Alessandro Pancrazzi

Mutations and prognosis in primary myelofibrosis

Patient outcome in primary myelofibrosis (PMF) is significantly influenced by karyotype. We studied 879 PMF patients to determine the individual and combinatorial prognostic relevance of somatic mutations. Analysis was performed in 483 European patients and the seminal observations were validated in 396 Mayo Clinic patients. Samples from the European cohort, collected at time of diagnosis, were analyzed for mutations in ASXL1, SRSF2, EZH2, TET2, DNMT3A, CBL, IDH1, IDH2, MPL and JAK2. Of these, ASXL1, SRSF2 and EZH2 mutations inter-independently predicted shortened survival. However, only ASXL1 mutations (HR: 2.02; P<0.001) remained significant in the context of the International Prognostic Scoring System (IPSS). These observations were validated in the Mayo Clinic cohort where mutation and survival analyses were performed from time of referral. ASXL1, SRSF2 and EZH2 mutations were independently associated with poor survival, but only ASXL1 mutations held their prognostic relevance (HR: 1.4; P=0.04) independent of the Dynamic IPSS (DIPSS)-plus model, which incorporates cytogenetic risk. In the European cohort, leukemia-free survival was negatively affected by IDH1/2, SRSF2 and ASXL1 mutations and in the Mayo cohort by IDH1 and SRSF2 mutations. Mutational profiling for ASXL1, EZH2, SRSF2 and IDH identifies PMF patients who are at risk for premature death or leukemic transformation.

Prospective identification of high-risk polycythemia vera patients based on JAK2(V617F) allele burden.

The aim of this study was to determine whether the burden of JAK2V617F allele correlated with major clinical outcomes in patients with polycythemia vera (PV). To this end, we determined JAK2 mutant allele levels in granulocytes of 173 PV patients at diagnosis. The mean (±s.d.) mutant allele burden was 52% (±29); 32 patients (18%) had greater than 75% mutant allele. The burden of JAK2V617F allele correlated with measurements of stimulated erythropoiesis (higher hematocrit, lower mean cell volume, serum ferritin and erythropoietin levels) and myelopoiesis (higher white cell count, neutrophil count and serum lactate dehydrogenase) and with markers of neutrophil activation (elevated leukocyte alkaline phosphatase and PRV-1 expression). As compared to those with less than 25% mutant allele, patients harboring greater than 75% JAK2V617F allele were at higher relative risk (RR) of presenting larger spleen (RR 4.7; P<0.001) or suffering from pruritus (RR 3.1; P<0.001). In these patients, the risk of requiring chemotherapy (RR 1.8; P=0.001) or developing major cardiovascular events (RR 7.1; P=0.003) during follow up were significantly increased. We conclude that a burden of JAK2V617F allele greater than 75% at diagnosis points to PV patients with high-risk disease.

Impact of calreticulin mutations on clinical and hematological phenotype and outcome in essential thrombocythemia.

Mutations in the calreticulin (CALR) gene were recently discovered in patients with essential thrombocythemia (ET) lacking the JAK2V617F and MPLW515 mutations, but no information is available on the clinical correlates. In this series, CALR mutations were found in 15.5% of 576 World Health Organization-defined ET patients, accounting for 48.9% of JAK2 and MPL wild-type (wt) patients. CALR-mutated patients were preferentially male and showed higher platelet count and lower hemoglobin and leukocyte count compared with JAK2- and MPL-mutated patients. Patients carrying the CALR mutation had a lower risk of thrombosis than JAK2- and MPL-mutated patients; of interest, their risk was superimposable to patients who were wt for the above mutations. CALR mutation had no impact on survival or transformation to post-ET myelofibrosis. Genotyping for CALR mutations represents a novel useful tool for establishing a clonal myeloproliferative disorder in JAK2 and MPL wt patients with thrombocytosis and may have prognostic and therapeutic relevance.

Clinical implications of the JAK2 V617F mutation in essential thrombocythemia.

