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S Tura

Publications and source records attributed to S Tura.

At least 37 records · Page 2Linked to original sources
PubMed2001

Pulsed ATRA as single therapy restores long-term remission in PML-RARalpha-positive acute promyelocytic leukemia patients: real time quantification of minimal residual disease. A pilot study.

All-trans retinoic acid (ATRA), alone or combined with chemotherapy (CHT) is widely used to induce complete remission (CR) in newly diagnosed acute promyelocytic leukemia (APL). If used alone, ATRA results in a substantial proportion of CRs. To maintain remission further, ATRA is commonly used with cycles of CHT, frequently followed by autologous (auto) or allogeneic (allo) stem cell transplantation (SCT), as early reports have shown that the continuous administration of ATRA as single therapy almost invariably leads to relapse in a short period of time (months). Pharmacokinetic studies have shown that induced resistance to ATRA is frequently suppressed by the intermittent use of the drug. In this study we applied an intermittent therapeutic protocol with ATRA in five APL patients who were either molecularly refractory after combined ATRA/CHT treatment, or relapsed, or at diagnosis, but not eligible for the combination treatment because of previous toxicity. They were treated with ATRA (45 mg/m2/day) for 21 days. The treatment was then prolonged continuously for 1 week every 2 weeks. Molecular analysis was performed by qualitative and quantitative reverse transcription-polymerase chain reaction (RT-PCR). All patients obtained molecular remission, as assessed by qualitative RT-PCR, in a median of 3 months (range 1-15). Quantitative RT-PCR confirmed these data, showing a progressive reduction (1 or 2 logs) to a 'negligible quantity' of PML-RARalpha fusion transcript (ratio PML-RARalpha/ABL x 10(4) ABL < 10(-1)) in all but one patient treated with pulsed ATRA therapy. These data were confirmed with qualitative and quantitative RT-PCR. After a median follow-up of 17 months from the start of ATRA therapy, 4/5 patients (80%) are in continuous complete molecular remission. To our knowledge, this is the first clinical observation that intermittent ATRA therapy (without chemotherapy) is effective not only in inducing but also in maintaining long-term molecular remission in APL patients. This approach could therefore be effective, if confirmed in larger series, in relapsed/refractory patients unsuitable for high-dose therapy and SCT; it may be proposed as induction therapy for selected older APL patients if considered not to be eligible for combined ATRA/CHT due to inadequate performance status or concurrent disease.

Adult↗
PubMed2001

Progress in allogenic bone marrow and peripheral blood stem cell transplantation for multiple myeloma: a comparison between transplants performed 1983--93 and 1994--8 at European Group for Blood and Marrow Transplantation centres.

Out of 690 allogeneic matched sibling donor transplants for multiple myeloma reported to the European Group for Blood and Marrow Transplantation (EBMT) registry, 334 were performed during the period 1983-93 (all with bone marrow) and 356 during 1994-98 [223 with bone marrow and 133 with peripheral blood stem cells (PBSCs)]. The median overall survival was 10 months for patients transplanted during the earlier time period and 50 months for patients transplanted with hone marrow during the later period. The use of PBSCs was associated with earlier engraftment but no significant survival benefit compared to bone marrow transplants during the same time period. The improvement in survival since 1994 with the result of a significant reduction in transplant-related mortality, which was 38%, 21% and 25% at 6 months and 46%, 30% and 37% at 2 years during the earlier period, and the later period with bone marrow and PBSCs respectively. Reasons for the reduced transplant-related mortality appeared to be fewer deaths owing to bacterial and fungal infections and interstitial pneumonitis, in turn a result of earlier transplantation and less prior chemotherapy. Better supportive treatment and more frequent use of cytokines may also play a role. The improvement in survival was not directly related to the increased use of PBSCs.

Adult↗
PubMed2001

Antiangiogenic therapy in multiple myeloma.

