Treatment approaches in myelofibrosis with myeloid metaplasia: the old and the new

Leveraging JAK-STAT regulation in myelofibrosis to improve outcomes with allogeneic hematopoietic stem-cell transplant

Primary myelofibrosis (PMF) is a disease characterized by bone marrow fibrosis, extramedullary hematopoiesis, risk of transformation to acute myeloid leukemia, and a substantial symptom burden with diminished quality of life. Allogeneic hematopoietic cell transplantation (HCT) is the only curative option; however, disease relapse and graft versus host disease (GVHD) are significant barriers to long-term survival. The discovery of the JAK2 V617F mutation, and subsequent development of JAK inhibitors, resulted in improved survival and significant improvements in spleen volumes and symptom scores. Though the effect of JAK inhibition on transplant outcome is poorly understood, using JAK inhibition to achieve maximal response prior to HCT is standard practice at major centers. After allogeneic HCT, a significant proportion of patients with steroid-refractory GVHD have clinical responses to JAK inhibition. Targeting this pathway is a key component in the management of patients with PMF before and after allogeneic HCT.

Adenoviral-mediated TGF-β1 inhibition in a mouse model of myelofibrosis inhibit bone marrow fibrosis development

Myelofibrosis is characterized by excessive deposits of extracellular matrix proteins, which occur as a marrow microenvironment reactive response to cytokines released from the clonal malignant myeloproliferation. The observation that mice exposed to high systemic levels of thrombopoietin (TPO) invariably developing myelofibrosis has allowed demonstration of the crucial role of transforming growth factor (TGF)-beta1 released by hematopoietic cells in the onset of myelofibrosis. The purpose of this study was to investigate whether TGF-beta1 inhibition could directly inhibit fibrosis development in a curative approach of this mice model. An adenovirus encoding for TGF-beta1 soluble receptor (TGF-beta-RII-Fc) was injected either shortly after transplantation (preventive) or 30 days post-transplantation (curative). Mice were transplanted with syngenic bone marrow cells transduced with a retrovirus encoding for murine TPO. All mice developed a myeloproliferative syndrome. TGF-beta-RII-Fc was detected in the blood of all treated mice, leading to a dramatic decrease in TGF-beta1 level. Histological analysis show that the two approaches (curative or preventive) were successful enough to inhibit bone marrow and spleen fibrosis development in this model. However, lethality of TPO overexpression was not decreased after treatment, indicating that in this mice model, myeloproliferation rather than fibrosis was probably responsible for the lethality induced by the disorder.

Advances in the therapy of chronic idiopathic myelofibrosis

The molecular basis of chronic idiopathic myelofibrosis (CIMF) has remained elusive, thus hampering the development of effective targeted therapies. However, significant progress regarding the molecular mechanisms involved in the pathogenes is of this disease has been made in recent years that will likely provide ample opportunity for the investigation of novel therapeutic approaches. At the fore front of these advances is the discovery that 35%-55% of patients with CIMF harbor mutations in the Janus kinase 2 tyrosine kinase gene. Until very recently, the management of patients with CIMF involved the use of supportive measures, including growth factors, transfusions, or interferon, and the administration of cyto-reductive agents, such as hydroxyurea and anagrelide. However, several trials have demonstrated the efficacy of antiangiogenic agents alone or in combination with corticosteroids. In addition, the use of reduced-intensity conditioning allogeneic stem cell transplantation has resulted in prolonged survival and lower transplant-related mortality.

Prognosis in transplant-eligible patients with agnogenic myeloid metaplasia

BACKGROUND

Allogeneic hematopoietic stem cell transplantation is potentially curative in agnogenic myeloid metaplasia (AMM) but is associated with substantial mortality and morbidity that necessitates accurate identification of patients in whom benefit outweighs risk. The current study describes the natural history of AMM in transplant-eligible patients and proposes a new prognostic scoring system that favorably compares with other established models.

METHODS

Patients diagnosed with AMM before the age of 60 years and seen at Mayo Clinic were identified and the diagnosis confirmed. Relevant demographic, clinical, and laboratory characteristics were abstracted, and the impact of various parameters on overall survival (OS) was evaluated with univariate and multivariate analyses.

RESULTS

A cohort of 160 patients with AMM is described. OS was 78 months. Multivariate analysis identified a hemoglobin level of <10 g/dL, white blood cell count of either <4 or >30x10(9)/L, platelet count of <100x10(9)/L, presence of constitutional symptoms, and hepatomegaly as independent predictors of inferior survival. The first 3 complete blood count-based parameters were combined into a new scoring system that resulted in median survivals of 155, 69, and 24 months in the presence of 0, 1, or >or=2 adverse features. The chi-square value for the new model was 80.6 compared with 51.4, 48.4, and 43.7 for the models by Dupriez, Cervantes, and Visani, respectively.

