Primary analysis of a phase II open-label trial of INCB039110, a selective JAK1 inhibitor, in patients with myelofibrosis.

Combined Janus kinase 1 (JAK1) and JAK2 inhibition therapy effectively reduces splenomegaly and symptom burden related to myelofibrosis but is associated with dose-dependent anemia and thrombocytopenia. In this open-label phase II study, we evaluated the efficacy and safety of three dose levels of INCB039110, a potent and selective oral JAK1 inhibitor, in patients with intermediate- or high-risk myelofibrosis and a platelet count ≥50×109/L. Of 10, 45, and 32 patients enrolled in the 100 mg twice-daily, 200 mg twice-daily, and 600 mg once-daily cohorts, respectively, 50.0%, 64.4%, and 68.8% completed week 24. A ≥50% reduction in total symptom score was achieved by 35.7% and 28.6% of patients in the 200 mg twice-daily cohort and 32.3% and 35.5% in the 600 mg once-daily cohort at week 12 (primary end point) and 24, respectively. By contrast, two patients (20%) in the 100 mg twice-daily cohort had ≥50% total symptom score reduction at weeks 12 and 24. For the 200 mg twice-daily and 600 mg once-daily cohorts, the median spleen volume reductions at week 12 were 14.2% and 17.4%, respectively. Furthermore, 21/39 (53.8%) patients who required red blood cell transfusions during the 12 weeks preceding treatment initiation achieved a ≥50% reduction in the number of red blood cell units transfused during study weeks 1-24. Only one patient discontinued for grade 3 thrombocytopenia. Non-hematologic adverse events were largely grade 1 or 2; the most common was fatigue. Treatment with INCB039110 resulted in clinically meaningful symptom relief, modest spleen volume reduction, and limited myelosuppression.

Skeletal muscle radio-density is an independent predictor of response and outcomes in follicular lymphoma treated with chemoimmunotherapy.

Skeletal muscle radio-density (SMD) measures muscle radiation attenuation (in Hounsfield Units, HU) on computed tomography (CT) scans. Low SMD is prognostic of poor survival in melanoma, however its significance is unknown for hematologic malignancies. We performed a single institution, retrospective review of all follicular lymphoma (FL) patients who received chemoimmunotherapy from 2004-2009. Patient demographics, FL International Prognostic Index 1 (FLIPI-1), progression free (PFS) and overall survival (OS) were collected as primary endpoints. Objective response rates (ORR) were secondary. SMD was calculated using pre-treatment CT scans. In 145 patients reviewed, median values were age 59, FLIPI-1 of 2, stage III, and 8 chemoimmunotherapy cycles received. Median PFS for those with low SMD (<36.6 and <33.1 HU for patients with BMI ≤ 25 and > 25 kg/m2, respectively) compared to those with high SMD was profoundly worse, 69.6 vs. 106.7 months (hazard ratio [HR] 1.85; p = 0.01), respectively. Median OS was not reached in patients with high SMD vs. 92.7 months in low SMD patients (HR 4.02; p = 0.0002). Multivariate analysis supported lower SMD's OS detriment (HR = 3.40; p = 0.002) independent of FLIPI-1 (HR 1.46-2.76, p = 0.05) or gender. Low SMD predicted lower ORR, 83 vs. 96% (p = 0.01). SMD predicts survival independent of FLIPI-1 and potentially chemoimmunotherapy response. SMD is an inexpensive and powerful tool that can complement FLIPI-1.

Salvage chemotherapy and autologous stem cell transplantation for transformed indolent lymphoma: a subset analysis of NCIC CTG LY12.

