Mutations of polycomb-associated gene ASXL1 in myelodysplastic syndromes and chronic myelomonocytic leukaemia

The myelodysplastic syndromes (MDSs) are a heterogeneous group of clonal haematological diseases characterized by ineffective haematopoiesis and predisposition to acute myeloid leukaemia (AML). The pathophysiology of MDSs remains unclear. A definition of the molecular biology of MDSs may lead to a better classification, new prognosis indicators and new treatments. We studied a series of 40 MDS/AML samples by high-density array-comparative genome hybridization (aCGH). The genome of MDSs displayed a few alterations that can point to candidate genes, which potentially regulate histone modifications and WNT pathways (e.g. ASXL1 , ASXL2 , UTX , CXXC4 , CXXC5 , TET2 , TET3 ). To validate some of these candidates we studied the sequence of ASXL1 . We found mutations in the ASXL1 gene in four out of 35 MDS patients (11%). To extend these results we searched for mutations of ASXL1 in a series of chronic myelomonocytic leukaemias, a disease classified as MDS/Myeloproliferative disorder, and found mutations in 17 out of 39 patients (43%). These results show that ASXL1 might play the role of a tumour suppressor in myeloid malignancies.     

Acute transformation of chronic myelomonocytic leukaemia: a multivariate study of predictive factors

In an attempt to determine the possible predictive value of the main clinical and haematological initial features of chronic myelomonocytic leukaemia (CMML) on the evolution to acute leukaemia, as well as the real impact of such an event on survival, 35 such patients were submitted to multiple regression analyses. At the time of the study 30 out of the 35 patients had died, with a median survival of 8.2 months for the whole series. 12 patients (34%) developed acute leukaemia, between 1.5 and 42.1 months from diagnosis of CMML, the actuarial median time of acute transformation being 29.4 months. The initial bone marrow blast cell percentage was the only factor influencing the development of acute leukaemia. On the other hand, the multivariate survival study showed that acute transformation introduced in the model as a time-dependent variable had a clear-cut unfavourable influence on the outcome of CMML patients, as did palpable spleen, advanced age and marked monocytosis.     

Successive transformation of chronic myelomonocytic leukaemia into acute myeloblastic then lymphoblastic leukaemia, both with minor-bcr rearrangement

We report a case of chronic myelomonocytic leukaemia (CMML), which transformed first into acute myeloblastic leukaemia (AML) and then into acute lymphoblastic leukaemia (ALL). In the AML and ALL phases, chromosome analysis showed a classic Philadelphia chromosome (Ph) t(9;22)(q34;q11). Molecular studies showed breakpoint cluster region rearrangement between exons e1 and a2 compatible with a p190^bcr/abl breakpoint as observed in Ph-positive lymphoblastic acute leukaemia. The minor (m-bcr) rearrangement was also detected during complete remission.
This observation supports a multistep pathogenesis of leukaemias, and that the p190^bcr/abl breakpoint may influence the course of the disease.     

TET2 gene mutation is a frequent and adverse event in chronic myelomonocytic leukemia

Background

Acquired somatic deletions and loss-of-function mutations in one or several codons of the TET2 (Ten-Eleven Translocation-2) gene were recently identified in hematopoietic cells from patients with myeloid malignancies, including myeloproliferative disorders and myelodys-plastic syndromes. The present study was designed to determine the prevalence of TET2 gene alterations in chronic myelomonocytic leukemias.

Design and Methods

Blood and bone marrow cells were collected from 88 patients with chronic phase chronic myelomonocytic leukemia and from 14 with acute transformation of a previously identified disease. Polymerase chain reaction analysis and direct sequencing were used to sequence exons 3 to 11 of the TET2 gene. Annotated single nucleotide polymorphisms were excluded. Survival curves were constructed by the Kaplan-Meier method.

Results

We detected TET2 mutations in 44 of 88 (50%) patients with chronic myelomonocytic leukemia, which suggests that TET2 gene mutations are especially frequent in this myeloid disease. A TET2 gene alteration was identified in 18 of the 43 patients studied at diagnosis and was associated with a trend to a lower overall survival rate; confining the analysis to the 29 patients with chronic myelomonocytic leukemia-1, according to the WHO classification, the difference in overall survival between patients with or without TET2 gene mutations became statistically significant.

Conclusions

TET2 gene alterations are more frequent in chronic myelomonocytic leukemia than in other subgroups of hematopoietic diseases studied so far and could negatively affect the patients’ outcome. The striking association between TET2 gene alterations and monocytosis, already observed in patients with systemic mastocytosis, could indicate a negative role of TET2 in the control of monocytic lineage determination.     

