In vitro down-regulation of bcl-2 expression by all-trans retinoic acid in AML blasts

 Using flow cytometry, we have investigated the effects of 0.5 μM all-trans–retinoic acid (ATRA) on bcl-2 expression in the blast cells of 25 acute myeloblastic leukemia (AML) patients and the HL-60 cell line after incubation for 6 days. We observed a significant decrease of bcl-2 expression after treatment with ATRA in 12 of 25 AML samples and the HL-60 cells. The mean fluorescence intensity (MFI) ratio for the bcl-2 levels of the ATRA responders (n=12) was reduced to 7.9±4.8 following incubation with ATRA compared with 10.9±6.5 (mean±SD) for control samples incubated without ATRA (p=0.011). There was no significant difference between the baseline bcl-2 MFI ratio in the ATRA responders (11.14±7, n=12) and the non responders (14.18±11.3, n=13;p=0.432). The down-regulation of bcl-2 expression by ATRA was not significantly associated with CD34-negative or -positive AML. There was no correlation between AML subtypes and regulation of bcl-2 expression by ATRA. Complete remission and overall survival were not significantly improved in bcl-2 down-regulated cases. Our data confirm that ATRA can down-regulate the bcl-2 expression in AML blasts. Because many chemotherapeutic agents also operate through the activation of programmed cell death and bcl-2 levels are positively associated with resistance to apoptosis, ATRA can be used in combination chemotherapy to increase the chemosensitivity of some patients with AML.     

Comparative quantitative expression of bcl-2 by normal and leukaemic myeloid cells

Summary. Expression of the bcl-2 oncoprotein by AML blasts has previously been demonstrated to be heterogenous with high levels of bcl-2 expression being associated with a low complete remission rate and poor survival. We have quantified bcl-2 expression in AML blasts in relation to expression of the CD34 antigen and in comparison to CD34-positive cells from normal bone marrow. When expressed as molecules of equivalent soluble fluorochrome (MESF) per cell, AML blast cell bcl-2 expression varied from 11.1 to 99.9 × lO³ (median 39.4 × 10³, n=56) with 28.5% of patients expressing high MESF values (>50 × 10³) and 16% of patients expressing low MESF values (<20 × 10³), the remainder expressing intermediate values. There was no significant difference between intensity of bcl-2 expression and FAB classification in the de novo AML cases, and there was no significant differences between de novo and secondary AML cases. Blasts from CD34⁺ AML patients expressed significantly higher levels of bcl-2 (mean MESF 43.6 × 10³, n =36) than CD34^? AML patients (mean MESF 31.7 × 10³, n=19). In five cases of CD34⁺ AML, bcl-2 expression was determined on purified CD34⁺ and CD34^? blast cell populations. In all cases CD34⁺ blasts were found to express significantly higher bcl-2 MESF values compared to the CD34^? fraction. Purified CD34⁺ cells from normal bone marrow consistently expressed high levels of bcl-2 (MESF >75 × 10³ n = 4), which was comparable to that found on CD34⁺ AML cells. Our results suggest that the poor prognosis previously associated with AML blasts expressing the CD34 antigen may in part be related to high expression of bcl-2. Also the ability to measure bcl-2 in AML blasts quantitatively by flow cytometry and to categorize patients into discrete groups may be of value as a prognostic indicator in AML.     

Nucleoside transporters,bcl-2 and apoptosis in CLL cells exposed to nucleoside analogues in vitro

