The immunologic detection of minimal residual disease in acute leukemia

Certain combinations of differentiation antigens are expressed on leukemia blasts and are absent or extremely rare among normal progenitors in the fetal liver and fetal and regenerating bone marrow. These combinations include cCD3/TdT, a thymic feature retained on thymic-acute lymphoblastic leukemia (T-ALL) blasts outside the thymus, and the coexpression of TdT and myeloid markers (CD13, CD33) on a proportion of ALL and acute myeloid leukemia (AML). Thus, double marker immunofluorescence assays are operationally leukemia-specific and can be applied in 35% of acute leukemias for detecting minimal disease at a less than 10(-4) level; only rare cases, 2 of 35 in our study, switch these relevant features during relapse. The sensitivity and specificity of these assays was tested as follows. First, bone marrow samples taken from patients who had originally presented with blasts expressing the leukemia-associated combinations but were in full morphologic remission were studied, and varying numbers (less than 0.01% to 10% of the mononuclear fraction) of cells with aberrant features were identified in 11.6% of the cases. Second, the outcome of 19 patients with minimal disease identified immunologically while in complete morphologic remission was investigated: all 19 patients have developed systemic relapse within 4 to 25 (median 14.5) weeks. In contrast, 17 of 25 patients also morphologically in complete remission and without residual disease identifiable immunologically after repeated testing are still in morphologic and immunologic remission (follow-up 17 to 114 weeks, median 28 weeks). Only eight patients in this group have relapsed so far: in two patients the relapse was localized in the cerebrospinal fluid, while in six patients a systemic relapse was observed 6 to 51 (median 21.5) weeks after the last negative immunologic bone marrow examination. In conclusion, no false-positive results were detected with these sensitive assays, and the introduction of appropriately planned prospective studies, including the immunologic detection of residual leukemia, is justified on the basis of these observations.     

CD34+ cell subpopulations detected by 8-color flow cytometry in bone marrow and in peripheral blood stem cell collections: application for MRD detection in leukemia patients

Fast development in polychromatic flow cytometry (PFC) makes it possible to study CD34+ cells with two scatter and eight fluorescence parameters. Minimal residual disease (MRD) is determined as persistence of leukemic cells at submicroscopic levels in bone marrow (BM) of patients in complete remission. MRD can be present in collections of hematopoietic stem cell from blood (HSC-B). Using PFC, we have defined patterns of antigen expression in CD34+ cell subpopulations in BM and applied them as templates in MRD analysis. Twelve BM samples from hospital control (HC) patients with no signs of hematological malignancy were studied using five 8-color monoclonal antibody combinations detecting subsets of CD34+ cells. These patterns have been used as templates to determine levels of MRD in HSC-B collections from six AML patients. Several subsets of CD34+ precursor cells were found to be present at very low frequencies (<10⁻⁴) in BM and/or HSC-B collections. All six HSC-B collections from AML patients showed MRD by 8-color technique and only three by previously applied 3-color method. The 8-color technique showed promising results in efficient detection of different CD34+ subpopulations of HSC-B and in MRD quantification. Monitoring of MRD should become a part of quality control of HSC-B collections.     

GM-CSF stimulates proliferation of clonal leukemic bone marrow cells in acute myeloid leukemia (AML) in vitro

