Membrane transporters in cell physiology, cancer metabolism and drug response.

By controlling the passage of small molecules across lipid bilayers, membrane transporters influence not only the uptake and efflux of nutrients, but also the metabolic state of the cell. With more than 450 members, the Solute Carriers (SLCs) are the largest transporter super-family, clustering into families with different substrate specificities and regulatory properties. Cells of different types are, therefore, able to tailor their transporter expression signatures depending on their metabolic requirements, and the physiological importance of these proteins is illustrated by their mis-regulation in a number of disease states. In cancer, transporter expression is heterogeneous, and the SLC family has been shown to facilitate the accumulation of biomass, influence redox homeostasis, and also mediate metabolic crosstalk with other cell types within the tumour microenvironment. This Review explores the roles of membrane transporters in physiological and malignant settings, and how these roles can affect drug response, through either indirect modulation of sensitivity or the direct transport of small-molecule therapeutic compounds into cells.

Peroxisomal compartmentalization of amino acid biosynthesis reactions imposes an upper limit on compartment size.

Cellular metabolism relies on just a few redox cofactors. Selective compartmentalization may prevent competition between metabolic reactions requiring the same cofactor. Is such compartmentalization necessary for optimal cell function? Is there an optimal compartment size? Here we probe these fundamental questions using peroxisomal compartmentalization of the last steps of lysine and histidine biosynthesis in the fission yeast Schizosaccharomyces japonicus. We show that compartmentalization of these NAD+ dependent reactions together with a dedicated NADH/NAD+ recycling enzyme supports optimal growth when an increased demand for anabolic reactions taxes cellular redox balance. In turn, compartmentalization constrains the size of individual organelles, with larger peroxisomes accumulating all the required enzymes but unable to support both biosynthetic reactions at the same time. Our reengineering and physiological experiments indicate that compartmentalized biosynthetic reactions are sensitive to the size of the compartment, likely due to scaling-dependent changes within the system, such as enzyme packing density.

Optimization of energy production and central carbon metabolism in a non-respiring eukaryote.

Most eukaryotes respire oxygen, using it to generate biomass and energy. However, a few organisms have lost the capacity to respire. Understanding how they manage biomass and energy production may illuminate the critical points at which respiration feeds into central carbon metabolism and explain possible routes to its optimization. Here, we use two related fission yeasts, Schizosaccharomyces pombe and Schizosaccharomyces japonicus, as a comparative model system. We show that although S. japonicus does not respire oxygen, unlike S. pombe, it is capable of efficient NADH oxidation, amino acid synthesis, and ATP generation. We probe possible optimization strategies through the use of stable isotope tracing metabolomics, mass isotopologue distribution analysis, genetics, and physiological experiments. S. japonicus appears to have optimized cytosolic NADH oxidation via glycerol-3-phosphate synthesis. It runs a fully bifurcated TCA pathway, sustaining amino acid production. Finally, we propose that it has optimized glycolysis to maintain high ATP/ADP ratio, in part by using the pentose phosphate pathway as a glycolytic shunt, reducing allosteric inhibition of glycolysis and supporting biomass generation. By comparing two related organisms with vastly different metabolic strategies, our work highlights the versatility and plasticity of central carbon metabolism in eukaryotes, illuminating critical adaptations supporting the preferential use of glycolysis over oxidative phosphorylation.

Disparities in mortality among acute myeloid leukemia-related hospitalizations.

Racial and socioeconomic disparities have become apparent in acute myeloid leukemia (AML) outcomes. We conducted a retrospective cohort study of hospitalizations for adults with a diagnosis of AML from 2009 to 2018 in the Nationwide Inpatient Sample (NIS). We categorized patients' ages in groups of <60 years and ≥60 years and stratified them by reported race/ethnicity. Exposures of interest were patient sociodemographics, hospital characteristics, and Elixhauser-comorbidity Index. Outcome of interest was in-hospital death. Statistical analyses included survey logistic regression to generate adjusted odds ratios (aORs) and 95% confidence intervals (CIs) to quantify the independent associations between patient characteristics and mortality. Of 622,417 AML-related hospitalizations, 57.6% were in patients ≥60 years. The overall rate of in-hospital death was 9.4%. Compared to patients <60, older patients experienced a higher rate of in-hospital death. In both age groups and in all ethnicities, mortality decreased over time. Differences in mortality were observed based on gender, payer, hospital location, and teaching status. For hospitalizations in patients ≥60, NH-Black race was associated with inferior in-hospital death outcomes (OR 1.17; CI 1.08-1.28). Urban teaching hospitals were associated with a 38% increase (OR 1.38; CI 1.06-1.80) in inpatient mortality in patients <60 and a 15% decrease (OR 0.85; CI 0.77-0.95) in inpatient mortality in patients ≥60. Our results highlight the increased need to recognize the role of race/ethnicity and socioeconomic factors and their contribution to disparate outcomes in AML.

