The interplay between signalling pathways and metabolism is crucial for tissue growth. Yet, it remains poorly understood. Here, we studied the consequences of modulating iron metabolism on the growth ...of Drosophila imaginal discs. We find that reducing the levels of the ferritin heavy chain in the larval wing discs leads to drastic growth defects, whereas light chain depletion causes only minor defects. Mutant cell clones for the heavy chain lack the ability to compete against Minute mutant cells. Reactive oxygen species (ROS) accumulate in wing discs with reduced heavy chain levels, causing severe mitochondrial defects and ferroptosis. Preventing ROS accumulation alleviates some of the growth defects. We propose that the increased expression of ferritin in hippo mutant cells may protect against ROS accumulation.
Abstract
Neutrophils are an essential part of the innate immune system. To study their importance, experimental studies often aim to deplete these cells, generally by injecting anti-Ly6G or anti-Gr1 ...antibodies. However, these approaches are only partially effective, transient or lack specificity. Here we report that neutrophils remaining after anti-Ly6G treatment are newly derived from the bone marrow, instead of depletion escapees. Mechanistically, newly generated, circulating neutrophils have lower Ly6G membrane expression, and consequently reduced targets for anti-Ly6G-mediated depletion. To overcome this limitation, we develop a double antibody-based depletion strategy that enhances neutrophil elimination by anti-Ly6G treatment. This approach achieves specific, durable and controlled reduction of neutrophils in vivo, and may be suitable for studying neutrophil function in experimental models.
Glucose utilization increases in tumors, a metabolic process that is observed clinically by
F-fluorodeoxyglucose positron emission tomography (
F-FDG-PET). However, is increased glucose uptake ...important for tumor cells, and which transporters are implicated in vivo? In a genetically-engineered mouse model of lung adenocarcinoma, we show that the deletion of only one highly expressed glucose transporter, Glut1 or Glut3, in cancer cells does not impair tumor growth, whereas their combined loss diminishes tumor development.
F-FDG-PET analyses of tumors demonstrate that Glut1 and Glut3 loss decreases glucose uptake, which is mainly dependent on Glut1. Using
C-glucose tracing with correlated nanoscale secondary ion mass spectrometry (NanoSIMS) and electron microscopy, we also report the presence of lamellar body-like organelles in tumor cells accumulating glucose-derived biomass, depending partially on Glut1. Our results demonstrate the requirement for two glucose transporters in lung adenocarcinoma, the dual blockade of which could reach therapeutic responses not achieved by individual targeting.
Neutrophils are the most abundant circulating leucocytes and are essential for innate immunity. In cancer, pro- or antitumor properties have been attributed to tumor-associated neutrophils (TAN). ...Here, focusing on TAN accumulation within lung tumors, we identify GLUT1 as an essential glucose transporter for their tumor supportive behavior. Compared with normal neutrophils, GLUT1 and glucose metabolism increased in TANs from a mouse model of lung adenocarcinoma. To elucidate the impact of glucose uptake on TANs, we used a strategy with two recombinases, dissociating tumor initiation from neutrophil-specific
deletion. Loss of GLUT1 accelerated neutrophil turnover in tumors and reduced a subset of TANs expressing SiglecF. In the absence of GLUT1 expression by TANs, tumor growth was diminished and the efficacy of radiotherapy was augmented. Our results demonstrate the importance of GLUT1 in TANs, which may affect their pro- versus antitumor behavior. These results also suggest targeting metabolic vulnerabilities to favor antitumor neutrophils. SIGNIFICANCE: Lung tumor support and radiotherapy resistance depend on GLUT1-mediated glucose uptake in tumor-associated neutrophils, indicating that metabolic vulnerabilities should be considered to target both tumor cells as well as innate immune cells. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/9/2345/F1.large.jpg.
Hyperactivating mutations in Ras signaling are hallmarks of carcinomas. Ras signaling mediates cell fate decisions as well as proliferation during development. It is not known what dictates whether ...Ras signaling drives differentiation versus proliferation. Here we show that the Hippo pathway is critical for this decision. Loss of Hippo switches Ras activation from promoting cellular differentiation to aggressive cellular proliferation. Transcriptome analysis combined with genetic tests show that this excessive proliferation depends on the synergistic induction of Ras target genes. Using ChIP-nexus, we find that Hippo signaling keeps Ras targets in check by directly regulating the expression of two key downstream transcription factors of Ras signaling: the ETS-domain transcription factor Pointed and the repressor Capicua. Our results highlight how independent signaling pathways can impinge on each other at the level of transcription factors, thereby providing a safety mechanism to keep proliferation in check under normal developmental conditions.
•Hippo pathway determines Ras signaling output of differentiation or proliferation•Ras signaling mediates cell fate decisions as well as proliferation during development•Scallopped controls expression of Ras effectors Pointed and Capicua•Hippo signaling and Capicua repress a gene subset required for excessive proliferation
How is the cellular response to Ras activation—differentiation versus proliferation—determined? Pascual et al. show that the Hippo pathway helps decide by controlling expression of Ras effector genes, including the repressor Capicua. Capicua acts with Hippo signaling to repress and restrict the expression of a gene subset to prevent hyperproliferation.
Men have a critically important role to play in supporting women from different backgrounds to move into leadership roles. Indeed, it is necessary work for those in positions of privilege to ...challenge processes that result in inequitable gender outcomes in health leadership. We present the resources that have been compiled into a toolkit for men to support more inclusive health leadership and transformative systemic change. A three-step process was undertaken to search, select, and curate leading evidence-informed practices. Three key clusters of resources in the toolkit address why men’s actions are necessary, what leading actions entail, and the importance of mentorship and sponsorship. Change will require more than shaping the individual attitudes and behaviours of men in leadership positions. Attention to gender and other forms of inequity need to be embedded into the structures, processes and outcomes of teams, organizations, and systems and evaluated for process.