The treatment of transformed indolent lymphoma (TRIL) often includes salvage chemotherapy (SC) and autologous stem cell transplant (ASCT). NCIC CTG LY12 is a randomized phase 3 trial comparing gemcitabine, dexamethasone, and cisplatin (GDP) with dexamethasone, cytarabine, and cisplatin (DHAP) before ASCT. This analysis compares the results of SC and ASCT for TRIL with de novo diffuse large B-cell lymphoma (DLBCL). Six-hundred nineteen patients with relapsed/refractory aggressive non-Hodgkin lymphoma were randomized to GDP or DHAP; 87 patients (14%) had TRIL and 429 (69%) had DLBCL. The response rate to SC was 47% in TRIL and 45% in DL (P = .81). Transplantation rates were similar: TRIL 53% and DL 52% (P = 1.0). With a median follow-up of 53 months, 4 year overall survival was 39% for TRIL and 41% for DL (P = .78); 4 year event-free survival (EFS) was 27% for TRIL and 27% for DL (P = .83). Post-ASCT, 4-year EFS was 45% for TRIL and 46% for DL. Histology (TRIL or DL) was not a predictor of any outcome in multivariate models. Patients with relapsed or refractory TRIL and DLBCL have similar outcomes with SC and ASCT; this therapy should be considered the standard of care for patients with TRIL who have received prior systemic chemotherapy. NCIC CTG LY12 is registered at ClinicalTrials.gov as #NCT00078949.

Randomized comparison of gemcitabine, dexamethasone, and cisplatin versus dexamethasone, cytarabine, and cisplatin chemotherapy before autologous stem-cell transplantation for relapsed and refractory aggressive lymphomas: NCIC-CTG LY.12.

PURPOSE: For patients with relapsed or refractory aggressive lymphoma, we hypothesized that gemcitabine-based therapy before autologous stem-cell transplantation (ASCT) is as effective as and less toxic than standard treatment. PATIENTS AND METHODS: We randomly assigned 619 patients with relapsed/refractory aggressive lymphoma to treatment with gemcitabine, dexamethasone, and cisplatin (GDP) or to dexamethasone, cytarabine, and cisplatin (DHAP). Patients with B-cell lymphoma also received rituximab. Responding patients proceeded to stem-cell collection and ASCT. Coprimary end points were response rate after two treatment cycles and transplantation rate. The noninferiority margin for the response rate to GDP relative to DHAP was set at 10%. Secondary end points included event-free and overall survival, treatment toxicity, and quality of life. RESULTS: For the intention-to-treat population, the response rate with GDP was 45.2%; with DHAP the response rate was 44.0% (95% CI for difference, -9.0% to 6.7%), meeting protocol-defined criteria for noninferiority of GDP (P = .005). Similar results were obtained in a per-protocol analysis. The transplantation rates were 52.1% with GDP and 49.3% with DHAP (P = .44). At a median follow-up of 53 months, no differences were detected in event-free survival (HR, 0.99; stratified log-rank P = .95) or overall survival (HR, 1.03; P = .78) between GDP and DHAP. Treatment with GDP was associated with less toxicity (P < .001) and need for hospitalization (P < .001), and preserved quality of life (P = .04). CONCLUSION: For patients with relapsed or refractory aggressive lymphoma, in comparison with DHAP, treatment with GDP is associated with a noninferior response rate, similar transplantation rate, event-free survival, and overall survival, less toxicity and hospitalization, and superior quality of life.

Hypoxia differentially upregulates the expression of embryonic, fetal and adult hemoglobin in human glioblastoma cells.

Hemoglobin is produced mainly in erythroid cells. However, it has been reported in non-erythroid cells of human and rodents. We have shown previously that neuroglobin, cytoglobin and hemoglobin are expressed in human glioblastoma multiforme (GBM) cells. We sought to determine whether hemoglobin expression is upregulated by hypoxia, and whether its expression is restricted to the cancer stem cell populations in different GBM cell lines or GBM brain tumor initiating cells (BTICs). Flow cytometry, magnetic cell sorting and qRT-PCR were used to examine the hypoxic upregulation of hemoglobins as well as erythropoietin (EPO) and erythropoietin receptor (EPOR) in GBM cell lines (M006x, M059J, M059K, U87R and U87T) and GBM-BTICs. The data showed significantly increased expression in globins (α, ß, γ, δ, ζ and ε), EPO and EPOR mRNA levels under hypoxia. Globin expression is not limited to the stem cell populations or GBM-BTICs but is a property of the entire GBM population. We assumed that the total expression of mRNA of different normalized globins (α, ß, γ, δ, ζ and ε) at different time­points for the same cell line is 100%. Under aerobic conditions, ε globin was predominantly expressed, and then decreased gradually with increasing time in hypoxia. This was coupled to a concomitant increase in α and γ globins. Our findings suggest that hypoxic upregulation of hemoglobin expression in GBM cells may be a part of a repertoire of active defence and adaptation mechanisms enabling these cells to acquire resistance to aggressive multimodality treatments of chemotherapy and radiotherapy. New therapeutic strategies to interfere with hemoglobin expression or function in GBM cells are required.

