Molecular characterization of V(D)J rearrangements in immature acute leukemias.

Early T-cell Precursor Acute Lymphoblastic Leukemia (ETP-ALL), T-Lymphoid/Myeloid Mixed Phenotype Acute Leukemia (T/M-MPAL), and Acute Myeloid Leukemia with minimal differentiation (AML-M0) are immature acute leukemias (AL) that present overlapping T-cell lymphoid and myeloid features at different degrees, with impact to disease classification. An interesting strategy to assess lymphoid lineage commitment and maturation is the analysis of V(D)J gene segment recombination, which can be applied to investigate leukemic cells in immature AL. Herein, we revisited 19 ETP-ALL, 8 T/M-MPAL, and 12 AML-M0 pediatric patients to characterize V(D)J rearrangement (V(D)J-r) profiles associated with other somatic alterations. V(D)J-r were identified in 74 %, 25 %, and 25 % of ETP-ALL, T/M-MPAL, and AML-M0, respectively. Forty-six percent of ETP-ALL harbored ≥ 3 V(D)J-r, while there was no more than one V(D)J-r per patient in AML-M0 and T/M-MPAL. TCRD was the most rearranged locus in ETPALL, but it was not rearranged in other AL. In ETP-ALL, N/KRAS mutations were associated with absence of V(D)J-r, while NF1 deletion was most frequent in patients with ≥ 3 V(D)J-r. Relapse and death occurred mainly in patients harboring one or no rearranged locus. Molecular characterization of V(D)J-r in our cohort indicates a distinct profile of ETP-ALL, compared to T/M-MPAL and AML-M0. Our findings also suggest that the clinical outcome of ETP-ALL patients may be affected by blast cell maturity, inferred from the number of rearranged TCR loci.

Acute promyelocytic leukemia in a long-standing HIV-positive patient: Case report and literature review.

The use of antiretroviral therapy has drastically improved the life quality and prognosis of people living with the human immunodeficiency virus (HIV). The risk of acute myeloid leukemia (AML) currently does not appear to be significantly increased compared to the general population. Acute promyelocytic leukemia (APL), infrequent in people with HIV, is a distinct subtype of AML with unique molecular pathogenesis, clinical manifestations, and treatment. Herein we describe a fatal case of APL hypogranular variant in an HIV-positive patient presenting with hyperleukocytosis. Also, we conducted a literature review of the ten cases reported so far.

Induced Pluripotent Stem Cells Enable Disease Modeling and Drug Screening in Calreticulin del52 and ins5 Myeloproliferative Neoplasms.

Mutations in the calreticulin (CALR) gene are seen in about 30% of essential thrombocythemia and primary myelofibrosis patients. To address the contribution of the human CALR mutants to the pathogenesis of myeloproliferative neoplasms (MPNs) in an endogenous context, we modeled the CALRdel52 and CALRins5 mutants by induced pluripotent stem cell (iPSC) technology using CD34+ progenitors from 4 patients. We describe here the generation of several clones of iPSC carrying heterozygous CALRdel52 or CALRins5 mutations. We showed that CALRdel52 induces a stronger increase in progenitors than CALRins5 and that both CALRdel52 and CALRins5 mutants favor an expansion of the megakaryocytic lineage. Moreover, we found that both CALRdel52 and CALRins5 mutants rendered colony forming unit-megakaryocyte (CFU-MK) independent from thrombopoietin (TPO), and promoted a mild constitutive activation level of signal transducer and activator of transcription 3 in megakaryocytes. Unexpectedly, a mild increase in the sensitivity of colony forming unit-granulocyte (CFU-G) to granulocyte-colony stimulating factor was also observed in iPSC CALRdel52 and CALRins5 compared with control iPSC. Moreover, CALRdel52-induced megakaryocytic spontaneous growth is more dependent on Janus kinase 2/phosphoinositide 3-kinase/extracellular signal-regulated kinase than TPO-mediated growth and opens a therapeutic window for treatments in CALR-mutated MPN. The iPSC models described here represent an interesting platform for testing newly developed inhibitors. Altogether, this study shows that CALR-mutated iPSC recapitulate MPN phenotypes in vitro and may be used for drug screening.