The purine nucleoside analogues fludarabine (Fl) and chlorodeoxyadenosine (2-CdA) are considered to be cell cycle specific agents which require DNA synthesis for cytotoxicity. However, their efficacy in the treatment of CLL, an indolent lymphoid malignancy suggests additional mechanisms of action. Like cytosine arabinoside (AraC), Fl and 2-CdA gain access to the cell via a specific nucleoside transporter (NST) protein. To investigate the mode of action of these drugs in CLL, we used a fluorescent ligand for the NST (5‘-(SAENTA- x 8)-fluorescein) and 3-colour flow cytometry to determine NST expression on CD5⁺/CD19⁺ B-cells from the peripheral blood (PB) of patients with CLL. NST levels on these cells was found to be not significantly different from normal control lymphocytes (mean = 485±425) vs. (mean = 553±178). Exposure to varying concentrations (0, 3 μM and 30 μM) of Fl and 2-CdA, however, resulted in an upregulation of NST (mean = 1552±775 with 30 μM FL; mean = 3392±2197 with 30 μM 2-CdA) after 48 h. “Large” lymphoid cells (not present in normal PB) were found to express significantly more NST (mean = 2540±2861) and have a higher proliferative capacity than “small” cells (mean = 357±517 NST/cell). Incubation of CLL cells with Fl (n = 6) and 2-CdA (n = 8) in vitro over 48 h also resulted in an increase in the proportion of cells in S-phase (0 μM = 0.2±0.1; 30 μM FL = 2.4±2.0; 30 μM 2-CdA = 3.3±1.3) and a significant increase in morphologically identifiable apoptosis. Apoptosis was confirmed by flow cytometric DNA analysis (0 μM = 13±8%; 30 μM FL = 40±20%; 30 μM 2-CdA = 48±11%). In situ hybridization using a biotinylated cDNA bcl-2 probe demonstrated that bcl-2 mRNA expression was markedly decreased in treated cells after 24 h. These studies have demonstrated that: (1) NST expression on CLL lymphocytes is low; (2) in vitro exposure to the analogues increases both the level of NST expression and the % cells in S-phase; (3) exposure to the analogues downregulates bcl-2 expression and increases apoptosis.     

Quantitation of resistance to cytosine arabinoside by myeloid leukemic cells expressing bcl-2

Abstract: The presence of bcl-2 in myeloid leukemias has been associated with a decrease in therapy-induced apoptosis, reduced patient survival and in vitro autonomous growth of leukemic cells. The present study focuses on the quantitation of resistance to increasing doses of 1-β-d-arabinofuranosylcytosine (Ara-C) by using hematological tumors expressing different levels of bcl-2. Scanning densitometry of Western blots demonstrated that the myeloid U-937 cells express low levels of bcl-2 (RD=0.008), whereas the follicular lymphoma RL-7 expressed very high levels (RD=3.084). Colony formation was also examined following incubation with Ara-C and RL-7 cells demonstrated a higher clonogenic survival (LD₅₀=0.5 μm) when compared with U-937 cells (LD₅₀=0.005 μm ). Similarly, the level of bcl-2 expression in each cell line was also related to apoptosis with U-937 cells demonstrating increased DNA fragmentation when compared with RL-7 cells. To further evaluate the effect of upregulated bcl-2 on Ara-C treatment, U-937 cells were transfected with a retroviral vector carrying the murine bcl-2 or vector alone. Upregulation of bcl-2 by myeloid leukemic cells increased the resistance by 3 logs to Ara-C when comparing LD₅₀ values from clonogenic assays, and decreased apoptosis by at least 3 logs when measuring dUTP positive cells by flow cytometry.     

Inv(16) acute myeloid leukemia cells show an increased sensitivity to cytosine arabinoside in vitro

Abstract: Karyotype represents the major independent prognostic factor for response and remission duration in acute leukemia. In particular, it has been reported that acute myeloid leukemia (AML) patients with inv(16) abnormality show a better prognosis, especially in case of treatment with high-dose Ara-C (HD Ara-C) containing regimens. In this study we aimed at testing whether leukemic cells from patients showing the inv(16) were more sensitive to Ara-C in vitro, compared to AML blasts from patients with normal karyotype or chromosomal abnormalities other than t(15;17) or t(8;21). We analyzed blast cells from 30 patients who were diagnosed and treated in our institution. The IC₅₀ of Ara-C, as tested by the XTT colorimetric assay, was significantly lower in cases with inv(16) (18.5±15.88 μmol/l vs. 38±14.6 μmol/l, in cases with other abnormalities, p = 0.01). This result was confirmed by a higher incorporation of [³H]-Ara-C into DNA (p = 0.02 and p = 0.001 compared to samples with normal and abnormal karyotype, respectively). All the same, Ara-C induced apoptosis was significantly increased in cells from patients with inv(16). Our data suggest a possible interaction between the molecular background of inv(16) and a modification of intracellular metabolism of Ara-C, and could thus provide a rationale for HD-Ara-C-based schedules for patients with inv(16) AML.     