 Granulocyte-macrophage colony-stimulating factor (GM-CSF) is known to stimulate granulocytes, monocytes, and macrophages. We studied the effect of GM-CSF on (clonal) bone marrow (BM) cells obtained from AML patients after 7 days of culture in vitro: BM samples were obtained from 19 AML patients at diagnosis (DIA), from two patients with persisting disease (PERS), from eight patients in complete remission (CR), and from 12 healthy donors. Flow-cytometric comparison of differentiated, CD 15-positive cells or of CD34-positive blast cells before and after cultivation showed that the proportion of CD15-positive cells was increased in nine of 12 healthy BM samples, in 14 of 19 cases at DIA, in one of three cases during PERS, and in five of six cases in CR of AML. The proportion of CD34-positive cells was increased in one of 12 healthy BM samples, in seven of 19 cases at DIA, in one of two cases during PERS, and in three of seven cases in CR of AML. Southern blot analysis (SBA) performed in six cases during the course of AML, before and after cell culture, showed that clonal DNA increased after GM-CSF treatment in three of five cases studied at DIA, in six of nine cases studied in CR, in the one case studied at PERS, and in the one studied at relapse (REL). In one case of trisomy 8 at DIA a normal karyotype was demonstrated in CR. However, after 7 days of cultivation of the cells in GM-CSF the trisomy 8 was detected in two of 17 metaphases isolated from colony-cells from methylcellulose cultures. Our data show that a 7-day treatment of BM cells with GM-CSF induced a differentiation of healthy and leukemic BM cells in the great majority of cases. An enrichment of CD34-positive cells was not achieved in healthy BM samples. However, in 70% of the cases in CR and in 30% of the cases at DIA of AML, clonal CD34-positive cells were enriched. This means that GM-CSF stimulates ('primes') leukemic cell growth in vitro. Received: August 17, 1998 / Accepted: April 28, 1999     

The value of dot plot patterns and leukemia-associated phenotypes in AML diagnosis by multiparameter flow cytometry

The immunophenotypic features in patients with acute myeloid leukemia (AML) were investigated at diagnosis using a wide antibody panel including progenitor-associated, myeloid and lymphoid markers in quadruple combinations. Analyzed were bone marrow samples from 37 adult and pediatric patients for exact identification of AML blasts according their localization on CD45/SSC dot plots and aberrant immunophenotypes in various subtype of AML. We found the localization of AML blasts on CD45/SSC dot plots, which in combination with immunophenotype profile of blasts allow discrimination of several AML subtypes (M0-M2, M3, M4/M5 and other types). In 27/37 AML patients (73%) at least one leukemia-associated phenotype (LAP) was found, two or more aberrancies coexisted in more than a half of them (78%). Asynchronous expression was the most frequent type of LAP (77.8%, 21/27) followed by coexpression of lymphoid-associated antigens, which occurred in 18/27 (66.7%) patients. Presented study showed that leukemic cells of each AML patient had a unique antigenic profile and could be discriminated from their normal counterparts based on typical light scatter profiles and aberrant antigen expression that could further be used for detection of minimal residual disease.     

In situ RHAMM protein expression in acute myeloid leukemia blasts suggests poor overall survival

Treatment options for patients with high-risk acute myeloid leukemia (AML) include high-dose chemotherapy regimens in combination with allogeneic hematopoietic stem cell transplantation, which takes advantage of the donor T-cell-mediated graft-versus-leukemia effect. Together with beneficial responses observed in assays targeted at leukemia-associated antigens (LAA), this encouraged research on cancer vaccines and adoptive cellular therapies in AML. The receptor for hyaluronic acid-mediated motility (RHAMM, CD168) was identified as one of the most promising LAA in AML. Thus far, little is known about in situ expression in leukemic bone marrow blasts or the prognostic role of RHAMM and its interaction partners in AML. We immunohistochemically analyzed the expression and prognostic significance of RHAMM on trephine bone marrow biopsies from 71 AML cases that had been evaluated for cytogenetics and presence of FLT3-internal tandem duplications and NPM1 mutations. Fifty-five patients (77%) were treated with curative intent, while 16 (23%) received the most appropriate supportive care. Twenty of 71 (28%) AML cases were considered RHAMM+. Receiver operating characteristic curves showed significant discriminatory power considering overall survival (OS) in AML patients treated curatively for RHAMM (p = 0.015). Multivariable analysis revealed that expression of RHAMM in >5% of leukemic blasts identifies a subgroup of curatively treated cases with adverse OS independent of failures to achieve complete remission. RHAMM not only represents a promising LAA with specific T-cell responses in AML but, if assessed in situ on blasts, also a probable prognostic factor.     