In the recent years, several pieces of evidence have pointed out that disease progression in multiple myeloma (MM) is characterized by an increased bone marrow neovascularization. Targeting the mechanisms that control angiogenesis could thus represent an innovative therapeutic approach to MM. Thalidomide, a glutamic acid derivative with sedative properties, is able to inhibit angiogenesis in murine models; this compound has recently demonstrated to be effective in relapsed/refractory MM, leading to a 30-40% response, coupled with mild systemic toxicity. Inhibition of angiogenesis is probably just one of the mechanisms by which thalidomide exerts its action in MM, as immunomodulation and inhibition of cytokine production by bone marrow stroma could also be involved. At present, several studies are ongoing, aiming at testing thalidomide-based drug combinations, mainly with dexamethasone, but also with conventional chemotherapy; the results that have been obtained so far show a synergistic effect of the drug combinations, with a response rate ranging from 50 to 70% in pretreated patients. There is now growing interest in novel compounds with potential antiangiogenic effects, among them a promising activity both in vitro and in animal models has been displayed by thalidomide analogs, inhibitors of vascular endothelial growth factor receptor-2 and endostatin.

Angiogenesis Inhibitors↗
PubMed2001

Interleukin-4 downregulates nuclear factor-erythroid 2 (NF-E2) expression in primary megakaryocytes and in megakaryoblastic cell lines.

The transcriptional factor nuclear factor-erythroid 2 (NF-E2) is one of the few transcription factors known to be functionally linked to the megakaryocytic lineage, where it regulates terminal megakaryocyte maturation and platelet formation. However, the regulation of NF-E2 expression in megakaryocytic cells has not been extensively evaluated. In particular, no data have been reported on the effect of negative regulators of megakaryocytopoiesis on NF-E2 expression. This study investigated the in vitro effects of two negative regulators of megakaryocytopoiesis, such as interleukin-4 (IL-4) and transforming growth factor-beta1 (TGF-beta1) on the expression of NF-E2 transcription factor in megakaryoblastic cell lines (Hel and MK1) and in normal CD34-derived megakaryocytic cells. For this purpose, we used quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) to detect mRNA NF-E2 isoforms (a and f) and flow-cytometry analysis to evaluate NF-E2 protein expression. Our results demonstrated that TGF-beta1 did not inhibit NF-E2 mRNA and protein expression of either maturating or fully mature normal megakaryocytic cells as well as that of the two cell lines. By contrast, IL-4 downmodulates the expression of NF-E2 transcription factor at both mRNA and protein levels in normal maturating megakaryocytic cells and in the megakaryoblastic cell lines. NF-E2 expression of normal mature megakaryocytes was not affected by IL-4. Thus, the results of the present investigation demonstrate that NF-E2 transcription factor is involved not only in terminal megakaryocyte maturation but also in the negative regulation of the early phase of megakaryocyte development.

Cell Division↗
PubMed2001

Competitive polymerase chain reaction as a method to detect the amplification of bcr-abl gene of chronic myeloid leukemia.

