Bidirectional transport of amino acids regulates mTOR and autophagy

Long-term leucine supplementation increases body weight in goats by controlling appetite and muscle protein synthesis under protein-restricted conditions

An inadequate amino acid (AA) supply in animals under protein-restricted conditions can slow skeletal muscle growth. Protein translation can be activated by short-term leucine (Leu) stimulation; however, whether muscle mass increases under long-term Leu supplementation and how the gut and muscle respond to Leu supplementation are largely unknown. In this study, we investigated if muscle mass increases with long-term Leu supplementation under protein-restricted conditions. We identified changes in the link between the gut and muscles under different amino acid supply conditions, using goats as the study object. A total of 27 Xiangdong black male goats with average initial body weight (BW) of 10.88 ± 1.22 kg were randomly divided into three dietary treatments: a normal protein diet (NP, 14.24% crude protein [CP]); a low protein diet (LP, 8.27% CP with supplemental 1.66% rumen-protected lysine [RPLys] and 0.09% rumen-protected methionine [RPMet]); and LP diet with rumen-protected Leu (RPLeu) (LP + RPLeu, 8.75% CP with supplemental 1.66% RPLys, 0.09% RPMet and 1.46% RPLeu). The animal trial lasted for 110 d, consisting of 20 d of adaptation and a 90 d of experimental period. The results showed that long-term protein restriction increased gut tryptophan hydroxylase 1 (TPH1) activity (P < 0.001), tryptophan (Trp) catabolism (P < 0.001), and 5-hydroxytryptamine (5-HT) synthesis (P < 0.001), which all subsequently reduced goat appetite. Long-term Leu supplementation inhibited 5-HT synthesis (P < 0.001), decreased Trp catabolism in the gut, and increased appetite in goats. Long-term protein restriction enhanced jejunal and ileal branched-chain amino acid transferase (BCAT) (P < 0.001) and branched-chain α-Keto acid dehydrogenase (BCKD) (P = 0.048) activities, which increased branched-chain amino acid (BCAA) catabolism. Immunofluorescence results showed that protein restriction decreased the intestinal mucosal expression of solute carrier family 1 member 5 (SLC1A5) (P = 0.032) and solute carrier family 7 member 5 (SLC7A5) (P < 0.001), reduced BCAA transport from the mucosa to the blood, lowered BCAA levels in the blood (P < 0.001). Western blot results showed that protein restriction inhibited mammalian target of rapamycin (mTOR) pathway activation in goat muscles. Leu supplementation increased BCAA translocation from the intestine to the blood and promoted activation of the muscle mTOR pathway and protein synthesis. In conclusion, our results suggest that Leu supplementation in low-protein diets improves appetite and alleviates the inhibition of muscle protein synthesis in goats.

Energy metabolism in health and diseases

Energy metabolism is indispensable for sustaining physiological functions in living organisms and assumes a pivotal role across physiological and pathological conditions. This review provides an extensive overview of advancements in energy metabolism research, elucidating critical pathways such as glycolysis, oxidative phosphorylation, fatty acid metabolism, and amino acid metabolism, along with their intricate regulatory mechanisms. The homeostatic balance of these processes is crucial; however, in pathological states such as neurodegenerative diseases, autoimmune disorders, and cancer, extensive metabolic reprogramming occurs, resulting in impaired glucose metabolism and mitochondrial dysfunction, which accelerate disease progression. Recent investigations into key regulatory pathways, including mechanistic target of rapamycin, sirtuins, and adenosine monophosphate-activated protein kinase, have considerably deepened our understanding of metabolic dysregulation and opened new avenues for therapeutic innovation. Emerging technologies, such as fluorescent probes, nano-biomaterials, and metabolomic analyses, promise substantial improvements in diagnostic precision. This review critically examines recent advancements and ongoing challenges in metabolism research, emphasizing its potential for precision diagnostics and personalized therapeutic interventions. Future studies should prioritize unraveling the regulatory mechanisms of energy metabolism and the dynamics of intercellular energy interactions. Integrating cutting-edge gene-editing technologies and multi-omics approaches, the development of multi-target pharmaceuticals in synergy with existing therapies such as immunotherapy and dietary interventions could enhance therapeutic efficacy. Personalized metabolic analysis is indispensable for crafting tailored treatment protocols, ultimately providing more accurate medical solutions for patients. This review aims to deepen the understanding and improve the application of energy metabolism to drive innovative diagnostic and therapeutic strategies.

dilp2-Mediated Insulin Signaling Pathway Was Involved in O3-Induced Multigenerational Effects of Shortened Lifespan in Drosophila melanogasters

As a long-standing atmospheric pollutant, ozone (O3) exerts enduring effects on biological health. However, experimental research on its impact on organism lifespan and generational effects is limited. This study exposed three generations of fruit flies (Drosophila melanogaster) to O3, revealing a shortened lifespan across generations. Specifically, after O3 exposure, the lifespan of the F2 generation was significantly reduced compared with F0 and F1 generations, indicating a cumulative multigenerational effect. Transcriptome analysis unveiled significant disruptions in metabolic pathways, notably the insulin signaling pathway. Subsequent qRT-PCR analysis showed elevated mRNA levels of insulin pathway-related genes (dilp2, dilp3, dilp5, InR, and TOR), alongside decreased expression levels of FOXO, 4E-BP, and Atg5 in flies exposed to O3. Notably, knocking down dilp2, rather than dilp3, dilp5, and InR, rescued the O3-induced lifespan shortening. Overall, O3 exposure triggered activation of the dilp2-mediated InR-FOXO/TOR-4E-BP-Atg5 signaling pathway, potentially contributing to shortened lifespan with cumulative effects. This study highlights the viability of employing fruit flies as a model to evaluate the multigenerational toxicity of environmental pollutants, particularly atmospheric pollutants.

Serine starvation suppresses the progression of esophageal cancer by regulating the synthesis of purine nucleotides and NADPH

Serine metabolism provides important metabolic intermediates that support the rapid proliferation of tumor cells. However, the role of serine metabolism in esophageal squamous cell carcinoma (ESCC) and the underlying mechanism remains unclear. Here, we show that serine starvation predominantly inhibits ESCC cell proliferation by suppressing purine nucleotides and NADPH synthesis. Mechanistically, serine depletion led to the accumulation of aminoimidazole carboxamide ribonucleoside (AICAR), an intermediate metabolite of de novo purine synthesis, and AMP/ATP ratio. These increases activated 5'-AMP-activated kinase (AMPK), which subsequently inhibited the mTORC1 pathway by phosphorylating Raptor at Ser792. Moreover, serine depletion decreased NADPH level followed by elevated reactive oxygen species (ROS) production and DNA damage, which induced p53-p21 mediated G1 phase cell cycle arrest. Conversely, serine starvation activated transcription factor 4 (ATF4)-mediated robust expression of phosphoserine aminotransferase 1 (PSAT1) which in turn promoted compensatory endogenous serine synthesis, thus maintaining ESCC cell survival under serine-limited conditions. Accordingly, serine deprivation combined with PSAT1 inhibition significantly suppressed ESCC tumor growth both in vitro and in vivo. Taken together, our findings demonstrate that serine starvation suppresses the proliferation of ESCC cells by disturbing the synthesis of purine nucleotides and NADPH, and the combination of serine deprivation and PSAT1 inhibition significantly impairs ESCC tumor growth. Our study provides a theoretical basis for targeting serine metabolism as a potential therapeutic strategy for ESCC.

ATF3-SLC7A7 Axis Regulates mTORC1 Signaling to Suppress Lipogenesis and Tumorigenesis in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) poses a substantial global health burden, with poor prognosis and high mortality rates. Dysregulated lipid metabolism has emerged as a critical driver of HCC progression. While mTORC1 signaling is known to promote lipid synthesis in HCC, the regulatory mechanisms governing mTORC1 remain largely unclear. Here, we demonstrate that mTORC1 inhibition significantly reduces lipogenesis in HCC and uncover a regulatory axis involving the transcription factor ATF3 and the leucine-arginine transporter SLC7A7. Transcriptomic analysis of HCC patients reveals an inverse correlation between ATF3 expression and lipid synthesis, a finding corroborated by experimental validation. Mechanistically, ATF3 suppresses mTORC1 signaling, thereby inhibiting lipid biosynthesis, with SLC7A7 identified as a key intermediary in this process. Specifically, ATF3 binds to the enhancer region of SLC7A7, driving its transcriptional activation and subsequently restraining mTORC1 activity. Functional assays in ATF3-overexpressing and -knockdown HCC cell lines further confirm ATF3's role as a tumor suppressor. Our study identifies a novel ATF3-SLC7A7-mTORC1 regulatory axis that attenuates lipogenesis and tumorigenesis in HCC, establishing a critical link between lipid metabolism and hepatocarcinogenesis. These findings offer new insights into potential therapeutic targets for the treatment of HCC.

