Food for Growth: Distinct Nutrient Preferences between Primary Tumors and Metastases.

In this issue of Molecular Cell, Rinaldi et al. (2021) reveal how nutrient availability in the metastatic niche of breast cancer cells shapes their growth signaling, highlighting potential avenues for therapeutic interventions.

Estrogen-related receptors are targetable ROS sensors.

Excessive reactive oxygen species (ROS) can cause oxidative stress and consequently cell injury contributing to a wide range of diseases. Addressing the critical gaps in our understanding of the adaptive molecular events downstream ROS provocation holds promise for the identification of druggable metabolic vulnerabilities. Here, we unveil a direct molecular link between the activity of two estrogen-related receptor (ERR) isoforms and the control of glutamine utilization and glutathione antioxidant production. ERRα down-regulation restricts glutamine entry into the TCA cycle, while ERRγ up-regulation promotes glutamine-driven glutathione production. Notably, we identify increased ERRγ expression/activation as a hallmark of oxidative stress triggered by mitochondrial disruption or chemotherapy. Enhanced tumor antioxidant capacity is an underlying feature of human breast cancer (BCa) patients that respond poorly to treatment. We demonstrate that pharmacological inhibition of ERRγ with the selective inverse agonist GSK5182 increases antitumor efficacy of the chemotherapeutic paclitaxel on poor outcome BCa tumor organoids. Our findings thus underscore the ERRs as novel redox sensors and effectors of a ROS defense program and highlight the potential therapeutic advantage of exploiting ERRγ inhibitors for the treatment of BCa and other diseases where oxidative stress plays a central role.

Choline metabolism underpins macrophage IL-4 polarization and RELMα up-regulation in helminth infection.

Type 2 cytokines like IL-4 are hallmarks of helminth infection and activate macrophages to limit immunopathology and mediate helminth clearance. In addition to cytokines, nutrients and metabolites critically influence macrophage polarization. Choline is an essential nutrient known to support normal macrophage responses to lipopolysaccharide; however, its function in macrophages polarized by type 2 cytokines is unknown. Using murine IL-4-polarized macrophages, targeted lipidomics revealed significantly elevated levels of phosphatidylcholine, with select changes to other choline-containing lipid species. These changes were supported by the coordinated up-regulation of choline transport compared to naïve macrophages. Pharmacological inhibition of choline metabolism significantly suppressed several mitochondrial transcripts and dramatically inhibited select IL-4-responsive transcripts, most notably, Retnla. We further confirmed that blocking choline metabolism diminished IL-4-induced RELMα (encoded by Retnla) protein content and secretion and caused a dramatic reprogramming toward glycolytic metabolism. To better understand the physiological implications of these observations, naïve or mice infected with the intestinal helminth Heligmosomoides polygyrus were treated with the choline kinase α inhibitor, RSM-932A, to limit choline metabolism in vivo. Pharmacological inhibition of choline metabolism lowered RELMα expression across cell-types and tissues and led to the disappearance of peritoneal macrophages and B-1 lymphocytes and an influx of infiltrating monocytes. The impaired macrophage activation was associated with some loss in optimal immunity to H. polygyrus, with increased egg burden. Together, these data demonstrate that choline metabolism is required for macrophage RELMα induction, metabolic programming, and peritoneal immune homeostasis, which could have important implications in the context of other models of infection or cancer immunity.

mTOR Controls Mitochondrial Dynamics and Cell Survival via MTFP1.

The mechanisms that link environmental and intracellular stimuli to mitochondrial functions, including fission/fusion, ATP production, metabolite biogenesis, and apoptosis, are not well understood. Here, we demonstrate that the nutrient-sensing mechanistic/mammalian target of rapamycin complex 1 (mTORC1) stimulates translation of mitochondrial fission process 1 (MTFP1) to control mitochondrial fission and apoptosis. Expression of MTFP1 is coupled to pro-fission phosphorylation and mitochondrial recruitment of the fission GTPase dynamin-related protein 1 (DRP1). Potent active-site mTOR inhibitors engender mitochondrial hyperfusion due to the diminished translation of MTFP1, which is mediated by translation initiation factor 4E (eIF4E)-binding proteins (4E-BPs). Uncoupling MTFP1 levels from the mTORC1/4E-BP pathway upon mTOR inhibition blocks the hyperfusion response and leads to apoptosis by converting mTOR inhibitor action from cytostatic to cytotoxic. These data provide direct evidence for cell survival upon mTOR inhibition through mitochondrial hyperfusion employing MTFP1 as a critical effector of mTORC1 to govern cell fate decisions.

