John Mascarenhas

Modulation of NF-κB Activity and Apoptosis in Chronic Lymphocytic Leukemia B Cells

Chronic lymphocytic leukemia (CLL) is an indolent malignancy of CD5+ B lymphocytes. CLL cells express CD40, a key regulator of B cell proliferation, differentiation, and survival. In nonmalignant B cells, CD40 ligation results in nuclear translocation and activation of NF-κB proteins. Based on observations that in some CLL cases, the tumor cells express both CD40 and its ligand, CD154 (CD40 ligand), we proposed a model for CLL pathogenesis due to CD40 ligation within the tumor. To evaluate this issue, we used freshly isolated CLL B cells to examine constitutive and inducible NF-κB activity by electrophoretic mobility shift assay. We consistently observed high levels of nuclear NF-κB-binding activity in unstimulated CLL B cells relative to that detected in nonmalignant human B cells. In each case examined, CD40 ligation further augmented NF-κB activity and prolonged CLL cell survival in vitro. The principle NF-κB proteins in stimulated CLL cells appear to be quite similar to those in nonmalignant human B cells and include p50, p65, and c-Rel. In a CD154-positive case, blocking CD154 engagement by mAb to CD154 resulted in inhibition of NF-κB activity in the CLL cells. The addition of anti-CD154 mAb resulted in accelerated CLL cell death to a similar degree as was observed in cells exposed to dexamethasone. These data indicate that CD40 engagement has a profound influence on NF-κB activity and survival in CLL B cells, and are consistent with a role for CD154-expressing T and B cells in CLL pathogenesis. The data support the development of novel therapies based on blocking the CD154-CD40 interaction in CLL.

The presence of JAK2V617F mutation in the liver endothelial cells of patients with Budd-Chiari syndrome.

Patients with myeloproliferative disorders are at a high risk of developing thrombotic events. Several investigators have hypothesized that endothelial cell (EC) abnormalities might contribute to this prothrombotic state. Budd-Chiari syndrome (BCS) and portal vein thrombosis have been reported to be associated with JAK2V617F-positive hematopoiesis. We explored whether JAK2V617F was present in ECs in the vessels of polycythemia vera (PV) patients with BCS using laser capture microdissection followed by nested polymerase chain reaction or reverse-transcribed polymerase chain reaction. The ECs of the 2 BCS patients with PV were homozygous for the JAK2V617F and were shown to express transcripts characteristic of ECs but not hematopoietic cells. ECs of the other BCS patient with PV and 2 patients with hepatoportal sclerosis without PV contained exclusively wild-type JAK2. The presence of JAK2V617F in both ECs and hematopoietic cells belonging to BCS patients with PV indicate that ECs in PV are involved by the malignant process and that in a subpopulation of the patients the disease might originate from a common cell of origin for hematopoietic and ECs.

Ruxolitinib: The First FDA Approved Therapy for the Treatment of Myelofibrosis

The BCR-ABL1–negative myeloproliferative neoplasms (e.g., essential thrombocythemia, polycythemia vera, and primary myelofibrosis) are a group of heterogeneous hematologic malignancies that involve a clonal proliferation of hematopoietic stem cells. Thrombosis, bleeding, and transformation to acute leukemia reduce the overall survival of patients with myelofibrosis, a disease typified by progressive splenomegaly and disease-related symptoms such as fatigue, pruritus, and bony pains. Hematopoietic stem cell transplant offers the only potential for cure in a minority of eligible patients, leaving a serious unmet need for improved therapies. Recent advances in our understanding of the pathogenetic mechanisms underlying these diseases have led to an explosion of clinical trials evaluating novel therapies. The discovery of an activating mutation in the Janus-activated kinase 2 (JAK2) gene provided a therapeutic target to downregulate this activated signaling pathway, which influences the phenotype of these diseases. Ruxolitinib (Jakafi; Incyte) is a small-molecule inhibitor of JAK1/2 that has proved to be effective at reducing splenomegaly and ameliorating symptoms in myeloproliferative neoplasms. Based on the results of 2 pivotal randomized phase III clinical trials, ruxolitinib has become the first therapeutic to be approved by the U.S. Food and Drug Administration for treatment of patients with myelofibrosis. Ruxolitinib offers a well-tolerated oral therapeutic option for patients with myelofibrosis with symptomatic splenomegaly and debilitating disease-related symptoms, but it does not seem to be effective at eliminating the underlying hematological malignancy. Clin Cancer Res; 18(11); 3008–14. ©2012 AACR.