BACKGROUND AND OBJECTIVES: The chimeric product of the bcr-abl rearranged gene is critical in the pathogenesis of chronic myeloid leukemia (CML), yet its role in the progression of the disease remains unclear. There is some evidence that increased bcr-abl expression levels, possibly due to gene amplification, precede the clonal evolution of CML hematopoietic progenitors toward a fully transformed phenotype and might be involved in their resistance to interferon-alpha or tyrosine kinase inhibitors. DESIGN AND METHODS: To quantify the bcr-abl gene both at the genomic and at the transcriptional levels we developed a competitive polymerase chain reaction (PCR) strategy. The competitive PCR technique is based upon the co-amplification of the sample template (target) together with increasing amounts of a DNA fragment (competitor) sharing with the target the primer recognition sites, but differing in size. We constructed a competitor for the quantification of both b2a2 and b3a2 alternative splicing forms of the bcr-abl chimera and established the accuracy and reproducibility of our competitive strategy in a clone of the murine 32DG hematopoietic cell line (32D LG7), which bears a stable integration of a single copy of p210 bcr-abl fusion gene. We utilized this technique to follow, over a period of 200 days, the fusion gene copy numbers and transcription rates in several p210 bcr-abl-transduced 32D cell clones, an experimental condition mimicking the evolution of CML myeloid progenitors in vivo. RESULTS: Our results are consistent with p210 bcr-abl overexpression but not gene amplification associated with their clonal evolution. Increased p210 bcr-abl transcription rate is associated with the abrogation of radiation-induced apoptotic cell death, suggesting a role for the chimeric gene expression level in cell life expectancy after a genotoxic insult. INTERPRETATION AND CONCLUSIONS: We conclude that the assessment of gene amplification and expression might serve to improve prognostic classification and follow-up of CML patients.

Alternative Splicing↗
PubMed2001

Primary mediastinal large B-cell lymphoma with sclerosis: a clinical study of 89 patients treated with MACOP-B chemotherapy and radiation therapy.

BACKGROUND AND OBJECTIVES: Primary mediastinal large B-cell lymphoma (PMLBCL) with sclerosis has recently been recognized as a specific clinical and pathologic entity for which the best therapeutic approach seems to be a combination of chemotherapy and radiotherapy. DESIGN AND METHODS: Between 1989 and 1998, 89 previously untreated patients with PMLBCL with sclerosis were treated with a combination of a third-generation chemotherapy regimen (MACOP-B) and mediastinal radiation therapy. The response evaluations were examined after chemotherapy and at the end of radiotherapy. RESULTS: Twenty-three (26%) patients achieved a complete response (CR) and 59 (66%) obtained a partial response (PR) after the MACOP-B regimen. After radiation therapy, 55/59 (93%) of the patients in PR achieved CR. The CR rate at the end of the treatment was 88% (78/89). Only 7 (8%) patients were non-responders. Among the 78 patients who obtained a CR there were 7 (9%) relapses in a median follow-up of 5 months (all relapses occurred within 9 months); the other 71 patients are currently in continuous CR with a median follow-upof 45 months (range, 4-110 months). Projected overall survival was 86% at 9 years; the relapse-free survival curve of the 78 patients who achieved CR was 91% at 9 years. INTERPRETATION AND CONCLUSIONS: In patients with PMLBCL with sclerosis, combined modality treatment using the MACOP-B chemotherapy regimen and radiation therapy induces a good remission rate with the patients having a greater than 90% chance of surviving disease-free at 9 years. Radiotherapy often plays a pivotal role in obtaining CR status.

Adolescent↗
PubMed2001

Real-time quantification of different types of bcr-abl transcript in chronic myeloid leukemia.

BACKGROUND AND OBJECTIVES: The most common translocation in chronic myeloid leukemia (CML) t(9;22) (q34;q22) produces the BCR/ABL fusion gene. We set up and evaluated a rapid and reliable real-time reverse-transcription-polymerase chain reaction (RT-PCR) approach using TaqMan technology for detection and quantification of bcr-abl transcripts in CML patients at diagnosis and during therapy. DESIGN AND METHODS: A pair of primers and probe complementary to ABL exon 2 were designed, enabling detection of the most frequent bcr-abl transcripts, and also of the normal ABL-Ia transcript as an internal control. Conditions were established to amplify less than 1(-10) target molecules/reaction and detect one CML cell in 10(6) cells from healthy donors. To determine the utility of the assay, we quantified the bcr-abl/ABL-Ia ratio in 59 bone marrow samples (45 samples with evidence of different Ph+ chromosome percentages and 14 samples in complete cytogenetic remission) from 48 CML patients, 34 of them at diagnosis and 14 in clinical remission (CR). In 14 cases, this ratio was compared with results obtained by a competitive-quantitative RT-PCR/capillary electrophoresis method from contemporary specimens. RESULTS: By real-time RT-PCR, the median value of bcr-abl/ABL-Ia ratio at diagnosis was 15.334 (range 3.3-28.81) and fell to 0.9 (range 0.003-26.1) in CR. The median value of bcr-abl/ABL-Ia ratio at cytogenetic remission was 0.7 (range 0.003-2.83). The real-time bcr-abl/ABL-Ia ratios correlated with those obtained by competitive RT-PCR (p < 0.0001) and the percentage of Ph+ metaphases (p < 0.0001). The high sensitivity and specificity of the real-time RT-PCR procedure was confirmed in all 14 patients with minimal residual disease. INTERPRETATION AND CONCLUSIONS. We conclude that this real-time RT-PCR procedure is a reliable and sensitive method of monitoring CML patients after therapy, and that the bcr-abl/ABL-Ia ratio correlates strongly with cytogenetic analysis.