The pterocarpanquinone LQB­118 compound induces apoptosis of cytarabine­resistant acute myeloid leukemia cells.

Acute myeloid leukemia (AML) is a complex hematological disorder characterized by blockage of differentiation and high proliferation rates of myeloid progenitors. Anthracycline and cytarabine­based therapy has remained the standard treatment for AML over the last four decades. Although this treatment strategy has increased survival rates, patients often develop resistance to these drugs. Despite efforts to understand the mechanisms underlying cytarabine resistance, there have been few advances in the field. The present study developed an in vitro AML cell line model resistant to cytarabine (HL­60R), and identified chromosomal aberrations by karyotype evaluation and potential molecular mechanisms underlying chemoresistance. Cytarabine decreased cell viability, as determined by MTT assay, and induced cell death and cell cycle arrest in the parental HL­60 cell line, as revealed by Annexin V/propidium iodide (PI) staining and PI DNA incorporation, respectively, whereas no change was observed in the HL­60R cell line. In addition, the HL­60R cell line exhibited a higher tumorigenic capacity in vivo compared with the parental cell line. Notably, no reduction in tumor volume was detected in mice treated with cytarabine and inoculated with HL­60R cells. In addition, western blotting revealed that the protein expression levels of Bcl­2, X­linked inhibitor of apoptosis protein (XIAP) and c­Myc were upregulated in HL­60R cells compared with those in HL­60 cells, along with predominant nuclear localization of the p50 and p65 subunits of NF­κB in HL­60R cells. Furthermore, the antitumor effect of LQB­118 pterocarpanquinone was investigated; this compound induced apoptosis, a reduction in cell viability and a decrease in XIAP expression in cytarabine­resistant cells. Taken together, these data indicated that acquired cytarabine resistance in AML was a multifactorial process, involving chromosomal aberrations, and differential expression of apoptosis and cell proliferation signaling pathways. Furthermore, LQB­118 could be a potential alternative therapeutic approach to treat cytarabine­resistant leukemia cells.

TET2 haploinsufficiency alters reprogramming into induced pluripotent stem cells.

The discovery of the Ten-Eleven Translocation (TET) protein family was initiated by the identification of the MLL partner TET1, and of mutations in the TET2 gene in hematological malignancies including myeloproliferative neoplasms (MPN). TET1, 2 and 3 proteins hydroxylate 5-methylcytosine (5-mC) into 5-hydroxymethylcytosine (5-hmC) and further oxidize 5-hmC into 5-formylcytosine (5-fC) and 5-carboxylcytosine (5-caC). Previous studies highlight the involvement of TET proteins in somatic cells reprogramming into induced pluripotent stem cells (iPSC), particularly Tet1 and 2 in mouse and TET1 in human. Here, we asked whether endogenous TET2 knockdown also displays this function. Using different shRNA against TET2, we provide evidence that TET2 strongly decreases the reprogramming of human hematopoietic progenitor cells into iPSC. Importantly, using 2 MPN patients, we observed that TET2 mutations affecting catalytic domain allowed iPSC generation. Instead, using another TET2 and TET3-mutated patient, we could only reprogram IPSC with TET3 mutation alone, suggesting that the type of TET2 mutation and/or the cooperation with TET3 mutations may alter the reprogramming activity. Altogether, this work highlights the importance of endogenous TET in the reprogramming process of human hematopoietic progenitors.

Transposon-mediated generation of CAR-T cells shows efficient anti B-cell leukemia response after ex vivo expansion.

CAR-T-cell therapy has shown considerable advance in recent years, being approved by regulatory agencies in US, Europe, and Japan for the treatment of refractory patients with CD19+ B-cell leukemia or diffuse large B-cell lymphoma. Current methods for CAR-T-cell production use viral vectors for T-cell genetic modification and can take up to 15 days to generate the infusion product. The development of simple and less costly manufacturing protocols is needed in order to meet the increasing demand for this therapy. In this present work, we generated 19BBz CAR-T cells in 8 days using a protocol based on the non-viral transposon-based vector Sleeping Beauty. The expanded cells display mostly a central memory phenotype, expressing higher levels of inhibitory receptors when compared with mock cells. In addition, CAR-T cells were cytotoxic against CD19+ leukemia cells in vitro and improved overall survival rates of mice xenografted with human RS4;11 or Nalm-6 B-cell leukemias. Infused CAR-T cells persisted for up to 28 days, showing that they are capable of long-term persistence and antitumor response. Altogether, these results demonstrate the effectiveness of our protocol and pave the way for a broader application of CAR-T-cell therapy.

