Serine synthesis pathway inhibition cooperates with dietary serine and glycine limitation for cancer therapy

Nutritional strategies in oncology: The role of dietary patterns in modulating tumor progression and treatment response

Dietary interventions can influence tumor growth by restricting tumor-specific nutritional requirements, altering the nutrient availability in the tumor microenvironment, or enhancing the cytotoxicity of anticancer drugs. Metabolic reprogramming of tumor cells, as a significant hallmark of tumor progression, has a profound impact on immune regulation, severely hindering tumor eradication. Dietary interventions can modify tumor metabolic processes to some extent, thereby further improving the efficacy of tumor treatment. In this review, we emphasize the impact of dietary patterns on tumor progression. By exploring the metabolic differences of nutrients in normal cells versus cancer cells, we further clarify how dietary patterns influence cancer treatment. We also discuss the effects of dietary patterns on traditional treatments such as immunotherapy, chemotherapy, radiotherapy, and the gut microbiome, thereby underscoring the importance of precision nutrition.

Ginsenoside Rd and chrysophanol: Modulating the serine-glycine-one-carbon pathway to enhance neuroprotection in intracerebral hemorrhage

BACKGROUND

Intracerebral hemorrhage (ICH) is a devastating neurological disorder characterized by oxidative stress, inflammatory cascades, and metabolic dysregulation. Ginsenoside Rd (G-Rd) and chrysophanol (Chr), two natural compounds with antioxidative and anti-inflammatory properties, have demonstrated neuroprotective potential, however, their mechanisms in ICH remain unclear.

OBJECTIVE

This study aimed to investigate the protective effects of G-Rd and Chr against heme-induced injury in HT22 cells and in a rat model of ICH, with a focus on oxidative stress, inflammation, apoptosis, and metabolic regulation.

METHODS

In vitro, HT22 cells were exposed with heme (10 μmol/L, 12 h) to simulate ICH injury, followed by treatment with G-Rd and Chr (80 μmol/L). Reactive oxygen species (ROS), apoptosis, mitochondrial membrane potential, and inflammatory cytokines (TNF-α, IL-1β, IL-6, IL-10) were assessed using flow cytometry, fluorescence microscopy, and ELISA. In vivo, ICH was induced in rats via collagenase injection. Neurological function, hematoma volume, histopathology, and metabolic enzymes (SOD, MDA, NAD+, Ca2+-ATPase) were evaluated. Western blotting was used to analyze key enzymes in the serine-glycine-one‑carbon (SGOC) pathway.

RESULTS

G-Rd and Chr significantly suppressed ROS production (P < 0.05), downregulated pro-inflammatory cytokines (TNF-α, IL-1β, IL-6; P < 0.01), and inhibited apoptosis (P < 0.01) in HT22 cells. Both compounds restored mitochondrial membrane potential and alleviated cellular damage. In the ICH rat model, combined treatment improved neurological scores by 45 % (P < 0.01), decreased hematoma volume by 38 % (P < 0.01), and restored metabolic homeostasis through modulation of SGOC pathway enzymes (PHGDH, PSAT1, PSPH, SHMT2; P < 0.05). Synergistic effects were observed in both hematoma resolution and neuroprotection.

CONCLUSION

G-Rd and Chr confer neuroprotection in ICH through antioxidative, anti-inflammatory, anti-apoptotic, and metabolic regulatory mechanisms. Their synergistic efficacy underscores their promise as therapeutic candidates, meriting further investigation of their molecular targets and translational potential.

Dual Ribosome Profiling reveals metabolic limitations of cancer and stromal cells in the tumor microenvironment

The tumor microenvironment (TME) influences cancer cell metabolism and survival. However, how immune and stromal cells respond to metabolic stress in vivo, and how nutrient limitations affect therapy, remains poorly understood. Here, we introduce Dual Ribosome Profiling (DualRP) to simultaneously monitor translation and ribosome stalling in multiple tumor cell populations. DualRP reveals that cancer-fibroblast interactions trigger an inflammatory program that reduces amino acid shortages during glucose starvation. In immunocompetent mice, we show that serine and glycine are essential for optimal T cell function and that their deficiency impairs T cell fitness. Importantly, immune checkpoint blockade therapy imposes amino acid restrictions specifically in T cells, demonstrating that therapies create distinct metabolic demands across TME cell types. By mapping codon-resolved ribosome stalling in a cell‑type‑specific manner, DualRP uncovers metabolic crosstalk that shapes translational programs. DualRP thus offers a powerful, innovative approach for dissecting tumor cell metabolic interplay and guiding combined metabolic-immunotherapeutic strategies.

