaB constitutes a potential therapeutic target in high-risk myelodysplastic syndrome.

Myelodysplastic syndrome (MDS) is a preneoplastic condition that frequently develops into overt acute myeloid leukemia (AML). The P39 MDS/AML cell line manifested constitutive NF-kappaB activation. In this cell line, NF-kappaB inhibition by small interfering RNAs specific for p65 or chemical inhibitors including bortezomib resulted in the down-regulation of apoptosis-inhibitory NF-kappaB target genes and subsequent cell death accompanied by loss of mitochondrial transmembrane potential as well as by the mitochondrial release of the caspase activator cytochrome c and the caspase-independent death effectors endonuclease G and apoptosis-inducing factor (AIF). Bone marrow cells from high-risk MDS patients also exhibited constitutive NF-kappaB activation similar to bone marrow samples from MDS/AML patients. Purified hematopoietic stem cells (CD34+) and immature myeloid cells (CD33+) from high-risk MDS patients demonstrated the nuclear translocation of the p65 NF-kappaB subunit. The frequency of cells with nuclear p65 correlated with blast counts, apoptosis suppression, and disease progression. NF-kappaB activation was confined to those cells that carried MDS-associated cytogenetic alterations. Since NF-kappaB inhibition induced rapid apoptosis of bone marrow cells from high-risk MDS patients, we postulate that NF-kappaB activation is responsible for the progressive suppression of apoptosis affecting differentiating MDS cells and thus contributes to malignant transformation. NF-kappaB inhibition may constitute a novel therapeutic strategy if apoptosis induction of MDS stem cells is the goal.

M0 AML, clinical and biologic features of the disease, including AML1 gene mutations: a report of 59 cases by the Groupe Français d'Hématologie Cellulaire (GFHC) and the Groupe Français de Cytogénétique Hématologique (GFCH).

Mutations of the AML1 gene are frequent molecular abnormalities in minimally differentiated acute myeloblastic leukemia (M0 AML), a rare type of AML. In this retrospective multicenter study, morphologic, immunophenotypical, cytogenetic, and molecular features of 59 de novo M0 AML cases were analyzed and correlated to AML1 mutations. Point mutations of AML1 gene were observed in 16 cases (27%). They were correlated with higher white blood cell (WBC) count (P =.001), greater marrow blast involvement (P =.03), higher incidence of immunoglobulin H/T-cell receptor (IgH/TCR) gene rearrangement (P <.0001), and with a borderline significant lower incidence of complex karyotypes. In the 59 patients, FLT3 mutations were the only significant prognostic factors associated with short survival.

Unlike AML1, CBFbeta gene is not deregulated by point mutations in acute myeloid leukemia and in myelodysplastic syndromes.

The core-binding factor (CBF) complex is a heterodimeric transcription factor composed of 2 subunits, CBFalpha and CBFbeta, that play a major role in hematopoiesis. Both members of the CBF complex are frequently altered in acute myeloid leukemia (AML) by translocation, most commonly t(8;21), t(12;21), and t(3;21) for CBFalpha, located in 21q22, and inv(16)(p13;q22) for CBFbeta, located on 16q22. Recently, a new mechanism of alteration of CBFalpha, by point mutation, has been reported in myeloid malignancies, particularly in M0 AML. In the present study, we found no point mutation of the CBFbeta gene in 30 myelodysplastic syndromes and 100 AMLs, suggesting a limited role, if any, of CBFbeta point mutations in those disorders.