Effects of microplastics on chemo-resistance and tumorigenesis of colorectal cancer

Microplastics (MPs) are widely distributed environmental pollutants around the world. Although studies have demonstrated that MPs have adverse effects on human health, the relationship between MPs and tumors remains unclear. The gut is the main site of microplastics absorption, and the function of MPs in the chemoresistance and progression of colorectal cancer (CRC) needs more investigation. Here, we show that MPs exist in human CRC tissues for the first time by using a laser direct infrared chemical imaging system. MPs can cause an increase in CRC incidence in animal models and promote resistance to oxaliplatin. It is illustrated that the uptake of MPs enhances levels of autophagy by activating the mTOR pathway. MPs can also promote the disorder of intestinal flora and intestinal inflammation, serving as an essential component in the onset and advancement of CRC. These results indicated that microplastic pollutants in colorectal cancer could mediate protective autophagy through the mTOR/ULK1 axis, which is one of the new reasons for chemo-resistance in CRC under the background of increasingly serious microplastics pollution. This study identified the adverse effects of MPs on colorectal cancer progression and chemotherapy prognosis, and attempted to block the intake of MPs to propose a novel approach for clinical precision treatment.

The promise of mitochondria in the treatment of glioblastoma: a brief review

Glioblastoma (GBM) is a prevalent and refractory type of brain tumor. Over the past two decades, there have been minimal advancements in GBM therapy. The current standard treatment involves surgical excision followed by radiation and chemotherapy. Compared to other tumors, GBM is more challenging to treat due to the presence of glioma stem-like cells (GSCs) and the blood-brain barrier, resulting in an extremely low survival rate. Mitochondria play a critical role in tumor respiration, metabolism, and multiple signaling pathways involved in tumor formation, progression, and cell apoptosis. Consequently, mitochondria represent promising targets for developing novel anticancer agents, including those targeting oxidative phosphorylation, reactive oxygen species (ROS), mitochondrial transfer, and mitophagy. This review outlines the mitochondrial-related therapeutic targets in GBM, highlighting the potential of mitochondria as a target for GBM treatment.

Targeting glutamine metabolism crosstalk with tumor immune response

Glutamine, akin to glucose, is a fundamental nutrient for human physiology. Tumor progression is often accompanied by elevated glutamine consumption, resulting in a disrupted nutritional balance and metabolic reprogramming within the tumor microenvironment. Furthermore, immune cells, which depend on glutamine for metabolic support, may experience functional impairments and dysregulation. Although the role of glutamine in tumors has been extensively studied, the specific impact of glutamine competition on immune responses, as well as the precise cellular alterations within immune cells, remains incompletely understood. In this review, we summarize the consequences of glutamine deprivation induced by tumor-driven glutamine uptake on immune cells, assessing the underlying mechanisms from the perspective of various components of the immune microenvironment. Additionally, we discuss the potential synergistic effects of glutamine supplementation and immunotherapy, offering insights into future research directions. This review provides compelling evidence for the integration of glutamine metabolism and immunotherapy as a promising strategy in cancer therapy.

A Novel DNA Repair-Gene Model to Predict Responses to Immunotherapy and Prognosis in Patients With EGFR-Mutant Non-Small Cell Lung Cancer

BACKGROUND

The epidermal growth factor receptor mutant (EGFRm) non-small cell lung cancer (NSCLC) has a unique "cold" immune profile. DNA damage repair (DDR) genes are closely related to tumorigenesis and the effectiveness of immunotherapy in many tumors. However, the role and mechanism of DDR in the genesis and progression of EGFRm NSCLC remain unclear.

METHODS

This study included 101 EGFRm NSCLC samples from The Cancer Genome Atlas (TCGA) dataset and a GSE31210 dataset (external set) from the GEO database. Cluster analysis was used to identify different subtypes of EGFRm NSCLC based on the expression of DDR genes. Univariate and LASSO regression analysis was used to develop a DDR-based predictive model. The prognostic significance of this model was assessed using Cox regression, Kaplan-Meier, and receiver operating characteristic (ROC) curve analyses. Bioinformatics analysis was performed to investigate the clinicopathological characteristics and immune profiles associated with this model. In vitro experiment was performed to testify the role of DDR genes in EGFRm NSCLC.

RESULTS

We identified two subtypes of EGFRm NSCLC: DDR-activated and DDR-suppressed. The DDR-activated subtype showed more aggressive clinical behavior and poorer prognosis and was more responsive to immunotherapy. A prognostic model for EGFRm NSCLC was constructed using four DDR genes: CAPS, FAM83A, IGLV8-61, and SLC7A5. The derived risk score could serve as an independent prognostic indicator. High- and low-risk patients exhibited distinct clinicopathological characteristics, immune profiles, and responses to immunotherapy. The T-cell inflammation and Tumor Immune Dysfunction and Exclusion (TIDE) scores differed between the high- and low-risk subgroups, with both showing enhanced effectiveness of immunotherapy in the low-risk subgroup. Targeted therapy such as BI.2536, an inhibitor of polo-like kinase 1, could be effective for patients with high-risk EGFRm NSCLC. Meanwhile, in vitro detection approved the role of DDR genes in EGFRm NSCLC response.

CONCLUSION

This study demonstrated a diversity of DDR genes in EGFRm NSCLC and developed a predictive model using these genes. This model could assist in identifying potential candidates for immunotherapy and in assessing personalized treatment and prognosis of patients with EGFRm NSCLC.

GlutaR: A High-Performance Fluorescent Protein-Based Sensor for Spatiotemporal Monitoring of Glutamine Dynamics In Vivo

Glutamine is the most abundant amino acid in human blood and muscle, and is integral to a wide variety of functions in cancer cells. However, the inability to monitor the subcellular distribution of glutamine in real-time has obscured understanding of glutamine metabolism under physiological and pathological conditions. Here, we report the development of a genetically encoded fluorescent sensor and demonstrate how this GlnBP-cpYFP fusion "GlutaR sensor" undergoes glutamine-induced conformational changes reflected in detectable fluorescence responses. Obtained after iterative screening of approximately 1,600 variants, GlutaR exhibits a ratiometric readout, fast response kinetics, and high responsivity (R488/405 of ~1000 %), and we demonstrate its selectivity for monitoring glutamine fluctuations in multiple cell types. Additionally, using digitonin permeabilization of GlutaR HeLa cells, we generated a calibration curve and performed in situ titration to quantify free glutamine concentrations in subcellular compartments (cytosol, nucleus, mitochondria). Subsequently, we applied GlutaR to investigate how chemical and genetic inhibition of glutamine synthetase (GS) and glutaminase (GLS) differentially alter glutamine levels in subcellular compartments. Finally, we demonstrate GlutaR's ability to monitor dynamic glutamine levels in muscle and liver tissues of diabetic mice in vivo. These findings collectively demonstrate GlutaR as a versatile tool for the spatiotemporal characterization of glutamine metabolism in living cells and tissues.

Glutamine metabolism is systemically different between primary and induced pluripotent stem cell-derived brain microvascular endothelial cells

Human primary (hpBMEC) and induced pluripotent stem cell (iPSC)-derived brain microvascular endothelial-like cells (hiBMEC) are interchangeably used in blood-brain barrier models to study neurological diseases and drug delivery. Both hpBMEC and hiBMEC use glutamine as a source of carbon and nitrogen to produce metabolites and build proteins essential to cell function and communication. We used metabolomic, transcriptomic, and computational methods to examine how hpBMEC and hiBMEC metabolize glutamine, which may impact their utility in modeling the blood-brain barrier. We found that glutamine metabolism was systemically different between the two cell types. hpBMEC had a higher metabolic rate and produced more glutamate and GABA, while hiBMEC rerouted glutamine to produce more glutathione, fatty acids, and asparagine. Higher glutathione production in hiBMEC correlated with higher oxidative stress compared to hpBMEC. α-ketoglutarate (α-KG) supplementation increased glutamate secretion from hiBMEC to match that of hpBMEC; however, α-KG also decreased hiBMEC glycolytic rate. These fundamental metabolic differences between BMEC types may impact in vitro blood-brain barrier model function, particularly communication between BMEC and surrounding cells, and emphasize the importance of evaluating the metabolic impacts of iPSC-derived cells in disease models.

