Isolated del(5q) in myeloid malignancies: clinicopathologic and molecular features in 143 consecutive patients

Myeloid neoplasm with isolated del(5q) and the MPLW515L mutation fulfills the WHO diagnostic criteria for ET

A 70-year-old male was referred to our hospital for marked thrombocytosis without anemia. The patient simultaneously presented with an MPL W515L mutation, one of the major driver mutations in essential thrombocythemia (ET), and deletion of 5q, a characteristic cytogenetic abnormality in myelodysplastic syndrome (MDS). Bone marrow examination showed a combination of both mature hyperlobulated megakaryocytes, as found in ET, and small hypolobulated megakaryocytes, typically found in MDS with del(5q). The present case is consistent with the recently proposed category of myeloid neoplasms with isolated del(5q) and an MPN driver mutation.

Acute myeloid leukemia with isolated del(5q) is associated with IDH1/IDH2 mutations and better prognosis when compared to acute myeloid leukemia with complex karyotype including del(5q)

Myelodysplastic syndrome with isolated del(5q) is a well-recognized entity with a relatively favorable prognosis. Isolated del(5q) in acute myeloid leukemia is rare and acute myeloid leukemia cases with isolated del(5q) are not well characterized. Del(5q) has been shown to be a poor prognostic marker in acute myeloid leukemia based on multivariable analysis in large cohort studies, which contained mostly cases with del(5q) in the context of multiple chromosomal abnormalities. To further characterize acute myeloid leukemia with isolated del(5q), clinicopathologic characterization including mutation analysis was performed. During a 10-year period, we identified 12 cases of acute myeloid leukemia with isolated del(5q), 7 cases of acute myeloid leukemia with del(5q) plus one additional chromosome abnormality not involving chromosome 7, as well as two control groups composed of 124 cases of acute myeloid leukemia with complex karyotype including del(5q), and 40 cases of myelodysplastic syndrome with isolated del(5q). At diagnosis, cases of acute myeloid leukemia with isolated del(5q) had higher platelet counts (p = 0.044), hemoglobin (p = 0.011), and mean corpuscular volume (p = 0.017) compared with cases of acute myeloid leukemia with complex karyotype including del(5q). Acute myeloid leukemia with isolated del(5q) was less likely therapy-related (p = 0.037), more likely to have IDH1/IDH2 mutations (p = 0.009), and less likely to have TP53 mutations (p = 0.005) when compared to acute myeloid leukemia with complex karyotype including del(5q). Acute myeloid leukemia with isolated del(5q) also showed longer overall survival than acute myeloid leukemia with complex karyotype cases including del(5q) (p = 0.004). In summary, acute myeloid leukemia with isolated del(5q) appeared to show some distinct clinicopathologic and genomic features as compared to cases of acute myeloid leukemia with complex karyotype including del(5q).

Genetic Alterations in Essential Thrombocythemia Progression to Acute Myeloid Leukemia: A Case Series and Review of the Literature

The genetic events associated with transformation of myeloproliferative neoplasms (MPNs) to secondary acute myeloid leukemia (sAML), particularly in the subgroup of essential thrombocythemia (ET) patients, remain incompletely understood. Deep studies using high-throughput methods might lead to a better understanding of genetic landscape of ET patients who transformed to sAML. We performed array-based comparative genomic hybridization (aCGH) and whole exome sequencing (WES) to analyze paired samples from ET and sAML phases. We investigated five patients with previous history of MPN, which four had initial diagnosis of ET (one case harboring JAK2 p.Val617Phe and the remaining three CALR type II p.Lys385fs*47), and one was diagnosed with MPN/myelodysplastic syndrome with thrombocytosis (SF3B1 p.Lys700Glu). All were homogeneously treated with hydroxyurea, but subsequently transformed to sAML (mean time of 6 years/median of 4 years to transformation). Two of them have chromosomal abnormalities, and both acquire 2p gain and 5q deletion at sAML stage. The molecular mechanisms associated with leukemic progression in MPN patients are not clear. Our WES data showed TP53 alterations recurrently observed as mutations (missense and frameshift) and monoallelic loss. On the other hand, aCGH showed novel chromosome abnormalities (+2p and del5q) potentially associated with disease progression. The results reported here add valuable information to the still fragmented molecular basis of ET to sAML evolution. Further studies are necessary to identify minimal deleted/amplified region and genes relevant to sAML transformation.

