Henrik Hasle

Somatic mutations in PTPN11 in juvenile myelomonocytic leukemia, myelodysplastic syndromes and acute myeloid leukemia

We report here that individuals with Noonan syndrome and juvenile myelomonocytic leukemia (JMML) have germline mutations in PTPN11 and that somatic mutations in PTPN11 account for 34% of non-syndromic JMML. Furthermore, we found mutations in PTPN11 in a small percentage of individuals with myelodysplastic syndrome (MDS) and de novo acute myeloid leukemia (AML). Functional analyses documented that the two most common mutations in PTPN11 associated with JMML caused a gain of function.

Risks of leukaemia and solid tumours in individuals with Down's syndrome

BACKGROUND Individuals with Downs syndrome have a greater risk of leukaemia than the general population, but reliable estimates of the age-specific risk are lacking and little is known about the risk of solid tumours. METHODS We identified 2814 individuals with Downs syndrome from the Danish Cytogenetic Register, and linked the data to the Danish Cancer Registry. The number of person-years at risk was 48453. Standardised incidence ratio (SIR) and 95% CI were calculated of the basis of cancer rates specific for age and sex in the general population. FINDINGS 60 cases of cancer were found, with 49.8 expected (SIR 1.20 [95% CI 0.92-1.55]). Leukaemia constituted 60% of cases of malignant disease overall and 97% of cases in children. The SIR for leukaemia varied with age, being 56 (38-81) at age 0-4 years and 10 (4-20) at 5-29 years. No cases of leukaemia were seen after the age of 29 years. The SIR for acute myeloid leukaemia was 3.8 (1.7-8.4) times higher than that for acute lymphoblastic leukaemia in children aged 0-4 years. The cumulative risk for leukaemia by the age of 5 years was 2.1% and that by 30 years was 2.7%. Only 24 solid tumours were seen, with 47.8 expected (0.50 [0.32-0.75]). No cases of breast cancer were found, with 7.3 expected (p=0.0007). Higher than expected numbers of testicular cancers, ovarian cancers, and retinoblastomas were seen but were not significant. INTREPRETATION: The occurrence of cancer in Downs syndrome is unique with a high risk of leukaemia in children and a decreased risk of solid tumours in all age-groups. The distinctive pattern of malignant diseases may provide clues in the search for leukaemogenic genes and tumour-suppressor genes on chromosome 21.

A pediatric approach to the WHO classification of myelodysplastic and myeloproliferative diseases.

Myelodysplastic and myeloproliferative disorders are rare in childhood and there is no widely accepted system for their diagnosis and classification. We propose minimal diagnostic criteria and a simple classification scheme which, while based on accepted morphological features and conforming with the recent suggestions of the WHO, allows for the special problems of myelodysplastic diseases in children. The classification recognizes three major diagnostic groups: (1) juvenile myelomonocytic leukemia (JMML), previously named chronic myelomonocytic leukemia (CMML) or juvenile chronic myeloid leukemia (JCML); (2) myeloid leukemia of Down syndrome, a disease with distinct clinical and biological features, encompassing both MDS and AML occurring in Down syndrome; and (3) MDS occurring both de novo and as a complication of previous therapy or pre-existing bone marrow disorder (secondary MDS). The main subtypes of MDS are refractory cytopenia (RC) and refractory anemia with excess of blasts (RAEB). It is suggested retaining the subtype of RAEB-T with 20–30% blasts in the marrow until more data are available. Cytogenetics and serial assessments of the patients are essential adjuncts to morphology both in diagnosis and classification.

Novel prognostic subgroups in childhood 11q23/MLL-rearranged acute myeloid leukemia: results of an international retrospective study