Health Disparities Experienced by Hispanic Americans with Multiple Myeloma: A Systematic Review.

Health disparities in multiple myeloma (MM) disproportionately affect minorities. Characterization of health disparities encountered by Hispanic Americans with MM is necessary to identify gaps and inform future strategies to eliminate them. We performed a systematic review of publications that described health disparities relevant to Hispanic Americans with MM through December 2021. We included all original studies which compared incidence, treatment, and/or outcomes of Hispanic Americans with other ethnic groups. Eight hundred and sixty-eight articles were identified of which 22 original study articles were included in our systematic review. The number of publications varied over time with the highest number of studies (32%) published in 2021. Most of the published studies (59%) reported worse outcomes for Hispanic Americans with MM compared to other ethnic groups. There is growing evidence that Hispanic Americans with MM are facing a multitude of disparities that require immediate attention and solutions.

A Right Atrial Mass with Fever and Cutaneous Nodules.

Primary cardiac tumors, although exceedingly rare, should be considered in the differential diagnosis during workup of any cardiac mass. Extranodal cardiac lymphomas have a natural aggressive course due to delayed diagnosis. We present a 71-year-old male with a dual-chamber pacemaker who presented with fevers and new cutaneous nodules. He was found to have a right atrial primary anaplastic large-cell lymphoma and had a complete metabolic response after chemotherapy. Our case highlights the importance of a multimodality approach in the diagnosis of cardiac tumors and during follow-up after treatment.

Impact of COVID-19 on Hematology-Oncology Trainees: A Quantitative and Qualitative Assessment.

PURPOSE: Graduate medical and research training has drastically changed during the COVID-19 pandemic, with widespread implementation of virtual learning, redeployment from core rotations to the care of patients with COVID-19, and significant emotional and physical stressors. The specific experience of hematology-oncology (HO) fellows during the COVID-19 pandemic is not known. METHODS: We conducted a mixed-methods study using a survey of Likert-style and open-ended questions to assess the training experience and well-being of HO fellows, including both clinical and postdoctoral trainee members of the American Society of Hematology and ASCO. RESULTS: A total of 2,306 surveys were distributed by e-mail; 548 (23.8%) fellows completed the survey. Nearly 40% of fellows felt that they had not received adequate mental health support during the pandemic, and 22% reported new symptoms of burnout. Pre-existing burnout before the pandemic, COVID-19-related clinical work, and working in a primary research or nonclinical setting were associated with increased burnout on multivariable logistic regression. Qualitative thematic analysis of open-ended responses revealed significant concerns about employment after training completion, perceived variable quality of virtual education and board preparation, loss of clinical opportunities to prepare for independent clinical practice, inadequate grant funding opportunities in part because of shifting research priorities, variable productivity, and mental health or stress during the pandemic. CONCLUSION: HO fellows have been profoundly affected by the pandemic, and our data illustrate multiple avenues for fellowship programs and national organizations to support both clinical and postdoctoral trainees.

Cancer Therapy-Related Cardiac Dysfunction: An Overview for the Clinician.

Cancer therapy-related cardiac dysfunction (CTRCD) is one of the most feared and undesirable side effects of chemotherapy, occurring in approximately 10% of the patients. It can be classified as direct (dose-dependent vs dose-independent) or indirect, either case being potentially permanent or reversible. Risk assessment, recognition, and prevention of CTRCD are crucial.

Acquired Von Willebrand's Syndrome in Systemic Lupus Erythematosus.

Acquired von Willebrand syndrome (AVWS) is an uncommon, underdiagnosed, and heterogeneous disease which is increasingly recognized as a cause of bleeding diatheses. Systemic lupus erythematosus (SLE) is an infrequent cause of AVWS. Herein, we report a case of AVWS diagnosed during the initial presentation of SLE in a previously healthy young man with no family history of bleeding diathesis who presented with worsening epistaxis, gastrointestinal bleeding, and anasarca. He was found to have severe anemia and prolonged activated partial thromboplastin time (aPTT) with severely decreased levels of von Willebrand factor (VWF) measurements in addition to markedly decreased factor VIII levels. Further evaluation revealed nephrotic syndrome and interstitial lung disease due to SLE. He initially received combination therapy with intravenous immunoglobulin (IVIG) and von Willebrand factor/factor VIII concentrates without significant improvement. Treatment with steroids, cyclophosphamide, and rituximab was followed by clinical improvement evidenced by cessation of bleeding. The short follow-up did not allow us to definitely prove the therapeutic effect of immunosuppressive treatment on AVWS in SLE patients. This case adds to the literature supporting the relationship between AVWS and SLE and highlights the importance of combination therapy in the treatment of severe AVWS as well as the role of IVIG, cyclophosphamide, and rituximab in AVWS associated with SLE.