Acute Myeloid Leukemia With Myelodysplasia-Related Changes

OBJECTIVES

Acute myeloid leukemia with myelodysplasia-related changes (AML-MRC) is a heterogeneous disorder defined by morphologic, genetic, or clinical features. Genetic abnormalities associated with AML-MRC are often associated with adverse prognostic features, and many cases are preceded by a myelodysplastic syndrome (MDS) or a myelodysplastic/myeloproliferative neoplasm.

METHODS

Although the criteria of 20% or more blasts in blood or bone marrow and multilineage dysplasia affecting 50% or more of cells in two or more of the myeloid lineages seem straightforward for AML-MRC, identification of morphologic dysplasia among observers is not always consistent, and there is morphologic overlap with other leukemic disorders such as acute erythroleukemia.

RESULTS

Session 3 of the workshop cases displayed heterogeneity as expected within AML-MRC, yet several cases suggested that recently recognized entities may exist within this category, such as familial MDS/AML predisposition syndromes and rare cases of high-risk AML associated with the cryptic t(5;11)(q35;p15);NUP98-NSD1 that may masquerade as a del(5q). However, most cases of AML-MRC were usually associated with adverse genetic abnormalities, particularly -5/del(5q), -7/del(7q), and/or complex karyotypes.

CONCLUSIONS

Whole-genome sequencing and array studies may identify genetic abnormalities, such as those affecting TP53, which may provide prognostic information.

PP2A: The Achilles Heal in MDS with 5q Deletion

Myelodysplastic syndromes (MDS) represent a hematologically diverse group of myeloid neoplasms, however, one subtype characterized by an isolated deletion of chromosome 5q [del(5q)] is pathologically and clinically distinct. Patients with del(5q) MDS share biological features that account for the profound hypoplastic anemia and unique sensitivity to treatment with lenalidomide. Ineffective erythropoiesis in del(5q) MDS arises from allelic deletion of the ribosomal processing S-14 (RPS14) gene, which leads to MDM2 sequestration with consequent p53 activation and erythroid cell death. Since its approval in 2005, lenalidomide has changed the natural course of the disease. Patients who achieve transfusion independence and/or a cytogenetic response with lenalidomide have a decreased risk of progression to acute myeloid leukemia and an improved overall survival compared to non-responders. Elucidation of the mechanisms of action of lenalidomide in del(5q) MDS has advanced therapeutic strategies for this disease. The selective cytotoxicity of lenalidomide in del(5q) clones derives from inhibition of a haplodeficient phosphatase whose catalytic domain is encoded within the common deleted region on chromosome 5q, i.e., protein phosphatase 2A (PP2Acα). PP2A is a highly conserved, dual specificity phosphatase that plays an essential role in regulation of the G2/M checkpoint. Inhibition of PP2Acα results in cell-cycle arrest and apoptosis in del(5q) cells. Targeted knockdown of PP2Acα using siRNA is sufficient to sensitize non-del(5q) clones to lenalidomide. Through its inhibitory effect on PP2A, lenalidomide stabilizes MDM2 to restore p53 degradation in erythroid precursors, with subsequent arrest in G2/M. Unfortunately, the majority of patients with del(5q) MDS develop resistance to lenalidomide over time associated with PP2Acα over-expression. Targeted inhibition of PP2A with a more potent inhibitor has emerged as an attractive therapeutic approach for patients with del(5q) MDS.

Myelodysplastic disorders carrying both isolated del(5q) and JAK2(V617F) mutation: concise review, with focus on lenalidomide therapy

The concomitant presence of del(5q) and JAK2(V617F) mutation is an infrequent event which occurs in rare patients with peculiar cytogenetic, molecular, morphological and clinical features, resembling those of both myelodysplastic syndromes and myeloproliferative neoplasms. Lenalidomide may induce rapid, profound, and long-lasting responses in a subset of these patients. However, the mechanism(s) by which the drug acts in these conditions remain not completely elucidated. A new case report and a review of all cases published so far in this setting are provided. Furthermore, the possibility of categorizing - from a clinical, pathological, and biological point of view - for at least some of these patients as a potential distinct entity is discussed.

Myeloid Neoplasms with inv(3)(q21q26.2) or t(3;3)(q21;q26.2)

Acute myeloid leukemia (AML) with inv(3)(q21q26.2)/t(3;3)(q21;q26.2) [inv3/t(3;3)] is a distinct entity under the subgroup of AMLs with recurrent genetic abnormalities in the 2008 World Health Organization classification. Myelodysplastic syndrome (MDS) with inv3/t(3;3) has a high risk of progression to AML. AML and MDS with inv3/t(3;3) have a similarly aggressive clinical course with short overall survival (OS) and are commonly refractory to therapy. In this article, clinical and pathologic features and prognosis in AML and MDS with inv3/t(3;3) are reviewed, and other myeloid neoplasms with similar dysplastic features to be differentiated from AML and MDS with inv3/t(3;3) are discussed.

