Prognostic diversity among cytogenetic abnormalities in myelofibrosis with myeloid metaplasia

Progression of Myeloproliferative Neoplasms (MPN): Diagnostic and Therapeutic Perspectives

Classical BCR-ABL-negative myeloproliferative neoplasms (MPN) are a heterogeneous group of hematologic malignancies, including essential thrombocythemia (ET), polycythemia vera (PV), and primary myelofibrosis (PMF), as well as post-PV-MF and post-ET-MF. Progression to more symptomatic disease, such as overt MF or acute leukemia, represents one of the major causes of morbidity and mortality. There are clinically evident but also subclinical types of MPN progression. Clinically evident progression includes evolution from ET to PV, ET to post-ET-MF, PV to post-PV-MF, or pre-PMF to overt PMF, and transformation of any of these subtypes to myelodysplastic neoplasms or acute leukemia. Thrombosis, major hemorrhage, severe infections, or increasing symptom burden (e.g., pruritus, night sweats) may herald progression. Subclinical types of progression may include increases in the extent of bone marrow fibrosis, increases of driver gene mutational allele burden, and clonal evolution. The underlying causes of MPN progression are diverse and can be attributed to genetic alterations and chronic inflammation. Particularly, bystander mutations in genes encoding epigenetic regulators or splicing factors were associated with progression. Finally, comorbidities such as systemic inflammation, cardiovascular diseases, and organ fibrosis may augment the risk of progression. The aim of this review was to discuss types and mechanisms of MPN progression and how their knowledge might improve risk stratification and therapeutic intervention. In view of these aspects, we discuss the potential benefits of early diagnosis using molecular and functional imaging and exploitable therapeutic strategies that may prevent progression, but also highlight current challenges and methodological pitfalls.

Leukemia secondary to myeloproliferative neoplasms

Secondary acute myeloid leukemias (AMLs) evolving from an antecedent myeloproliferative neoplasm (MPN) are characterized by a unique set of cytogenetic and molecular features distinct from de novo AML. Given the high frequency of poor-risk cytogenetic and molecular features, malignant clones are frequently insensitive to traditional AML chemotherapeutic agents. Allogeneic stem cell transplant, the only treatment modality shown to have any beneficial long-term outcome, is often not possible given the advanced age of patients at time of diagnosis and frequent presence of competing comorbidities. Even in this setting, relapse rates remain high. As a result, outcomes are generally poor and there remains a significant unmet need for novel therapeutic strategies. Although advances in cancer genomics have dramatically enhanced our understanding of the molecular events governing clonal evolution in MPNs, the cell-intrinsic and -extrinsic mechanisms driving leukemic transformation at this level remain poorly understood. Here, we review known risk factors for the development of leukemic transformation in MPNs, recent progress made in our understanding of the molecular features associated with leukemic transformation, current treatment strategies, and emerging therapeutic options for this high-risk myeloid malignancy.

Expression of CD markers in JAK2V617F positive myeloproliferative neoplasms: Prognostic significance

Myeloproliferative neoplasms (MPNs) are clonal stem cell disorders characterized by the presence of JAK2^V617F mutation. Thrombohemorrhagic as well as autoimmune or inflammatory phenomena are common clinical outcomes of these disorders. Recent studies have shown that abnormality in frequency and function of blood cells manifested by an alteration in CD markers' expression patterns play a key role in these complications. So, there may be a relationship between CD markers' expressions and prognosis of JAK2^V617F positive MPNs. Therefore, in this review, we have focused on these abnormalities from the perspective of changing expressions of CD markers and assessment of the relationship between these changes with prognosis of JAK2^V617F positive MPNs. It can be stated that the abnormal expression of a large number of CD markers can be used as a prognostic biomarker for clinical outcomes including thrombohememorrhagic events, as well as autoimmune and leukemic transformation in JAK2^V617F positive MPNs. Considering the possible role of CD markers' expressions in JAK2^V617F MPNs prognosis, further studies are needed to confirm the relationship between the expression of CD markers with prognosis to be able to find an appropriate therapeutic approach via targeting CD markers.

Treatment With JAK Inhibitors in Myelofibrosis Patients Nullifies the Prognostic Impact of Unfavorable Cytogenetics

INTRODUCTION

In the era before Janus kinase (JAK) inhibitors, cytogenetic information was used to predict survival in myelofibrosis patients. However, the prognostic value of cytogenetics in the setting of JAK inhibitor therapy remains unknown.

PATIENTS AND METHODS

We performed a retrospective analysis of 180 patients with bone marrow biopsy-proven myelofibrosis from 3 US academic medical centers. We fit Cox proportional hazards models for overall survival and transformation-free survival on the bases of 3 factors: JAK inhibitor therapy as a time-dependent covariate, dichotomized cytogenetic status (favorable vs. unfavorable), and statistical interaction between the two. The median follow-up time was 37.1 months.

