A leucemia linfóide aguda (LLA) é considerada uma doença grave dos glóbulos brancos, sendo mais comum e mais agressiva em crianças e adolescentes. O tratamento para a LLA tem avançado devido aos estudos para a otimização de drogas já utilizadas em quimioterapias. Entre essas drogas estão as enzimas L- asparaginases (ASPases) que atuam reduzindo a concentração de L-asparagina (Asn) na corrente sanguínea, impedindo a proliferação das células cancerosas, visto que essas não conseguem sintetizar quantidades apropriadas desse aminoácido. No entanto, o medicamento por ser oriundo de um procarioto causa severas reações alérgicas aos usuário, afim de diminuir a imunogenicidade deste quimioterápico, é importante gerar um biofármaco oriundo de um eucarioto. Neste âmbito, obtivemos a Pichia pastoris recombinante responsável pela produção da enzima ASPase intermembranar, oriunda do gene ASP3 de Saccharomyces cerevisiae. Através do planejamento experimental, foi possível ter um aumento de 5 vezes na atividade obtida na condição inicial. O clone Mut+ alcançou sua melhor atividade de 8,6 U/g de célula nas seguintes condições: 20°C, pH inicial 6 e 1,5% de concentração de indutor. / Acute lymphoblastic leukemia (ALL) is considered a serious disease of white blood cells, is more common and more aggressive in children and adolescents. Treatment for ALL has advanced due to studies for drug optimization already used in chemotherapy. Among these drugs are the enzymes L-asparaginases (ASPases) which act by reducing the concentration of L-asparagine (Asn) in the bloodstream, preventing the proliferation of cancer cells, since these can not synthesize appropriate amounts of this amino acid. However, the drug to be derived from a prokaryote causes severe allergic reactions to the user, in order to decrease the immunogenicity of the chemotherapy, it is important to generate a biopharmaceutical derived from a eukaryote. In this context, we obtained the recombinant Pichia pastoris responsible for producing the enzyme ASPase intermembrane, coming from the ASP3 gene of Saccharomyces cerevisiae. Through the experimental design, it was possible to have a 5-fold increase in activity obtained at the initial condition. The Mut + clone achieved their best activity of 8.6 U/g cell under the following conditions: 20 °C, initial pH 6 and 1.5% of inducer concentration.

A L- asparaginase é uma enzima aplicada no tratamento de Leucemia Linfoide Aguda, que atua na hidrólise da L- asparagina, privando a célula tumoral de um aminoácido essencial para o seu crescimento. A L- asparaginase, como outros biofármacos, deve ser estável, manter sua atividade específica e formar poucos agregados. A fim de manter a integridade do biofármaco, são utilizados adjuvantes nas formulações farmacêuticas, e dentre os mais importantes estão os osmólitos. Essas moléculas protegem a estrutura nativa da proteína, sendo capazes de interferir na formação de agregados e garantir a estabilidade proteica. O presente trabalho teve o objetivo de estudar o efeito dos osmólitos sacarose, sorbitol, arginina e glicina na atividade específica, estabilidade, cinética e caracterização de agregados na solução de L- asparaginase II de Erwinia chrysanthemi. Os resultados mostraram que a maioria dos osmólitos testados aumentou a atividade específica e a estabilidade da enzima, o que pode estar relacionado com o aumento da velocidade máxima e do kcat observados no ensaio cinético realizado com sacarose e sorbitol. Um perfil diferente de agregados foi encontrado para cada tipo de osmólito. A presença de sacarose ou sorbitol resultou na menor quantidade de agregados na faixa de, respectivamente, 100 a 200 e 200 a 300 nm em relação a enzima sem osmólito. Por outro lado, aumento no número total de agregados e presença de moléculas de alto peso molecular (300 a 500 nm) foram observados nas soluções enzimáticas contendo, respectivamente, glicina e arginina. Dessa forma, os resultados obtidos neste trabalho poderão auxiliar na produção e escolha da formulação de biofármacos, e, consequentemente, melhorar o tratamento medicamentoso de pacientes. / L L-Asparaginase is an enzyme applied in the treatment of Acute Lymphoblastic Leukemia, which acts on the hydrolysis of L- asparagine, depriving the tumor cell of an essential amino acid for its growth. L-asparaginase, as other biopharmaceuticals, must be stable, maintain its specific activity and form few aggregates. In order to maintain the integrity of the biopharmaceutical, adjuvants are used in the pharmaceutical formulations, and among the most importants adjuvants are the osmolytes. These molecules protect the native structure of the protein, being able of interfering in the formation of aggregates and guarantee protein stability. The present work had the objective of studying the effect of the osmolytes sucrose, sorbitol, arginine and glycine in the specific activity, stability, kinetic and aggregates characterization, in L- asparaginase II solution of Erwinia chrysanthemi. The results showed that the majority of the tested osmolytes increased the specific activity of the enzyme and its stability, which may be related to the augment of maximum velocity and kcat observed in the kinetic assay performed with sucrose and sorbitol. A different profile of aggregates was found for each type of osmolyte. The presence of sucrose or sorbitol resulted in the least amount of aggregates in the range of, respectively, 100-200 and 200-300nm in relation to the enzyme without osmolyte. On the other hand, increase in the total number of aggregates and the presence of high molecular weight molecules (300 to 500 nm) were observed in the enzymatic solutions containing, respectively, glycine and arginine. Thus, the results obtained in this work may help in the production and choice of the formulation of biopharmaceuticals and, consequently, improve the drug treatment of patients.