Prognostic importance of immunophenotyping in adults with acute myelocytic leukaemia: the significance of the stem-cell glycoprotein CD34 (My 10)

A series of 23 monoclonal antibodies reactive with normal lymphoid and myeloid cells at various stages of differentiation were used to characterize 96 adult patients with acute myelocytic leukaemia (AML), concentrating on the possible role the expression of these antigens may have in predicting response to intensive chemotherapy. Only the expression of CD34 (P = 0.008) and HLA-DR (P = 0.035) was significant in predicting response to therapy; patients with leukaemic cells expressing CD34 (My10) had a complete remission (CR) rate of 59% compared to 87% for those with blasts not expressing the antigen. In a multivariate analysis predicting for CR, the expression of CD34, the disease category (de novo AML versus secondary AML [SAML] or a history of antecedent haematological disorder [AHD]), and WBC were significant covariates. Adjusting for disease category and WBC, patients with CD34-positive AML were one-third as likely to enter CR as with those with disease not expressing the antigen (P = 0.066). Comparison of clinical characteristics between the 58 patients whose leukaemia expressed CD34 and the 33 which were CD34-negative found that patients with CD34-positive AML had a higher incidence of SAML and AHD, a lower WBC at diagnosis, and a more frequent incidence of chromosomal abnormalities involving chromosomes 5 and/or 7. Twenty-eight of these patients also had immunophenotyping performed at relapse. Patients who presented with CD34-positive AML, and entered remission, and then relapsed all recurred with CD34-positive leukaemia; there was no case of CD34-positive AML at diagnosis relapsing with CD34-negative disease. In addition, there were patients presenting with CD34-negative AML and then relapsing with CD34-positive AML. These results suggest that intensive cytoreductive therapy is ineffective against CD34-positive AML. Patients who present with CD34-positive AML may require different therapeutic approaches to completely eradicate their disease.     

The Expression Pattern of CD33 Antigen Can Differentiate Leukemic from Normal Progenitor Cells in Acute Myeloid Leukemia

Leukemic stem cells (LSC) in acute myeloid leukemia (AML), defined by CD34 and CD38 antigens also express CD33 similar to normal hematopoietic stem cells. Residual LSC are believed to be responsible for relapse in AML after chemotherapy. Leukemic progenitor cell compartments were defined by CD34 and CD38 expression by flow cytometry in 61 new cases of AML. In each of four compartments thus defined, CD34+CD38−, CD34+CD38+, CD34−CD38− and CD34−CD38+, the pattern and intensity of expression of CD33 were studied in comparison to similar progenitor cell compartments in normal bone marrow and peripheral blood stem cell harvests. Post induction bone marrow samples from 10/61 cases were studied for aberrant CD33 expression. The intensity and pattern of expression of CD33 in AML progenitor cells were significantly different compared to normal progenitor cells. In two cases who were in morphological remission post induction, aberrant CD33 expressing progenitor cells were detectable at a frequency of 1.6 and 0.5 % respectively in the bone marrow. Aberrant CD33 expression in bone marrow LSC identified as CD34+CD38− cells in the CD45 dim/low side scatter region on flow cytometry may be useful as minimal residual disease marker after AML therapy. The method involves the use of a limited number of reagents and can be applied to all cases of AML.     

Correlation between CD34 expression and chromosomal abnormalities but not clinical outcome in acute myeloid leukemia

The hemopoletic stem cell marker CD34 has been reported to be a useful predictor of treatment outcome in acute myeloid leukemia (AML). Previous data suggested that CD34 expression may be associated with other poor prognosis factors in AML such as undifferentiated leukemia, secondary AML (SAML), and clonal abnormalities involving chromosome 5 and 7. In order to analyze the correlations between the clinicopathologic features, cytogenetic and CD34 expression in AML, we retrospectively investigated 99 patients with newly diagnosed AML: 85 with de novo disease and 14 with secondary AML (SAML). Eighty-six patients who received the same induction chemotherapy were available for clinical outcome. Defining a case as positive when ≥ 20% of bone marrow cells collected at diagnosis expressed the CD34 antigen, forty-five patients were included in the CD34 positive group. Ninety patients had adequate cytogenetic analysis. Thirty-two patients (72%) with CD34 positive AML exhibited an abnormal karyotype whereas 15 patients (28%) with CD34 negative AML had abnormal metaphases (P < 0.01). Monosomy 7/7q- or monosomy 5/5q- occurred in 10 patients and 8 of them expressed the CD34 antigen (P < 0.05). All patients with t(8;21) which is considered as a favorable factor in AML had levels of CD34 ≥ 20% (P < 0.05). We did not find any association between CD34 expression and attainment of complete remission, overall survival, or disease-free survival. In conclusion, the variations of CD34 expression in AML are correlated with cytogenetic abnormalities associated both with poor and favorable outcome. The evaluation of the correlations between CD34 antigen and clinical outcome in AML should take into account the results of pretreatment karyotype. © 1996 Wiley-Liss, Inc.     