RESULTS

Among patients treated with best available therapy, unfavorable cytogenetic status was associated with decreased survival (hazard ratio = 2.31; P = .025). At initiation of JAK inhibitor therapy, unfavorable cytogenetics was (nonsignificantly) associated with increased survival compared to favorable cytogenetics (hazard ratio = 0.292; P = .172). The ratio of hazard ratios was 0.126 (P = .034). These findings were similar after adjusting for standard clinical prognostic factors as well as when measured against transformation-free survival.

CONCLUSION

The initiation of JAK inhibitor therapy appears to change the association between cytogenetics and overall survival. There was little difference in survival between treatment types in patients with favorable cytogenetics. However, the use of JAK inhibitor therapy among patients with unfavorable cytogenetics was not associated with worse survival compared to favorable cytogenetics. Our analyses suggest that initiation of JAK inhibitor therapy nullifies the negative prognostic implication of unfavorable cytogenetics established in the pre-JAK inhibitor therapy era.

Revised cytogenetic risk stratification in primary myelofibrosis: analysis based on 1002 informative patients

Current cytogenetic risk stratification in primary myelofibrosis (PMF) is two-tiered: ‘favorable’ and ‘unfavorable’. Recent studies have suggested prognostic heterogeneity within the unfavorable risk category. In 1002 consecutive patients, we performed stepwise analysis of impact on survival from individual and prognostically ordered cytogenetic abnormalities, leading to a revised three-tiered risk model: ‘very high risk (VHR)’—single/multiple abnormalities of −7, i(17q), inv(3)/3q21, 12p−/12p11.2, 11q−/11q23, or other autosomal trisomies not including + 8/ + 9 (e.g., +21, +19); ‘favorable’—normal karyotype or sole abnormalities of 13q−, +9, 20q−, chromosome 1 translocation/duplication or sex chromosome abnormality including -Y; ‘unfavorable’—all other abnormalities. Median survivals for VHR (n = 75), unfavorable (n = 190) and favorable (n = 737) risk categories were 1.2 (HR 3.8, 95% CI 2.9–4.9), 2.9 (HR 1.7, 95% CI 1.4–2.0) and 4.4 years and survival impact was independent of clinically derived prognostic systems, driver and ASXL1/SRSF2 mutations. The revised model was also effective in predicting leukemic transformation: HRs (95% CI) were 4.4 (2.0–9.4) for VHR and 2.0 (1.2–3.4) for unfavorable. The impact of driver mutations on survival was confined to favorable and that of ASXL1/SRSF2 mutations to favorable/unfavorable cytogenetic risk categories. The current study clarifies the prognostic hierarchy of genetic risk factors in PMF and provides a more refined three-tiered cytogenetic risk model.

Epigenetic dysregulation of secreted frizzled-related proteins in myeloproliferative neoplasms complements the JAK2V617F-mutation

Background

Secreted frizzled-related proteins (SFRPs) are antagonists of the Wnt signaling pathway, which plays a central role in stem cell maintenance and differentiation of stem cells and hematopoietic progenitors. Epigenetic downregulation of SFRPs by promoter hypermethylation has been described to be involved in the pathogenesis of hematopoietic malignancies. There is an association between aberrant Wnt signaling and the established cancer stem cell concept. In contrast to BCR-ABL1-positive chronic myeloid leukemia CML, BCR-ABL1-negative myeloproliferative neoplasms (Ph^-MPN) are characterized by the frequent occurrence of an autoactivating mutation in the JAK2 tyrosine kinase (JAK2V617F) or other mutations in the JAK-STAT pathway. However, pathogenetic mechanisms of JAK2 mutated or unmutated Ph^-MPN remain not completely understood. We determined the promoter methylation status of SFRP-1, -2, -4, and -5 in 57 MPN patient samples by methylation-specific polymerase chain reaction (PCR) (MSP). JAK2V617F was assessed by allele-specific PCR.

Results

Aberrant methylation among primary MPN samples was 4% for SFRP-1, 25% for SFRP-2, 2% for SFRP-4, and 0% for SFRP-5. Hypermethylation of SFRP-2, which was the most frequently hypermethylated gene in our study, could not be correlated to any specific MPN subtype. However, we detected a significant correlation between SFRP-2 methylation and presence of a JAK2V617F mutation (P = 0.008). None of the 10 CML samples showed any SFRP-methylation.

Conclusions

Our data indicate that epigenetic dysregulation of the Wnt signaling pathway is a common event in MPN with aberrant methylation of at least one SFRP being detected in 25% of the primary patient samples and in 30% if only accounting for Ph^-MPN. A significant correlation between SFRP-2 methylation and presence of JAK2V617F in our data supports the hypothesis that epigenetic dysregulation may be a complementary mechanism to genetic aberrations. Aberrant methylation of crucial stem cell maintenance genes seems to contribute to disease pathogenesis in Ph^-MPN.