Total body irradiation: A transition from a Co-60 treatment unit to an IMRT lateral-field extended-SAD technique.

PURPOSE: The purpose of this work was to detail our center's experience in transitioning from a Co-60 treatment technique to an intensity modulated radiation therapy (IMRT) based lateral-field extended source-to-axis distance (e-SAD) technique for total body irradiation (TBI). MATERIALS AND METHODS: An existing beam model in RayStation v.10A was validated for the use of e-SAD TBI treatments. Data were acquired with an Elekta Synergy linear accelerator (LINAC) at an extended source-to-surface distance of 365 cm with an 18 MV beam. Beam model validation measurements included percentage depth dose (PDD), profile data, surface dose, build-up region and transmission measurements. End-to-end testing was carried out using an anthropomorphic phantom. Treatments were performed in a supine position in a whole-body Vac-Lok at an e-SAD of 400 cm with a beam spoiler 10 cm from the couch. Planning was achieved using IMRT, where multi-leaf collimators were used to modulate the beam and shield the organs at risk. Beam's eye view projection images were used for in-room patient positioning and in-vivo dosimetry was performed for every treatment. RESULTS: The percent difference between the measured and calculated PDD and profiles was less than 2% at all locations. Surface dose was 83.8% of the maximum dose with the beam spoiler at a 10 cm distance from the phantom. The largest percent difference between the treatment planning system (TPS) and measured data within the anthropomorphic phantom was approximately 2%. In-vivo dosimetry measurements yielded results within the 5% institutional threshold. CONCLUSION: In 2022, 17 patients were successfully treated using the new IMRT-based lateral-field e-SAD TBI technique. The resulting clinical plans respected the institutional standard. The commissioning process, as well as the treatment planning and delivery aspects were described in this work with the intention of supporting other clinics in implementing this treatment method.

Chronic AMPK activation via loss of FLCN induces functional beige adipose tissue through PGC-1α/ERRα.

The tumor suppressor folliculin (FLCN) forms a repressor complex with AMP-activated protein kinase (AMPK). Given that AMPK is a master regulator of cellular energy homeostasis, we generated an adipose-specific Flcn (Adipoq-FLCN) knockout mouse model to investigate the role of FLCN in energy metabolism. We show that loss of FLCN results in a complete metabolic reprogramming of adipose tissues, resulting in enhanced oxidative metabolism. Adipoq-FLCN knockout mice exhibit increased energy expenditure and are protected from high-fat diet (HFD)-induced obesity. Importantly, FLCN ablation leads to chronic hyperactivation of AMPK, which in turns induces and activates two key transcriptional regulators of cellular metabolism, proliferator-activated receptor γ (PPARγ) coactivator-1α (PGC-1α) and estrogen-related receptor α (ERRα). Together, the AMPK/PGC-1α/ERRα molecular axis positively modulates the expression of metabolic genes to promote mitochondrial biogenesis and activity. In addition, mitochondrial uncoupling proteins as well as other markers of brown fat are up-regulated in both white and brown FLCN-null adipose tissues, underlying the increased resistance of Adipoq-FLCN knockout mice to cold exposure. These findings identify a key role of FLCN as a negative regulator of mitochondrial function and identify a novel molecular pathway involved in the browning of white adipocytes and the activity of brown fat.

Household Food Insecurity and Changes in BMI Z-Score in a Pediatric Obesity Management Clinic.