Immunophenotype of c-kit cells in normal human bone marrow: implications for the detection of minimal residual disease in AML

Summary. In the present study, seven normal human bone marrow samples from healthy volunteers have been analysed in order to investigate the immunophenotypic characteristics of the normal CD117⁺ cells and their utility for the detection of minimal residual disease in 71 acute myeloid leukaemia patients.
Our results show that most of normal BM CD117⁺ cells coexpress the HLADR and the myeloid associated CD33 antigen. In addition, almost half of CD117⁺ cells are CD34⁺, these cells displaying a different FSC/SSC distribution when compared to the CD117⁺/CD34⁻ cells. No CD117⁺/CD15⁺ and CD117⁺/CD10⁺ cells were detected and very few CD117⁺ cells (<1 × 10⁻³) expressing the HLADR⁻/CD34⁻, CD33⁺/HLADR⁻ and CD34⁺/HLADR⁻ phenotypes were found to be present in normal BM. In contrast, from the 71 AML patients analysed, 34 had CD117⁺/CD15⁺ blast cells and eight had the CD117⁺ phenotypes detected at low frequencies (<1 × 10⁻³) in normal BM.
In summary, the present study shows that the use of the CD117 antigen in different monoclonal antibodies combinations may be of great help for the detection of minimal residual disease in a high proportion of AML cases, especially in those patients displaying the CD117⁺/CD15⁺ phenotype, because cells coexpressing both antigens in normal BM, if present, are at very low frequencies.     

Cytokines can reduce clonal, CD34-positive cells in acute myeloid leukemia in vitro

We studied the influence of cytokine mixes on the survival of acute myeloid leukemia (AML) bone-marrow (BM) cells in a 14-day culture assay in vitro. Southern-blot analysis using a panel of different probes in combination with densitometry and flow cytometry were used to detect and compare the amount of clonal or CD34-positive BM cells before and after the culturing procedure. A significant reduction of CD34-positive cells after incubation with a cytokine mix [interleukin (IL)-1β, IL-3, IL-6, stem cell factor (SCF), erythropoietin (EP) with granulocyte macrophage/colony-stimulating factor (GM-CSF, Cytok1] could be achieved in all 16 cases with a CD34-positive blast phenotype studied at diagnosis (P<0.001), in 3 of 10 cases at relapse, and in 8 of 18 cases in complete remission. In healthy donors, an increase of CD34-positive cells was demonstrated in 5 of 5 samples. A reduction of clonal DNA through incubation with Cytok1 was achieved in 5 of 5 (100 %) cases studied at diagnosis, in 1 of 4 (25%) cases at relapse, and in 7 of 9 cases (78%) in complete remission. Cytokine cocktails with GM-CSF (Cytok1) were more efficient in reducing (clonal) CD34-positive cells than cocktails without GM-CSF (Cytok2). AML patients at diagnosis and in complete remission had a better survival probability if their CD34-positive or clonal cells could be reduced in vitro by cytokine cultivation (P<0.05). Vitality of BM cells was not influenced by 14-day cytokine treatment; however, the total cell count could be increased by Cytok1 and Cytok2 by 55–174%, but not by the control medium. Our data show that: (1) clonal cell populations can be regularly detected at diagnosis, during complete remission, and at relapse; (2) CD34-positive cells in AML can be demonstrated to be clonal, gene-rearranged cells; (3) incubation of AML BM-cells with Cytok1 leads to a reduction of the CD34-positive, clonal cell load in all cases at diagnosis and in 78% of the cases in complete remission of AML, but in only 25% of the cases at relapse; (4) in all healthy BM samples, proportions of ‘healthy’ CD34-positive cells were increased. Moreover, absolute cell counts were increased by cytokine incubation of cells obtained at diagnosis, relapse, or complete remission of AML and from healthy donors indicating a selective stimulation of healthy, but not of leukemic CD34-positive cells; (5) cytokine cocktails containing GM-CSF are more efficient in reducing leukemic cells than cocktails without GM-CSF; and (6) in vitro reactivity of clonal or CD34-positive BM cells against Cytok1 has clinical relevance. We conclude, that Southern-blot analysis and flow cytometry are suitable methods to detect and quantify leukemic disease and to distinguish between clonal or non-clonal CD34-positive cells. The ex vivo or clinical application of specific combinations of cytokines might be a feasible and successful application of immunotherapy in AML that merits further investigations. Received: 19 April 1999 / Accepted: 13 January 2000     

