What’s New in Research – July 2018
Eat ’Em Up: Next-Generation Therapeutic Helps Immune Cells Detect, Destroy Cancer
Supramolecule provides a double whammy to knock out cancer’s ‘eat-me-not’ signaling, keep macrophages on the attack
Macrophages — immune cells that engulf and digest particles and pathogens — provide a first line of defense against bacteria and viruses and can also help destroy cancer cells. Macrophages play a paradoxical role, with M1 macrophages rousing the immune system to action and M2 macrophages quelling inflammation. Researchers have found that cancer cells evade destruction by macrophages in two ways – by converting cells to become docile, M2 macrophages, and by sending out an “eat me not” signal that tricks M1 macrophages into letting them be. Investigators from Brigham and Women’s Hospital have developed a therapeutic that delivers a double whammy to knock out both mechanisms. In preclinical models, the new approach has yielded promising results. The team’s findings are published today in Nature Biomedical Engineering.
“Clinicians are increasingly realizing that one drug or a one-size-fits-all approach is not enough when combatting cancer, and that a combination immunotherapy, such as blocking two distinct targets in the same immune cell, is the future of immuno-oncology. Our approach capitalizes on this concept,” said co-corresponding author Ashish Kulkarni, PhD, a former instructor in the Division of Engineering in Medicine at BWH and assistant professor in the Department of Chemical Engineering at University of Massachusetts, Amherst.
Kulkarni and colleagues have previously reported on the design and engineering of supramolecules – therapeutics that are built from component molecules that click together like building blocks. To reinvigorate macrophages, the team designed a supramolecule that could block the “don’t eat me” signal that cancer cells can produce and simultaneously inhibit signaling that converts macrophages to M2 subtype.
The researchers tested the supramolecular therapeutic in animal models of aggressive forms of breast cancer and skin cancer, comparing their drug directly with a drug currently available in the clinic. Mice that were untreated formed large tumors by Day 10. Mice treated with currently available therapies showed decreased tumor growth. But mice treated with the new supramolecular therapy had complete inhibition of tumor growth. The team also reported an increase in survival and a significant reduction in metastatic nodes.
“We can actually see macrophages eating cancer cells,” said co-corresponding author Shiladitya Sengupta, PhD, BWH associate bioengineer and assistant professor of medicine at Harvard Medical School, citing confocal microscopy images published in the paper that show macrophages (red) engulfing cancer cells (green).
The researchers plan to continue testing the new therapy in preclinical models to evaluate safety, efficacy and dosage. The supramolecular therapy they have designed has been licensed and they hope to move the therapeutic into clinical trials in the years ahead should preclinical testing continue to show promise.
Funding for this work was provided by a Department of Defense Breakthrough Award (BC132168), an American Lung Association Innovation Award (LCD-259932-N), an NCI UO1 (CA214411), a National Cancer Institute of the National Institutes of Health (P50CA168504)
and Hearst Foundation/Brigham and Women’s Hospital Young Investigator Award.
Paper cited: Kulkarni, Ashish et al. “A designer self-assembled supramolecule amplifies macrophage immune responses against aggressive cancer” Nature Biomedical Engineering DOI:10.1038/s41551-018-0254-6
Study Charts the Landscape of Mosaic Chromosomal Alterations in Blood Cells
New technique detects mutations that affect large chunks of chromosomes in people with clonal hematopoiesis
It’s a common occurrence in elderly people: Blood cells carrying mutated DNA explosively increase in number, resulting in genetic “mosaicism”: the presence of a population of cells that carries an altered genome. This phenomenon, known as clonal hematopoiesis, is associated with a substantially increased risk of blood cancer. However, most people with clonal hematopoiesis do not go on to develop blood cancers, and the causes and effects of clonal hematopoiesis are poorly understood.
A study by investigators from Brigham and Women’s Hospital, Harvard and the Broad Institute developed a new technique for detecting a type of clonal hematopoiesis known as mosaic chromosomal alterations, which involve mutations that affect large chunks of chromosomes. The team compiled an atlas of 8,342 mosaic chromosomal alterations, an order of magnitude larger than any previous study. Results are published this week in Nature.
“Our findings refine the link between mosaicism and blood cancer risk,” said Po-Ru Loh, PhD, of the Center for Data Sciences and the Division of Genetics at BWH. “While this work is still upstream of clinical translation, it improves our understanding of the biology of clonal hematopoiesis and suggests promising directions for future work.”
