The distribution of MLL breakpoints correlates with outcome in infant acute leukaemia

Acute leukaemia in early childhood ‐ and mainly infant leukaemia (IL) – is characterized by acquired genetic alterations, most commonly by the presence of distinct MLL rearrangements (MLL‐r). The aim of this study was to investigate possible correlations between clinical features and molecular analyses of a series of 545 childhood leukaemia (≤24 months of age) cases: 385 acute lymphoblastic leukaemia (ALL) and 160 acute myeloid leukaemia (AML). The location of the genomic breakpoints was determined in a subset of 30 MLL‐r cases. The overall survival of the investigated cohort was 60·5%, as determined by the Kaplan‐Meier method. Worse outcomes were associated with age at diagnosis ≤6 months (P < 0·001), high white blood cell count (P = 0·001), and MLL‐r (P = 0·002) in ALL, while children with AML displayed a poorer outcome (P = 0·009) regardless of their age strata. Moreover, we present first evidence that MLL‐r patients with poor outcome preferentially displayed chromosomal breakpoints within MLL intron 11. Based on the literature, most MLL‐r IL display a breakpoint localization towards intron 11, which in turn may explain their worse clinical course. In summary, the MLL breakpoint localization is of clinical importance and should be considered as a novel outcome predictor for MLL‐r patients.     

Langerhans cell histiocytosis in children: from the bench to bedside for an updated therapy

Langerhans cell histiocytosis (LCH) is a rare disease, affecting subjects of any age, with extremely variable clinical manifestations. Although most patients with LCH have localized disease, requiring local or even no therapy, those patients with disseminated, ‘multi‐system’ disease require specific therapy because they may be at risk for morbidity or even mortality. The current standard of care has developed empirically, based mainly on the experience of treating children with leukaemia and other haemo‐proliferative disorders. At the time of writing, the combined use of vinblastine and prednisone remains the standard of care for children with multi‐system LCH. The combination of cytarabine and cladribine is the current standard for second‐line therapy of refractory cases with vital organ dysfunction. Recent advances in the knowledge of the pathogenesis of LCH may support a change in treatment strategy. Evidence of mutations that aberrantly activate RAF/MEK/ERK signalling in over two thirds of patients with LCH may direct a target therapy strategy. Vemurafenib, a small molecule widely used in the treatment of melanoma, is the main candidate for testing in prospective trials for patients with evidence of BRAF^V600E mutation on lesional tissue. Additional molecules, including the recently approved trametinib, could follow. Identification of mutations in other genes in the remaining multisystem LCH cases could contribute to define a scenario in which target therapy becomes the main therapeutic choice in this intriguing disorder. However, because the long‐term risks and benefits of these agents in children are unknown, and other effective treatments exist for many LCH patients, the optimal indications for administering a tyrosine kinase inhibitor to children is an open question.     

No significant prognostic value of normal precursor B‐cell regeneration in paediatric acute myeloid leukaemia after induction treatment

B‐cell precursors (BCP) regeneration in bone marrow (BM) after induction chemotherapy is prognostic for good treatment response in adult acute myeloid leukaemia (AML). We detected BCP regeneration in 81% of 59 paediatric AML patients at first complete remission; this compared to 46% in an adult study. BCP regeneration did not correlate with outcome or minimal residual disease levels. In 36 healthy BM controls, BCP levels were significantly higher in children as compared to adults. Therefore, BCP regeneration does not reflect good response to treatment in paediatric AML, possibly due to the relatively high base‐line levels of BCP in children.     

DNA copy number alterations mark disease progression in paediatric chronic myeloid leukaemia

Early recognition of children with chronic phase chronic myeloid leukaemia (CML‐CP) at risk for developing a lymphoid blast crisis (LyBC) is desirable, because therapy options in CML‐LyBC are limited. We used Multiplex Ligation‐dependent Probe Amplification to determine whether B‐cell lymphoid leukaemia‐specific copy number alterations (CNAs) (e.g. IKZF1, PAX5, CDKN2A deletions) could be detected in CML‐CP and may be used to predict disease progression to LyBC. CNAs were detected in all patients with CML‐LyBC, but in none of the 77 patients with CML‐CP. Based on this study we conclude that CNAs remain a hallmark of disease progression.     