CD66 expression in acute leukaemia

Antibodies against CD66 identify antigens from the carcinoembryonic antigen (CEA) family of proteins, which belong to the immunoglobulin gene superfamily. Despite being usually restricted to cells of myeloid or monocytic origin, CD66 expression has also been reported in blasts from children with B-cell lineage acute lymphocytic leukaemia (ALL). An analysis of the CD66 expression was undertaken in a series of acute leukaemia patients. Antigenic expression was analysed using triple combinations of monoclonal antibodies (mAbs) in forty-five patients. The CD66 Kat4 fluorescein isothiocyanate clone was purchased from Dako (Glostrup, Denmark). CD66 was expressed in 2 of 29 patients with AML (acute myeloblastic leukemia) (6.8%) and in 8 of 12 patients with B-cell lineage ALL (66.7%; P <0.001); in blast crisis (BC) of chronic myelocytic leukaemia (CML), CD66 was expressed in two patients with lymphoid BC but not in the two with myeloid BC. The co-expression of CD66 with other myeloid antigens was observed in all CD66+ ALL/Ly-BC cases tested: CD 13 in six patients, CD33 in seven and CD117 in two patients. The CD66 expression is more frequent in ALL than in AML. Furthermore, we analysed minimal residual disease (MRD) in eight patients in complete remission. CD66 expression was associated with an abnormal B-cell differentiation pattern and with increases in CD34/CD19+ cells in all but one case. These findings suggest that an aberrant expression of CD66 could be used to investigate MRD in ALL. The association between CD66 reactivity and bcr-abl in adult ALL remains to be investigated. Received: 31 May 1999 / Accepted: 10 November 1999     

Phase-II trial of idarubicin, fludarabine, cytosine arabinoside, and filgrastim (Ida-FLAG) for treatment of refractory, relapsed, and secondary AML

 The current phase-II trial was initiated to assess the efficacy and toxicity of the Ida-FLAG regimen in patients with poor-risk acute myeloid leukemia (AML). Three subgroups of patients with AML were eligible for the study: (a) refractory, (b) first relapse, or (c) secondary AML (i.e., signs of trilineage myelodysplasia at diagnosis or the history of a myelodysplasia or myeloproliferative disorder). Fifty-seven fully evaluable patients were included in the study. Twenty patients received a second course of Ida-FLAG. Complete remission was achieved by 1/14 patients with refractory AML, 12/15 patients with relapsed AML, and 17/28 patients with secondary AML. The median duration of ANC <1000/μl was 17 days (10–36); of platelets <30,000/μl 23 days (9–65); of days with fever >38.0  °C 6 days (1–33). Thirteen patients (22.8%) died within 42 days of severe infection or hemorrhage. Overall survival at 20 weeks in the subgroups was 24% for patients with refractory, 78% for patients with relapsed, and 55% for patients with secondary AML. The toxicity of the first cycle of Ida-FLAG is moderate. The feasibility and subjective tolerance of the Ida-FLAG regimen are acceptable. There is no evidence for an increase of atypical infections. The efficacy for patients with secondary AML and especially those with first relapse of AML is good, with a high rate of complete remissions. Remission duration seems to be short. Therefore, an intensified post-remission therapy seems necessary. Received: August 28, 1998 / Accepted: April 9, 1999     