The team identified specific mosaic events that drive this increase in risk, observing that duplication of chromosome 12 conferred over a hundred-fold increased risk of chronic lymphocytic leukemia (CLL). However, blood cancers are rare diseases, so despite the large increases in risk, most people with mosaic events will not go on to develop blood cancers – making clinical application challenging. In addition, interventions still need to be developed to prevent high-risk individuals from getting blood cancer.
The team used highly sensitive computational techniques capable of detecting alterations that were present in only a small fraction (less than 1 percent) of blood cells, representing the very early stages of clonal expansion. The technique can be applied to data from genotyping arrays, a cheap and easily available technology for generating large amounts of data from very large sample sizes.
The researchers applied their technique to samples from approximately 150,000 participants in the UK Biobank.
“The large size of this data set allowed us to find many interesting patterns in the data,” said Loh. “The biggest surprise was that several subclasses of clonal expansions are actually strongly influenced by inherited genetic variants. That is, certain DNA mutations that are passed along from parents to children strongly increase the likelihood of clonal expansions later in one’s life.”
Funding for this work was provided by the National Institutes of Health (R01 HG006399, R01 GM105857, R01 MH101244, R21 HG009513, F32 HG007805, R01 HG006855, UM1 HG008900 and R01 HD081256) a Burroughs Wellcome Fund Career Award at the Scientific Interfaces, the Next Generation Fund at the Broad Institute of MIT and Harvard, the Stanley Center for Psychiatric Research, the Fannie and John Hertz Foundation, the US Department of Defense Breast Cancer Research Breakthrough Awards (W81XWH-16-1-0315, W81XWH-16-1-0316) the Elsa U. Pardee Foundation, NCI MSKCC Cancer Center Core Grant (P30 CA008748), and the Simons Foundation (SFARI Awards #346042 and #385027).
Paper cited: Loh, PR et al. “Insights into clonal haematopoiesis from 8,342 mosaic chromosomal alterations” Nature DOI: 10.1038/s41586-018-0321-x
Abnormal Branched-Chain Amino Acid Breakdown May Raise Diabetes Risk
In the U.S., about five out of 100 expectant mothers develop gestational diabetes mellitus (GDM), a temporary form of diabetes in which hormonal changes disrupt insulin function. Although GDM is often symptomless and subsides after delivery, women with a history of it face a seven-fold risk for developing type 2 diabetes.
The biological mechanisms underlying this rise in type 2 diabetes risk are mysterious. But a new study in Clinical Chemistry led by Deirdre Tobias, DSc., associate epidemiologist at Brigham and Women’s Hospital and Assistant Professor at Harvard Medical School, suggests that the irregular metabolism of branched-chain amino acids – components of proteins found in many foods – may be partially to blame for progression to type 2 diabetes.
Tobias and her team of researchers assessed reported diets and blood samples collected during the Nurses’ Health Study II, an investigation of chronic disease risk in women that was carried out from 1989 and continues today. They looked at the data from 347 women with histories of GDM, roughly half of whom later developed type 2 diabetes. The researchers calculated the women’s levels of branched-chain amino acid intake using published guidelines for nutrient content. Using mass spectrometry, they also measured the levels of branched-chain amino acids in the blood samples that were collected prior to type 2 diabetes development during the period of 1996-1999.
The researchers found that women with a history of GDM who later developed type 2 diabetes had higher levels of branched-chain amino acids in their blood, regardless of their dietary intake. That suggests that greater consumption of branched-chain amino acids may increase the risk for type 2 diabetes, but only if an individual’s ability to properly metabolize them is impaired.
“If your dietary intake is high, but you can clear these normally from circulation, then you don’t seem to be at a higher type 2 diabetes risk,” said Tobias.
Researchers cannot yet fully characterize the specific pathway of this impaired metabolism, but the abnormality seems to result in a buildup of circulating branched-chain amino acids, which have a detrimental downstream effect on insulin function.
Branched-chain amino acids are essential amino acids, meaning that they can only be obtained from food. They play important roles in immune and neurological function, and they exist in a wide variety of foods. Tobias emphasized that branched-chain amino acids are not necessarily unhealthy. More research is needed to determine whether lowering dietary intake of them can lower type 2 diabetes risk in people with abnormal metabolism.
“From a practical point of view, branched-chain amino acids are difficult to avoid,” said Tobias. “They are found in so many protein sources, both healthy and less healthy.”
Tobias and her team hope that early detection of abnormally high branched-chain amino acid blood concentrations may one day enable earlier interventions for those at risk for type 2 diabetes. They suggest it will take further research to determine if tests to detect these levels should become standard procedures during doctor’s appointments.