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We analysed the long‐term outcome of 35 children and adolescents (<20 years at diagnosis) with chronic myeloid leukaemia (CML) in chronic phase: 20 patients had received interferon‐alpha and/or tyrosine kinase inhibitors (TKIs), and 15 underwent a haematopoietic stem cell transplant. The 10‐year survival probabilities were similar in transplanted and non‐transplanted patients (73·3% vs. 72·1%, respectively), whereas the survival probability was significantly lower in patients diagnosed before 1999 compared to those diagnosed afterwards (62·1% vs. 100%, P = 0·0384). The availability of TKIs and the standardized molecular monitoring have significantly improved treatment, management and outcome in children and adolescents with CML.     

Acute lymphoblastic leukaemia

Acute lymphoblastic leukaemia, a malignant disorder of lymphoid progenitor cells, affects both children and adults, with peak prevalence between the ages of 2 and 5 years. Steady progress in development of effective treatments has led to a cure rate of more than 80% in children, creating opportunities for innovative approaches that would preserve past gains in leukaemia-free survival while reducing the toxic side-effects of current intensive regimens. Advances in our understanding of the pathobiology of acute lymphoblastic leukaemia, fuelled by emerging molecular technologies, suggest that drugs specifically targeting the genetic defects of leukaemic cells could revolutionise management of this disease. Meanwhile, studies are underway to ascertain the precise events that take place in the genesis of acute lymphoblastic leukaemia, to enhance the clinical application of known risk factors and antileukaemic agents, and to identify treatment regimens that might boost the generally low cure rates in adults and subgroups of children with high-risk leukaemia.     

Chlorinated adenosine analogue induces AMPK and autophagy in chronic lymphocytic leukaemia cells during therapy

8‐chloro‐adenosine (8‐Cl‐Ado) is currently in phase‐I clinical trials for acute myeloid leukaemia and chronic lymphocytic leukaemia (CLL). Previously, we demonstrated that treatment with 8‐Cl‐Ado leads to diminished ATP levels. We hypothesized that AMP‐activated protein kinase (AMPK) signalling would be initiated in these cells, leading to induction of autophagy. AMPK activation and induction of autophagy were demonstrated during preclinical incubations in CLL cells with the analogues. Importantly, we extended similar observations in CLL lymphocytes during an 8‐Cl‐Ado phase‐I trial. In conclusion, 8‐Cl‐Ado treatment induces autophagy in CLL lymphocytes in vitro as well as in vivo during clinical trial.     

Impact of ELN recommendations in the management of first‐line treated chronic myeloid leukaemia patients: a French cross‐sectional study

The availability of tyrosine kinase inhibitors has extended therapeutic options for chronic myeloid leukaemia (CML) patients. Monitoring recommendations and clinical response goals have recently been updated. The objective of this study was to describe the profile of CML patients in chronic phase currently receiving first‐line therapy, including treatment, monitoring and response kinetics. A multicentre, cross‐sectional, epidemiological survey in unselected chronic phase CML patients in France attending consultations during a one‐month period was performed. 438 of 697 (62·8%) reported patients were currently receiving first‐line treatment and were analysed. Imatinib was the most frequently received treatment (72·4% of patients). Retrospective cytogenetic and molecular assessments at 3, 6, 12 or 18 months were available in 88·4% of patients. At the 12‐month assessment, 32·2% were not in major molecular response (MMR). At last assessment, among 355 patients with duration of treatment ≥ 12 months, 91·5% had achieved MMR and 66·5% were in deep molecular response. This study, performed in everyday practice population of CML patients, suggests that monitoring of molecular responses in real‐life practice is aligned with European LeukaemiaNet recommendations. The majority of patients still receiving first‐line treatment are in optimal response, with a few being classified as in the warning area or responding to failure.     