The crosstalk between glutathione metabolism and non-coding RNAs in cancer progression and treatment resistance

Excessive reactive oxygen species (ROS) are closely associated with the initiation and progression of cancers. As the most abundant intracellular antioxidant, glutathione (GSH) plays a critical role in regulating cellular ROS levels, modulating physiological processes, and is intricately linked to tumor progression and drug resistance. However, the underlying mechanisms remain not fully elucidated. Non-coding RNAs (ncRNAs), including long non-coding RNAs (lncRNAs) and microRNAs (miRNAs), are key regulators of GSH levels. Different ncRNAs modulate various pathways involved in GSH metabolism, and these regulatory targets have the potential to serve as therapeutic targets for enhancing cancer treatment. In this review, we summarize the functions of GSH metabolism and highlight the significance of ncRNA-mediated regulation of GSH in cancer progression, drug resistance, and clinical applications.

De novo serine biosynthesis is protective in mitochondrial disease

The importance of serine as a metabolic regulator is well known for tumors and is also gaining attention in degenerative diseases. Recent data indicate that de novo serine biosynthesis is an integral component of the metabolic response to mitochondrial disease, but the roles of the response have remained unknown. Here, we report that glucose-driven de novo serine biosynthesis maintains metabolic homeostasis in energetic stress. Pharmacological inhibition of the rate-limiting enzyme, phosphoglycerate dehydrogenase (PHGDH), aggravated mitochondrial muscle disease, suppressed oxidative phosphorylation and mitochondrial translation, altered whole-cell lipid profiles, and enhanced the mitochondrial integrated stress response (ISRmt) in vivo in skeletal muscle and in cultured cells. Our evidence indicates that de novo serine biosynthesis is essential to maintain mitochondrial respiration, redox balance, and cellular lipid homeostasis in skeletal muscle with mitochondrial dysfunction. Our evidence implies that interventions activating de novo serine synthesis may protect against mitochondrial failure in skeletal muscle.

Interplay between the gut microbiota, its metabolites and carcinogens

The gut microbiota is a complex and dynamic community of microorganisms that reside in the gastrointestinal tract, playing a critical role in the host. It produces many metabolites, such as bile acids, which play an important role in the metabolism of the host. One area of particular interest is its involvement in the development and treatment of cancer. Carcinogens, which are substances known to promote cancer formation and development, are present in various sources in our daily lives, including cigarettes, barbecues, and moldy foods. The types, amounts, and metabolism of carcinogens have been closely linked to cancer risk, underscoring the importance of understanding their interplay with the gut microbiota. Numerous studies have demonstrated significant differences in the composition and function of the gut microbiota in individuals with cancer compared to healthy individuals. The gut microbiota and its metabolites have been shown to influence the metabolism of various carcinogens, thereby affecting cancer progression. While much attention has been paid to the relationship between the gut microbiota and cancer risk, the potential interplay between the gut microbiota and carcinogens has received less focus. This review aims to emphasize the importance of exploring the interplay between the gut microbiota with its metabolites and carcinogens in cancer development and therapy. By uncovering the mechanisms of the interplay, new approaches for cancer prevention and treatment can be developed.

m6A/IGF2BP3-driven serine biosynthesis fuels AML stemness and metabolic vulnerability

Metabolic reprogramming of amino acids represents a vulnerability in cancer cells, yet the mechanisms underlying serine metabolism in acute myeloid leukemia (AML) and leukemia stem/initiating cells (LSCs/LICs) remain unclear. Here, we identify RNA N6-methyladenosine (m6A) modification as a key regulator of serine biosynthesis in AML. Using a CRISPR/Cas9 screen, we find that depletion of m6A regulators IGF2BP3 or METTL14 sensitizes AML cells to serine and glycine (SG) deprivation. IGF2BP3 recognizies m6A on mRNAs of key serine synthesis pathway (SSP) genes (e.g., ATF4, PHGDH, PSAT1), stabilizing these transcripts and sustaining serine production to meet the high metabolic demand of AML cells and LSCs/LICs. IGF2BP3 silencing combined with dietary SG restriction potently inhibits AML in vitro and in vivo, while its deletion spares normal hematopoiesis. Our findings reveal the critical role of m6A modification in the serine metabolic vulnerability of AML and highlight the IGF2BP3/m6A/SSP axis as a promising therapeutic target.

Online monitoring and stable isotope tracing of cancer associated volatiles in murine model captures tumor associated markers in vivo

BACKGROUND

The imperative need for early cancer detection, which is crucial for improved survival rates in many severe cancers such as lung cancer, remains challenging due to the lack of reliable early-diagnosis technologies and robust biomarkers. To address this gap, innovative screening platforms are essential to unveil the chemical signatures of lung cancer and its treatments. It is established that the oxidative tumor environment induces alterations in host metabolic processes and influences endogenous volatile synthesis. Despite efforts, consensus on unique volatile markers for cancer detection has been elusive, partly due to genetic variation leading to metabolic heterogeneity in humans and the lack of standardized procedures for analytical analyses.

