A randomized phase 3 trial of interferon-α vs hydroxyurea in polycythemia vera and essential thrombocythemia.

The goal of therapy for patients with essential thrombocythemia (ET) and polycythemia vera (PV) is to reduce thrombotic events by normalizing blood counts. Hydroxyurea (HU) and interferon-α (IFN-α) are the most frequently used cytoreductive options for patients with ET and PV at high risk for vascular complications. Myeloproliferative Disorders Research Consortium 112 was an investigator-initiated, phase 3 trial comparing HU to pegylated IFN-α (PEG) in treatment-naïve, high-risk patients with ET/PV. The primary endpoint was complete response (CR) rate at 12 months. A total of 168 patients were treated for a median of 81.0 weeks. CR for HU was 37% and 35% for PEG (P = .80) at 12 months. At 24 to 36 months, CR was 20% to 17% for HU and 29% to 33% for PEG. PEG led to a greater reduction in JAK2V617F at 24 months, but histopathologic responses were more frequent with HU. Thrombotic events and disease progression were infrequent in both arms, whereas grade 3/4 adverse events were more frequent with PEG (46% vs 28%). At 12 months of treatment, there was no significant difference in CR rates between HU and PEG. This study indicates that PEG and HU are both effective treatments for PV and ET. With longer treatment, PEG was more effective in normalizing blood counts and reducing driver mutation burden, whereas HU produced more histopathologic responses. Despite these differences, both agents did not differ in limiting thrombotic events and disease progression in high-risk patients with ET/PV. This trial was registered at www.clinicaltrials.gov as #NCT01259856.

Conventional Cytogenetic Analysis and Array CGH + SNP Identify Essential Thrombocythemia and Prefibrotic Primary Myelofibrosis Patients Who Are at Risk for Disease Progression.

The Philadelphia chromosome-negative myeloproliferative neoplasms (Ph-MPNs) are a heterogeneous group of clonal hematopoietic malignancies that include polycythemia vera (PV), essential thrombocythemia (ET), and the prefibrotic form of primary myelofibrosis (prePMF). In this study, we retrospectively reviewed the karyotypes from conventional cytogenetics (CC) and array Comparative Genomic Hybridization + Single Nucleotide Polymorphism (aCGH + SNP) in patients with ET or prePMF to determine whether the combined analysis of both methodologies can identify patients who may be at a higher risk of disease progression. We performed a comprehensive genomic review on 169 patients with a clinical diagnosis of ET (154 patients) or prePMF (15 patients). Genomic alterations detected by CC or array-CGH + SNP were detected in 36% of patients. In patients who progressed, 68% had an abnormal genomic finding by either technology. There was a shorter progression-free survival (PFS) among patients who were cytogenetically abnormal or who were cytogenetically normal but had an abnormal aCGH + SNP result. Leveraging the ability to detect submicroscopic copy number alterations and regions of copy neutral-loss of heterozygosity, we identified a higher number of patients harboring genomic abnormalities than previously reported. These results underscore the importance of genomic analysis in prognostication and provide valuable information for clinical management and treatment decisions.

Multipotent fetal-derived Cdx2 cells from placenta regenerate the heart.

The extremely limited regenerative potential of adult mammalian hearts has prompted the need for novel cell-based therapies that can restore contractile function in heart disease. We have previously shown the regenerative potential of mixed fetal cells that were naturally found migrating to the injured maternal heart. Exploiting this intrinsic mechanism led to the current hypothesis that Caudal-type homeobox-2 (Cdx2) cells in placenta may represent a novel cell type for cardiac regeneration. Using a lineage-tracing strategy, we specifically labeled fetal-derived Cdx2 cells with enhanced green fluorescent protein (eGFP). Cdx2-eGFP cells from end-gestation placenta were assayed for cardiac differentiation in vitro and in vivo using a mouse model of myocardial infarction. We observed that these cells differentiated into spontaneously beating cardiomyocytes (CMs) and vascular cells in vitro, indicating multipotentiality. When administered via tail vein to infarcted wild-type male mice, they selectively and robustly homed to the heart and differentiated to CMs and blood vessels, resulting in significant improvement in contractility as noted by MRI. Proteomics and immune transcriptomics studies of Cdx2-eGFP cells compared with embryonic stem (ES) cells reveal that they appear to retain "stem"-related functions of ES cells but exhibit unique signatures supporting roles in homing and survival, with an ability to evade immune surveillance, which is critical for cell-based therapy. Cdx2-eGFP cells may potentially represent a therapeutic advance in allogeneic cell therapy for cardiac repair.

