Philadelphia-negative myeloproliferative neoplasms as disorders marked by cytokine modulation

Background: Cytokines are key immune mediators in physiological and disease processes, whose increased levels have been associated with the physiopathology of hematopoietic malignancies, such as myeloproliferative neoplasms. Methods: This study examined the plasma cytokine profiles of patients with essential thrombocythemia, primary myelofibrosis, polycythemia vera and of healthy subjects, and analyzed correlations with JAK2 V617F status and clinical-hematological parameters. Results: The proinflammatory cytokine levels were increased in myeloproliferative neoplasm patients, and the presence of the JAK2 V617F mutation was associated with high IP-10 levels in primary myelofibrosis patients. Conclusions: Essential thrombocythemia, primary myelofibrosis, and polycythemia vera patients exhibited different patterns of cytokine production, as revealed by cytokine network correlations. Together, these findings suggest that augmented cytokine levels are associated with the physiopathology of myeloproliferative neoplasms.

TERRA expression is dysregulated in acute myeloid leukemia

Os telômeros compõem as extremidades dos cromossomos lineares e são responsáveis por manter a integralidade genômica. As regiões subtelomérica e teloméricas são transcritas em RNAs longo não codificantes denominados TERRA (TElomeric Repeat containing RNA). Os TERRAs formam híbridos de DNA-RNA denominados R-loops e estão envolvidos na manutenção e estabilização do telômero, alongamento telomérico por vias dependentes e independentes da telomerase e controle transcricional. Os R-loops devem ser mantidos em níveis ideais, tanto alto quanto baixos níveis de R-loops estão relacionados a lesão do DNA e encurtamento telomérico. Este estudo teve como objetivo avaliar a expressão de TERRA em leucemias mieloides agudas (LMAs). Também foram avaliadas as expressões de genes relacionados a dinâmica telomérica (TERT, TRF2), controle dos R-loops (RNaseH1, RNaseH2) e dinâmica da transcrição dos TERRAs (TRF2, ATRX). A análise por clusterização hierárquica baseada na expressão de TERRA demonstrou que existem dois grupos de LMA, um com alta expressão de TERRA e outro com baixa expressão de TERRA. Ambos os grupos apresentam comprimento telomérico curto, alta expressão de TRF2, RNaseH1 e ATRX. O grupo com alta expressão de TERRA apresenta menor expressão de RNaseH2 (p < 0,05), enzima essencial para a diminuição dos R-loops durante a fase S, e de TERT (p < 0,05). Neste grupo, a baixa expressão de RNaseH2 pode favorecer o acúmulo de R-loops, aumento da quebra de DNA e a ativação de vias alternativas de alongamento telomérico independente da telomerase. Em relação a caracterização citogenética molecular dos grupos de LMAs, o grupo com alta expressão de TERRA se caracteriza por uma baixa prevalência de mutações em fatores de splicing. Baseado na prevalência dos diferentes subtipos de LMA da nossa coorte, foram selecionadas duas linhagens celulares, NB4, uma linhagem de leucemia promielocítica aguda, e THP1, uma linhagem de leucemia mielomonocítica a fim de estudar a importância dos R-loops na manutenção dessas linhagens. As linhagens foram transduzidas com vetores lentivirais contendo RNaseH1-GFP ou apenas GFP. As linhagens transduzidas com vetor lentiviral RNaseH1-GFP apresentaram alta expressão de RNaseH1 (p < 0,05) e maior quimiossensibilidade a citarabina (p < 0,05) . Este resultado indica que a inibição dos R-loops é um potencial alvo terapêutica nas LMAs.Telomeres compose the ends of linear chromosomes and maintain genomic integrity. The subtelomeric and telomeric regions are transcribed into long non-coding RNAs called TERRA (TElomeric Repeat containing RNA). TERRAs form DNA-RNA hybrids called R-loops and are involved in telomere maintenance and stabilization, telomeric elongation by telomerasedependent and independent pathways, and transcriptional control. R-loops must be maintained at optimal levels. Both high and low levels of R-loops are related to DNA damage and telomeric shortening. This study aimed to evaluate the expression of TERRA in acute myeloid leukemias (AMLs). The expressions of genes related to telomeric dynamics (TERT, TRF2), R-loops control (RNaseH1, RNaseH2), and TERRA transcriptional dynamics (TRF2, ATRX) were also evaluated. The analysis by hierarchical clustering based on the expression of TERRA revealed two groups of AML, one with high TERRA expression and the other with low TERRA expression. Both groups demonstrated short telomeric length and high expression of TRF2, RNaseH1, and ATRX. The group with high expression of TERRA showed lower expression of RNaseH2 (p < 0.05), an enzyme responsible for the reduction of R-loops during the S phase, and of TERT (p < 0.05). In this group, the low expression of RNaseH2 may favor the accumulation of R-loops, increased DNA breakage, and activation of alternative telomere lengthening. Regarding the molecular cytogenetic characterization of the AML groups, the group with high expression of TERRA is characterized by a low prevalence of mutations in splicing factors. Based on the prevalence of different AML subtypes in our cohort, two cell lines, NB4, an acute promyelocytic leukemia lineage, and THP1, a myelomonocytic leukemia lineage, were selected to study the importance of R-loops in the maintenance of these lines. NB4 and THP1 were transduced with lentiviral vectors containing RNaseH1-GFP or GFP alone. Cell lines transduced with the lentiviral vector RNaseH1-GFP showed high expression of RNaseH1 (p < 0.05) and greater chemosensitivity to cytarabine (p < 0.05). This result indicates that inhibition of R-loops is a potential therapeutic target in AMLs

Philadelphia-negative myeloproliferative neoplasms as disorders marked by cytokine modulation

Background: Cytokines are key immune mediators in physiological and disease processes, whose increased levels have been associated with the physiopathology of hematopoietic malignancies, such as myeloproliferative neoplasms. Methods: This study examined the plasma cytokine profiles of patients with essential thrombocythemia, primary myelofibrosis, polycythemia vera and of healthy subjects, and analyzed correlations with JAK2 V617F status and clinical-hematological parameters. Results: The proinflammatory cytokine levels were increased in myeloproliferative neoplasm patients, and the presence of the JAK2 V617F mutation was associated with high IP-10 levels in primary myelofibrosis patients. Conclusions: Essential thrombocythemia, primary myelofibrosis, and polycythemia vera patients exhibited different patterns of cytokine production, as revealed by cytokine network correlations. Together, these findings suggest that augmented cytokine levels are associated with the physiopathology of myeloproliferative neoplasms. Keywords: Ph-negative myeloproliferative neoplasms, Inflammation, Plasma cytokines, JAK2 V617