Thrombocytosis in children and adolescents-classification, diagnostic approach, and clinical management.

Secondary thrombocytosis is a frequent secondary finding in childhood infection and inflammation. Primary hereditary thrombocytosis may be caused by germline mutations within the genes encoding key regulators of thrombopoiesis, i.e., thrombopoietin (THPO) and its receptor c-MPL (MPL) or the receptor's effector kinase Januskinase2 (JAK2). Furthermore, somatic mutations in JAK2, MPL, and in the gene-encoding calreticulin (CALR) have been described to act as driver mutations within the so-called Philadelphia-negative myeloproliferative neoplasms (MPNs), namely essential thrombocythemia (ET), polycythemia vera (PV), and primary myelofibrosis (PMF). Increasing knowledge on the molecular mechanisms and on the clinical complications of these diseases is reflected by the WHO diagnostic criteria and European LeukemiaNet (ELN) recommendations on the management of adult MPN. However, data on childhood thrombocytosis are rare, and no consensus guidelines for pediatric thrombocytosis exist. Current literature has highlighted differences in the epidemiology and molecular pathogenesis of childhood thrombocytosis as compared to adults. Furthermore, age-dependent complications and pharmacological specificities suggest that recommendations tailored to the pediatric population are necessary in clinical practice. Here we summarize literature on classification, diagnostics, and clinical management of childhood thrombocytosis.

Radiosensitization by histone deacetylase inhibition in an osteosarcoma mouse model.

BACKGROUND: Osteosarcomas (OS) are highly malignant and radioresistant tumors. Histone deacetylase inhibitors (HDACi) constitute a novel class of anticancer agents. We sought to investigate the effect of combined treatment with suberoylanilide hydroxamic acid (SAHA) and radiotherapy in OS in vivo. METHODS: Clonogenic survival of human OS cell lines as well as tumor growth delay of OS xenografts were tested after treatment with either vehicle, radiotherapy (XRT), SAHA, or XRT and SAHA. Tumor proliferation, necrosis, microvascular density, apoptosis, and p53/p21 were monitored by immunohistochemistry. The CD95 pathway was performed by flow cytometry, caspase (3/7/8) activity measurements, and functional inhibition of CD95 death signaling. RESULTS: Combined treatment with SAHA and XRT markedly reduced the surviving fraction of OS cells as compared to XRT alone. Likewise, dual therapy significantly inhibited OS tumor growth in vivo as compared to XRT alone, reflected by reduced tumor proliferation, impaired angiogenesis, and increased apoptosis. Addition of HDACi to XRT led to elevated p53, p21, CD95, and CD95L expression. Inhibition of CD95 signaling reduced HDACi- and XRT-induced apoptosis. CONCLUSION: Our data show that HDACi increases the radiosensitivity of osteosarcoma cells at least in part via ligand-induced apoptosis. HDACi thus emerge as potentially useful treatment components of OS.

Increased efficiency of mRNA 3' end formation: a new genetic mechanism contributing to hereditary thrombophilia.

The G-->A mutation at position 20210 of the prothrombin or coagulation factor II gene (F2) represents a common genetic risk factor for the occurrence of thromboembolic events. This mutation affects the 3'-terminal nucleotide of the 3' untranslated region (UTR) of the mRNA and causes elevated prothrombin plasma concentrations by an unknown mechanism. Here, we show that the mutation does not affect the amount of pre-mRNA, the site of 3' end cleavage or the length of the poly(A) tail of the mature mRNA. Rather, we demonstrate that the physiological F2 3' end cleavage signal is inefficient and that F2 20210 G-->A represents a gain-of-function mutation, causing increased cleavage site recognition, increased 3' end processing and increased mRNA accumulation and protein synthesis. Enhanced mRNA 3' end formation efficiency emerges as a novel principle causing a genetic disorder and explains the role of the F2 20210 G-->A mutation in the pathogenesis of thrombophilia. This work also illustrates the pathophysiologic importance of quantitatively minor aberrations of RNA metabolism.

