Addiction to DUSP1 protects JAK2V617F-driven polycythemia vera progenitors against inflammatory stress and DNA damage, allowing chronic proliferation.

Inflammatory and oncogenic signaling converge in disease evolution of BCR-ABL-negative myeloproliferative neoplasms, clonal hematopoietic stem cell disorders characterized by gain-of-function mutation in JAK2 kinase (JAK2V617F), with highest prevalence in patients with polycythemia vera (PV). Despite the high risk, DNA-damaging inflammatory microenvironment, PV progenitors tend to preserve their genomic stability over decades until their progression to post-PV myelofibrosis/acute myeloid leukemia. Using induced pluripotent stem cells-derived CD34+ progenitor-enriched cultures from JAK2V617F+ PV patient and from JAK2 wild-type healthy control, CRISPR-modified HEL cells and patients' bone marrow sections from different disease stages, we demonstrate that JAK2V617F induces an intrinsic IFNγ- and NF-κB-associated inflammatory program, while suppressing inflammation-evoked DNA damage both in vitro and in vivo. We show that cells with JAK2V617F tightly regulate levels of inflammatory cytokines-induced reactive oxygen species, do not fully activate the ATM/p53/p21waf1 checkpoint and p38/JNK MAPK stress pathway signaling when exposed to inflammatory cytokines, suppress DNA single-strand break repair genes' expression yet overexpress the dual-specificity phosphatase (DUSP) 1. RNAi-mediated knock-down and pharmacological inhibition of DUSP1, involved in p38/JNK deactivation, in HEL cells reveals growth addiction to DUSP1, consistent with enhanced DNA damage response and apoptosis in DUSP1-inhibited parental JAK2V617F+ cells, but not in CRISPR-modified JAK2 wild-type cells. Our results indicate that the JAK2V617F+ PV progenitors utilize DUSP1 activity as a protection mechanism against DNA damage accumulation, promoting their proliferation and survival in the inflammatory microenvironment, identifying DUSP1 as a potential therapeutic target in PV.

[Chronic myeloid leukemia--resistance to imatinib mesylate (Glivec)--literature review and personal experience]. / Chronická myeloidní leukémie--rezistence na imatinib mesylát (Glivec)--prehled literatury a vlastní zkusenosti.

Chronic myeloid leukemia (CML) is a myeloproliferative disorder characterized by an abnormal fusion gene BCR-ABL. BCR-ABL encodes a constitutively active Bcr-Abl tyrosine kinase, which is required and sufficient for cellular transformation. Bcr-Abl is, therefore, an ideal target for pharmacotherapy. Imatinib Mesylate (Glivec) is a specific inhibitor of Bcr-Abl kinase. Imatinib shows high efficiency and low toxicity in treatment of CML patients. The main problem of imatinib treatment is the development of resistance. The mechanisms of resistance can be divided into two groups. The first group is characterized by reactivation of Bcr-Abl kinase in spite of continual imatinib presence. This can be caused by BCR-ABL amplification, overexpression or mutation in Abl kinase domain. Imatinib might not even reach the target Bcr-Abl protein (possible causes: drug efflux or imatinib binding to alpha1-acid glycoprotein). In the second group of resistance mechanisms, the Bcr-Abl kinase is inhibited but the resistance is maintained by other signal transducers (e.g. Src kinases). Standard cytogenetics as well as assay evaluating the phosphorylation status of Bcr-Abl substrate and/or sequencing of Abl kinase transcript can be used to test the mechanism of resistance. Treatment of patients can be re-evaluated on the basis of the status of IM resistance.

Complex karyotypes in childhood acute lymphoblastic leukemia: cytogenetic and molecular cytogenetic study of 21 cases.