BACKGROUND: Multicomponent lifestyle interventions are fundamental in pediatric obesity management. However, whether household food insecurity influences the efficacy of such interventions remains undocumented. OBJECTIVES: The objective was to compare changes in BMI z-score (BMIz) among children whose family received lifestyle counseling at a pediatric obesity management clinic in Montréal (Canada) according to their household food security status. METHODS: This is a retrospective, longitudinal analysis of medical records of children (2-17 y) with overweight or obesity who received lifestyle counseling at a pediatric obesity management clinic. The number of visits at the clinic and the duration of the follow-up were individualized. Household food security status was assessed using the Health Canada's Household Food Security Survey Module at the first visit at the clinic. BMIz was calculated and updated at each visit. A reduction of ≥0.25 in BMIz between the last and the first visit at the clinic was considered clinically meaningful. Statistical significance was considered at P < 0.05. RESULTS: Among the 214 children included in the study, 83 (38.8%) lived in a food insecure household. In multivariable-adjusted analyses, differences in BMIz between the last and the first appointment tended to be smaller among children who lived in a food insecure household than those in children living in a food secure household [ΔBMIzfood insecurity = -0.432 (95% CI: -0.672, -0.193) compared with ΔBMIzfood security = -0.556 (95% CI: -0.792, -0.319; P = 0.14)]. Differences were most notable in the first 6 mo of follow-up. The OR of achieving a clinically significant reduction in BMIz over follow-up associated with household food insecurity, compared with household food security, was 0.57 (95% CI: 0.31, 1.05; P = 0.07). CONCLUSIONS: In this sample of children followed up at a pediatric obesity clinic, those who lived in a food insecure household experienced smaller BMIz reductions than those who lived in a food secure household.

Food insecurity in households of children receiving care at a paediatric obesity management clinic in Montreal: Overall prevalence and changes associated with the COVID-19 pandemic.

Objectives: Food insecurity and paediatric obesity are two major public health issues in Canada that may have been exacerbated by the COVID-19 pandemic. We assessed food insecurity and its correlates among households of children receiving care at a paediatric obesity management clinic in Montreal. We also assessed whether the prevalence of food insecurity among households of children who received care during the COVID-19 pandemic differed from those who received care before it. Methods: This is a retrospective, cross-sectional analysis of medical records of children (2 to 17 years) who received care at a paediatric obesity management clinic in Montreal (Maison de santé prévention - Approche 180 [MSP-180]). Children's household food security status was assessed using Health Canada's Household Food Security Survey Module. Results: Among the 253 children included in the study, 102 (40.3%) lived in households with moderate (n=89; 35.2%) or severe food insecurity (n=13; 5.1%). Food insecurity was more prevalent in households of children who were first- or second-generation immigrants compared with those who were third generation or more (48.3% versus 30.1%; P=0.03). Prevalence of food insecurity among households of children who received care during the COVID-19 pandemic was 5.5% higher than among those who received care before the pandemic, but the difference was not statistically significant (39.6% versus 45.1%; P=0.65). Conclusions: Forty per cent of children treated at this paediatric obesity clinic lived in a food insecure household. This prevalence may have increased during the first year of the COVID-19 pandemic, but statistical power was insufficient to confirm it.

Cardiovascular Risk Reduction in High-Risk Pediatric Patients: A Scientific Statement From the American Heart Association.

This scientific statement presents considerations for clinical management regarding the assessment and risk reduction of select pediatric populations at high risk for premature cardiovascular disease, including acquired arteriosclerosis or atherosclerosis. For each topic, the evidence for accelerated acquired coronary artery disease and stroke in childhood and adolescence and the evidence for benefit of interventions in youth will be reviewed. Children and adolescents may be at higher risk for cardiovascular disease because of significant atherosclerotic or arteriosclerotic risk factors, high-risk conditions that promote atherosclerosis, or coronary artery or other cardiac or vascular abnormalities that make the individual more vulnerable to the adverse effects of traditional cardiovascular risk factors. Existing scientific statements and guidelines will be referenced when applicable, and suggestions for risk identification and reduction specific to each setting will be described. This statement is directed toward pediatric cardiologists, primary care providers, and subspecialists who provide clinical care for these young patients. The focus will be on management and justification for management, minimizing information on pathophysiology and epidemiology.

nanoCAGE reveals 5' UTR features that define specific modes of translation of functionally related MTOR-sensitive mRNAs.

