Bruce Petersen

Deletion of Tet2 in mice leads to dysregulated hematopoietic stem cells and subsequent development of myeloid malignancies

TET2 is mutated/deleted with high frequencies in multiple forms of myeloid malignancies including MDS, CMML, MPN, and AML. However, little is known regarding the biological function of TET2 and its role in the pathogenesis of myeloid malignancies. To study the function of TET2 in vivo, we generated a Tet2 knock out mouse model. Deletion of Tet2 in mice led to dramatic reduction in the 5-hydroxymethylcytosine levels and concomitant increase in the 5-methylcytosine levels in the genomic DNA of BM cells. The Tet2(-/-) mice contained an increased Lin(-)Sca-1(+)c-Kit(+) (LSK) cell pool before the development of myeloid malignancies. A competitive reconstitution assay revealed that Tet2(-/-) LSK cells had an increased hematopoietic repopulating capacity with an altered cell differentiation skewing toward monocytic/granulocytic lineages. Approximately 1/3 of Tet2(-/-) and 8% of Tet2(+/-) mice died within 1 year of age because of the development of myeloid malignancies resembling characteristics of CMML, MPD-like myeloid leukemia, and MDS. Furthermore, transplantation of Tet2(-/-), but not wild-type (WT) or Tet2(+/-) BM cells, led to increased WBC counts, monocytosis, and splenomegaly in WT recipient mice. These data indicate that Tet2-deficient mice recapitulate patients with myeloid malignancies, implying that Tet2 functions as a tumor suppressor to maintain hematopoietic cell homeostasis.

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.

Anti-transforming growth factor-β therapy in patients with myelofibrosis

Bone marrow fi brosis (BMF), in the myeloproliferative neoplasm (MPN) myelofi brosis (MF), is the result of a complex and yet not fully understood interaction between megakaryocytes, monocytes, fi broblasts, endothelial cells, cytokines and marrow stroma [1]. Th ere are substantial data to support the clonal nature of MPNs from primitive progenitor hematopoietic cells which then secrete factors that activate polyclonal fi broblasts in the bone marrow [2]. BMF is not an irreversible process, and morphologic evidence of reversal can be achieved after hematopoietic stem cell transplant and occasionally drug therapy [3 – 5]. Transforming growth factorβ (TGFβ ) is a pleiotropic cytokine implicated in the promotion of angiogenesis, tumor growth, collagen fi brosis, metastatic spread and down-regulation of antitumor immunity, and paradoxically, tumor-suppressive eff ects [6]. TGFβ likely plays a dual role in promoting myelofi brosis and myeloproliferation, both of which are the morphologic hallmarks of MF [2]. Degree of BMF can be correlated with a variety of clinical features such as anemia, thrombocytopenia, leukopenia, splenomegaly and peripheral blood blasts, and can be predictive of survival in patients with MF [7,8]. Preclinical studies support a pathobiological role of TGFβ in MF [9 – 11]. Th e development of BMF in GATA-1 low and TPO high murine models of MF is associated with high levels of TGFβ expression in extracellular fl uids and spaces within the bone marrow and spleen [10]. A working hypothesis linking abnormal megakaryocyte/neutrophil interaction with enhanced TGFβ expression in MF has been developed based on these observations [11]. Para-apoptosis leading to the release of TGFβ from megakaryocyte alpha-granules may be the result of impaired neutrophil emperipolesis due to abnormal P-selectin localization on the demarcation membrane of MF megakaryocytes [10]. Additionally, TGFβ mRNA levels are signifi cantly elevated in megakaryocytes of patients with MF and correlate with the degree of BMF [9]. We hypothesized that inhibiting the TGFβ signaling pathway in MF would decrease the fi brogenic stimuli leading to BMF and concomitantly interrupt myeloproliferation. GC1008 is a human immunoglobulin G4 (IgG4) kappa monoclonal antibody capable of neutralizing each of the mammalian isoforms of TGFβ (i.e. β 1, β 2 and β 3). Animal toxicology studies of TGFβ antibodies in normal rodents and primates have shown that administration of inhibitory antibodies to TGFβ is well tolerated, and a phase 1 clinical trial of GC1008 in advanced melanoma and renal cell carcinoma has also proven to be well tolerated in humans [12]. A total of 29 patients were enrolled in this study, and doses up to 15 mg/kg were found to be safe without the development of dose limiting toxicities (DLTs). Th e most frequently reported drug-related adverse events (AEs) were gingival bleeding and fatigue, and the most serious AEs were skin rashes (including keratocanthomas and squamous cell carcinoma) that were noted in sun-exposed areas of patients with melanoma only. Based on an existing preclinical rationale, we conducted an investigator-initiated, single institution, open label, phase 1, dose escalation study investigating the tolerability and safety of GC1008 (Fresolimumab; Genzyme) in patients with intermediate-1 or higher primary myelofi brosis (PMF) or post-polycythemia vera/essential thrombocythemia myelofi brosis (post-PV/ET MF) [13]. Th is trial was registered at www.ClinicalTrials.gov (NCT01291784), approved by the Mount Sinai School of Medicine Program for the Protection for Human Subjects (PPHS), and informed written consent was obtained in accordance with the Declaration of Helsinki. Patients were eligible if they had documented BMF of MF-2 or higher as assessed by the European consensus grading score and grade 3 or higher by modifi ed Bauermeister scale [14 – 16]. Th e primary objective of this study was to determine the safety and tolerability of GC1008 treatment in patients with MF. Secondary objectives included treatment response assessment by International Working Group for Myelofi brosis Research and Treatment (IWG-MRT) criteria; assessment of degree of change in BMF grade measured by the modifi ed Bauermeister scale and European consensus grading system after six and 12 cycles; evaluation of exploratory markers for their potential to predict treatment response; and assessment of symptom response using the Myeloproliferative L eu k L ym ph om a D ow nl oa de d fr om in fo rm ah ea lth ca re .c om b y N yu M ed ic al C en te r on 0 7/ 24 /1 5

