Brady L. Stein

Vitamin D Treatment for the Prevention of Falls in Older Adults: Systematic Review and Meta‐Analysis

OBJECTIVES: To systematically review and quantitatively synthesize the effect of vitamin D therapy on fall prevention in older adults.

Detection of a potent humoral response associated with immune-induced remission of chronic myelogenous leukemia

The effectiveness of donor-lymphocyte infusion (DLI) for treatment of relapsed chronic myelogenous leukemia (CML) after allogeneic bone marrow transplantation is a clear demonstration of the graft-versus-leukemia (GVL) effect. T cells are critical mediators of GVL, but the antigenic targets of this response are unknown. To determine whether patients who respond to DLI also develop B-cell immunity to CML-associated antigens, we analyzed sera from three patients with relapsed CML who achieved a complete molecular remission after infusion of donor T cells. Sera from these individuals recognized 13 distinct gene products represented in a CML-derived cDNA library. Two proteins, Jkappa-recombination signal-binding protein (RBP-Jkappa) and related adhesion focal tyrosine kinase (RAFTK), were recognized by sera from three of 19 DLI responders. None of these antigens were recognized by sera from healthy donors or patients with chronic graft-versus-host disease. Four gene products were recognized by sera from CML patients treated with hydroxyurea and nine were detected by sera from CML patients who responded to IFN-alpha. Antibody titers specific for RAFTK, but not for RBP-Jkappa, were found to be temporally associated with the response to DLI. These results demonstrate that patients who respond to DLI generate potent antibody responses to CML-associated antigens, suggesting the development of coordinated T- and B-cell immunity. The characterization of B cell-defined antigens may help identify clinically relevant targets of the GVL response in vivo.

Disruption of the ASXL1 gene is frequent in primary, post-essential thrombocytosis and post-polycythemia vera myelofibrosis, but not essential thrombocytosis or polycythemia vera: analysis of molecular genetics and clinical phenotypes.

Background The myeloproliferative neoplasms, essential thrombocytosis, polycythemia vera and primary myelofibrosis, share the same acquired genetic lesion, but the concept of JAK2 V617F serving as the sole lesion responsible for these neoplasms is under question, and there has been interest in identifying additional mutations that may contribute to disease pathogenesis. Because ASXL1 lesions have been increasingly identified in myeloid neoplasms, we examined the relationships of ASXL1 mutation or deletion to both clinical phenotype and associated molecular features in 166 patients with myeloproliferative neoplasms. Design and Methods Exon 12 of ASXL1 was amplified from neutrophil genomic DNA and bidirectionally sequenced in 77 patients with myelofibrosis (including patients with primary and post-essential thrombocytosis or post-polycythemia myelofibrosis), 42 patients with polycythemia vera, 41 with essential thrombocytosis and 6 with post-myelofibrosis acute myeloid leukemia. Pyrosequencing assays were designed to determine the allele percentages of JAK2 V617F (G5073770T), ASXL1 2475dupA, and ASXL1 2846_2847del in neutrophil genomic DNA samples. Clinical and laboratory characteristics of patients with wild-type and ASXL1 mutations were then compared. Results We identified nonsense mutations or hemizygous deletion of ASXL1 in 36% of the patients with myelofibrosis, but very rarely among those with polycythemia vera or essential thrombocytosis. Among the patients with myelofibrosis, those with ASXL1 lesions were not distinguished from their wild-type counterparts with regard to JAK2 V617F status, exposure to chemotherapy or evolution to leukemia. Myelofibrosis patients with ASXL1 lesions were more likely to have received anemia-directed therapy compared to those without lesions [15/26 (58%) versus 11/39 (23%); P=0.02]. Using serial banked samples and quantitative ASXL1 mutant allele burden assays, we observed the acquisition and accumulation of ASXL1 mutations over time in two patients with post-essential thrombocytosis myelofibrosis. Conclusions ASXL1 haploinsufficiency is associated with a myelofibrosis phenotype in the context of other known and unknown lesions, and disruption of ASXL1 function may contribute to the disease pathogenesis of myelofibrosis.

