In cancer, tumor cells and their neoplastic microenvironment can sculpt the immunogenic phenotype of a developing tumor. In this context, natural killer (NK) cells are subtypes of lymphocytes of the innate immune system recognized for their potential to eliminate neoplastic cells, not only through direct cytolytic activity but also by favoring the development of an adaptive antitumor immune response. Even though the protective effect against leukemia due to NK-cell alloreactivity mediated by the absence of the KIR-ligand has already been shown, and some data on the role of NK cells in myeloproliferative neoplasms (MPN) has been explored, their mechanisms of immune escape have not been fully investigated. It is still unclear whether NK cells can affect the biology of BCR-ABL1-negative MPN and which mechanisms are involved in the control of leukemic stem cell expansion. Aiming to investigate the potential contribution of NK cells to the pathogenesis of MPN, we characterized the frequency, receptor expression, maturation profile, and function of NK cells from a conditional Jak2V617F murine transgenic model, which faithfully resembles the main clinical and laboratory characteristics of human polycythemia vera, and MPN patients. Immunophenotypic analysis was performed to characterize NK frequency, their subtypes, and receptor expression in both mutated and wild-type samples. We observed a higher frequency of total NK cells in JAK2V617F mutated MPN and a maturation arrest that resulted in low-numbered mature CD11b+ NK cells and increased immature secretory CD27+ cells in both human and murine mutated samples. In agreement, inhibitory receptors were more expressed in MPN. NK cells from Jak2V617F mice presented a lower potential for proliferation and activation than wild-type NK cells. Colonies generated by murine hematopoietic stem cells (HSC) after mutated or wild-type NK co-culture exposure demonstrated that NK cells from Jak2V617F mice were deficient in regulating differentiation and clonogenic capacity. In conclusion, our findings suggest that NK cells have an immature profile with deficient cytotoxicity that may lead to impaired tumor surveillance in MPN. These data provide a new perspective on the behavior of NK cells in the context of myeloid malignancies and can contribute to the development of new therapeutic strategies, targeting onco-inflammatory pathways that can potentially control transformed HSCs.

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Induction of fetal hemoglobin (HbF) production is an effective therapeutic strategy in the management of patients with beta hemoglobinopathies. Hydroxyurea is the only drug with this mechanism approved for clinical use, and 20% or more of patients do not respond or tolerate it, which has led to the search for new HbF inducers. Benserazide (BEN) is a DOPA decarboxylase inhibitor used in combination with levodopa in the treatment of parkinsonism, but it was also noticed to induce increased gamma globin production in preclinical models. The mechanisms by which BEN acts include downregulation of BCL11A, LSD1 and HDAC3 on the promoter region of the gamma globin gene, making it an interesting candidate for clinical studies in hemoglobinopathies. We hypothesized that patients undergoing treatment for parkinsonism with chronic use of BEN-containing medication may develop increase in HbF production and in circulating F-cells. Material and Methods: Peripheral blood samples were collected from patients with parkinsonism during their follow-up at the Neurology Clinic, who had been using BEN for at least 30 days (BEN group), from healthy controls (group AA), and from patients known to have increased of HbF due to sickle cell anemia (group SS), for comparison purposes. Exclusion criteria for BEN and AA groups were: any hemoglobinopathy, transfusion in the last 90 days, and use of HU or any chemotherapeutic agent. Automated complete blood counts with reticulocyte count were performed on a XN-3000 equipment (Sysmex, Japan), HbF levels were determined by HPLC (BioRad, USA), and F-cell percentage was determined by flow cytometry (BD FACSCalibur, USA). Results: Thirty-five patients on BEN, 10 negative controls (AA group) and five positive controls (SS group) were included. One patient taking BEN was excluded due to HPLC compatible with beta thalassemia trait. Patients taking BEN had blood counts within the normal range. There was no statistically significant difference between BEN and AA groups, and the SS group was significantly anemic as expected. We found a strongly positive correlation between HbF and circulating F-cells (p <0.0001, r = 0.946) when analyzing the entire population, but within the subgroup of patients using BEN, this correlation was much weaker (p = 0.0032, r = 0.492). Dose range of BEN used by the patients was 100-700mg daily, at 1.21 to 11.1mg/kg/day, but we found no correlation between dose and HbF levels. Discussion: We found no differences in blood counts, and extensive use of this regimen support that chronic use of BEN is safe in doses up to 11.1mg/kg/day. In vitro studies suggest that BEN is 30 times more potent than HU. Therefore, considering the minimum dose of HU used in clinical practice of 15mg/kg/day, we had expected that some increase in HbF could be observed at 0.5mg/kg/day of BEN. However, our data show that, even with chronic use of doses 20 times higher, there was no increase in HbF or F-cell levels. The lack of effectiveness of BEN in this population may be explained by its hydrolysis in the intestinal mucosa, and by its reported short half-life (48min), which could account for reduced bioavailability. In addition, patients not bearing beta globin mutations may be less likely to respond to gamma globin induction. Conclusion: Although BEN is already in clinical use and is a strong candidate as a new HbF inducer, we did not detect this effect in humans without hemoglobinopathies. Our data impact the experimental design of future clinical trials with BEN, and suggests the need for more studies on its pharmacokinetics and pharmacodynamics to improve the chances of achieving the desired clinical effect. Disclosures Fertrin: Alexion Pharmaceutical Brasil: Speakers Bureau; Apopharma Inc.: Honoraria.

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Gostaria de dedicar esta dissertação às pessoas que me acompanharam desde os primeiros passos, tanto da vida propriamente dita quanto da vida acadêmica. Seus questionamentos e incentivos guiaram meus passos até aqui e me deram equilíbrio para escolher os caminhos: meu pai (Luiz Lauro), minha mãe (Lenirin memoriam), meu marido (Ronaldo) e meu orientador (Kleber). Aos meus filhos, que de formas diferentes e inerentes às suas personalidades, me incentivaram com seus olhinhos ávidos por respostas. Olhinhos nos quais me inspirei tantos dias, pois o encantamento de uma criança perante às respostas da vida é o que o adulto precisa não perder. Por terem me ensinado que o foco e a perseverança superam a dificuldade e a falta de tempo, e que tudo vale a pena quando estou com eles. Aos familiares, que mesmo sem compreender ao que eu me dedicava, conseguiram me apoiar, fosse com palavras ou cuidando dos meus filhos. Aos amigos conquistados, reconquistados e aos afastados pela falta de tempo. O importante não é estar junto, mas do lado de dentro (do coração). À minha amiga irmã, Patricia, que me prova que não importa o tempo, a distância ou a situação, esteve e sempre estará ao meu lado. Aos pacientes, que ansiosos pela cura, também se dedicaram ao nosso trabalho, doando-se. "Viver é enfrentar um problema atrás do outro. O modo como você o encara é que faz a diferença" Benjamin Franklin AGRADECIMENTOS Agradeço ao meu orientador, Dr. Kleber Fertrin, exemplo de orientador, profissional louvável, dotado de ética e capaz de motivar, ensinar e encantar. Agradeço por ter reaberto uma porta que eu pensei que estava fechada. Por ter acreditado e confiado em mim, não apenas na execução desse projeto, mas em tantos momentos da vida. Foram tantos os sonhos e planos que fizemos juntos, que, de certa forma, acredito que estejam se concretizando finalmente com conclusão desse trabalho. Espero que não seja o fim!