A three-gene leukaemic stem cell signature score is robustly prognostic in chronic myelomonocytic leukaemia

Leukaemic stem cell (LSC) gene expression has recently been linked to prognosis in patients with acute myeloid leukaemia (17-gene LSC score, LSC-17) and myelodysplastic syndromes. Although chronic myelomonocytic leukaemia (CMML) is regarded as a stem cell disorder, the clinical and biological impact of LSCs on CMML patients remains elusive. Making use of multiple independent validation cohorts, we here describe a concise three-gene expression signature (LSC-3, derived from the LSC-17 score) as an independent and robust prognostic factor for leukaemia-free and overall survival in CMML. We propose that LSC-3 could be used to supplement existing risk stratification systems, to improve prognostic performance and guide management decisions.     

Multiple myeloma and chronic myelomonocytic leukaemia developing in a patient with autoimmune disease

A 64-year-old lady with a personal and family history of autoimmune disease developed chronic myelomonocytic leukaemia and multiple myeloma simultaneously. Her sister died of acute myelomonocytic leukaemia, but showed no evidence of autoimmune disease. It is possible that chronic immunological stimulation, perhaps by an autoantigen, may predispose toward malignant transformation in both plasma cell and monocyte series. However, the present observations raise the alternative possibility of a primary disorder of monocytes that predisposes toward both autoimmune disease and a clonal disorder of plasma cells.     

Recent advances in diagnosis, molecular pathology and therapy of chronic myelomonocytic leukaemia

The clinical, morphological, and genetic heterogeneity of chronic myelomonocytic leukaemia (CMML), has made it difficult to clearly assign this entity to a distinct haematological category. In 2001, the World Health Organization transferred CMML to a new category of mixed myeloproliferative/myelodysplastic disorders, which was maintained in the last revision in 2008. Considering the rare occurrence of CMML, most pharmacotherapeutic and transplant studies combined CMML with myelodysplastic syndrome cases, but some clinical trials specifically investigated the use of demethylating agents in CMML and demonstrated stabilization of the haematological situation or even complete remission in subsets of patients. Information on the significance of other drugs is very limited. Allogeneic haematopoietic stem cell transplantation (HSCT) remains the only curative option for patients with CMML. Molecular studies revealed various novel genetic alterations in CMML - notably of the JAK2, TET2, CBL, IDH, or RUNX1 and RAS genes. This review summarizes the current status of pharmacotherapy and transplantation in CMML and outlines recent results of molecular research for diagnosis of this heterogeneous entity.     

Prognostic significance of ASXL1 mutations in myelodysplastic syndromes and chronic myelomonocytic leukemia: A meta-analysis

Objectives: Although additional sex comb-like 1 (ASXL1) gene mutations have long been reported in myelodysplastic syndromes (MDSs) and chronic myelomonocytic leukemia (CMML), the prognostic significance has been controversial. Therefore, a meta-analysis to study the impact of ASXL1 mutations on patients with MDS and CMML is useful.

Methods: The identified articles were retrieved from some common databases. We extracted hazard ratios (HRs) for overall survival (OS) and leukemic-free survival (LFS) and P-value of some clinical parameters, which compared AXSL1 mutations to those without from the available studies. Each individual HR and P-value was used to calculate the pooled HR and P-value.

Results: Six studies covering 1689 patients were selected for this meta-analysis. The pooled HRs for OS and LFS were 1.45 (95% confidential interval (CI), 1.24–1.70) and 2.20 (95% CI, 1.53–3.17), respectively. When considering CMML patients alone the HR for OS was 1.50 (95% CI, 1.18–1.90). Additionally, ASXL1 mutations were more frequently found in male (P?=?0.008), older (P?=?0.019), and patients with lower platelets (P?=?0.009) or hemoglobin level (P?=?0.0015) and associated with other mutations such as EZH2, IDH1/2, RUNX1, and TET2.

Discussion: Although our analysis has its limitation, it showed that ASXL1 mutations had significant inferior impact on OS and LFS for French–American–British-defined MDS patients. However, the influence of different types of ASXL1 mutations on patients with MDS still needs illustrating.

Conclusion: ASXL1 mutations were associated with poor prognosis in MDS, which may contribute to risk stratification and prognostic assessment in the disease.     

New prognostic markers, determined using gene expression analyses, reveal two distinct subtypes of chronic myelomonocytic leukaemia patients

Chronic myelomonocytic leukaemia (CMML) is a heterogeneous haematopoietic disorder characterized by myeloproliferative or myelodysplastic features. At present, the pathogenesis of this malignancy is not completely understood. In this study, we sought to analyse gene expression profiles of CMML in order to characterize new molecular outcome predictors. A learning set of 32 untreated CMML patients at diagnosis was available for TaqMan low-density array gene expression analysis. From 93 selected genes related to cancer and cell cycle, we built a five-gene prognostic index after multiplicity correction. Using this index, we characterized two categories of patients with distinct overall survival (94% vs. 19% for good and poor overall survival, respectively; P = 0·007) and we successfully validated its strength on an independent cohort of 21 CMML patients with Affymetrix gene expression data. We found no specific patterns of association with traditional prognostic stratification parameters in the learning cohort. However, the poor survival group strongly correlated with high-risk treated patients and transformation to acute myeloid leukaemia. We report here a new multigene prognostic index for CMML, independent of the gene expression measurement method, which could be used as a powerful tool to predict clinical outcome and help physicians to evaluate criteria for treatments.     