Oral idasanutlin in patients with polycythemia vera.

A limited number of drugs are available to treat patients with polycythemia vera (PV) and essential thrombocythemia (ET). We attempted to identify alternative agents that may target abnormalities within malignant hematopoietic stem (HSCs) and progenitor cells (HPCs). Previously, MDM2 protein levels were shown to be upregulated in PV/ET CD34+ cells, and exposure to a nutlin, an MDM2 antagonist, induced activation of the TP53 pathway and selective depletion of PV HPCs/HSCs. This anticlonal activity was mediated by upregulation of p53 and potentiated by the addition of interferon-α2a (IFN-α2a). Therefore, we performed an investigator-initiated phase 1 trial of the oral MDM2 antagonist idasanutlin (RG7388; Roche) in patients with high-risk PV/ET for whom at least 1 prior therapy had failed. Patients not attaining at least a partial response by European LeukemiaNet criteria after 6 cycles were then allowed to receive combination therapy with low-dose pegylated IFN-α2a. Thirteen patients with JAK2 V617F+ PV/ET were enrolled, and 12 (PV, n = 11; ET, n = 1) were treated with idasanutlin at 100 and 150 mg daily, respectively, for 5 consecutive days of a 28-day cycle. Idasanutlin was well tolerated; no dose-limiting toxicity was observed, but low-grade gastrointestinal toxicity was common. Overall response rate after 6 cycles was 58% (7 of 12) with idasanutlin monotherapy and 50% (2 of 4) with combination therapy. Median duration of response was 16.8 months (range, 3.5-26.7). Hematologic, symptomatic, pathologic, and molecular responses were observed. These data indicate that idasanutlin is a promising novel agent for PV; it is currently being evaluated in a global phase 2 trial. This trial was registered at www.clinicaltrials.gov as #NCT02407080.

Pegylated interferon alfa-2a for polycythemia vera or essential thrombocythemia resistant or intolerant to hydroxyurea.

Prior studies have reported high response rates with recombinant interferon-α (rIFN-α) therapy in patients with essential thrombocythemia (ET) and polycythemia vera (PV). To further define the role of rIFN-α, we investigated the outcomes of pegylated-rIFN-α2a (PEG) therapy in ET and PV patients previously treated with hydroxyurea (HU). The Myeloproliferative Disorders Research Consortium (MPD-RC)-111 study was an investigator-initiated, international, multicenter, phase 2 trial evaluating the ability of PEG therapy to induce complete (CR) and partial (PR) hematologic responses in patients with high-risk ET or PV who were either refractory or intolerant to HU. The study included 65 patients with ET and 50 patients with PV. The overall response rates (ORRs; CR/PR) at 12 months were 69.2% (43.1% and 26.2%) in ET patients and 60% (22% and 38%) in PV patients. CR rates were higher in CALR-mutated ET patients (56.5% vs 28.0%; P = .01), compared with those in subjects lacking a CALR mutation. The median absolute reduction in JAK2V617F variant allele fraction was -6% (range, -84% to 47%) in patients achieving a CR vs +4% (range, -18% to 56%) in patients with PR or nonresponse (NR). Therapy was associated with a significant rate of adverse events (AEs); most were manageable, and PEG discontinuation related to AEs occurred in only 13.9% of subjects. We conclude that PEG is an effective therapy for patients with ET or PV who were previously refractory and/or intolerant of HU. This trial was registered at www.clinicaltrials.gov as #NCT01259856.