Cytogenetic and molecular cytogenetic analysis of 79 childhood acute lymphoblastic leukemias (ALL) revealed chromosomal abnormalities in 76 (96%). Complex karyotypes (a finding of three and more chromosomal aberrations in a karyotype) were identified in 21 (26.6%) out of 79 patients. In 11 patients, complex karyotypes have included common recurrent chromosomal abnormalities, such as translocation t(12;21) in seven cases, t(9;22) in two cases, one case with t(2;1;19) and another one with translocation involving 11q23. In 10 patients, miscellaneous abnormalities were detected. Five patients displayed hyperdiploidy (47 approximately 57 chromosomes), three patients complex karyotypes with deletions of 9p, one patient with two new complex translocations t(2;4;12;13) and t(7;11;20), and the last patient with dic(12;21). The evaluation of the frequency of the chromosomal breaks (>5 per chromosome) showed that chromosomes 2, 4, 5, 7, 9, 12, 13, and 21 were most frequently affected. Survival analysis revealed statistically significant unfavorable event-free survival (EFS) (P=0.013) and decreased overall survival in the group with complex karyotypes (n=21) compared with the other cases (n=58). The evaluation of overexpression profile revealed increased occurrence of double CD13/CD33 positivity in patients with common recurrent chromosomal abnormalities (in 70% of cases); no such cases were registered in the other group (P<0.01).

Non-anemic homozygous beta(o) thalassemia in an African-American family: association of high fetal hemoglobin levels with beta thalassemia alleles.

We have studied a four-generation (23 subjects) African-American family with beta(o) thalassemia and high fetal hemoglobin (HbF) levels. The beta(o) thalassemia in this family is due to the splicing site mutation, beta IVS2+1G-->A, that leads to aberrant mRNA processing and the absence of beta globin. Two members of this family are homozygous for beta(o) thalassemia and are non-anemic. All family members who are heterozygous for the beta IVS2+1G-->A mutation have elevated HbF, with the exception of two individuals who also have severe alpha-globin chain deficiency. We excluded linkage with the hereditary persistence of fetal hemoglobin loci on chromosomes 6 and X. We also excluded the presence of all previously described determinants in the beta globin gene cluster associated with elevated HbF production. One thalassemia allele is in the Cameroon-like (HS2)/Benin-like beta globin gene cluster haplotype, and the other is in the Senegal-like (HS2)/Benin-like beta globin gene cluster haplotype. We speculate that in the homozygotes, those erythroid cells that express low to absent levels of gamma globin are selectively destroyed. In contrast, in the heterozygotes, the presence of the normal beta globin allele would ameliorate the globin chain imbalance and thus allow survival of erythroid cells that express the abnormal transcript, leading to a typical beta(o) thalassemia phenotype. Thus, the heterocellular gamma globin expression together with in vivo preferential survival of HbF-containing erythroid cells ameliorates Cooley's anemia in the beta(o) thalassemia homozygotes. It remains to be determined what sequences linked to each thalassemia allele and what trans-acting factors contribute to high HbF levels.

Mouse model of congenital polycythemia: Homologous replacement of murine gene by mutant human erythropoietin receptor gene.

Mutations causing truncations of the cytoplasmic domain of the human erythropoietin receptor (EPOR) result in a dominantly inherited disorder-primary familial congenital polycythemia. This disorder is characterized by increased numbers of erythrocytes (polycythemia) and by in vitro hypersensitivity of erythroid precursors to erythropoietin. The consequences of EPOR truncation in nonerythroid tissues are unknown. We replaced the murine EPOR gene with a wild-type human EPOR gene and a mutant human EPOR gene that we initially identified in a patient with polycythemia. This mutation leads to an EPOR truncated after the first tyrosine residue of the intracellular domain. Mice heterozygous for this mutant allele and a wild-type human EPOR allele mimicked the human disorder. Interestingly, mice that were homozygous for the mutant human allele were severely polycythemic but viable. Our results provide a model for functional studies of EPOR-triggered signaling pathways in erythropoiesis. These animals can now be used to investigate the molecular pathophysiology of this gain-of-function EPOR mutation in erythroid tissue and in those nonerythroid tissues that express EPOR.

Lessons to better understanding of hypoxia sensing. Acquired and congenital mutations resulting in polycythemia.

Adaptation of the organism to hypoxia has profound effect on multiple tissues including regulation of erythropoiesis, vasculogenesis, a proper regulation of embryogenesis as well as other functions. The elucidation of those congenital or acquired mutations giving rise to disease states affecting physiological systems devoted to oxygen homeostasis provides not only a practical diagnostic and potential therapeutic target, but also allows to identify the essential, non-redundant physiological pathways that may be hitherto unknown. The erythropoietin gene was the first gene expression found to be upregulated by hypoxia; the mechanism of this regulation lead to our current understanding of hypoxia sensing. Thus it is appropriate that the disorders resulting from augmented erythropoiesis are subject of this review.

Cryptic splice site activation during RNA processing of MLL/AF4 chimeric transcripts in infants with t(4;11) positive ALL.