Hb Santa Juana (ß 108(G10) Asn > Ser): a low oxygen affinity hemoglobin variant in a family of Bosnian background.

We present a family that carries the ß-hemoglobin variant Hb Santa Juana (HBB:c.326A>G, ß 108(G10) Asn>Ser), also known as Hb Serres, in three generations. All affected family members had an anomal hemoglobin fraction as detected by HPLC but normal blood count without evidence of anemia or hemolysis. Oxygen affinity (p50 (O2) = 31.9-40.4 mmHg) was decreased in all probands, compared to 24.9-28.1 mmHg in unaffected individuals. Clinical symptoms likely related to the hemoglobin variant were cyanosis during anaesthesia, while other complaints such as shortness of breath or dizziness were less clearly linked with the hemoglobin variant.

The beta thalassaemia trait in Jamaica.

The objective of this study was to review the prevalence and features of the beta thalassaemia trait in Jamaican populations. Screening of 221,306 newborns over the last 46 years has given an indication of the distribution and prevalence of beta thalassaemia genes, and screening of 16,612 senior school students in Manchester parish, central Jamaica, has provided their haematological features. The prevalence of the beta thalassaemia trait predicted from double heterozygotes was 0.8% of 100,000 babies in Kingston, 0.9% of 121,306 newborns in southwest Jamaica, and 0.9% of school students in Manchester. Mild beta+ thalassaemia variants (-88 C>T, -29 A>G, -90 C>T, polyA T>C) accounted for 75% of Kingston newborns, 76% of newborns in southwest Jamaica, and 89% of Manchester students. Severe beta+ thalassaemia variants were uncommon. Betao thalassaemia variants occurred in 43 patients and resulted from 11 different variants of which the IVSII-849 A>G accounted for 25 (58%) subjects. Red cell indices in IVSII-781 C>G did not differ significantly from HbAA, and this is probably a harmless polymorphism rather than a form of beta+ thalassaemia; the removal of 6 cases in school screening had a minimal effect on the frequency of the beta thalassaemia trait. Red cell indices in the beta+ and betao thalassaemia traits followed established patterns, although both were associated with increased HbF levels. The benign nature of beta+ thalassaemia genes in Jamaica means that cases of sickle cell-beta+ thalassaemia are likely to be overlooked, and important clinical questions such as the role of pneumococcal prophylaxis remain to be answered.

Suberoylanilide hydroxamic acid affects γH2AX expression in osteosarcoma, atypical teratoid rhabdoid tumor and normal tissue cell lines after irradiation.

PURPOSE: Osteosarcoma and atypical teratoid rhabdoid tumors are tumor entities with varying response to common standard therapy protocols. Histone acetylation affects chromatin structure and gene expression which are considered to influence radiation sensitivity. The aim of this study was to investigate the effect of the combination therapy with the histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA) and irradiation on atypical teratoid rhabdoid tumors and osteosarcoma compared to normal tissue cell lines. METHODS: Clonogenic assay was used to determine cell survival. DNA double-strand breaks (DSB) were examined by pulsed-field electrophoresis (PFGE) as well as by γH2AX immunostaining involving flow cytometry, fluorescence microscopy, and immunoblot analysis. RESULTS: SAHA lead to an increased radiosensitivity in tumor but not in normal tissue cell lines. γH2AX expression as an indicator for DSB was significantly increased when SAHA was applied 24 h before irradiation to the sarcoma cell cultures. In contrast, γH2AX expression in the normal tissue cell lines was significantly reduced when irradiation was combined with SAHA. Analysis of initial DNA fragmentation and fragment rejoining by PFGE, however, did not reveal differences in response to the SAHA pretreatment for either cell type. CONCLUSION: SAHA increases radiosensitivity in tumor but not normal tissue cell lines. The increased H2AX phosphorylation status of the SAHA-treated tumor cells post irradiation likely reflects its delayed dephosphorylation within the DNA damage signal decay rather than chromatin acetylation-dependent differences in the overall efficacy of DSB induction and rejoining. The results support the hypothesis that combining SAHA with irradiation may provide a promising strategy in the treatment of solid tumors.