Treatment for acute myelocytic leukemia with allogeneic bone marrow transplantation following preparation with BuCy2

One hundred twenty-seven patients with acute myelocytic leukemia (AML) were given busulfan 4 mg/kg on each of 4 days and cyclophosphamide 60 mg/kg on each of 2 days (BuCy2) followed by allogeneic bone marrow transplantation from an HLA-identical or one antigen disparate sibling. For 71 patients in first complete remission, 23 in second complete remission or initial relapse, and 33 patients with primary refractory disease, second or subsequent relapse, or a preceding hematologic disorder, the 3-year leukemia-free survival (LFS) is 63.1%, 32.6%, and 24.2% respectively. The actuarial probability of relapse for each group is 14.1%, 40.6%, and 61.0%. In multivariate analyses, relapse and decreased LFS were associated with advanced disease phase and with M4/M5 French-American-British classification. The LFS of first remission patients was adversely associated with a short time interval from diagnosis to transplantation. This study indicates that BuCy2 is an attractive preparative regimen for marrow transplantation in patients with AML and that prognostic factors for relapse and LFS are similar those described for regimens containing total body irradiation.     

Increased myeloid precursors in regenerating bone marrow; implications for detection of minimal residual disease in acute myeloid leukemia

Presented study is focused on exact immunophenotypic definition of myeloid precursors and their following stages in regenerating bone marrow during treatment of ALL/AML for correct interpretation of the immunophenotype results and proper distinction from minimal residual disease (MRD) by multiparameter flow cytometry. This study includes bone marrow samples from 36 controls, 27 patients with AML, 39 patients with B-ALL undergoing therapy who remained in complete remission after treatment and also 30 B-ALL patients one year after the end of therapy. We observed substantial expansion of immature bone marrow populations in the regenerating bone marrows, which were identified by expression of CD34 and/or CD117 markers by 4-color flow cytometry. Myeloid precursors were significantly increased after cessation of induction therapy cycle of B-ALL (1.27+/-2.04%, p=0.0064) and also AML patients (0.87+/-0.77%, p=0.001), but also during follow-up of B-ALL patients (1.42+/-2.36%, p=0.0001) when compared with non-treated controls (0.38+/-0.29%). Some cases where their frequencies achieved up to 12% reflect the massive regeneration of myeloid lineage in bone marrow after chemotherapy cycles. Especially in these cases accurate interpretation of such a high frequency of immature myeloid cells as myeloid precursors was very important to exclude incoming relapse or secondary leukemia. The myeloid precursors represented by CD34+ in regenerating bone marrow expressed CD45 (94.8+/-5.5%), CD117 (38.3+/-26.2%), CD38 (91.4+/-5.7%), HLA-DR (90.6+/-7.6%), CD13 (73.0+/-20.8%) and CD33 (85.2+/-15.6%), while CD90 (2.7+/-2.5%), CD133 (10.0+/-8.2%) and T or B lymphocyte markers were negative. Comparing immunophenotypes with control bone marrows, only difference in expression of CD33 marker was found (85.2+/-15.6% versus 63.0+/-17.4% p=0.024). In addition, according to expression of these markers three different subsets of myeloid precursor cells were identified in regenerating bone marrow samples: CD34+ CD117- HLA-DR+, CD34+ CD117+ HLA-DR+ and CD34- CD117+ HLA-DR-/+ without aberrant marker expression. In conclusion for the correct discrimination of MRD in acute leukemia it is indispensable to define the range of normality in myeloid differentiation by extensive studies of bone marrows not only from healthy donors but also from regenerating bone marrow of patients undergoing therapy.     