This study consists of two pieces of work investigating haematological malignancies; Acute Lymphoblastic Leukaemia (ALL) and Diffuse Large B Cell Lymphoma (DLBCL). Firstly, Pre-B ALL represents the most common paediatric malignancy and despite increasingly improved outcomes for patients, ~ 20% of all patients diagnosed with ALL relapse. Activating mutations in the RAS pathway are common (~50%) and result in hyperactivation of the MAPK pathway. I identified Erk negative feedback control via DUSP6 to be crucial for NRASG12D-mediated pre-B cell transformation and investigated its potential as a therapeutic target. I showed that a small molecule inhibitor of DUSP6 (BCI) selectively induced cell death in patient-derived pre-B ALL cells; with a higher sensitivity observed in relapse pre-B ALL. I also discovered that a high level of Erk activity is required for proliferation of normal pre-B cells, but dispensable in leukemic pre-B ALL cells. In addition, I found that human B cell malignancies can be grouped into three categories that fundamentally differ in their ability to control Erk signalling strength. Secondly, DLBCL is the most common haematological malignancy and although potentially curable with chemotherapy, 40% of patients still succumb from their disease. Recent exome sequencing studies have identified hundreds of genetic alterations but, for most, their contribution to disease, or their importance as therapeutic targets, remains uncertain. I optimised a novel approach to screen the functional importance of these mutations. This was achieved by reconstituting non-malignant, primary, human germinal centre B cells (GC B cells) with combinations of wildtype and mutant genes to recapitulate the genetic events of DLBCL. When injected into immunodeficient mice, these oncogene-transduced GC B cells gave rise to tumours that closely resemble human DLBCL, reinforcing the biological relevance of this system. To screen potential tumour suppressor mutations in this system in a high throughput fashion, I developed a lymphoma-focused CRISPR library of 692 genes recurrently altered in B cell lymphomas. These experiments identified GNA13 as an unexpectedly potent tumour suppressor in human GC B cells and provided new understanding to its mechanism of action. These findings provide novel understanding of the complexity of oncogenic mechanisms in human B cell malignancies.