Association of JAK2 mutation status and cytogenetic abnormalities in myeloproliferative neoplasms and myelodysplastic/myeloproliferative neoplasms

Myeloproliferative neoplasms and myelodysplastic/myeloproliferative neoplasms are heterogeneous disorders. JAK2 mutation testing and karyotyping are routinely used for diagnosis but have not been incorporated into risk stratification in Philadelphia chromosome-negative myeloproliferative neoplasms. This study correlated cytogenetic abnormalities with disease stage and JAK2 status. A total of 179 cases were analyzed for the JAK2 mutation. Among them, cytogenetic data were available for 97 cases-45 of 106 JAK2+ and 52 of 73 JAK2-. The JAK2+ group showed a higher frequency of cytogenetic anomalies than the JAK2- group (23/45 [51%] vs 14/52 [27%]). Chromosome 9, chromosome 7, and 20q- were recurrent abnormalities in the JAK2+ group, whereas 13q- and trisomy 21 were common in the JAK2- group. In the JAK2+ group, chromosome 7 and complex cytogenetic abnormalities were associated with excess blasts/blastic transformation (P < .05), whereas no cases with 20q- underwent blastic transformation. Our results suggest that incorporation of JAK2 mutation testing and karyotyping allows for monitoring of disease progression with prognostic and therapeutic implications.

A dynamic prognostic model to predict survival in primary myelofibrosis: a study by the IWG-MRT (International Working Group for Myeloproliferative Neoplasms Research and Treatment)

Age older than 65 years, hemoglobin level lower than 100 g/L (10 g/dL), white blood cell count greater than 25 × 109/L, peripheral blood blasts 1% or higher, and constitutional symptoms have been shown to predict poor survival in primary myelofibrosis (PMF) at diagnosis. To investigate whether the acquisition of these factors during follow-up predicts survival, we studied 525 PMF patients regularly followed. All 5 variables had a significant impact on survival when analyzed as time-dependent covariates in a multivariate Cox proportional hazard model and were included in 2 separate models, 1 for all patients (Dynamic International Prognostic Scoring System [DIPSS]) and 1 for patients younger than 65 years (age-adjusted DIPSS). Risk factors were assigned score values based on hazard ratios (HRs). Risk categories were low, intermediate-1, intermediate-2, and high in both models. Survival was estimated by the HR. When shifting to the next risk category, the HR was 4.13 for low risk, 4.61 for intermediate-1, and 2.54 for intermediate-2 according to DIPSS; 3.97 for low risk, 2.84 for intermediate-1, and 1.81 for intermediate-2 according to the age-adjusted DIPSS. The novelty of these models is the prognostic assessment of patients with PMF anytime during their clinical course, which may be useful for treatment decision-making.

Phase 2 study of CEP-701, an orally available JAK2 inhibitor, in patients with primary or post-polycythemia vera/essential thrombocythemia myelofibrosis

Few treatment options exist for patients with myelofibrosis (MF), and their survival is significantly shortened. Activating mutation of the JAK2 tyrosine kinase (JAK2(V617F)) is found in approximately 50% of MF patients. CEP-701 is a tyrosine kinase inhibitor that inhibits JAK2 in in vitro and in vivo experiments. We conducted a phase 2 clinical study of CEP-701 in 22 JAK2(V617F)-positive MF patients (80 mg orally twice daily), and 6 (27%) responded by International Working Group criteria (clinical improvement in all cases): reduction in spleen size only (n = 3), transfusion independency (n = 2), and reduction in spleen size with improvement in cytopenias (n = 1). Median time to response was 3 months, and duration of response was more than or equal to 14 months. No improvement was seen in bone marrow fibrosis or JAK2(V617F) allele burden. Phosphorylated STAT3 levels decreased from baseline in responders while on therapy. Eight patients (36%) experienced grade 3 or 4 toxicity, and 6 (27%) required dose reduction. Main side effects were myelosuppression (grade 3 or 4 anemia, 14%; and thrombocytopenia, 23%) and gastrointestinal disturbances (diarrhea, any grade, 72%; grade 3 or 4, 9%; nausea, grade 1 or 2 only, 50%; vomiting, grade 1 or 2 only, 27%). In conclusion, CEP-701 resulted in modest efficacy and mild but frequent gastrointestinal toxicity in MF patients. The study was registered at http://clinicaltrials.gov as NCT00494585.

International Prognostic Scoring System-independent cytogenetic risk categorization in primary myelofibrosis

Among 200 patients with primary myelofibrosis, karyotype at diagnosis was abnormal in 83 (42%). To assess their individual prognostic impact, specific cytogenetic abnormalities with more than or equal to 5 informative cases were identified and the rest grouped separately as "other abnormalities." Median survival in patients with sole +9 (n = 6), sole 20q- (n = 21), sole 13q- (n = 8), normal karyotype (n = 117), "other abnormalities" (n = 28), complex karyotype (n = 13), and sole +8 (n = 7) were "not reached," 112, 105, 80, 46, 34, and 28 months, respectively (P = .01). Accordingly, 4 cytogenetic risk groups were considered: (1) favorable (sole +9, 20q-, or 13q-), (2) normal, (3) unfavorable (complex karyotype or sole +8), and (4) "other abnormalities." Multivariable analysis confirmed the International Prognostic Scoring System (IPSS)-independent prognostic value of both 4-way and 2-way (ie, favorable/normal vs unfavorable/other abnormalities; IPSS-adjusted hazard ratio = 0.37; 95% confidence interval, 0.24-0.58) cytogenetic risk categorization (P < .01). The ability to prognostically dissect a specific IPSS category has major therapeutic implications.