Translocations involving chromosome 11q23 frequently occur in pediatric acute myeloid leukemia (AML) and are associated with poor prognosis. In most cases, the MLL gene is involved, and more than 50 translocation partners have been described. Clinical outcome data of the 11q23-rearranged subgroups are scarce because most 11q23 series are too small for meaningful analysis of subgroups, although some studies suggest that patients with t(9;11)(p22;q23) have a more favorable prognosis. We retrospectively collected outcome data of 756 children with 11q23- or MLL-rearranged AML from 11 collaborative groups to identify differences in outcome based on translocation partners. All karyotypes were centrally reviewed before assigning patients to subgroups. The event-free survival of 11q23/MLL-rearranged pediatric AML at 5 years from diagnosis was 44% (+/- 5%), with large differences across subgroups (11% +/- 5% to 92% +/- 5%). Multivariate analysis identified the following subgroups as independent prognostic predictors: t(1;11)(q21;q23) (hazard ratio [HR] = 0.1, P = .004); t(6;11)(q27;q23) (HR = 2.2, P < .001); t(10;11)(p12;q23) (HR = 1.5, P = .005); and t(10;11)(p11.2;q23) (HR = 2.5, P = .005). We could not confirm the favorable prognosis of the t(9;11)(p22;q23) subgroup. We identified large differences in outcome within 11q23/MLL-rearranged pediatric AML and novel subgroups based on translocation partners that independently predict clinical outcome. Screening for these translocation partners is needed for accurate treatment stratification at diagnosis.

Diagnosis and management of acute myeloid leukemia in children and adolescents: recommendations from an international expert panel

Despite major improvements in outcome over the past decades, acute myeloid leukemia (AML) remains a life-threatening malignancy in children, with current survival rates of ∼70%. State-of-the-art recommendations in adult AML have recently been published in this journal by Döhner et al. The primary goal of an international expert panel of the International BFM Study Group AML Committee was to set standards for the management, diagnosis, response assessment, and treatment in childhood AML. This paper aims to discuss differences between childhood and adult AML, and to highlight recommendations that are specific to children. The particular relevance of new diagnostic and prognostic molecular markers in pediatric AML is presented. The general management of pediatric AML, the management of specific pediatric AML cohorts (such as infants) or subtypes of the disease occurring in children (such as Down syndrome related AML), as well as new therapeutic approaches, and the role of supportive care are discussed.

Pattern of malignant disorders in individuals with Down's syndrome

The pattern of occurrence of malignant disorders in people with Downs syndrome (DS) is unique and may serve as a model in the search for leukaemogenic genes and tumour suppressor genes on chromosome 21, since the risk of leukaemia is higher in individuals with DS than in non-DS individuals. Acute lymphoblastic leukaemia in DS shares many of the clinical characteristics of the same malignancy in other patients, and with current intensive therapy the long-term survival is similar. Myelodysplastic syndrome and acute myeloid leukaemia have unique clinical characteristics in these patients and are best described as a single disorder, termed myeloid leukaemia of DS. When these patients are treated intensively, they show better survival rates than patients without DS. This may be related to increased expression of genes on chromosome 21 contributing to increased chemosensitivity. Chronic myeloid leukaemia and chronic lymphocytic leukaemia occur less often than expected. With the exception of an increased risk of retinoblastoma, germ-cell tumours, and perhaps lymphomas, the risk of developing solid tumours is lower in both children and adults. Breast cancer is almost absent, and the risk of a second malignant disease after treatment for leukaemia also appears to be decreased. Increased susceptibility to apoptosis in DS may result in cell death rather than malignant transformation after major cell injuries. This hypothesis would explain the decreased risk of both solid tumours and secondary cancers.

Germline CBL mutations cause developmental abnormalities and predispose to juvenile myelomonocytic leukemia

CBL encodes a member of the Cbl family of proteins, which functions as an E3 ubiquitin ligase. We describe a dominant developmental disorder resulting from germline missense CBL mutations, which is characterized by impaired growth, developmental delay, cryptorchidism and a predisposition to juvenile myelomonocytic leukemia (JMML). Some individuals experienced spontaneous regression of their JMML but developed vasculitis later in life. Importantly, JMML specimens from affected children show loss of the normal CBL allele through acquired isodisomy. Consistent with these genetic data, the common p.371Y>H altered Cbl protein induces cytokine-independent growth and constitutive phosphorylation of ERK, AKT and S6 only in hematopoietic cells in which normal Cbl expression is reduced by RNA interference. We conclude that germline CBL mutations have developmental, tumorigenic and functional consequences that resemble disorders that are caused by hyperactive Ras/Raf/MEK/ERK signaling and include neurofibromatosis type 1, Noonan syndrome, Costello syndrome, cardiofaciocutaneous syndrome and Legius syndrome.

