FLT3 is genetically essential for ITD-mutated leukemic stem cells but dispensable for human hematopoietic stem cells.

Leukemic stem cells (LSCs) fuel acute myeloid leukemia (AML) growth and relapse, but therapies tailored towards eradicating LSCs without harming normal hematopoietic stem cells (HSCs) are lacking. FLT3 is considered an important therapeutic target due to frequent mutation in AML and association with relapse. However, there has been limited clinical success with FLT3 drug targeting, suggesting either that FLT3 is not a vulnerability in LSC, or that more potent inhibition is required, a scenario where HSC toxicity could become limiting.

A Call to Arms: Wartime Blood Donor Recruitment.

To ensure an adequate blood supply, blood collection agencies must design campaigns to recruit and maintain an active donor pool. Such campaigns generally appeal to altruism and humanitarianism, which donors most commonly cite as their reasons for donating. However, large donor registries and the widespread recruitment campaigns that sustain them did not become a necessity until the technology for the collection, storage, and transfusion of blood had advanced to a point that enabled the establishment of transfusion services that could provide large amounts of stored blood to meet high demands.

Gene expression and mutation-guided synthetic lethality eradicates proliferating and quiescent leukemia cells.

Quiescent and proliferating leukemia cells accumulate highly lethal DNA double-strand breaks that are repaired by 2 major mechanisms: BRCA-dependent homologous recombination and DNA-dependent protein kinase-mediated (DNA-PK-mediated) nonhomologous end-joining, whereas DNA repair pathways mediated by poly(ADP)ribose polymerase 1 (PARP1) serve as backups. Here we have designed a personalized medicine approach called gene expression and mutation analysis (GEMA) to identify BRCA- and DNA-PK-deficient leukemias either directly, using reverse transcription-quantitative PCR, microarrays, and flow cytometry, or indirectly, by the presence of oncogenes such as BCR-ABL1. DNA-PK-deficient quiescent leukemia cells and BRCA/DNA-PK-deficient proliferating leukemia cells were sensitive to PARP1 inhibitors that were administered alone or in combination with current antileukemic drugs.

A 17-gene stemness score for rapid determination of risk in acute leukaemia.

Refractoriness to induction chemotherapy and relapse after achievement of remission are the main obstacles to cure in acute myeloid leukaemia (AML). After standard induction chemotherapy, patients are assigned to different post-remission strategies on the basis of cytogenetic and molecular abnormalities that broadly define adverse, intermediate and favourable risk categories. However, some patients do not respond to induction therapy and another subset will eventually relapse despite the lack of adverse risk factors.

TTI-621 (SIRPαFc): A CD47-Blocking Innate Immune Checkpoint Inhibitor with Broad Antitumor Activity and Minimal Erythrocyte Binding.

The ubiquitously expressed transmembrane glycoprotein CD47 delivers an anti-phagocytic (do not eat) signal by binding signal-regulatory protein α (SIRPα) on macrophages. CD47 is overexpressed in cancer cells and its expression is associated with poor clinical outcomes. TTI-621 (SIRPαFc) is a fully human recombinant fusion protein that blocks the CD47-SIRPα axis by binding to human CD47 and enhancing phagocytosis of malignant cells.

An Integrated Analysis of Heterogeneous Drug Responses in Acute Myeloid Leukemia That Enables the Discovery of Predictive Biomarkers.

Many promising new cancer drugs proceed through preclinical testing and early-phase trials only to fail in late-stage clinical testing. Thus, improved models that better predict survival outcomes and enable the development of biomarkers are needed to identify patients most likely to respond to and benefit from therapy. Here, we describe a comprehensive approach in which we incorporated biobanking, xenografting, and multiplexed phospho-flow (PF) cytometric profiling to study drug response and identify predictive biomarkers in acute myeloid leukemia (AML) patients.

miR-126 Regulates Distinct Self-Renewal Outcomes in Normal and Malignant Hematopoietic Stem Cells.

To investigate miRNA function in human acute myeloid leukemia (AML) stem cells (LSC), we generated a prognostic LSC-associated miRNA signature derived from functionally validated subpopulations of AML samples. For one signature miRNA, miR-126, high bioactivity aggregated all in vivo patient sample LSC activity into a single sorted population, tightly coupling miR-126 expression to LSC function. Through functional studies, miR-126 was found to restrain cell cycle progression, prevent differentiation, and increase self-renewal of primary LSC in vivo.

Bringing Leukemia Stem Cells into the Clinic.

