Classic and targeted anti-leukaemic agents interfere with the cholesterol biogenesis metagene in acute myeloid leukaemia: Therapeutic implications

Despite significant advances in deciphering the molecular landscape of acute myeloid leukaemia (AML), therapeutic outcomes of this haematological malignancy have only modestly improved over the past decades. Drug resistance and disease recurrence almost invariably occur, highlighting the need for a deeper understanding of these processes. While low O2 compartments, such as bone marrow (BM) niches, are well‐recognized hosts of drug‐resistant leukaemic cells, standard in vitro studies are routinely performed under supra‐physiologic (21% O2, ambient air) conditions, which limits clinical translatability. We hereby identify molecular pathways enriched in AML cells that survive acute challenges with classic or targeted therapeutic agents. Experiments took into account variations in O2 tension encountered by leukaemic cells in clinical settings. Integrated RNA and protein profiles revealed that lipid biosynthesis, and particularly the cholesterol biogenesis branch, is a particularly therapy‐induced vulnerability in AML cells under low O2 states. We also demonstrate that the impact of the cytotoxic agent cytarabine is selectively enhanced by a high‐potency statin. The cholesterol biosynthesis programme is amenable to additional translational opportunities within the expanding AML therapeutic landscape. Our findings support the further investigation of higher‐potency statin (eg rosuvastatin)–based combination therapies to enhance targeting residual AML cells that reside in low O2 environments

Collaborative Research from the Center for Membrane Biosciences

poster abstractThe Center for Membrane Biosciences has been facilitating new research activities between the IUPUI School of Science and IU School of Medicine in the structure, biochemistry, and physiology of biological membranes. Results from two projects resulting from these collaborations are presented. Project 1: Ceramides are sphingolipids involved in the development of lung alveolar cell apoptosis (programmed death) and possibly in the clearance of apoptotic cells by alveolar macrophages. We use a combination of molecular and cellular methods to determine the effect of ceramides on the ability of alveolar macrophages to engulf apoptotic cells. Engulfment experiments of labeled apoptotic Jurkat cells were performed with rat alveolar macrophages (AM) obtained via bronchoalveolar lavage. AM were treated with various ceramide species and efferocytosis was quantified by flow cytometry. Using small-angle X-ray scattering and solid state 2H NMR we determined how ceramides (C6:0, C18:1) affect the molecular organization and the physical properties of model membranes. These studies can lead to a better understanding of the molecular mechanisms responsible for apoptotic cell clearance. If the clearance process is impaired, apoptotic cells may progress to secondary necrosis, resulting in release of harmful cellular contents and tissue inflammation. Project 2: Highly-photostable quantum dots (QD) conjugated to lipids or antibodies can be utilized to explore changes in compartmentalization of the plasma membrane due to hyperinsulinemia using wide field single molecule fluorescence microscopy. Protocols describing the bio-inertness and monovalent binding of QDs to antibodies are outlined, as well as use of confocal fluorescence correlation spectroscopy to determine colloidal stability of CdSe/ZnS QDs in aqueous solution. Tracking experiments on QD-conjugated to transferrin receptors in healthy and insulin-resistant adipocytes detect changes in membrane compartmentalization. The impact of chromium picolinate on receptor mobility was also investigated

Elevations in High-Sensitive Cardiac Troponin T and N-Terminal Prohormone Brain Natriuretic Peptide Levels in the Serum Can Predict the Development of Anthracycline-Induced Cardiomyopathy.

BackgroundAnthracyclines remain the cornerstone of the treatment in many cancers including lymphomas, leukemia and sarcomas, and breast cancer. The cardiomyopathy that develops from anthracyclines can lead to heart failure and decreased survival. Multiple mechanisms are involved in the pathophysiology of anthracycline-induced heart failure.Study questionWe hypothesize that anthracycline-induced cardiac (AIC) pathology can be monitored using a panel of blood biomarkers including high-sensitive cardiac troponin T (hs-cTnT) for myocyte necrosis and N-terminal prohormone brain natriuretic peptide (NT-proBNP) for parietal stress.Study designA prospective, institutionally approved study recruited all patients with cancer scheduled to start anthracycline chemotherapy in the Transylvania University cancer clinics.Measures and outcomesTransthoracic 2D echocardiography and the measurements of NT-proBNP and hs-cTnT plasma levels were performed at the beginning of the study and 3 months and 6 months after anthracycline treatment initiation.ResultsThe plasma levels of hs-cTnT at 3 months (rho = 0.439, P = 0.0001) and 6 months (rho = 0.490, P = 0.0001) are correlated with AIC occurrence. For a cutoff value of hs-cTnT at 3 months > 0.008 ng/mL, we obtained 66.7% sensitivity and 67.9% specificity for developing AIC at 6 months, with a 54.5% positive predictive value and a 87.8% negative predictive value. The NT-proBNP serum levels at 3 months (rho = 0.495, P = 0.0001) and 6 months (rho = 0.638, P = 0.0001) are correlated with an AIC diagnosis at 6 months. For a cutoff value of NT-proBNP at 3 months >118.5 pg/mL, we obtained 80% sensitivity and 79.2% specificity for evolution to AIC at 6 months, with 52.2% positive predictive value and 93.3% negative predictive value.ConclusionsIn anthracycline-treated cancer patients, the increase in plasma levels of NT-proBNP and of hs-cTnT can predict the development of anthracycline-induced cardiomyopathy. Early identification of at-risk patients will potentially allow for targeted dose reductions and will diminish the number of patients developing cardiac pathology

Effects of Lipid Interactions on Model Vesicle Engulfment by Alveolar Macrophages

The engulfment function of macrophages relies on complex molecular interactions involving both lipids and proteins. In particular, the clearance of apoptotic bodies (efferocytosis) is enabled by externalization on the cell target of phosphatidylserine lipids, which activate receptors on macrophages, suggesting that (local) specific lipid-protein interactions are required at least for the initiation of efferocytosis. However, in addition to apoptotic cells, macrophages can engulf foreign bodies that vary substantially in size from a few nanometers to microns, suggesting that nonspecific interactions over a wide range of length scales could be relevant. Here, we use model lipid membranes (made of phosphatidylcholine, phosphatidylserine, and ceramide) and rat alveolar macrophages to show how lipid bilayer properties probed by small-angle x-ray scattering and solid-state 2H NMR correlate with engulfment rates measured by flow cytometry. We find that engulfment of protein-free model lipid vesicles is promoted by the presence of phosphatidylserine lipids but inhibited by ceramide, in accord with a previous study of apoptotic cells. We conclude that the roles of phosphatidylserine and ceramide in phagocytosis is based, at least in part, on lipid-mediated modification of membrane physical properties, including interactions at large length scales as well as local lipid ordering and possible domain formation

Informed Consent: How Much Awareness Is There?

Improving the informed consent process in clinical research is of constant concern to regulatory authorities in the field and presents a challenge for both the specialists and patients involved. Informed consent is a process that should adequately match the complexity of clinical research. In analyzing the behaviour of 68 patients during the informed consent process related to the clinical research performed at Neomed Clinical Center in Brasov, we found that many patients do not ask any questions (35.3%). From those who do, part of the questions (20,6%) referred to general aspects (addressed the form but not the gist) of the clinical trial, some (72,8%) referred to specific aspects of the clinical trial they will attend and others (6,6%) unrelated to the clinical trial. These results suggest a lack of interest, awareness, and understanding of the information presented in the informed consent form. The possible underlying causes of this attitude and its bureaucratic, ethic, and legal implications are discussed