Idiopathic myelofibrosis: pathogenesis to treatment

Chronic Lymphocytic Leukemia and Myelofibrosis

Background

Chronic lymphocytic lymphoma (CLL) can be associated with several malignancies, but rarely with myelofibrosis. Only isolated case reports in the literature described the association between CLL and primary myelofibrosis (PMF) in the same patient.

Objectives

We describe a case of CLL characterized by the development of PMF and a review of literature.

Methods

We describe an 86-year-old female diagnosed as having CLL and followed by the development of splenomegaly and progressively rising LDH levels 27 months later. A bone marrow biopsy was consistent with the diagnosis of PMF, with positive JAK-2 V617F mutation. We also review the clinical and molecular characteristics of patients with CLL and PMF.

Results

Patients with CLL and PMF are usually older. A lead diagnosis of CLL harbored by PMF is the most common clinical course, although concomitant diseases may occur in 31.7% of patients. JAK-2 V617F mutation can be found in 48.7% of patients.

Conclusion

This case reported here constitutes an unusual situation of CLL characterized by the development of PMF. Etiologic and pathogenic associations-the role of t (1; 6) and JAK-2 V617F mutation-are discussed.

Identifying and enriching platelet-producing human stem cell-derived megakaryocytes using factor V uptake

Stem cell-derived platelets have the potential to replace donor platelets for transfusion. Defining the platelet-producing megakaryocytes (MKs) within the heterogeneous MK culture may help to optimize the in vitro generation of platelets. Using 2 human stem cell models of megakaryopoiesis, we identified novel MK populations corresponding to distinct maturation stages. An immature, low granular (LG) MK pool (defined by side scatter on flow cytometry) gives rise to a mature high granular (HG) pool, which then becomes damaged by apoptosis and glycoprotein Ib α chain (CD42b) shedding. We define an undamaged HG/CD42b⁺ MK subpopulation, which endocytoses fluorescently labeled coagulation factor V (FV) from the media into α-granules and releases functional FV⁺CD42b⁺ human platelet-like particles in vitro and when infused into immunodeficient mice. Importantly, these FV⁺ particles have the same size distribution as infused human donor platelets and are preferentially incorporated into clots after laser injury. Using drugs to protect HG MKs from apoptosis and CD42b shedding, we also demonstrate that apoptosis precedes CD42b shedding and that apoptosis inhibition enriches the FV⁺ HG/CD42b⁺ MKs, leading to increased platelet yield in vivo, but not in vitro. These studies identify a transition between distinct MK populations in vitro, including one that is primed for platelet release. Technologies to optimize and select these platelet-ready MKs may be important to efficiently generate functional platelets from in vitro-grown MKs.

Pathological interactions between hematopoietic stem cells and their niche revealed by mouse models of primary myelofibrosis

Primary myelofibrosis (PMF) belongs to the Philadelphia-negative myeloproliferative neoplasms and is a hematological disorder caused by abnormal function of the hematopoietic stem cells. The disease manifests itself with a plethora of alterations, including anemia, splenomegaly and extramedullary hematopoiesis. Its hallmarks are progressive marrow fibrosis and atypical megakaryocytic hyperplasia, two distinctive features used to clinically monitor disease progression. In an attempt to investigate the role of abnormal megakaryocytopoiesis in the pathogenesis of PMF, several transgenic mouse models have been generated. These models are based either on mutations that interfere with the extrinsic (thrombopoietin and its receptor, MPL) and intrinsic (the GATA1 transcription factor) control of normal megakaryocytopoiesis, or on known genetic lesions associated with the human disease. Here we provide an up-to-date review on the insights into the pathobiology of human PMF achieved by studying these animal models, with particular emphasis on results obtained with Gata1(low) mice.

Signal transduction in the chronic leukemias: implications for targeted therapies

The chronic leukemias, including chronic myeloid leukemia (CML), the Philadelphia-negative myeloproliferative neoplasms (MPNs), and chronic lymphocytic leukemia (CLL), have been characterized extensively for abnormalities of cellular signaling pathways. This effort has led to the elucidation of the central role of dysregulated tyrosine kinase signaling in the chronic myeloid neoplasms and of constitutive B-cell receptor signaling in CLL. This, in turn, has stimulated the development of small molecule inhibitors of these signaling pathways for therapy of chronic leukemia. Although the field is still in its infancy, the clinical results with these agents have ranged from encouraging (CLL) to spectacular (CML). In this review, we summarize recent studies that have helped to define the signaling pathways critical to the pathogenesis of the chronic leukemias. We also discuss correlative studies emerging from clinical trials of drugs targeting these pathways.

Regulation of fas/fas ligand-mediated apoptosis by nuclear factor of activated T cells in megakaryocytes

Signal transduction pathways in megakaryocytes, a rare population of bone marrow cells, are poorly understood. We have previously shown that the calcineurin-dependent transcription factor Nuclear Factor of Activated T cells (NFAT) is expressed in megakaryocytes and is required for the transcription of specific megakaryocytic genes. The biological role of NFAT in megakaryocytes, however, is unknown. Here we show that activation of the calcineurin/NFAT pathway in megakaryocytes forces the cells to go into apoptosis. Calcineurin/NFAT activation in megakaryocytes leads to membrane expression of Fas ligand (FASLG), a pro-apoptotic member of the tumour necrosis factor superfamily. Expression of FASLG was augmented in cells stably overexpressing NFATC2 and suppressed in cells either pretreated with the calcineurin inhibitor ciclosporin A (CsA) or expressing the specific peptide inhibitor of NFAT, VIVIT. In cocultures with Fas-expressing Jurkat T cells, the presence of activated megakaryocytic cells, but not of unstimulated cells or cells stimulated in the presence of CsA, significantly induced apoptosis in Jurkat cells in a Fas/FASLG- and NFAT-dependent manner. These results represent the first evidence for a biological function of the calcineurin/NFAT pathway in megakaryocytes, and suggest that the biological role of megakaryocytes may include the induction of apoptosis in bystander cells.