Co-expression of multiple variants of the MLL/AF4 fusion transcript is a common phenomenon in patients with acute lymphoblastic leukemia (ALL) with t(4;11)(q21;q23). Different transcriptional and post-transcriptional mechanisms were found to contribute to the heterogeneity of the chimeric transcripts. Multiple splice variants are generated by utilizing alternative splice sites that result in the joining of different MLL-exons within the breakpoint cluster region to one of three exons in the AF4 fusion partner. To address the question of how splice site selection occurs during RNA processing, we investigated der(11) transcripts in 10 infants with t(4;11) positive ALL. Specific RT-PCR products were analyzed by Southern blot hybridization, SSCP, endonuclease digestion, cloning and sequencing. In patients co-expressing as many as six different chimeric mRNA species, activation of cryptic splice sites has been detected in MLL-exons 8 and 10. This led to the formation of four novel transcript variants, three of which maintained open reading frames (ORFs). Patients with cryptic donor site activation in MLL-exon 8 did not have any MLL-exon 8/AF4 transcripts using the authentic 5' splice site, although this site is 100% homologous to the consensus sequence. However, since MLL-exon 8 does not end in-phase, the use of the authentic splice site would result in loss of the ORF of the fusion message. The activated cryptic splicing sites are located in the vicinity of the polypurine stretches present in MLL-exons 8 and 10, which are known to function as splicing enhancers recognized by SR proteins. We postulate that both the nonsense-mediated decay eliminating correctly spliced MLL-exon 8/AF4 mRNAs and activation of suboptimal splicing sites contribute to the diversity of MLL/AF4 RNA species.

Full-length human L1 insertions retain the capacity for high frequency retrotransposition in cultured cells.

Functional L1 elements are autonomous retrotransposons that can insert into human genes and cause disease. To date, 10 of 12 known L1 retrotranspositions into human genes have been found to be 5"-truncated and incapable of further retrotransposition. Here we report the nucleotide sequences of the two full-length L1 elements, L1beta-thal and L1RP, that have inserted into the beta-globin and retinitis pigmentosa-2 (RP2) genes, respectively. L1beta-thal is 99. 4% identical to a consensus sequence of active human L1s, while L1RP is 99.9% identical. Both elements retain impressive capacity for high frequency retrotransposition in cultured HeLa cells. Indeed, L1RP is the most active L1 isolated to date. Our data indicate that not all L1 insertions into human genes are 'dead on arrival'. Our findings also lend further credence to the concept of cis preference, that the proteins encoded by a particular L1 preferentially act upon their encoding RNA as opposed to other L1 RNAs.

[New beta0-thalassaemic insertion mutation (CD 7/8, +G) in a Slovak family, associated with the Mediterranean haplotype IX]. / Nová beta0-talasemická posunová mutace (CD 7/8, +G) ve slovenské rodine asociovaná s mediteránním haplotypem IX.

The authors describe a newly identified beta0-thalassaemic mutation found in two subjects from two generations of a Slovak family. The beta0-thalassaemic allele developed by insertion of one nucleotide (+G, CD 7/8) into the first exon of the beta-globin gene. The mutation causes a shift of the open globin reading frame which leads to the development of a terminal codon in codon 22. The thalassaemic allele is associated with the mediterranean haplotype IX. The mutation has in both heterozygotes the phenotype of beta0-thalassaemia minor with a slightly elevated level of HbF.

[Hemoglobin Sydney--alpha beta 2 67 (E11) Val-Ala and hemoglobin Olomouc alpha 2 beta 2 86 (F 2) Ala-Asp in Czech families. DNA sequence analysis for a more accurate diagnosis of hemoglobinopathies]. / Hemoglobin Sydney--alpha 2 beta 2 67 (E11) Val-Ala a hemoglobin Olomouc alpha 2 beta 2 86 (F 2) Ala-Asp v ceských rodinách. Prínos sekvenacní analýzy DNA pro zpresnení diagnostiky hemoglobinopatií.