Successful treatment of B-cell lymphoma associated with hemophagocytic syndrome using autologous peripheral blood CD34 positive cell transplantation followed by induction of autologous graft-versus-host disease

A 56-year-old man who presented with persistent high fever and abdominal pain was diagnosed as having a B-cell lymphoma associated with hemophagocytic syndrome (B-LAHS). As post-remission therapy, the patient was treated with high-dose chemoradiotherapy followed by infusion of autologous CD34+ cells that had been isolated from the peripheral blood buffy coat. Cyclosporin and interferon (IFN)-γ were administered to induce autologous graft-versus-host disease (GVHD). Hematopoietic recovery promptly occurred and skin GVHD developed on day 26 after CD34+ cell transplantation. The patient has been in complete remission without therapy for 20 months since transplant. Autologous CD34+ cell transplantation in combination with induction of autologous GVHD may be efficacious in obtaining a cure for B-LAHS. Received: 19 April 1999 / Accepted: 14 December 1999     

Variability in responsiveness to lovastatin of the primitive CD34+ AML subfraction compared to normal CD34+ cells

In the present study, we questioned whether the cholesterol synthesis inhibitor lovastatin potentiates the cytotoxicity of chemotherapeutic agents in the primitive CD34⁺ subpopulation of acute myeloid leukemia (AML) cells. AML mononuclear cells (n = 17) were sorted in CD34⁺ and CD34⁻ fractions and compared to normal CD34^+/− cells (n = 7). The percentage of surviving cells upon exposure to lovastatin (25–100 μM) and/or chemotherapeutics (cytarabin or daunorubicin) was determined with a luminescent cell viability assay. The results demonstrate that the primitive CD34⁺ subpopulation of normal and AML cells displayed a higher sensitivity to lovastatin than the more mature CD34⁻ subpopulation. The combination of lovastatin and chemotherapeutics resulted in a more pronounced inhibitory effect on both subpopulations. In contrast to the homogeneous results in normal CD34⁺ cells, a distinct heterogeneity in lovastatin sensitivity was found in AML samples. Therefore, a group of normal (n = 11) and abnormal (n = 6) responders were identified based on a reduced or increased cell survival compared to normal CD34⁺ cells. This distinction was not only observed in the CD34⁺ AML subfraction but also in CD34⁺CD38⁻AML cells. In the abnormal responder group, 50% of patients presented with unfavorable cytogenetics and significant higher peripheral blast cell counts, which coincided with poor treatment results. In summary, the findings indicate that the primitive subfraction of CD34⁺ AML cells is in the majority of cases affected by lovastatin treatment, which is potentiated when combined with chemotherapeutics. Heterogeneity of the response observed in AML patients allowed identification of a subgroup with poor prognosis.     

Prognostic impact of the CD34+/CD38− cell burden in patients with acute myeloid leukemia receiving allogeneic stem cell transplantation

In acute myeloid leukemia (AML), leukemia‐initiating cells exist within the CD34+/CD38? cell compartment. They are assumed to be more resistant to chemotherapy, enriched in minimal residual disease cell populations, and responsible for relapse. Here we evaluated clinical and biological associations and the prognostic impact of a high diagnostic CD34+/CD38? cell burden in 169 AML patients receiving an allogeneic stem cell transplantation in complete remission. Here, the therapeutic approach is mainly based on immunological graft‐versus‐leukemia effects. Percentage of bone marrow CD34+/CD38? cell burden at diagnosis was measured using flow cytometry and was highly variable (median 0.5%, range 0%–89% of all mononuclear cells). A high CD34+/CD38? cell burden at diagnosis associated with worse genetic risk and secondary AML. Patients with a high CD34+/CD38? cell burden had shorter relapse‐free and overall survival which may be mediated by residual leukemia‐initiating cells in the CD34+/CD38? cell population, escaping the graft‐versus‐leukemia effect after allogeneic transplantation. Evaluating the CD34+/CD38? cell burden at diagnosis may help to identify patients at high risk of relapse after allogeneic transplantation. Further studies to understand leukemia‐initiating cell biology and develop targeting therapies to improve outcomes of AML patients are needed.     