RESULTS

In this study, we utilized advanced secondary electrospray ionization (SESI) technique coupled with a high-resolution mass spectrometer (HRMS) to non-invasively monitor lung cancer volatiles in a pre-clinical mouse model in real time. Our findings revealed 651 dysregulated volatile features upon cancer onset and identified 36 features correlated with tumor size. Endogenous tracing of glucose metabolism highlighted the γ-glutamyl cycle as a downstream pathway implicated in lung cancer, driven by an imbalance in glutathione metabolism due to reactive oxygen species (ROS) accumulation. Notably, our study unveiled unique volatile changes associated with gemcitabine and cisplatin treatment, which significantly abrogated tumor growth in vivo. Furthermore, we identified 5-oxoproline as a volatile metabolite indicative of lung cancer response to treatment.

SIGNIFICANCE

In conclusion, our SESI-HRMS based analysis of pre-clinical model systematically explores the volatile signatures of lung cancer, and provides a novel non-invasive platform that possess great potential for the real-time, confident, and sensitive detection and monitoring of lung cancer.

Hydroxymethyltransferase 2 promotes the development of glioblastoma by mediating WTAP regulation of PTEN N6-methyladenosine modification

Characterized by rapid proliferation and therapeutic resistance, glioblastoma (GBM) represents the deadliest primary CNS neoplasm, demonstrating a low survival rate and high mortality rate in patients. This is mainly related to the development of GBM more specifically due to the abnormal metabolism within cells. SHMT2 (serine hydroxymethyltransferase 2) acts as a pivotal metabolic regulator in neoplastic cells, driving one-carbon unit transfer essential for nucleotide biosynthesis. Here, we explored the mechanism of SHMT2 mediated GBM occurrence. In this study, SHMT2 expression was assessed in GBM cells and tissues. In vitro experiments were performed to investigate the functional role of SHMT2. The detailed mechanisms of SHMT2-mediated cell metabolism were addressed. Xenograft model analysis explored the influence of SHMT2 on GBM development. The expression level of SHMT2 in GBM clinical tissues and cell lines is higher than that in normal tissues. The downregulation of SHMT2 inhibits the proliferation ability and metabolic process of GBM cell lines. Mechanism dissection revealed that SHMT2 enhanced phosphatase and tensin homolog (PTEN) N6-methyladenosine (m6A) modification through the endogenous methyl donor SAM mediated by SHMT2 via serine/glycine one carbon metabolic networks. In addition, Xenograft model analysis showed that knockdown of SHMT2 inhibited the development of GBM tumors. SHMT2 promotes the tumorigenesis of glioblastoma by regulating the m6A modification of PTEN.

Halofuginone targets Serine/Glycine synthesis to reverse epidermal growth factor receptor Tyrosine Kinase inhibitor resistance in lung adenocarcinoma

BACKGROUND

An emerging issue is that patients are prone to become resistance to epidermal growth factor tyrosine kinase inhibitors (EGFR-TKIs) which are the first- line treatment for EGFR-mutated non-small cell lung cancer (NSCLC) after approximately 10 months of drug administration. Interestingly, metabolic dysregulation occurs simultaneously with acquired EGFR-TKI resistance in certain NSCLC cell lines.

PURPOSE

We aimed to investigate whether a natural product, halofuginone (HF), could overcome NSCLC resistance to EGFR-TKIs by influencing metabolism.

RESULTS

In our study, the combination of HF and EGFR-TKI exhibited synergistic cytotoxicity compared to EGFR-TKI monotherapy. The underlying mechanism is that HF promotes the degradation of SP1 protein and decreases the expression of phosphatidylserine transcarbamoylase 1 (PSAT1), which leads to defects in the de novo synthesis of Serine/Glycine and cell death.

CONCLUSIONS

HF is a promising natural product for overcoming NSCLC resistance to third-generation epidermal growth factor receptors-TKIs.

Loss of NOL10 leads to impaired disease progression of NUP98::DDX10 leukemia

NUP98 rearrangements associated with acute myeloid leukemia and myelodysplastic syndromes generate NUP98-fusion proteins. One such fusion protein, NUP98::DDX10, contains the putative RNA helicase DDX10. The molecular mechanism by which NUP98::DDX10 induces leukemia is not well understood. Here, we show that 24 amino acids within the DDX10 moiety of NUP98::DDX10 are crucial for cell immortalization and leukemogenesis. NOL10, nucleolar protein 10, interacts with the 24 amino acids, and NOL10 is a critical dependency of NUP98::DDX10 leukemia development. Studies in a mouse model of NUP98::DDX10 leukemia showed that loss of Nol10 impaired disease progression and improved survival. We also identified a novel function of NOL10 in that it acts cooperatively with NUP98::DDX10 to regulate serine biosynthesis pathways and stabilize ATF4 mRNA. Collectively, these findings suggest that NOL10 is a critical regulator of NUP98::DDX10 leukemia and that targeting NOL10 (or the serine synthesis pathway regulated by NOL10) may be an effective therapeutic approach.