The role of cytogenetic abnormalities as a prognostic marker in primary myelofibrosis: applicability at the time of diagnosis and later during disease course

Although cytogenetic abnormalities are important prognostic factors in myeloid malignancies, they are not included in current prognostic scores for primary myelofibrosis (PMF). To determine their relevance in PMF, we retrospectively examined the impact of cytogenetic abnormalities and karyotypic evolution on the outcome of 256 patients. Baseline cytogenetic status impacted significantly on survival: patients with favorable abnormalities (sole deletions in 13q or 20q, or trisomy 9 +/- one other abnormality) had survivals similar to those with normal diploid karyotypes (median, 63 and 46 months, respectively), whereas patients with unfavorable abnormalities (rearrangement of chromosome 5 or 7, or > or = 3 abnormalities) had a poor median survival of 15 months. Patients with abnormalities of chromosome 17 had a median survival of only 5 months. A model containing karyotypic abnormalities, hemoglobin, platelet count, and performance status effectively risk-stratified patients at initial evaluation. Among 73 patients assessable for clonal evolution during stable chronic phase, those who developed unfavorable or chromosome 17 abnormalities had median survivals of 18 and 9 months, respectively, suggesting the potential role of cytogenetics as a risk factor applicable at any time in the disease course. Dynamic prognostic significance of cytogenetic abnormalities in PMF should be further prospectively evaluated.

Karyotype complements the International Prognostic Scoring System for primary myelofibrosis

OBJECTIVES

The International Prognostic Scoring System (IPSS) for primary myelofibrosis (PMF) is based on five independent predictors of inferior survival: age >65 yr, hemoglobin <10 g/dL, leukocyte count >25 x 10(9)/L, circulating blasts > or =1%, and presence of constitutional symptoms. The presence of 0, 1, 2, and > or =3 adverse factors defines low, intermediate-1, intermediate-2, and high risk disease, respectively. We examined the additional prognostic relevance of karyotype.

METHODS

World Health Organization criteria were used for PMF diagnosis. Only patients with bone marrow cytogenetic studies at the time or within 1 yr of diagnosis and a minimum of 20 evaluable metaphases were considered. Cytogenetic findings were categorized as 'normal' vs. 'abnormal' or 'favorable' (normal or with sole abnormalities of 13q- or 20q-) vs. 'unfavorable' (all other abnormalities).

RESULTS

A total of 109 patients were studied (median age 63 yr). Numbers of patients in the above-listed four IPSS risk groups were 26, 31, 28, and 24, respectively. Cytogenetic results were abnormal in 33% of the patients and unfavorable in 21%. At a median follow-up of 35 months, 45 (41%) deaths were recorded. 'Unfavorable' (P = 0.008) but not 'abnormal' (P = 0.19) karyotype predicted shortened survival and its significance remained on multivariable analysis that included the IPSS or other prognostic tools as covariates. JAK2V617F, detected in 63 (58%) patients, was inconsequential to survival.

CONCLUSIONS

In PMF, specific cytogenetic abnormalities and not the mere presence of an abnormal karyotype provide important prognostic information that is not accounted for by the IPSS or other established risk factors.

JAK2 V617F mutational status predicts progression to large splenomegaly and leukemic transformation in primary myelofibrosis

Few investigators have evaluated the usefulness of the JAK2 V617F mutation for explaining the phenotypic variations and for predicting the risk of major clinical events in primary myelofibrosis (PMF). In a transversal survey we assayed by allele-specific polymerase chain reaction (PCR) the JAK2 V617F mutational status in 304 patients with PMF. Multiple DNA samples were collected prospectively from 64 patients, and a highly sensitive quantitative PCR was used as a confirmatory test. In a longitudinal prospective study we determined the progression rate to clinically relevant outcomes in 174 patients who had JAK2 mutation determined at diagnosis. JAK2 V617F was identified in 63.4% of patients. None of the V617F-negative patients who were sequentially genotyped progressed to become V617F positive, whereas progression rate from heterozygous to homozygous mutation was 10 per 100 patient-years. JAK2 V617F mutation contributed to hemoglobin, aquagenic pruritus, and platelet count variability, whereas homozygous mutation was independently associated with higher white blood cell count, larger spleen size, and greater need for cytoreductive therapies. Adjusting for conventional risk factors, V617F mutation independently predicted the evolution toward large splenomegaly, need of splenectomy, and leukemic transformation. We conclude that JAK2 V617F genotype should be considered in any future risk stratification of patients with PMF.