The putative role of arylsulfatase in interleukin-2- mediated cytotoxicity and interleukin-7-mediated bactericidal activity of natural killer cells

 We have examined the cytolytic and bactericidal activity of resting and cytokine-stimulated natural-killer (NK) cells against K562 and Daudi cell lines and Escherichia coli, respectively. Unstimulated NK cells showed considerable cytolytic activity against K562 (64±4%) and relatively low activity against the Daudi cell lines (22±9%). Pretreatment of NK cells with the arylsulfatase (AS) type-II-specific inhibitor NaH₂PO₄ reduced cytotoxicity towards K562 and Daudi 1.3- and 2.9-fold (p<0.05;n=12), respectively, indicating that AS participates in NK-mediated cytotoxicity. Interleukin-2 (IL-2) (200 units/ml) caused a 1.3- and 3.5-fold (p<0.5;n=12) enhancement of NK cytotoxic activity against K562 and Daudi, respectively. Pretreatment of these cells with the AS type-II-specific inhibitor NaH₂PO₄ reduced cytotoxicity 1.1-fold towards K562 (p>0.05;n=12) and 1.2-fold towards Daudi (p>0.05;n=12) indicating that AS does not participate in IL-2-mediated NK cytolytic activity against these cell lines. IL-7 (3 units/ml) did not cause any enhancement of NK cytolytic activity. Unstimulated NK cells showed considerable bactericidal activity against E. coli (23±4%). Incubation of resting NK cells with NaH₂PO₄ reduced the bactericidal effect only by 1.09-fold (p>0.05;n=12), indicating that AS does not mediate this effect. IL-2 (200 units/ml) and IL-7 (3 units/ml) enhanced the bactericidal activity 1.5- and 2.2-fold, respectively (p<0.05;n=12). This effect was not influenced by incubation of IL-2-stimulated cells with NaH₂PO₄, indicating that AS does not participate in the IL-2-mediated NK bactericidal effect. IL-2 seems to exert its stimulatory effect upon NK-mediated bactericidal activity by a different, non-AS-dependent mechanism. However, incubation of IL-7-stimulated NK cells with NaH₂PO₄ reduced the NK bactericidal effect by 1.2-fold (p<0.05;n=12), indicating that AS may have a role in this reaction. These data can be further confirmed by detection of AS through degranulation of NK cells, showing that IL-2 induced only mild degranulation of resting and f-MLP-stimulated NK cells (26±1% vs 22±2% and 31±2% vs 29±2, respectively) (p>0.05;n=8). In contrast, IL-7 showed significant enhancement of AS release in resting or f-MLP-induced NK cells (36±3% vs 22±2% and 49±3% vs 29±2%, respectively) (p<0.05;n=8). Received: 13 August 1996 / Accepted: 15 November 1996     

Expression and functional role of urokinase-type plasminogen activator receptor in normal and acute leukaemic cells

Urokinase-type plasminogen activator receptor (UPA-R-CD87) is a GPI-anchored membrane protein which promotes the generation of plasmin on the surface of many cell types, probably facilitating cellular extravasation and tissue invasion. A flow cytometric quantitative analysis of expression levels for UPA-R was performed on fresh blast cells from patients with acute myeloid leukaemia (AML, n = 74), acute lymphoblastic leukaemia (ALL, n = 24), and biphenotypic leukaemia (BAL, n = 3) using two CD87 monoclonal antibodies (McAbs) (3B10 and VIM5). Peripheral blood and bone marrow (BM) cells from 15 healthy adults served as controls. Using 3B10 McAb, UPA-R was expressed (>99%) by blood monocytes, neutrophils, and BM myelomonocytic precursors in controls, whereas resting T and B lymphocytes, and CD34⁺ cells were UPA-R negative. We also attempted to clarify whether UPA-R has a role in mediating neutrophil functions. Oriented locomotion induced by different chemotaxins and lysozyme release by granules stimulated with fMLP or PMA were significantly decreased when UPA-R was neutralized by CD87 McAb. In contrast, the anti-UPA-R McAb had no effect on superoxide anion generation of normal neutrophils. Blasts from AML showed a heterogenous pattern of expression for the UPA-R McAbs, with reactivity strictly dependent on FAB subtype. The highest UPA-R expression was seen in the M5 group: all patients tested (n = 20) showed strong positivity for the UPA-R McAb whereas only 12% (3/24) of ALL patients were CD87 positive, and 2/3 of BAL patients showed a dim expression for CD87. The number of receptors expressed by blast cells in 6/74 (8.1%) AML patients was higher than those of normal samples; in addition, since co-expression of UPA-R and CD34 was not found in normal haemopoietic cells, it may be postulated that CD87 can be used alone (when overexpressed) or in combination with CD34 for the detection of minimal residual disease. Results also indicated that patients with UPA-receptors >12 × 10³ ABC/cell, irrespective of FAB subtype, had a greater tendency for cutaneous and tissue infiltration and a higher frequency of chromosome abnormalities, thus suggesting the concept that cellular UPA-R content positively correlates with the invasive potential of AML cells. The combination of higher UPA-R positivity, abnormalities of chromosome 11, and M5 FAB morphology may identify a peculiar subset of AML, characterized by a more aggressive clinical course.     

