Biology and management of idiopathic myelofibrosis

The role of allogeneic SCT in primary myelofibrosis: a British Society for Blood and Marrow Transplantation study

Fifty-one patients with primary myelofibrosis (PMF) received allogeneic haematopoietic stem cell transplants from related (n=33) or unrelated (n=18) donors. Twenty-seven patients, 19-54 years old, were prepared with myeloablative regimens including CY plus BU (n=4) or TBI (n=23). Twenty-four patients, 40-64 years old, received reduced-intensity conditioning (RIC) regimens. All RIC regimens contained fludarabine, combined with melphalan (n=19) or BU (n=5), and alemtuzumab or anti-thymocyte globulin (ATG) in the majority (n=19). Four patients (17%) in the RIC group had primary graft failure. Previous splenectomy reduced time to engraftment in the RIC group (13 versus 20 days; P=0.008). For MA and RIC groups, respectively, at 3 years, overall survival rates were 44 and 31% (P=0.67), progression-free survival 44 and 24% (P=0.87), and actuarial relapse rates 15 and 46% (P=0.06). Non-relapse mortality at 3 years was 41% for the myeloablative and 32% for the RIC group. Acute GVHD occurred in 29 and 38% of patients in the myeloablative and RIC groups, respectively. Extensive chronic GVHD developed in 30 and 35% of evaluable patients, respectively.

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.

Recovery of normal autologous myelopoiesis after graft rejection following allogeneic bone marrow transplant for agnogenic myeloid metaplasia

Allogeneic hematopoietic transplantation is the only currently available therapy that has the potential to cure agnogenic myeloid metaplasia (AMM) or primary myelofibrosis (PMF). Amelioration of fibrosis and eradication of the abnormal clone is thought to occur through the repopulation of marrow by donor-derived hematopoiesis and graft-vs.-host reaction leading to graft vs. tumor effect. We report here a 50-year-old female with AMM/PMF, conditioned with busulfan and cyclophosphamide, who rejected a single locus (HLA-B) mismatched bone marrow transplant from her daughter, but recovered normal autologous hematopoiesis with disappearance of marrow fibrosis and extramedullary hematopoiesis. Variable number tandem repeats (VNTR) analysis showed a gradual loss of donor-derived hematopoietic cells with recovery of autologous hematopoiesis. This case therefore illustrates that eradication of AMM/PMF in this patient with myeloablative chemotherapy combined with a transient allogeneic effect was sufficient to suppress the abnormal stem cell clone associated with AMM/PMF with subsequent cure.

Allogeneic hematopoietic stem-cell transplantation with reduced-intensity conditioning in intermediate- or high-risk patients with myelofibrosis with myeloid metaplasia

A total of 21 patients with myelofibrosis with myeloid metaplasia (MMM), with a median age of 54 years (range, 27-68 years), were prepared with a reduced-intensity conditioning (RIC) regimen. The patients received an allogeneic marrow (n = 3) or peripheral blood stem-cell (n = 18) transplant from HLA-matched related (n = 18) or unrelated (n = 2), or 1 Ag-mismatched related (n = 1), donors. RIC regimens included fludarabine/total body irradiation 200 cGy (n = 5) or 450 cGy (n = 1), fludarabine/melphalan (n = 7), thiotepa/cyclophosphamide (n = 7), and thiotepa/fludarabine (n = 1). At the time of transplantation, all of the patients were at intermediate (n = 13) or high (n = 8) risk, according to the Dupriez classification. Of the patients, 19 had grade III or IV marrow fibrosis. All of the patients achieved full engraftment but one. Posttransplantation chimerism analysis showed more than 95% donor cells in 18 patients, while 2 patients achieved complete donor chimerism after donor leukocyte infusion (DLI). Acute graft-versus-host disease (GVHD) grades II to IV was observed in 7 patients, grades III to IV in 2, and extensive chronic GVHD in 8 of 18 evaluable patients. There were 3 patients who died from acute GVHD, infection, and relapse. There are 18 patients alive 12 to 122 months (median, 31 months) after transplantation, and 17 are in remission (1 after a second transplantation). The use of RIC regimens in allogeneic stem cell transplantation results in prolonged survival in intermediate/high-risk MMM patients.

