Fludarabine/i.v. BU conditioning regimen: myeloablative, reduced intensity or both?

In this study, we utilized a conditioning regimen with fludarabine and myeloablative dose i.v. BU (12.8 mg/kg) (FluBU) in 36 adult patients (median age: 44 years, range: 18-61) with myeloid or lymphoid malignancies at standard risk (n=10) or high risk of relapse (n=26), who received an allogeneic hematopoietic SCT (HSCT) from HLA-matched related (n=16) or unrelated (n=20) donors. The source of hematopoietic stem cells was peripheral blood in 28 and marrow in 8 cases. Rabbit-antithymocyte globulin at 7 mg/kg was utilized in 21 patients. Acute GVHD grade II-IV was observed in 19% of the patients (grade III-IV in 14% of patients) and chronic GVHD in 11 of 30 evaluable patients (37%). At median follow-up of 737 days (range: 152-1,737) for alive patients, overall survival rates in standard- and high-risk patients were 80 and 35%, respectively, and event-free survival rates were 70 and 31%, respectively. TRM was 10% in standard-risk and 19% in high-risk patients. Post transplant relapse was observed in 20% standard-risk and in 46% high-risk patients. FluBU conditioning regimen is associated with a limited hematologic and extrahematologic toxicity and with an antitumor activity comparable to other standard myeloablative regimens.

Comparable kinetics of myeloablation between fludarabine/full-dose busulfan and fludarabine/melphalan conditioning regimens in allogeneic peripheral blood stem cell transplantation.

Fludarabine was utilized in the conditioning regimen of 30 adult patients undergoing an allogeneic hematopoietic stem cell transplant. In 18 patients it was combined with full-dose busulfan (FluBu) as a myeloablative regimen and in 12 cases with melphalan (FluMel) as a reduced intensity conditioning (RIC) regimen. Patients in the FluBu group were younger than in the FluMel group (P=0.03). Of 30 patients, 24 received peripheral blood stem cells (PBSC) whereas six patients in the FluBu group received bone marrow cells. The hematological toxicity of each regimen was evaluated by analyzing the kinetics of the neutropenia induced by preparative regimens and the time to recovery of the absolute neutrophils count (ANC) and platelets post transplantation. In PBSC transplants, the median day of severe neutropenia (<500 ANC/microl) occurred on day +6 after the FluBu regimen and on day +3 after FluMel (P=ns), whereas both groups had a duration of severe neutropenia of 9 days and a comparable time for ANC and platelet engraftment. Extra-hematological toxicities were also comparable in the two groups. These findings suggest that the hematological and extra-hematological toxicities induced by fludarabine/full-dose i.v. busulfan are similar to those induced by a standard RIC regimen such as fludarabine/melphalan.

Prolonged responses after autologous stem cell transplantation in African-American patients with multiple myeloma.

Multiple myeloma (MM) has a double incidence in African-American (AA) than in non-AA patients and previous studies have shown a higher mortality in the former patient population. Here, we retrospectively analyzed the results of autologous stem cell transplantation (ASCT) in 38 AA and 32 non-AA consecutive patients. The two groups were comparable at diagnosis for age, stage of the disease, cytogenetic abnormalities, beta(2) microglobulin and albumin blood levels, and plasma cell marrow infiltration. The rates of complete and partial response observed in AA and non-AA patients after induction chemotherapy (9 and 42 vs 13 and 33%) and at 2 months (31 and 25 vs 30 and 20%) following ASCT were similar. At 6 months after ASCT, a greater relapse rate was observed in non-AA patients (P=0.009). At a median follow-up of 26 months, AA patients had a greater event-free survival (P=0.02) than non-AA patients, whereas overall survival was comparable in the two groups. The initial finding that AA patients with MM, compared to non-AA patients, had more prolonged responses and comparable survival after ASCT suggests that intensified chemotherapy is equally effective in patients of various ethnicities.

Melphalan 200 mg/m2 in patients with renal impairment is associated with increased short-term toxicity but improved response and longer treatment-free survival.