The paper demonstrates the importance of sequence analysis of DNA for the identification of Hb-Sydney [alpha2-beta2 67 (E11) Val-Ala]. The latter was considered erroneously, based on results of biochemical analyses to be Hb-M-Milwaukee [alpha2 beta2 67 (E 11) Val-Glu]. With the unstable Hb-Sydney correspond also phenotypical manifestations of disease (haemolytic anaemia with Heinz bodies in red blood cells). Sequence analysis of DNA of patients with Hb-Olomouc [alpha 2 beta 2 (F 2) Ala-Asp] revealed that mutation of Ala-Asp in position 86 (F 2) of the beta globin chain is coded by mutation C-->A (GCC-GAC).

[Hemoglobin Haná or alpha 2 beta 2 63 (E7) His-Asn: a new unstable hemoglobin variant with a paradoxically different clinical manifestations in smokers and non-smokers in the same family]. / Hemoglobin Haná nebo alpha 2 beta 2 63 (E7) His-Asn: nová nestabilní varianta hemoglobinu s paradoxne rozdílnou klinickou manifestací u kuráku a nekuráku téze rodiny.

The authors describe the identification and the clinical manifestations of a new structural variant of haemoglobin found in three subjects from two generations of a Moravian family. It is manifested by mild haemolytic anaemia with Heinz bodies in the proband and a slightly elevated value of methaemoglobin. The sequential analysis of the beta-globin gene provided evidence that the cause is mutation CAT-AAT in codon 63 which leads to the exchange of distal histidine /E7/ for asparagine. The ratio of beta X:beta A is 38:62. The mother with the same mutation is asymptomatic. The relative amount of beta X:beta A mRNA transcripts in mother and daughter are equal. This indicates that the clinical differences are not due to a different gene expression. The mother is a heavy smoker with an elevated CO-Hb level that probably protect the mutant against oxidative denaturation and increases thus the stability of Hb-Haná. The authors discuss also the finding of two abnormal stripes assessed by three electrophoretic methods.

[Interferon-alpha in the treatment of patients with chronic myeloid leukemia]. / Interferon alfa v lécbe nemocných s chronickou myeloidní leukémií.

A retrospective analysis of the treatment with Interferon alpha in 18 patients with Ph positive chronic myeloid leukaemia is presented and compared with the results of peroral chemotherapy with Hydroxyurea or Busulphan in 20 patients. Patients treated with Interferon were significantly younger than the control group (median age 40.5 versus 55.5) (p = 0.01) and were followed-up for shorter period of time (median 10.5 months versus 36.5 months) ( p = 0.002), but did not differ in other parameters. Despite the shorter period of observation and treatment, significantly more complete haematological remissions were achieved with Interferon (86%) than with peroral chemotherapy (25%) (p = 0.03). 6 major and 2 minor (44%) cytogenetic responses were observed after Interferon, despite the fact that 8 patients had been treated for less than one year. Interferon was not the optimal therapy in the patients with additional or complex cytogenetic abnormalities at the time of diagnosis, which were the most significant negative prognostic factor. In general, our short-term results confirm the importance and effectiveness of Interferon in the patient with CML providing the therapy was started early, with an effective dose and with simultaneous cytogenetic monitoring. Longer observation of the patients is needed to confirm the impact of Interferon on the survival of patients.

[Unstable Santa Ana hemoglobin or alpha 2 beta 2 88 (F4) Leu-Pro detected in a Slovak girl]. / Nestabilní hemoglobin Santa Ana nebo alpha 2 beta 2 88 (F4) Leu-Pro identifikovaný u slovenské dívky.

The unstable haemoglobin variant Ana (alpha 2 beta 2 88 (F4) Leu-Pro) was identified to cause haemolysis in a 10-year-old Slovak girl. She was followed for haemolytic anaemia symptoms since two years of age. Clinical signs are hepatosplenomegaly and moderate haemolytic anaemia not requiring blood transfusions. It is the first case of an unstable haemoglobinopathy found in Slovak Republic as far as we know. Hypothesis of 'de novo' origin of the mutation in the propositus is supported by the parents' and brother's laboratory findings.

[Structural variants in hemoglobin occurring in the Czech Republic]. / Strukturní varianty hemoglobinu nalezené v Ceské republice.