Clinical Benefit Derived from Decitabine Therapy for Advanced Phases of Myeloproliferative Neoplasms.

Treatment options are limited for patients with advanced forms of myeloproliferative neoplasms (MPN) including blast-phase disease (MPN-BP). Decitabine has frequently been deployed but its efficacy and safety profile are not well described in this population. We retrospectively reviewed 42 patients treated with decitabine either alone or in combination with ruxolitinib at our institution: 16 with MPN-BP, 14 with MPN accelerated-phase (MPN-AP), and 12 with myelofibrosis with high-risk features (MF-HR). The median overall survival (OS) for the MPN-BP patients was 2.6 months, and for those who received ≥2 cycles of decitabine therapy, it was 6.7 months (3.8-29.8). MPN-BP patients with a poor performance status and who required hospitalization at the time of the initiation of decitabine had a dismal prognosis. After a median follow-up of 12.4 months for MPN-AP patients, and 38.7 months for MF-HR patients, the median OS was not reached for either cohort, with 1 and 2 patients alive at 60 months, respectively. The probability of spleen length reduction and transfusion independence within 12 months of initiating decitabine was 28.6 and 23.5%, respectively. The combination of decitabine and ruxolitinib appeared to improve overall survival versus single-agent decitabine (21 and 12.9 months, respectively). Decitabine, alone or in combination with ruxolitinib, appears to have clinical benefit for patients with advanced phases of MPN when initiated early in the disease course prior to the development of MPN-BP.

Comparing the epidemiology, clinical characteristics and prognostic factors of acute myeloid leukemia with and without acute promyelocytic leukemia.

Acute promyelocytic leukemia (APL) is a particularly aggressive subtype of acute myeloid leukemia (AML), with high rates of early death. It is important to examine how epidemiological characteristics, clinical and treatment factors, cytogenetic and genetic data affect survival and differ between APL and non-APL AML patients. We analyzed population data from the New York State Cancer Registry to characterize AML including APL incidence rates by demographics. APL incidence rates were higher among Hispanics than non-Hispanics [incidence rate ratio = 1.22; 95% confidence interval (CI) = 1.02-1.43]; and among foreign-born than USA-born persons. APL incidence rates increased more rapidly through 1995-2014 than non-APL AML; and its frequency increased faster among foreign-born persons. In a hospital cohort of 390 AML patients, the risk of death was significantly higher among APL patients with FLT3-internal tandem duplications than those without [hazard ratio (HR) = 11.74; 95% CI = 1.03-134.5]; and among APL patients with secondary versus de novo disease (HR = 17.32; 95% CI = 1.56-192.1). Among non-APL AML patients, risk of death was significantly associated with prior chemotherapy with antitubulin agents after adjusting for age, gender and ethnicity (adjusted HR = 3.30; 95% CI = 1.49-7.32); and separately with older age, unfavorable cytogenetics and complex karyotype. This study highlights FLT3-internal tandem duplications as a prognostic factor in APL and proposes consideration of prior antitubulin therapy as a prognostic factor in non-APL AML.

Impact of High-Molecular-Risk Mutations on Transplantation Outcomes in Patients with Myelofibrosis.

Mutational profiling has demonstrated utility in predicting the likelihood of disease progression in patients with myelofibrosis (MF). However, there is limited data regarding the prognostic utility of genetic profiling in MF patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HCT). We performed high-throughput sequencing of 585 genes on pre-transplant samples from 101 patients with MF who underwent allo-HCT and evaluated the association of mutations and clinical variables with transplantation outcomes. Overall survival (OS) at 5 years post-transplantation was 52%, and relapse-free survival (RFS) was 51.1 % for this cohort. Nonrelapse mortality (NRM) accounted for most deaths. Patient's age, donor's age, donor type, and Dynamic International Prognostic Scoring System score at diagnosis did not predict for outcomes. Mutations known to be associated with increased risk of disease progression, such as ASXL1, SRSF2, IDH1/2, EZH2, and TP53, did not impact OS or RFS. The presence of U2AF1 (P = .007) or DNMT3A (P = .034) mutations was associated with worse OS. A Mutation-Enhanced International Prognostic Scoring System 70 score was available for 80 patients (79%), and there were no differences in outcomes between patients with high risk scores and those with intermediate and low risk scores. Collectively, these data identify mutational predictors of outcome in MF patients undergoing allo-HCT. These genetic biomarkers in conjunction with clinical variables may have important utility in guiding transplantation decision making.

