60 research outputs found

    E2F1 induction following DNA damage and oncogene activation

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    The transcription factor E2F1, a critical target of the tumour suppressor pRb, is deregulated in most human cancers. Oncogenes have been shown to deregulate E2F1 through inhibition of pRB and deregulation of E2F1 is an event that occurs in most human cancers. The essential role of E2F1 in apoptosis is well documented and deregulated E2F1 can enhance drug induced death. E2F1 is induced by various chemotherapeutic drugs and this induction, in addition with oncogenic stress, contributes to increased chemosensitivity. Cells expressing the adenovirus early region 1A (E1A) oncogene have been used as a tool to identify cellular regulatory pathways that modulate chemosensitivity. E1A sensitises cells to the induction of apoptosis by diverse stimuli, including many chemotherapeutic drugs. These E1A activities are mediated through binding the RB family proteins (pRb, p107 and p130) and via the E1A N-terminal domain that interacts with different cellular protein complexes including the p300/CBP transcriptional activator and p400/TRRAP chromatin-remodeling complex. The results presented here illustrate novel mechanisms of E2F1 induction both by oncogenes and chemotherapeutic drugs. Two minimal domains of E2F1 are described that are induced following DNA damage via mechanism(s) not previously identified. In addition, data are presented which show that E1A expression not only deregulates E2F1, but also elevates E2F1 levels. E1A is dependent on interaction with RB protein to induce E2F1 levels and this elevation contributes to cell death. Using previously described protein binding deficient truncations of E1A, we demonstrate that E1A binding to the p400/TRRAP protein complex is also critical for the induction of E2F1. E1A binding to p400/TRRAP was also critical in sensitizing these cells to drug induced apoptosis. Suppression of p400 using siRNA had similar affect on E2F1 induction and caused an increase in drug sensitivity indicating that E1A inhibits p400 function. These results contribute to the understanding of how activation of the E2F1 pathway may be targeted therapeutically to enhance chemotherapy-induced tumour cell death

    The leukaemia stem cell: similarities, differences and clinical prospects in CML and AML

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    For two decades, leukaemia stem cells (LSCs) in chronic myeloid leukaemia (CML) and acute myeloid leukaemia (AML) have been advanced paradigms for the cancer stem cell field. In CML, the acquisition of the fusion tyrosine kinase BCR–ABL1 in a haematopoietic stem cell drives its transformation to become a LSC. In AML, LSCs can arise from multiple cell types through the activity of a number of oncogenic drivers and pre-leukaemic events, adding further layers of context and genetic and cellular heterogeneity to AML LSCs not observed in most cases of CML. Furthermore, LSCs from both AML and CML can be refractory to standard-of-care therapies and persist in patients, diversify clonally and serve as reservoirs to drive relapse, recurrence or progression to more aggressive forms. Despite these complexities, LSCs in both diseases share biological features, making them distinct from other CML or AML progenitor cells and from normal haematopoietic stem cells. These features may represent Achilles’ heels against which novel therapies can be developed. Here, we review many of the similarities and differences that exist between LSCs in CML and AML and examine the therapeutic strategies that could be used to eradicate them

    E2F1 induction following DNA damage and oncogene activation

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    The transcription factor E2F1, a critical target of the tumour suppressor pRb, is deregulated in most human cancers. Oncogenes have been shown to deregulate E2F1 through inhibition of pRB and deregulation of E2F1 is an event that occurs in most human cancers. The essential role of E2F1 in apoptosis is well documented and deregulated E2F1 can enhance drug induced death. E2F1 is induced by various chemotherapeutic drugs and this induction, in addition with oncogenic stress, contributes to increased chemosensitivity. Cells expressing the adenovirus early region 1A (E1A) oncogene have been used as a tool to identify cellular regulatory pathways that modulate chemosensitivity. E1A sensitises cells to the induction of apoptosis by diverse stimuli, including many chemotherapeutic drugs. These E1A activities are mediated through binding the RB family proteins (pRb, p107 and p130) and via the E1A N-terminal domain that interacts with different cellular protein complexes including the p300/CBP transcriptional activator and p400/TRRAP chromatin-remodeling complex. The results presented here illustrate novel mechanisms of E2F1 induction both by oncogenes and chemotherapeutic drugs. Two minimal domains of E2F1 are described that are induced following DNA damage via mechanism(s) not previously identified. In addition, data are presented which show that E1A expression not only deregulates E2F1, but also elevates E2F1 levels. E1A is dependent on interaction with RB protein to induce E2F1 levels and this elevation contributes to cell death. Using previously described protein binding deficient truncations of E1A, we demonstrate that E1A binding to the p400/TRRAP protein complex is also critical for the induction of E2F1. E1A binding to p400/TRRAP was also critical in sensitizing these cells to drug induced apoptosis. Suppression of p400 using siRNA had similar affect on E2F1 induction and caused an increase in drug sensitivity indicating that E1A inhibits p400 function. These results contribute to the understanding of how activation of the E2F1 pathway may be targeted therapeutically to enhance chemotherapy-induced tumour cell death.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