Bone Marrow↗
PubMed2001

Efficacy of vinorelbine, epirubicin and prednisone combination regimen in pretreated elderly patients with aggressive non-Hodgkin's lymphoma.

BACKGROUND AND OBJECTIVES: To assess the efficacy and toxic profile of the NAEPP protocol, a regimen including vinorelbine, epirubicin and prednisone, in a particularly troublesome subset of patients: pretreated elderly patients with aggressive non-Hodgkin's lymphoma (NHL). DESIGN AND METHODS: From November 1998 to January 2000, 20 pretreated patients who had all relapsed after first-line VNCOP-B chemotherapy were enrolled in a phase II trial and treated with the NAEPP regimen: vinorelbine (25 mg/m(2) i.v. on days 1 and 8), epirubicin (40 mg/m(2) i.v. on days 1 and 8), and prednisone (40 mg/m(2) on days 1 and 8) with granulocyte colony-stimulating factor administered at 5 mg/kg/day on days 2-5 and days 9-12. Chemotherapy was repeated every 4 weeks for a total of 6 cycles. RESULTS: Six (30%) patients achieved complete remission (CR) and 7 (35%) had partial responses (PR), giving an overall response rate of 65%. The response rate was not affected either by type of relapse presentation (nodal versus nodal plus extranodal), presence of bulky disease, or time of relapse. No major toxic effects were recorded. INTERPRETATION AND CONCLUSIONS: These preliminary data suggest that the NAEPP regimen is an effective combination with a low toxicity profile in elderly pretreated patients with aggressive NHL. Further trials using NAEPP as a consolidation phase following first-line treatment are needed to establish the advantage in terms of CR rate and relapse-free survival in these patients.

Aged↗
PubMed2001

Salvage therapy with thalidomide in multiple myeloma patients relapsing after autologous peripheral blood stem cell transplantation.

BACKGROUND AND OBJECTIVES: The introduction of high-dose therapy with stem cell support has significantly improved the outcome of patients with multiple myeloma (MM) in terms of increased complete remission (CR) rate and extended survival, both disease-free and overall. Few options, however, are presently available for patients who relapse after single or double autologous stem cell transplantation (SCT). Thalidomide, a glutamic acid derivative with anti-angiogenetic properties, has been recently proposed as salvage treatment for such patients. The present study was aimed at evaluating thalidomide as single agent therapy for patients who had previously received autologous peripheral blood stem cell transplantation. DESIGN AND METHODS: From October 1999 to August 2000, 11 patients (7 males/4 females) who had relapsed after single (n = 4) or double (n = 7) autologous peripheral blood SCT were enrolled in the trial. Thalidomide, always employed as a single agent, was initially administered at a dose of 100 mg/day; if well tolerated, the dose was increased serially by 200 mg every other week to a maximum of 800 mg/day. RESULTS: The median administered dose was 600 mg/day. WHO grade > II toxic effects were constipation, lethargy, and leukopenia. Four patients (36%) showed > 50% reduction in serum M protein concentration and 4 showed > 25% reduction, for a total response rate averaging 72%. After a median follow-up of 5 months, 3 out of 8 responding patients are alive and progression-free and 5 patients have relapsed. INTERPRETATION AND CONCLUSIONS; These data confirm that thalidomide is active in poor-prognosis MM patients such as those relapsing after autologous SCT, and could thus deserve further testing in combination therapy.