This study was funded by the National Institutes of Health.
Paper cited: Deirdre K. Tobias, Clary Clish, Samia Mora, Jun Li, Liming Liang, Frank B. Hu, JoAnn E. Manson, and Cuilin Zhang. “Dietary Intakes and Circulating Concentrations of Branched-Chain Amino Acids in Relation to Incident Type 2 Diabetes Risk Among High-Risk Women with a History of Gestational Diabetes Mellitus. Clinical Chemistry. In Press.
Accurate Measurements of Sodium Intake Confirm Relationship with Mortality
New study suggests recent paradoxical results may be due to imprecise evaluation
Eating foods high in salt is known to contribute to high blood pressure, but does that linear relationship extend to increased risk of cardiovascular disease and death? Recent cohort studies have contested that relationship, but a new study published in the International Journal of Epidemiology by investigators from Brigham and Women’s Hospital and their colleagues using multiple measurements confirms it. The study suggests that an inaccurate way of estimating sodium intake may help account for the paradoxical findings of others.
“Sodium is notoriously hard to measure,” said Nancy Cook, ScD, a biostatistician in the Department of Medicine at BWH. “Sodium is hidden – you often don’t know how much of it you’re eating, which makes it hard to estimate how much a person has consumed from a dietary questionnaire. Sodium excretions are the best measure, but there are many ways of collecting those. In our work, we used multiple measures to get a more accurate picture.”
Sodium intake can be measured using a spot test to determine how much salt has been excreted in a person’s urine sample. However, sodium levels in urine can fluctuate throughout the day so an accurate measure of a person’s sodium intake on a given day requires a full 24-hour sample. In addition, sodium consumption may change from day to day, meaning that the best way to get a full picture of sodium intake is to take samples on multiple days.
While previous studies have used spot samples and the Kawasaki formula, the team assessed sodium intake in multiple ways, including estimates based on that formula as well as ones based on the gold-standard method, which uses the average of multiple, non-consecutive urine samples. They assessed results for participants in the Trials of Hypertension Prevention, which included nearly 3,000 individuals with pre-hypertension.
The gold-standard method showed a direct linear relationship between increased sodium intake and increased risk of death. The team found that the Kawasaki formula suggested a J-shaped curve, which would imply that both low levels and high levels of sodium consumption were associated with increased mortality.
“Our findings indicate that inaccurate measurement of sodium intake could be an important contributor to the paradoxical J-shaped findings reported in some cohort studies. Epidemiological studies should not associate health outcomes with unreliable estimates of sodium intake,” the authors wrote.
Funding for this work was provided by the National Heart, Lung and Blood Institute (NHLBI) grant numbers HL37849, HL37852, HL37853, HL37854, HL37872, HL37884, HL37899, HL37904, HL37906, HL37907, HL37924, HL57915; and 14GRNT18440013 from the American Heart Association.
Paper cited: He, FJ et al. “Errors in estimating usual sodium intake by the Kawasaki formula alter its relationship with mortality: implications for public health” International Journal of Epidemiology DOI: 10.1093/ije/dyy114
Novel Molecular Target to Prevent Scarring of the Lung Blood Vessels Identified
Study identifies cancer protein as a target for treating fibrosis of the lung arteries with direct implications for patients with pulmonary arterial hypertension
Pulmonary arterial hypertension, a severe form of cardiopulmonary disease in which the arteries that transport blood from the heart to the lungs become thickened, constricted, and scarred, is a disease for which there is no cure. Investigators from Brigham and Women’s Hospital are unraveling the molecular mechanisms that may control PAH’s development and progression in an effort toward finding treatments that can halt the disease’s advancement. In a paper published this week in Science Translational Medicine, researchers share results from a study that identifies the cancer protein NEDD9 as a critical player in disease development, with potential therapeutic implications for patients with PAH.
“Our work identifies as a novel molecular target to prevent fibrosis in lung arteries, which can lead to early right-sided heart failure and death,” said corresponding author Bradley Maron, MD, a cardiologist and vascular biologist at BWH. “Our data provide an alternative mechanism that may account for the variability in fibrosis observed across subgroups of patients with PAH.”
In PAH, fibrosis is an important cause of damage to pulmonary arteries, which increases strain on the heart and leads to perpetual shortness of breath. In the past, researchers had theorized that one pathway acted as a “master switch” to globally control fibrosis but new evidence suggests that the development of fibrosis may be more complicated and more specific to different kinds of tissue. To better understand which genes and proteins may influence scarring specifically in the lung arteries, the Brigham research team used network medicine – a method of mapping relationships between proteins, pathways and more. Through this approach, the researchers discovered that the cancer protein NEDD9 is a critical mediator of vascular fibrosis in lung blood vessels.
