published_or_final_version / Pathology / Master / Master of Philosophy

Thesis (M. Phil.)--Universiry of Hong Kong, 1994. / Includes bibliographical references (leaves 111-121).

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 76-82).

Extensive efforts have shed light on the identity and biology of cancer stem cells, required and sufficient for the propagation of hematological malignancies and solid tumours. Much less is understood about the closely related issue as to the identity and properties of the normal stem and progenitor cells targeted by oncogenic lesions, and how the nature of the targeted cell might impact on the biology and clinical picture of the resulting cancer. To address this, we developed a mouse model allowing targeted inactivation of Ezh2 and Runx1 to different haematopoietic compartments. Inactivating mutations of EZH2 and RUNX1 frequently co-occur in haematological malignancies with markedly different phenotypes including myelodysplastic syndrome (MDS) and early thymic progenitor (ETP) leukaemia. Inactivation of Ezh2 and Runx1 in adult haematopoietic stem cells (HSCs) resulted in perturbed haematopoiesis leading to development of an MDS-like disease. Unexpectedly, this MDS phenotype could be fully reproduced when Ezh2 and Runx1 inactivation was targeted to multipotent progenitors (MPPs) using Flt3-Cre. Furthermore, the disease was transplantable by MPPs, but not more committed progenitor populations, demonstrating that MDS tumour propagating potential is not exclusive to intrinsically self-renewing HSCs. Targeting Ezh2 and Runx1 inactivation to early lympho-myeloid progenitors did not result in an MDS phenotype. These mice showed a marked expansion of ETPs within the thymus, combined with a block in thymocyte differentiation. These expanded ETPs displayed transcriptional features characteristic of ETP leukaemia, a treatment-resistant acute leukaemia subtype hypothesised to originate from ETPs. Combination of inactivation of Ezh2 and Runx1 in ETPs with the constitutively activating Flt3-ITD signalling mutation resulted in an aggressive lympho-myeloid acute leukaemia, which could be propagated by the expanded ETP population. These findings demonstrate the potential of lympho-myeloid progenitors such as ETPs to become leukaemia stem cells which propagate a disease retaining lympho-myeloid features. We used this novel ETP leukaemia model to explore therapeutic targeting of Ezh2-inactivated ETP leukaemias using inhibitors of the bromodomain and extra terminal (BET) proteins. Aberrant transcription resulting from epigenetic changes induced by Ezh2 loss could be reversed by BET inhibitors, and these compounds showed therapeutic efficacy against both mouse and human ETP leukaemias in vitro and in vivo.

Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 4 uppsatser.

Understanding which cells within a cancer are responsible for its initiation and propagation is vital if we are to achieve cure. If cancer stem cells are the only population able to sustain a tumour long term, designing therapeutic strategies to target this population will give medical science the best chance of long-term cure. Significant controversy remains over the existence of cancer stem cells, predominantly due to the lack of a sensitive human cancer stem cell assay. This thesis investigates whether two haematological malignancies, myelodysplastic syndromes (MDS) and chronic myelomonocytic leukaemia (CMML) can only be driven by rare and distinct cancer stem cells. We have demonstrated that low and intermediate-1 risk MDS is driven solely by the stem cell (Lin- CD34+ CD38- CD90+ CD45RA-) by developing a novel genetic approach, tracing all somatic mutations and karyotypic abnormalities back to this population. Prior to this study, very little was known about the clonal architecture of CMML. By performing detailed phenotypic, functional, molecular and genetic analysis of patients with CMML, we were able to demonstrate that the most likely candidate driver cell in these patients was also the stem cell rather than any of the down-stream progenitors. Currently, effective therapeutic strategies for MDS or CMML are very limited. Allogeneic stem cell transplantation is the only potential cure and not suitable for most patients. Cancer stem cells, including MDS stem cells are known to be highly quiescent and selectively resistant to therapy. Having demonstrated that both MDS and CMML were driven by stem cells, we developed a novel therapeutic targeting strategy. Using the thrombopoietin receptor agonist, Romiplostim, we were able to activate stem cells and enhance their subsequent sensitivity to chemotherapy dramatically. This approach may facilitate improved remission rates and prevent cancer stem cell driven relapse in many diseases.