Immunogenic Cell Death and Metabolic Reprogramming in Cancer: Mechanisms, Synergies, and Innovative Therapeutic Strategies

Immunogenic cell death (ICD) is a promising cancer therapy where dying tumor cells release damage-associated molecular patterns (DAMPs) to activate immune responses. Recent research highlights the critical role of metabolic reprogramming in tumor cells, including the Warburg effect, oxidative stress, and lipid metabolism, in modulating ICD and shaping the immune microenvironment. These metabolic changes enhance immune activation, making tumors more susceptible to immune surveillance. This review explores the molecular mechanisms linking ICD and metabolism, including mitochondrial oxidative stress, endoplasmic reticulum (ER) stress, and ferroptosis. It also discusses innovative therapeutic strategies, such as personalized combination therapies, metabolic inhibitors, and targeted delivery systems, to improve ICD efficacy. The future of cancer immunotherapy lies in integrating metabolic reprogramming and immune activation to overcome tumor immune evasion, with multi-omics approaches and microbiome modulation offering new avenues for enhanced treatment outcomes.

The role and research progress of serine metabolism in tumor cells

Serine is crucial for tumor initiation, progression, and adaptive immunity. Metabolic pathways for serine synthesis, acquisition, and utilization in tumors and tumor-associated cells are influenced by various physiological factors and the tumor microenvironment, leading to metabolic reprogramming and amplification. Excessive serine metabolism promotes abnormal macromolecule biosynthesis, mitochondrial dysfunction, and epigenetic modifications, driving malignant transformation, proliferation, metastasis, immune suppression, and drug resistance in tumor cells. Restricting dietary serine intake or reducing the expression of serine synthetic enzymes can effectively slow tumor growth and extend patient survival. Consequently, targeting serine metabolism has emerged as a novel and promising research focus in cancer research. This paper reviews serine metabolic pathways and their roles in tumor development. It summarizes the influencing factors of serine metabolism. The article explores the significance of serine synthesis and metabolizing enzymes, along with related biomarkers, in tumor diagnosis and treatment, providing new insights for developing targeted therapies that modulate serine metabolism in cancer.

Unveiling the crossroads of STING signaling pathway and metabolic reprogramming: the multifaceted role of the STING in the TME and new prospects in cancer therapies

The cGAS-STING signaling pathway serves as a critical link between DNA sensing and innate immunity, and has tremendous potential to improve anti-tumor immunity by generating type I interferons. However, STING agonists have shown decreasing biotherapeutic efficacy in clinical trials. Tumor metabolism, characterized by aberrant nutrient utilization and energy production, is a fundamental hallmark of tumorigenesis. And modulating metabolic pathways in tumor cells has been discovered as a therapeutic strategy for tumors. As research concerning STING progressed, emerging evidence highlights its role in metabolic reprogramming, independent its immune function, indicating metabolic targets as a strategy for STING activation in cancers. In this review, we delve into the interplay between STING and multiple metabolic pathways. We also synthesize current knowledge on the antitumor functions of STING, and the metabolic targets within the tumor microenvironment (TME) that could be exploited for STING activation. This review highlights the necessity for future research to dissect the complex metabolic interactions with STING in various cancer types, emphasizing the potential for personalized therapeutic strategies based on metabolic profiling.

The landscape of ATF3 in tumors: Metabolism, expression regulation, therapy approach, and open concerns

Cellular stress response is a pivotal process in tumor development and therapy. Activating transcription factor 3 (ATF3), a representative stress-responsive protein, plays pleiotropic roles in various biological processes. Over the past decade, studies have described not only the general role of ATF3 in tumor metabolism but also the complexity of ATF3 expression regulation and its associated modifications, including phosphorylation, ubiquitination, SUMOylation, and NEDDylation. Interestingly, beyond being a transcription factor, ATF3 can act as a modifier to control the ubiquitination of target molecules, such as p53, to exert its function in tumors. These advances in uncovering ATF3 biological function have yielded new insights into the cellular stress response during tumor development and will be instrumental in developing novel interventions. In this review, we update the role of ATF3 as a nexus in amino acid metabolism, lipid metabolism, glycometabolism, and other metabolic pathways in tumors; delineate the underlying mechanisms involving DNA level regulation, epigenetic regulation, and post-translational modifications of ATF3; and summarize the progression of tumor mono/combination therapies related to ATF3. In particular, we discuss the challenges that need to be addressed to provide a new conceptual framework for further understanding the potential therapeutic value of ATF3 in ongoing clinical trials.

PHGDH activation fuels glioblastoma progression and radioresistance via serine synthesis pathway

BACKGROUND

Glioma stem-like cells (GSCs) are key drivers of treatment resistance and recurrence in glioblastoma (GBM). Phosphoglycerate dehydrogenase (PHGDH), a crucial enzyme in the de novo serine synthesis pathway (SSP), is implicated in tumorigenesis and therapy resistance across various cancers. However, its specific role in GBM, particularly in radioresistance, remains poorly understood.