SNP array karyotyping allows for the detection of uniparental disomy and cryptic chromosomal abnormalities in MDS/MPD-U and MPD

We applied single nucleotide polymorphism arrays (SNP-A) to study karyotypic abnormalities in patients with atypical myeloproliferative syndromes (MPD), including myeloproliferative/myelodysplastic syndrome overlap both positive and negative for the JAK2 V617F mutation and secondary acute myeloid leukemia (AML). In typical MPD cases (N = 8), which served as a control group, those with a homozygous V617F mutation showed clear uniparental disomy (UPD) of 9p using SNP-A. Consistent with possible genomic instability, in 19/30 MDS/MPD-U patients, we found additional lesions not identified by metaphase cytogenetics. In addition to UPD9p, we also have detected UPD affecting other chromosomes, including 1 (2/30), 11 (4/30), 12 (1/30) and 22 (1/30). Transformation to AML was observed in 8/30 patients. In 5 V617F+ patients who progressed to AML, we show that SNP-A can allow for the detection of two modes of transformation: leukemic blasts evolving from either a wild-type jak2 precursor carrying other acquired chromosomal defects, or from a V617F+ mutant progenitor characterized by UPD9p. SNP-A-based detection of cryptic lesions in MDS/MPD-U may help explain the clinical heterogeneity of this disorder.

Advances in molecular diagnostics of myeloproliferative disorders

Incremental advances in the molecular pathogenesis of myeloproliferative disorders (MPDs) have had a substantial impact on clinical practice in terms of both diagnosis and treatment. An array of novel molecular methods are being developed and integrated into the current battery of tests for diagnosis and monitoring of treatment response. Primarily, subjective clinico-histologic approaches to diagnosis are being replaced by more objective semimolecular diagnostic algorithms. Furthermore, identification of disease-specific molecular markers has facilitated the development of small-molecule drugs for targeted therapy. This review provides an overview of MPDs with emphasis on molecular diagnostic tests and their incorporation into contemporary diagnostic and therapeutic algorithms.

Hematopoietic cell transplantation as curative therapy for idiopathic myelofibrosis, advanced polycythemia vera, and essential thrombocythemia

A total of 104 patients, aged 18 to 70 years, with a diagnosis of chronic idiopathic myelofibrosis (CIMF), polycythemia vera (PV), or essential thrombocythemia (ET) with marrow fibrosis were transplanted from allogeneic (56 related and 45 unrelated) or syngeneic (n = 3) donors. Busulfan (BU) or total body irradiation (TBI)-based myeloablative conditioning regimens were used in 95 patients, and a nonmyeloablative regimen of fludarabine plus TBI was used in 9 patients. The source of stem cells was bone marrow in 43 patients and peripheral blood in 61 patients. A total of 63 patients were alive at a follow-up of 1.3-15.2 years (median, 5.3 years), for an estimated 7-year actuarial survival rate of 61%. Eleven patients had recurrent/persistent disease, of whom 8 died. Nonrelapse mortality was 34% at 5 years. Patients conditioned with targeted BU (plasma levels 800-900 ng/mL) plus cyclophosphamide (tBUCY) had a higher probability of survival (68%) than other patients. Dupriez score, platelet count, patient age, and comorbidity score were statistically significantly associated with mortality in univariate models. In a multivariable regression model, use of tBUCY (P = .03), high platelet count at transplantation (P = .01 for PV/ET; P = .39 for other diagnoses), younger patient age (P = .04), and decreased comorbidity score (P = .03) remained statistically significant for improved survival. Our findings show that hematopoietic cell transplantation offers potentially curative treatment for patients with ICMF, PV, or ET.

Monocytosis is an adverse prognostic factor for survival in younger patients with primary myelofibrosis

We recently developed a modified Dupriez prognostic scoring system (PSS) that effectively discriminated between high-, intermediate-, and low-risk young patients (age < or =60 years) with primary myelofibrosis (PMF) based on the respective presence of none, one, or two or more of the following parameters: hemoglobin <10 g/dL, leukocyte count <4 or >30 x 10(9)L(-1), and platelet count <100 x 10(9)L(-1). The current study (n=129; median age, 52 years; 69 males) reveals, on multivariable analysis, that an absolute monocyte count of > or =1 x 10(9)L(-1) carries an independent predictive value (p=0.02), for an inferior survival, in addition to that provided by hemoglobin level (p=0.002), platelet count (0.02), and leukocyte count (p=0.16). The inclusion of the monocyte count as a fourth risk factor enabled the construction of a new and improved Mayo PSS; median survival was 173, 61, and 26 months in the absence of all four (low-risk), three (intermediate-risk), or two or less (high-risk) adverse features, respectively (p<0.0001). The independent prognostic value of monocytosis was validated in a separate database of 97 patients with PMF from another institution.