Outcomes in acute myeloid leukemia (AML) remain poor due to high rates of relapse. Thus, there is an urgent unmet medical need for new therapies that can more effectively kill the leukemia stem cells (LSC) and recently recognized preleukemic hematopoietic stem cells (preL-HSC) that can drive relapsed disease. In order to develop such therapies, a better understanding of the biology of these stem cell populations is required.

Inhibition of the Mitochondrial Protease ClpP as a Therapeutic Strategy for Human Acute Myeloid Leukemia.

From an shRNA screen, we identified ClpP as a member of the mitochondrial proteome whose knockdown reduced the viability of K562 leukemic cells. Expression of this mitochondrial protease that has structural similarity to the cytoplasmic proteosome is increased in leukemic cells from approximately half of all patients with AML. Genetic or chemical inhibition of ClpP killed cells from both human AML cell lines and primary samples in which the cells showed elevated ClpP expression but did not affect their normal counterparts.

Identification of pre-leukaemic haematopoietic stem cells in acute leukaemia.

In acute myeloid leukaemia (AML), the cell of origin, nature and biological consequences of initiating lesions, and order of subsequent mutations remain poorly understood, as AML is typically diagnosed without observation of a pre-leukaemic phase. Here, highly purified haematopoietic stem cells (HSCs), progenitor and mature cell fractions from the blood of AML patients were found to contain recurrent DNMT3A mutations (DNMT3A(mut)) at high allele frequency, but without coincident NPM1 mutations (NPM1c) present in AML blasts. DNMT3A(mut)-bearing HSCs showed a multilineage repopulation advantage over non-mutated HSCs in xenografts, establishing their identity as pre-leukaemic HSCs.

Unusual dermal pleomorphic calcifications in a case of inflammatory breast carcinoma.

Inflammatory breast carcinoma is a rare and aggressive type of breast cancer that is definitively diagnosed by histologic evaluation showing invasive tumor cells in the dermal lymphatic system. Associated dermal calcifications are not typically identified. We report an unusual case in which inflammatory breast carcinoma led to the presence of pleomorphic dermal calcifications identified on the initial mammographic examination.

Fat necrosis in the breast from methylene blue dye injection.

Sentinel lymph node biopsy has become the standard of clinical care in staging axillary lymph nodes for breast carcinoma. While deemed safe and effective, methylene blue dye has been associated with infection, fibrosis, and skin and fat necrosis. The variable appearance of surgical dye-related fibrosis and fat necrosis on imaging studies poses a challenge to both radiologists and clinicians.

Methylation of the TERT promoter and risk stratification of childhood brain tumours: an integrative genomic and molecular study.

Background: Identification of robust biomarkers of malignancy and methods to establish disease progression is a major goal in paediatric neuro-oncology. We investigated whether methylation of the TERT promoter can be a biomarker for malignancy and patient outcome in paediatric brain tumours.

Methods: For the discovery cohort, we used samples obtained from patients with paediatric brain tumours and individuals with normal brain tissues stored at the German Cancer Research Center (Heidelberg, Germany).

Lymphoma in the breast.

Lymphoma is a rare neoplasm in the breast. In this location, it may be primary or secondary, depending on whether there is lymphoma elsewhere in the body. The most common presentation of breast lymphoma is a painless palpable mass, indistinguishable from that of breast carcinoma, although the treatment regimens for these two neoplasms differ vastly.

Targeting SIRPα in cancer.

Strategies to harness the patient's immune system to fight cancer have mainly involved adoptive T-cell transfer. We and others have recently highlighted an alternative immunotherapeutic approach to cancer that consists of enhancing the macrophage-mediated clearance of leukemia cells through the blockade of inhibitory signals transmitted by signal regulatory protein α (SIRPα).

Cancer patient perceptions on the ethical and legal issues related to biobanking.

Background: Understanding the perception of patients on research ethics issues related to biobanking is important to enrich ethical discourse and help inform policy.

Methods: We examined the views of leukemia patients undergoing treatment in clinics located in the Princess Margaret Hospital in Toronto, Ontario, Canada. An initial written survey was provided to 100 patients (64.

Lysosomal disruption preferentially targets acute myeloid leukemia cells and progenitors.

Despite efforts to understand and treat acute myeloid leukemia (AML), there remains a need for more comprehensive therapies to prevent AML-associated relapses. To identify new therapeutic strategies for AML, we screened a library of on- and off-patent drugs and identified the antimalarial agent mefloquine as a compound that selectively kills AML cells and AML stem cells in a panel of leukemia cell lines and in mice. Using a yeast genome-wide functional screen for mefloquine sensitizers, we identified genes associated with the yeast vacuole, the homolog of the mammalian lysosome.

