Targeting BCR-ABL1-positive leukaemias: a review article.

Treatment and understanding of BCR::ABL1-positive leukaemias is a precision medicine success story. Our appreciation of the BCR::ABL1 gene and resulting BCR::ABL1 oncoprotein in chronic myeloid leukaemia (CML) and Philadelphia chromosome-positive (Ph+) acute leukaemias, has led to treatment advances associated with exceptional improvements in patient outcomes with normal life expectancy for many patients with chronic phase (CP-)CML. However, despite these major therapeutic advances, the management of Ph+ leukaemias remains complex, with development of specific resistance mutations on treatment, as well as the need for lifelong therapy in most patients due to the persistence of CML stem cells despite prolonged tyrosine kinase inhibitors (TKIs) treatment. BCR::ABL1-specific TKIs are associated with chronic toxicities affecting quality-of-life in many patients but can also result in more serious pulmonary and cardiovascular complications. Dose optimisation is increasingly being used to manage side effects and maintain molecular response in CML patients. Here, we review the development of BCR::ABL1-specific TKIs from the discovery of imatinib in 1996 to the more recent second- and third-generation TKIs and emerging specifically targeting the ABL myristoyl pocket (STAMP) inhibitors. We will also evaluate the current evidence for treatment of BCR::ABL1-positive leukaemias, including TKI discontinuation in optimally responding CP-CML patients.

Multiple myeloma: therapeutic delivery of antibodies and aptamers.

Multiple myeloma is the second most common hematological malignancy in adults, accounting for 2% of all cancer-related deaths in the UK. Current chemotherapy-based regimes are insufficient, as most patients relapse and develop therapy resistance. This review focuses on current novel antibody- and aptamer-based therapies aiming to overcome current therapy limitations, as well as their respective limitations and areas of improvement. The use of computer modeling methods, as a tool to study and improve ligand-receptor alignments for the use of novel therapy development will also be discussed, as it has become a rapid, reliable and comparatively inexpensive method of investigation.

Synergistic cytotoxicity of dual PI3K/mTOR and FLT3 inhibition in FLT3-ITD AML cells.

Acute myeloid leukemia (AML) is an aggressive hematopoietic malignancy, characterized by a heterogeneous genetic landscape and complex clonal evolution, with poor outcomes. Mutation at the internal tandem duplication of FLT3 (FLT3-ITD) is one of the most common somatic alterations in AML, associated with high relapse rates and poor survival due to the constitutive activation of the FLT3 receptor tyrosine kinase and its downstream effectors, such as PI3K signaling. Thus, aberrantly activated FLT3-kinase is regarded as an attractive target for therapy for this AML subtype, and a number of small molecule inhibitors of this kinase have been identified, some of which are approved for clinical practice. Nevertheless, acquired resistance to these molecules is often observed, leading to severe clinical outcomes. Therapeutic strategies to tackle resistance include combining FLT3 inhibitors with other antileukemic agents. Here, we report on the preclinical activity of the combination of the FLT3 inhibitor quizartinib with the dual PI3K/mTOR inhibitor PF-04691502 in FLT3-ITD cells. Briefly, we show that the association of these two molecules displays synergistic cytotoxicity in vitro in FLT3-ITD AML cells, triggering 90% cell death at nanomolar concentrations after 48 h.

Correction: CD93 is expressed on chronic myeloid leukemia stem cells and identifies a quiescent population which persists after tyrosine kinase inhibitor therapy.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

CD93 is expressed on chronic myeloid leukemia stem cells and identifies a quiescent population which persists after tyrosine kinase inhibitor therapy.

The introduction of BCR-ABL tyrosine kinase inhibitors has revolutionized the treatment of chronic myeloid leukemia (CML). A major clinical aim remains the identification and elimination of low-level disease persistence, termed "minimal residual disease". The phenomenon of disease persistence suggests that despite targeted therapeutic approaches, BCR-ABL-independent mechanisms exist which sustain the survival of leukemic stem cells (LSCs). Although other markers of a primitive CML LSC population have been identified in the preclinical setting, only CD26 appears to offer clinical utility. Here we demonstrate consistent and selective expression of CD93 on a lin-CD34+CD38-CD90+ CML LSC population and show in vitro and in vivo data to suggest increased stem cell characteristics, as well as robust engraftment in patient-derived xenograft models in comparison with a CD93- CML stem/progenitor cell population, which fails to engraft. Through bulk and single-cell analyses of selected stem cell and cell survival-specific genes, we confirmed the quiescent character and demonstrate their persistence in a population of CML patient samples who demonstrate molecular relapse on TKI withdrawal. Taken together, our results identify that CD93 is consistently and selectively expressed on a lin-CD34+CD38-CD90+ CML LSC population with stem cell characteristics and may be an important indicator in determining poor TKI responders.

Approaches for targeting self-renewal pathways in cancer stem cells: implications for hematological treatments.