istic upmodulation of CD20 and downmodulation of CD10, comparable to the immunophenotypic modulation observed in vivo. In contrast, the viable 7-AAD-negative cells retained their original immunophenotype (Figure 2e, f). For each antibody, the MFI differed between the viable and dead cells, but within these two populations the MFI was not affected by the type and dose of the cytotoxic agents to which the cells were exposed (data not shown). Further analysis of dead and viable cells showed that dead cells had a higher MFI for each isotype control antibody than viable cells. This increase in background staining was comparable to the upmodulation of CD20 on CD20-negative leukemic cells observed in day 15 and 28 samples. Altogether, these data indicate that the immunophenotypic modulation observed in vitro is due to the induction of cell kill, resulting in a higher aspecific staining and a decreased expression of membrane antigens. Our data suggest that in ALL patients undergoing treatment, immunophenotypic modulation is caused by drug-induced cell death, resulting in loss of membrane antigens and higher aspecific staining. Our data are in agreement with a recent study, which showed that the loss of expression of lineage antigens (such as CD19) is a common feature of lymphocytes undergoing apoptosis and that the MFI for different antigens might drop to undetectable levels during different stages of apoptosis. Antigens coexpressed on the same cells showed different degrees of loss in the different stages of apoptosis, suggesting that it is a specific, active process, rather than a general degradation of cell components. Our observation that immunophenotypic modulation is due to apoptotic cells also explains why ALL blast cells in resistant patients show no modulation. In conclusion, our data indicate that immunophenotypic modulation in ALL patients undergoing treatment can (at least in part) be explained by the induction of cell death. As the presence of these dying cells may still be clinically relevant, usage of strict gating procedures, based on the exact immunophenotype of the blast cells at diagnosis, should be avoided for the analysis of MRD.

Characteristics and clinical correlates of MPL 515W>L/K mutation in essential thrombocythemia.

Among 994 patients with essential thrombocythemia (ET) who were genotyped for the MPLW515L/K mutation, 30 patients carrying the mutation were identified (3.0%), 8 of whom also displayed the JAK2V671F mutation. MPLW515L/K patients presented lower hemoglobin levels and higher platelet counts than did wild type (wt) MPL; these differences were highly significant compared with MPLwt/JAK2V617F-positive patients. Reduced hemoglobin and increased platelet levels were preferentially associated with the W515L and W515K alleles, respectively. MPL mutation was a significant risk factor for microvessel disturbances, suggesting platelet hyperreactivity associated with constitutively active MPL; arterial thromboses were increased only in comparison to MPLwt/JAK2wt patients. MPLW515L/K patients presented reduced total and erythroid bone marrow cellularity, whereas the numbers of megakaryocytes, megakaryocytic clusters, and small-sized megakaryocytes were all significantly increased. These data indicate that MPLW515L/K mutations do not define a distinct phenotype in ET, although some differences depended on the JAK2V617F mutational status of the counterpart.

Identification of patients with poorer survival in primary myelofibrosis based on the burden of JAK2V617F mutated allele.

A total of 186 patients with primary myelofibrosis (PMF) were genotyped for JAK2V617F at diagnosis aimed at analyzing the correlation of mutational status and mutated allele burden with outcome variables, including time to anemia, leukocytosis, leukopenia, thrombocytopenia, massive splenomegaly, leukemia, and with overall survival. A total of 127 JAK2V617F-mutated patients (68% of whole series) were divided in quartiles of V617F allele burden. After a median follow-up of 17.2 months, 23 patients died, 15 because of leukemia. A JAK2V617F mutated status did not impact on the rate of leukemia transformation or overall survival. Patients in the lower quartile had shorter time to anemia and leukopenia and did not progress to large splenomegaly. Furthermore, survival was significantly reduced in the lower quartile compared with upper quartiles and JAK2 wild-type patients. In multivariate analysis, factors associated with reduced survival were age, a blast count more than 1%, and a JAK2V617F burden within first quartile. Causes of death in the lower quartile were represented mainly by systemic infections. We conclude that a low JAK2V617F allele burden at diagnosis is preferentially associated with a myelodepletive rather than myeloproliferative phenotype and represents an independent factor associated with shortened survival in patients with PMF.

Anaemia characterises patients with myelofibrosis harbouring MplW515L/K mutation

The clinical and haematological phenotype of patients with myelofibrosis harbouring MPLW515L/K mutation has not been thoroughly investigated. Of 217 myelofibrosis subjects, 18 (8·2%) had an MPL mutation, four of which (22%) co‐existed with JAK2V617F mutation. When compared with MPL wild‐type patients, irrespective of JAK2V617F status, those with MPLW515L/K, were more frequently female, were older (61 years vs. 57 years; P = 0·02), presented with more severe anaemia (haemoglobin, 101 g/l vs. 121 g/l; P = 0·002) and were more likely to require regular transfusional support (P = 0·012). These data indicate that MPL mutation in myelofibrosis characterises patients with more severe anaemic phenotype.

Influence of JAK2V617F allele burden on phenotype in essential thrombocythemia.