Data on the effectiveness and toxicity of high-dose melphalan in patients with renal impairment (RI) are lacking. We evaluated the impact of RI on outcomes of patients with multiple myeloma treated with melphalan 200 mg/m2 (Mel200) and autologous stem cell transplantation. Similar baseline characteristics were seen among 46 patients with creatinine clearance (CrCl) <60 mL/min (median 50 mL/min, range 20-59) and 103 patients with CrCl ⩾60 mL/min (median 83 mL/min, range 60-128). Patients with CrCl <60 mL/min had longer time to neutrophil (P=0.008) and platelet engraftment (P<0.001). Diarrhea, duration of total parenteral nutrition use and infection were significantly higher in the CrCl <60 mL/min group. With a median follow-up of 35 months (range 2-132) in the CrCl <60 mL/min group and 47 months (range 1-45) in the CrCl ⩾60 mL/min group, overall survival was comparable between the two groups. Median treatment-free survival was longer in the RI group (37 vs 17 months, P=0.0025). Multivariate analysis showed CrCl <60 mL/min (hazard ratio (HR) 3.5), and prior proteasome inhibitor therapy (HR 2.441) both predicted longer treatment-free survival. We consider Mel200 safe and effective in patients with CrCl between 30 and 60 mL/min.

Constitutive and stimulated production of VEGF by human megakaryoblastic cell lines: effect on proliferation and signaling pathway.

Release of vascular endothelial growth factor (VEGF) and other candidate angiogenic factors such as basic fibroblast growth factor and transforming growth factor beta, may play a role in sustaining neoplastic cell proliferation and tumor growth. We evaluated VEGF expression and synthesis in the two erythromegakaryocytic cell lines B1647, HEL and one megakaryocytic cell line MO7 expressing erythroid markers. In this study RT-PCR was performed to evaluate VEGF expression and that of its receptor KDR; VEGF production was assayed by Elisa test and western blot analysis; sensitivity to VEGF was tested by thymidine incorporation. VEGF and its receptor KDR were expressed in B1647 and HEL, both as mRNAs and as proteins, while only KDR transcript was found in MO7 cells. Only B1647 and HEL cells showed a strong spontaneous proliferating activity. In fact, measurable amounts of VEGF were present in the unstimulated cell medium, thus suggesting an autocrine production of VEGF by B1647 and HEL cells, but not by MO7, which was inhibited in mRNA-silencing conditions. This production could not be further boosted by other growth factors, whereas it was inhibited by TGF-beta1. Finally, analysis of Shc signal transduction proteins following stimulation with VEGF indicated that only p46 was tyrosine phosphorylated. These data indicate that leukemic cells may be capable of autocrine production of VEGF which, in turn, maintains cell proliferation, possibly mediated by Shc p46 phosphorylation.

In vitro susceptibility of acute leukemia cells to the cytotoxic activity of allogeneic and autologous lymphokine activated killer (LAK) effectors: correlation with the rate and duration of complete remission and with survival.

Acute lymphoblastic leukemia (ALL) and acute myeloblastic leukemia (AML) blasts were studied for their sensitivity to the lytic activity of normal allogeneic interleukin 2 (IL-2) activated killer (LAK) cells, and of autologous LAK effectors generated at the time of complete remission (CR). In 12 of 23 ALL cases (52%), the blasts were susceptible to normal LAK cells (> 15% lysis) and ten of them achieved a CR. Of the remaining 11 LAK-resistant cases, seven obtained a CR. No correlation was found between susceptibility to LAK activity, cytomorphology, immunophenotype, CR duration and survival. Eighteen of the 26 AMLs tested (70%) were susceptible to normal LAK cells, and nine of the 13 cases studied (70%) were also lysed by autologous LAK effectors generated at CR. No clearcut correlation was observed between blast sensitivity to normal LAK cells and morphologic cytotype, though a higher incidence of resistant cases was observed in the M4 subgroup. All AMLs susceptible to normal LAK cells but one achieved a CR, while this occurred only in three of the eight resistant cases (p = 0.004). The median survival and event-free survival duration in the resistant patients were significantly shorter (p = 0.03 and p = 0.02, respectively) compared to those of the susceptible patients. In ten ALL and in six AML, which at presentation displayed less than 10% circulating blasts, the susceptibility of the leukemic population to normal and autologous LAK effectors could be tested, both at diagnosis and at remission. All cases but one were resistant to autologous LAK cells generated at diagnosis, while at CR, seven cases (four ALL and three AML) became susceptible to autologous LAK cells (p = 0.01). The remaining nine were resistant to both allogeneic and autologous LAK effectors. Taken together, these findings suggest that in AML, but not in ALL, the LAK cell compartment may play a role in the clinical course and overall outcome of the disease.