Metabolic Signaling in the Tumor Microenvironment

Cancer cells must reprogram their metabolism to sustain rapid growth. This is accomplished in part by switching to aerobic glycolysis, uncoupling glucose from mitochondrial metabolism, and performing anaplerosis via alternative carbon sources to replenish intermediates of the tricarboxylic acid (TCA) cycle and sustain oxidative phosphorylation (OXPHOS). While this metabolic program produces adequate biosynthetic intermediates, reducing agents, ATP, and epigenetic remodeling cofactors necessary to sustain growth, it also produces large amounts of byproducts that can generate a hostile tumor microenvironment (TME) characterized by low pH, redox stress, and poor oxygenation. In recent years, the focus of cancer metabolic research has shifted from the regulation and utilization of cancer cell-intrinsic pathways to studying how the metabolic landscape of the tumor affects the anti-tumor immune response. Recent discoveries point to the role that secreted metabolites within the TME play in crosstalk between tumor cell types to promote tumorigenesis and hinder the anti-tumor immune response. In this review, we will explore how crosstalk between metabolites of cancer cells, immune cells, and stromal cells drives tumorigenesis and what effects the competition for resources and metabolic crosstalk has on immune cell function.

A Review on the Role of Human Solute Carriers Transporters in Cancer

Background and Aim

The high rate of tumor growth results in an increased need for amino acids. As solute carriers (SLC) transporters are capable of transporting different amino acids, cancer may develop as a result of these transporters' over-expression due to their complex formation with other biological molecules. Therefore, this review investigated the role of SLC transporters in the progression of cancer.

Methods

We retrieved data from Google Scholar, Web of Science, PubMed, Cochrane Library, and EMBASE regarding the influence of human SLCs on the development of cancer. Articles published in English before August 2024 were included in the study.

Results

The overexpression of SLCs is strongly related to tumor cell proliferation and angiogenesis in a number of cancer types including thyroid, pancreatic, lung, hepatocellular, and colon cancers. They are crucial for the stimulation of several biological signaling pathways, particularly mTOR kinase activity, which starts a signaling cascade, protein synthesis, cell growth, and proliferation, and inhibits apoptosis of cancerous cells. Furthermore, they contribute to the activation of PI3K/AKT signaling, which has an impact on the growth, invasion, and death of cancer cells. Thus, SLC transporters become a potential therapeutic target that plays a crucial role in drug resistance, tumor microenvironment regulation, and modulation of immune response.

Conclusion

The review recognized the crucial role of SLC transporters in different types of cancer progression. Therefore, to confirm our findings, a case-control study is required to investigate the role of amino acid transporters in cancer development.

Transmembrane Amino Acid Transporters in Shaping the Metabolic Profile of Breast Cancer Cell Lines: The Focus on Molecular Biological Subtype

Amino acid metabolism in breast cancer cells is unique for each molecular biological subtype of breast cancer. In this review, the features of breast cancer cell metabolism are considered in terms of changes in the amino acid composition due to the activity of transmembrane amino acid transporters. In addition to the main signaling pathway PI3K/Akt/mTOR, the activity of the oncogene c-Myc, HIF, p53, GATA2, NF-kB and MAT2A have a direct effect on the amino acid metabolism of cancer cells, their growth and proliferation, as well as the maintenance of homeostatic equilibrium. A distinctive feature of luminal subtypes of breast cancer from TNBC is the ability to perform gluconeogenesis. Breast cancers with a positive expression of the HER2 receptor, in contrast to TNBC and luminal A subtype, have a distinctive active synthesis and consumption of fatty acids. It is interesting to note that amino acid transporters exhibit their activity depending on the pH level inside the cell. In the most aggressive forms of breast cancer or with the gradual progression of the disease, pH will also change, which will directly affect the metabolism of amino acids. Using the cell lines presented in this review, we can trace the characteristic features inherent in each of the molecular biological subtypes of breast cancer and develop the most optimal therapeutic targets.

Amino Acid Metabolism and Autophagy in Atherosclerotic Cardiovascular Disease

Cardiovascular disease is the most common cause of mortality globally, accounting for approximately one out of three deaths. The main underlying pathology is atherosclerosis, a dyslipidemia-driven, chronic inflammatory disease. The interplay between immune cells and non-immune cells is of great importance in the complex process of atherogenesis. During atheroprogression, intracellular metabolic pathways, such as amino acid metabolism, are master switches of immune cell function. Autophagy, an important stress survival mechanism involved in maintaining (immune) cell homeostasis, is crucial during the development of atherosclerosis and is strongly regulated by the availability of amino acids. In this review, we focus on the interplay between amino acids, especially L-leucine, L-arginine, and L-glutamine, and autophagy during atherosclerosis development and progression, highlighting potential therapeutic perspectives.

Metabolic drives affecting Th17/Treg gene expression changes and differentiation: impact on immune-microenvironment regulation

The CD4+ T-cell population plays a vital role in the adaptive immune system by coordinating the immune response against different pathogens. A significant transformation occurs in CD4+ cells during an immune response, as they shift from a dormant state to an active state. This transformation leads to extensive proliferation, differentiation, and cytokine production, which contribute to regulating and coordinating the immune response. Th17 and Treg cells are among the most intriguing CD4+ T-cell subpopulations in terms of genetics and metabolism. Gene expression modulation processes rely on and are linked to metabolic changes in cells. Lactylation is a new model that combines metabolism and gene modulation to drive Th17/Treg differentiation and functional processes. The focus of this review is on the metabolic pathways that impact lymphocyte gene modulation in a functionally relevant manner.

Targeting the glutamine-arginine-proline metabolism axis in cancer

Metabolic abnormalities are an important feature of tumours. The glutamine-arginine-proline axis is an important node of cancer metabolism and plays a major role in amino acid metabolism. This axis also acts as a scaffold for the synthesis of other nonessential amino acids and essential metabolites. In this paper, we briefly review (1) the glutamine addiction exhibited by tumour cells with accelerated glutamine transport and metabolism; (2) the methods regulating extracellular glutamine entry, intracellular glutamine synthesis and the fate of intracellular glutamine; (3) the glutamine, proline and arginine metabolic pathways and their interaction; and (4) the research progress in tumour therapy targeting the glutamine-arginine-proline metabolic system, with a focus on summarising the therapeutic research progress of strategies targeting of one of the key enzymes of this metabolic system, P5CS (ALDH18A1). This review provides a new basis for treatments targeting the metabolic characteristics of tumours.

Fueling the fight against cancer: Exploring the impact of branched-chain amino acid catalyzation on cancer and cancer immune microenvironment

Metabolism of Branched-chain amino acids (BCAAs) is essential for the nutrient necessities in mammals. Catalytic enzymes serve to direct the whole-body BCAAs oxidation which involve in the development of various metabolic disorders. The reprogrammed metabolic elements are also responsible for malignant oncogenic processes, and favor the formation of distinctive immunosuppressive microenvironment surrounding different cancers. The impotent immune surveillance related to BCAAs dysfunction is a novel topic to investigate. Here we focus on the BCAA catalysts that contribute to metabolic changes and dysregulated immune reactions in cancer progression. We summarize the current knowledge of BCAA catalyzation, highlighting the interesting roles of BCAA metabolism in the treatment of cancers.

KLF7 Promotes Hepatocellular Carcinoma Progression Through Regulating SLC1A5-Mediated Tryptophan Metabolism

Krüppel-like factor 7 is a transcriptional activator and acts as an oncogene in human cancers, including hepatocellular carcinoma (HCC). Tryptophan metabolism is important for HCC cell proliferation, metastasis, and invasion. It is unclear whether KLF7 could regulate Trp metabolism in HCC. In this study, we found that Trp metabolism was suppressed in HCC cells with KLF7 knockdown. The mRNA and protein levels of SLC1A5, SLC7A5, and TPH1, as well as the content of Trp and serotonin, were reduced after KLF7 knockdown, and were potentiated following KLF7 overexpression. Increasing the content of serotonin could restore the malignancy of tumour cells in vitro and tumour growth in vivo. Conversely, decreasing the content of serotonin suppressed HCC cell proliferation. The binding activity of KLF7 was on the promoter of SLC1A5, and KLF7 positively regulated the expression of SLC1A5. KLF7 contributed to the proliferation and migration of HCC cells by up-regulation of SLC1A5. Collectively, KLF7 promotes the progression of HCC through regulating Trp metabolism. The newly identified axis of KLF7/ SLC1A5 in HCC could represent a potential target for HCC therapy.

Molecular Mechanisms Underlying Initiation and Activation of Autophagy

Autophagy is an important catabolic process to maintain cellular homeostasis and antagonize cellular stresses. The initiation and activation are two of the most important aspects of the autophagic process. This review focuses on mechanisms underlying autophagy initiation and activation and signaling pathways regulating the activation of autophagy found in recent years. These findings include autophagy initiation by liquid-liquid phase separation (LLPS), autophagy initiation in the endoplasmic reticulum (ER) and Golgi apparatus, and the signaling pathways mediated by the ULK1 complex, the mTOR complex, the AMPK complex, and the PI3KC3 complex. Through the review, we attempt to present current research progress in autophagy regulation and forward our understanding of the regulatory mechanisms and signaling pathways of autophagy initiation and activation.