Adult↗
PubMed2001

Delayed non-infectious lung disease in allogeneic bone marrow transplant recipients.

BACKGROUND AND AIM OF THE WORK: The studies on late-onset non-infectious respiratory complications after allogeneic bone marrow transplantation (allo-BMT) have been mainly focused on bronchiolitis obliterans to date. The aim of this work was to analyze the incidence, clinico-pathologic characteristics and outcome of the entire spectrum of entities falling into the group of delayed non-infectious lung disease (DLD). METHODS: Retrospective chart review was carried out of 112 patients who underwent allo-BMT for hematologic malignancies between April 1995 and November 1998 at a single Institution. The categorization of the pulmonary disease was made by analyzing clinical data, bronchoalveolar lavage (BAL), high-resolution computed tomography (HRCT) and histology when possible. RESULTS: DLD occurred in 10 (10%) out of 97 recipients who survived at least 100 days following allo-BMT and was defined as bronchiolitis obliterans (BO; 4 cases), acute lung injury (ALI; 1 case) and subacute cellular interstitial pneumonia (SCIP; 5 cases). The BAL-profile was characterized by a marked increase of the neutrophil percentage in BO cases and of the lymphocyte (predominantly CD8+) percentage in parenchymal DLDs (SCIP, ALI). HRCT proved to be helpful to correctly identify BO cases, whereas histology was always needed to better define DLD presenting with an interstitial and/or alveolar pattern. The predominant airway involvement as well as the acute-onset of a respiratory illness with histological evidence of diffuse alveolar damage were associated with a worse prognosis because of a poor response to the immunosuppressive treatment. CONCLUSIONS: DLDs represent a group of entities heterogeneous in regard to variables such as onset and clinical behaviour (acute, subacute or chronic), predominant pattern of lung involvement (airway or parenchymal), response to treatment. Although immunopathologic mechanisms related to c-GVHD probably have a relevant pathogenic importance in this setting, the possible role of associated events (eg, drug toxicity and infections) at least in priming the lung damage need to be better clarified for its therapeutical implications.

Adolescent↗
PubMed2001

Long-term follow-up of idiopathic thrombocytopenic purpura in 310 patients.

BACKGROUND AND OBJECTIVES: Idiopathic thrombocytopenic purpura (ITP) induces thrombocytopenia by means of an autoimmune mechanism. Despite the available therapies a subset of patients develop chronic refractory severe thrombocytopenia (i.e. a platelet count consistently lower than 20 to 30x10(9)/L), and life-threatening bleeding can occasionally occur. It has been suggested that the risk of major bleeding is higher in elderly patients and in patients with bleeding at diagnosis. However, since clear data on the influence of clinical and/or laboratory parameters on outcome are lacking, some patients may be receiving unnecessary treatment. DESIGN AND METHODS: We made a retrospective analysis of a series of 310 patients with chronic ITP (108 males and 202 females), with a median age at diagnosis of 40 years (range 8-87 years). The median follow-up time was 121 months, (range 7-434 months). Therapy was most often started in the presence of hemorrhagic complications and/or a platelet count <30x10(9)/L either at diagnosis or during follow-up. RESULTS: Our findings confirmed that patients who were symptomatic at diagnosis were more likely to have bleeding during their follow-up. Moreover, all the patients who suffered major bleeding during their follow-up had median platelet counts of 10x10(9)/L (range 1-20) at that time. Only one patient, aged 43 years, died of hemorrhage following prolonged severe thrombocytopenia. Age >60 years was not associated with any significant differences in incidence of bleeding at diagnosis or during follow-up. INTERPRETATION AND CONCLUSIONS: We conclude that prospective studies are required to evaluate whether it may be reasonable to treat only symptomatic patients, independently of age.