The haematology of Jamaicans: red cell indices in HbAA, HbAS, HbAC, and HbA-HPFH genotypes.

Based in the parish of Manchester in central Jamaica, the Manchester Project offered free detection of haemoglobin genotype to senior classes in 15 secondary schools between 2008 and 2013. Restricting the database to 15,103 students aged 15.0-19.9 years provided an opportunity to examine the red cell characteristics of the different haemoglobin genotypes, including normal (HbAA) in 85.0%, the sickle cell trait (HbAS) in 9.7%, HbC trait (HbAC) in 3.5% and hereditary persistence of foetal haemoglobin (HbA-HPFH) in 0.4%. Compared to the normal HbAA phenotype, HbAS had significantly increased mean cell haemoglobin concentration (MCHC), red cell count (RBC), and red cell distribution width (RDW) and decreased mean cell volume (MCV) and mean cell haemoglobin (MCH), these differences being even more marked in HbAC. Compared to HbAA, the HbA-HPFH had significantly increased RDW, but there were no consistent differences in other red cell indices, and there were no significant differences in haematological indices between the two common deletion HPFH variants, HPFH-1 and HPFH-2. Although these changes are unlikely to be clinically significant, they contribute to an understanding of the haematological spectrum of the common haemoglobin genotypes in peoples of African origin.

The proximal element of the beta globin locus control region is not functionally required in vivo.

In addition to local sequence elements the regulation of the high-level, development- and tissue-specific expression of the human beta globin gene cluster appears to require distant regulatory sequences which have been termed locus control region. In the chromatin of erythroid cells the locus control region is characterized by four DNaseI hypersensitive sites that are located 6-18 kb 5' of the epsilon globin gene. The definition of the sequences minimally required for locus control region activity is likely to further the understanding of its physiology and will be of interest for the development of somatic gene therapy strategies of the hemoglobinopathies. We present here the analysis of a family with a 3,030-bp deletion of sequences upstream of the epsilon globin gene including the most 3' locus control region element and cosegregating beta(0) thalassemia. The deletion is linked in cis to a structurally and functionally normal beta globin gene. The proximal element of the locus control region does not therefore appear to be necessary for beta globin gene activity in vivo.

Identification of a genetically defined ultra-high-risk group in relapsed pediatric T-lymphoblastic leukemia.

In the search for genes that define critical steps of relapse in pediatric T-cell acute lymphoblastic leukemia (T-ALL) and can serve as prognostic markers, we performed targeted sequencing of 313 leukemia-related genes in 214 patients: 67 samples collected at the time of relapse and 147 at initial diagnosis. As relapse-specific genetic events, we identified activating mutations in NT5C2 (P=0.0001, Fisher's exact test), inactivation of TP53 (P=0.0007, Fisher's exact test) and duplication of chr17:q11.2-24.3 (P=0.0068, Fisher's exact test) in 32/67 of T-ALL relapse samples. Alterations of TP53 were frequently homozygous events, which significantly correlated with higher rates of copy number alterations in other genes compared with wild-type TP53 (P=0.0004, Mann-Whitney's test). We subsequently focused on mutations with prognostic impact and identified genes governing DNA integrity (TP53, n=8; USP7, n=4; MSH6, n=4), having key roles in the RAS signaling pathway (KRAS, NRAS, n=8), as well as IL7R (n=4) and CNOT3 (n=4) to be exclusively mutated in fatal relapses. These markers recognize 24/49 patients with a second event. In 17 of these patients with mostly refractory relapse and dire need for efficient treatment, we identified candidate targets for personalized therapy with p53 reactivating compounds, MEK inhibitors or JAK/STAT-inhibitors that may be incorporated in future treatment strategies.

Genomic profiling of Acute lymphoblastic leukemia in ataxia telangiectasia patients reveals tight link between ATM mutations and chromothripsis.