Intensive chemotherapy with idarubicin, ara-C, etoposide, and m-AMSA followed by immunotherapy with interleukin-2 for myelodysplastic syndromes and high-risk Acute Myeloid Leukemia (AML)

 Intensive chemotherapy followed by treatment with interleukin-2 (IL-2) was evaluated in a prospective, randomized, multicenter trial including 18 patients with refractory anemia with excess of blasts in transformation (RAEB-T), 86 patients with acute myeloid leukemia (AML) evolving from myelodysplastic syndromes, and six patients with secondary AML after previous chemotherapy. Median age was 58 years (range: 18–76 years). Forty-nine patients (45%) achieved a complete remission (CR) after two induction cycles with idarubicin, ara-C, and etoposide, 52% of them aged ≤60 years and 35% aged >60 years (p=0.06). After two consolidation courses, patients were randomized to four cycles of either high- or low-dose IL-2. Patients aged up to 55 years with an HLA-identical sibling donor were eligible for allogeneic bone marrow transplantation. The median relapse-free survival was 12.5 months, with a probability of ongoing CR at 6.5 years of 19%. Overall survival of all patients was 8 months, and 21 months for the CR patients. Median survival was significantly longer among patients aged ≤60 years than among the older patients (16 vs 6 months, p<0.001). Median duration of survival and relapse-free survival were not statistically different in the two IL-2 treatment arms. Received: March 23, 1999 / Accepted: June 23, 1999     

Different organization of von Willebrand factor oligomers in type-2A and -2B von Willebrand disease variants: effects of DDAVP infusion and protease inhibitors

The existence of leukemic-associated phenotypes has been suggested to be a valuable tool for the detection of minimal residual disease (MRD) in AML patients, as they would allow to distinguish leukemic blast cells from normal hematopoietic progenitors. The present study was designed to analyze in which proportion of AML patients the immunological detection of MRD is feasible, based on the presence of aberrant phenotypes that allow the distinction of leukemic from normal cells. For this purpose we have prospectively investigated the blast cells from 40 AML patients at diagnosis with a large panel of MoAb in double and triple staining combinations analyzed at flow cytometry, in order to detect aberrant phenotypes on blast cells (lineage infidelity, antigenic overexpression, and asynchronous antigenic expression, as well as aberrant lightscatter pattern). In the analysis of the 40 AML cases more than one blast cell subset, distinguished by its different antigenic expression, was detected in 85% of the patients: five different phenotypic blast cell subsets were observed in six cases, four in 13 patients, three subsets in three cases, and two in 12 patients; only six cases showed a homogeneous phenotypical blast cell population. Twenty-nine of the 40 AML cases analyzed (73%) showed the existence of at least one aberrant phenotype: in 15 cases the myeloid blast cells co-expressed lymphoid-associated antigens (CD2, CD5, CD7, and/or CD19) - lineage infidelity -; asynchronous antigen expression was detected in 25 patients (CD34+CD56+, CD34+CD11b+, CD34+CD14+, CD117+CD15+, CD33-CD13+, CD13-CD15+, HLADR+CD15+++, HLADR-CD14+CD11b+ CD4+); seven cases displayed antigen overexpression (CD13, CD33, CD15, or CD14); and in 13 patients leukemic cells had an abnormal FSC/SSC distribution according to their phenotype. These results suggest that immunological methods for the detection of MRD based on the existence of aberrant phenotypes could be used in the majority of AML patients.     

Primary cutaneous marginal center lymphoma – complete remission induced by interferon α2a

Marginal zone lymphoma (MZL) is a distinct entity among B-cell lymphomas. We report on a 53-year-old woman who developed disseminated primary cutaneous MZL with secondary lymph node involvement and perinodular spreading. The tumor cell phenotype was characterized as CD20/CD79a/κ/λ+/bcl-2-positive, CD3/5/15/39/bcl-1-negative. Ki-67 was expressed by 20–35% of tumor cells. There was no evidence of systemic (including bone marrow) involvement. The diagnosis of MZL with plasmacellular differentiation (Stage IVa) was made. The patient was treated with interferon α2a injected s.c. at 9 × 10⁶ U 3 days a week for 1 year. During this time the skin lesions completely disappeared. No evidence of lymph node or extracutaneous disease was found. The patient remains in complete remission. Side effects were only of grade I (WHO); the Karnovsky index was 90%. As shown for other types of primary cutaneous B-cell lymphoma, prolonged interferon α monotherapy may be effective in controlling the disease and/or inducing complete remission in MZL. Received: 11 December 1998 / Accepted: 13 January 1999