Huangqin tang alleviates colitis-associated colorectal cancer via amino acids homeostasisand PI3K/AKT/mtor pathway modulation

ETHNOPHARMACOLOGICAL RELEVANCE

Huangqin Tang (HQT), a traditional Chinese medicine formula, is commonly used in clinical practice for the treatment of inflammatory bowel diseases. It has been reported that HQT exerts antitumor effects on colitis-associated colorectal cancer (CAC). However, the mechanism by which HQT interferes with the inflammation-to-cancer transformation remains unclear.

AIMS OF THE STUDY

The purpose of this study was to dynamically evaluate the efficacy of HQT in alleviating or delaying CAC and to reveal the underlying mechanism.

METHODS

We established a mouse model of CAC using azoxymethane combined with 1.5% dextran sodium sulphate. The efficacy of HQT was evaluated based on pathological sections and serum biochemical indices. Subsequently, amino acids (AAs) metabolism analyses were performed using ultra-performance liquid chromatography-tandem mass spectrometry, and the phosphatidylinositol 3 kinase/protein kinase B/mechanistic target of rapamycin (PI3K/AKT/mTOR) pathway was detected by western blotting.

RESULTS

The data demonstrated that HQT could alleviate the development of CAC in the animal model. HQT effectively reduced the inflammatory response, particularly interleukin-6 (IL-6), in the inflammation induction stage, as well as in the stages of proliferation initiation and tumorigenesis. During the proliferation initiation and tumorigenesis stages, immunohistochemistry staining showed that the expression of the proliferation marker Ki67 was reduced, while apoptosis was increased in the HQT group. Accordingly, HQT substantially decreased the levels of specific AAs in the colon with CAC, including glutamic acid, glutamine, arginine, and isoleucine. Furthermore, HQT significantly inhibited the activated PI3K/AKT/mTOR pathway, which may contribute to suppression of cell proliferation and enhancement of apoptosis.

CONCLUSION

HQT is effective in alleviating and delaying the colon "inflammation-to-cancer". The mechanism of action may involve HQT maintained AAs metabolism homeostasis and regulated PI3K/AKT/mTOR pathway, so as to maintain the balance between proliferation and apoptosis, and then interfere in the occurrence and development of CAC.

Nutrient transporter pattern in CD56dim NK cells: CD16 (FcγRIIIA)-dependent modulation and association with memory NK cell functional profile

Background

Human memory NK cells represent a heterogeneous CD56dim population that expands and persists in human cytomegalovirus (HCMV)-seropositive healthy individuals. They are characterized by the preferential, not fully overlapping, expression of NKG2C (activating receptor for HLA-E) and CD57 maturation marker, and by the lack of FcεRIγ adaptor chain. Hyperresponsiveness to Fcγ receptor IIIA (CD16) engagement represents the distinctive functional signature of memory NK cells. Although CD16 engagement was shown to acutely enhance glycolytic and oxidative pathways, its capability to induce a persisting metabolic reprogramming of human NK cells is poorly understood yet.

Results

Here, we describe the peculiar nutrient transporter expression pattern of FcεRIγ- memory NK cells, characterized by higher levels of CD98 neutral amino acid antiporter and CD71 transferrin receptor, and lower expression of GLUT1 glucose transporter, with respect to FcεRIγ+ conventional NK cells. Although CD16 engagement acutely enhances glycolytic and oxidative pathways, its capability to induce a persisting metabolic reprogramming of human NK cells is poorly understood yet. Our results firstly show that sustained CD16 engagement by contact with IgG-opsonized target cells induces the mTORC1-dependent upregulation of CD98 and CD71 nutrient receptors on CD56dim NK cells, in a transporter-specific fashion, that is finely tuned by cell-dependent (grade of functional maturation, and memory or conventional lineage) and stimulus-dependent (time length and cooperation with cytokines) factors. We also demonstrate that CD98 antiporter function is required for CD16-dependent IFN-γ production, and that enhanced CD98-mediated neutral amino acid uptake associates with heightened memory NK cell functional response.

Conclusion

Collectively, our work documents that CD16 engagement leads to a metabolic rewiring of human NK cells and suggests that a distinct nutrient transporter expression pattern may contribute to memory NK cell peculiar functional features.

Discovering Root Causal Genes with High Throughput Perturbations

Root causal gene expression levels - or root causal genes for short - correspond to the initial changes to gene expression that generate patient symptoms as a downstream effect. Identifying root causal genes is critical towards developing treatments that modify disease near its onset, but no existing algorithms attempt to identify root causal genes from data. RNA-sequencing (RNA-seq) data introduces challenges such as measurement error, high dimensionality and non-linearity that compromise accurate estimation of root causal effects even with state-of-the-art approaches. We therefore instead leverage Perturb-seq, or high throughput perturbations with single cell RNA-seq readout, to learn the causal order between the genes. We then transfer the causal order to bulk RNA-seq and identify root causal genes specific to a given patient for the first time using a novel statistic. Experiments demonstrate large improvements in performance. Applications to macular degeneration and multiple sclerosis also reveal root causal genes that lie on known pathogenic pathways, delineate patient subgroups and implicate a newly defined omnigenic root causal model.

Exposure to the antiretroviral drug dolutegravir impairs structure and neurogenesis in a forebrain organoid model of human embryonic cortical development

Introduction

For many therapeutic drugs, including antiretroviral drugs used to treat people living with HIV-1 (PLWH), we have little data on the potential effects on the developing human brain due to limited access to tissue and historical constraints on the inclusion of pregnant populations in clinical trials. Human induced pluripotent stem cells (iPSCs) offer a new avenue to gain insight on how drugs may impact human cell types representative of the developing central nervous system. To prevent vertical transmission of HIV and promote the health of pregnant PLWH, antiretroviral therapy must be initiated and/or maintained throughout pregnancy. However, many antiretroviral drugs are approved for widespread use following clinical testing only in non-pregnant populations and there may be limited information on potential teratogenicity until pregnancy outcomes are evaluated. The integrase strand transfer inhibitor dolutegravir (DTG) is a frontline antiretroviral drug that is effective in viral suppression of HIV but was previously reported to be associated with a slight increase in the risk for neural tube defects in one study, although this has not been replicated in other cohorts.

Methods

To directly investigate the potential impact of DTG on human cortical neurogenesis, we measured the effects of daily drug exposure on the early stages of corticogenesis in a human iPSC-based forebrain organoid model. We quantified organoid size and structure and analyzed gene and protein expression to evaluate the impact of several doses of DTG on organoid development.

Results

We observed deficits in organoid structure and impaired neurogenesis in DTG-treated organoids compared to vehicle-treated control organoids after 20 or 40 days in culture. Our highest dose of DTG (10 μM) resulted in significantly smaller organoids with a reduced density of neural rosette structures compared to vehicle-treated controls. Mechanistically, RNA-sequencing and immunohistological analysis suggests dysregulated amino acid transport and activation of the integrated stress response in the DTG-treated organoids, and functionally, a small molecule integrated stress response inhibitor (ISRIB) could partially rescue increased expression of proteins related to cell cycle regulation.

Discussion

Together, these results illustrate the potential for human iPSC-based strategies to reveal biological processes during neurogenesis that may be affected by therapeutic drugs and provide complementary data in relevant human cell types to augment preclinical investigations of drug safety during pregnancy.

Double-Edge Effects of Leucine on Cancer Cells

Leucine is an essential amino acid that cannot be produced endogenously in the human body and therefore needs to be obtained from dietary sources. Leucine plays a pivotal role in stimulating muscle protein synthesis, along with isoleucine and valine, as the group of branched-chain amino acids, making them one of the most popular dietary supplements for athletes and gym-goers. The individual effects of leucine, however, have not been fully clarified, as most of the studies so far have focused on the grouped effects of branched-chain amino acids. In recent years, leucine and its metabolites have been shown to stimulate muscle protein synthesis mainly via the mammalian target of the rapamycin complex 1 signaling pathway, thereby improving muscle atrophy in cancer cachexia. Interestingly, cancer research suggests that leucine may have either anti-cancer or pro-tumorigenic effects. In the current manuscript, we aim to review leucine's roles in muscle protein synthesis, tumor suppression, and tumor progression, specifically summarizing the molecular mechanisms of leucine's action. The role of leucine is controversial in hepatocellular carcinoma, whereas its pro-tumorigenic effects have been demonstrated in breast and pancreatic cancers. In summary, leucine being used as nutritional supplement for athletes needs more attention, as its pro-oncogenic effects may have been identified by recent studies. Anti-cancer or pro-tumorigenic effects of leucine in various cancers should be further investigated to achieve clear conclusions.