A SÃndrome MielodisplÃsica à uma hemopatia clonal de alta prevalÃncia em idosos Anemia à uma caracterÃstica marcante dessa doenÃa Pacientes com dependÃncia de suporte transfusional tem pior prognÃstico Depois das complicaÃÃes relacionadas à prÃpria doenÃa as complicaÃÃes cardiovasculares sÃo a principal causa de morte Novas tÃcnicas ecocardiogrÃficas como o Doppler tecidual e speckle-tracking podem ser Ãteis na anÃlise da funÃÃo cardÃaca nesse grupo Neste estudo foi avaliado um grupo de 34 pacientes e 14 controles saudÃveis emparelhados por sexo e idade sendo submetido à ecocardiograma convencional Doppler tecidual e avaliaÃÃo da deformaÃÃo miocÃrdica (strain) Os pacientes foram subdivididos entre dependentes (13) ou nÃo de suporte transfusional (21) e comparados aos controles Dentre os 13 pacientes do grupo dependentes havia 10 com sobrecarga de ferro (ferritina >1.000 ng/mL) Os pacientes dependentes de suporte transfusional apresentaram maiores volumes diastÃlico e sistÃlico do ventrÃculo esquerdo em relaÃÃo aos controles (p = 0,047 e 0,039) O volume do Ãtrio esquerdo indexado foi maior no grupo de dependentes em relaÃÃo ao grupo controle (p = 0,003) A funÃÃo diastÃlica do ventrÃculo esquerdo (VE) por Doppler convencional e tecidual (razÃo E/A e razÃo E/Eâ) foi normal no grupo de pacientes e nÃo apresentou diferenÃa significante entre os grupos (p = 0,15 e 0,90) Na avaliaÃÃo da funÃÃo sistÃlica do VE por fraÃÃo de ejeÃÃo e por deformaÃÃo miocÃrdica (strain longitudinal global) nÃo houve desvio da normalidade nem diferenÃas entre os grupos (p = 0,71 e 0,097) A espessura do septo interventricular foi maior nos pacientes com ferritina > 1.000 ng/mL (p = 0,012) O nÃvel de hemoglobina mas nÃo o de ferritina apresentou correlaÃÃo com os volumes esquerdos (Ãtrio: r = -0,53 e p = 0,013 / ventrÃculo: r = -0,4 e p = 0,019) Nossa amostra nÃo apresentou disfunÃÃo global nem sistÃlica nem diastÃlica mesmo à anÃlise por novas tÃcnicas de ecocardiograma como Doppler tecidual e deformaÃÃo miocÃrdica (strain) O nÃvel de hemoglobina menor que 8 g/dL foi marcador precoce de pior funÃÃo ventricular nos nossos pacientes com SÃndrome MielodisplÃsica / Myelodysplastic syndrome is a clonal disorder of hematopoietic tissue highly prevalent on elderly Anemia is one of most striking feature of this disorder Patients with transfusional dependence have a poor prognosis Following complications related to the own illness cardiovascular complications are the leading cause of death New echocardiographic techniques such as Tissue Doppler and speckle-tracking may be useful on assessment of the myocardial function in these patients A group with 34 patients and 14 healthy controls matched by sex and age was subjected to conventional echocardiography Tissue Doppler and assessment of myocardial deformation (strain) Patients were divided between those with (13) or without (21) transfusional dependence and compared to controls In the group of transfusional dependence there were 10 subjects with iron overload (serum ferritin levels > 1.000 ng/mL) Those with transfusion dependence had bigger left systolic and diastolic ventricular volumes than controls (p = 0,047 and 0,039) The indexed left atrium volume was larger on those with transfusion dependence compared to controls (p = 0,003) The left ventricular diastolic function assessed by tissue and conventional Doppler (E/A and E/Eâ ratios) was normal in the patient group and has not difference between them (p = 0,15 and 0,9) On the assessment of the systolic left ventricular function by ejection fraction and myocardial deformation (global longitudinal strain) there was no difference between groups or from reference values (p = 0,71 and 0,097) The interventricular septum thickness was larger in the group with serum ferritin > 1.000 ng/mL than patients with ferritin < 1.000 ng/mL (p = 0,012) The hemoglobin level but not ferritin showed linear correlation with the left volumes (atrium: r = -0,53 with p =0,013 / ventricle: r = -0,4 with p = 0,019) Our sample doesnât show diastolic nor systolic global dysfunctions yet with new techniques of tissue Doppler and myocardial deformation (strain). Hemoglobin below 8 g/dL was an early marker of worst ventricular function in our patients with myelodysplastic syndrome