The authors present a review of clinical and laboratory findings of seven in the Czech Republic hitherto diagnosed structural haemoglobin variants. Unstable variants are found most frequently: Hb-Köln, Hb-St. Louis, Hb-Nottingham, Hb-E and Hb-Hradec Králové. The variant Hb-Hradec Králové (Hb-HK) or alpha 2 beta 2 115 (G17) Ala-Asp was newly detected. The great instability of Hb-HK chains makes classical diagnosis of Hb-pathy impossible. It was possible to identify it only at a molecular genetic level. A manifestation of Hb-HK instability is also the thalassaemic feature of the disease and the formation of Heinz bodies from free chains. The only representative of haemoglobins with a high oxygen affinity identified in this country was newly detected. It was given the name Hb-Olomouc or alpha 2 beta 2 86 (F2) Ala-Asp. This haemoglobin variant leads to erythrocytosis in father and son and the same clinical manifestations were recently described also in Japan. The last structural variant of haemoglobin found in this country is Hb-M Milwaukee or alpha 2 beta 2 67 (E11) Val-Glu which in our patients is manifested rather by haemolysis with formation of Heinz bodies than classical cyanosis. The cause of instability of Hb-M in our patients is not known. Hb-S was not diagnosed so far in the Czech Republic.

Hb Nottingham or alpha 2 beta 2 98 (FG5) Val-->Gly in a Czech child.

We report a fourth case of Hb Nottingham [alpha 2 beta 2 98 (FG5) Val-->Gly] observed in an 8-year-old girl in the Czech Republic with clinical and laboratory symptoms of severe hemolytic anemia. The unstable hemoglobin probably represents a de novo mutation, since the parents of the patient and the two siblings do not exhibit any hematological abnormalities. Splenectomy had a beneficial effect on the degree of hemolysis, as well as on the Hb level.

[Dominant beta-thalassemia alleles in the Czech and Slovak population (beta-thalassemia mutations in 112(T-A) and 121(G-T) codons and the unstable Hradec Králové hemoglobin or alpha 2 beta 2 115 (G17) Ala-Asp)]. / Dominantní beta-talasemické alely v ceské a slovenské populaci [beta-talasemické mutace v kodonech 112 (T-A) a 121 (G-T) a nestabilní hemoglobinová varianta Hradec Králové nebo alpha 2 beta 2 115 (G 17) Ala-Asp].

In four unrelated families of Czech and Slovak origin two nonsense dominant beta-thalassaemic alleles (CD 121 (G-T); CD 112 (T-A)) and in one family simple substitution in codon 115 (GCC-GAC) or alpha 2 beta 2 115 (G17) Ala-Asp HB-Hradec Králové were identified. Mutations in codons 112 and 115 were described for the first time. Phenotypic manifestation of beta-thal. intermedia was revealed in three families with CD 121 (G-T) and in a family with a mutation in CD 112, but the phenotypic manifestations differed markedly in individual subjects. Heinz bodies were detected in erythrocytes of the peripheral blood in two families. An exact explanation of phenotypic deviations in patients with the same mutation even within the same family were not obtained even in studies of alpha genes and the promoter area of the beta gene. The unstable variant of Hb-Hradec Králové is manifested in the mother and daughter by haemolytic anaemia with some traits of beta-thal. The authors discuss contemporary findings from the pathophysiology of recessive and dominant beta-thal. mutations and explain some of the phenotypic consequences. A relatively high incidence of dominant beta-thal. mutations in the Czech and Slovak Republic (4 of 12 families known world wide with a nonsense beta-thal. mutation in the 3rd exon) is explained by the absence of selective preference of these mutations in malaria infested areas as a result of serious clinical manifestations in heterozygotes. The haplotype in one of the families suggests a de novo origin of the mutation in CD 121.

Sickle cell anemia, sickle cell beta-thalassemia, and thalassemia major in Albania: characterization of mutations.

We have analyzed the hemoglobin abnormalities in nearly 50 Albanian patients with a significant hemoglobinopathy and included 37 relatives in this study. Sickle cell anemia (SS) is a common disorder; all 15 sickle cell anemia patients had the complications expected for this disease. The beta S haplotype was type 19 (Benin); alpha-thalassemia-2 was rare. Three beta-thalassemia alleles (IVS-I-110, G-->A; codon 39, C-->T; IVS-I-6, T-->C) were present in nearly 85% of the beta-thalassemia alleles; their frequencies were intermediate between those observed in the populations of neighboring countries. A few rare mutations were also found, which might have originated in India, Turkey, Macedonia, and Greece. Nearly all patients with Hb S-beta-thalassemia had the IVS-I-110 (G-->A) mutation. The frequencies of 11 beta-thalassemia mutations in 17 mostly Mediterranean countries have been reviewed.