Sex differences in the JAK2V617F allele burden in chronic myeloproliferative disorders

Background The JAK2V617F allele burden is a variable measure, determined by the frequency of mitotic recombination events and the expansion of JAK2V617F clones. Since variability in the JAK2V617F allele burden is partly responsible for the distinct phenotypes seen in the myeloproliferative disorders, the objective of this study was to identify modifiers of the allele burden. Design and Methods Blood samples were obtained between May 2005 and January 2009 from 272 patients with essential thrombocytosis, polycythemia vera, and myelofibrosis. The JAK2V617F allele burden was measured by an allele-specific quantitative polymerase chain reaction using DNA from purified neutrophils. Repeated measures, on average 2 years apart, were available for 104 patients. Results Sex, age at diagnosis, and disease duration all independently influenced the JAK2V617F allele burden. When considering all patients with myeloproliferative disorders, women had significantly lower allele burdens than men (P=0.04). In those patients with repeated measures, the increase in allele burden per year between the first and second evaluations was significantly less in females than in males. Among those who experienced disease evolution, females were 4.5 times more likely to have evolution from essential thrombocytosis to polycythemia vera, but 0.23 times as likely to have evolution from essential thrombocytosis to myelofibrosis. Conclusions Sex is an independent factor accounting for variability in the JAK2V617F allele burden. We speculate that lower allele burdens in females reflect a lower frequency of mitotic recombination events in females than in males, and should be considered when evaluating the relationship of allele burden to disease phenotype and also in evaluating responses to JAK2V617F-inhibitors. Because sex may influence genotype and/or clonal expansion, underpinning the variability in JAK2V617F allele burden, it will be important to explore factors that determine susceptibility to mitotic recombination events.

Sex differences in the JAK2V617F allele burden in the chronic myeloproliferative disorders

Background The JAK2V617F allele burden is a variable measure, determined by the frequency of mitotic recombination events and the expansion of JAK2V617F clones. Since variability in the JAK2V617F allele burden is partly responsible for the distinct phenotypes seen in the myeloproliferative disorders, the objective of this study was to identify modifiers of the allele burden. Design and Methods Blood samples were obtained between May 2005 and January 2009 from 272 patients with essential thrombocytosis, polycythemia vera, and myelofibrosis. The JAK2V617F allele burden was measured by an allele-specific quantitative polymerase chain reaction using DNA from purified neutrophils. Repeated measures, on average 2 years apart, were available for 104 patients. Results Sex, age at diagnosis, and disease duration all independently influenced the JAK2V617F allele burden. When considering all patients with myeloproliferative disorders, women had significantly lower allele burdens than men (P=0.04). In those patients with repeated measures, the increase in allele burden per year between the first and second evaluations was significantly less in females than in males. Among those who experienced disease evolution, females were 4.5 times more likely to have evolution from essential thrombocytosis to polycythemia vera, but 0.23 times as likely to have evolution from essential thrombocytosis to myelofibrosis. Conclusions Sex is an independent factor accounting for variability in the JAK2V617F allele burden. We speculate that lower allele burdens in females reflect a lower frequency of mitotic recombination events in females than in males, and should be considered when evaluating the relationship of allele burden to disease phenotype and also in evaluating responses to JAK2V617F-inhibitors. Because sex may influence genotype and/or clonal expansion, underpinning the variability in JAK2V617F allele burden, it will be important to explore factors that determine susceptibility to mitotic recombination events.