Biological markers and minimal residual disease in hairy cell leukemia.

Soluble Interleukin-2 Receptor (sIl-2R) and Tumor Necrosis Factor-alpha (TNF-alpha) have been found significantly increased in serum samples of patients with HCL at diagnosis and a strict correlation with leukemic burden has been reported. Furthermore, following therapy, serological monitoring of these cytokines may be considered a useful tool for controlling therapeutic efficacy and for detection of minimal residual disease. Eighteen HCL patients, treated with 2-Chlorodeoxyadenosine (2-CdA) at a dose of 0.1 mg/kg daily for 7 days, entered the study all of them showing increased levels of sIL-2R and TNF-alpha prior to therapy. After therapy, serum levels were reassessed and a remarkable decrease was recorded in all cases. In particular, after 1 month by the end of treatment sIL-2R and TNF-alpha decreased from 3,377 +/- 2,303 to 149 +/- 96 pM/ml (p = 0.00003) and from 38 +/- 41 to 18 +/- 18 pg/ml (p = 0.015) respectively. The only 3 patients who did not normalize sIL-2R and TNF-alpha levels showed also an evident persistence of the disease in the marrow. In conclusion, 2-CdA leads to a rapid normalization of the increased levels of sIL-2R and TNF-alpha in the majority of HCL patients. Furthermore, monitoring of these cytokines represents a useful tool for detecting minimal residual disease.

Long-lasting complete remission in patients with hairy cell leukemia treated with 2-CdA: a 5-year survey.

Between January 1991 and January 1994, 40 patients with hairy-cell leukemia (HCL), 30 males and 10 females, with a median age of 54 years, were treated with a single course of 2-chlorodeoxyadenosine (2-CdA) at a dose of 0.1 mg/kg/day continuous infusion for 7 days. Thirteen patients were untreated and 27 had previously received alpha-interferon. Thirty out of 40 patients (75%) achieved complete remission (CR) and 10 (25%) partial remission (PR). The median follow-up duration for patients in CR has been 48 months (range 30-66). Five of the complete responders (17%) relapsed at 12, 24, 26, 30 and 36 months after treatment as documented by the increase of hairy cells (Hc) in the bone marrow and two of them, who were retreated with 2-CdA after showing an initial impairment of peripheral blood values, obtained a second CR. The remaining three relapsed patients were never retreated and still show normal peripheral counts after 30, 38 and 40 months. Twelve of the continuous complete responder patients are still in CR after more than 5 years. In contrast, 8 out of 10 partial responders progressed after 8-36 months and all of them were retreated with 2-CdA at a dose of 0.15 mg/kg/day for 5 days i.v. Four of them (50%) achieved a CR, three a better PR and one patient died 6 months after the second 2-CdA course because of infectious complications. Two additional patients, both in CR, died after 28 and 37 months because of a second neoplasm. Toxic side-effects consisted of febrile episodes recorded in 16 patients: in seven of them, fever lasted only 24-48 h after the end of treatment and was apparently not infection-related. In the remaining nine patients, showing in addition severe neutropenia (neutrophils less than 1.0 x 10(9)/l), fever was related to bacterial infection requiring systemic antibiotics in all of them and G-CSF in three cases. In conclusion, 2-CdA induces a very high proportion of complete and long-lasting remissions in patients with HCL. In a number of cases relapse at bone marrow level may not affect peripheral blood values for prolonged time. However, in those patients with initial pancytopenia a retreatment with 2-CdA is still effective in inducing a durable second CR.

High bcl-2 expression in acute myeloid leukemia cells correlates with CD34 positivity and complete remission rate.