CONCLUSIONS

A new scoring system based on blood count at the time of diagnosis can adequately stratify by risk transplant-eligible patients with AMM and can accurately identify high-risk as well as intermediate-risk disease. The new system displayed a stronger discriminative value, between risk categories, compared with currently existing prognostic models.

Pathogenesis of myelofibrosis with myeloid metaplasia

The primary disease process in myelofibrosis with myeloid metaplasia (MMM) is clonal myeloproliferation with varying degrees of phenotypic differentiation. This is characteristically accompanied by secondary intramedullary collagen fibrosis, osteosclerosis, angiogenesis, and extramedullary hematopoiesis. Modern clonality studies have confirmed the multipotent stem-cell origin of the neoplastic process in MMM. The nature of the specific oncogenic mutation(s) is currently being unraveled with the recent discovery of an association between a somatic point mutation of JAK2 tyrosine kinase (V617F) and bcr/abl-negative myeloproliferative disorders, including MMM. The pathogenetic mechanisms that underlie the secondary bone marrow stromal changes in MMM are also incompletely understood. Mouse models of this latter disease aspect have been constructed by either in vivo overexpression of thrombopoietin (TPOhigh mice) or megakaryocyte lineage restricted underexpression of the transcription factor GATA-1 (GATA-1low mice). Gene knockout experiments using such animal models have suggested the essential role of hematopoietic cell-derived transforming growth factor beta1 in inducing bone marrow fibrosis and stromal cell-derived osteoprotegerin in promoting osteosclerosis. However, experimental myelofibrosis in mice does not recapitulate clonal myeloproliferation that is fundamental to human MMM. Other cytokines that are implicated in mediating myelofibrosis and angiogenesis in MMM include basic fibroblast, platelet-derived, and vascular endothelial growth factors. It is currently assumed that such cytokines are abnormally released from clonal megakaryocytes as a result of a pathologic interaction with neutrophils (eg, emperipolesis). This latter phenomenon, through neutrophil-derived elastase, could also underlie the abnormal peripheral-blood egress of myeloid progenitors in MMM.

The JAK2V617F tyrosine kinase mutation in myelofibrosis with myeloid metaplasia: lineage specificity and clinical correlates

An association between an activating JAK2 mutation (JAK2(V617F)) and BCR/ABL-negative myeloproliferative disorders was recently reported in multiple simultaneous publications. In the current study, mutation analysis for JAK2(V617F) was performed in peripheral blood mononuclear cells (PBMC) from 157 patients with myelofibrosis with myeloid metaplasia (MMM) including 117 with agnogenic (AMM), 22 with postpolycythaemic (PPMM), and 18 with post-thrombocythaemic (PTMM) myeloid metaplasia. The detection rate for JAK2(V617F) was significantly higher in PPMM (91%; homozygous in 18%) compared with either AMM (45.3%; homozygous in 2.6%) or PTMM (38.9%; homozygous in 11.1%). Concomitant analysis in granulocytes (n=57) and CD34(+) cells (n=25) disclosed a higher incidence of homozygous JAK2(V617F) mutation but the overall mutation rate was similar to that obtained from PBMC. JAK2(V617F) was not detected in DNA derived from T cells (n=19). In AMM, the presence of JAK2(V617F) was associated with an older age at diagnosis and a history of thrombosis or pruritus. Multivariate analysis identified only age and the Dupriez prognostic score as independent prognostic factors; JAK2(V617F) had no prognostic significance. In conclusion, JAK2(V617F) is a myeloid lineage-specific event, its incidence in MMM is significantly higher with an antecedent history of polycythaemia vera (PV), and its presence in AMM does not affect prognosis but is associated with PV-characteristic clinical features.

Recombinant human erythropoietin in the treatment of nonrenal anemia

Recombinant human erythropoietins (rhEPO) reliably increase hemoglobin levels in cancer patients experiencing chemotherapy-associated anemia. However, in patients with "anemia of cancer" not being treated with chemotherapy, rhEPO appears less effective. Recently, two studies have been broadly discussed which have raised concern on the concomitant use of erythropoietin and chemo- or radiation therapy in cancer patients. In addition, use of rhEPO is generally not considered cost-effective. Thus, the application of rhEPO should be limited to indications with proven clinical benefit. This review will provide an overview of the state of the art use of rhEPO in anemic patients and will discuss future developments.

Single-agent thalidomide induces response in T-cell lymphoma

T-cell lymphoma is an aggressive lymphoma that cannot be cured despite aggressive therapy, including autologous stem cell transplantation. Thalidomide is an immunomodulatory drug with numerous properties that has proven effective in relapsed multiple myeloma and, to a lesser extent, in other hematologic diseases. We report three cases of relapsed refractory T-cell lymphoma treated with thalidomide with a good tumor response.