Proposed criteria for response assessment in patients treated in clinical trials for myeloproliferative neoplasms in blast phase (MPN-BP): Formal recommendations from the post-myeloproliferative neoplasm acute myeloid leukemia consortium

Leukemic transformation (LT) of a myeloproliferative neoplasm (MPN) is associated with a dismal prognosis and no medical therapies have shown a survival improvement in patients with MPN in blast phase (MPN-BP). Effective therapies for the treatment of MPN-BP are a serious unmet need. Consensus response criteria do not exist for the treatment of patients with MPN-BP and this is necessary for the uniformed reporting of treatment response in clinical trials. We have identified relevant MPN and MPN-BP features in order to define treatment response categories that reflect hematological, clinical, pathological, cytogenetic and molecular changes after therapeutic intervention. We plan to validate these proposed response criteria within multi-centered clinical trials.

A Case Report of Chronic Myelogenous Leukemia in a Patient With Multiple Myeloma and a Review of the Literature

Introduction Multiple myeloma (MM) is a plasma cell malignancy of lymphoid cell lineage with an annual incidence rate of 5.6 cases per 100,000 and a median age at time of diagnosis of 70 years. Chronic myelognous leukemia (CML) is a malignancy of myeloid cell lineage charcterized by the t(9;22) (q34;q11) reciprocal translocation, known as he Philadelphia (Ph) chromosome, which produces the BCR-ABL1 ybrid fusion. CML has an annual incidence rate of 1 to 2 cases per 00,000 and a mean age at time of diagnosis of 65 years. The occurrence of these 2 uncommon diseases in the same patient is extremely rare, and, since 1972, there have been 15 cases reported in the world literature. The question of the origin of these 2 malignancies in such patients remains unanswered. Here we describe the

A phase II study of panobinostat in patients with primary myelofibrosis (PMF) and post-polycythemia vera/essential thrombocythemia myelofibrosis (post-PV/ET MF).