Adult, embryonic and fetal hemoglobin are expressed in human glioblastoma cells.

Hemoglobin is a hemoprotein, produced mainly in erythrocytes circulating in the blood. However, non-erythroid hemoglobins have been previously reported in other cell types including human and rodent neurons of embryonic and adult brain, but not astrocytes and oligodendrocytes. Human glioblastoma multiforme (GBM) is the most aggressive tumor among gliomas. However, despite extensive basic and clinical research studies on GBM cells, little is known about glial defence mechanisms that allow these cells to survive and resist various types of treatment. We have shown previously that the newest members of vertebrate globin family, neuroglobin (Ngb) and cytoglobin (Cygb), are expressed in human GBM cells. In this study, we sought to determine whether hemoglobin is also expressed in GBM cells. Conventional RT-PCR, DNA sequencing, western blot analysis, mass spectrometry and fluorescence microscopy were used to investigate globin expression in GBM cell lines (M006x, M059J, M059K, M010b, U87R and U87T) that have unique characteristics in terms of tumor invasion and response to radiotherapy and hypoxia. The data showed that α, ß, γ, δ, ζ and ε globins are expressed in all tested GBM cell lines. To our knowledge, we are the first to report expression of fetal, embryonic and adult hemoglobin in GBM cells under normal physiological conditions that may suggest an undefined function of those expressed hemoglobins. Together with our previous reports on globins (Ngb and Cygb) expression in GBM cells, the expression of different hemoglobins may constitute a part of series of active defence mechanisms supporting these cells to resist various types of treatments including chemotherapy and radiotherapy.

Establishing a target exposure for once-daily intravenous busulfan given with fludarabine and thymoglobulin before allogeneic transplantation.

A combination of fludarabine (Flu) and daily i.v. busulfan (Bu) is well tolerated and effective in patients undergoing allogeneic hematopoietic stem cell transplantation. Although there is some evidence that Bu exposures exceeding 6000 µM.min [corrected] may lead to excessive toxicity, there is little information on the effect of exposures below this level on outcomes. We studied Bu exposure, as measured by area under the concentration-time curve (AUC), in 158 patients with various hematologic malignancies in an attempt to identify an optimal range for targeted therapy. The preparative chemotherapy regimen comprised Flu 50 mg/m(2) on days -6 to -2 and i.v. Bu 3.2 mg/kg on days -5 to -2 inclusive. Graft-versus-host disease (GVHD) prophylaxis included methotrexate, cyclosporin A, and antithymocyte globulin. Patients with Bu exposures below the median AUC of 4439 µM.min [corrected] were at increased risk for acute GVHD grade II-IV (hazard ratio [HR], 2.30; 95% confidence interval [CI], 1.19 to 4.49; P = .014). Those in the highest and lowest Bu exposure quartiles (daily AUC <3814 µM.min and >4993 µM.min) [corrected] had an increased risk of nonrelapse mortality (subdistribution HR, 3.32; 95% CI, 1.46 to 7.54; P = .004), as well as worse disease-free survival (HR, 1.81; 95% CI, 1.09 to 2.99; P = .021) and overall survival (HR, 1.94; 95% CI, 1.12 to 3.37; P = .018). Bu exposures between 4440 and 4993 µM/min were accompanied by the lowest risk of both nonrelapse mortality and acute GVHD.

Emerging therapeutic options for myelofibrosis: a Canadian perspective.