Detection of Aberrant Gene Expression in CD34+Hematopoietic Stem Cells from Patients with Agnogenic Myeloid Metaplasia Using Oligonucleotide Microarrays

Agnogenic myeloid metaplasia (AMM) is a clonal stem cell disorder that leads to ineffective hematopoiesis, bone marrow fibrosis, and extramedullary hematopoiesis. The molecular mechanisms underlying the development of this syndrome are currently unknown. Therefore, the aim of this study was to characterize aberrant gene expression in CD34+ hematopoietic stem cells from patients with AMM. We used oligonucleotide microarrays to analyze gene expression profiles in CD34+ hematopoietic stem cells from patients with AMM compared with expression in CD34+ cells from healthy individuals. We identified 95 highly differentially expressed genes (48 upregulated and 47 down-regulated) that are potentially involved in regulating abnormal hematopoietic proliferation and differentiation and confirmed many of them by quantitative polymerase chain reaction. Using class membership prediction analysis, we identified 75 genes whose expression profiles can accurately differentiate AMM samples from the controls. Using these 75 genes, we were able to discriminate patients with AMM from the controls by hierarchical clustering (Spearman's confidence correlation). The predictive power of these genes was verified by applying the algorithm to an unknown test set containing expression data from eight additional CD34+ samples (four AMM, four control). Our results indicate that a subset of genes may be used to differentiate patients with AMM from healthy individuals. Furthermore, we identify 95 genes whose aberrant expression may be involved in AMM.

Diagnostic and prognostic value of colony formation of hematopoietic progenitor cells in myeloid malignancies

Hematopoietic progenitor cells are capable of forming colonies of mature blood cells in semisolid media in response to specific growth factors. Colony assays have been extensively used for many years to study normal and malignant hematopoiesis in vitro. In fact, these assays have provided an excellent research tool for investigating growth and differentiation of progenitor cells in response to positive and negative regulators of hematopoiesis. However, apart from their role in basic research, colony assays are also widely used in routine clinical practice in the diagnosis of various hematologic disorders, such as aplastic anemia, myelodysplastic syndromes and myeloproliferative disorders. This review summarizes our current knowledge on the diagnostic value and prognostic significance of the growth of progenitor cells in peripheral blood and bone marrow in patients with myeloid malignancies.

FLAG chemotherapy followed by allogeneic stem cell transplant using nonmyeloablative conditioning induces regression of myelofibrosis with myeloid metaplasia

A 38-year-old woman with agnogenic myeloid metaplasia complicated by the poor prognostic factors of severe osteosclerosis, prominent hepatosplenomegaly, and profound anemia was treated with FLAG chemotherapy to decrease her organomegaly before undergoing a nonmyeloablative allogeneic stem cell transplant from a matched-sibling donor. The patient's pre- and post transplant course were complicated by an autoimmune disorder and her post transplant course was complicated by severe hepatic and gastrointestinal GVHD. A technetium-99m sulfur colloid scan 4 months post transplant and bone marrow studies 8 months post transplant demonstrated intramedullary hematopoiesis, complete resolution of marrow fibrosis, and partial resolution of osteosclerosis.

Molecular markers in myeloproliferative disorders: from classification to prognosis?

The recent description of molecular markers in patients with myeloproliferative disorders (MPDs) has raised several questions: does the presence of multiple markers coincide in individual patients or can a patient acquire some markers selectively? Do the markers distinguish molecular categories of MPDs? Do these categories coincide with the clinically defined subgroups of MPDs: PV, ET and IMF? If not, which system of categorization is more useful to the patient and his physician, the molecular one or the clinical one, and why? The present review will summarize the current knowledge of molecular markers in MPDs and discuss today's answers to the above questions. Since our knowledge of the molecular basis of MPDs is rapidly expanding, it is my hope that this review will soon be outdated.

Stem cell transplantation for myelofibrosis: a report from two Canadian centers

We describe the course of 25 patients with myelofibrosis (MF) due to agnogenic myeloid metaplasia (n=19) or essential thrombocytosis (n=6) who underwent allogeneic stem cell transplantation (SCT) at one of two Canadian centers. The median age at transplantation was 48.7 (IQR 45.9-50.4) years and transplantation was carried out at a median of 10.7 (IQR 5.67-26.5) months after diagnosis. Granulocyte engraftment (absolute neutrophil count >0.5 x 109/l) occurred at a median of 20 days after transplantation for splenectomized patients, compared with 27.5 days for nonsplenectomized individuals (P=0.03). Increased risk of grade II-IV acute graft-versus-host disease (P=0.04) was noted in patients transplanted after splenectomy. Patients with MF received 0.264+/-0.189 U of packed red blood cells per day over the first 180 days after transplantation, and remained dependent on red blood cell transfusions for a median of 123 (IQR 48-205) days. Complete remission of MF was documented in 33% of evaluable patients. The 1 year cumulative nonrelapse mortality was 48.3%. Median survival for this group of patients was 393 (IQR 109-1014+) days, with a projected 2-year overall survival of 41%. We conclude that allogeneic SCT offers a reasonable chance for prolonged survival in patients with advanced MF, but this occurs at the cost of considerable toxicity and nonrelapse mortality.

Polycythaemia vera: will new markers help us answer old questions?

The publication of the first molecular markers for polycythaemia vera (PV) has led to a renewed interest in finding the mutations leading to the development of this myeloproliferative disorder. A substantial amount of cell biological data on the PV stem cell, however, have been available for over two decades. This review will summarise, combine and integrate both fields of investigation. Based on this analysis, two alternative models for the development of myeloproliferative disorders are proposed.