Myeloid malignancies-related somatic mutations in aging individuals.

We search for the presence of somatic mutations in 12 genes related to MDS, MPN, and AML in a Brazilian cohort composed of 609 elderly individuals from a census-based sample.

Characterization of a human induced Pluripotent Stem (iPS) cell line (INCABRi002-A) derived from a primary myelofibrosis patient harboring the 5-bp insertion in CALR and the p.W146X mutation in TP53.

Primary myelofibrosis (PMF) is a hematological malignancy characterized by activation of the JAK/STAT pathway and risk of leukemic transformation. In this study, we generated an induced Pluripotent Stem (iPS) cell line derived from a 65-year old male PMF patient carrying the 5-pb insertion in the CALR gene (CALRins5) and the c.437 G > A mutation in the TP53 gene (p.W146X). The newly derived PMF3.17 iPS cell line harbors the original mutations and was characterized as bona fide iPS. Resource table.

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.

Generation and characterization of a human induced pluripotent stem (iPS) cell line derived from an acute myeloid leukemia patient evolving from primary myelofibrosis carrying the CALR 52bp deletion and the ASXL1 p.R693X mutation.

Peripheral blood sample was donated by a 61years old female patient diagnosed with acute myeloid leukemia secondary to a primary myelofibrosis harboring the 52-bp deletion in the CALR gene (c.1092_1143del, p.L367fs*46) and the R693X mutation in the ASXL1 gene (c.2077C>T, p.R693X). CD34+ cells were isolated from the sample and subjected to the reprogramming procedure by using the Sendai virus carrying the reprogramming factors Oct3/4, Sox2, Klf4 and c-Myc. iPS colonies generated retained the original mutations and displayed all the features of bona fide iPS cells.

TET2 expression level and 5-hydroxymethylcytosine are decreased in refractory cytopenia of childhood.

Myelodysplastic syndromes (MDS) are myeloid malignancies characterized by ineffective hematopoiesis, dysplasia, peripheral cytopenia and increased risk of progression to acute myeloid leukemia. Refractory cytopenia of childhood (RCC) is the most common subtype of pediatric MDS and has overlapping clinical features with viral infections and autoimmune disorders. Mutations in TET2 gene are found in about 20-25% of adult MDS and are associated with a decrease in 5-hydroxymethylcytosine (5-hmC) content. TET2 deregulation and its malignant potential were reported in adult but not in pediatric MDS. We evaluated the gene expression and the presence of mutations in TET2 gene in 19 patients with RCC. TET2 expression level was correlated with 5-hmC amount in DNA and possible regulatory epigenetic mechanisms. One out of 19 pediatric patients with RCC was a carrier of a TET2 mutation. TET2 expression and 5-hmC levels were decreased in patients when compared to a disease-free group. Lower expression was not associated to the presence of mutation or with the status of promoter methylation, but a significant correlation with microRNA-22 expression was found. These findings suggested that TET2 downregulation and low levels of 5-hmC are inversely related to miR-22 expression. The existence of a regulatory loop between microRNA-22 and TET2 may play a role in MDS pathogenesis.

TET2 deficiency inhibits mesoderm and hematopoietic differentiation in human embryonic stem cells.

Ten-eleven-translocation 2 (TET2) belongs to the TET protein family that catalyzes the conversion of 5-methylcytosine into 5-hydroxymethylcytosine and plays a central role in normal and malignant adult hematopoiesis. Yet the role of TET2 in human hematopoietic development remains largely unknown. Here, we show that TET2 expression is low in human embryonic stem cell (ESC) lines and increases during hematopoietic differentiation. shRNA-mediated TET2 knockdown had no effect on the pluripotency of various ESCs. However, it skewed their differentiation into neuroectoderm at the expense of endoderm and mesoderm both in vitro and in vivo. These effects were rescued by reintroducing the targeted TET2 protein. Moreover, TET2-driven differentiation was dependent on NANOG transcriptional factor. Indeed, TET2 bound to NANOG promoter and in TET2-deficient cells the methylation of the NANOG promoter correlated with a decreased in NANOG expression. The altered differentiation resulting from TET2 knockdown in ESCs led to a decrease in both the number and the cloning capacities of hematopoietic progenitors. These defects were due to an increased apoptosis and an altered gene expression profile, including abnormal expression of neuronal genes. Intriguingly, when TET2 was knockdown in hematopoietic cells, it increased hematopoietic development. In conclusion, our work suggests that TET2 is involved in different stages of human embryonic development, including induction of the mesoderm and hematopoietic differentiation.