Mutations in CBL occur frequently in juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia is an aggressive myeloproliferative disorder characterized by malignant transformation in the hematopoietic stem cell compartment with proliferation of differentiated progeny. Seventy-five percent of patients harbor mutations in the NF1, NRAS, KRAS, or PTPN11 genes, which encode components of Ras signaling networks. Using single nucleotide polymorphism arrays, we identified a region of 11q isodisomy that contains the CBL gene in several JMML samples, and subsequently identified CBL mutations in 27 of 159 JMML samples. Thirteen of these mutations alter codon Y371. In this report, we also demonstrate that CBL and RAS/PTPN11 mutations were mutually exclusive in these patients. Moreover, the exclusivity of CBL mutations with respect to other Ras pathway-associated mutations indicates that CBL may have a role in deregulating this key pathway in JMML.

WT1 gene expression: an excellent tool for monitoring minimal residual disease in 70% of acute myeloid leukaemia patients - results from a single-centre study.

Following induction chemotherapy for acute myeloid leukaemia (AML), sensitive determination of minimal residual disease (MRD) in patients achieving complete remission (CR) should enable the detection of early relapse and allow intervention at a more favourable stage than at overt relapse. We have determined the expression levels of the Wilms’ tumour gene (WT1) by real‐time quantitative polymerase chain reaction (RQ‐PCR) in peripheral blood and bone marrow in 133 newly diagnosed AML patients and compared them with those in healthy volunteers. At diagnosis, the WT1 level exceeded normal expression in 118 of 133 (89%) patients, and was high enough to allow for detection of a WT1 decrease of least 1000‐fold in 98 of 133 (74%) patients following induction therapy. Concomitant monitoring of fusion transcripts (PML‐RARα, AML1‐ETO, MLL‐MLL, CBFβ‐MYH11, or DEK‐CAN) in 38 patients identified different relationships between WT1 and fusion transcript levels, the AML1‐ETO group showing remarkably low levels of WT1 compared with fusion transcript. In 32 patients analysed longitudinally there was close concordance between relapse and increased WT1 levels. Parallel longitudinal monitoring of WT1 and fusion transcript showed close correlation in 18 of 18 patients. We conclude that WT1 expression by RQ‐PCR may be employed as a tool to detect MRD in the majority of fusion transcript‐negative AML patients.

Myelodysplastic syndrome, juvenile myelomonocytic leukemia, and acute myeloid leukemia associated with complete or partial monosomy 7

We reviewed the clinical features, treatment, and outcome of 100 children with myelodysplastic syndrome (MDS), juvenile myelomonocytic leukemia (JMML), and acute myeloid leukemia (AML) associated with complete monosomy 7 (−7) or deletion of the long arm of chromosome 7 (7q−). Patients with therapy-induced disease were excluded. The morphologic diagnoses according to modified FAB criteria were: MDS in 72 (refractory anemia (RA) in 11, RA with excess of blasts (RAEB) in eight, RAEB in transformation (RAEB-T) in 10, JMML in 43), and AML in 28. The median age at presentation was 2.8 years (range 2 months to 15 years), being lowest in JMML (1.1 year). Loss of chromosome 7 as the sole cytogenetic abnormality was observed in 75% of those with MDS compared with 32% of those with AML. Predisposing conditions (including familial MDS/AML) were found in 20%. Three-year survival was 82% in RA, 63% in RAEB, 45% in JMML, 34% in AML, and 8% in RAEB-T. Children with −7 alone had a superior survival than those with other cytogenetic abnormalities: this was solely due to a better survival in MDS (3-year survival 56 vs 24%). The reverse was found in AML (3-year survival 13% in −7 alone vs 44% in other cytogenetic groups). Stable disease for several years was documented in more than half the patients with RA or RAEB. Patients with RA, RAEB or JMML treated with bone marrow transplantation (BMT) without prior chemotherapy had a 3-year survival of 73%. The morphologic diagnosis was the strongest prognostic factor. Only patients with a diagnosis of JMML fitted what has previously been referred to as the monosomy 7 syndrome. Our data give no support to the concept of monosomy 7 as a distinct syndrome.