Glutamine: A key player in human metabolism as revealed by hyperpolarized magnetic resonance

In recent years, there has been remarkable progress in the field of dissolution dynamic nuclear polarization (D-DNP). This method has shown significant potential for enhancing nuclear polarization by over 10,000 times, resulting in a substantial increase in sensitivity. The unprecedented signal enhancements achieved with D-DNP have opened new possibilities for in vitro analysis. This method enables the monitoring of structural and enzymatic kinetics with excellent time resolution at low concentrations. Furthermore, these advances can be straightforwardly translated to in vivo magnetic resonance imaging and magnetic resonance spectroscopy (MRI and MRS) experiments. D-DNP studies have used a range of 13C labeled molecules to gain deeper insights into the cellular metabolic pathways and disease hallmarks. Over the last 15 years, D-DNP has been used to analyze glutamine, a key player in the cellular metabolism, involved in many diseases including cancer. Glutamine is the most abundant amino acid in blood plasma and the major carrier of nitrogen, and it is converted to glutamate inside the cell, where the latter is the most abundant amino acid. It has been shown that increased glutamine consumption by cells is a hallmark of tumor cancer metabolism. In this review, we first highlight the significance of glutamine in metabolism, providing an in-depth description of its use at the cellular level as well as its specific roles in various organs. Next, we present a comprehensive overview of the principles of D-DNP. Finally, we review the state of the art in D-DNP glutamine analysis and its application in oncology, neurology, and perfusion marker studies.

In silico analysis shows slc1a4 as a potential target of hsa-mir-133a for regulating glutamine metabolism in gastric cancer

Cutting-edge research has spotlighted glutamine metabolism as a promising therapeutic target in managing gastric cancer. This investigation highlights the upregulated glutamine transporters by leveraging clinical data from the TCGA Database and the expression analysis of the transcriptome profile of stomach adenocarcinoma (STAD) patients. Notably, it identifies SLC1A4 as a potential glutamine transporter in STAD. The screening of human miRNAs conducted using the TargetScan database, and the subsequent docking analysis present multiple miRNAs with the potential of being explored as therapeutic agents. By integrating transcriptome profiling, miRNA screening, and molecular docking, this study reveals, for the first time, the potential of hsa-mir-133a-1 in targeting slc1a4, along with its known target mTOR, in stomach cancer. The myriad interactions that can be regulated by this silencing mechanism are anticipated to ultimately reduce glutamine uptake in STAD. This study provides compelling evidence of glutamine transport via SLC1A4 in stomach cancer and delves into how it might impact mTOR and some of its pivotal downstream molecules. Considering these findings, novel therapeutic strategies can be devised to further enhance existing methods for combating gastric cancer.

Growing Macrophages Regulate High Rates of Solute Flux by Pinocytosis

In metazoan cells, growth factors stimulate solute ingestion by pinocytosis. To examine the role of pinocytosis in cell growth, this study measured cell proliferation and the attendant rates of solute flux by pinocytosis in murine macrophages in response to the growth factor colony-stimulating factor-1 (CSF1). During CSF1-dependent growth in rich medium, macrophages internalized 72 percent of their cell volume in extracellular fluid every hour. Removal of the essential amino acid leucine from growth medium limited rates of protein synthesis and growth, but increased rates of solute accumulation by macropinocytosis. The amount of protein synthesized during leucine-dependent growth exceeded the capacity of pinocytosis to internalize enough soluble leucine to support growth and proliferation. Fluid-phase solute recycling from lysosomes secreted small molecules from the cells at high rates. Inhibitors of pinocytosis and the mechanistic target-of-rapamycin (mTOR) reduced cell growth and solute recycling, indicating roles for pinocytosis in growth and for nutrient sensing in the regulation of solute flux by pinocytosis.

Synergistic Role of Amino Acids in Enhancing mTOR Activation Through Lysosome Positioning

Lysosome positioning, or lysosome cellular distribution, is critical for lysosomal functions in response to both extracellular and intracellular cues. Amino acids, as essential nutrients, have been shown to promote lysosome movement toward the cell periphery. Peripheral lysosomes are involved in processes such as lysosomal exocytosis, cell migration, and metabolic signaling-functions that are particularly important for cancer cell motility and growth. However, the specific types of amino acids that regulate lysosome positioning, their underlying mechanisms, and their connection to amino acid-regulated metabolic signaling remain poorly understood. In this study, we developed a high-content imaging system for unbiased, quantitative analysis of lysosome positioning. We examined the 15 amino acids present in cell culture media and found that 10 promoted lysosome redistribution toward the cell periphery to varying extents, with aromatic amino acids showing the strongest effect. This redistribution was mediated by promoting outward transport through SLC38A9-BORC-kinesin 1/3 axis and simultaneously reducing inward transport via inhibiting the recruitment of Rab7 and JIP4 onto lysosomes. When examining the effects of amino acids on mTOR activation-a central regulator of cell metabolism-we found that the amino acids most strongly promoting lysosome dispersal, such as phenylalanine, did not activate mTOR on their own. However, combining phenylalanine with arginine, which activates mTOR without affecting lysosome positioning, synergistically enhanced mTOR activity. This synergy was lost when lysosomes failed to localize to the cell periphery, as observed in kinesin 1/3 knockout (KO) cells. Furthermore, breast cancer cells exhibited heightened sensitivity to phenylalanine-induced lysosome dispersal compared to noncancerous breast cells. Inhibition of LAT1, the amino acid transporter responsible for phenylalanine uptake, reduced peripheral lysosomes and impaired cancer cell migration and proliferation, highlighting the importance of lysosome positioning in these coordinated cellular activities. In summary, amino acid-regulated lysosome positioning and mTOR signaling depend on distinct sets of amino acids. Combining lysosome-dispersing amino acids with mTOR-activating amino acids synergistically enhances mTOR activation, which may be particularly relevant in cancer cells.

Glutamine maintains the stability of alveolar structure and function after lung transplantation by inhibiting autophagy

Excessive autophagy may lead to degradation and damage of alveolar epithelial cells after lung transplantation, eventually leading to alveolar epithelial cell loss, affecting the structural integrity and function of alveoli. Glutamine (Gln), a nutritional supplement, regulates autophagy through multiple signaling pathways. In this study, we explored the protective role of Gln on alveolar epithelial cells by inhibiting autophagy. In vivo, a rat orthotopic lung transplant model was carried out to evaluate the therapeutic effect of glutamine. Ischemia/reperfusion (I/R) induced alveolar collapse, edema, epithelial cell apoptosis, and inflammation, which led to a reduction of alveolar physiological function, such as an increase in peak airway pressure, and a decrease in lung compliance and oxygenation index. In comparison, Gln preserved alveolar structure and function by reducing alveolar apoptosis, inflammation, and edema. In vitro, a hypoxia/reoxygenation (H/R) cell model was performed to simulate IR injury on mouse lung epithelial (MLE) cells and human lung bronchus epithelial (Beas-2B) cells. H/R impaired the proliferation of epithelial cells and triggered cell apoptosis. In contrast, Gln normalized cell proliferation and suppressed I/R-induced cell apoptosis. The activation of mTOR and the downregulation of autophagy-related proteins (LC3, Atg5, Beclin1) were observed in Gln-treated lung tissues and alveolar epithelial cells. Both in vivo and in vitro, rapamycin, a classical mTOR inhibitor, reversed the beneficial effects of Gln on alveolar structure and function. Taken together, Glnpreserved alveolar structure and function after lung transplantation by inhibiting autophagy.

Growth Signaling Networks Orchestrate Cancer Metabolic Networks

Normal cells grow and divide only when instructed to by signaling pathways stimulated by exogenous growth factors. A nearly ubiquitous feature of cancer cells is their capacity to grow independent of such signals, in an uncontrolled, cell-intrinsic manner. This property arises due to the frequent oncogenic activation of core growth factor signaling pathway components, including receptor tyrosine kinases, PI3K-AKT, RAS-RAF, mTORC1, and MYC, leading to the aberrant propagation of pro-growth signals independent of exogenous growth factors. The growth of both normal and cancer cells requires the acquisition of nutrients and their anabolic conversion to the primary macromolecules underlying biomass production (protein, nucleic acids, and lipids). The core growth factor signaling pathways exert tight regulation of these metabolic processes and the oncogenic activation of these pathways drive the key metabolic properties of cancer cells and tumors. Here, we review the molecular mechanisms through which these growth signaling pathways control and coordinate cancer metabolism.

