ASXL1 and SETBP1 mutations and their prognostic contribution in chronic myelomonocytic leukemia: a two-center study of 466 patients

In a cohort of 466 patients, we sought to clarify the prognostic relevance of ASXL1 and SETBP1 mutations, among others, in World Health Organization-defined chronic myelomonocytic leukemia (CMML) and its added value to the Mayo prognostic model. In univariate analysis, survival was adversely affected by ASXL1 (nonsense and frameshift) but not SETBP1 mutations. In multivariable analysis, ASXL1 mutations, absolute monocyte count >10 × 10(9)/l, hemoglobin <10 g/dl, platelets <100 × 10(9)/l and circulating immature myeloid cells were independently predictive of shortened survival: hazard ratio (95% confidence interval (CI)) values were 1.5 (1.1-2.0), 2.2 (1.6-3.1), 2.0 (1.6-2.6), 1.5 (1.2-1.9) and 2.0 (1.4-2.7), respectively. A regression coefficient-based prognostic model based on these five risk factors delineated high (≥3 risk factors; HR 6.2, 95% CI 3.7-10.4) intermediate-2 (2 risk factors; HR 3.4, 95% CI 2.0-5.6) intermediate-1 (one risk factor; HR 1.9, 95% CI 1.1-3.3) and low (no risk factors) risk categories with median survivals of 16, 31, 59 and 97 months, respectively. Neither ASXL1 nor SETBP1 mutations predicted leukemic transformation. The current study confirms the independent prognostic value of nonsense/frameshift ASXL1 mutations in CMML and signifies its added value to the Mayo prognostic model, as had been shown previously in the French consortium model.

CALR vs JAK2 vs MPL-mutated or triple-negative myelofibrosis: clinical, cytogenetic and molecular comparisons

Calreticulin (CALR) mutations were recently described in JAK2 and MPL unmutated primary myelofibrosis (PMF) and essential thrombocythemia. In the current study, we compared the clinical, cytogenetic and molecular features of patients with PMF with or without CALR, JAK2 or MPL mutations. Among 254 study patients, 147 (58%) harbored JAK2, 63 (25%) CALR and 21 (8.3%) MPL mutations; 22 (8.7%) patients were negative for all three mutations, whereas one patient expressed both JAK2 and CALR mutations. Study patients were also screened for ASXL1 (31%), EZH2 (6%), IDH (4%), SRSF2 (12%), SF3B1 (7%) and U2AF1 (16%) mutations. In univariate analysis, CALR mutations were associated with younger age (P<0.0001), higher platelet count (P<0.0001) and lower DIPSS-plus score (P=0.02). CALR-mutated patients were also less likely to be anemic, require transfusions or display leukocytosis. Spliceosome mutations were infrequent (P=0.0001) in CALR-mutated patients, but no other molecular or cytogenetic associations were evident. In multivariable analysis, CALR mutations had a favorable impact on survival that was independent of both DIPSS-plus risk and ASXL1 mutation status (P=0.001; HR 3.4 for triple-negative and 2.2 for JAK2-mutated). Triple-negative patients also displayed inferior LFS (P=0.003). The current study identifies 'CALR(-)ASXL1(+)' and 'triple-negative' as high-risk molecular signatures in PMF.

Mayo prognostic model for WHO-defined chronic myelomonocytic leukemia: ASXL1 and spliceosome component mutations and outcomes

We evaluated the prognostic relevance of several clinical and laboratory parameters in 226 Mayo Clinic patients with chronic myelomonocytic leukemia (CMML): 152 (67%) males and median age 71 years. At a median follow-up of 15 months, 166 (73%) deaths and 33 (14.5%) leukemic transformations were documented. In univariate analysis, significant risk factors for survival included anemia, thrombocytopenia, increased levels of white blood cells, absolute neutrophils, absolute monocyte count (AMC), absolute lymphocytes, peripheral blood and bone marrow blasts, and presence of circulating immature myeloid cells (IMCs). Spliceosome component (P=0.4) and ASXL1 mutations (P=0.37) had no impact survival. On multivariable analysis, increased AMC (>10 × 10(9)/l, relative risk (RR) 2.5, 95% confidence interval (CI) 1.7-3.8), presence of circulating IMC (RR 2.0, 95% CI 1.4-2.7), decreased hemoglobin (<10 g/dl, RR 1.6, 99% CI 1.2-2.2) and decreased platelet count (<100 × 10(9)/l, RR 1.4, 99% CI 1.0-1.9) remained significant. Using these four risk factors, a new prognostic model for overall (high risk, RR 4.4, 95% CI 2.9-6.7; intermediate risk, RR 2.0, 95% CI 1.4-2.9) and leukemia-free survival (high risk, RR 4.9, 95% CI 1.9-12.8; intermediate risk, RR 2.6, 95% CI 1.1-5.9) performed better than other conventional risk models and was validated in an independent cohort of 268 CMML patients.