Cytogenetic and molecular aspects of Philadelphia negative chronic myeloproliferative disorders: clinical implications

Chronic myeloproliferative disorders (CMPD) are clonal disorders of the hematopoietic stem cell. The myeloid lineage shows increased proliferation with effective maturation, while peripheral leukocytosis, thrombocytosis or elevated red blood cell mass are found. In Philadelphia negative CMPD recurrent cytogenetic abnormalities occur, but no specific abnormality has been defined to date. The spectrum of cytogenetic aberrations is heterogeneous ranging from numerical gains and losses to structural changes including unbalanced translocations. The most common chromosomal abnormalities are 20q-, 13q-, 12p-, +8, +9, partial duplication of 1q, balanced translocations involving 8p11 and gains in 9p. Cytogenetic analysis of CMPD by conventional or molecular techniques has an important role in establishing the diagnosis of a malignant disease, adding also more information for disease outcome. Molecular studies may detect the possible role of candidate genes implicated in the neoplastic process, addressing new molecular target therapies. FIP1L1/PDGFRalpha rearrangements, as well as alterations of PDGFRbeta or FGFR1 gene have been found to be associated with specific types of CMPD. Recently, a novel somatic mutation, JAK2V617F, has been reported in most of the polycthemia vera (PV) patients, as well as in a lower percentage in essential thrombocythemia (ET) or idiopathic myelofibrosis (IMF) patients. This finding represents the most important advance in understanding of the molecular mechanisms underlined the pathogenesis of CMPD, contributing to the classification and management of patients.

Experimental therapy in myelofibrosis with myeloid metaplasia

Myelofibrosis with myeloid metaplasia (MMM) is a Philadelphia chromosome-negative myeloproliferative disorder that is characterised by constitutional symptoms, progressive anaemia and extramedullary haematopoiesis. There are no curative therapies available for patients with MMM apart from stem cell transplantation, which is associated with significant morbidity and mortality, and for which most patients are not suitable candidates. Traditional pharmacological therapy of MMM has focused on the palliation of symptoms associated with myeloproliferation and correction of cytopoenias. Recently, new findings regarding the molecular basis of MMM and the pathogenesis of the associated bone marrow stromal reaction have provided both basic and clinical researchers with invaluable tools to develop effective targeted therapies for patients with MMM. Several novel treatment strategies are being investigated including antiangiogenic agents, signal transduction inhibitors, inhibitors of fibrogenesis and small-molecule inhibitors of the JAK2(V617F )mutation. This article reviews the current status of experimental novel therapies for MMM.

Cytogenetics of agnogenic myeloid metaplasia: a study of 61 patients

Agnogenic myeloid metaplasia (AMM) or idiopathic myelofibrosis is a chronic myeloproliferative disorder characterized by fibrotic bone marrow, extramedullar haematopoiesis, and a leukoerythroblastic picture in circulating blood. The cytogenetic data on AMM are scanty and no recurring chromosome abnormality has been associated with the natural course of this disease. Trisomy 1q, del(13q), del(20q), and trisomy 8, appear in about two thirds of patients with demonstrable chromosome aberrations. We report on the cytogenetic analyses of 61 consecutive patients with AMM studied at diagnosis. The metaphases could not be found in 10/61 (16.4%) patients, and chromosome studies were successful in 51 patients. Twenty-one patients (41%) had an abnormal clone, whereas 30 (59%) patients had a normal karyotype. Most frequent pathological findings included trisomy 8 (either alone or within a complex karyotype) in five patients, aberrations of chromosome 12 (translocation in two, monosomy in two, and trisomy in one patient), and aberrations of chromosome 20 (interstitial deletion in two, monosomy in two, and trisomy in one patient). We also detected aberrations of chromosome 13 (translocation in two and an interstitial deletion and trisomy in one patient each) and chromosome 18 (derivative 18 in two patients and a monosomy and deletion in one patient each). Three patients exhibited complex aberrations involving several chromosomes, sometimes with a mosaicisam. A near-tetraploid karyotype was observed in a single patient. Balanced translocations [t(2;16)(q31;q24), t(5;13)(q13;q32), t(12;13)(p12;q13), and t(12;16)(q24;q24)] were present in four patients. While the series of patients studied displayed chromosomal aberrations that are frequently observed in AMM, we found some new abnormalities (balanced translocations and polyploidy) that are rarely observed in AMM.