They went on to identify a specific amino acid residue in NEDD9 that controls lung artery fibrosis. In patients with PAH, increased oxidant stress modifies this NEDD9 amino acid to cause lung artery fibrosis. The team also showed that the lung artery endothelium, previously regarded largely as a bystander in vascular fibrosis, contributes to this problem.
At the heart of the research team’s findings is NEDD9, which their data suggest mediates fibrotic vascular remodeling. The authors note that this has potential therapeutic relevance for PAH patients. While a therapy that targets this protein has not yet been developed, because of its role in cancer, several studies have put NEDD9 forward as an important therapeutic target for future drug discovery efforts.
Funding for this work was provided by the National Institutes of Health (NIH 1K08HL11207-01A1, NIH R56HL131787, NIH 1R01HL139613-01, NIH K08HL128802, NIH 1F32HL139019-01, NIH 5T32HL007633-32, NIH/NHLBI 1U01HL125215-01, R37 HL061795, HL108630, U54 HL119145, PPG HL048743, NHLBI F32HL131228, NIH/MIAMS K24 AR063120, R01 ARO70470, NIH 5R01-HL131910, NIH GM065204, NIH R01HL114839); American Heart Association (AHA 15GRNT25080016); Pulmonary Hypertension Association, CMREF, Klarman Foundation at Brigham and Women’s Hospital, and Systemic Sclerosis Foundation;
Paper cited: Samokhin, A et al. “NEDD9 targets COL3A1 to promote endothelial fibrosis and pulmonary arterial hypertension” Science Translational Medicine DOI: 10.1126/scitranslmed. aap7294
Double-Checking Diabetes Medications May Reduce Re-Hospitalizations
New study suggests that medication reconciliation programs can reduce risks
Clinicians may take upwards of 15 minutes to double-check a patient’s medication list in an electronic health record system, but according to a new study, this reconciliation process may be well worth the time for diabetes patients. In a paper to be published in the Diabetes Care journal, Brigham and Women’s Hospital physician Alexander Turchin, MD, MS, and his colleagues assessed medication reconciliation programs at BWH and Massachusetts General Hospital, and found that they seem to be working.
“Lists of medications often don’t match what the patient is actually taking,” said Turchin. “Data entry errors, as well as medications prescribed by other practitioners that we’re unaware of, can cause those discrepancies.” These discrepancies can lead to medication errors like omissions, duplications, improper doses and drug interactions that can sometimes have serious health consequences.
It’s not fully understood how common these discrepancies are. But two studies cited in the paper put the chance at 53.6 percent in 2005 – the same year that the Joint Commission first emphasized medication reconciliation as a national goal – and 41.3 percent in 2008. In one 2014 study cited, four out of five referral letters for 300 patients at a certain diabetes center each contained at least one medication discrepancy.
Diabetes patients are especially at risk for adverse reactions caused by improper dosages and pairings of medications. Incorrect dosing of medications like insulins and sulfonylureas can easily lead to low blood sugar – a dangerous complication that can result in seizures, loss of consciousness or even death.
To study whether medication reconciliation affected health outcomes for diabetes patients, Turchin and his team pulled patient records from January 2000 through June 2014. They examined the instances of medical reconciliation – when a clinician confirmed that a patient’s medications were correct – and the patient’s subsequent hospital visits in six-month periods. Patients typically took between one and two diabetes medications and visited primary care four times per assessment period. Turchin and his team found that clinicians reconciled diabetes medications in 67 percent of assessment periods, and that reconciliation of outpatient diabetes medications was associated with fewer subsequent hospitalizations and emergency room visits. They did not find the same correlation with reconciliation of non-diabetes medications the patients were on.
Extrapolating these findings, reconciling diabetes medications could save up to $6.7 billion annually – 8 percent of the total annual cost of hospitalizations of diabetes patients in the U.S. – and prevent rare but serious adverse reactions for patients.
“Our results suggest that reconciling diabetes medications could improve patient outcomes and decrease health care costs,” Turchin said.
This study was funded by the Patient-Centered Outcomes Research Institute.
Paper cited: Turchin A et al. “Ambulatory Medication Reconciliation and Frequency of Hospitalizations and Emergency Department Visits in Patients with Diabetes.” Diabetes Care. DOI: 10.2337/dc17-1260