The diversity of MTOR-regulated mRNA translation remains unresolved. Whereas ribosome-profiling suggested that MTOR almost exclusively stimulates translation of the TOP (terminal oligopyrimidine motif) and TOP-like mRNAs, polysome-profiling indicated that MTOR also modulates translation of mRNAs without the 5' TOP motif (non-TOP mRNAs). We demonstrate that in ribosome-profiling studies, detection of MTOR-dependent changes in non-TOP mRNA translation was obscured by low sensitivity and methodology biases. Transcription start site profiling using nano-cap analysis of gene expression (nanoCAGE) revealed that not only do many MTOR-sensitive mRNAs lack the 5' TOP motif but that 5' UTR features distinguish two functionally and translationally distinct subsets of MTOR-sensitive mRNAs: (1) mRNAs with short 5' UTRs enriched for mitochondrial functions, which require EIF4E but are less EIF4A1-sensitive; and (2) long 5' UTR mRNAs encoding proliferation- and survival-promoting proteins, which are both EIF4E- and EIF4A1-sensitive. Selective inhibition of translation of mRNAs harboring long 5' UTRs via EIF4A1 suppression leads to sustained expression of proteins involved in respiration but concomitant loss of those protecting mitochondrial structural integrity, resulting in apoptosis. Conversely, simultaneous suppression of translation of both long and short 5' UTR mRNAs by MTOR inhibitors results in metabolic dormancy and a predominantly cytostatic effect. Thus, 5' UTR features define different modes of MTOR-sensitive translation of functionally distinct subsets of mRNAs, which may explain the diverse impact of MTOR and EIF4A inhibitors on neoplastic cells.

Polo kinase regulates mitotic chromosome condensation by hyperactivation of condensin DNA supercoiling activity.

A defining feature of mitosis is the reorganization of chromosomes into highly condensed structures capable of withstanding separation and large-scale intracellular movements. This reorganization is promoted by condensin, an evolutionarily conserved multisubunit ATPase. Here we show, using budding yeast, that condensin is regulated by phosphorylation specifically in anaphase. This phosphorylation depends on several mitotic regulators, and the ultimate effector is the Polo kinase Cdc5. We demonstrate that Cdc5 directly phosphorylates all three regulatory subunits of the condensin complex in vivo and that this causes a hyperactivation of condensin DNA supercoiling activity. Strikingly, abrogation of condensin phosphorylation is incompatible with viability, and cells expressing condensin mutants that have a reduced ability to be phosphorylated in vivo are defective in anaphase-specific chromosome condensation. Our results reveal the existence of a regulatory mechanism essential for the promotion of genome integrity through the stimulation of chromosome condensation in late mitosis.

PGC1α and mitochondrial metabolism--emerging concepts and relevance in ageing and neurodegenerative disorders.

PGC1α is a transcriptional coactivator that is a central inducer of mitochondrial biogenesis in cells. Recent work highlighted that PGC1α can also modulate the composition and functions of individual mitochondria. Therefore, it is emerging that PGC1α is controlling global oxidative metabolism by performing two types of remodelling: (1) cellular remodelling through mitochondrial biogenesis, and (2) organelle remodelling through alteration in the intrinsic properties of mitochondria. The elevated oxidative metabolism associated with increased PGC1α activity could be accompanied by an increase in reactive oxygen species (ROS) that are primarily generated by mitochondria. However, increasing evidence suggests that this is not the case, as PGC1α is also a powerful regulator of ROS removal by increasing the expression of numerous ROS-detoxifying enzymes. Therefore, PGC1α, by controlling both the induction of mitochondrial metabolism and the removal of its ROS by-products, would elevate oxidative metabolism and minimize the impact of ROS on cell physiology. In this Commentary, we discuss how the biogenesis and remodelling of mitochondria that are elicited by PGC1α contribute to an increase in oxidative metabolism and the preservation of ROS homeostasis. Finally, we examine the importance of these findings in ageing and neurodegenerative disorders, conditions that are associated with impaired mitochondrial functions and ROS balance.