Inhibition of TET2-mediated conversion of 5-methylcytosine to 5-hydroxymethylcytosine disturbs erythroid and granulomonocytic differentiation of human hematopoietic progenitors.

TET2 converts 5-methylcytosine to 5-hydroxymethylcytosine (5-hmC) in DNA and is frequently mutated in myeloid malignancies, including myeloproliferative neoplasms. Here we show that the level of 5-hmC is decreased in granulocyte DNA from myeloproliferative neoplasm patients with TET2 mutations compared with granulocyte DNA from healthy patients. Inhibition of TET2 by RNA interference decreases 5-hmC levels in both human leukemia cell lines and cord blood CD34(+) cells. These results confirm the enzymatic function of TET2 in human hematopoietic cells. Knockdown of TET2 in cord blood CD34(+) cells skews progenitor differentiation toward the granulomonocytic lineage at the expense of lymphoid and erythroid lineages. In addition, by monitoring in vitro granulomonocytic development we found a decreased granulocytic differentiation and an increase in monocytic cells. Our results indicate that TET2 disruption affects 5-hmC levels in human myeloid cells and participates in the pathogenesis of myeloid malignancies through the disturbance of myeloid differentiation.

A mutação JAK2 V617F e as síndromes mieloproliferativas / JAK2 V617F mutation and the myeloproliferative disorders

Síndromes mieloproliferativas (SMPs) são doenças hematopoéticas de origem clonal que apresentam amplificação de uma ou mais linhagens mielóides. Policitemia vera (PV), trombocitemia essencial (TE), mielofibrose idiopática (MF) e leucemia mielóide crônica (LMC) são consideradas SMPs clássicas e apresentam características clínicas e biológicas comuns. Ao contrário de LMC, cuja etiologia está relacionada à proteína constitutivamente ativa Bcr-Abl, o mecanismo molecular de PV, TE e MF permaneceu por muito tempo desconhecido. Esta revisão se foca na recente descoberta da mutação JAK2 V617F em pacientes com PV, TE e MF, sua relação com o fenótipo mieloproliferativo e implicações na abordagem clínica de pacientes.

Myeloproliferative disorders are clonal hematopoietic diseases that are characterized by the amplification of one or more myeloid lineages. Polycythemia vera, essential thrombocythemia, idiopathic myelofibrosis and chronic myeloid leukemia are considered classic myeloproliferative disorders and share common clinical and biological features. While the genetic basis of chronic myeloid leukemia is shown to be the constitutive active protein BCR-ABL, the main molecular lesions in polycythemia vera, essential thrombocythemia and idiopathic myelofibrosis remain unknown. This review focuses on the recent discovery of the JAK2 V617F mutation, its relationship to the myeloproliferative phenotype and implications in the clinical approach of patients.

JAK2 V617F prevalence in Brazilian patients with polycythemia vera, idiopathic myelofibrosis and essential thrombocythemia

Polycythemia vera (PV), essential thrombocythemia (ET) and idiopathic myelofibrosis (IMF) are myeloproliferative disorders (MPD) that arise from the clonal proliferation of a pluripotent hematopoietic progenitor, leading to the overproduction of one or more myeloid lineages. Recently, a specific mutation in the JAK2 gene, which encodes a tyrosine kinase, has been shown to be associated with the myeloproliferative phenotype observed in PV, ET and IMF. In this study of Brazilian patients, the JAK2 V617F mutation [c.1887G > T) was detected in four out of 49 patients with PV (96 percent), 14 out of 25 patients with IMF (56 percent), and in eight out of 29 patients with ET, which is in accordance with previous screenings of this mutation in other populations.