A strategy for improving silk yield and organ size in silk-producing insects

Insect silks possess excellent biodegradability, biocompatibility and mechanical properties, and have numerous applications in biomedicine and tissue engineering. However, the application of silk fiber is hindered by its limited supply, especially from non-domesticated insects. In the present study, the silk yield and organ size of Bombyx mori were significantly improved through genetic manipulation of the target of rapamycin complex 1 (TORC1) pathway components. Silk protein synthesis and silk gland size were decreased following rapamycin treatment, inhibiting the TORC1 signaling pathway both in vivo and ex vivo. The overexpression of posterior silk gland-specific Rheb and BmSLC7A5 improved silk protein synthesis and silk gland size by activating the TORC1 signaling pathway. Silk yield in BmSLC7A5-overexpression silkworms was significantly increased by approximately 25%. We have demonstrated that the TORC1 signaling pathway is involved in the transcription and translation of silk genes and transcriptional activators via phosphorylation of p70 S6 kinase 1 and 4E-binding protein 1. Our findings present a strategy for increasing silk yield and organ size in silk-producing insects.

Oncogenic Control of Metabolism

A cell committed to proliferation must reshape its metabolism to enable robust yet balanced production of building blocks for the assembly of proteins, lipids, nucleic acids, and other macromolecules, from which two functional daughter cells can be produced. The metabolic remodeling associated with proliferation is orchestrated by a number of pro-proliferative signaling nodes, which include phosphatidylinositol-3 kinase (PI3K), the RAS family of small GTPases, and transcription factor c-myc In metazoan cells, these signals are activated in a paracrine manner via growth factor-mediated activation of receptor (or receptor-associated) tyrosine kinases. Such stimuli are limited in duration and therefore allow the metabolism of target cells to return to the resting state once the proliferation demands have been satisfied. Cancer cells acquire activating genetic alterations within common pro-proliferative signaling nodes. These alterations lock cellular nutrient uptake and utilization into a perpetual progrowth state, leading to the aberrant accumulation and spread of cancer cells.

Sodium chloride in the tumor microenvironment enhances T cell metabolic fitness and cytotoxicity

The efficacy of antitumor immunity is associated with the metabolic state of cytotoxic T cells, which is sensitive to the tumor microenvironment. Whether ionic signals affect adaptive antitumor immune responses is unclear. In the present study, we show that there is an enrichment of sodium in solid tumors from patients with breast cancer. Sodium chloride (NaCl) enhances the activation state and effector functions of human CD8+ T cells, which is associated with enhanced metabolic fitness. These NaCl-induced effects translate into increased tumor cell killing in vitro and in vivo. Mechanistically, NaCl-induced changes in CD8+ T cells are linked to sodium-induced upregulation of Na+/K+-ATPase activity, followed by membrane hyperpolarization, which magnifies the electromotive force for T cell receptor (TCR)-induced calcium influx and downstream TCR signaling. We therefore propose that NaCl is a positive regulator of acute antitumor immunity that might be modulated for ex vivo conditioning of therapeutic T cells, such as CAR T cells.

BmSLC7A5 is essential for silk protein synthesis and larval development in Bombyx mori

Insects produce silk to form cocoons, nests, and webs, which are important for their survival and reproduction. However, little is known about the molecular mechanism of silk protein synthesis at the translation level. The solute carrier family 7 (SLC7) genes are involved in activating the target of rapamycin complex 1 (TORC1) signaling pathway and protein translation process, but the physiological roles of SLC7 genes in silk-producing insects have not been reported. Here, we found that amino acid signaling regulates silk protein synthesis and larval development via the L-type amino acid transporter 1 (LAT1; also known as SLC7A5) in Bombyx mori. A total of 12 SLC7 homologs were identified in the silkworm genome, among which BmSLC7A5 was found to be a silk gland-enriched gene and may be involved in leucine transport. Bioinformatics analysis indicated that SLC7A5 displays high homology and a close phylogenetic relationship in silk-producing insects. Subsequently, we found that leucine treatment significantly increased silk protein synthesis by improving the transcription and protein levels of silk genes. Furthermore, systemic and silk gland-specific knockout of BmSLC7A5 led to decreased silk protein synthesis by inhibiting TORC1 signaling, and somatic mutation also resulted in arrested development from the 5th instar to the early pupal stage. Altogether, our study reveals that BmSLC7A5 is involved in regulating silk protein synthesis and larval development by affecting the TORC1 signaling pathway, which provides a new strategy and target for improving silk yield.

Salidroside sensitizes Triple-negative breast cancer to ferroptosis by SCD1-mediated lipogenesis and NCOA4-mediated ferritinophagy

INTRODUCTION

Triple-negative breast cancer (TNBC) is the primary cause of breast cancer-induced death in women. Literature has confirmed the benefits of Salidroside (Sal) in treating TNBC. However, the study about potential therapeutic targets and mechanisms of Sal-anchored TNBC remains limited.

OBJECTIVE

This study was designed to explore the main targets and potential mechanisms of Sal against TNBC.

METHODS

Network pharmacology, bioinformatics, and machine learning algorithm strategies were integrated to examine the role, potential targets, and mechanisms of the Sal act in TNBC. MDA-MB-231 cells and tumor-bearing nude mice were chosen for in vitro and in vivo experimentation. Cell viability and cytotoxicity were determined using CCK-8, LDH test, and Calcein-AM/PI staining. Antioxidant defense, lipid peroxidation, and iron metabolism were explored using glutathione, glutathione peroxidase, malondialdehyde (MDA), C11-BODIPY 581/591 probe, and FerroOrange dye. Glutathione peroxidase 4 (GPX4) or stearoyl-CoA desaturase 1 (SCD1) overexpression or nuclear receptor co-activator 4 (NCOA4) deficiency was performed to demonstrate the mechanism of Sal on TNBC.

RESULTS

The prediction results confirmed that 22 ferroptosis-related genes were identified in Sal and TNBC, revealing that the potential mechanism of the Sal act on TNBC was linked with ferroptosis. Besides, these genes were mainly involved in the mTOR, PI3K/AKT, and autophagy signaling pathway by functional enrichment analysis. The in vitro validation results confirmed that Sal inhibited TNBC cell proliferation by modulating ferroptosis via elevation of intracellular Fe2+ and lipid peroxidation. Mechanistically, Sal sensitized TNBC cells to ferroptosis by inhibiting the PI3K/AKT/mTOR axis, thereby suppressing SCD1-mediated lipogenesis of monounsaturated fatty acids to induce lipid peroxidation, additionally facilitating NCOA4-mediated ferritinophagy to increase intracellular Fe2+ content. The GPX4 or SCD1 overexpression or NCOA4 deficiency results further supported our mechanistic studies. In vivo experimentation confirmed that Sal is vital for slowing down tumor growth by inducing ferroptosis.

CONCLUSIONS

Overall, this study elucidates TNBC pathogenesis closely linked to ferroptosis and identifies potential biomarkers in TNBC. Meanwhile, the study elucidates that Sal sensitizes TNBC to ferroptosis by SCD1-mediated lipogenesis and NCOA4-mediated ferritinophagy, regulated by PI3K/AKT/mTOR signaling pathways. Our findings provide a theoretical basis for applying Sal to treat TNBC.

Glutamine availability regulates cDC subsets in tissue

Proliferating tumor cells take up glutamine for anabolic processes engendering glutamine deficiency in the tumor microenvironment. How this might impact immune cells is not well understood. Using multiple mouse models of soft tissue sarcomas, glutamine antagonists, as well as genetic and pharmacological inhibition of glutamine utilization, we found that the number and frequency of conventional dendritic cells (cDC) is dependent on microenvironmental glutamine levels. cDCs comprise two distinct subsets - cDC1 and cDC2, with the former subset playing a critical role in antigen cross-presentation and tumor immunity. While both subsets show dependence on Glutamine, cDC1s are particularly sensitive. Notably, glutamine antagonism did not reduce the frequency of DC precursors but decreased proliferation and survival of cDC1s. Further studies suggest a role of the nutrient sensing mTOR signaling pathway in this process. Taken together, these findings uncover glutamine dependence of cDC1s that is coopted by tumors to escape immune responses.

One Sentence Summary

Type 1 conventional dendritic cells require glutamine to maintain their number in non-lymphoid tissue.

Significance

Immune evasion is a key hallmark of cancer; however, the underlying pathways are diverse, tumor-specific and not fully elucidated. Many tumor cells avidly import glutamine to support their anabolic needs, creating a glutamine-deficient tumor microenvironment (TME). Herein, using mouse models of soft tissue sarcomas, we show that glutamine depletion in TME leads to reduced type 1 conventional dendritic cells - a cell type that is critical for adaptive immune responses. This work is a paradigm for how tumor cell metabolism can regulate anti-tumor immune responses and will be foundational to future efforts targeting glutamine metabolism for cancer immunotherapy.