A leucemia linfoide aguda (LLA) compreende um grupo heterogêneo de neoplasias caracterizadas por proliferação anormal e acúmulo de células imaturas na medula óssea, o que prejudica a produção de eritrócitos, leucócitos e plaquetas. O fator de crescimento semelhante à insulina 1 (insulin-like growth factor 1; IGF1) e seu receptor (IGF1R) regulam o crescimento celular normal e contribuem para a transformação e crescimento de células malignas através da ativação de vias de sinalização intracelular. A via de sinalização do IGF1 é iniciada através da ativação de seu receptor seguido da ativação de seus substratos, incluindo o substrato 1 do receptor de insulina (insulin receptor substrate 1; IRS1). IRS1 é uma proteína predominantemente citosólica envolvida na transdução de sinal, e também desempenha um papel na transformação maligna, sendo altamente expresso em muitos tipos de câncer. Em fibroblastos de camundongos, Irs1, através da sinalização do Igf1, foi descoberto como uma proteína chave para a translocação nuclear da ?-catenina e ativação da transcrição de seus genes alvos, como o Myc e a ciclina D1. MYC e ciclina D1 podem atuar como oncogenes, contribuindo para o desenvolvimento de diversas neoplasias, inclusive as hematopoéticas. Deste modo, o objetivo deste projeto de pesquisa foi investigar a participação do IRS1 nuclear na via da ?-catenina em LLA. Foram utilizadas no estudo linhagens celulares de LLA (Jurkat, MOLT4, Raji e Namalwa) e células hematopoéticas primárias de doadores normais (n=13) e de pacientes adultos com LLA (n=45) atendidos em nossa Instituição. Estudos de expressão gênica (PCRq), expressão, associação proteica (western blotting, imunoprecipitação) e localização celular (fracionamento subcelular e microscopia confocal) foram utilizados. Células da linhagem Jurkat foram submetidas à estimulação com IGF1 e/ou inibição farmacológica de IGF1R (OSI-906). Observamos elevada expressão gênica relativa de IRS1, ?-catenina e MYC nos pacientes com LLA quando comparada aos controles normais (p<0,05), mas não houve diferença na expressão gênica de ciclina D1 e IGF1R entre os dois grupos. Observamos uma correlação positiva entre a expressão gênica de ?-catenina e MYC (p=0.0004; r=0.50), e entre a expressão de IRS1 e MYC (p=0.001; r=0.45) na coorte de pacientes com LLA. Na análise univariada, idade e expressão de MYC correlacionaram-se negativamente com a sobrevida global de pacientes com LLA; idade foi fator independente de prognóstico para a sobrevida. Em linhagens celulares de LLA (Jurkat, MOLT4, Raji e Namalwa), observamos co-localização de IRS1 e ?-catenina no núcleo e no citoplasma. Em células primárias de doador normal, IRS1 e ?-catenina localizaram-se predominantemente no citoplasma. Em células da linhagem celular Jurkat, observamos interação entre IRS1 e ?- catenina e o estímulo com IGF1 provocou o aumento da fosforilação em tirosina de IRS1. O tratamento com OSI-906 diminuiu a fosforilação em tirosina de IGF1R, a translocação nuclear de ?-catenina e a expressão proteica de MYC em células Jurkat. Em conclusão, nossos dados suportam uma relação entre a via de sinalização IGF1R/IRS1 e a ativação da ?- catenina em leucemia linfoide aguda, o que pode representar um importante eixo de sinalização envolvido na fisiopatologia da doença. / The acute lymphoblastic leukemia (ALL) is a heterogeneous group of malignancies characterized by abnormal proliferation and accumulation of immature cells in the bone marrow, which impairs the production of erythrocytes, leukocytes and platelets. Insulin-like growth factor 1 (IGF1) and its receptor (IGF1R) regulate normal cell growth and contribute to transformation and growth of malignant cells through activation of downstream signaling pathways. The IGF1 signaling pathway is initiated through activation of its receptor followed by activation of its substrates, including insulin receptor substrate 1 (IRS1). IRS1 is well known as a cytosolic protein involved in signal transduction, but also plays a role in malignant transformation, being highly expressed in many cancers. In mouse fibroblasts, Irs1, through Igf1 signaling, was found to be the key protein for nuclear translocation of ?-catenin and transcription activation of its target genes, such as Myc and cyclin D1. MYC and cyclin D1 may act as oncogenes, contributing to the development of cancers, including hematopoietic neoplasm. Thus, the aims of this study were to investigate the role of nuclear IRS1 in the ?-catenin pathway in LLA. We used in the study ALL cell lines (Jurkat, MOLT-4, Namalwa and Raji) and primary hematopoietic cells from healthy donors (n=13) and from adult patients with ALL (n=45) treated at our Institution. Studies of gene expression (qPCR), protein expression, association (Western blotting and immunoprecipitation) and cell location (subcellular fractionation and confocal microscopy) were used. Jurkat cells were submitted to IGF1 stimulation and/or IGF1R pharmacological inhibition (OSI-906). IRS1, ?-catenin and MYC relative gene expression were significantly elevated in ALL patients compared to normal controls (p<0.05), but there was no difference in gene expression of cyclin D1 and IGF1R between the two groups. A positive correlation between ?-catenin and MYC relative expression (p=0.0004; r=0.50) and between IRS1 and MYC expression (p=0.001; r=0.45) was found. Univariate analysis revealed that increasing age and elevated expression of MYC are factors that adversely affect the overall survival; age was an independent prognostic factor for survival. IRS1 and ?-catenin co-localized in the nucleus and cytoplasm of ALL cell lines (Jurkat, MOLT4, Raji e Namalwa). In primary cell of normal donor, IRS1 and ?-catenin were found predominantly in the cytoplasm. In Jurkat cells, a constitutive IRS1 and ?-catenin protein interaction was observed and IGF1 stimulation increased IRS1 tyrosine phosphorylation. OSI-906 treatment decreased IGF1R tyrosine phosphorylation, nuclear translocation of ?-catenin and MYC protein expression in Jurkat cells. In conclusion, our data support a link between the signaling pathway IGF1R/IRS1 and activation of ?-catenin in acute lymphoblastic leukemia, which may represent an important axis involved in the pathophysiology of the disease.