Negative CD19 expression is associated with inferior relapse-free survival in children with RUNX1-RUNX1T1–positive acute myeloid leukaemia: results from the Japanese Paediatric Leukaemia/Lymphoma Study Group AML-05 study

We performed a retrospective analysis of leukaemic surface antigen expression and genomic data from a total of 100 RUNX1-RUNX1T1–positive paediatric acute myeloid leukaemia (AML) patients enrolled in the Japanese Paediatric Leukaemia/Lymphoma Study Group (JPLSG) AML-05 protocol to determine risk factors for relapse. In univariate analysis, the KIT exon 17 mutation (n = 21) and CD19 negativity (n = 59) were significant risk factors for relapse (P = 0·01). In multivariate analysis, CD19 negativity was the sole significant risk factor for relapse (hazard ratio, 3·09; 95% confidence interval, 1·26–7·59; P < 0·01), suggesting that biological differences between CD19-positive and CD19-negative RUNX1-RUNX1T1 AML patients should be investigated.     

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.     

High expression of Bcl-2 protein in acute myeloid leukemia cells is associated with poor response to chemotherapy

Flow cytometric expression of bcl-2 protein was analyzed in 67 newly diagnosed acute myeloblastic leukemia (AML) patients using an anti-bcl-2 monoclonal antibody by direct immunofluorescence technique and results were correlated with FAB subtype, CD34 expression and clinical outcome. The number of bcl-2+ cells in each sample was heterogenous (range, 19% to 96%), with a mean of 81%. The percentage of bcl-2+ cells was higher in M0 and M1 types according to French-American-British classification. The mean fluorescence index (MFI), expressed as the ratio of sample channel:control mean channel was significantly higher (p=0.01) in M0 (19.0) and M1 (17.6) than M4 (11.7) and M5 (8.9) cytotypes. In addition, bcl-2 MFI significantly correlated both with CD34 positivity and with CD34 MFI. High percentage expression of bcl-2 and MFI index of bcl-2 was associated with a low complete remission rate after intensive chemotherapy (40.4% in cases with 20% and more positive cells vs 72% in cases with less than 20% positive cells). By statistical analysis we also demonstrated that both bcl-2 high MFI (>16) and CD34 expression are independent prognostic factors for achieving CR in AML.     

The expression of co-stimulatory molecules and their relation- ship to the prognosis of human acute myeloid leukaemia: poor prognosis of B7-2-positive leukaemia

We examined the expression of co-stimulatory molecules on leukaemic cells of 52 adult patients with acute myeloid leukaemia (AML) (34 men and 18 women) and analysed the relationship between these expressions and the patient's prognosis. B7-1 was not expressed in any of the 23 patients investigated, whereas B7-2 was expressed in 26/52 patients (50.0%). B7-2 was expressed in all AML patients with monocytic morphology (M4 or M5) and in 16/42 cases without monocytic morphology. CD54 was expressed in 28/37 patients examined (75.7%), and CD58 was expressed in all of the AML patients except one (M7). The overall survival of the 26 B7-2-positive leukaemia patients (1–24 months, median survival 11.5 months) was significantly shorter than that of the 26 B7-2-negative leukaemia patients (1–71+ months, median 35.1 months) (P = 0.0080). In addition, the B7-2-positive patients exhibited significantly shorter disease-free survival periods compared to the B7-2-negative patients (P = 0.021). There was no significant difference in age, sex, haematological data and complete remission rate between the B7-2-positive and B7-2-negative patients. Our results indicated that B7-2 is one of the most crucial factors in the prognosis of adult acute leukaemia and can be expected to have an important role in tumour immunity.     