MicroRNAs in metabolism for precision treatment of lung cancer

The dysregulation of miRNAs in lung cancer has been extensively documented, with specific miRNAs acting as both tumor suppressors and oncogenes, depending on their target genes. Recent research has unveiled the regulatory roles of miRNAs in key metabolic pathways, such as glycolysis, the tricarboxylic acid cycle, fatty acid metabolism, and autophagy, which collectively contribute to the aberrant energy metabolism characteristic of cancer cells. Furthermore, miRNAs are increasingly recognized as critical modulators of the tumor microenvironment, impacting immune response and angiogenesis. This review embarks on a comprehensive journey into the world of miRNAs, unraveling their multifaceted roles, and more notably, their emerging significance in the context of cancer, with a particular focus on lung cancer. As we navigate this extensive terrain, we will explore the fascinating realm of miRNA-mediated metabolic rewiring, a phenomenon that plays a pivotal role in the progression of lung cancer and holds promise in the development of novel therapeutic strategies.

VCP/p97 UFMylation stabilizes BECN1 and facilitates the initiation of autophagy

Macroautophagy/autophagy is essential for the degradation and recycling of cytoplasmic materials. The initiation of this process is determined by phosphatidylinositol-3-kinase (PtdIns3K) complex, which is regulated by factor BECN1 (beclin 1). UFMylation is a novel ubiquitin-like modification that has been demonstrated to modulate several cellular activities. However, the role of UFMylation in regulating autophagy has not been fully elucidated. Here, we found that VCP/p97 is UFMylated on K109 by the E3 UFL1 (UFM1 specific ligase 1) and this modification promotes BECN1 stabilization and assembly of the PtdIns3K complex, suggesting a role for VCP/p97 UFMylation in autophagy initiation. Mechanistically, VCP/p97 UFMylation stabilizes BECN1 through ATXN3 (ataxin 3)-mediated deubiquitination. As a key component of the PtdIns3K complex, stabilized BECN1 facilitates assembly of this complex. Re-expression of VCP/p97, but not the UFMylation-defective mutant, rescued the VCP/p97 depletion-induced increase in MAP1LC3B/LC3B protein expression. We also showed that several pathogenic VCP/p97 mutations identified in a variety of neurological disorders and cancers were associated with reduced UFMylation, thus implicating VCP/p97 UFMylation as a potential therapeutic target for these diseases. Abbreviation: ATG14:autophagy related 14; Baf A1:bafilomycin A1;CMT2Y: Charcot-Marie-Toothdisease, axonal, 2Y; CYB5R3: cytochromeb5 reductase 3; DDRGK1: DDRGK domain containing 1; DMEM:Dulbecco'smodified Eagle's medium;ER:endoplasmic reticulum; FBS:fetalbovine serum;FTDALS6:frontotemporaldementia and/or amyotrophic lateral sclerosis 6; IBMPFD1:inclusion bodymyopathy with early-onset Paget disease with or withoutfrontotemporal dementia 1; LC-MS/MS:liquid chromatography tandem mass spectrometry; MAP1LC3B/LC3B:microtubule associated protein 1 light chain 3 beta; MS: massspectrometry; NPLOC4: NPL4 homolog, ubiquitin recognition factor;PIK3C3: phosphatidylinositol 3-kinase catalytic subunit type 3;PIK3R4: phosphoinositide-3-kinase regulatory subunit 4; PtdIns3K:phosphatidylinositol 3-kinase; RPL26: ribosomal protein L26; RPN1:ribophorin I; SQSTM1/p62: sequestosome 1; UBA5: ubiquitin likemodifier activating enzyme 5; UFC1: ubiquitin-fold modifierconjugating enzyme 1; UFD1: ubiquitin recognition factor in ERassociated degradation 1; UFL1: UFM1 specific ligase 1; UFM1:ubiquitin fold modifier 1; UFSP2: UFM1 specific peptidase 2; UVRAG:UV radiation resistance associated; VCP/p97: valosin containingprotein; WT: wild-type.

The interplay of the circadian clock and metabolic tumorigenesis

The circadian clock and cell metabolism are both dysregulated in cancer cells through intrinsic cell-autonomous mechanisms and external influences from the tumor microenvironment. The intricate interplay between the circadian clock and cancer cell metabolism exerts control over various metabolic processes, including aerobic glycolysis, de novo nucleotide synthesis, glutamine and protein metabolism, lipid metabolism, mitochondrial metabolism, and redox homeostasis in cancer cells. Importantly, oncogenic signaling can confer a moonlighting function on core clock genes, effectively reshaping cellular metabolism to fuel cancer cell proliferation and drive tumor growth. These interwoven regulatory mechanisms constitute a distinctive feature of cancer cell metabolism.

Aerobic glycolysis but not GLS1-dependent glutamine metabolism is critical for anti-tumor immunity and response to checkpoint inhibition

Tumor cells undergo uncontrolled proliferation driven by enhanced anabolic metabolism including glycolysis and glutaminolysis. Targeting these pathways to inhibit cancer growth is a strategy for cancer treatment. Critically, however, tumor-responsive T cells share metabolic features with cancer cells, making them susceptible to these treatments as well. Here, we assess the impact on anti-tumor T cell immunity and T cell exhaustion by genetic ablation of lactate dehydrogenase A (LDHA) and glutaminase1 (GLS1), key enzymes in aerobic glycolysis and glutaminolysis. Loss of LDHA severely impairs expansion of T cells in response to tumors and chronic infection. In contrast, T cells lacking GLS1 can compensate for impaired glutaminolysis by engaging alternative pathways, including upregulation of asparagine synthetase, and thus efficiently respond to tumor challenge and chronic infection as well as immune checkpoint blockade. Targeting GLS1-dependent glutaminolysis, but not aerobic glycolysis, may therefore be a successful strategy in cancer treatment, particularly in combination with immunotherapy.

Targeting amino acid-metabolizing enzymes for cancer immunotherapy

Despite the immune system's role in the detection and eradication of abnormal cells, cancer cells often evade elimination by exploitation of various immune escape mechanisms. Among these mechanisms is the ability of cancer cells to upregulate amino acid-metabolizing enzymes, or to induce these enzymes in tumor-infiltrating immunosuppressive cells. Amino acids are fundamental cellular nutrients required for a variety of physiological processes, and their inadequacy can severely impact immune cell function. Amino acid-derived metabolites can additionally dampen the anti-tumor immune response by means of their immunosuppressive activities, whilst some can also promote tumor growth directly. Based on their evident role in tumor immune escape, the amino acid-metabolizing enzymes glutaminase 1 (GLS1), arginase 1 (ARG1), inducible nitric oxide synthase (iNOS), indoleamine 2,3-dioxygenase 1 (IDO1), tryptophan 2,3-dioxygenase (TDO) and interleukin 4 induced 1 (IL4I1) each serve as a promising target for immunotherapeutic intervention. This review summarizes and discusses the involvement of these enzymes in cancer, their effect on the anti-tumor immune response and the recent progress made in the preclinical and clinical evaluation of inhibitors targeting these enzymes.

Soy Peptide Supplementation Mitigates Undernutrition through Reprogramming Hepatic Metabolism in a Novel Undernourished Non-Human Primate Model

In spite of recent advances in the field of undernutrition, current dietary therapy relying on the supply of high protein high calorie formulas is still plagued with transient recovery of impaired organs resulting in significant relapse of cases. This is partly attributed to the inadequacy of current research models in recapitulating clinical undernutrition for mechanistic exploration. Using 1636 Macaca fascicularis monkeys, a human-relevant criterion for determining undernutrition weight-for-age z-score (WAZ), with a cutoff point of ≤ -1.83 is established as the benchmark for identifying undernourished nonhuman primates (U-NHPs). In U-NHPs, pathological anomalies in multi-organs are revealed. In particular, severe dysregulation of hepatic lipid metabolism characterized by impaired fatty acid oxidation due to mitochondria dysfunction, but unlikely peroxisome disorder, is identified as the anchor metabolic aberration in U-NHPs. Mitochondria dysfunction is typified by reduced mito-number, accumulated long-chain fatty acids, and disruption of OXPHOS complexes. Soy peptide-treated U-NHPs increase in WAZ scores, in addition to attenuated mitochondria dysfunction and restored OXPHOS complex levels. Herein, innovative criteria for identifying U-NHPs are developed, and unknown molecular mechanisms of undernutrition are revealed hitherto, and it is further proved that soypeptide supplementation reprogramed mitochondrial function to re-establish lipid metabolism balance and mitigated undernutrition.

Research progress of T cell autophagy in autoimmune diseases

T cells, as a major lymphocyte population involved in the adaptive immune response, play an important immunomodulatory role in the early stages of autoimmune diseases. Autophagy is a cellular catabolism mediated by lysosomes. Autophagy maintains cell homeostasis by recycling degraded cytoplasmic components and damaged organelles. Autophagy has a protective effect on cells and plays an important role in regulating T cell development, activation, proliferation and differentiation. Autophagy mediates the participation of T cells in the acquired immune response and plays a key role in antigen processing as well as in the maintenance of T cell homeostasis. In autoimmune diseases, dysregulated autophagy of T cells largely influences the pathological changes. Therefore, it is of great significance to study how T cells play a role in the immune mechanism of autoimmune diseases through autophagy pathway to guide the clinical treatment of diseases.