Background: In childhood acute lymphoblastic leukemia (ALL), the cure rate has now reached 80% in the western world. Even so, 15¬–20% will die from the disease or treatment-related causes, among them children who did not present any known unfavorable features at diagnosis. Treatment of childhood ALL is risk-adapted, meaning that certain factors that are related to the child or the leukemic blasts stratifies to more or less intensive treatment. In this thesis, characteristics of the bone marrow (BM) stroma, reflecting the interaction between the leukemic cells and their microenvironment, were evaluated. The aims were to investigate these factors in relation to other known data in order to further understand the biology of leukemia, and to suggest additional risk factors that would further improve decision making for the treatment of individual children diagnosed with ALL. Methods: We retrospectively investigated microvessel density (MVD), blast-congested vessel fraction (BCVF), and degree of fibrosis – reticulin fiber density (RFD) – in sections from diagnostic BM biopsies from children diagnosed in Umeå, Uppsala, and Stockholm. RFD was also studied in BM sections from treatment day 29. Results: RFD had prognostic impact in patients with high-hyperdiploid (HeH) leukemia. Moreover, rapid reduction of RFD during induction treatment was associated with a favorable prognosis compared to slow reduction, in B-cell precursor (BCP) ALL patients. There was also a correlation between RFD at diagnosis and minimal residual disease (MRD) measured by flow cytometry on treatment day 29 in BCP patients. BCP patients with high RFD and high MVD had an unfavorable outcome compared to all other BCP patients. In addition, MVD and RFD were both associated with immunophenotype, and MVD with cytogenetic aberrations. There was a correlation between MVD and WBC count in BCP high-risk patients. There was also a strong correlation between BCVF and WBC count in all BCP patients, but not between BCVF and MVD or RFD. There was a negative correlation between MVD and in vitro cellular resistance to several drugs in BCP patients. A drug-resistance score combining the drugs most strongly correlated to MVD – cytarabine, doxorubicin, and dexametasone (ADD score) – identified the prognostic potential of ADD score in HeH patients with no unfavorable features. Conclusions: Taken together, these studies indicate that stroma factors in leukemia are related to both phenotypic and genotypic features of acute leukemia. Stroma factors also seem to influence the response to induction treatment, in vitro drug resistance, and outcome in certain subgroups of childhood ALL patients. The results emphasize the importance of BM stroma in leukemia and the need for greater use of BM biopsy at diagnosis.

Source: Dissertation Abstracts International, Volume: 70-03, Section: B, page: 1574. Adviser: Elaine Symanski. Includes bibliographical references.