Disruption of SIRPα signaling in macrophages eliminates human acute myeloid leukemia stem cells in xenografts.

Although tumor surveillance by T and B lymphocytes is well studied, the role of innate immune cells, in particular macrophages, is less clear. Moreover, the existence of subclonal genetic and functional diversity in some human cancers such as leukemia underscores the importance of defining tumor surveillance mechanisms that effectively target the disease-sustaining cancer stem cells in addition to bulk cells. In this study, we report that leukemia stem cell function in xenotransplant models of acute myeloid leukemia (AML) depends on SIRPα-mediated inhibition of macrophages through engagement with its ligand CD47.

Inhibition of the LSD1 (KDM1A) demethylase reactivates the all-trans-retinoic acid differentiation pathway in acute myeloid leukemia.

Acute promyelocytic leukemia (APL), a cytogenetically distinct subtype of acute myeloid leukemia (AML), characterized by the t(15;17)-associated PML-RARA fusion, has been successfully treated with therapy utilizing all-trans-retinoic acid (ATRA) to differentiate leukemic blasts. However, among patients with non-APL AML, ATRA-based treatment has not been effective. Here we show that, through epigenetic reprogramming, inhibitors of lysine-specific demethylase 1 (LSD1, also called KDM1A), including tranylcypromine (TCP), unlocked the ATRA-driven therapeutic response in non-APL AML.

Inhibition of mitochondrial translation as a therapeutic strategy for human acute myeloid leukemia.

To identify FDA-approved agents targeting leukemic cells, we performed a chemical screen on two human leukemic cell lines and identified the antimicrobial tigecycline. A genome-wide screen in yeast identified mitochondrial translation inhibition as the mechanism of tigecycline-mediated lethality. Tigecycline selectively killed leukemia stem and progenitor cells compared to their normal counterparts and also showed antileukemic activity in mouse models of human leukemia.

Evolution of human BCR-ABL1 lymphoblastic leukaemia-initiating cells.

Many tumours are composed of genetically diverse cells; however, little is known about how diversity evolves or the impact that diversity has on functional properties. Here, using xenografting and DNA copy number alteration (CNA) profiling of human BCR-ABL1 lymphoblastic leukaemia, we demonstrate that genetic diversity occurs in functionally defined leukaemia-initiating cells and that many diagnostic patient samples contain multiple genetically distinct leukaemia-initiating cell subclones. Reconstructing the subclonal genetic ancestry of several samples by CNA profiling demonstrated a branching multi-clonal evolution model of leukaemogenesis, rather than linear succession.

Good cells gone bad: the cellular origins of cancer.

One issue in human cancer research that remains largely unresolved is the identity of the normal cell type in which tumorigenesis begins. Knowledge of the starting cell populations targeted by transforming events is crucial for characterizing early neoplastic changes and understanding how normal cellular processes become disrupted during cancer development. Recent focus on cancer stem cells (CSCs) has been accompanied by the frequent assumption that these cells derive from normal stem cells.

Evaluating therapeutic efficacy against cancer stem cells: new challenges posed by a new paradigm.

Current measures of anticancer drug efficacy reflect bulk cell killing and are poorly suited to detect activity against cancer stem cells (CSCs), which sustain tumor growth. The CSC paradigm necessitates a reexamination of methodologies used to evaluate clinical efficacy of anticancer therapies, as well as strategies employed during preclinical drug development.

Comment on "Tumor growth need not be driven by rare cancer stem cells".

Kelly et al. (Brevia, 20 July 2007, p. 337) questioned xenotransplant experiments supporting the cancer stem cell (CSC) hypothesis because they found a high frequency of leukemia-initiating cells (L-IC) in some transgenic mouse models.

Polymorphism in Sirpa modulates engraftment of human hematopoietic stem cells.

Graft failure in the transplantation of hematopoietic stem cells occurs despite donor-host genetic identity of human leukocyte antigens, suggesting that additional factors modulate engraftment. With the nobese diabetic (NOD)-severe combined immunodeficiency (SCID) xenotransplantation model, we found that the NOD background allowed better hematopoietic engraftment than did other strains with equivalent immunodeficiency-related mutations. We used positional genetics to characterize the molecular basis for this strain specificity and found that the NOD Sirpa allele conferred support for human hematopoiesis.