Flow cytometric expression of bcl-2 protein was analyzed in 90 newly diagnosed acute myeloblastic leukemia (AML) patients using an anti-bcl-2 monoclonal antibody by direct immunofluorescence technique and results were correlated with FAB cytotype, CD34 expression and clinical outcome. Bcl-2 was expressed in all AML cases with different intensity. The mean fluorescence index (MFI), expressed as the ratio of sample mean channel:control mean channel, ranged from 3.0 to 39.5 with a median value of 14. The MFI was significantly higher (P = 0.01) in M0 (20.9) and M1 (18.3) than in M2 (11.7), M3 (12.4), M4 (11.8) and M5 (9.5) cytotypes. In addition, bcl-2 MFI significantly correlated both with CD34 positivity (P = 0.001) and with CD34 MFI (P = 0.01), being CD34 antigen expressed in 65% of patients with a bcl-2 MFI >14, and only in 35% of AML cases with a bcl-2 MFI >14. When bcl-2 intensity expression was correlated with complete remission (CR) rate, a higher MFI was associated with a low CR rate after standard intensive chemotherapy. In particular, CR was achieved in 86% of patients with a bcl-2 MFI <14, but only in 57% of patients with a MFI >14 (P = 0.008). A further decrease of CR rate to 41% was observed in patients in whom a higher bcl-2 MFI was coupled with the presence of CD34 antigen on their blasts. By statistical analysis we also demonstrated that both bcl-2 high MFI (>14) and CD34 expression are independent prognostic factors for achieving CR in AML. These data raise the hypothesis that high values of bcl-2 may confer on myeloid blasts a higher resistance to standard chemotherapy. However, identification of patients with high expression of bcl-2 may be important for a different therapeutic approach.

Long-lasting decrease of CD4+/CD45RA+ T cells in HCL patients after 2-chlorodeoxyadenosine (2-CdA) treatment.

The CD45RA and CD45RO isoforms of the leukocyte common antigen identify functionally distinct CD4+ T cell subsets: CD4+/CD45RA+ cells which represent a more 'naive' stage of T cell compartment and CD4+/CD45RO+ 'memory' cells. Phenotypic and functional abnormalities in T cell compartment have been frequently reported in patients with hairy cell leukemia (HCL) and, in more recent studies, a significant reduction in the absolute number of CD4+ lymphocytes bearing the CD45RO antigen has also been recorded. In our study we evaluated the CD45RA and CD45RO expression on CD4+ T cells by three-color staining in flow cytometry in 38 HCL patients, 19 untreated and 19 previously treated with 2-chlorodeoxyadenosine (2-CdA), administered at a daily dose of 0.1 mg/kg c.i. for 7 days. In HCL untreated patients, the proportion and the absolute number of CD4+/CD45RA+ and of CD4+/CD45RO+ T cell subsets were similar to normal controls. In contrast, HCL patients at 3-5 years by the end of treatment with 2-CdA, together with a reduction in the absolute number of CD4+ T cells, showed a persistent and significant decrease in the proportion and absolute number of CD4+/CD45RA+ cells as compared with both untreated HCL patients and normal controls (41 +/- 16% vs 57 +/- 14% and vs 65 +/- 7%) (P = 0.01 and 0.0001) and (0.201 +/- 0.137 x 10(9)/l vs 0.549 +/- 0.238 x 10(9)/l and vs 0.696 +/- 0.078 x 10(9)/l) (P = 0.00009 and P = 0.00001). In addition, together with the reduction of CD4+/CD45RA+ cells, we recorded a concomitant increase in the proportion of the CD4+/CD45RO+ cells as compared to untreated HCL patients and normal controls (62 +/- 16% vs 47 +/- 15% and vs 42 +/- 12%) (P = 0.08 and 0.02). These findings may suggest that CD4+/CD45RA+ cells are more sensitive than CD4+/CD45RO+ to the toxic effect of 2-CdA.

CD56 antigenic expression in acute myeloid leukemia identifies patients with poor clinical prognosis.