Epigenetic alterations complement mutation of JAK2 tyrosine kinase in patients with BCR/ABL-negative myeloproliferative disorders

An acquired autoactivating mutation with a V617F amino-acid substitution in the JAK2 tyrosine kinase is frequently found in BCR/ABL-negative myeloproliferative disorders (MPD). Hypermethylation of CpG islands within gene promoter regions is associated with transcriptional inactivation and represents an important mechanism of gene silencing in the pathogenesis of hematopoietic malignancies. In this study, we determined the DNA methylation status of 13 cancer-related genes in the context of JAK2 mutations in 39 patients with MPD. Genes analyzed for hypermethylation were SOCS-1, SHP-1, E-cadherin, MGMT, TIMP-2, TIMP-3, p15, p16, p73, DAPK1, RASSF1A, RARbeta2 and hMLH1. We found at least one hypermethylated gene in 15/39 MPD patient specimens, and in 6/39 samples aberrant methylation of the negative cytokine regulator SOCS-1 was present. The JAK2V617F mutation was found in 21/39 patients as determined by allele-specific polymerase chain reaction. Hypermethylation of SOCS-1 was observed in 3/21 patients with an autoactivating JAK2 mutation and in 3/18 patients with wild-type JAK2. Our results suggest that epigenetic inactivation of SOCS-1 may be a complementary mechanism to the JAK2V617F mutation in the pathogenesis of MPD that leads to dysregulation of JAK-STAT signal transduction and thus contributes to growth factor hypersensitivity.

Validation and comparison of contemporary prognostic models in primary myelofibrosis

BACKGROUND

Survival in primary myelofibrosis (PMF) is predicted by several prognostic scoring systems (PSSs); the most widely recognized is that of Dupriez. Two other PSSs, Cervantes and Mayo, were recently reported as being more useful in younger patients. The current study compares these 3 PSSs among all age groups.

METHODS

The Mayo Clinic PMF database was queried to identify a consecutive series of patients in whom pretreatment bone marrow and complete blood count (CBC), obtained within 6 months of diagnosis, were available for review.

RESULTS

Among 334 study patients (median age, 57 years), median survival was 70 months. Multivariable analysis of all 6 adverse prognostic factors utilized in the aforementioned PSSs (ie, hemoglobin <10 g/dL, leukocyte count <4 or >30 x 10(9)/L, constitutional symptoms, circulating blasts > or = 1%, platelet count <100 x 10(9)/L, absolute monocyte count > or = 1 x 10(9)/L) identified all but platelet count as being significant. The Mayo PSS, which is based on the 4 CBC-derived parameters (ie, hemoglobin, platelet, leukocyte, and monocyte counts), displayed a better hazard ratio profile compared with the other 2 PSSs in identifying long-lived patients as well as delineating intermediate-risk disease category. The latter effect was even more pronounced in patients younger than age 60 years.

CONCLUSIONS

The Mayo PSS for survival in PMF is an objective CBC-derived prognostic model that might be superior in its performance over that of either the Dupriez and Cervantes PSSs.

New insights into the pathogenesis and drug treatment of myelofibrosis

PURPOSE OF REVIEW

Myelofibrosis with myeloid metaplasia was first described in 1879, classified as a myeloproliferative disorder in 1951, and characterized as a clonal stem cell disorder in 1978. Despite the passing of time, the molecular basis of the disease has remained elusive although substantial progress has been made regarding the pathogenesis of the associated bone marrow stromal reaction. Advances have also been meager in terms of treatment for disease complications, including anemia, splenomegaly, and leukemic transformation.

RECENT FINDINGS

At the molecular level, a JAK2 tyrosine kinase mutation (JAK2) has recently been described in a spectrum of myeloproliferative disorders including myelofibrosis with myeloid metaplasia with the reported mutational frequency ranging from 35% to 57% with 9-29% homozygosity. To date, the presence of JAK2 in myelofibrosis with myeloid metaplasia has not been shown to have prognostic relevance. Other recent observations of potential pathogenetic relevance in this disease include the description of a highly specific chromosomal translocation {der(6)t(1;6)(q23;p21)}, the demonstration of an epigenetic downregulation of the retinoic acid receptor-beta2 expression in CD34 cells, and the direct implication of transforming growth factor-beta1 in thrombopoietin-driven experimental myelofibrosis in mice. From a therapeutic standpoint, benefit to a subset of patients has been demonstrated for both allogeneic stem cell transplantation and novel drugs, including thalidomide and lenalidomide.

SUMMARY

Recent advances in the pathogenesis of myelofibrosis with myeloid metaplasia are expected to facilitate the development of molecularly targeted therapy. In the mean time, current management strategies include observation, participation in experimental drug therapy, and allogeneic stem cell transplantation for low-risk, intermediate-risk, and high-risk disease, 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.

Allogeneic stem cell transplantation as treatment for myelofibrosis

Idiopathic myelofibrosis (IMF) is a clonal disorder resulting from the proliferation of aberrant hematopoietic stem cells. Conventional treatment is unsatisfactory, and with the exception of supportive blood transfusions, none of the standard therapies have been shown to confer a survival advantage. Allogeneic stem cell transplantation represents the only treatment modality with proven curative potential. Myeloablative conditioning regimens are associated with high transplant-related mortality, particularly in the elderly, making most patients with IMF ineligible for this treatment. Strategies using reduced intensity conditioning regimes have allowed application of allogeneic transplantation to a broader range of patients and a number of recent reports have demonstrated potential efficacy.