Myelofibrosis (MF) is a clonal stem cell disorder characterized by cytopenias, splenomegaly, marrow fibrosis, and systemic symptoms due to elevated inflammatory cytokines. MF is associated with decreased survival. The quality of life of patients with MF is similar to other advanced malignancies. Allogeneic hematopoietic cell transplantation is a curative treatment, but is applicable to a minority of patients with MF. None of the conventional therapies are known to alter the natural history of the disease. Significant progress has been made in the last few years in the understanding of disease biology of MF. Discovery of the JAK2V617F mutation paved the way for drug discovery in MF, and the first JAK1/2 inhibitor, ruxolitinib, has been approved by FDA and Health Canada. Several other JAK1/2 inhibitors are at various stages of clinical development. As a consequence, the therapeutic landscape of MF is changing from a disease where no effective therapies existed to one with several novel treatment options on the horizon. In this report, we assess the changing therapeutic options for MF, and critically analyze the position of novel treatments in the current armamentarium.

A randomized trial of dasatinib 100 mg versus imatinib 400 mg in newly diagnosed chronic-phase chronic myeloid leukemia.

Tyrosine kinase inhibitor therapy with imatinib (IM), dasatinib (DAS), or nilotinib is very effective in chronic-phase chronic myeloid leukemia. Two hundred fifty-three patients with newly diagnosed chronic-phase chronic myeloid leukemia were randomized to IM 400 mg/day or DAS 100 mg/day. The proportion of patients achieving a complete cytogenetic remission rate was superior with DAS (84% vs 69%), as was the 12-month molecular response by the proportions of patients achieving > 3-log, > 4-log, and > 4.5-log reduction in BCR-ABL transcript levels. Overall and progression-free survival was similar in the 2 arms. Among patients who achieved hematologic CR, 3-year relapse-free survival was 91% with DAS and 88% with IM 400 mg. Grade 3 and 4 toxicities were most commonly hematologic, including thrombocytopenia in 18% and 8% of DAS and IM patients, respectively. DAS induced more complete cytogenetic response and deeper molecular responses after 12 months, compared with IM 400 mg, and with a median follow-up of 3.0 years there have been very few deaths, relapses, or progressions in the 2 arms. In summary, DAS compared with IM appeared to have more short-term cytogenetic and molecular response, more hematologic toxicity, and similar overall survival. This trial is registered at www.clinicaltrials.gov as NCT00070499.

Fludarabine, busulfan, antithymocyte globulin, and total body irradiation for pretransplantation conditioning in acute lymphoblastic leukemia: excellent outcomes in all but older patients with comorbidities.

Hematopoietic stem cell transplantation (SCT) is routinely offered to suitable candidates with high-risk or advanced acute lymphoblastic leukemia (ALL). In this report, we update our experience with SCT in patients with ALL with a novel conditioning regimen. A total of 44 patients with high-risk or advanced (greater than first complete remission) ALL in remission underwent SCT after myeloablative conditioning with fludarabine + busulfan + total body irradiation. The median follow-up of surviving patients was 4.3 years (range, 1.0-9.0 years). The cohort consists of 32 patients with high-risk disease (median age, 40 years; range, 19-64 years) and 12 patients with advanced disease (median age, 25 years; range, 19-65 years) who underwent SCT: 25 with a related donor (21 fully matched) and 19 with an unrelated donor (16 fully matched). The cumulative incidence of grade II-IV acute graft-versus-host disease (GVHD) was 53.2%, and that of grade III-IV acute GVHD was 20.6%. The incidence of chronic GVHD was 55%. The 100-day nonrelapse mortality was 13.6%. Five-year progression-free survival was 56.7%, and 5-year overall survival was 66.0%. Nine patients (20%) died in remission, 6 (14%) died after relapse, and 2 survived after a second SCT for relapsed disease. Outcomes were inferior in older patients with comorbidities compared with other patients.

Membrane Type-1 Matrix Metalloproteinase Expression in Acute Myeloid Leukemia and Its Upregulation by Tumor Necrosis Factor-α.