Neonatal leukaemia

Neonatal leukaemia is defined as occurring within the first 28 days of life and most, if not all, cases are congenital. With the exception of Down syndrome‐associated transient abnormal myelopoiesis, which is not considered here, neonatal leukaemias are rare. In two‐thirds of patients the disease manifests as an acute myeloid leukaemia, frequently with monocytic/monoblastic characteristics. Most other cases are acute lymphoblastic leukaemia, particularly B lineage, but some are mixed phenotype or blastic plasmacytoid dendritic cell neoplasms. The most frequently observed cytogenetic/molecular abnormality is t(4;11)(q21.3;q23.3)/KMT2A‐AFF1 followed by t(1;22)(p13.3;q13.1)/RBM15‐MKL1 and t(8;16)(p11.2;p13.3)/KAT6A‐CREBBP. Common clinical features include prominent hepatosplenomegaly and a high incidence of skin involvement, sometimes in the absence of bone marrow disease. A distinctive feature is the occurrence of spontaneous remission in some cases, particularly in association with t(8;16). In this review, we summarise current knowledge of the clinical, cytogenetic and molecular features of neonatal leukaemia and discuss clinical management of these cases.     

A 4‐gene expression score associated with high levels of Wilms Tumor‐1 (WT1) expression is an adverse prognostic factor in acute myeloid leukaemia

Wilms Tumor‐1 (WT1) expression level is implicated in the prognosis of acute myeloid leukaemia (AML). We hypothesized that a gene expression profile associated with WT1 expression levels might be a good surrogate marker. We identified high WT1 gene sets by comparing the gene expression profiles in the highest and lowest quartiles of WT1 expression in two large AML studies. Two high WT1 gene sets were found to be highly correlated in terms of the altered genes and expression profiles. We identified a 17‐probe set signature of the high WT1 set as the optimal prognostic predictor in the first AML set, and showed that it was able to predict prognosis in the second AML series after adjustment for European LeukaemiaNet genetic groups. The gene signature also proved to be of prognostic value in a third AML series of 163 samples assessed by RNA sequencing, demonstrating its cross‐platform consistency . This led us to derive a 4‐gene expression score, which faithfully predicted adverse outcome. In conclusion, a short gene signature associated with high WT1 expression levels and the resultant 4‐gene expression score were found to be predictive of adverse prognosis in AML. This study provides new clues to the molecular pathways underlying high WT1 states in leukaemia.     

Prophylactic bypassing agent use before and during immune tolerance induction in patients with haemophilia A and inhibitors to FVIII

The development of high‐titre inhibitory antibodies (inhibitors) against factor VIII (FVIII) remains a challenge in the management of patients with haemophilia A (HA). Patients with high‐titre inhibitors are more likely to experience uncontrolled bleeding, physical disability from chronic arthropathy and premature death compared with those without this complication. Immune tolerance induction (ITI), utilizing repeated infusions of FVIII, is an effective therapeutic approach to eliminating inhibitory antibodies. This strategy can eradicate FVIII inhibitors, so that FVIII‐specific tolerance is induced. However, patients undergoing ITI are still vulnerable to the development of serious and/or repeated bleeding events. The efficacy of bypassing agents in preventing bleeding episodes has been widely proven in patients with HA and inhibitors to FVIII. Evidence suggests that reducing bleeding during ITI can also shorten the time to tolerance. There are concerns with the use of bypassing agents, including the cost of treatment, short half‐life, management of non‐responders and the risk of thrombosis. Despite these concerns, and the still limited evidence from prospective studies and consensus reports, the use of prophylaxis with bypassing agents during ITI has been gaining support. This review presents a rationale and current data supporting the use of prophylactic bypassing agents as effective and safe therapies to reduce the incidence of joint bleeding due to inhibitors and improve quality of life in patients with HA undergoing ITI.     

Molecular profiling of chronic lymphocytic leukaemia: genetics meets epigenetics to identify predisposing genes

Molecular profiling may lead to a better understanding of a disease. This knowledge is especially important in malignancies, where multiple alterations are required during the progression from premalignant to malignant stages. Such information can be useful for the development of novel biomarkers that allow the prediction of a clinical course, response to treatment or early detection. Molecular data is also utilized to develop targeted therapies. Moreover, gene defects identified in profiling studies will help to understand the molecular pathways disrupted in the disease. This review provides an overview of molecular profiling approaches in chronic lymphocytic leukaemia (CLL). We will describe our current understanding of genetic alterations in CLL, the use of familial CLL for the identification of predisposing mutations, and the search for epigenetic alterations in CLL.     