Anticancer Effect of PtIIPHENSS, PtII5MESS, PtII56MESS and Their Platinum(IV)-Dihydroxy Derivatives against Triple-Negative Breast Cancer and Cisplatin-Resistant Colorectal Cancer

Development of resistance to cisplatin, oxaliplatin and carboplatin remains a challenge for their use as chemotherapies, particularly in breast and colorectal cancer. Here, we compare the anticancer effect of novel complexes [Pt(1,10-phenanthroline)(1S,2S-diaminocyclohexane)](NO3)2 (PtIIPHENSS), [Pt(5-methyl-1,10-phenanthroline)(1S,2S-diaminocyclohexane)](NO3)2 (PtII5MESS) and [Pt(5,6-dimethyl-1,10-phenanthroline)(1S,2S-diaminocyclohexane)](NO3)2 (PtII56MESS) and their platinum(IV)-dihydroxy derivatives with cisplatin. Complexes are greater than 11-fold more potent than cisplatin in both 2D and 3D cell line cultures with increased selectivity for cancer cells over genetically stable cells. ICP-MS studies showed cellular uptake occurred through an active transport mechanism with considerably altered platinum concentrations found in the cytoskeleton across all complexes after 24 h. Significant reactive oxygen species generation was observed, with reduced mitochondrial membrane potential at 72 h of treatment. Late apoptosis/necrosis was shown by Annexin V-FITC/PI flow cytometry assay, accompanied by increased sub-G0/G1 cells compared with untreated cells. An increase in S and G2+M cells was seen with all complexes. Treatment resulted in significant changes in actin and tubulin staining. Intrinsic and extrinsic apoptosis markers, MAPK/ERK and PI3K/AKT activation markers, together with autophagy markers showed significant activation of these pathways by Western blot. The proteomic profile investigated post-72 h of treatment identified 1597 MDA-MB-231 and 1859 HT29 proteins quantified by mass spectroscopy, with several differentially expressed proteins relative to no treatment. GO enrichment analysis revealed a statistically significant enrichment of RNA/DNA-associated proteins in both the cell lines and specific additional processes for individual drugs. This study shows that these novel agents function as multi-mechanistic chemotherapeutics, offering promising anticancer potential, and thereby supporting further research into their application as cancer therapeutics.

Reciprocal interactions between neuropeptide F and RYamide regulate host attraction in the mosquito Aedes aegypti

Female mosquitoes produce eggs in gonadotrophic cycles that are divided between a previtellogenic and vitellogenic phase. Previtellogenic females consume water and sugar sources like nectar while also being attracted to hosts for blood feeding. Consumption of a blood meal activates the vitellogenic phase, which produces mature eggs and suppresses host attraction. In this study, we tested the hypothesis that neuropeptide Y-like hormones differentially modulate host attraction behavior in the mosquito Aedes aegypti. A series of experiments collectively indicated that enteroendocrine cells (EECs) in the posterior midgut produce and release neuropeptide F (NPF) into the hemolymph during the previtellogenic phase which stimulates attraction to humans and biting behavior. Consumption of a blood meal, which primarily consists of protein by dry weight, down-regulated NPF in EECs until mature eggs developed, which was associated with a decline in hemolymph titer. NPF depletion depended on protein digestion but was not associated with EEC loss. Other experiments showed that neurons in the terminal ganglion extend axons to the posterior midgut and produce RYamide, which showed evidence of increased secretion into circulation after a blood meal. Injection of RYamide-1 and -2 into previtellogenic females suppressed host attraction, while coinjection of RYamides with or without short NPF-2 also inhibited the host attraction activity of NPF. Overall, our results identify NPF and RYamide as gut-associated hormones in A. aegypti that link host attraction behavior to shifts in diet during sequential gonadotrophic cycles.

New insights into the interplay between autophagy, gut microbiota and insulin resistance in metabolic syndrome

Metabolic syndrome (MetS) is a widespread and multifactorial disorder, and the study of its pathogenesis and treatment remains challenging. Autophagy, an intracellular degradation system that maintains cellular renewal and homeostasis, is essential for maintaining antimicrobial defense, preserving epithelial barrier integrity, promoting mucosal immune response, maintaining intestinal homeostasis, and regulating gut microbiota and microbial metabolites. Dysfunctional autophagy is implicated in the pathological mechanisms of MetS, involving insulin resistance (IR), chronic inflammation, oxidative stress, and endoplasmic reticulum (ER) stress, with IR being a predominant feature. The study of autophagy represents a valuable field of research with significant clinical implications for identifying autophagy-related signals, pathways, mechanisms, and treatment options for MetS. Given the multifactorial etiology and various potential risk factors, it is imperative to explore the interplay between autophagy and gut microbiota in MetS more thoroughly. This will facilitate the elucidation of new mechanisms underlying the crosstalk among autophagy, gut microbiota, and MetS, thereby providing new insights into the diagnosis and treatment of MetS.

The potential therapeutic targets of glutamine metabolism in head and neck squamous cell carcinoma

Targeting metabolic reprogramming may be an effective strategy to enhance cancer treatment efficacy. Glutamine serves as a vital nutrient for cancer cells. Inhibiting glutamine metabolism has shown promise in preventing tumor growth both in vivo and in vitro through various mechanisms. Therefore, this review collates recent scientific literature concerning the correlation between glutamine metabolism and cancer treatment. Novel treatment modalities based on amino acid transporters, metabolites, and glutaminase are discussed. Moreover, we demonstrate the relationship between glutamine metabolism and tumor proliferation, drug resistance, and the tumor immune microenvironment, offering new perspectives for the clinical treatment of head and neck squamous cell carcinoma, particularly for combined therapies. Identifying innovative approaches for enhancing the efficacy of glutamine-based metabolic therapy is crucial to improving HNSCC treatment.

Claudin-4 Modulates Autophagy via SLC1A5/LAT1 as a Mechanism to Regulate Micronuclei

Genome instability is a hallmark of cancer crucial for tumor heterogeneity and is often a result of defects in cell division and DNA damage repair. Tumors tolerate genomic instability, but the accumulation of genetic aberrations is regulated to avoid catastrophic chromosomal alterations and cell death. In ovarian cancer tumors, claudin-4 is frequently upregulated and closely associated with genome instability and worse patient outcomes. However, its biological association with regulating genomic instability is poorly understood. Here, we used CRISPR interference and a claudin mimic peptide to modulate the claudin-4 expression and its function in vitro and in vivo. We found that claudin-4 promotes a tolerance mechanism for genomic instability through micronuclei generation in tumor cells. Disruption of claudin-4 increased autophagy and was associated with the engulfment of cytoplasm-localized DNA. Mechanistically, we observed that claudin-4 establishes a biological axis with the amino acid transporters SLC1A5 and LAT1, which regulate autophagy upstream of mTOR. Furthermore, the claudin-4/SLC1A5/LAT1 axis was linked to the transport of amino acids across the plasma membrane as one of the potential cellular processes that significantly decreased survival in ovarian cancer patients. Together, our results show that the upregulation of claudin-4 contributes to increasing the threshold of tolerance for genomic instability in ovarian tumor cells by limiting its accumulation through autophagy.

SIGNIFICANCE

Autophagy regulation via claudin-4/SLC1A5/LAT1 has the potential to be a targetable mechanism to interfere with genomic instability in ovarian tumor cells.

A novel SLC3A2-targeting antibody-drug conjugate exerts potent antitumor efficacy in head and neck squamous cell cancer

The development of innovative therapeutic strategies for head and neck squamous cell carcinoma (HNSCC) is a critical medical requirement. Antibody-drug conjugates (ADC) targeting tumor-specific surface antigens have demonstrated clinical effectiveness in treating hematologic and solid malignancies. Our investigation revealed high expression levels of SLC3A2 in HNSCC tissue and cell lines. This study aimed to develop a novel anti-SLC3A2 ADC and assess its antitumor effects on HNSCC both in vitro and in vivo. This study developed a potent anti-SLC3A2 ADC (19G4-MMAE) and systematically investigated its drug delivery potential and antitumor efficacy in preclinical models. This study revealed that 19G4-MMAE exhibited specific binding to SLC3A2 and effectively targeted lysosomes. Moreover, 19G4-MMAE induced a significant accumulation of reactive oxygen species (ROS) and apoptosis in SLC3A2-positive HNSCC cells. The compound demonstrated potent antitumor effects derived from MMAE against SLC3A2-expressing HNSCC in preclinical models, displaying a favorable safety profile. These findings suggest that targeting SLC3A2 with an anti-SLC3A2 ADC could be a promising therapeutic approach for treating HNSCC patients.