Membrane type-1 matrix metalloproteinase (MT1-MMP) has been implicated in tumor invasion, as well as trafficking of normal hematopoietic cells, and acts as a physiologic activator of proMMP-2. In this study we examined MT1-MMP expression in primary acute myeloid leukemia (AML) cells. Because tumor necrosis factor (TNF)-α is known to be elevated in AML, we also investigated the effect of TNF-α on MT1-MMP expression. We found (i) MT1-MMP mRNA expression in 41 out of 43 primary AML samples tested; (ii) activation of proMMP-2 in co-cultures of AML cells with normal bone marrow stromal cells; and (iii) inhibition of proMMP-2 activation and trans-Matrigel migration of AML cells by gene silencing using MT1-MMP siRNA. Moreover, recombinant human TNF-α upregulated MT1-MMP expression in AML cells resulting in enhanced proMMP-2 activation and trans-Matrigel migration. Thus, AML cells express MT1-MMP and TNF-α enhances it leading to increased MMP-2 activation and most likely contributing to the invasive phenotype. We suggest that MT1-MMP, together with TNF-α, should be investigated as potential therapeutic targets in AML.

The ins and outs of hematopoietic stem cells: studies to improve transplantation outcomes.

Deciphering the mechanisms of hematopoietic stem/progenitor cell (HSPC) mobilization and homing is important for the development of strategies to enhance the efficacy of HSPC transplantation and achieve the full potential of HSPC-based cellular therapy. Investigation of these mechanisms has revealed interdependence among the various molecules, pathways and cellular components involved, and underscored the complex nature of these two processes. This review summarizes recent progress in identifying the specific factors implicated in HSPC mobilization and homing, with emphasis on our own work. Particularly, we will discuss our studies on stromal cell-derived factor-1 and its interaction with its receptor CXCR4, proteases (matrix metalloproteinases and carboxypeptidase M), complement proteins (C1q, C3a, C5a, membrane attack complex), sphingosine-1-phosphate, and pharmacologic agents such as the histone deacetylase inhibitor valproic acid and hyaluronic acid.

Hypoxic regulation of cytoglobin and neuroglobin expression in human normal and tumor tissues.

BACKGROUND: Cytoglobin (Cygb) and neuroglobin (Ngb) are recently identified globin molecules that are expressed in vertebrate tissues. Upregulation of Cygb and Ngb under hypoxic and/or ischemic conditions in vitro and in vivo increases cell survival, suggesting possible protective roles through prevention of oxidative damage. We have previously shown that Ngb is expressed in human glioblastoma multiforme (GBM) cell lines, and that expression of its transcript and protein can be significantly increased after exposure to physiologically relevant levels of hypoxia. In this study, we extended this work to determine whether Cygb is also expressed in GBM cells, and whether its expression is enhanced under hypoxic conditions. We also compared Cygb and Ngb expression in human primary tumor specimens, including brain tumors, as well as in human normal tissues. Immunoreactivity of carbonic anhydrase IX (CA IX), a hypoxia-inducible metalloenzyme that catalyzes the hydration of CO2 to bicarbonate, was used as an endogenous marker of hypoxia. RESULTS: Cygb transcript and protein were expressed in human GBM cells, and this expression was significantly increased in most cells following 48 h incubation under hypoxia. We also showed that Cygb and Ngb are expressed in both normal tissues and human primary cancers, including GBM. Among normal tissues, Cygb and Ngb expression was restricted to distinct cell types and was especially prominent in ductal cells. Additionally, certain normal organs (e.g. stomach fundus, small bowel) showed distinct regional co-localization of Ngb, Cygb and CA IX. In most tumors, Ngb immunoreactivity was significantly greater than that of Cygb. In keeping with previous in vitro results, tumor regions that were positively stained for CA IX were also positive for Ngb and Cygb, suggesting that hypoxic upregulation of Ngb and Cygb also occurs in vivo. CONCLUSIONS: Our finding of hypoxic up-regulation of Cygb/Ngb in GBM cell lines and human tumor tissues suggests that these globin molecules may be part of the repertoire of defense mechanisms that allow cancer cells to survive in hypoxic microenvironments.

MT1-MMP association with membrane lipid rafts facilitates G-CSF--induced hematopoietic stem/progenitor cell mobilization.