Acute Myeloid Leukemia (AML) is a type of cancer that affects the process of hematopoiesis. In individuals affected with AML, normal blood cells do not develop into red blood cells, white blood cells, and platelets, leading to symptoms such as anemia, neutropenia, and thrombocytopenia. The prognosis of AML is affected by multiple factors including: the genetic make-up of the leukemic cells, age of the affected individual, and underlying blood disorders such as myelodysplastic syndrome (MDS). MDS affects the development of stem cells into red blood cells, white blood cells, and platelets. Due to their clinical heterogeneity, AML and MDS continue to be a challenge that should be investigated in the community hospital setting. Remission rates between patients diagnosed with de-novo AML and patients diagnosed with AML with MDS were compared in a community hospital setting following induction therapy using a retrospective study design. Length of stay between patients diagnosed with de-novo AML and patients diagnosed with AML with MDS was compared during induction therapy. The association of age at diagnosis and number of chromosomal abnormalities to remission status was evaluated in each disease group. The association of blood transfusion requirements and neutropenic fever to length of stay was evaluated in each disease group. There were no statistically significant differences found between disease groups with respect to remission rates and length of stay. There were no statistically significant associations found between blood transfusion requirements and neutropenic fever in each disease group. There was an association found between age at diagnosis and remission status in patients diagnosed with AML with MDS. This indicates that older patients with AML with MDS are less likely to benefit from therapy and achieve complete remission. It is important to consider the small sample size, rare nature of the disease, and other variables that could have contributed to trends seen in the study population. The impact of predictors such as growth factor use and incidence of fungal infections should be investigated in future studies with AML patients. Considering these factors will allow for the development of targeted therapies and mechanisms against drug resistance for affected individuals.

Some myelodysplastic syndrome (MDS) patients present with macrothrombocytopenia due to impaired megakaryocyte (MK) differentiation. Transgenic mice that express the NUP98-HOXD13 (NHD13) fusion gene is a model for MDS and recapitulates the key features of MDS. The study investigated the hypothesis that expression of NHD13 disrupts actin architecture during MK differentiation leading to macrothrombocytopenia. To test the hypothesis, sternums were stained with hematoxylin and eosin, and evaluated by light microscopy to analyze MK morphology in vivo. NHD13 bone marrow (BM) contained many dysplastic MK. BM from wild type (WT) and NHD13 mice were also flushed, cultured in media supplemented with thrombopoietin only or with estrogen to induce proplatelet formation, and MK harvested after 5 days. Harvested MK and BM cores were processed and analyzed by transmission electron microscopy (TEM) to detail the ultrastructural features. TEM of MK revealed that NHD13 leads to formation of an irregular demarcation membrane system and fewer proplatelets. Cultured WT and NHD13 MK were also cytospun onto glass slides, labeled with fluorescent-tagged F-actin, α/β-tubulin and myosin IIa, and their cytoskeleton compared. Interestingly WT MK had actin either distributed evenly or predominantly in the periphery of the cytoplasm, NHD13 MK displayed only the former phenotype. Additionally, proplatelets lacked actin cytoplasmic extensions. The results from the present thesis demonstrate actin expression and architecture are impaired in dysplastic MK expressing the NHD13 leukemic fusion gene and leads to macrothromcytopenia. Understanding the molecular mechanisms of abnormal MK differentiation in MDS is important as many MDS patients die of hemorrhagic complications. / Master of Science

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 4 uppsatser.