A Novel t(1;9)(p36;p24.1) JAK2 Translocation and Review of the Literature.

The JAK2V617F point mutation has been implicated in the pathogenesis of the vast majority of myeloproliferative neoplasms (MPNs), but translocations involving JAK2 have increasingly been identified in patients with JAK2V617F-negativeMPNs. Here, we present a case of a patient diagnosed with JAK2V617F-negativepolycythemia vera (PV) that transformed to the MPN-blast phase. Cytogenetic and FISH analysis revealed a novel translocation of t(1;9)(p36;p24.1), causing a PEX14-JAK2 gene fusion product. The t(1;9)(p36;p24.1) represents a new addition to the list of known translocations involving JAK2that have been identified in hematologic malignancies. Although the prognostic and treatment implications of JAK2 translocations in MPNs have not been elucidated, positive outcomes have been described in case reports describing the use of JAK inhibitors in these patients. Further research into the role of JAK2 translocations in the pathogenesis and outcomes of hematologic malignancies is warranted.

Outcome of Allogeneic Hematopoietic Stem Cell Transplantation for Patients with Chronic and Advanced Phase Myelofibrosis.

Myelofibrosis (MF) is a chronic progressive hematologic malignancy with a median overall survival (OS) of approximately 6 years. Allogeneic hematopoietic stem cell transplantation (HSCT) is the sole treatment approach that offers curative potential. The use of reduced-intensity conditioning regimens has expanded the application of HSCT to patients with MF up to age 70 years. Recent retrospective and prospective reports have suggested worse HSCT outcomes for patients with MF receiving an unrelated donor graft compared with those receiving a related donor graft. To identify patient- and HSCT-specific variables influencing outcomes, we conducted a retrospective analysis of 42 patients with chronic and advanced-phase MF who underwent HSCT at our institution. For this cohort, at a median follow-up of 43 months, progression-free survival (PFS) was 15 months and OS was 25 months. In multivariable analysis, the sole clinical variable that negatively influenced outcome was the use of an unrelated donor, with a median PFS and OS both of 11 months versus not yet reached in patients receiving a related donor graft. At 2 years, OS was 38% (95% confidence interval [CI], 20%-56%) and nonrelapse mortality (NRM) was 53% (95% CI, 36%-78%) in the unrelated donor graft group, compared with 75% (95% CI, 46%-90%) and 21% (95% CI, 9%-47%) in the related donor graft group. There was no difference in the rates of grade III-IV acute graft-versus-host disease between the unrelated and related donor groups (38% versus 38%). Despite a more aggressive disease state, 2-year PFS and OS were both 42% (95% CI, 15%-67%) in patients with myeloproliferative neoplasm-blast phase undergoing HSCT. Graft failure rate was higher in patients receiving a mismatched donor graft compared with those receiving a matched donor graft (60% versus 13%; P = .0398). Retransplantation of patients with graft failure resulted in long-term survival. Baseline splenomegaly did not affect transplantation outcomes. Given the particularly poor outcomes seen in the unrelated donor cohort here and elsewhere, a formal exploration of alternative hematopoietic stem cell sources is warranted.

JAK2 inhibitors do not affect stem cells present in the spleens of patients with myelofibrosis.