METHODS

In silico analysis of GBM patient data assessed SSP enrichment and PHGDH expression linked with tumor stemness. Comparative gene expression analysis focused on PHGDH in paired GBM specimens and GSCs. Genetic and pharmacological loss-of-function assays were performed in vitro and in vivo to evaluate PHGDH's impact on GSC self-renewal and malignant progression. Comprehensive transcriptomic and metabolomic analyses, along with chromatin immunoprecipitation, mass spectrometry, and various other biochemical assays, were used to elucidate PHGDH-mediated mechanisms in GBM progression and radioresistance.

RESULTS

PHGDH expression is significantly elevated in GSCs, associated with aggressive glioma progression and poor clinical outcomes. PHGDH activation enhances GSC self-renewal by regulating redox homeostasis, facilitating one-carbon metabolism, and promoting DNA damage response via SSP activation. Importantly, MYC was identified as a crucial transcriptional regulator of PHGDH expression. Furthermore, genetic ablation or pharmacological inhibition of PHGDH markedly reduced tumor growth and increased tumor sensitivity to radiotherapy, thereby improving survival outcomes in orthotopic GSC-derived and patient-derived GBM xenograft models.

CONCLUSIONS

This study underscores the pivotal role of MYC-mediated PHGDH activation in driving GSC malignant progression and radioresistance in GBM. Targeting PHGDH presents a promising approach to enhance radiotherapy efficacy in GBM patients.

Neuron-Specific Glycine Metabolism Links Transfer RNA Epitranscriptomic Regulation to Complex Behaviors

Background

The presence of treatment resistance in neuropsychiatric disease suggests that novel mechanism-based discoveries and therapies could benefit the field, with a viable candidate being transfer RNA (tRNA) epitranscriptomics. Nsun2 tRNA methyltransferase depletion in mature neurons elicits changes in complex behaviors relevant for fear, anxiety, and other neuropsychiatric phenotypes. However, it remains unclear whether this is due to dysregulated tRNAs or metabolic shifts that impact the neuronal translatome by activation of stress messengers together with alterations in amino acid supply.

Methods

To link specific molecular alterations resulting from neuronal Nsun2 ablation to neuropsychiatric phenotypes, we used drug-induced phosphoactivation of stress response translation initiation factors together with disruption of NSUN2-regulated glycine tRNAs and cell type-specific ablation of the glycine cleavage system modeling the excessive upregulation of this amino acid in the Nsun2-deficient brain. Changes in extracellular glycine levels were monitored by an optical glycine Förster resonance energy transfer (FRET) sensor in the hippocampus, and behavioral phenotyping included cognition, anxiety-like behavior, and behavioral despair.

Results

Increased motivated escape behaviors were specifically observed in mice with neuron-specific ablation of Gldc, resulting in an excess in cortical glycine levels comparable to a similar phenotype in mice after deletion of neuronal Nsun2. None of these phenotypes were observed in mice treated with tunicamycin for chemoactivation of integrative stress response pathways or in mice genetically engineered for decreased glycine tRNA gene dosage. In the Nsun2-deficient brain, dynamic glycine profiles in the hippocampal extracellular space were fully maintained at baseline and in the context of neuronal activity.

Conclusions

Alterations in neuronal glycine metabolism, resulting from targeted ablation of the glycine cleavage system or disruption of the tRNA regulome, elicit changes in complex behaviors in mice relevant for neuropsychiatric phenotypes.

Network pharmacology alliance with experimental validation unveils the anti-colorectal cancer mechanism of Xianlian Jiedu decoction

ETHNOPHARMACOLOGICAL RELEVANCE

The Xianlian Jiedu Decoction (XLJDD), a traditional Chinese medicine (TCM) decoction, which is effective in clinical treatment of colorectal cancer (CRC). Nevertheless, the pharmacodynamic material basis and mechanism of its action have not been explored yet.

AIMS OF THE STUDY

To investigate the potential functional components and possible mechanism of XLJDD in anti-CRC.

MATERIALS AND METHODS

The UPLC-Q-TOF-MS method was applied to the qualification of absorbed phytochemical compounds in the plasma of rats administrated with XLJDD. Network pharmacology approach was used to create the compound-target network, GO and KEGG enrichment resolution was used to predict the potential biological mechanism of XLJDD anti-CRC. The binding of potential active ingredients to their targets was demonstrated using AutoDock Tools. And the anti-CRC efficacy of XLJDD was investigated through in vitro and in vivo experiments. Furthermore, the mechanism of XLJDD anti-CRC was validated by Western blot.

RESULTS

14 compounds from XLJDD were detected in the plasma of rats administrated with XLJDD. The results of network pharmacology analysis shown that PI3K/AKT and chemokine signaling pathways were strongly linked to XLJDD against CRC. The potential active compounds berberine, 7-methoxycoumarin and 13-methylberberubine may target PRKACA, PIK3CB, and EGFR to regulate PI3K/AKT signaling pathway, which plays a crucial role in cancer cell proliferation. In vitro experimental results revealed that XLJDD apparently inhibits the cell viability and proliferation of HCT116 cells. In vivo experimental results found that in contrast to the model group, the XLJDD treatment obviously cut down the size and weight of tumor. Further, Western blot results demonstrated that XLJDD significantly inhibited the CXCR2/PI3K/AKT signaling axis.