The thesis is based on three studies in which data on children with acute lymhpblastic leukemia (ALL) treated in Lithuania or the Nordic countries were analyzed. Study I. Epidemiological and survival data of 459 children treated in Lithuania in 1992-2012 were analyzed. Children with ALL were included for the first time into international clinical trial that was conducted by pediatric oncologists in the Nordic countries. This resulted in survival improval of childhood ALL by 20% reaching results reported by large international childhood ALL study groups. Study II. Study of 2636 childhood ALL patients treated in the Nordic countries in 1992-2008 revealed significant differences in white blood cell (WBC) distribution both among different biological ALL subsets defined by immunophenotype or cytogenetical aberrations of leukemic blasts, and among patients of different age or gender. WBC remained as a risk factor to have a significantly poorer prognosis for patients with a WBC ≥100 x 109/L, but only among slow-responding patients. Study III. A population-based multicenter study of 221 children aged <15 y. with ALL and WBC ≥200x109/L at diagnosis treated in Lithuania and the Nordic countries were analyzed for early mortality and the impact of initial treatment strategy to survival. The Nordic/Baltic guidelines for initial treatment of ALL patients with hyperleukocytosis and a high risk for the development of tumor lysis syndrome (WBC ≥100 x 109/L) were conducted. / Disertacijoje nagrinėjami Lietuvoje ir Šiaurės šalyse 1992-2012 m. ūmine limfoblastine leukemija (ŪLL) sirgusių vaikų duomenys. I tyrimas. Surinkti ir išanalizuoti 1992-2012 m. Lietuvoje gydytų ŪLL sirgusių vaikų (N=459) epidemiologija ir gydymo rezultatai, įsitraukta į tarptautinio (kartu su Šiaurės šalių vaikų onkohematologais) vaikų ŪLL gydymo protokolą. ŪLL sergančių vaikų išgyvenamumas Lietuvoje pagerėjo apie 20% ir pasiekė tarptautinį lygį. II tyrimas. Išanalizavus Šiaurės šalyse 1992-2008 m. dėl ŪLL gydytų vaikų duomenis (N=2363) nustatytos leukeminių blastų citogenetinės aberacijos ir ligonio biologiniai veiksniai, lemiantys skirtingą LS diagnozuojant ŪLL. Nustatyta, kad LS buvo reikšmingas išgyvenamumo rizikos veiksnys tiek pre-B ŪLL, tiek T-ŪLL ligoniams, kuriems pradinis LS buvo ≥100 x 109/L, tačiau tik tais atvejais, kai atsakas į gydymą buvo lėtas. III tyrimas. Populiaciniame tyrime išanalizuoti 1992-2011 m. Lietuvoje ar Šiaurės šalyse ŪLL sirgusių vaikų, kurių pradinis LS≥200 x 109/L, duomenys (N=221). Nustatyta, kad didelis leukocitų skaičius, o ne naviko lizės sindromas buvo pagrindinis ankstyvo mirtingumo rizikos veiksnys. Uždelstas specifinis ŪLL gydymas ar sumažintos pradinės chemopreparatų dozės galėjo turėti neigiamos reikšmės ankstyvų mirčių išsivystymui. Sudarytos bendros Baltijos ir Šiaurės šalių centrams skirtos rekomendacijos dėl pradinės ligonių su ŪLL ir hiperleukocitoze bei didele naviko lizės išsivystymo rizika (LS ≥100 x 109/L), gydymo taktikos... [toliau žr. visą tekstą]

Disertacijoje nagrinėjami Lietuvoje ir Šiaurės šalyse 1992-2012 m. ūmine limfoblastine leukemija (ŪLL) sirgusių vaikų duomenys. I tyrimas. Surinkti ir išanalizuoti 1992-2012 m. Lietuvoje gydytų ŪLL sirgusių vaikų (N=459) epidemiologija ir gydymo rezultatai, įsitraukta į tarptautinio (kartu su Šiaurės šalių vaikų onkohematologais) vaikų ŪLL gydymo protokolą. ŪLL sergančių vaikų išgyvenamumas Lietuvoje pagerėjo apie 20% ir pasiekė tarptautinį lygį. II tyrimas. Išanalizavus Šiaurės šalyse 1992-2008 m. dėl ŪLL gydytų vaikų duomenis (N=2363) nustatytos leukeminių blastų citogenetinės aberacijos ir ligonio biologiniai veiksniai, lemiantys skirtingą LS diagnozuojant ŪLL. Nustatyta, kad LS buvo reikšmingas išgyvenamumo rizikos veiksnys tiek pre-B ŪLL, tiek T-ŪLL ligoniams, kuriems pradinis LS buvo ≥100 x 109/L, tačiau tik tais atvejais, kai atsakas į gydymą buvo lėtas. III tyrimas. Populiaciniame tyrime išanalizuoti 1992-2011 m. Lietuvoje ar Šiaurės šalyse ŪLL sirgusių vaikų, kurių pradinis LS≥200 x 109/L, duomenys (N=221). Nustatyta, kad didelis leukocitų skaičius, o ne naviko lizės sindromas buvo pagrindinis ankstyvo mirtingumo rizikos veiksnys. Uždelstas specifinis ŪLL gydymas ar sumažintos pradinės chemopreparatų dozės galėjo turėti neigiamos reikšmės ankstyvų mirčių išsivystymui. Sudarytos bendros Baltijos ir Šiaurės šalių centrams skirtos rekomendacijos dėl pradinės ligonių su ŪLL ir hiperleukocitoze bei didele naviko lizės išsivystymo rizika (LS ≥100 x 109/L), gydymo taktikos... [toliau žr. visą tekstą] / The thesis is based on three studies in which