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.

CSF3R T618I is a highly prevalent and specific mutation in chronic neutrophilic leukemia

Truncation mutations of the receptor cytoplasmic domain for colony-stimulating factor 3 (CSF3R) are frequently seen in severe congenital neutropenia, whereas activating missense mutations affecting the extracellular domain (exon 14) have been described in hereditary neutrophilia and chronic neutrophilic leukemia (CNL). In order to clarify mutational frequency, specificity and phenotypic associations, we sequenced CSF3R exons 14-17 in 54 clinically suspected cases of CNL (n=35) or atypical chronic myeloid leukemia (aCML; n=19). Central review of these cases confirmed WHO-defined CNL in 12 patients, monoclonal gammopathy (MG)-associated CNL in 5 and WHO-defined aCML in 9. A total of 14 CSF3R mutations were detected in 13 patients, including 10 with CSF3RT618I (exon 14 mutation, sometimes annotated as CSF3R T595I). CSF3RT618I occurred exclusively in WHO-defined CNL with a mutational frequency of 83% (10 of 12 cases). CSF3R mutations were not seen in aCML or MG-associated CNL. CSF3RT618I was also absent among 170 patients with primary myelofibrosis (PMF; n=76) or chronic myelomonocytic leukemia (CMML; n=94). SETBP1 mutational frequencies in WHO-defined CNL, aCML, CMML and PMF were 33, 0, 7 and 3%, respectively. Four CSF3RT618I-mutated cases co-expressed SETBP1 mutations. We conclude that CSF3RT618I is a highly sensitive and specific molecular marker for CNL and should be incorporated into current diagnostic criteria.

Clinical correlates of JAK2V617F allele burden in essential thrombocythemia

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Background: JAK2V617F occurs in approximately 50% of patients with essential thrombocythemia. Qualitative studies of mutation analysis have previously reported an association between JAK2V617F and advanced age, higher hemoglobin level, higher leukocyte count, and lower platelet count. A possible association with thrombotic complication has also been considered. Methods: Allele-specific, quantitative PCR analysis for JAK2V617F was performed on 176 patients with ET, using genomic DNA from archived bone marrow, which was collected within one year (n=72), between 1 and 5 years (n=64), or after 5 years (n=40) of diagnosis. Results: JAK2V617F was detected in 96 patients (55%), in whom mutant allele burden ranged from 1% to 100% (median 6.3%). Neither mutational frequency (p=0.37) nor mutant allele burden (p=0.62) was affected by the timing of bone marrow sample collection. Presence of JAK2V617F was significantly associated with higher hemoglobin level (p<0.0001), lower platelet count (p=0.001), higher leukocyte count (p=0.008), increased incidence of venous thrombosis occurring after diagnosis (p=0.02), and older age at diagnosis (p=0.03). All but age retained significance in multivariable analysis. In mutation-positive patients (n=96), JAK2V617F allele burden clustered between 1% and 22% in 94 cases, in whom it correlated directly and significantly with platelet and leukocyte counts, palpable splenomegaly at diagnosis, and venous thrombosis occurring after diagnosis. Conclusions: JAK2V617F allele burden imparts additional phenotypic effects in ET.

No significant financial relationships to disclose.

Connective tissue dysplasia in five new patients with NF1 microdeletions: further expansion of phenotype and review of the literature

Approximately 5% of patients with neurofibromatosis type 1 (NF1) have deletions of the entire NF1 gene. The phenotype usually includes early onset, large number of neurofibromas, presence of congenital anomalies, cognitive deficiency, and variable dysmorphic features and growth abnormalities. Connective tissue abnormalities are not generally recognised as a part of NF1 microdeletion syndrome, but mitral valve prolapse, joint laxity, and/or soft skin on the palms have been reported in a few patients. We describe clinical findings in six newly diagnosed patients with NF1 microdeletions, five of whom presented with connective tissue abnormalities. A literature review of the clinical findings associated with NF1 microdeletion was also performed. Our report confirms that connective tissue dysplasia is common in patients with NF1 microdeletions. Given the potential for associated cardiac manifestation, screening by echocardiogram may be warranted. Despite the large number (>150) of patients with known NF1 microdeletions, the clinical phenotype remains incompletely defined. Additional reports of patients with NF1 microdeletions, including comprehensive clinical and molecular information, are needed to elucidate possible genotype-phenotype correlation.