Recent developments in sequencing technologies led to the discovery of a novel form of genomic instability, termed chromothripsis. This catastrophic genomic event, involved in tumorigenesis, is characterized by tens to hundreds of simultaneously acquired locally clustered rearrangements on one chromosome. We hypothesized that leukemias developing in individuals with Ataxia Telangiectasia, who are born with two mutated copies of the ATM gene, an essential guardian of genome stability, would show a higher prevalence of chromothripsis due to the associated defect in DNA double-strand break repair. Using whole-genome sequencing, fluorescence in situ hybridization and RNA sequencing, we characterized the genomic landscape of Acute Lymphoblastic Leukemia (ALL) arising in patients with Ataxia Telangiectasia. We detected a high frequency of chromothriptic events in these tumors, specifically on acrocentric chromosomes, as compared with tumors from individuals with other types of DNA repair syndromes (27 cases total, 10 with Ataxia Telangiectasia). Our data suggest that the genomic landscape of Ataxia Telangiectasia ALL is clearly distinct from that of sporadic ALL. Mechanistically, short telomeres and compromised DNA damage response in cells of Ataxia Telangiectasia patients may be linked with frequent chromothripsis. Furthermore, we show that ATM loss is associated with increased chromothripsis prevalence in additional tumor entities.

The prothrombin 20209 C-->T mutation in Jewish-Moroccan Caucasians: molecular analysis of gain-of-function of 3' end processing.

BACKGROUND: Mutations of the 3' end mRNA-processing signal of the prothrombin (F2) gene have been reported to cause elevated F2 plasma concentrations, thrombosis, and complications of pregnancy. Whereas the common F2 20210*A mutation is almost exclusively found in Caucasians, the F2 20209*T mutation has been reported in Afro-Americans and Afro-Caribbeans only. PATIENTS AND METHODS: Using LightCycler technology, three unrelated Jewish-Moroccan patients tested for obstetric complications were found to be carriers of the F2 20209*T allele. A detailed molecular analysis was performed to identify the functional impact of this mutation. RESULTS: We report three unrelated women of Jewish-Moroccan origin with a F2 20209*T mutation and fetal loss or infertility. The functional analysis revealed that the F2 20209*T mutation stimulates 3' end processing and up-regulates prothrombin protein expression as assessed by a highly sensitive luminescence-based reporter system. CONCLUSIONS: This is the first report of 20209*T in Caucasians, and functional analysis demonstrates that F2 20209*T falls into a general category of mutations of the F2 gene, which may possibly contribute to thrombophilia and complications of pregnancy by interfering with a tightly balanced architecture of non-canonical F2 3' end formation signals.

The polymerase chain reaction: a new tool for the detection of minimal residual disease in haematological malignancies.

The polymerase chain reaction (PCR) is a novel technique for the in vitro amplification of specific short DNA fragments, which permits a selective and up to 10(7) fold enrichment of the target sequence. The method is increasingly being used for the molecular genetic analysis of hereditary, infectious and neoplastic disorders. The use of PCR for the detection of minimal residual disease in particular types of leukaemia or lymphoma, such as chronic myelogenous leukaemia expressing specific BCR/ABL-RNA and follicular non-Hodgkin lymphoma with the chromosomal translocation t(14;18) are reviewed. In acute lymphoblastic leukaemia clone-specific sequences from rearranged antigen receptor genes may be molecular markers suitable for amplification. Although PCR holds great promise for "molecular" staging and follow-up, several technical problems have to be kept in mind, and the clinical relevance of PCR-based evidence of minimal residual disease in haematological malignancies requires further investigation.

Increased rate of factor V Leiden mutation in patients with cerebral venous thrombosis.

We investigated the association between cerebral venous thrombosis and hereditary resistance to activated protein C (APC) in 12 consecutive German patients with non-fatal cerebral venous thrombosis and in 187 controls without a history of thrombotic disorder. Three patients (25%) had a mutation in the factor V Leiden gene against only one subject in the control group. This difference was significant (P < 0.05), with an odds ratio of 11.7 (1.5-87; 95% confidence interval). Two patients carrying the mutation had additional common risk factors for thrombosis, and 2 had a positive family history of thromboembolism. We conclude that inherited APC resistance by a mutation in factor V Leiden is an important risk factor in non-fatal cerebral venous thrombosis. We recommend testing for APC resistance and, if abnormal for factor V Leiden mutation in patients with cerebral venous thrombosis.