Stomatin-like protein 2 deficiency in T cells is associated with altered mitochondrial respiration and defective CD4+ T cell responses.

Stomatin-like protein 2 (SLP-2) is a mostly mitochondrial protein that regulates mitochondrial biogenesis and function and modulates T cell activation. To determine the mechanism of action of SLP-2, we generated T cell-specific SLP-2-deficient mice. These mice had normal numbers of thymocytes and T cells in the periphery. However, conventional SLP-2-deficient T cells had a posttranscriptional defect in IL-2 production in response to TCR ligation, and this translated into reduced CD4(+) T cell responses. SLP-2 deficiency was associated with impaired cardiolipin compartmentalization in mitochondrial membranes, decreased levels of the NADH dehydrogenase (ubiquinone) iron-sulfur protein 3, NADH dehydrogenase (ubiquinone) 1ß subcomplex subunit 8, and NADH dehydrogenase (ubiquinone) 1α subcomplex subunit 9 of respiratory complex I, and decreased activity of this complex as well as of complex II plus III of the respiratory chain. In addition, SLP-2-deficient T cells showed a significant increase in uncoupled mitochondrial respiration and a greater reliance on glycolysis. Based on these results, we propose that SLP-2 organizes the mitochondrial membrane compartmentalization of cardiolipin, which is required for optimal assembly and function of respiratory chain complexes. This function, in T cells, helps to ensure proper metabolic response during activation.

Attenuation of LDH-A expression uncovers a link between glycolysis, mitochondrial physiology, and tumor maintenance.

Alterations in cellular metabolism are among the most consistent hallmarks of cancer. Herein we have investigated the relationship between increased aerobic lactate production and mitochondrial physiology in tumor cells. To diminish the ability of malignant cells to metabolize pyruvate to lactate, lactate dehydrogenase A (LDH-A) levels were knocked down by means of LDH-A short hairpin RNAs. Reduction in LDH-A activity resulted in stimulation of mitochondrial respiration and decrease of mitochondrial membrane potential. It also compromised the ability of these tumor cells to proliferate under hypoxia. The tumorigenicity of the LDH-A-deficient cells was severely diminished, and this phenotype was reversed by complementation with the human ortholog LDH-A protein. These results demonstrate that LDH-A plays a key role in tumor maintenance.

Reduced exercise capacity for muscle mass in adolescents living with obesity.

BACKGROUND: Adolescents living with obesity (AlwO) can have limited exercise capacity. Exercise capacity can be predicted by a 2-factor model comprising lung function and leg muscle function, but no study has looked at cycling leg muscle function and its contribution to cycling exercise capacity in AlwO. METHODS: Twenty-two nonobese adolescents and 22 AlwO (BMI > 95 percentile) were studied. Anthropometry, body composition (dual-energy X-ray absorptiometry), spirometry, 30-s isokinetic work capacity, and maximal exercise (cycle ergometry) were measured. RESULTS: AlwO had greater total body mass, lean body mass, and lean leg mass (LLM). Lung function trended higher in AlwO. Leg 30-s work did not differ in absolute terms or per allometrically scaled LLM. Peak oxygen consumption did not differ between the groups in absolute terms or as percent predicted values (79.59 ± 14.6 vs. 82.3 ± 11.2% predicted control versus ALwO) but was lower in AlwO when expressed per kg body mass, kg lean body mass, scaled lean body mass, and LLM. Peak oxygen consumption related to both lung function and 30-s work, with no observed group effect. 30-s leg work related to the scaled LLM, with a small group effect. There was some correlation between leg work and time spent in moderate to vigorous physical activity in AlwO (rs = 0.39, p = .07). CONCLUSION: AlwO have larger LLM and preserved exercise capacity, when expressed as percentage of predicted, but not per allometrically scaled LLM. Increasing time spent in moderate to vigorous activity may benefit AlwO.