Outcome of pediatric patients with acute myeloid leukemia (AML) and -5/5q- abnormalities from five pediatric AML treatment protocols: a report from the Children's Oncology Group

BACKGROUND

Abnormalities of chromosome 5q (-5/5q-) are associated with poor prognosis in adults with acute myeloid leukemia (AML). However, there are no large studies on outcomes of children with -5/5q- AML. To determine the disease correlates of this group, we retrospectively analyzed cytogenetic data from five studies of childhood AML.

PROCEDURE

Data from patients whose cytogenetic clones included -5/5q-, with the exception of those with acute promyelocytic leukemia or Down syndrome, were included.

RESULTS

Of the 2,240 patients with cytogenetic data available, 26 (1.2%) had -5 or 5q-. A significant number of these patients were age 11-21 (61.5%, P = 0.031) and had M0 morphology compared with patients without -5/5q- (24.0% vs. 2.8%, P < 0.001). Twenty-two of the 26 patients had a complete remission (CR) response to induction chemotherapy. The 5-year overall survival (OS) from the time of diagnosis for the -5/5q- patients was significantly lower than for patients without -5/5q- (27 ± 17% vs. 50 ± 2%, P = 0.027). Similarly, from induction CR, patients with -5/5q- had significantly worse disease free survival, OS and relapse risk than those without this abnormality (27 ± 19% vs. 46 ± 2%, P = 0.035, 32 ± 20% vs. 57 ± 2%, P = 0.025, 68 ± 21% vs. 45 ± 2%, P = 0.01, respectively).

CONCLUSIONS

Pediatric patients with AML and -5/5q- had a very poor outcome. These findings support the need for new or novel therapies for these patients.

Perturbations of 5-hydroxymethylcytosine patterning in hematologic malignancies

The recent identification of covalent cytosine modifications derived from the metabolism of 5-methylcytosine (5-mC) and catalyzed by the TET proteins has facilitated molecular insight into a new subclass of acute myeloid leukemias (AMLs). TET2-mutant AMLs have the predicted hypermethylation phenotype expected given the inability of the mutant TET2 protein to convert 5-mC to 5-hydroxymethylcytosine (5-hmC). In addition, IDH1/2 mutations confer a gain-of-function, allowing the enzymes to process α-ketoglutarate to 2-hydroxyglutarate, which inhibits the TET proteins and ultimately induces the same hypermethylation phenotype. New techniques are being developed rapidly that have the unprecedented capacity to distinguish among the various covalent cytosine modifications now known to exist. Soon, these methods will be harnessed to yield a new level of insight into AMLs with altered distribution of 5-hmC, information that may allow new diagnostic and therapeutic approaches for patients with this subtype of AML.

Targeted re-sequencing analysis of 25 genes commonly mutated in myeloid disorders in del(5q) myelodysplastic syndromes

Interstitial deletion of chromosome 5q is the most common chromosomal abnormality in myelodysplastic syndromes. The catalogue of genes involved in the molecular pathogenesis of myelodysplastic syndromes is rapidly expanding and next-generation sequencing technology allows detection of these mutations at great depth. Here we describe the design, validation and application of a targeted next-generation sequencing approach to simultaneously screen 25 genes mutated in myeloid malignancies. We used this method alongside single nucleotide polymorphism-array technology to characterize the mutational and cytogenetic profile of 43 cases of early or advanced del(5q) myelodysplastic syndromes. A total of 29 mutations were detected in our cohort. Overall, 45% of early and 66.7% of advanced cases had at least one mutation. Genes with the highest mutation frequency among advanced cases were TP53 and ASXL1 (25% of patients each). These showed a lower mutation frequency in cases of 5q- syndrome (4.5% and 13.6%, respectively), suggesting a role in disease progression in del(5q) myelodysplastic syndromes. Fifty-two percent of mutations identified were in genes involved in epigenetic regulation (ASXL1, TET2, DNMT3A and JAK2). Six mutations had allele frequencies <20%, likely below the detection limit of traditional sequencing methods. Genomic array data showed that cases of advanced del(5q) myelodysplastic syndrome had a complex background of cytogenetic aberrations, often encompassing genes involved in myeloid disorders. Our study is the first to investigate the molecular pathogenesis of early and advanced del(5q) myelodysplastic syndromes using next-generation sequencing technology on a large panel of genes frequently mutated in myeloid malignancies, further illuminating the molecular landscape of del(5q) myelodysplastic syndromes.