Myeloproliferative neoplasms cause glomerulopathy

Myeloproliferative neoplasms are clonal hematopoietic stem cell disorders that can produce an undefined glomerulopathy. To better characterize the glomerular disease associated with myeloproliferative neoplasms, we evaluated features of 11 patients with myeloproliferative neoplasm-related glomerulopathy that included 8 patients with primary myelofibrosis, and 1 each with chronic myelogenous leukemia, polycythemia vera, and essential thrombocythemia. Indications for biopsy were nephrotic-range proteinuria (nephrotic syndrome in four) and chronic renal insufficiency. The mean time from diagnosis of the neoplasms to biopsy was 7.2 years. Histologically, mesangial sclerosis and hypercellularity were seen in all 11 cases, segmental sclerosis in 8, features of chronic thrombotic microangiopathy in 9, and intracapillary hematopoietic cells in 4. On follow-up, seven patients had persistent renal dysfunction and four progressed to end-stage renal disease (ESRD). Thus, glomerulopathy appears to be a late complication of myeloproliferative neoplasms, particularly primary myelofibrosis, with guarded prognosis. Greater awareness of this entity and larger studies are needed to define possible therapies.

Bilateral ureteral obstruction due to primary myelofibrosis caused hyperuricaemia

In healthy population, uric acid comprises the major component of 10-20% of renal stones. Extreme hiperuricaemia is seen in cancer patients with tumor lysis syndrome (TLS) which is classically associated with haematological malignancies with rapid tumor growth rates such as acute lymphoid leukaemia and high grade lymphomas. Primary melofibrosis (Agnogenic myeloid metaplasia- AMM) is a chronic myeloproliferative disease characterized by splenomegaly, a leukoerythroblastic blood picture, teardrop poikilocytosis and varying degrees of marrow fibrosis. Due to the increased extramedullary haematopoiesis, hiperuricemia may occur. However, TLS in patients with AMM is, according to the available literature, described just in one patient. In this paper we present a case of a 47-year-old male patient who was admitted to the hospital with symptoms of fatigue and small amount of urine, and clinical signs of plethora and enlarged spleen. The laboratory findings showed leuko-and erythrocytosis, increased levels of urea-BUN (32 mmol/l) and creatinine (766 mmol/l) as well as uric acid (920 mmol/l). The immediate abdominal ultrasound confirmed extreme splenomegaly, but also showed bilateral hydronephrosis of grade II-III with two stones in proximal part of right ureter and one in proximal part of left ureter as well as empty bladder. Stones were not seen on plain film. Since the patient was in complete anuria, with further rapid elevation of BUN and creatinine levels, bilateral ureteral stents were applicated together with extensive hydration, urine alkalization and administration of allopurinol which resulted in the complete recovery of kidney function. The bone marrow biopsy was also performed and histopathological diagnosis was: Hypercellulary phase of AMM.

Hematological Oncology: further ahead

This editorial presents the new editorial structure of Hematological Oncology and summarizes the topics of interest of the journal. Authors are strongly encouraged to submit quality manuscripts regarding all the aspects of haematologic cancers via the Hematological Oncology website at http://mc.manuscriptcentral.com/hon.

Dramatic remission of anemia after thymectomy in a patient of idiopathic myelofibrosis with thymoma

Anemia is one of the characteristics of idiopathic myelofibrosis (IMF), and malignant thymoma is usually associated with various hematologic disorders, including anemia, pancytopenia, and hypogammaglobulinemia. However, the relationship between IMF and malignant thymoma has not been published before. Here, we report a 48-year-old woman who was initially diagnosed of IMF with severe anemia and transfusion dependent. Five years later, malignant thymoma was found when she was examined for chronic cough. After performing extended thymectomy, her anemia dramatically recovered to normal and sustained for 2 years till last follow-up. Her splenomegaly and myelofibrosis were also improved. We hypothesized that her malignant thymoma induced the progression of IMF, especially in anemia.

A new MALDI-TOF-based assay for monitoring JAK2 V617F mutation level in patients undergoing allogeneic stem cell transplantation (allo SCT) for classic myeloproliferative disorders (MPD)

JAK2 V617F mutation is found in a high proportion of MPD patients. We developed a quantitative assay for the detection of the JAK2 mutation and demonstrated its clinical utility in MPD patients who underwent SCT. Sixty percent of the patients were JAK2 V617F positive prior to the SCT (mean mutation levels 74%, range 16-98%). After the procedure, the mutation levels progressively decreased and were in correlation with the donor-recipient chimerism status (r=0.97, p<0.001). At a median follow up of 16 months (range 2-58), 9/15 patients are alive and in CR. The levels of the JAK2 V617F mutation reached 0% in all surviving patients.