HMGA2 as a potential molecular target in KMT2A‐AFF1‐positive infant acute lymphoblastic leukaemia

Acute lymphoblastic leukaemia (ALL) in infants is an intractable cancer in childhood. Although recent intensive chemotherapy progress has considerably improved ALL treatment outcome, disease cure is often accompanied by undesirable long‐term side effects, and efficient, less toxic molecular targeting therapies have been anticipated. In infant ALL cells with KMT2A (MLL) fusion, the microRNA let‐7b (MIRLET7B) is significantly downregulated by DNA hypermethylation of its promoter region. We show here that the expression of HMGA2, one of the oncogenes repressed by MIRLET7B, is reversely upregulated in infant ALL leukaemic cells, particularly in KMT2A‐AFF1 (MLL‐AF4) positive ALL. In addition to the suppression of MIRLET7B, KMT2A fusion proteins positively regulate the expression of HMGA2. HMGA2 is one of the negative regulators of CDKN2A gene, which encodes the cyclin‐dependent kinase inhibitor p16^INK4A. The HMGA2 inhibitor netropsin, when combined with demethylating agent 5‐azacytidine, upregulated and sustained the expression of CDKN2A, which resulted in growth suppression of KMT2A‐AFF1‐expressing cell lines. This effect was more apparent compared to treatment with 5‐azacytidine alone. These results indicate that the MIRLET7B‐HMGA2‐CDKN2A axis plays an important role in cell proliferation of leukaemic cells and could be a possible molecular target for the therapy of infant ALL with KMT2A‐AFF1.     

Comparative analysis between RQ‐PCR and digital‐droplet‐PCR of immunoglobulin/T‐cell receptor gene rearrangements to monitor minimal residual disease in acute lymphoblastic leukaemia

Real‐time quantitative polymerase chain reaction (RQ‐PCR) is a standardized tool for minimal residual disease (MRD) monitoring in acute lymphoblastic leukaemia (ALL). The applicability of this technology is limited by the need of a standard curve based on diagnostic DNA. The digital droplet PCR (ddPCR) technology has been recently applied to various medical fields, but its use in MRD monitoring is under investigation. In this study, we analysed 50 ALL cases by both methods in two phases: in the first, we established analytical parameters to investigate the applicability of this new technique; in the second, we analysed MRD levels in 141 follow‐up (FU) samples to investigate the possible use of ddPCR for MRD monitoring in ALL patients. We documented that ddPCR has sensitivity and accuracy at least comparable to those of RQ‐PCR. Overall, the two methods gave concordant results in 124 of the 141 analysed MRD samples (88%, P = 0·94). Discordant results were found in 12% borderline cases. The results obtained prove that ddPCR is a reliable method for MRD monitoring in ALL, with the advantage of quantifying without the need of the calibration curves. Its application in a cohort of patients with a longer FU will conclusively define its clinical predictive value.     

Treatment of relapsed/refractory acute myeloid leukaemia in adults

The prognosis of relapsed acute myeloid leukaemia (AML) is poor and treatment is challenging. While the most potent treatment modality for patients who achieve a complete remission after relapse is still allogeneic haematopoietic cell transplantation (allo‐HCT), both transplant‐related mortality and relapse rates are high and many patients are not candidates for this approach. After a few decades of relative stasis in this field, a large number of novel approaches have become available to tackle this highly fatal disease. This is mostly due to our improved understanding of disease pathogenesis (including targetable mutations) and the anti‐leukaemia potential of the immune system. Several small‐molecule inhibitors and immunotherapeutic options are being explored in clinical trials and many more are in pre‐clinical phase. Future studies will focus on novel and mechanistically driven combinations, sequential treatments, and low‐toxicity maintenance strategies. While cure of relapsed/refractory AML without allo‐HCT is currently unlikely, treatments are becoming less toxic and remissions are lasting longer.     