Adolescent↗
PubMed2001

Molecular therapy for multiple myeloma.

BACKGROUND AND OBJECTIVES: Several molecular and cytogenetic advances have suggested novel therapeutic strategies that could help reach an eventual cure for multiple myeloma (MM). EVIDENCE AND INFORMATION SOURCES: Identification of novel, "MM-specific" molecular targets should pave the way for drugs that can specifically attack the neoplastic cells while sparing the normal ones. Drugs that alter the marrow microenvironment--such as bisphosphonates, proteasome inhibitors (e.g. PS-341/LDP341), lactacystin or LLNV compounds--induce apoptosis or G1 growth arrest and alter the adhesion of MM cells to marrow stroma. These drugs that modified microenvironment have a more solid scientific basis and may therefore have more realistic implications in MM treatment. Of these, novel vascular endothelial growth factor (VEGF) inhibitors, such as SU5416 and SU6668, block tumor-cell adhesion and could disrupt MM cell proliferation. Similar tyrosine kinase inhibitors (TKI) such as fibroblast growth factor receptor (FGFR) inhibitors may serve when the FGFR3 gene is overexpressed due to the t(4;14)(p16.3;q32) and/or is activated by point mutations. In cases carrying the translocation and expressing the IgH/WHSC1-MMSET hybrid transcripts, histone deacetylase (HDAC) inhibitors could be useful, but their possible clinical use need to be supported by more biological studies. Tumor necrosis factor alpha-related apoptosis-inducing ligand (TRAIL) induces apoptosis in MM cell lines and primary cells. The proliferative signaling pathway of FGFR3 is mediated by Ras (Ras-activating mutations are frequently found in MM), which presents a possible target for farnesyltransferase inhibitors (used alone or in association with IFN-alpha). PERSPECTIVES: In several of these options, preclinical studies have proved encouraging, and clinical trials are now getting underway.

Animals↗
PubMed2000

Molecular monitoring of minimal residual disease in patients in long-term complete remission after allogeneic stem cell transplantation for multiple myeloma.

In the present study, we used a polymerase chain reaction-based (PCR-based) strategy to retrospectively analyze the presence of residual myeloma cells in serial posttransplant bone marrow samples obtained from 13 patients in remission after allogeneic hemopoietic stem cell transplantation (allo SCT). For this purpose, patient-specific primers were generated from complementarity determining regions 2 and 3 of the rearranged IgH gene. The level of sensitivity of the PCR-based assay ranged from 1 in 10(5) to 1 in 10(6) normal marrow cells. Following transplantation, 9 of 12 patients who attained stringently defined complete remission (CR) remained persistently PCR(-) for a median of 36 months, and 4 of the patients remained PCR(-) up to the latest analysis, which was performed at 48, 72, 72, and 120 months, respectively, after allo SCT. None of the patients in the PCR(-) subgroup experienced a disease relapse, and only 1 of 4 PCR(+) patients experienced a relapse. It is concluded that allo SCT has the potential ability to induce sustained serological and molecular CR in selected patients with multiple myeloma.

Adult↗
PubMed2000

Engraftment, clinical, and molecular follow-up of patients with multiple myeloma who were reinfused with highly purified CD34+ cells to support single or tandem high-dose chemotherapy.