Results of conventional-dose cytosine arabinoside and idarubicin in elderly patients with acute myeloid leukemia

Summary Conventional-dose Ara-C (200 mg/m² d 1–5) combined with idarubicin (12 mg/m² d 1–3) was employed as remission induction and consolidation therapy in 23 elderly AML patients with a median age of 66 years (range, 60–75) with AML according to the FAB criteria (M1n=3, M2n=10, M4n=6, M5n=2, M6n=2), eligible for the study. In seven patients earlier MDS had been documented by previous bone marrow aspirates. The CR rate after one induction course was 65% (15/23). Toxicity was acceptable, with four patients dying during the chemotherapy-induced hypoplasia (4/23). Although 80% of the CR patients received two additional cycles of Ara-C and idarubicin as consolidation therapy, only two patients are still in continuous complete remission more than 12 months after achieving CR. The median disease-free survival of the CR patients was 11.5 months and the median survival of the entire group was 10 months. We conclude that conventional dose Ara-C/idarubicin is an effective protocol for inducing complete remission in elderly patients with AML, but that consolidation therapy consisting of two courses of the same regimen does not produce a relevant rate of long-term disease-free survival.     

A comparison of busulphan versus total body irradiation combined with cyclophosphamide as conditioning for autograft or allograft bone marrow transplantation in patients with acute leukaemia

We retrospectively compared the outcome in patients in the EBMT database transplanted for acute leukaemia from January 1987 to January 1994 who received busulphan and cyclophosphamide (BU/CY) as a pretransplant regimen versus those who received cyclophosphamide and total-body irradiation (CY/TBI). The patients were matched for type of transplant (autologous bone marrow transplantation (ABMT) versus allogeneic (BMT)), diagnosis (acute lymphoblastic leukaemia (ALL) or acute myeloid leukaemia (AML)), status (early (first complete remission, CR-1) versus intermediate (second or later remission, first relapse)), age, FAB classification for AML, prevention of graft-versus-host disease and year of transplantation. In ABMT recipients (matched paired 530 × 2) with ALL CR-1, AML CR-1 and AML intermediate disease, transplant-related mortalities (TRM), relapse incidence (RI) and leukaemia-free survival (LFS) did not differ significantly in patients treated with BU/CY or CY/TBI. However, in ABMT recipients with ALL intermediate disease, the probability of relapse was 82 ± 5% (±95% confidence interval) in the BU/CY group compared to 62 ± 6% in the CY/TBI group (P = 0.002) and the 2-year leukaemia-free survival 14 ± 4% and 34 ± 6%, respectively (P = 0.002). In BMT recipients of bone marrow from HLA-identical siblings (matched paired 391 × 2), the TRM, RI and LFS did not differ significantly between the two treatments in all groups. In particular, the 2-year LFS in patients with AML CR-1 was 64 ± 3% in those treated with BU/CY (n = 237) compared to 66 ± 3% in those given CY/TBI (n = 237). In all groups the findings were confirmed in a multivariate analysis of prognostic factors. Veno-occlusive disease (VOD) of the liver (P < 0.05) and haemorrhagic cystitis (P < 0.001) was more common in the BU/CY group compared to the CY/TBI group for ABMT and BMT patients. In conclusion, BU/CY and CY/TBI as pretransplant regimens gave similar results in all situations, except ABMT for ALL intermediate stages with more than 2 years from diagnosis to transplantation, where a lower RI and a higher LFS were associated with CY/TBI.     