CONCLUSION

The therapeutic mechanism of XLJDD against CRC involves inhibiting CRC cells proliferation via modulating the CXCR2/PI3K/AKT signaling pathway.

Emerging insights into the impact of systemic metabolic changes on tumor-immune interactions

Tumors are inherently embedded in systemic physiology, which contributes metabolites, signaling molecules, and immune cells to the tumor microenvironment. As a result, any systemic change to host metabolism can impact tumor progression and response to therapy. In this review, we explore how factors that affect metabolic health, such as diet, obesity, and exercise, influence the interplay between cancer and immune cells that reside within tumors. We also examine how metabolic diseases influence cancer progression, metastasis, and treatment. Finally, we consider how metabolic interventions can be deployed to improve immunotherapy. The overall goal is to highlight how metabolic heterogeneity in the human population shapes the immune response to cancer.

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.

PHGDH Induction by MAPK Is Essential for Melanoma Formation and Creates an Actionable Metabolic Vulnerability

Overexpression of phosphoglycerate dehydrogenase (PHGDH), the rate-limiting enzyme in the serine synthesis pathway, promotes melanomagenesis, melanoma cell proliferation, and survival of metastases in serine-low environments such as the brain. Here, we found that PHGDH is universally increased in melanoma cells and required for melanomagenesis. Although PHGDH amplification explained PHGDH overexpression in a subset of melanomas, oncogenic BRAFV600E also promoted PHGDH transcription through mTORC1-mediated translation of ATF4. Importantly, depletion of PHGDH in genetic mouse melanoma models blocked tumor formation. In addition to BRAFV600E-mediated upregulation, PHGDH was further induced by exogenous serine restriction. Surprisingly, BRAFV600E inhibition diminished serine restriction-mediated PHGDH expression by preventing ATF4 induction. Consequently, melanoma cells could be specifically starved of serine by combining BRAFV600E inhibition with exogenous serine restriction, which promoted cell death in vitro and attenuated melanoma growth in vivo. In summary, this study identified that PHGDH is essential for melanomagenesis and regulated by BRAFV600E, revealing a targetable vulnerability in BRAFV600E-mutant melanoma. Significance: BRAFV600E promotes the expression of the serine synthesis enzyme PHGDH, which is required for melanoma formation, and can be targeted to sensitize melanoma to dietary serine restriction, providing a melanoma cell-specific treatment strategy.

MYC-dependent upregulation of the de novo serine and glycine synthesis pathway is a targetable metabolic vulnerability in group 3 medulloblastoma

BACKGROUND

Group 3 medulloblastoma (MBGRP3) represents around 25% of medulloblastomas and is strongly associated with c-MYC (MYC) amplification, which confers significantly worse patient survival. Although elevated MYC expression is a significant molecular feature in MBGRP3, direct targeting of MYC remains elusive, and alternative strategies are needed. The metabolic landscape of MYC-driven MBGRP3 is largely unexplored and may offer novel opportunities for therapies.

METHODS

To study MYC-induced metabolic alterations in MBGRP3, we depleted MYC in isogenic cell-based model systems, followed by 1H high-resolution magic-angle spectroscopy (HRMAS) and stable isotope-resolved metabolomics, to assess changes in intracellular metabolites and pathway dynamics.

RESULTS

Steady-state metabolic profiling revealed consistent MYC-dependent alterations in metabolites involved in one-carbon metabolism such as glycine. 13C-glucose tracing further revealed a reduction in glucose-derived serine and glycine (de novo synthesis) following MYC knockdown, which coincided with lower expression and activity of phosphoglycerate dehydrogenase (PHGDH), the rate-limiting enzyme in this pathway. Furthermore, MYC-overexpressing MBGRP3 cells were more vulnerable to pharmacological inhibition of PHGDH compared to those with low expression. Using in vivo tumor-bearing genetically engineered and xenograft mouse models, pharmacological inhibition of PHGDH increased survival, implicating the de novo serine/glycine synthesis pathway as a pro-survival mechanism sustaining tumor progression. Critically, in primary human medulloblastomas, increased PHGDH expression correlated strongly with both MYC amplification and poorer clinical outcomes.

CONCLUSIONS

Our findings support a MYC-induced dependency on the serine/glycine pathway in MBGRP3 that represents a novel therapeutic treatment strategy for this poor prognosis disease group.