A phase I study of panobinostat (LBH589) in patients with primary myelofibrosis (PMF) and post‐polycythaemia vera/essential thrombocythaemia myelofibrosis (post‐PV/ET MF)

Panobinostat (LBH589), a novel histone deacetylase inhibitor (HDACi), was evaluated in a phase I study of patients with primary myelofibrosis (PMF) and post‐essential thrombocythaemia/polycythaemia vera‐related myelofibrosis (Post‐ET/PV MF). Eighteen patients (PMF 56%; Post‐PV MF 28%; Post‐ET MF 17%) were treated in three cohorts at oral doses of (i) 20, (ii) 30, and (iii) 25 mg three times weekly consecutively. Reversible thrombocytopenia was the dose‐limiting toxicity. Five patients (two in Dose Cohort 1, one in Dose Cohort 2 and two in Dose Cohort 3) received six or more cycles and were evaluable for response assessment. After the sixth cycle, three of these five patients achieved clinical improvement (CI) with 100% reduction in palpable splenomegaly from baseline, and two patients experienced stable disease. Panobinostat therapy was also associated with improvement in the degree of anaemia in two of the five patients. Of the three patients who achieved CI after six cycles, one patient achieved a near complete remission after 15 cycles of treatment and another patient had resolution of marrow fibrosis after 16 cycles. We conclude that panobinostat is a well‐tolerated, clinically active treatment for MF patients, regardless of JAK2 V617F status, and most effective when given at low doses over long periods of time.

Experience with pegylated interferon α-2a in advanced myeloproliferative neoplasms in an international cohort of 118 patients

The Philadelphia negative myeloproliferative neoplasms, including polycythemia vera, essential thrombocythemia, and myelofibrosis, are associated with substantial vascular and transformative complications. Standard therapy for high-risk disease, particularly in patients that have failed initial therapy, remains controversial. Non-pegylated interferon has previously been shown to be effective in controlling erythrocytosis, thrombocytosis and thrombotic complications, but was found to have poor tolerability and excessive adverse effects. Recently, pegylated interferon alpha-2a was introduced and found to be better tolerated and less toxic than standard interferon. In addition, in recent phase II trials, pegylated interferon alpha-2a therapy was found to induce both hematologic and molecular remissions. We retrospectively analyzed 118 myeloproliferative patients who underwent pegylated interferon alpha-2a treatment. Responses were evaluated by ELN, IWG-MET and EUMNET standardized criteria sets and adverse effects were analyzed.

The Effect of CXCL12 Processing on CD34+ Cell Migration in Myeloproliferative Neoplasms

Primary myelofibrosis (PMF) and polycythemia vera (PV) are chronic myeloproliferative neoplasms. PMF and, to a lesser degree, PV are characterized by constitutive mobilization of hematopoietic stem cells (HSC) and progenitor cells (HPC) into the peripheral blood (PB). The interaction between the chemokine CXCL12 and its receptor CXCR4 plays a pivotal role in determining the trafficking of CD34(+) cells between the bone marrow (BM) and the PB. PMF, but not PV, is associated with downregulation of CXCR4 by CD34(+) cells due to epigenetic events. Both PV and PMF patients have elevated levels of immunoreactive forms of CXCL12 in the BM and PB. Using electrospray mass spectrometry, the PB and BM plasma of PV and PMF patients was shown to contain reduced amounts of intact CXCL12 but significant amounts of several truncated forms of CXCL12, which are lacking in normal PB and BM plasma. These truncated forms of CXCL12 are the product of the action of several serine proteases, including dipeptidyl peptidase-IV, neutrophil elastase, matrix metalloproteinase-2 (MMP-2), MMP-9, and cathepsin G. Unlike CXCL12, these truncates either lack the ability to act as a chemoattractant for CD34(+) cells and/or act as an antagonist to the action of CXCL12. These data suggest that proteolytic degradation of CXCL12 is characteristic of both PV and PMF and that the resulting truncated forms of CXCL12, in addition to the reduced expression of CXCR4 by CD34(+) cells, lead to a profound mobilization of HSC/HPC in PMF.