Update on cytogenetic and molecular changes in myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are characterized by ineffective hematopoiesis and a high propensity to transform to acute myeloid leukemia (AML). In the pathogenesis of the disease, both gene mutations and cytogenetic changes play an important role. The latter have been integrated into prognostic scoring systems including the IPSS (International Prognostic Scoring System) and WPSS (World Health Organization [WHO] classification-based Prognostic Scoring System). In these systems and in multivariate analyses comparing clinical and genetic data, complex karyotypes are associated with a particularly poor prognosis. del(5q) plays a distinct role by classifying the only genetically defined WHO subtype. Also, due to advancement in technology such as whole genome sequencing, the number of known mutations occurring in MDS is steadily increasing. Important recent discoveries include mutations in EZH2, DNMT3A, ASXL1 and IDH1/2. Like TET2, the most commonly mutated gene in MDS, all are involved in epigenetic regulation. Mutations such as ASXL1, RUNX1, EZH2, ETV6/TEL and TP53 have an adverse impact on patient overall survival. Early evidence suggests that some mutations might influence treatment response, necessitating reassessment of the prognostic effect of genetic alterations in the light of every new treatment. This review discusses clinical and biological effects of the most common cytogenetic and molecular aberrations in patients with MDS.

Differential prognostic effect of IDH1 versus IDH2 mutations in myelodysplastic syndromes: a Mayo Clinic study of 277 patients

Unlike the case with acute myeloid leukemia, there is limited information on the prognostic impact of isocitrate dehydrogenase (IDH) mutations in myelodysplastic syndromes (MDS). In the current study of 277 patients with MDS, IDH mutations were detected in 34 (12%) cases: 26 IDH2 (all R140Q) and 8 IDH1 (6 R132S and 2 R132C). Mutational frequency was 4% (2 of 56) in refractory anemia with ring sideroblasts, 12% (16 of 130) in refractory cytopenia with multilineage dysplasia, 14% (2 of 14) in MDS-unclassifiable, 14% (6 of 42) in refractory anemia with excess blasts (RAEB)-1 and 23% (8 of 35) in RAEB-2. Normal karyotype was noted in all but one IDH1-mutated cases and 13 IDH2-mutated cases. Multivariable analysis identified presence of mutant IDH1 (P=0.0004; hazard ration 4.0, 95% confidence interval 1.9-8.8), revised International Prognostic Scoring System risk category (P<0.0001), and red cell transfusion need (P=0.002) as independent predictors of inferior survival. In a similar multivariable analysis, mutant IDH1 was the only variable associated with shortened leukemia-free survival (P=0.001; hazard ration 7.0, 95% confidence interval 2.3-20.8). The presence of IDH2R140Q did not affect the overall (P=0.54) or leukemia-free (P=0.81) survival. The current study suggests a powerful adverse prognostic effect for mutant IDH1 in MDS.

IDH mutations in primary myelofibrosis predict leukemic transformation and shortened survival: clinical evidence for leukemogenic collaboration with JAK2V617F

Isocitrate dehydrogenase (IDH) mutations are frequent in blast-phase myeloproliferative neoplasms and might therefore contribute to leukemic transformation. We examined this possibility in 301 consecutive patients with chronic-phase primary myelofibrosis (PMF). The mutant IDH was detected in 12 patients (4%): 7 IDH2 (5 R140Q, 1 R140W and 1 R172G) and 5 IDH1 (3 R132S and 2 R132C). In all, 6 (50%) of the 12 IDH-mutated patients also expressed JAK2V617F. Overall, 18 (6%) patients displayed only MPL and 164 (54.3%) only JAK2 mutations. Multivariable analysis that accounted for conventional risk factors disclosed inferior overall survival (OS; P=0.03) and leukemia-free survival (LFS; P=0.003) in IDH-mutated patients: OS hazard ratio (HR) was 0.39 (95% confidence interval (95% CI) 0.2–0.75), 0.50 (95% CI 0.27–0.95) and 0.53 (95% CI 0.23–1.2) for patients with no, JAK2 or MPL mutations, respectively. Further analysis disclosed a more pronounced effect for the mutant IDH on OS and LFS in the presence (P=0.0002 and P<0.0001, respectively) as opposed to the absence (P=0.34 and P=0.64) of concomitant JAK2V617F. Analysis of paired samples obtained during chronic- and blast-phase disease revealed the presence of both IDH and JAK2 mutations at both time points. Our observations suggest that IDH mutations in PMF are independent predictors of leukemic transformation and raise the possibility of leukemogenic collaboration with JAK2V617F.