AKT is a therapeutic target in myeloproliferative neoplasms

The majority of patients with BCR-ABL1-negative myeloproliferative neoplasms (MPN) harbor mutations in JAK2 or MPL, which lead to constitutive activation of the JAK/STAT, PI3K and ERK signaling pathways. JAK inhibitors by themselves are inadequate in producing selective clonal suppression in MPN and are associated with hematopoietic toxicities. MK-2206 is a potent allosteric AKT inhibitor that was well tolerated, including no evidence of myelosuppression, in a phase I study of solid tumors. Herein, we show that inhibition of PI3K/AKT signaling by MK-2206 affected the growth of both JAK2V617F- or MPLW515L-expressing cells via reduced phosphorylation of AKT and inhibition of its downstream signaling molecules. Moreover, we demonstrate that MK-2206 synergizes with ruxolitinib in suppressing the growth of JAK2V617F-mutant SET2 cells. Importantly, MK-2206 suppressed colony formation from hematopoietic progenitor cells in patients with primary myelofibrosis and alleviated hepatosplenomegaly and reduced megakaryocyte burden in the bone marrows, livers and spleens of mice with MPLW515L-induced MPN. Together, these findings establish AKT as a rational therapeutic target in the MPNs.

Disease burden at the progenitor level is a feature of primary myelofibrosis: a multivariable analysis of 164 JAK2 V617F-positive myeloproliferative neoplasm patients

OBJECTIVE Suppression of normal hematopoiesis by the neoplastic clone (clonal dominance) is a feature of the myeloproliferative neoplasms, but the determinants that predict clonal dominance are unknown. The objective of this study was to identify clinical and laboratory variables that associate with the JAK2 V617F CD34(+) progenitor allele burden and clonal dominance, which was defined by congruence of the JAK2 V617F CD34(+) progenitor and neutrophil allele burdens. MATERIALS AND METHODS A cross-sectional analysis was performed on 164 consecutive JAK2 V617F-positive patients: 30 with essential thrombocytosis (ET), 100 with polycythemia vera (PV), and 34 with myelofibrosis (MF), including 8 post-ET MF and 3 post-PV MF. The JAK2 V617F CD34(+) progenitor and neutrophil allele burdens were measured using an allele-specific, quantitative real-time polymerase chain reaction assay. RESULTS After adjusting for genotype, sex, age at diagnosis, and disease duration, disease type was the strongest predictor of clonal dominance, with the odds ratio being nearly 61.9 times higher for MF patients when compared with ET patients (p < 0.001), and 9.7 times higher when compared with PV patients (p = 0.002). Additionally, clonal dominance was associated with a clinical phenotype of an increased spleen size (p = 0.006), increased white blood cell count (p = 0.009), and lower hemoglobin (p < 0.001), even after adjusting for disease type and duration. CONCLUSIONS These data indicate that loss of wild-type clones at the progenitor level is a feature of MF (primary MF, post-ET MF, and post-PV MF), presumably due to expansion of the JAK2 V617F clone and that this characteristic is surprisingly independent of JAK2 V617F homozygosity, suggesting that additional genomic lesions may contribute to this unique molecular process that distinguishes MF from ET and PV.

Age-related differences in disease characteristics and clinical outcomes in polycythemia vera

Abstract The natural history and prognosis for young patients with polycythemia vera (PV) in the post-JAK2 V617F era are not well defined. Therefore, we retrospectively analyzed disease characteristics and clinical outcomes in 120 patients ≤ 45 years and 84 patients ≥ 65 years at diagnosis. Despite lower white blood counts (9.2 vs. 13.4 × 109/L, p = 0.004) and a lower JAK2 V617F allele burden (51% vs. 66%, p = 0.015), younger patients with PV had comparable rates of vascular complications compared to older patients (27% vs. 31%, p = 0.64). However, splanchnic vein thrombosis occurred more frequently in younger patients (13% vs. 2%, p = 0.0056). Myelofibrotic and leukemic transformation, the most serious complications of myeloproliferative neoplasms (MPN), occurred with similar frequencies in young versus older patients (15% vs. 10%, p = 0.29). Prevention or delay of these complications is currently the most urgent challenge in the care of younger patients with PV.