Evolocumab in paediatric heterozygous familial hypercholesterolaemia: cognitive function during 80 weeks of open-label extension treatment.

AIMS: PCSK9 inhibition intensively lowers low density lipoprotein cholesterol and is well tolerated in adults and paediatric patients with familial hypercholesterolaemia (FH). HAUSER-RCT showed that 24 weeks of treatment with evolocumab in paediatric patients did not affect cognitive function. This study determined the effects of 80 additional weeks of evolocumab treatment on cognitive function in paediatric patients with heterozygous FH. METHODS AND RESULTS: HAUSER-OLE was an 80-week open-label extension of HAUSER-RCT, a randomized, double-blind, 24-week trial evaluating the efficacy and safety of evolocumab in paediatric patients (ages 10-17 years) with FH. During the OLE, all patients received monthly 420 mg subcutaneous evolocumab injections. Tests of psychomotor function, attention, visual learning, and executive function were administered at baseline and Weeks 24 and 80 of the OLE. Changes over time were analysed descriptively and using analysis of covariance. Cohen's d statistic was used to evaluate the magnitude of treatment effects. Analysis of covariance results indicated no decrease in performance across visits during 80 weeks of evolocumab treatment for Groton Maze Learning, One Card Learning accuracy, Identification speed, or Detection speed (all P > 0.05). Performance on all tasks was similar for those who received placebo or evolocumab in the RCT (all P > 0.05). For all tests, the least square mean differences between patients who received placebo vs. evolocumab in the parent study were trivial (all Cohen's d magnitude < 0.2). CONCLUSION: In paediatric patients with FH, 80 weeks of open-label evolocumab treatment had no negative impact on cognitive function. REGISTRATION: ClinicalTrials.gov identifier: NCT02624869.

Some children are born with a genetic disorder that causes high cholesterol, which leads to heart disease. Children with high cholesterol can be treated with evolocumab, a medication that lowers blood cholesterol. Because cholesterol is important for development and adequate function of the brain, there is a concern that lowering cholesterol in children may affect mental ability. In this study, we tested whether treating children with evolocumab for 80 weeks affected mental ability in performing several tasks. A battery of tests that measure executive function (Groton Maze Learning Test), visual learning (One Card Learning Test), visual attention (Identification Test), and psychomotor function (Detection Test) showed no decrease in performance across visits during 80 weeks of evolocumab treatment. Performance on all tasks was similar for the children who received placebo for the first 24 weeks then received evolocumab for an additional 80 weeks (placebo/evolocumab) and those who received evolocumab for 24 weeks then received evolocumab for an additional 80 weeks (evolocumab/evolocumab).

p66ShcA promotes malignant breast cancer phenotypes by alleviating energetic and oxidative stress.

Significant efforts have focused on identifying targetable genetic drivers that support the growth of solid tumors and/or increase metastatic ability. During tumor development and progression to metastatic disease, physiological and pharmacological selective pressures influence parallel adaptive strategies within cancer cell sub-populations. Such adaptations allow cancer cells to withstand these stressful microenvironments. This Darwinian model of stress adaptation often prevents durable clinical responses and influences the emergence of aggressive cancers with increased metastatic fitness. However, the mechanisms contributing to such adaptive stress responses are poorly understood. We now demonstrate that the p66ShcA redox protein, itself a ROS inducer, is essential for survival in response to physiological stressors, including anchorage independence and nutrient deprivation, in the context of poor outcome breast cancers. Mechanistically, we show that p66ShcA promotes both glucose and glutamine metabolic reprogramming in breast cancer cells, to increase their capacity to engage catabolic metabolism and support glutathione synthesis. In doing so, chronic p66ShcA exposure contributes to adaptive stress responses, providing breast cancer cells with sufficient ATP and redox balance needed to withstand such transient stressed states. Our studies demonstrate that p66ShcA functionally contributes to the maintenance of aggressive phenotypes and the emergence of metastatic disease by forcing breast tumors to adapt to chronic and moderately elevated levels of oxidative stress.