Presence of unfavorable cytogenetic abnormalities is the strongest predictor of poor survival in secondary myelofibrosis

BACKGROUND

Postpolycythemic (PV) and postthrombocythemic (ET) myeloid metaplasia are consensually referred to as secondary myelofibrosis (sMF). Prognostic variables in sMF are not as well defined as they are for de novo myelofibrosis with myeloid metaplasia (MMM), which is also known as agnogenic myeloid metaplasia (AMM). Such information is particularly crucial for management decisions in transplant-eligible patients.

METHODS

Diagnoses of PV and ET required fulfillment of the World Health Organization criteria for the diagnosis of MMM as well as an antecedent history of either polycythemia vera or essential thrombocythemia that was supported by bone marrow examination. Cytogenetic findings were classified as being either favorable (normal or isolated 13q- or 20q- clones) or unfavorable (presence of abnormalities other than 13q- and 20q-).

RESULTS

The study population was comprised of 66 young patients (age <60 yrs) with sMF, including 37 patients with PV and 29 patients with ET. Multivariate analysis of parameters other than cytogenetics identified older age (P = .02), anemia (hemoglobin level <10 g/dL [P = .007]), and PV (P = .009) to be independent risk factors for shortened survival. However, when such analysis was restricted to patients in whom cytogenetic studies were performed (n = 31 patients), the presence of unfavorable cytogenetic abnormalities (i.e., clones other than 20q- and 13q-) became the only adverse prognostic factor for survival (P = .001). A similar analysis in a temporal cohort of 50 age-matched patients with AMM also identified unfavorable cytogenetics as an independent predictor of poor survival, along with thrombocytopenia and anemia.

CONCLUSIONS

The results of the current study suggest that cytogenetic findings might supersede AMM-derived prognostic scoring systems for predicting survival in patients with sMF.

Respective clustering of unfavorable and favorable cytogenetic clones in myelofibrosis with myeloid metaplasia with homozygosity for JAK2(V617F) and response to erythropoietin therapy

BACKGROUND

Patients who have myelofibrosis with myeloid metaplasia (MMM) display recurrent, albeit nonspecific cytogenetic abnormalities that are diverse prognostically. For the current study, the authors explored the relation between specific cytogenetic clones and JAK2(V617F) mutational status in patients with MMM and the effects on treatment response to erythropoietin (Epo).

METHODS

Concomitantly collected blood granulocytes and bone marrow were processed for JAK2(V617F) mutation analysis and cytogenetic studies, respectively. Genomic DNA was amplified by polymerase chain reaction, and fluorescent dye chemistry sequencing was performed by using the same primers that were used for amplification.

RESULTS

Among 105 study patients, cytogenetic abnormalities were detected in 47 patients (45%), and the JAK2(V617F) mutation was detected in 52 patients (50%). Comparison of mutational frequencies between favorable (normal, sole 13q-, or 20q- clones; n = 70 patients) and unfavorable (all other abnormalities; n = 35 patients) cytogenetic categories revealed a significantly different incidence of homozygous JAK2(V617F) between them (9% vs. 23%, respectively; P = .04). Furthermore, the mutant allele coexisted with several recurrent cytogenetic lesions. Among 25 patients who received Epo either alone (n = 17 patients) or in combination with hydroxyurea (n = 8 patients), 4 patients (16%) achieved a response, and none of them were homozygous for JAK2(V617F). Conversely, a response was more likely (P = .0001) in the presence of favorable cytogenetic abnormalities (i.e., 3 of 4 responders carried sole 13q- or 20q- clones).

CONCLUSIONS

Unfavorable and favorable cytogenetic clones in MMM clustered with homozygosity for JAK2(V617F) and treatment response to Epo-based therapy, respectively.

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.

Prognostic relevance of cytogenetics determined by fluorescent in situ hybridization in patients having myelofibrosis with myeloid metaplasia

BACKGROUND

In chronic myelofibrosis (MF), distinct recurrent cytogenetic aberrations have been identified but their true prognostic relevance remains uncertain. In this disease, cytogenetic studies as assessed by conventional metaphase karyotyping are limited due to the inherent difficulties in obtaining adequate bone marrow aspirates and the low proliferative capacity of the clonal cells. Interphase fluorescent in situ hybridization (FISH) can partly overcome these limitations and increase the sensitivity of cytogenetic assessment in MF.

METHODS

We retrospectively analyzed formalin-fixed, paraffin embedded bone marrow sections of 107 MF patients by FISH and correlated cytogenetic findings with clinical presentation and survival.

RESULTS

Chromosomal aberrations were detected in 56% of patients, with 20q- (24.3%) and 13q- (16.8%) being the most frequent ones. Importantly, cytogenetic abnormalities were found in 8/17 patients displaying a normal karyotype as assessed by conventional cytogenetics.

CONCLUSIONS

Cytogenetic abnormalities in patients with MF can be detected reliably using FISH. Rare abnormalities confer an adverse outcome, but the main recurrent chromosomal aberrations do not correlate with clinical features and prognosis.