Variable proportions of mutant alleles are found in patients with JAK2 (V617F)-positive myeloproliferative disorders. This study shows that this variable mutant allele burden influences the clinical phenotype of JAK2 (V617F)-positive essential thrombocythemia. Background Fifty to sixty percent of patients with essential thrombocythemia harbor the JAK2V617F mutation. The impact of this mutation on clinical phenotype is still debated. The aim of this study was to evaluate possible correlations between JAK2V617F mutant allele burden and both clinical presentation and hematologic abnormalities in essential thrombocythemia patients. Design and Methods In this single-center retrospective study, JAK2V617F allele load was measured by sensitive quantitative reverse transcriptase polymerase chain reaction (RT-PCR) in the granulocytes of 260 patients diagnosed as having essential thrombocythemia according to WHO criteria. Results Median V617F allele burden in patients with the mutation (n=165, 63.4%) was 24%, ranging from 1% to 87%; an allele burden greater than 51% was found in 5% of the patients. Older patients presented progressively higher percentages of the V617F allele. Signs of stimulated erythropoiesis and myelopoiesis, as well as higher PRV-1 levels, were found in patients with the mutation, but no linear correlation with load of mutant allele could be ascertained; on the other hand, the frequency of patients with erythropoietin-independent erythroid colonies progressively increased depending on mutant allele load. Splenomegaly and microvessel symptoms were significantly more represented among patients with greater than 50% and 25% JAK2V617F allele burden, respectively. Increasing mutant allele load correlated with higher frequency of arterial thrombosis at diagnosis, as confirmed also in multivariate analysis; the relative risk was 3.0 (95% CI 1.3–6.8; p=0.01) in patients having a greater than 25% mutant allele burden. Conclusions The JAK2V617F mutant allele burden contributes to determining the clinical phenotype in patients with essential thrombocythemia.

The number of prognostically detrimental mutations and prognosis in primary myelofibrosis: an international study of 797 patients

We recently defined a high-molecular risk category (HMR) in primary myelofibrosis (PMF), based on the presence of at least one of the five ‘prognostically detrimental’ mutated genes (ASXL1, EZH2, SRSF2 and IDH1/2). Herein, we evaluate the additional prognostic value of the ‘number’ of mutated genes. A total of 797 patients were recruited from Europe (n=537) and the Mayo Clinic (n=260). In the European cohort, 167 (31%) patients were HMR: 127 (23.6%) had one and 40 (7.4%) had two or more mutated genes. The presence of two or more mutations predicted the worst survival: median 2.6 years (hazard ratio (HR) 3.8, 95% confidence interval (CI) 2.6–5.7) vs 7.0 years (HR 1.9, 95% CI 1.4–2.6) for one mutation vs 12.3 years for no mutations. The results were validated in the Mayo cohort and prognostic significance in both cohorts was independent of International Prognostic Scoring System (IPSS; HR 2.4, 95% CI 1.6–3.6) and dynamic IPSS (DIPSS)-plus (HR 1.9, 95% CI 1.2–3.1), respectively. Two or more mutations were also associated with shortened leukemia-free survival (HR 6.2, 95% CI 3.5–10.7), also Mayo validated. Calreticulin mutations favorably affected survival, independently of both number of mutations and IPSS/DIPSS-plus. We conclude that the ‘number’ of prognostically detrimental mutations provides added value in the combined molecular and clinical prognostication of PMF.

Safety and efficacy of everolimus, a mTOR inhibitor, as single agent in a phase 1/2 study in patients with myelofibrosis

In addition to dysregulated JAK/STAT signaling, activation of the AKT/mTOR pathway occurs in myelofibrosis, a myeloproliferative neoplasm with no approved therapies. We conducted a phase 1/2 study with everolimus, an mTOR inhibitor, in 39 high- or intermediate-risk primary or postpolycythemia vera/postessential thrombocythemia myelofibrosis subjects. Responses were evaluated in 30 patients of phase 2. No dose-limiting toxicity was observed in phase 1 up to 10 mg/d. When this dose was used in phase 2, grade ≥ 3 toxicities were infrequent; the commonest toxicity was grade 1-2 stomatitis. Rapid and sustained splenomegaly reduction of > 50% and > 30% occurred in 20% and 44% of subjects, respectively. A total of 69% and 80% experienced complete resolution of systemic symptoms and pruritus. Response in leukocytosis, anemia, and thrombocytosis occurred in 15%-25%. Clinical responses were not associated with reduced JAK2V617F burden, circulating CD34(+) cells, or cytokine levels, whereas CCDN1 mRNA and phospho-p70S6K level, known targets of mTOR, and WT1 mRNA were identified as possible biomarkers associated with response. Response rate was 60% when European Network for Myelofibrosis criteria were used (8 major, 7 moderate, 3 minor responses) or 23% when IWG-MRT criteria (1 partial response, 6 clinical improvements) were used. These results provide proof-of-concept that targeting mTOR pathway in myelofibrosis may be clinically relevant.