Development of a D-FISH method to detect DEK/CAN fusion resulting from t(6;9)(p23;q34) in patients with acute myelogenous leukemia

The t(6;9)(p23;q34)-DEK/CAN fusion occurs with an incidence of 1-5% in adult patients with acute myelogenous leukemia (AML) and tends to have an unfavorable prognosis at diagnosis. Due to the subtle appearance of this chromosome rearrangement, both initial detection and minimal residual disease (MRD) tracking by conventional karyotyping can be difficult. Unfortunately, no commercial or previously published fluorescence in situ hybridization (FISH) strategies exist for this recurrent anomaly. We have developed a highly sensitive assay using dual-color, double-fusion FISH (D-FISH), which can be used both for initial detection and MRD monitoring. We analyzed archived bone marrow samples from 15 patients with a previously identified t(6;9)(p23;q34) and 10 corresponding post-treatment samples. The results demonstrate that our D-FISH method effectively identified all abnormal samples, including a low-level MRD sample that was considered to be normal by conventional cytogenetic analysis. Normal value ranges were established from 30 negative controls to be < 0.6% when 500 interphase nuclei were analyzed. The development of this sensitive D-FISH strategy for the detection of the t(6;9)(p23;q34) adds to the AML FISH testing repertoire, and is effective in the detection of low-level disease in post-treatment samples in these patients.

Centrifuge polarizing microscope. II. Sample biological applications

The rationale, design and general performance of the CPM (centrifuge polarizing microscope) were described in Part I of this study (Inoué et al. J. Microsc. 201 (2001) 341-356. In this second part, we describe observations on several biological samples that we have explored over the past two years using the CPM. As described in the first part of the study, although the CPM was basically designed as a high-extinction centrifuge polarizing microscope, it also allows observations of the specimen exposed to high centrifugal fields up to 10 500 x g (earth's gravitational acceleration) in fluorescence (532-nm excitation) and in DIC (differential interference or Nomarski contrast).

Centrifuge polarizing microscope. I. Rationale, design and instrument performance

We first describe early uses of the centrifuge for deciphering physical properties and molecular organization within living cells, as well as the development and use of centrifuge microscopes for such studies. The rationale for developing a centrifuge microscope that allows high-extinction polarized light microscopy to observe dynamic fine structures in living cells is next discussed. We then describe a centrifuge polarizing microscope (CPM) that we developed for observing fine structural changes in living cells which are being exposed to up to approximately 11 500 times earth's gravitational field (g). With the specimen housed in a rotor supported on an air spindle motor, and imaged through an external microscope illuminated by a precisely synchronized flash of less than 10 ns duration from a Nd:YAG laser, the image of the spinning object remains steady up to the maximum speed of 11 700 rev min-1, or up to approximately 11 500 x g. The image is captured, at up to 25 frames s-1, by an interference-fringe-free CCD camera that is synchronized to the centrifuge rotor. At all speeds (in 100 rev min-1 increments), the image is resolved to better than 1 microm, while birefringence of the specimen, housed in a specially designed specimen chamber that suffers low-stress birefringence and prevents leakage of the physiological solutions, is detected with a retardance sensitivity of better than 1 nm. Differential interference contrast and fluorescence images (532 nm excitation) of the spinning specimen can also be generated with the CPM. The second part of this study (Inoué et al., J. Microsc. 201 (2001) 357-367, describes several biological applications of the CPM that we have explored. Individual live cells, such as oocytes and blood cells, are supported on a sucrose or Percoll density gradient while other cells, such as cultured fibroblasts and Dictyostelium amoebae, are observed crawling on glass surfaces. Observations of these cells exposed to the high G fields (centripetal acceleration/g) in the CPM are yielding many new results that lead to intriguing questions regarding the organization and function of fine structures in living cells and related quasi-fluid systems.