Dysregulation of Janus kinase (JAK)-signal transducer and activator of transcription signaling is central to the pathogenesis of myelofibrosis (MF). JAK2 inhibitor therapy in MF patients results in a rapid reduction of the degree of splenomegaly, yet the mechanism underlying this effect remains unknown. The in vitro treatment of splenic and peripheral blood MF CD34(+) cells with the JAK1/2/3 inhibitor, AZD1480, reduced the absolute number of CD34(+), CD34(+)CD90(+), and CD34(+)CXCR4(+) cells as well as assayable hematopoietic progenitor cells (HPCs) irrespective of the JAK2 and calreticulin mutational status. Furthermore, AZD1480 treatment resulted in only a modest reduction in the proportion of HPCs that were JAK2V617F(+) or had a chromosomal abnormality. To study the effect of the drug on MF stem cells (MF-SCs), splenic CD34(+) cells were treated with AZD1480 and transplanted into immunodeficient mice. JAK2 inhibitor therapy did not affect the degree of human cell chimerism or the proportion of malignant donor cells. These data indicate that JAK2 inhibitor treatment affects a subpopulation of MF-HPCs, while sparing another HPC subpopulation as well as MF-SCs. This pattern of activity might account for the reduction in spleen size observed with JAK2 inhibitor therapy as well as the rapid increase in spleen size observed frequently with its discontinuation.

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.

Cytogenetically normal acute myeloid leukemia with a novel KIT mutation in exon 11 G565V developing a sole trisomy 13 at relapse: a clinical dilemma.

We describe a patient with acute myeloid leukemia (AML) who had a normal karyotype at diagnosis and was negative for NPM1 and FLT3 mutations, but had a KIT G565V mutation in exon 11. This has not been described previously in AML. The patient received induction and consolidation chemotherapy and was in hematologic remission for 351 days when deletion 7q was cytogenetically detected in 8% of the bone marrow cells. After an initial treatment of azacitidine followed by decitabine, an unrelated trisomy 13 clone was identified, followed by subclonal rearrangement of ETV6. The patient underwent reinduction with high-dose cytarabine and mitoxantrone followed by voluntary-unrelated-donor allogeneic stem cell transplantation with a reduced-intensity conditioning. As of writing, the patient is in complete hematologic and cytogenetic remission with 100% donor cell engraftment.

Oncogene-mediated alterations in chromatin conformation.

Emerging evidence suggests that chromatin adopts a nonrandom 3D topology and that the organization of genes into structural hubs and domains affects their transcriptional status. How chromatin conformation changes in diseases such as cancer is poorly understood. Moreover, how oncogenic transcription factors, which bind to thousands of sites across the genome, influence gene regulation by globally altering the topology of chromatin requires further investigation. To address these questions, we performed unbiased high-resolution mapping of intra- and interchromosome interactions upon overexpression of ERG, an oncogenic transcription factor frequently overexpressed in prostate cancer as a result of a gene fusion. By integrating data from genome-wide chromosome conformation capture (Hi-C), ERG binding, and gene expression, we demonstrate that oncogenic transcription factor overexpression is associated with global, reproducible, and functionally coherent changes in chromatin organization. The results presented here have broader implications, as genomic alterations in other cancer types frequently give rise to aberrant transcription factor expression, e.g., EWS-FLI1, c-Myc, n-Myc, and PML-RARα.

Combination treatment in vitro with Nutlin, a small-molecule antagonist of MDM2, and pegylated interferon-α 2a specifically targets JAK2V617F-positive polycythemia vera cells.