The favorable effect of activating NOTCH1 receptor mutations on long-term outcome in T-ALL patients treated on the ALL-BFM 2000 protocol can be separated from FBXW7 loss of function.

Precursor T-cell acute lymphoblastic leukemia (T-ALL) remains an important challenge in pediatric oncology. Because of the particularly poor prognosis of relapses, it is vital to identify molecular risk factors allowing early and effective treatment stratification. Activating NOTCH1 mutations signify a favorable prognosis in patients treated on ALL-BFM protocols. We have now tested if NOTCH pathway activation at different steps has similar clinical effects and if multiple mutations in this pathway function synergistically. Analysis of a validation set of 151 T-ALL patients and of the total cohort of 301 patients confirms the low relapse rate generally and the overall favorable effect of activating NOTCH1 mutations. Subgroup analysis shows that the NOTCH1 effect in ALL-BFM is restricted to patients with rapid early treatment response. Inactivation of the ubiquitin ligase FBXW7 is associated with rapid early treatment response and synergizes with NOTCH1 receptor activation. However, the effect of FBXW7 inactivation is separable from NOTCH1 activation by not synergizing with NOTCH1 mutations in predicting favorable long-term outcome, which can probably be explained by the interaction of FBXW7 with other clients. Finally, the comparison with other European protocols suggests that the NOTCH effect is treatment dependent generally and may depend on the intensity of central nervous system-directed therapy specifically.

[Genetic modifiers of homozygous sickle cell disease]. / Genetische modulierende Faktoren der Klinik der homozygoten Sichelzellkrankheit.

Homozygous sickle cell (HbSS) disease is paradigmatic for the complex influence of genetic modifiers of a monogenic disease. The genetically determined variability of HbF concentration has a strong impact on the clinical phenotype. The pharmacologically induced increase of HbF leads to a reduced morbidity which demonstrates that the knowledge of genetic modifiers enables the development of new therapeutic strategies. The presence of alpha-thalassemia also ameliorates the disease phenotype albeit not to the same extent as HbF does. Both factors, HbF and alpha-thalassemia are insufficient to explain the clinical variability of HbSS disease. The introduction of genome analysis has now provided the tools to identify relevant gene loci that will likely be helpful in estimating the probability of severe complications such as the occurrence of stroke. Following the validation in prospective studies, the subtle analysis of genetic modifiers will therefore influence the management of patients with sickle cell disease.

[Beta thalassemia: molecular pathogenesis and clinical variability]. / beta-Thalassämie: Molekulare Pathogenese und klinische Variabilität.

Clinically, homozygous beta-thalassaemia is characterised by a severe anaemia requiring regular transfusion therapy in most patients. However, there is a marked clinical variability ranging from this severe picture to the virtual absence of symptoms and haematological abnormalities. Biochemically, beta-globin synthesis in the erythroid precursors of the bone marrow is reduced or absent resulting in a relative excess of insoluble alpha-globin chains and dyserythropoiesis. The molecular genetics of this disorder is highly variable involving a multitude of different mutations of the beta-globin gene. These mutations can inactivate gene expression at all levels on its way from DNA to mature haemoglobin. The clinical picture is largely determined by the type of mutations inherited. Additionally the degree of alpha-globin chain excess can be influenced by the co-inheritance of alpha-thalassaemia or mutations resulting in the hereditary persistence of fetal globin synthesis (HPFH). This review discusses the relationship between the molecular defect and the clinical picture of patients with beta-thalassaemia.

mRNA Metabolism and hereditary disorders: a tale of surveillance and escape.