CD56 antigen, a 200-220 kDa cell surface glycoprotein, identified as an isoform of the neural adhesion molecules (NCAM), has been found frequently expressed in several lympho-hematopoietic neoplasms including acute myeloid leukemias (AML). In fact, in these latter diseases it has been reported that the presence of CD56 antigen on the blasts of AML patients with t(8;21) (q22;q22), and in those with M3 subtype, identifies a subgroup of patients with a more unfavorable prognosis. On the basis of these findings, we evaluated in 152 newly diagnosed AML patients CD56 surface expression, and results were correlated with morphology, immunophenotype, cytogenetic pattern and clinical outcome. CD56 antigen was recorded in 37 out of 152 cases (24%) and particularly in those with M2 and M5 cytotypes. Moreover, CD56 expression was significantly associated with P-glycoprotein (PGP) hyperexpression (P = 0.007), unfavorable cytogenetic abnormalities (P = 0.008) and with a reduced probability of achieving complete remission (CR) (36% vs 68%) (P = 0.035) as well as with a shorter survival (6 vs 12 months) (P = 0.032). In conclusion, CD56 antigenic expression on AML cells represents an important adverse prognostic factor and therefore its presence should be regularly investigated for a better prognostic assessment of AML patients at diagnosis.

Different reconstitution of peripheral blood lymphocytes and dendritic cells in liver and kidney transplant patients.

T cells and dendritic cells are responsible for immune alloreactivity or tolerance after transplantation. In this study, we compared the levels of circulating T, B, and NK lymphocytes, as well as monocytes, plasmacytoid dendritic cells, and myeloid dendritic cells, in adult patients undergoing a liver transplant or kidney transplant. Our findings show that candidates for liver transplant had significantly lower levels of circulating T, B, and dendritic cells than candidates for kidney transplant. Nevertheless, liver transplant patients showed a greater T-cell recovery, despite the use of thymoglobulin, as compared with kidney transplant patients who were induced with Daclizumab. In four kidney transplant patients with allograft rejection we observed a dramatic drop of circulating T and dendritic cells at the time of rejection, and while myeloid dendritic cells and CD4(+) and CD8(+) cells rapidly recovered after 1 month, plasmacytoid dendritic cells and CD4(+)CD25(+) T-cell numbers remained significantly lower than in patients without rejection. Future studies will evaluate the monitoring of circulating CD4(+)CD25(+) T cells and myeloid dendritic cell:plasmacytoid dendritic cell ratio as potential biomarkers for rejection or, alternatively, for withdrawal of immune suppression.

Tolerance and hematopoietic stem cell transplantation 50 years after Burnet's theory.

OBJECTIVE: In 1949, the original formulation of Burnet's theory on the mechanisms responsible for the capacity of the immune system to discriminate between foreign antigens (i.e., the "non-self") and the cells of its own body (i.e., the "self") was published. Since then, further refinements and reconsiderations of the basic concepts underlying the achievement of a state of tolerance toward a certain antigen have been reported. Here, we attempt to analyze critically new clinical and experimental strategies aimed at inducing alloantigen-specific unresponsiveness. DATA SOURCES: The data discussed in this review are drawn from articles and abstracts published in journals covered by the Science Citation Index and Medline. STATE OF THE ART: Induction of tolerance toward alloantigens still remains one of the most elusive goals of clinical immunology. Until now, nonspecific immunosuppressive drugs have been used to successfully perform both solid organ and hematopoietic stem cell transplantation. However, using this approach, patients given an allograft are exposed to the threat of infections, tumors, and other side effects. Moreover, in solid organ transplant recipients, permanent tolerance toward the graft's alloantigens is never achieved. Recently, considerable progress has been made in expanding our knowledge of transplant tolerance. The traditional model of central tolerance, derived from Burnet's concept, has been complemented by knowledge of mechanisms of peripheral tolerance. CONCLUSIONS: New experimental and therapeutic trials based on the blockade of costimulatory molecules, as well as on generation and infusion of either regulatory or nonimmunogenic cells, have been recently proposed for inducing alloantigen-specific tolerance.The achievements obtained in understanding the mechanisms of unresponsiveness toward non-self antigens are fundamental prerequisites for successful allogeneic transplants, and they could open a new exciting era of specific, immunosuppressive therapies.