AMPK-mediated regulation of endogenous cholesterol synthesis does not affect atherosclerosis in a murine Pcsk9-AAV model.

BACKGROUND AND AIMS: Dysregulated cholesterol metabolism is a hallmark of atherosclerotic cardiovascular diseases, yet our understanding of how endogenous cholesterol synthesis affects atherosclerosis is not clear. The energy sensor AMP-activated protein kinase (AMPK) phosphorylates and inhibits the rate-limiting enzyme in the mevalonate pathway HMG-CoA reductase (HMGCR). Recent work demonstrated that when AMPK-HMGCR signaling was compromised in an Apoe-/- model of hypercholesterolemia, atherosclerosis was exacerbated due to elevated hematopoietic stem and progenitor cell mobilization and myelopoiesis. We sought to validate the significance of the AMPK-HMGCR signaling axis in atherosclerosis using a non-germline hypercholesterolemia model with functional ApoE. METHODS: Male and female HMGCR S871A knock-in (KI) mice and wild-type (WT) littermate controls were made atherosclerotic by intravenous injection of a gain-of-function Pcsk9D374Y-adeno-associated virus followed by high-fat and high-cholesterol atherogenic western diet feeding for 16 weeks. RESULTS: AMPK activation suppressed endogenous cholesterol synthesis in primary bone marrow-derived macrophages from WT but not HMGCR KI mice, without changing other parameters of cholesterol regulation. Atherosclerotic plaque area was unchanged between WT and HMGCR KI mice, independent of sex. Correspondingly, there were no phenotypic differences observed in hematopoietic progenitors or differentiated immune cells in the bone marrow, blood, or spleen, and no significant changes in systemic markers of inflammation. When lethally irradiated female mice were transplanted with KI bone marrow, there was similar plaque content relative to WT. CONCLUSIONS: Given previous work, our study demonstrates the importance of preclinical atherosclerosis model comparison and brings into question the importance of AMPK-mediated control of cholesterol synthesis in atherosclerosis.

Spatiotemporal modeling of chemoresistance evolution in breast tumors uncovers dependencies on SLC38A7 and SLC46A1.

In solid tumors, drug concentrations decrease with distance from blood vessels. However, cellular adaptations accompanying the gradated exposure of cancer cells to drugs are largely unknown. Here, we modeled the spatiotemporal changes promoting chemotherapy resistance in breast cancer. Using pairwise cell competition assays at each step during the acquisition of chemoresistance, we reveal an important priming phase that renders cancer cells previously exposed to sublethal drug concentrations refractory to dose escalation. Therapy-resistant cells throughout the concentration gradient display higher expression of the solute carriers SLC38A7 and SLC46A1 and elevated intracellular concentrations of their associated metabolites. Reduced levels of SLC38A7 and SLC46A1 diminish the proliferative potential of cancer cells, and elevated expression of these SLCs in breast tumors from patients correlates with reduced survival. Our work provides mechanistic evidence to support dose-intensive treatment modalities for patients with solid tumors and reveals two members of the SLC family as potential actionable targets.

PGC-1s shape epidermal physiology by modulating keratinocyte proliferation and terminal differentiation.

Skin plays central roles in systemic physiology, and it undergoes significant functional changes during aging. Members of the peroxisome proliferator-activated receptor-gamma coactivator (PGC-1) family (PGC-1s) are key regulators of the biology of numerous tissues, yet we know very little about their impact on skin functions. Global gene expression profiling and gene silencing in keratinocytes uncovered that PGC-1s control the expression of metabolic genes as well as that of terminal differentiation programs. Glutamine emerged as a key substrate promoting mitochondrial respiration, keratinocyte proliferation, and the expression of PGC-1s and terminal differentiation programs. Importantly, gene silencing of PGC-1s reduced the thickness of a reconstructed living human epidermal equivalent. Exposure of keratinocytes to a salicylic acid derivative potentiated the expression of PGC-1s and terminal differentiation genes and increased mitochondrial respiration. Overall, our results show that the PGC-1s are essential effectors of epidermal physiology, revealing an axis that could be targeted in skin conditions and aging.