Eighty-two patients with advanced multiple myeloma (MM) were enrolled in 2 sequential clinical studies of 1 or 2 courses of myeloablative therapy with stem cell support. Conditioning regimens consisted of high-dose melphalan (MEL) with or without total body irradiation (TX1 = 35) and MEL as the first preparative regimen, followed within 6 months by busulfan and melphalan (TX2 = 47). On the basis of adequate stem cell harvest, 31 patients (TX1 = 13; TX2 = 18) were transplanted with highly purified CD34+ cells. Positively selected stem cells did not adversely affect hematopoietic reconstitution compared with unmanipulated peripheral blood stem cell. Overall, the complete remission (CR) rate of evaluative patients was 13.8% and 41% for single and double autotransplant, respectively (P =.04). Moreover, 3 patients undergoing TX2 achieved molecular remission and 2 remain PCR-negative after 36 and 24 months from autograft. The median event-free survival (EFS) durations for TX1 and TX2 were 17 and 35 months, respectively (P =.03). Actuarial 3-year overall survival for patients treated with 1 or 2 transplants are 76% and 92%, respectively (P = NS). On multivariate analysis, superior EFS was associated with low beta2 microglobulin (beta2-M) level at diagnosis and TX2, whereas overall survival was correlated with beta2-M. Positive selection of CD34+ cells did not influence the achievement of clinical or molecular CR, as well as remission duration or survival of MM patients. Thus, whereas multiple cycles of high-dose therapy may be beneficial for patients with myeloma, the clinical impact of tumor cell purging remains highly questionable.

Adolescent↗
PubMed2000

Transforming growth factor beta3 inhibits chronic myelogenous leukemia hematopoiesis by inducing Fas-independent apoptosis.

OBJECTIVE: Transforming growth factor beta3 (TGF-beta3) is a potent suppressor of human hematopoietic progenitor cells. In this article, we compare the activity of TGF-beta3 on highly purified CD34+ cells and more immature CD34-DR(-) cells from chronic myelogenous leukemia (CML) patients in chronic phase and normal donors. MATERIALS AND METHODS: Primitive hematopoietic progenitors were stimulated in liquid cultures and clonogenic assays by early-acting growth factors such as stem cell factor (SCF) and interleukin 11 (IL-11) and the intermediate-late-acting stimulating factors IL-3, granulocyte-macrophage colony-stimulating factor, and erythropoietin. Molecular analysis of bcr/abl mRNA was performed on single CML colonies by nested reverse transcriptase polymerase chain reaction. Moreover, cell cycle analysis and assessment of apoptosis of normal and leukemic CD34+ cells were performed by propidium iodide (PI) alone and simultaneous staining with annexin V and PI, respectively. RESULTS: The colony-forming efficiency of CML CD34+ cells was generally inhibited by more than 90% regardless of whether the colony-stimulating factors were used alone or combined. When compared to normal CD34+ cells, leukemic cells were significantly more suppressed in 6 of 8 culture conditions. The inhibitory effect of TGF-beta3 on CD34+ cells was exerted within the first 24 hours of incubation as demonstrated by short-term preincubation followed by IL-3-and SCF-stimulated colony assays. Evaluation of bcr/abl transcript on residual CML colonies incubated with TGF-beta3 demonstrated a small subset of neoplastic CD34+ cells unresponsive to the inhibitory effect of the study cytokine. TGF-beta3 demonstrated a greater inhibitory activity on primitive CD34+DR cells than on more mature CD34+ cells. Again, CML CD34+DR(-) cells were significantly more inhibited by TGF-beta3 than their normal counterparts in 3 of 8 culture conditions. Kinetic analysis performed on CD34+ cells showed that TGF-beta induces cell cycle arrest in G(1) phase. However, this mechanism of action is shared by normal and leukemic cells. Conversely, TGF-beta3 preferentially triggered the programmed cell death of CML CD34-cells without increasing the proportion of leukemic cells coexpressing CD95 (Fas receptor), and this effect was not reversed by functional blockade of Fas receptor. Conclusion. We demonstrate that TGF-beta3 exerts a potent suppressive effect on CML cells that is partly mediated by Fas-independent apoptosis.

Antigens, CD34↗