    Metabolism in stem cell driven leukaemia: parallels between haematopoiesis and immunity

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    Our understanding of cancer metabolism spans from its role in cellular energetics and supplying the building blocks necessary for proliferation, to maintaining cellular redox and regulating the cellular epigenome and transcriptome. Cancer metabolism, once thought to be solely driven by upregulated glycolysis, is now known to comprise of multiple pathways with great plasticity in response to extrinsic challenges. Furthermore, cancer cells can modify their surrounding niche during disease initiation, maintenance and metastasis, contributing to therapy resistance. Leukaemia is a paradigm model of stem cell driven cancer. Here, we review how leukaemia remodels the niche and rewires its metabolism with particular attention paid to therapy-resistant stem cells. Specifically, we aim to give a global, non-exhaustive overview of key metabolic pathways. By contrasting the metabolic rewiring required by myeloid leukaemic stem cells with that required for haematopoiesis and immune cell function, we highlight the metabolic features they share. This is a critical consideration when contemplating anti-cancer metabolic inhibitor options, especially in the context of anti-cancer immune therapies. Finally, we examine pathways that have not been studied in leukaemia but are critical in solid cancers in the context of metastasis and interaction with new niches. These studies also offer detailed mechanisms that have yet to be investigated in leukaemia. Given that cancer (and normal) cells can meet their energy requirements by not only upregulating metabolic pathways, but also utilising systemically available substrates, we aim to inform how interlinked these metabolic pathways are, both within leukaemic cells and between cancer cells and their niche

    The Ins and Outs of Autophagy and Metabolism in Hematopoietic and Leukemic Stem Cells: Food for Thought

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    Discovered over fifty years ago, autophagy is a double-edged blade. On one hand, it regulates cellular energy sources by “cannibalization” of its own cellular components, feeding on proteins and other unused cytoplasmic factors. On the other, it is a recycling process that removes dangerous waste from the cytoplasm keeping the cell clean and healthy. Failure of the autophagic machinery is translated in dysfunction of the immune response, in aging, and in the progression of pathologies such as Parkinson disease, diabetes, and cancer. Further investigation identified autophagy with a protective role in specific types of cancer, whereas in other cases it can promote tumorigenesis. Evidence shows that treatment with chemotherapeutics can upregulate autophagy in order to maintain a stable intracellular environment promoting drug resistance and cell survival. Leukemia, a blood derived cancer, represents one of the malignancies in which autophagy is responsible for drug treatment failure. Inhibition of autophagy is becoming a strategic target for leukemic stem cell (LSC) eradication. Interestingly, the latest findings demonstrate that LSCs show higher levels of mitochondrial metabolism compared to normal stem cells. With this review, we aim to explore the links between autophagy and metabolism in the hematopoietic system, with special focus on primitive LSCs

    Mitochondrial metabolism as a potential therapeutic target in myeloid leukaemia

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    While the understanding of the genomic aberrations that underpin chronic and acute myeloid leukaemia (CML and AML) has allowed the development of therapies for these diseases, limitations remain. These become apparent when looking at the frequency of treatment resistance leading to disease relapse in leukaemia patients. Key questions regarding the fundamental biology of the leukaemic cells, such as their metabolic dependencies, are still unresolved. Even though a majority of leukaemic cells are killed during initial treatment, persistent leukaemic stem cells (LSCs) and therapy-resistant cells are still not eradicated with current treatments, due to various mechanisms that may contribute to therapy resistance, including cellular metabolic adaptations. In fact, recent studies have shown that LSCs and treatment-resistant cells are dependent on mitochondrial metabolism, hence rendering them sensitive to inhibition of mitochondrial oxidative phosphorylation (OXPHOS). As a result, rewired energy metabolism in leukaemic cells is now considered an attractive therapeutic target and the significance of this process is increasingly being recognised in various haematological malignancies. Therefore, identifying and targeting aberrant metabolism in drug-resistant leukaemic cells is an imperative and a relevant strategy for the development of new therapeutic options in leukaemia. In this review, we present a detailed overview of the most recent studies that present experimental evidence on how leukaemic cells can metabolically rewire, more specifically the importance of OXPHOS in LSCs and treatment-resistant cells, and the current drugs available to target this process. We highlight that uncovering specific energy metabolism dependencies will guide the identification of new and more targeted therapeutic strategies for myeloid leukaemia