Allo-SCT for myelofibrosis: reversing the chronic phase in the JAK inhibitor era?

At present, allo-SCT is the only curative treatment for patients with myelofibrosis (MF). Unfortunately, a significant proportion of candidate patients are considered transplant ineligible due to their poor general condition and advanced age at the time of diagnosis. The approval of the first JAK inhibitor, ruxolitinib, for patients with advanced MF in 2011 has had a qualified impact on the treatment algorithm. The drug affords substantial improvement in MF-associated symptoms and splenomegaly but no major effect on the natural history. There has, therefore, been considerable support for assessing the drug's candidacy in the peritransplant period. The drug's precise impact on clinical outcome following allo-SCT is currently not known; nor are the drug's long-term efficacy and safety known. Considering the rarity of MF and the small proportion of patients who undergo allo-SCT, well designed collaborative efforts are required. In order to address some of the principal challenges, an expert panel of laboratory and clinical experts in this field was established, and an independent workshop held during the 54th American Society of Hematology Annual Meeting in New Orleans, USA on 6 December 2013, and the European Hematology Association's Annual Meeting in Milan, Italy on 13 June 2014. This document summarizes the results of these efforts.

Indication and management of allogeneic stem cell transplantation in primary myelofibrosis: a consensus process by an EBMT/ELN international working group.

The aim of this work is to produce recommendations on the management of allogeneic stem cell transplantation (allo-SCT) in primary myelofibrosis (PMF). A comprehensive systematic review of articles released from 1999 to 2015 (January) was used as a source of scientific evidence. Recommendations were produced using a Delphi process involving a panel of 23 experts appointed by the European LeukemiaNet and European Blood and Marrow Transplantation Group. Key questions included patient selection, donor selection, pre-transplant management, conditioning regimen, post-transplant management, prevention and management of relapse after transplant. Patients with intermediate-2- or high-risk disease and age <70 years should be considered as candidates for allo-SCT. Patients with intermediate-1-risk disease and age <65 years should be considered as candidates if they present with either refractory, transfusion-dependent anemia, or a percentage of blasts in peripheral blood (PB) >2%, or adverse cytogenetics. Pre-transplant splenectomy should be decided on a case by case basis. Patients with intermediate-2- or high-risk disease lacking an human leukocyte antigen (HLA)-matched sibling or unrelated donor, should be enrolled in a protocol using HLA non-identical donors. PB was considered the most appropriate source of hematopoietic stem cells for HLA-matched sibling and unrelated donor transplants. The optimal intensity of the conditioning regimen still needs to be defined. Strategies such as discontinuation of immune-suppressive drugs, donor lymphocyte infusion or both were deemed appropriate to avoid clinical relapse. In conclusion, we provided consensus-based recommendations aimed to optimize allo-SCT in PMF. Unmet clinical needs were highlighted.

Expression of P21(WAF1/CIP1/SID1) cyclin-dependent kinase inhibitor in hematopoietic progenitor cells.

P21(Waf1/Cip1/Sid1) is a critical component of biomolecular pathways leading to the G(1) arrest evoked in response to DNA damage, growth arrest signals and differentiation commitment. It belongs to the Cip/Kip class of cyclin-dependent kinase inhibitors and is at least partly regulated by p53. P21(Waf1/Cip1/Sid1) functional inactivation possibly resulting from mutations of the gene itself or, more likely, from p53 mutations may be critical for either the cell fate following DNA-damaging insults or clonal evolution toward malignancy. In the study presented here we describe a competitive polymerase chain reaction (PCR) strategy whose sensitivity and reproducibility enable us to attain a precise quantitation of p21(Waf1/Cip1/Sid1) expression levels in hematopoietic progenitors, the cell compartment which mostly suffers from the side effects of genotoxic drugs in use for cancer cure. The strategy was set in the M07 factor-dependent hematopoietic progenitor cell line. We confirmed that its p21(waf1/cip1/sid1) constitutive expression level is very low and up-modulated by DNA-damaging agents: ionizing radiations and ultraviolet light. Gene up-modulation resulted in checkpoint activation and, in particular, in a significant G(1) arrest, required for either the repair of damaged DNA sequences or apoptotic cell death. Our competitive PCR strategy was further validated in CD34(+) purified hematopoietic progenitors from healthy donors mobilized into the peripheral blood by granulocyte colony-stimulating factor and intended for allogeneic bone marrow transplantation. The constitutive p21(WAF1/CIP1/SID1) expression levels, measured in three separate harvests, were very low and no significant differences were apparent. Our results support the use of a competitive PCR strategy as a useful tool for clinical purposes, to assess the individual biomolecular response of early hematopoietic progenitors to antiblastic drugs.