INTRODUCTION: Self-renewal is considered a defining property of stem cells. Self-renewal is essential in embryogenesis and normal tissue repair and homeostasis. However, in cancer, self-renewal pathways, e.g. WNT, NOTCH, Hedgehog and BMP, frequently become de-regulated in stem cells, or more mature progenitor cells acquire self-renewal properties, resulting in abnormal tissue growth and tumorigenesis. Areas covered: This review considers the conserved embryonic self-renewal pathways, including WNT, NOTCH, Hedgehog and BMP. The article describes recent advances in our understanding of these pathways in leukemia and, more specifically, leukemia stem cells (LSC), how these pathways cross-talk and interact with the LSC microenvironment, and discusses the clinical implications and potential therapeutic strategies, both in preclinical and in clinical trials for hematological malignancies. Expert opinion: The conserved embryonic self-renewal pathways are frequently de-regulated in cancer stem cells (CSC), including LSCs. There is significant cross-talk between self-renewal pathways, and their downstream targets, and the microenvironment. Effective targeting of these pathways is challenging due to cross-talk, and importantly, because these pathways are important for normal stem cells as well as CSC, adverse effects on normal tissues may mean a therapeutic window cannot be identified. Nonetheless, several agents targeting these pathways are currently in clinical trials in hematological malignancies.

Stem Cell Guardians - Old and New Perspectives in LSC Biology.

The introduction of tyrosine kinase inhibitors in chronic myeloid leukaemia (CML) has revolutionised disease outcome. However, despite this, progression to blast phase disease is high in those that do not achieve complete cytogenetic and major molecular response on standard therapy. As well as BCR-ABL-dependent mechanisms, disease persistence has been shown to play a key role. Disease persistence suggests that, despite a targeted therapeutic approach, BCR-ABL-independent mechanisms are being exploited to sustain the survival of a small population of cells termed leukaemic stem cells (LSCs). Increasing evidence highlights the importance of self-renewal and survival pathways in this process. This review will focus on the role of stem-cell restricted self-renewal pathways, namely Hedgehog, Notch, and Bone Morphogenic Pathway (BMP). Wingless-Int/ß-Catenin (Wnt/ß-Catenin) signalling will be discussed within a further review in this series in view of its regulatory role in GSK3ß. Further to this, we will highlight the role of key transcriptional regulators, namely p53 and c- MYC, in targeting wider deregulated networks.

Haemolytic anaemia: don't leave it out in the cold.

This clinical case highlights the diagnostic odyssey of an adolescent girl presenting to A&E with non-specific headaches and chest pain. The case will describe the steps in decision making from admission to follow-up.

Low Oxygen Affinity Variant Haemoglobin in an elderly woman presenting with low oxygen saturation.

An asymptomatic 81-year-old woman was referred by her general practitioner regarding a pulse-oximetry oxygen saturation (SpO2) of 74%. An arterial blood gas analysis (ABG) on air showed PaO2 12.9 kPa, oxygen saturation 80%, with normal pH, PaCO2, methaemoglobin and carboxyhaemoglobin levels. After a normal chest x-ray, tinzaparin was administered empirically for possible occult pulmonary embolus. This diagnosis was subsequently excluded with an unremarkable computed tomography pulmonary angiogram (CTPA). She was further investigated as an out patient. DNA globin-gene analysis identified a variant haemoglobin revealed to be haemoglobin Saint Mande (HbSM). Following reassurance regarding the benign nature of her condition, she has remained well.

Novel drug therapies in myeloid leukemia.

Both acute myeloid leukemia and chronic myeloid leukemia are thought to arise from a subpopulation of primitive cells, termed leukemic stem cells that share properties with somatic stem cells. Leukemic stem cells are capable of continued self-renewal, and are resistant to conventional chemotherapy and are considered to be responsible for disease relapse. In recent years, improved understanding of the underlying mechanisms of myeloid leukemia biology has led to the development of novel and targeted therapies. This review focuses on clinically relevant patent applications and their relevance within the known literature in two areas of prevailing therapeutic interest, namely monoclonal antibody therapy and small molecule inhibitors in disease-relevant signaling pathways.

Nanog requires BRD4 to maintain murine embryonic stem cell pluripotency and is suppressed by bromodomain inhibitor JQ1 together with Lefty1.

Embryonic stem cells (ESCs) are maintained in an undifferentiated state through expression of the core transcriptional factors Nanog, Oct4, and Sox2. However, the epigenetic regulation of pluripotency is poorly understood. Differentiation of ESCs is accompanied by a global reduction of panacetylation of histones H3 and H4 suggesting that histone acetylation plays an important role in maintenance of ESC pluripotency. Acetylated lysine residues on histones are read by members of the bromodomain family that includes BET (bromodomain and extraterminal domain) proteins for which highly potent and selective inhibitors have been developed. In this study we demonstrate that the pan-BET bromodomain inhibitor JQ1 induces rapid spontaneous differentiation of murine ESCs by inducing marked transcriptional downregulation of Nanog as well as the stemness markers Lefty1 and Lefty2, but not Myc, often used as a marker of BET inhibitor activity in cancer. We show that the effects of JQ1 are recapitulated by knockdown of the BET family member BRD4 implicating this protein in Nanog regulation. These data are also supported by chromatin immunoprecipitation experiments which confirm BRD4 binding at the Nanog promoter that is known to require acetylation by the histone acetyltransferase MOF for transcriptional activity. In further support of our findings, we show that JQ1 antagonizes the stem cell-promoting effects of the histone deacetylase inhibitors sodium butyrate and valproic acid. Our data suggest that BRD4 is critical for the maintenance of ESC pluripotency and that this occurs primarily through the maintenance of Nanog expression.

Pregnancy in Shwachman-Diamond syndrome: a novel genetic mutation with minimal consequence.

Shwachman-Diamond syndrome (SDS) is a rare inherited bone marrow failure syndrome, characterised by neutropenia, exocrine pancreatic dysfunction and often skeletal abnormalities. To date, and to our knowledge, we report a novel genetic mutation in SDS that, we believe, is associated with minimal consequence,and report the fertility and pregnancy in this individual.