Identification of emerging FLT3 ITD‐positive clones during clinical remission and kinetics of disease relapse in acute myeloid leukaemia with mutated nucleophosmin

FLT3 internal tandem duplication (ITD) mutations are frequently detected at diagnosis in cytogenetically normal acute myeloid leukaemia (CN‐AML) and predict unfavourable outcome. FLT3 ITD is an unstable aberration and may be lost or acquired at relapse. Recent whole genome sequencing studies have suggested that FLT3 ITD⁺ve AML relapse may evolve from small subclones undetectable at diagnosis by routine polymerase chain reaction (PCR). We developed a patient‐specific real‐time quantitative‐PCR (RQ‐PCR) to implement FLT3 ITD detection in six AML patients whose blasts carried wild‐type FLT3 at diagnosis and who relapsed with FLT3 ITD by routine PCR. Patient‐specific forward primers were designed after cloning and sequencing the FLT3 ITD in each case. The assay allowed retrospective detection of FLT3 ITD in diagnostic samples of 4/6 cases and to establish the kinetics of clonal evolution preceding relapse. After conventional chemotherapy, all patients had early relapse despite having been classified as NPM1⁺ve/FLT3 ITD^?ve at presentation, with shorter remissions being observed in four patients re‐classified as FLT3 ITD⁺ve by the new assay. Notably, FLT3 ITD clone became detectable by conventional PCR in three patients tested during remission after initial treatment. Our data underscore the need of identifying low FLT3 ITD levels, which are probably associated with relapse in otherwise good prognosis CN‐AML.     

Allogeneic bone marrow transplantation for acute leukaemia: comparative outcomes for adults and children

Advances in both allogeneic marrow transplantation and conventional therapy for acute leukaemia have complicated the choice between bone marrow transplantation (BMT) and other remission treatment options. Because older patients may be more susceptible to BMT-related complications, this study analysed the effect of age on clinical outcome for 149 patients with acute leukaemia in remission receiving allogeneic BMT. Overall projected relapse-free survival at 3 years post-transplant is equivalent for 48 adults (18 years or older) and 101 children (less than 18) at 45.4% (31.1-59.6; 95% confidence interval) and 39.9% (30.1-49.7; 95% C.I.), respectively. Among 73 patients with acute lymphocytic leukaemia (ALL) 35.3% of adults and 30.1% of children survive relapse-free at 3 years. Cox multiple regression analysis demonstrated that higher diagnostic white count, but not pre-transplant extramedullary leukaemia, remission number, or age, was important as an independent adverse clinical prognostic factor for patients with ALL. Overall outcome was better for 76 patients with acute myeloid leukaemia (AML) with 51.6% of adults and 52.9% of children surviving relapse-free at 3 years post-transplant. Cox multivariate regression analysis identified first remission status and lower white cell count, but not patient age, as independent predictors of improved relapse-free survival for AML patients. Adults had greater transplant morbidity, predominantly related to a higher incidence of acute graft-versus-host disease (GVHD), resulting in longer hospital stay. Survival at 100 d, long-term survival and clinical performance status were similar in both age groups. These data suggest that results of allogeneic BMT for adults with acute leukaemia compare favourably with those found in children and are superior to most reports of conventional chemotherapy. Allogeneic BMT remains a reasonable option for remission acute leukaemia patients up to the age of 45.     

Cell cycle status in AML blast cells from peripheral blood,bone marrow aspirates and trephines and implications for biological studies and treatment

Using immunohistochemistry and flow cytometry to define phases of the cell cycle, this study shows that a high proportion of acute myeloid leukaemia (AML) blasts obtained from trephine biopsies are cycling, whereas >95% of peripheral blood‐derived blasts are arrested in G₁. Results obtained from bone marrow aspirates are more similar to those from blood rather than from trephine biopsies. These differences were confirmed by gene expression profiling in a patient with high count AML. This has implications for cell cycle and other biological studies using aspirates rather than trephine biopsies and for the use of cell mobilising agents before chemotherapy.