FOXC1-mediated serine metabolism reprogramming enhances colorectal cancer growth and 5-FU resistance under serine restriction

Colorectal cancer (CRC) is the most common gastrointestinal malignancy, and 5-Fluorouracil (5-FU) is the principal chemotherapeutic drug used for its treatment. However, 5-FU resistance remains a significant challenge. Under stress conditions, tumor metabolic reprogramming influences 5-FU resistance. Serine metabolism plasticity is one of the crucial metabolic pathways influencing 5-FU resistance in CRC. However, the mechanisms by which CRC modulates serine metabolic reprogramming under serine-deprived conditions remain unknown. We found that exogenous serine deprivation enhanced the expression of serine synthesis pathway (SSP) genes, which in turn supported CRC cell growth and 5-FU resistance. Serine deprivation activate the ERK1/2-p-ELK1 signaling axis, leading to upregulated FOXC1 expression in CRC cells. Elevated FOXC1 emerged as a critical element, promoting the transcription of serine metabolism enzymes PHGDH, PSAT1, and PSPH, which in turn facilitated serine production, supporting CRC growth. Furthermore, through serine metabolism, FOXC1 influenced purine metabolism and DNA damage repair, thereby increasing 5-FU resistance. Consequently, combining dietary serine restriction with targeted therapy against the ERK1/2-pELK1-FOXC1 axis could be a highly effective strategy for treating CRC, enhancing the efficacy of 5-FU.

Possible Metabolic Remodeling based on de novo Biosynthesis of L-serine in Se-Subtoxic or -Deficient Mammals

Current research studies point to an increased risk of diabetes with selenium (Se) intake beyond the physiological requirement used to prevent cancers. The existing hypothesis of "selenoprotein overexpression leads to intracellular redox imbalance" cannot clearly explain the U-shaped dose-effect relationship between Se intake and the risk of diabetes. In this review, it is speculated that metabolic remodeling based on the de novo biosynthesis of L-serine may occur in mammals at supranutritional or subtoxic levels of Se. It is also speculated that a large amount of L-serine is consumed by the body during insufficient Se intake, thus resulting in similar metabolic reprogramming. The increase in atypical ceramide and its derivatives due to the lack of L-serine may also play a role in the development of diabetes.

Limiting serine availability during tumor progression promotes muscle wasting in cancer cachexia

Cancer cachexia is a multifactorial syndrome characterized by a progressive loss of body weight occurring in about 80% of cancer patients, frequently representing the leading cause of death. Dietary intervention is emerging as a promising therapeutic strategy to counteract cancer-induced wasting. Serine is the second most-consumed amino acid (AA) by cancer cells and has emerged to be strictly necessary to preserve skeletal muscle structure and functionality. Here, we demonstrate that decreased serine availability during tumor progression promotes myotubes diameter reduction in vitro and induces muscle wasting in in vivo mice models. By investigating the metabolic crosstalk between colorectal cancer cells and muscle cells, we found that incubating myotubes with conditioned media from tumor cells relying on exogenous serine consumption triggers pronounced myotubes diameter reduction. Accordingly, culturing myotubes in a serine-free medium induces fibers width reduction and suppresses the activation of the AKT-mTORC1 pathway with consequent impairment in protein synthesis, increased protein degradation, and enhanced expression of the muscle atrophy-related genes Atrogin1 and MuRF1. In addition, serine-starved conditions affect myoblast differentiation and mitochondrial oxidative metabolism, finally inducing oxidative stress in myotubes. Consistently, serine dietary deprivation strongly strengthens cancer-associated weight loss and muscle atrophy in mice models. These findings uncover serine consumption by tumor cells as a previously undisclosed driver in cancer cachexia, opening new routes for possible therapeutic approaches.

Redox homeostasis of one-carbon metabolism-dependent reprogramming is critical for RCC progression under exogenous serine/glycine-deprived conditions

BACKGROUND

Serine/glycine are critical for the growth and survival of cancer cells. Some cancer cells are more dependent on exogenous serine/glycine than endogenously synthesized serine/glycine. However, the function and underlying mechanisms of exogenous serine/glycine in renal cell carcinoma (RCC) remain unclear.

METHODS

We conducted a comprehensive assessment of RCC progression under conditions of exogenous serine/glycine deprivation and explored the underlying mechanism via immunofluorescence, autophagic flux analysis, extracellular acidification rate (ECAR) and oxygen consumption rate (OCR) measurements.

RESULTS

The expression of the serine synthesis pathway enzymes was decreased in RCC specimens, the de novo serine synthesis pathway (SSP) was reduced in RCC. And the levels of endogenously synthesized serine/glycine were little. Yet, the exogenous serine/glycine deprivation significantly inhibited the growth of RCC cells both in vitro and in vivo, indicating that exogenous serine/glycine were important for RCC progression. Mechanistically, the deprivation of exogenous serine/glycine disrupted one-carbon metabolism and increased the ratio of NAD(P)+/NAD(P)H, resulting in the accumulation of reactive oxygen species (ROS) and oxidative stress, which induced autophagic flux and enhanced lysosome membrane permeabilization (LMP), leading to the release of lysosomal cathepsins into the cytoplasm, which ultimately triggered lysosomal dependent cell death (LDCD) and inhibited the progression of RCC.