OBJECTIVE: Soluble matrix metalloproteinases (MMPs) facilitate the egress of hematopoietic stem/progenitor cells (HSPC) from the bone marrow (BM) during granulocyte colony-stimulating factor (G-CSF)-induced mobilization. Because membrane-type (MT)1-MMP, which is localized on the leading edge of migrating cells, activates the latent forms of soluble MMPs, we investigated its role in HSPC mobilization. MATERIALS AND METHODS: We examined the effect of G-CSF on the expression of MT1-MMP and its activities (proMMP-2 activation and migration) in hematopoietic cells. We also investigated the subcellular localization of MT1-MMP and the signaling pathways that regulate its expression and function in hematopoietic cells after exposure to G-CSF. RESULTS: We found that G-CSF increases MT1-MMP transcription and protein synthesis in hematopoietic cells; proMMP-2 activation in cocultures of HSPC with BM fibroblasts; chemoinvasion across reconstituted basement membrane Matrigel toward a stromal cell-derived factor-1 gradient, which is reduced by small interfering RNA silencing of MT1-MMP; and localization of MT1-MMP to membrane lipid rafts through a mechanism that is regulated by the phosphatidylinositol 3-kinase signaling pathway. Disruption of raft formation (by the cholesterol-sequestering agent methyl-beta-cyclodextrin) abrogated phosphatidylinositol 3-kinase phosphorylation and MT1-MMP incorporation into lipid rafts resulting in reduced proMMP-2 activation and HSPC migration. CONCLUSION: G-CSF-induced upregulation of MT1-MMP in hematopoietic cells and its enhanced incorporation into membrane lipid rafts contributes to proMMP-2 activation, which facilitates mobilization of HSPC.

Fifth complement cascade protein (C5) cleavage fragments disrupt the SDF-1/CXCR4 axis: further evidence that innate immunity orchestrates the mobilization of hematopoietic stem/progenitor cells.

OBJECTIVE: Having previously demonstrated that the complement system modulates mobilization of hematopoietic stem/progenitor cells (HSPC) in mice, we investigated the involvement of C5 cleavage fragments (C5a/(desArg)C5a) in human HSPC mobilization. MATERIALS AND METHODS: C5 cleavage fragments in the plasma were evaluated by enzyme-linked immunosorbent assay using human anti-(desArg)C5a antibody, and expression of the C5a/(desArg)C5a receptor (CD88) in hematopoietic cells by flow cytometry. We also examined the chemotactic responses of hematopoietic cells to C5 cleavage fragments and expression of stromal cell-derived factor-1 (SDF-1)-degrading proteases that perturb retention of HSPC in bone marrow, namely matrix metalloproteinase (MMP)-9, membrane type (MT) 1-MMP, and carboxypeptidase M. RESULTS: We found that plasma levels of (desArg)C5a are significantly higher in patients who are good mobilizers and correlate with CD34(+) cell and white blood cell counts in mobilized peripheral blood. C5 cleavage fragments did not chemoattract myeloid progenitors (colony-forming unit granulocyte-macrophage), but (desArg)C5a did strongly chemoattract mature nucleated cells. Consistently, CD88 was not detected on CD34(+) cells, but appeared on more mature myeloid precursors, monocytes, and granulocytes. Moreover, granulocyte colony-stimulating factor-mobilized peripheral blood mononuclear cells and polymorphonuclear cells had a significantly higher percentage of cells expressing CD88 than nonmobilized peripheral blood. Furthermore, C5a stimulation of granulocytes and monocytes decreased CXCR4 expression and chemotaxis toward an SDF-1 gradient and increased secretion of MMP-9 and expression of MT1-MMP and carboxypeptidase M. CONCLUSION: C5 cleavage fragments not only induce a highly proteolytic microenvironment in human bone marrow, which perturbs retention through the CXCR4/SDF-1 axis, but also strongly chemoattracts granulocytes, promoting their egress into mobilized peripheral blood, which is crucial for subsequent mobilization of HSPC.

The addition of 400 cGY total body irradiation to a regimen incorporating once-daily intravenous busulfan, fludarabine, and antithymocyte globulin reduces relapse without affecting nonrelapse mortality in acute myelogenous leukemia.