data on children with acute lymhpblastic leukemia (ALL) treated in Lithuania or the Nordic countries were analyzed. Study I. Epidemiological and survival data of 459 children treated in Lithuania in 1992-2012 were analyzed. Children with ALL were included for the first time into international clinical trial that was conducted by pediatric oncologists in the Nordic countries. This resulted in survival improval of childhood ALL by 20% reaching results reported by large international childhood ALL study groups. Study II. Study of 2636 childhood ALL patients treated in the Nordic countries in 1992-2008 revealed significant differences in white blood cell (WBC) distribution both among different biological ALL subsets defined by immunophenotype or cytogenetical aberrations of leukemic blasts, and among patients of different age or gender. WBC remained as a risk factor to have a significantly poorer prognosis for patients with a WBC ≥100 x 109/L, but only among slow-responding patients. Study III. A population-based multicenter study of 221 children aged <15 y. with ALL and WBC ≥200x109/L at diagnosis treated in Lithuania and the Nordic countries were analyzed for early mortality and the impact of initial treatment strategy to survival. The Nordic/Baltic guidelines for initial treatment of ALL patients with hyperleukocytosis and a high risk for the development of tumor lysis syndrome (WBC ≥100 x 109/L) were conducted.

TAL-1, ectopically expressed in 60% of T-cell acute lymphoblastic leukemia (T-ALL) patients, may contribute to poor chemotherapy response. This research sought to determine if TAL-1 influences expression of proteins involved in the NF-kB signaling pathway and thus, resistance to cell death. NF-kB, IKKy, and TRAF-2 expression levels were found to be TAL-1 dependent. Cell death levels were higher in staurosporine-treated cells compared to tumor necrosis factor a-treated or dual-treated cells. TAL-1, NF-kB, IKKy, and TRAF-2 expression levels were elevated in tumor necrosis factor a-treated cells and reduced in staurosporine-treated or dual treated cells compared to untreated cells. These results suggest TAL-1 influences expression of proteins involved in the NF-kB signaling pathway, thus inducing an anti-apoptotic response in the cell. / Department of Biology

<p>Hematopoiesis is the continual process of blood cell generation that primarily occurs in the bone marrow of adult animals. Hematologic neoplasms can also occur in the bone marrow and often result from dysregulation of signal transduction pathways. One example is the activation of the Ras oncogene, which has been linked to a variety of different cancers, including hematologic neoplasms. Ras is located proximal to the cell membrane and can activate many downstream effector pathways, thus it is difficult to determine which downstream pathway is mediating oncogenic Ras function. My thesis work focused on the effect of inappropriate activation of MEK/ERK, a downstream Ras effector pathway, in the hematopoietic system.</p><p>Using a retroviral transduction system, we expressed a constitutively active form of MEK1 in hematopoietic stem cells (HSCs). Mice transplanted with HSCs expressing active MEK developed a lethal myelodysplastic syndrome/myeloproliferative disease (MDS/MPN) characterized by the expansion of granulocytes/macrophages (GM) at the expense of lymphoid cell development. Transplantation of active MEK-induced MDS/MPNs into naïve mice did not result in further disease, suggesting that the MDS/MPN is not a frank leukemia.</p><p>Bcl-2 is an anti-apoptotic molecule that has been shown to play a role in leukemia development and maintenance. Coupling expression of active MEK and Bcl-2 resulted in MDS/MPNs that were phenotypically identical and had very similar disease onset compared to active MEK-induced MDS/MPNs. However, transplantation of Bcl-2/active MEK-induced MDS/MPNs did not result in a myeloid disease; rather, it resulted in the development of T-acute lymphoblastic leukemia (T-ALL) that was marked by activated Notch signaling. </p><p>These results led us to conclude that activation of MEK/ERK was sufficient to cause a pre-leukemic myeloid disease; however, additional oncogenic factors, such as Bcl-2 and Notch, were necessary for frank leukemia development. Moreover, additional oncogenic factors can alter the disease phenotype and disease course. Future analysis of the interplay between oncogenic factors will help shed light on disease development and aid in the development of more effective cancer treatments.</p> / Dissertation