The exploration of the molecular origin of hereditary diseases focused on genes and proteins for many years. Recently, mRNA has gained increasing attention. Most human genes contain introns and a considerable proportion of transcripts are not only alternatively spliced but also regulated posttranscriptionally in manifold ways. mRNA processing as well as a complex network of interactions between the steps of gene expression and associated quality control mechanisms are guided by a multitude of regulative mRNA sequence elements. Therefore it is not surprising that mutations of such elements can cause or modify human disease. The purpose of this review is the illustration of principles of physiological and dysregulated mRNA metabolism as well as a survey of new analytical tools and therapeutic approaches.

Relationship of foetal haemoglobin levels and beta s haplotypes in homozygous sickle cell disease.

The foetal haemoglobin (HbF) levels and the haplotypes of beta s chromosomes in sickle cell anaemia patients in Nigeria were evaluated. The mean HbF level was 5.9 +/- 3.8% with a range of 0.9-16.7%. 80% of the patients had HbF values below 8% and 94% had HbF levels below 10%. No significant difference in haematological parameters was seen between those with less than 2% HbF and those with greater than 8% HbF. The presence (+) or absence (-) of eight restriction endonuclease enzyme sites within the beta s globin gene cluster (haplotype) on chromosome 11 were mapped. The common haplotype (- - - - + + - +) in 97% of the chromosomes examined closely correlates with the low levels of foetal haemoglobin generally observed in sickle cell patients in the same population.

[Monitoring pregnant patients from risk countries with sickle cell disease and thalassemia. Clinical aspects, screening and prenatal diagnosis]. / Betreuung von Schwangeren aus Risikoländern mit Sichelzellerkrankungen und Thalassämien. Klinik, Screening und Pränatale Diagnostik.

At the present time, about 3.5 million people from Turkey, Greece, Italy, the Middle East, Africa and Asia are living in Germany. They are potential carriers of beta-thalassaemia and haemoglobinopathies such as sickle cell disease. These diseases are new for most of us and represent a challenge to physicians, taking care of these patients. Not only do we have to learn about the clinical problems of homozygous patients and how to handle them, we also have to become acquainted with the problems related to the heterozygous carrier stage. The large number of asymptomatic pregnant carriers of beta-globin anomalies is a particular challenge for obstetricians. They need to identify carriers through haemoglobin electrophoresis screening, inform the carrier about the meaning of being a carrier, screen the woman's partner, refer for genetic counselling and suggest and explain prenatal diagnosis in case the partner is also a carrier. There is as yet no cure for thalassaemia and sickle cell disease, except for bone marrow transplantation in a few selected cases. Therefore, prenatal diagnosis presents a valuable method of preventing severe chronic diseases. Screening does not only allow genetic counselling, the information gained has also clinical implications for carriers of beta-thalassaemia. In this paper a summary is given of the pathophysiological and clinical features of thalassaemia and sickle cell disease and molecular biology methods to diagnose thalassaemias and sickle cell disease are discussed. In addition, a screening programme for pregnant women from countries at risk is suggested to enable physicians to give optimal care and initiate prenatal diagnosis.

[The molecular basis of hereditary persistence of fetal hemoglobin (HPFH). Clinical importance of the hemoglobin switching mechanism with special reference to Corfu delta beta zero thalassemia]. / Die molekulare Grundlage der hereditären Persistenz fetalen Hämoglobins (HPFH) und des Hämoglobinschaltmechanismus. Ein Beitrag zur klinischen Bedeutung unter besonderer Berücksichtigung der Corfu-delta beta zero-Thalassämie.

The haemoglobinopathies are a group of autosomal recessively inherited diseases that are common among populations in the Mediterranean, in Africa and large parts of Asia. In Germany, the immigration of people from those parts of the world has resulted in an increased occurrence in particular of beta thalassaemia. Homozygous patients usually become transfusion dependent during the first year of life as the excess of alpha globin chains in the erythroid precursors causes a most severe dyserythropoietic anaemia. Genetic determinants that diminish the alpha globin chain excess are thus clinically significant. Here, we describe the molecular genetic changes that result in an increased gamma globin gene expression and hende in a binding of alpha globin chains as HbF. We discuss the significance of those changes for the clinical course of beta thalassaemia and for the elucidation of the ontogenetic processes of gene regulation during the perinatal haemoglobin switch.