Abnormal surface markers expression on bone marrow CD34<Superscript>+</Superscript> cells and correlation with disease activity in patients with systemic lupus erythematosus

Defects of hematopoietic stem cells (HSCs) have been suggested to contribute to the development of systemic lupus erythematosus (SLE). The aim of this study was to investigate the phenotypic characteristics of bone marrow (BM) CD34⁺ cells in patients with SLE and its relationship with SLE disease activity. Ten SLE patients and 10 healthy subjects were recruited and their BM CD34⁺ cells were analyzed by flow cytometric analysis with CD45/SSC gating for the expression of CD90, CD95, CD117, CD123, CD164, CD166, FAS-L, and HLA-DR. The percentage of BM CD34⁺ cells was significantly decreased in active SLE patients (1.48 ± 0.41%, n = 7) compared to the healthy controls (2.31 ± 0.75%, n = 10, p < 0.01), but no significant difference was found between the inactive patients (2.04 ± 0.44%, n = 3) and the controls. The expression of CD95, CD123, and CD166 on BM CD34⁺ cells were significantly increased in SLE patients (48.31 ± 10.59%, 44.9 ± 21.5%, 30.9 ± 19.54%, respectively, n = 10) when compared with the control subjects (24.33 ± 11.1%, 19.5 ± 4.4%, 10.7 ± 5.5%, respectively, n = 10, p < 0.05). The increased CD123 expression was negatively correlated with the number of peripheral white blood cells (r = −0.700, p < 0.05, n = 10). The percentage of CD166 expression was found significantly correlated with the index of SLE disease activity (r = 0.472, p < 0.05, n = 10) and 24 h proteinuria (r = 0.558, p < 0.05, n = 10), but negatively correlated with serum C3 level (r = −0.712, p < 0.01, n = 10). Our study found that the surface marker expression of CD95, CD123, and CD166 on BM CD34⁺ cells were significantly increased in patients. This supports the hypothesis that there are abnormalities of the HSC in SLE. Since CD166 and CD123 correlated with the overall lupus activity, their role as a biomarker of inflammatory disease activity also requires further study.     

Contrasting in vitro effects for the combination of fludarabine, cytosine arabinoside (Ara-C) and granulocyte colony-stimulating factor (FLAG) compared with daunorubicin and Ara-C in P-glycoprotein-positive and P-glycoprotein-negative acute myeloblastic leukaemia

It has been suggested that the FLAG remission induction regimen comprising fludarabine (F-ara), cytosine arabinoside (Ara-C) and granulocyte colony-stimulating factor (G-CSF) may be capable of overcoming P-glycoprotein (P-gp)-related multidrug resistance (MDR) in patients with acute myeloblastic leukaemia (AML). We have investigated the in vitro response of P-gp-positive and -negative AML clones to FLAG and compared this with their response to treatment with Ara-C and daunorubicin (DNR). Twenty-four cryopreserved samples from patients with AML were studied using a flow cytometric technique for the enumeration of viable (7-amino actinomycin D negative) cells. Samples consisted of 12 P-gp-positive and 12 P-gp-negative cases, as measured by the MRK16 antibody. The results were analysed by calculating the comparative drug resistance (CDR), i.e. the percentage cell death caused by Ara-C + DNR subtracted from the percentage cell death, caused by FLAG after 48 h incubation in suspension culture. P-gp-positive clones were shown to have a significantly higher CDR than P-gp-negative clones (P = 0. 001). Furthermore, a significant positive correlation (r2 = 0.40, P < 0.01) was found between P-gp protein expression and CDR. However, P-gp function, measured using cyclosporin modulation of rhodamine 123 (R123) uptake, was not associated with the CDR, demonstrating that there are other properties of P-gp, besides its role in drug efflux, that modulate the responsiveness of AML blasts to chemotherapy. These results are consistent with a potential benefit for FLAG in P-gp-positive AML, but not P-gp-negative AML, compared with standard anthracycline and Ara-C therapy.     

Multiparametric analysis of apoptotic and multi-drug resistance phenotypes according to the blast cell maturation stage in elderly patients with acute myeloid leukemia.