Interferon (IFN-α) is effective therapy for polycythemia vera (PV) patients, but it is frequently interrupted because of adverse events. To permit the long-term use of IFN, we propose combining low doses of IFN with Nutlin-3, an antagonist of MDM2, which is also capable of promoting PV CD34(+) cell apoptosis. Combination treatment with subtherapeutic doses of Peg IFN-α 2a and Nutlin-3 inhibited PV CD34(+) cell proliferation by 50% while inhibiting normal CD34(+) cells by 30%. Combination treatment with Nutlin-3 and Peg IFN-α 2a inhibited PV colony formation by 55%-90% while inhibiting normal colony formation by 22%-30%. The combination of these agents also decreased the proportion of JAK2V617F-positive hematopoietic progenitor cells in 6 PV patients studied. Treatment with low doses of Peg IFN-α 2a combined with Nutlin-3 increased phospho-p53 and p21 protein levels in PV CD34(+) cells and increased the degree of apoptosis. These 2 reagents affect the tumor suppressor p53 through different pathways with Peg IFN-α 2a activating p38 MAP kinase and STAT1, leading to increased p53 transcription, whereas Nutlin-3 prevents the degradation of p53. These data suggest that treatment with low doses of both Nutlin-3 combined with Peg IFN-α 2a can target PV hematopoietic progenitor cells, eliminating the numbers of malignant hematopoietic progenitor cells.

Fetal cells traffic to injured maternal myocardium and undergo cardiac differentiation.

RATIONALE: Fetal cells enter the maternal circulation during pregnancy and may persist in maternal tissue for decades as microchimeras. OBJECTIVE: Based on clinical observations of peripartum cardiomyopathy patients and the high rate of recovery they experience from heart failure, our objective was to determine whether fetal cells can migrate to the maternal heart and differentiate to cardiac cells. METHODS AND RESULTS: We report that fetal cells selectively home to injured maternal hearts and undergo differentiation into diverse cardiac lineages. Using enhanced green fluorescent protein (eGFP)-tagged fetuses, we demonstrate engraftment of multipotent fetal cells in injury zones of maternal hearts. In vivo, eGFP+ fetal cells form endothelial cells, smooth muscle cells, and cardiomyocytes. In vitro, fetal cells isolated from maternal hearts recapitulate these differentiation pathways, additionally forming vascular tubes and beating cardiomyocytes in a fusion-independent manner; ≈40% of fetal cells in the maternal heart express Caudal-related homeobox2 (Cdx2), previously associated with trophoblast stem cells, thought to solely form placenta. CONCLUSIONS: Fetal maternal stem cell transfer appears to be a critical mechanism in the maternal response to cardiac injury. Furthermore, we have identified Cdx2 cells as a novel cell type for potential use in cardiovascular regenerative therapy.

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.

Down-regulation of stathmin expression is required for megakaryocyte maturation and platelet production.

The final stages of of megakaryocyte (MK) maturation involve a series of steps, including polyploidization and proplatelet formation. Although these processes are highly dependent on dynamic changes in the microtubule (MT) cytoskeleton, the mechanisms responsible for regulation of MTs in MKs remain poorly defined. Stathmin is a highly conserved MT-regulatory protein that has been suggested to play a role in MK differentiation of human leukemic cell lines. However, previous studies defining this relationship have reached contradictory conclusions. In this study, we addressed this controversy and investigated the role of stathmin in primary human MKs. To explore the importance of stathmin down-regulation during megakaryocytopoiesis, we used a lentiviral-mediated gene delivery system to prevent physiologic down-regulation of stathmin in primary MKs. We demonstrated that sustained expression of constitutively active stathmin delayed cytoplasmic maturation (ie, glycoprotein GPIb and platelet factor 4 expression) and reduced the ability of MKs to achieve high levels of ploidy. Moreover, platelet production was impaired in MKs in which down-regulation of stathmin expression was prevented. These studies indicate that suppression of stathmin is biologically important for MK maturation and platelet production and support the importance of MT regulation during the final stages of thrombopoiesis.

Chromothripsis in lipoblastoma: second reported case with complex PLAG1 rearrangement.

Lipoblastomas (LPBs) are rare benign neoplasms derived from embryonal adipose that occur predominantly in childhood. LPBs typically present with numeric or structural rearrangements of chromosome 8, the majority of which involve the pleomorphic adenoma gene 1 (PLAG1) proto-oncogene on chromosome 8q12. Here, we report on a LPB case on which showed evidence of chromothripsis. This is the second reported case of chromothripsis in LPB.