Myelofibrosis is a chronic and progressive myeloproliferative neoplasm characterized by anemia, splenomegaly, debilitating symptoms and leukemic transformation. Ruxolitinib, an oral JAK1/2 inhibitor, is highly effective in ameliorating systemic symptoms and reducing splenomegaly. Current clinical research is focused on the evaluation of agents based on pre-clinical rationale that can result in disease course modification. Panobinostat is a pan-histone deacetylase inhibitor that has demonstrated clinical activity as a single agent in early phase trials of myelofibrosis. We previously conducted a phase I trial of panobinostat monotherapy in patients with myelofibrosis and determined 25mg thrice weekly as the recommended phase II dose. We then completed an investigator initiated, Simon 2-stage, phase II trial of 22 myelofibrosis patients at our single institution. After 6 cycles of therapy, the overall response rate by IWG-MRT criteria was 36% (8/22; 95% CI: 16-56%). The median percent reduction in spleen volume was 34% (range, 1.6%-73%) in eight evaluable patients. The average reduction in JAK2V617F allele burden was 6.8% (Range; -4.0% to 20.2%) and one patient obtained a complete molecular response. Six patients remained on therapy in the extension phase for a median of 18 months (range, 7-44). Treatment discontinuation was frequent due to patient/physician perception of therapy ineffectiveness. The optimal dosing of panobinostat for the treatment of MF remains somewhat ill-defined but appears to be most effective and better tolerated when administered at lower doses over a prolonged duration of therapy.

Signaling pathways in lymphoma: pathogenesis and therapeutic targets

Lymphoma is the fifth most common cancer in the USA. Most lymphomas are classified as non-Hodgkins lymphoma, and nearly 95% of these cancers are of B-cell origin. B-cell receptor (BCR) surface expression and BCR functional signaling are critical for survival and proliferation of both healthy B cells, as well as most B-lymphoma cells. Agents that inhibit various components of the BCR signaling pathway, as well as parallel signaling pathways, are currently in clinical trials for the treatment of various lymphoma subtypes, including those targeting isoforms of PI3K, mTOR and BTK. In this review, we describe the signaling pathways in healthy mature B cells, the aberrant signaling in lymphomatous B cells and the rationale for clinical trials of agents targeting these pathways as well as the results of clinical trials to date. We propose that the entry into a kinase inhibitor era of lymphoma therapy will be as transformative for our patients as the advent of the antibody or chemotherapy era before it.

An Unusual Cause of Acute Liver Failure: Three Cases of Hemophagocytic Lymphohistiocytosis Presenting at a Transplant Center

Acquired hemophagocytic lymphohistiocytosis (HLH) is a rare life-threatening disorder of the immune system. Hemophagocytic lymphohistiocytosis has been associated with infections, autoimmune disorders, and malignancy. This case series describes three patients admitted to an academic liver transplant center from February 2014 to February 2015 with acute liver failure (ALF) who were ultimately diagnosed with HLH. All cases were female patients (44 to 53 years of age) transferred for workup of ALF. All developed fevers and cytopenias and underwent rapid evaluation for liver transplant by a multidisciplinary team. A complete workup for ALF was negative for intrinsic liver disease and none had significant alcohol or toxin exposure. The patients had liver biopsies showing diffuse lobular necroinflammation, of which two had evidence of hemophagocytosis on histopathology. The diagnosis of HLH was made by bone marrow biopsy featuring histiocytes with hemophagocytosis. All cases were treated with chemotherapy, but died during their hospitalization. Hemophagocytic lymphohistiocytosis can present as ALF in adult patients. Given the low success rate of treatment, early diagnosis is critical. Therefore, a high degree of suspicion should be exercised in patients with unexplained ALF.

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.

An unusual case of donor-derived myelodysplastic syndrome following double-unit umbilical cord blood transplantation in acute lymphoblastic leukemia.

Umbilical cord-blood transplantation is considered an effective treatment strategy for acute lymphoblastic leukemia (ALL) when a human leukocyte antigen (HLA)-matched donor is unavailable. The use of a second unit helps ensure engraftment in larger adults and those with comorbidities, even though only one unit engrafts in most patients. Herein, we present the clinical and laboratory characteristics of a patient who developed donor-derived myelodysplastic syndrome (ddMDS) after double umbilical cord-blood transplantation (dUCB HSCT). To our knowledge, no cases of ddMDS have been described in a patient with a history of ALL in molecular remission after receiving a dUCB HSCT. Current molecular techniques, including analysis of short tandem repeats (STR) and fluorescence in situ hybridization (FISH) allowed us to firmly establish donor origin.