Bone marrow trephine morphology and immunohistochemical findings in chronic myelomonocytic leukaemia

Chronic myelomonocytic leukaemia (CMML) is a clonal disorder with myelodysplastic/myeloproliferative features. Its diagnosis is based on the presence of peripheral blood monocytosis and bone marrow aspirate findings, according to World Health Organization criteria. However, bone marrow trephine biopsy (BMTB) features characteristic of CMML have not been adequately investigated. We studied BMTB in 20 cases of CMML-1 and three cases of CMML-2 and compared with ten cases of polycythaemia vera, ten cases of chronic myeloid leukaemia (chronic phase) and ten cases of florid myeloid hyperplasia (MH). Furthermore, we evaluated the use of CD34, CD117 and CD68 (PGM-1) antibodies in diagnosis and subtyping of CMML and in differentiating from other categories. Hypercellularity, high myeloid:erythroid ratio, increased proportion of 'myelo/monocytic' cells often seen as clusters and/or nodules, absence of eosinophilia, and presence of abnormal localisation of immature precursors (ALIP) and dysmegakaryopoiesis can aid in the diagnosis of CMML in BMTB. CD68 (PGM-1) positive cells amounted to 20·7 ± 6·1% cells among CMML trephines. The proportion of CD34⁺ cells among cases of CMML-1 was ≤5% and among CMML-2 was ≥10% cells in two of three cases and 5% in the other case. Morphological and immunohistochemical features of BMTB samples are extremely helpful in the diagnosis of CMML.     

MYC translocation in chronic lymphocytic leukaemia is associated with increased prolymphocytes and a poor prognosis

Chromosomal translocations that involve MYC , characteristic of Burkitt lymphoma, are rare in chronic lymphocytic leukaemia (CLL). We report the clinical, morphological, immunophenotypic, cytogenetic and molecular genetic features of eight CLL cases with MYC rearrangement. The patients, five men and three women (median age, 71 years) had bone marrow involvement and an absolute peripheral blood lymphocytosis; five had lymphadenopathy; seven had splenomegaly. Prolymphocytes were increased (≥10%) in all cases. Six cases were classified as CLL with increased prolymphocytes (CLL/PL; prolymphocytes 10–55%), and two were classified as CLL in prolymphocytic transformation (CLL/PT; prolymphocytes >55%). All cases co-expressed CD5, CD19, and CD23; five of eight expressed ZAP-70. Of seven cases tested, four had mutated and three had unmutated IGHV genes. Conventional cytogenetic studies demonstrated t(8;14)(q24·1;q32) in five cases, t(8;22)(q24·1;q11) in two cases, and t(2;8)(p12;q24·1) in one case. Seven cases contained additional chromosomal abnormalities. All patients received combination chemotherapy. Two developed Epstein–Barr virus (EBV)-associated diffuse large B-cell lymphomas (DLBCL) that were clonally unrelated to the CLL. At follow-up, two patients are alive, four died of underlying disease, one died of EBV-associated DLBCL, and one died of an unrelated cancer. In summary, MYC rearrangement, which occurs rarely in CLL patients, is associated with increased prolymphocytes, complex cytogenetic abnormalities, and a poor prognosis.     

Chronic myelomonocytic leukemia with nucleophosmin (NPM1) mutation

Nucleophosmin (NPM1) mutations in chronic myelomonocytic leukemia (CMML) are extremely uncommon, and the clinicopathologic features of these neoplasms are poorly characterized. Over a 10‐yr interval, NPM1 mutation analysis was performed in 152 CMML at our institution. NPM1 mutations were identified in 8 (5.3%) patients, five men and three women, with a median age of 72 yr (range, 27–87). In all patients, the bone marrow was hypercellular with multilineage dysplasia, monocytosis, and retained maturation supporting a diagnosis of CMML. NPM1 mutation allele burden was <5% in two patients and >10% in six patients. Four (50%) patients, all with >10% NPM1, progressed AML with a median interval of 11 months (range, 1–21). Compared with 144 CMML without NPM1 mutations, CMML patients with NPM1 mutation presented with more severe anemia (P = 0.053), higher BM monocyte percentage (P = 0.033), and an increased tendency for AML progression (P = 0.088) and an inferior overall survival (P = 0.076). Mutations involving NRAS/KRAS (2/7), TET2(2/5), ASXL1(1/5,) and FLT3(0/8) were not significantly different between these two groups. In summary, CMML with NPM1 mutation shows histopathological features of CMML, but patients appear to have a high probability for AML progression and may require aggressive clinical intervention, especially in patients with a high mutation burden.