BACKGROUND AND OBJECTIVES: Acute myeloid leukemia (AML) is a heterogeneous group of malignant diseases, often characterized by coexistence of more than one subpopulation of blast cells. Multiparametric flow cytometry immunophenotyping has proven to be a reliable and sensitive approach for the discrimination of myeloid blast cells from residual normal cells present in bone marrow samples from AML patients and, at the same time, allows the identification of different maturation compartments among myeloid blasts. Therefore, it provides a unique tool for assessing apoptotic and multidrug resistance (MDR)-associated phenotypes in individual subsets of leukemic cells. DESIGN AND METHODS: The aim of the present study was to explore the simultaneous expression of proteins related to both apoptosis (APO2.7, bcl-2, bax) and multidrug resistance (MDR1, MRP, LRP) in the different blast cell subpopulations detected at diagnosis in a group of 72 elderly patients with AML. In addition, we included 5 bone marrow samples from healthy adult donors in the analysis. RESULTS: Immature blast cells (CD34+: subset I) showed a significantly higher level of bcl-2 expression (p <0.0001) together with a lower reactivity for APO 2.7 (p=0.02) as compared to the other more mature CD34- cell subsets. The expression of Bax parallelled that of APO 2.7, although the difference between immature CD34+ blast cells and the mature blast cell subsets did not reach statistical significance (p=0.18). These results translated into a significantly (p<0.0001) higher bcl-2/bax ratio for the CD34+ blast cells as compared to that of the two CD34- blast cell subpopulations. Regarding the expression of the multidrug resistance-associated proteins Pgp and MRP, CD34+ blast cells displayed a greater expression of both proteins as compared to the more mature CD34- AML blast cells, but differences according to maturation stage of AML blast cells did not reach statistical significance. In contrast, LRP expression was significantly lower in the more immature CD34+ blast cell subset than in the more mature ones (p=0.01). INTERPRETATIONS AND CONCLUSIONS: As far as normal bone marrow is concerned our results suggest that all blast cell subpopulations are more protected from apoptosis than their normal counterparts. We conclude that in elderly patients with AML the more immature blast cells are more resistant to apoptotic processes, which could explain why, when AML relapses, the blast cells frequently display a more immature phenotype than that observed at diagnosis. Contradictory results in multidrug resistance profile support the hypothesis that failure to respond to chemotherapeutic drugs in AML is a multifactorial phenomenon.     

Mobilization of Philadelphia-negative peripheral blood progenitor cells with chemotherapy with rhuG-CSF in chronic myelogenous leukaemia patients with a poor response to interferon-alpha

The purpose of this cooperative study was to evaluate the quantity and quality of Ph¹-negative progenitor cells mobilized in the peripheral blood of patients with chronic myelogenous leukaemia soon after aplasia induced by chemotherapy. 32 patients ineligible for allografting who were cytogenetically refractory to interferon-alpha (IFN-α) were entered into this study. The chronic phase varied widely, with a median duration of 17 months (range 3–90 months). All patients were treated with intensive conventional chemotherapy regimens and recombinant human granulocyte colony-stimulating factor (rhuG-CSF, lenograstim). Peripheral blood progenitor cells (PBPC) were harvested by leukaphereses during early recovery from chemotherapy-induced aplasia. A total of 119 leukaphereses were performed. Median numbers of CD34⁺ cells and CFU-GM collected were 2.04 × 10⁶/kg and 2.9 × 10⁴/kg, respectively. There was a significant correlation between white cell count and number of CD34⁺ cells in the leukaphereses (P = 0.0001, r² = 0.41, n = 104). A strict correlation between the number of CD34⁺ cells and CFU-GM in the leukapheretic product (P = 0.0001, r² = 0.39, n = 110) was observed. 21% of evaluable patients (6/29) achieved a complete cytogenetic remission in the leukapheretic product and the other four patients achieved a major cytogenetic response for an overall response of 35% (10/22 patients). To date, 16 patients have been autografted and are alive. Five of them are Ph¹-negative (three patients) or partially Ph¹-negative (two patients). In conclusion, despite the high-risk characteristics of this study population, Ph¹-negative PBPC were successfully mobilized in more than one-quarter of patients using a chemotherapy plus rhuG-CSF regimen. The importance of this achievement is increased by the current lack of other practical methods of rescuing Ph¹-negative cells in such patients.     

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.     

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.