A combination of fludarabine (Flu) and daily i.v. busulfan (Bu) is well tolerated and effective in patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT) for acute myelogenous leukemia (AML). The addition of rabbit antithymocyte globulin (ATG) may reduce morbidity and mortality from graft-versus-host disease (GVHD), but lead to increased relapse. To compensate for this effect, we added 400 cGy of total body irradiation (TBI) to the Flu/Bu regimen in 89 patients, and compared outcomes with those achieved in 90 patients who received the drug combination alone. Although nonrelapse mortality (NRM) at 3 years did not differ between the groups, the inclusion of TBI significantly reduced relapse (hazard ratio [HR] = 0.29; 95% confidence interval [CI] = 0.15-0.54; P = .0001). Consequently, both overall survival (OS; HR = 0.50; 95% CI = 0.3-0.84; P = .009) and disease-free survival (DFS; HR = 0.43; 95% CI = 0.26-0.72; P = .001) were improved with the inclusion of TBI. This study confirms the importance of regimen intensity in allogeneic HSCT for AML. The combination of daily i.v. Bu, Flu, 400 cGy TBI, and ATG provides a well-tolerated regimen with antileukemic activity in AML comparable to that of other, conventional myeloablative (MA) regimens.

The HGF/c-Met axis synergizes with G-CSF in the mobilization of hematopoietic stem/progenitor cells.

As granulocyte-colony-stimulating factor (G-CSF)-induced mobilization of hematopoietic stem/progenitor cells (HSPCs) increases human serum levels of hepatocyte growth factor (HGF), our aim was to investigate the role of HGF and its receptor, c-Met, in the mobilization of HSPC. CD34(+) cells and leukocytes were isolated from the bone marrow (BM) of normal donors and the peripheral blood (PB) of patients mobilized with G-CSF and chemotherapy. Plasma HGF levels were evaluated by ELISA and HGF and c-Met expression by RT-PCR, fluorescence-activated cell sorter (FACS) analysis, and confocal microscopy. Because matrix metalloproteinases (MMPs) facilitate migration across extracellular matrix (ECM) and basement membranes, we also examined expression of MMP-9 and membrane type 1 (MT1)-MMP in hematopoietic cells after HGF stimulation. We found that plasma HGF levels in mobilized (m)PB were higher in patients who are good mobilizers and correlated with their white blood cell (WBC) and CD34(+) cell counts. Moreover, HGF and c-Met expression was significantly higher in mPB CD34(+) cells and leukocytes than in their steady-state BM counterpart cells and was up-regulated by G-CSF. Like G-CSF, HGF increased the secretion of MMP-9 and the expression of MT1-MMP in leukocytes, which was abrogated by the c-Met inhibitor K-252a. This inhibitor also significantly reduced the trans-Matrigel migration of mPB CD34(+) cells toward HGF. Our results suggest that G-CSF-mediated HSPC mobilization occurs in part through the HGF/c-Met axis in HSPC and myeloid cells, eliciting increased production of matrix-degrading enzymes and subsequently facilitating egress of HSPC.

Valproic acid increases CXCR4 expression in hematopoietic stem/progenitor cells by chromatin remodeling.

A major limitation of cord blood (CB) hematopoietic stem/progenitor cell (HSPC) transplantation in adult patients is the low cell dose available, which is associated with delayed or failed engraftment. This has prompted intensive research to develop novel strategies to improve HSPC engraftment and reconstitution. The chemokine receptor CXCR4 and its ligand stromal cell-derived factor (SDF)-1alpha play a crucial role in the homing and repopulation capacity of HSPCs. We hypothesized that in HSPCs the CXCR4 receptor is regulated through chromatin remodeling by histone deacetylase inhibitors (HDIs) such as valproic acid (VPA). Using CB CD34(+) cells and the models of immature hematopoietic cells expressing CD34 antigen, namely the leukemic cell lines KG-1a and KG-1, we found that VPA increases surface and mRNA CXCR4 levels in these cells, thereby enhancing their migration toward an SDF-1alpha gradient. We also found that modulation of CXCR4 gene transcription by VPA correlates with the acetylation status of histone H4 in CB CD34(+) and KG-1 cells. Hence we suggest that in CB transplantation priming of HSPCs with VPA could improve homing and engraftment.