Elevated peripheral blood and tumor-infiltrating neutrophils are often associated with a poor patient prognosis. However, therapeutic strategies to target these cells are difficult to implement due ...to the life-threatening risk of neutropenia. In a genetically engineered mouse model of lung adenocarcinoma, tumor-associated neutrophils (TAN) demonstrate tumor-supportive capacities and have a prolonged lifespan compared to circulating neutrophils. Here, we show that tumor cell-derived GM-CSF triggers the expression of the anti-apoptotic Bcl-xL protein and enhances neutrophil survival through JAK/STAT signaling. Targeting Bcl-xL activity with a specific BH3 mimetic, A-1331852, blocked the induced neutrophil survival without impacting their normal lifespan. Specifically, oral administration with A-1331852 decreased TAN survival and abundance, and reduced tumor growth without causing neutropenia. We also show that G-CSF, a drug used to combat neutropenia in patients receiving chemotherapy, increased the proportion of young TANs and augmented the anti-tumor effect resulting from Bcl-xL blockade. Finally, our human tumor data indicate the same role for Bcl-xL on pro-tumoral neutrophil survival. These results altogether provide preclinical evidence for safe neutrophil targeting based on their aberrant intra-tumor longevity.
Synopsis
Tumor-associated neutrophils (TAN) survive extensively in the lung tumor microenvironment and increase expression of the anti-apoptotic protein Bcl-xL via GM-CSF-induced JAK/STAT signaling. Blockade of Bcl-xL decreases TAN ageing, reducing tumor growth in a mouse model of lung adenocarcinoma.
Expression of the anti-apoptotic Bcl-xL is higher in TANs than in neutrophils outside tumors, and continues to increase as they age.
Blockade of Bcl-xL selectively targets old, SiglecF-positive, tumor-supportive TANs, while preserving normal neutrophils and younger TANs.
In vivo inhibition of Bcl-xL delays tumor growth in a mouse model of lung adenocarcinoma.
Neutrophil depletion interferes with the anti-tumor efficacy of Bcl-xL blockade.
The use of the anti-neutropenic agent G-CSF potentiates the anti-tumor effect of Bcl-xL inhibition.
Tumor-associated neutrophils (TAN) survive extensively in the lung tumor microenvironment and increase expression of the anti-apoptotic protein Bcl-xL via GM-CSF-induced JAK/STAT signaling. Blockade of Bcl-xL decreases TAN ageing, reducing tumor growth in a mouse model of lung adenocarcinoma.
The deposition of amyloid-beta (Aβ) aggregates in the brain is a major pathological hallmark of Alzheimer's disease (AD). Aβ is generated from the cleavage of C-terminal fragments of the amyloid ...precursor protein (APP-CTFs) by γ-secretase, an intramembrane-cleaving protease with multiple substrates, including the Notch receptors. Endogenous modulation of γ-secretase is pointed to be implicated in the sporadic, age-dependent form of AD. Moreover, specifically modulating Aβ production has become a priority for the safe treatment of AD because the inhibition of γ-secretase results in adverse effects that are related to impaired Notch cleavage. Here, we report the identification of the adipocyte differentiation protein APMAP as a novel endogenous suppressor of Aβ generation. We found that APMAP interacts physically with γ-secretase and its substrate APP. In cells, the partial depletion of APMAP drastically increased the levels of APP-CTFs, as well as uniquely affecting their stability, with the consequence being increased secretion of Aβ. In wild-type and APP/ presenilin 1 transgenic mice, partial adeno-associated virus-mediated APMAP knockdown in the hippocampus increased Aβ production by ∼20 and ∼55%, respectively. Together, our data demonstrate that APMAP is a negative regulator of Aβ production through its interaction with APP and γ-secretase. All observed APMAP phenotypes can be explained by an impaired degradation of APP-CTFs, likely caused by an altered substrate transport capacity to the lysosomal/autophagic system.
Repetitive transcranial magnetic stimulation (rTMS) is widely used in both research and clinical settings to modulate human brain function and behavior through the engagement of the mechanisms of ...plasticity. Based upon experiments using single-pulse TMS as a probe, the physiologic mechanism of these effects is often assumed to be via changes in cortical excitability, with 10 Hz rTMS increasing and 1 Hz rTMS decreasing the excitability of the stimulated region. However, the reliability and reproducibility of these rTMS protocols on cortical excitability across and within individual subjects, particularly in comparison to robust sham stimulation, have not been systematically examined.
In a cohort of 28 subjects (39 ± 16 years), we report the first comprehensive study to (1) assess the neuromodulatory effects of traditional 1 Hz and 10 Hz rTMS on corticospinal excitability against both a robust sham control, and two other widely used patterned rTMS protocols (intermittent theta burst stimulation, iTBS; and continuous theta burst stimulation, cTBS), and (2) determine the reproducibility of all rTMS protocols across identical repeat sessions.
At the group level, neither 1 Hz nor 10 Hz rTMS significantly modulated corticospinal excitability. 1 Hz and 10 Hz rTMS were also not significantly different from sham and both TBS protocols. Reproducibility was poor for all rTMS protocols except for sham. Importantly, none of the real rTMS and TBS protocols demonstrated greater neuromodulatory effects or reproducibility after controlling for potential experimental factors including baseline corticospinal excitability, TMS coil deviation and the number of individual MEP trials.
These results call into question the effectiveness and reproducibility of widely used rTMS techniques for modulating corticospinal excitability, and suggest the need for a fundamental rethinking regarding the potential mechanisms by which rTMS affects brain function and behavior in humans.
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