Incidence and prognostic relevance of CD34 expression in acute myeloblastic leukemia: analysis of 141 cases.

In 141 adult patients with diagnosis of acute myeloid leukemia the overall expression and intensity of expression of CD34 antigen on leukemic cells was investigated. Myeloid blasts were tested by applying direct immunofluorescence staining using anti-CD34 fluorescein monoclonal antibody in flow cytometry. CD34 antigen was found in 73 out of 141 (51%) cases and in particular in M0, M1 and M4 French-American-British (FAB) cytotypes, while M3 and M5 cases were rarely positive. In patients whose blasts expressed CD34 antigen a significantly lower rate of complete remission (CR) was observed as opposed to CD34 negative cases (61% vs 88%) (P = 0.001). Furthermore, a negative correlation between high intensity of CD34 expression, measured as a mean fluorescence index (MFI), and CR rate was observed. In particular, patients with a higher CD34 fluorescence intensity (MFI > 23), showed a further reduction in CR rate (48%). Also, these patients had a significantly lower overall survival (P = 0.03) as compared to patients with no expression of CD34 and patients with CD34 MFI < 23. In conclusion, these findings confirm that CD34 expression is frequently associated with "immature" FAB cytotypes (M0, M1 and M4) and with a reduced probability to achieve CR. Furthermore, a high CD34 intensity of expression should be considered as a reliable poor prognostic factor.

Biological characterization of CD34+ cells mobilized into peripheral blood.

We review here the functional and kinetic characteristics of highly purified hematopoietic CD34+ mobilized into peripheral blood (PB) by granulocyte colony-stimulating factor (G-CSF) with or without chemotherapy for autologous or allogeneic transplantation. Circulating CD34+ cells were evaluated for their colony-forming capacity and trilineage proliferative response to selected recombinant human (rh) CSF in vitro, and the content of very primitive long-term culture initiating cells (LTC-IC). In addition, the cycling status of PB CD34+ cells, including committed clonogenic progenitor cells and the more immature LTC-IC, was determined by the cytosine arabinoside (Ara-C) suicide test and the acridine orange (AO) flow cytometric technique. By comparison, bone marrow (BM) CD34+ cells from the same individuals were studied under steady-state conditions and during G-CSF administration. Clonogenic assays in methylcellulose showed the same frequency of colony-forming unit cells (CFU-C) when PB primed-CD34+ cells and BM cells were stimulated with phytohemagglutinin-lymphocyte-conditioned medium (PHA-LCM). However, mobilized CD34+ cells were significantly more responsive than their steady-state BM counterparts to interleukin-3 (IL-3) and stem cell factor (SCF) combined with G-CSF or IL-3 in the presence of erythropoietin (Epo). Conversely, circulating and BM megakaryocyte precursors (CFU-MK) showed the same clonogenic efficiency in response to IL-3, GM-CSF and IL-3, IL-6 and Epo. Interestingly, very few CD34+ cells expressed the Mpl receptor and this finding resulted in the lower proliferative response of mobilized CFU-MK to the Mpl-ligand (megakaryocyte growth and development factor; MGDF), as compared to BM cells. After 5 weeks of liquid culture supported by the engineered murine stromal cell line M2-10B4 to produce G-CSF and IL-3, we reported a similar frequency of LTC-IC in PB and steady-state BM. Kinetic studies on PB and BM CD34+ cells, including LTC-IC, showed the low number of circulating progenitor cells in S and G2M phase whereas simultaneous DNA/RNA analysis and the Ara-C suicide assay demonstrated that the majority of PB CD34+ cells and LTC-IC are not quiescent (ie in G0 phase) being in G1 phase. Moreover, G-CSF administration prevented apoptosis in a small but significant proportion of mobilized CD34+ cells. Thus, our results indicate that mobilized and BM CD34+ cells can be considered equivalent for the frequency of both committed and more immature hematopoietic progenitor cells, although they show different kinetic and functional profiles. A further set of experiments indicated that G-CSF treatment did not alter the alloantigen presenting function of CD34+ cells which was mainly mediated by the upregulation of costimulatory molecules upon coincubation with allogeneic T cells. Taken together, these findings should allow a better understanding of PBSC transplantation.