MPD-RC 101 prospective study of reduced-intensity allogeneic hematopoietic stem cell transplantation in patients with myelofibrosis

From 2007 to 2011, 66 patients with primary myelofibrosis or myelofibrosis (MF) preceded by essential thrombocythemia or polycythemia vera were enrolled into a prospective phase 2 clinical trial of reduced-intensity allogeneic hematopoietic stem cell transplantation (AHSCT), Myeloproliferative Disorder Research Consortium 101 trial. The study included patients with sibling donors (n = 32) receiving fludarabine/melphalan (FluMel) as a preparative regimen and patients with unrelated donors (n = 34) receiving conditioning with FluMel plus anti-thymocyte globulin (ATG). Patient characteristics in the 2 cohorts were similar. Engraftment occurred in 97% of siblings and 76% of unrelated transplants, whereas secondary graft failure occurred in 3% and 12%, respectively. With a median follow-up of 25 months for patients alive, the overall survival (OS) was 75% in the sibling group (median not reached) and 32% in the unrelated group (median OS: 6 months, 95% confidence interval [CI]: 3, 25) (hazard ratio 3.9, 95% CI: 1.8,8.9) (P < .001). Nonrelapse mortality was 22% in sibling and 59% in unrelated AHSCT. Survival correlated with type of donor, but not with the degree of histocompatibility match, age, or JAK2(V617F) status. In patients with MF with sibling donors, AHSCT is an effective therapy, whereas AHSCT from unrelated donors with FluMel/ATG conditioning led to a high rate of graft failure and limited survival. This trial was registered at www.clinicaltrials.gov as #NCT00572897.

A comprehensive review and analysis of the effect of ruxolitinib therapy on the survival of patients with myelofibrosis

Myelofibrosis is a hematological malignancy with a median survival of approximately 5 to 7 years. Allogeneic stem cell transplantation is the only therapeutic modality that provides a cure for myelofibrosis patients. Recently, ruxolitinib has been shown in 2 phase 3 studies to be effective in reducing splenomegaly and improving symptoms in myelofibrosis patients. Although conventional markers of disease burden (marrow histopathological features, cytogenetic and molecular markers, and reversal of cytopenias) were not uniformly improved, a survival advantage in favor of ruxolitinib therapy was demonstrated. The use of historical control cohorts to compare survival was implemented in 2 different analyses of patients enrolled in the phase 1/2 studies and has further added fuel to the controversy surrounding the significance of this survival advantage. Ruxolitinib therapy results in a dramatic reduction in circulating proinflammatory cytokine levels, which has been associated with improvement in symptoms and performance status and may provide a link to improved survival. We analyze the various data published and place in perspective the significance of the prolongation of survival associated with ruxolitinib therapy. This critical review of these data may allow physicians to more rationally assess the benefits that can be anticipated with the appropriate use of this therapy.

Proliferative response of mantle cell lymphoma cells stimulated by CD40 ligation and IL-4

Mantle cell lymphoma (MCL) is a tumor of intermediate-size, IgM+, IgD+ B cells derived from the mantle zone of the germinal center. Little is known about its specific immunologic features or responsiveness to T cell-derived signals. In this work, we evaluated the proliferation and cell cycle properties of freshly isolated MCL cells after CD40 ligation, in the absence and presence of interleukin 4 (IL-4). In each MCL case examined, there was a marked growth-enhancing effect of these two stimuli characterized by improved viability, augmented expression of Ki-67, and induction of the proliferating cell nuclear antigen (PCNA). Cyclin D1 was expressed throughout the cell cycle in MCL cells induced to enter S phase. From these investigations, we conclude that the biology of MCL B lymphocytes is affected by CD154 (CD40 ligand) and IL-4, two signals usually provided by CD4+ T cells. The capacity to manipulate the activation and cell cycle state of MCL cells by these specific immunological stimuli may be exploited to confer susceptibility to chemotherapy agents and develop novel therapies in this disease.

Therapeutic options for patients with myelofibrosis in blast phase

Myelofibrosis (MF) is a clonal stem cell disorder with the potential to transform to acute leukemia, referred to as myelofibrosis in blast phase (MF-BP). The outcome of patients with MF-BP is grave with a median survival of only 2.7 months. MF-BP is largely refractory to conventional chemotherapy and intensive induction therapy fails to have a significant impact with a median survival of 3.9 months. Eleven consecutive patients were treated at our institution with MF-BP over a 2-year period. Eligible patients with an available donor received an allogeneic stem cell transplant (ASCT) and those that were not eligible or without a donor were treated with Decitabine (DEC). The median time for follow up for the entire group was 9 months (range 5-21 month). At 9 months (range 5-45 months), 67% of the patients treated with DEC were alive and at 20 months (range 9-23 months), 53% of patients treated with ASCT remain alive. Reduced intensity conditioning allogeneic stem cell transplantation (RIC-ASCT) is a viable option that offers the potential for prolonged survival and the possibility of cure for patients with MF-BP. DEC is a tolerable outpatient chemotherapeutic regimen for MF-BP patients ineligible for transplant and deserves further prospective study.