    Auto-commentary on: “Targeting mitochondrial oxidative phosphorylation eradicates therapy-resistant chronic myeloid leukemia stem cells”

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    We have recently uncovered an abnormal increase in mitochondrial oxidative metabolism in therapy-resistant chronic myeloid leukaemia stem cells (LSCs). By simultaneously disrupting mitochondrial respiration and inhibiting BCR-ABL kinase activity using the antibiotic tigecycline and imatinib respectively, we effectively eradicated LSCs and prevented disease relapse in pre-clinical animal models

    Folate metabolism: a re-emerging therapeutic target in haematological cancers

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    Folate-mediated one carbon (1C) metabolism supports a series of processes that are essential for the cell. Through a number of interlinked reactions happening in the cytosol and mitochondria of the cell, folate metabolism contributes to de novo purine and thymidylate synthesis, to the methionine cycle and redox defence. Targeting the folate metabolism gave rise to modern chemotherapy, through the introduction of antifolates to treat paediatric leukaemia. Since then, antifolates, such as methotrexate and pralatrexate have been used to treat a series of blood cancers in clinic. However, traditional antifolates have many deleterious side effects in normal proliferating tissue, highlighting the urgent need for novel strategies to more selectively target 1C metabolism. Notably, mitochondrial 1C enzymes have been shown to be significantly upregulated in various cancers, making them attractive targets for the development of new chemotherapeutic agents. In this article, we present a detailed overview of folate-mediated 1C metabolism, its importance on cellular level and discuss how targeting folate metabolism has been exploited in blood cancers. Additionally, we explore possible therapeutic strategies that could overcome the limitations of traditional antifolates

    Utilizing stimulated Raman scattering microscopy to study intracellular distribution of label-free ponatinib in live cells

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    Stimulated Raman scattering (SRS) microscopy represents a powerful method for imaging label-free drug dis-tribution with high resolution. SRS was applied to image label-free ponatinib with high sensitivity and speci-ficity in live human chronic myeloid leukemia (CML) cell lines. This was achieved at biologically relevant, na-nomolar concentrations; allowing determination of ponatinib uptake and sequestration into lysosomes during the development of acquired drug resistance and an improved understanding of target engagement

    Targeting mitochondrial oxidative phosphorylation eradicates therapy-resistant chronic myeloid leukemia stem cells

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    Treatment of chronic myeloid leukemia (CML) with imatinib mesylate and other second-and/or third-generation c-Abl-specific tyrosine kinase inhibitors (TKIs) has substantially extended patient survival(1). However, TKIs primarily target differentiated cells and do not eliminate leukemic stem cells (LSCs)(2-4). Therefore, targeting minimal residual disease to prevent acquired resistance and/or disease relapse requires identification of new LSC-selective target(s) that can be exploited therapeutically(5,6). Considering that malignant transformation involves cellular metabolic changes, which may in turn render the transformed cells susceptible to specific assaults in a selective manner(7), we searched for such vulnerabilities in CML LSCs. We performed metabolic analyses on both stem cell-enriched (CD34(+) and CD34(+)CD38(-)) and differentiated (CD34(-)) cells derived from individuals with CML, and we compared the signature of these cells with that of their normal counterparts. Through combination of stable isotope-assisted metabolomics with functional assays, we demonstrate that primitive CML cells rely on upregulated oxidative metabolism for their survival. We also show that combination treatment with imatinib and tigecycline, an antibiotic that inhibits mitochondrial protein translation, selectively eradicates CML LSCs both in vitro and in a xenotransplantation model of human CML. Our findings provide a strong rationale for investigation of the use of TKIs in combination with tigecycline to treat patients with CML with minimal residual disease
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