Use of anti-BDCA-2 antibody for detection of dendritic cells type-2 (DC2) in allogeneic hematopoietic stem cell transplantation.

TH2-inducing dendritic cells (DC2) are commonly identified as negative for lineage markers and positive for HLA-DR and CD123 expression. More recently, normal blood DC2 were shown also to be positive for BDCA-2 and BDCA-4 antigens. The aim of this study was to evaluate whether BDCA-2 expression on DC2 is impaired in patients undergoing an allogeneic hematopoietic stem cell transplantation (HSCT) and in healthy donors treated with G-CSF for HSC mobilization. Flow cytometry assays for DC2 detection using either a triple staining with anti-HLA-DR PerCP, anti-Lin(+) anti-CD34 FITC and anti-CD123 PE monoclonal antibodies (mAbs), or a double staining with anti-HLA-DR PE and anti-BDCA-2 FITC mAbs were compared in blood samples from patients who underwent an allogeneic HSCT (n = 30) or from healthy donors before (n = 11) and after (n = 8) G-CSF mobilization, as well as in healthy donors' leukapheresis products (n = 12) or bone marrow (n = 4). Staining of BDCA-2(+) cells with other markers such as anti-CD38, anti-CD54 and anti-CD58 were also performed. Median values of CD123(+) DC2 and BDCA-2(+) DC2 were not statistically different in the blood of patients previously treated with chemotherapy, nor in the blood or bone marrow of heathy donors. Also, a 5 day G-CSF treatment did not affect BDCA-2 or adhesion molecule expression on healthy donors' blood DC2 significantly. A correlation between all the results (n = 65) obtained with the two assays was demonstrated in a linear regression curve (r = 0.914) (P = 0.00001). BDCA-2 is a marker highly specific for DC2 that is not downregulated by chemotherapy or G-CSF treatment. Therefore, the anti-BDCA-2 mAb can be efficiently combined with other mAbs and used in studies addressing the role of DC2 in the allogeneic HSCT setting.

Reduced incidence of GVHD without increase in relapse with low-dose rabbit ATG in the preparative regimen for unrelated bone marrow transplants in CML.

SUMMARY: Antithymocyte globulin (ATG) treatment prevents graft failure and results in a low incidence of GVHD, but an increased risk of relapse could be expected as a consequence of reduced GVHD. From September 1995 to June 2001, 28 consecutive chronic myeloid leukemia (CML) patients underwent unrelated bone marrow transplants: 21 were in chronic phase (CP) and seven in advanced phase (AP). Median age was 35.5 years (range 20-50). HLA typing was based on high-resolution molecular techniques; in eight cases there were one or more allele mismatches. The preparative regimen consisted of TBI, EDX 120 mg/kg and rabbit ATG 15 mg/kg. All patients engrafted and no rejection occurred. Acute GVHD grade III-IV occurred in six patients (21%). Chronic GVHD occurred in 10 (40%) and it was extensive in one. Four out of seven patients transplanted in AP had a hematological relapse. Of 21 in CP, there was one cytogenetic and one molecular relapse: these two patients are now in complete remission with imatinib mesylate. With a median follow-up of 45.7 months, the 5-year survival is 76.2% for those transplanted in CP. These data demonstrate that transplants performed in CP, with low-dose ATG, are associated with a good outcome, low incidence of GVHD and no increase of relapse.