Janus kinase inhibitors: an update on the progress and promise of targeted therapy in the myeloproliferative neoplasms.

Purpose of review The discovery of the JAK2 V617F mutation in the classical myeloproliferative neoplasms (MPNs) essential thrombocytosis, polycythemia vera, and primary myelofibrosis has ushered in a new era of scientific discovery in these diseases, resulting in a molecular classification and an improved understanding of disease pathogenesis. Alongside this period of discovery has been the rapid development of targeted therapy and, here, we summarize results from clinical trials involving these small molecule Janus family of tyrosine kinase (JAK) inhibitors. Recent findings The JAK inhibitors consistently alleviate constitutional symptoms and reduce spleen size. Early phase testing indicates that some of these inhibitors have additional unique effects: INCB018424 results in a significant reduction in the level of pro-inflammatory cytokines; TG101348 may modify disease burden as assessed by JAK2 allele measurements; and CYT387 ameliorates anemia. Summary The initial enthusiasm for these agents has been tempered by recognition that JAK2 V617F may represent only one component of lesions driving the heterogeneity of the MPN. Clinical trial design cannot address important disease endpoints such as thrombosis or leukemia transformation, but it appears that JAK inhibitors will offer an important palliative option and because of the molecular complexity in these diseases, it might be rational to give these inhibitors along with other agents that target alternate mechanisms of the disease pathogenesis.

Treatment options for patients with chronic myeloid leukemia who are resistant to or unable to tolerate imatinib

BACKGROUND Imatinib has been found to substantially improve outcomes in patients with chronic myeloid leukemia (CML) compared with previously available therapies. However, its use is complicated by development of resistance or drug intolerance, prompting dose escalation or a trial of dasatinib or nilotinib, the second-generation tyrosine kinase inhibitors (TKIs). OBJECTIVES This article reviews the mechanisms of TKI resistance; discusses the tolerability and efficacy of high-dose imatinib, dasatinib, and nilotinib; and provides background for the rational use of second-line treatment options. METHODS MEDLINE (1966-December 2009) and EMBASE (1993-December 2009) were searched for pertinent English-language publications using search terms that included, but were not limited to, chronic myeloid leukemia, imatinib, dasatinib, nilotinib, and clinical trial. Abstracts from American Society of Hematology annual meetings (2005-2009) were also reviewed. There were no prespecified inclusion or exclusion criteria. RESULTS Major and complete cytogenetic responses (MCyR and CCyR, respectively) to second-line treatment with high-dose (600-800 mg/d PO) imatinib were restricted to CML patients who had achieved a CyR to standard-dose imatinib: >90% of patients without a previous CyR failed to respond. The expected durability of the response to this approach remains unclear. Grade 3/4 thrombocytopenia, neutropenia, and anemia occurred in 14%, 39%, and 8%, respectively, of patients receiving high-dose imatinib. In patients who failed first-line treatment with imatinib, dasatinib (70 mg BID PO) was associated with higher rates of CCyR at 2 years compared with imatinib (44% vs 18%, respectively; P = 0.003), as well as higher estimated rates of progression-free survival at 2 years (86% vs 65%; P = 0.001). Dasatinib use was complicated by grade 3/4 thrombocytopenia and neutropenia in 57% and 63% of patients, respectively, and pleural effusion in 5%. Nilotinib treatment was effective in patients who were resistant to or unable to tolerate imatinib, with 46% and 58% achieving a CCyR and MCyR, respectively, at 2 years. Nilotinib use was complicated by grade 3/4 thrombocytopenia and neutropenia in 28% and 40% of patients, respectively, and QTc-interval prolongation in 1% to 10% of patients. Neither agent was clinically effective in patients with the common T315I mutation. CONCLUSION Dasatinib and nilotinib were effective and generally well tolerated as second-line treatments for CML patients with a suboptimal response to standard doses of imatinib or imatinib intolerance.