CONCLUSIONS

Our results indicate that exogenous serine/glycine are critical for RCC progression by maintaining one-carbon metabolism-dependent redox homeostasis, which provides new insights for the development of dietary serine/glycine starvation-based therapeutic approaches for RCC.

Serine related gene CCT6A promotes metastasis of hepatocellular carcinoma via interacting with RPS3

Metastasis is responsible for approximately 90% of lethality from solid tumors. Metabolic abnormalities are one of the key characteristics of tumor cells, closely associated with tumorigenesis and progression. The de novo synthesis pathway of serine is a key metabolic bypass in glycolysis, which could provide material and energy basis for the rapid proliferation of tumor cells by mediating one-carbon metabolism. The transformation of metabolic patterns is particularly pronounced in HCC, often leading to a high dependence of HCC cells on glycolysis. However, up to now, the underlying relationship between serine metabolism and HCC metastasis remains largely unknown. Through a series of bioinformatics methods, we reported CCT6A, a serine related gene, was particularly associated with metastatic events of HCC. We furtherly demonstrated that CCT6A was highly expressed in HCC cells with high metastatic potential. Gain- and loss-of-function analyses showed that CCT6A could promote HCC cells migration and invasion. Mechanistically, CCT6A was found to be interacted with RPS3, and might potentiate the metastasis of HCC by affecting some metabolic processes. Totally, our results suggest that the metabolic reprogramming induced by interacting between CCT6A and RPS3 could advance HCC metastasis, making the CCT6A/RPS3 axis a promising target for therapeutic intervention.

Loss of USP10 promotes hepatocellular carcinoma proliferation by regulating the serine synthesis pathway through inhibition of LKB1 activity

Metabolic dysregulation is emerging as a critical factor in tumorigenesis, and reprogramming of serine metabolism has been identified as an essential factor in the progression of hepatocellular carcinoma (HCC). Studies have shown that LKB1 deficiency can activate mTOR to upregulate the serine synthesis pathway (SSP) and promote tumor progression. Our team discovered that ubiquitin-specific protease 10 (USP10) can inhibit HCC proliferation through mTOR, but its relationship with SSP needs further investigation. The metabolite assays revealed a significant increase in serine content in HCC tissues. Through the LKB1/mTOR/activating transcription factor 4 (ATF4) axis, loss of USP10 may increase serine biosynthesis and promote the proliferation of HCC in vitro and in vivo. Furthermore, it was found that USP10 could activate LKB1 through deubiquitination. Analyzing clinical HCC tissues revealed a positive correlation between USP10 and LKB1. Additionally, those with high expression of USP10 in HCC tissues showed a better degree of tumor differentiation and longer overall survival time. Moreover, we found increased expression of both serine and its synthase in liver tumor tissues of USP10 liver-specific KO mice. Loss of USP10 inhibits the activity of LKB1, contributing to the stimulation of the mTOR/ATF4 axis and SSP and then promoting the proliferation of HCC. This work presents a novel approach for serine-targeted treatment in HCC.

Advancing Anticancer Drug Discovery: Leveraging Metabolomics and Machine Learning for Mode of Action Prediction by Pattern Recognition

A bottleneck in the development of new anti-cancer drugs is the recognition of their mode of action (MoA). Metabolomics combined with machine learning allowed to predict MoAs of novel anti-proliferative drug candidates, focusing on human prostate cancer cells (PC-3). As proof of concept, 38 drugs are studied with known effects on 16 key processes of cancer metabolism, profiling low molecular weight intermediates of the central carbon and cellular energy metabolism (CCEM) by LC-MS/MS. These metabolic patterns unveiled distinct MoAs, enabling accurate MoA predictions for novel agents by machine learning. The transferability of MoA predictions based on PC-3 cell treatments is validated with two other cancer cell models, i.e., breast cancer and Ewing's sarcoma, and show that correct MoA predictions for alternative cancer cells are possible, but still at some expense of prediction quality. Furthermore, metabolic profiles of treated cells yield insights into intracellular processes, exemplified for drugs inducing different types of mitochondrial dysfunction. Specifically, it is predicted that pentacyclic triterpenes inhibit oxidative phosphorylation and affect phospholipid biosynthesis, as confirmed by respiration parameters, lipidomics, and molecular docking. Using biochemical insights from individual drug treatments, this approach offers new opportunities, including the optimization of combinatorial drug applications.

Lactylation-Driven IGF2BP3-Mediated Serine Metabolism Reprogramming and RNA m6A-Modification Promotes Lenvatinib Resistance in HCC

Acquired resistance remains a bottleneck for molecular-targeted therapy in advanced hepatocellular carcinoma (HCC). Metabolic adaptation and epigenetic remodeling are recognized as hallmarks of cancer that may contribute to acquired resistance. In various lenvatinib-resistant models, increased glycolysis leads to lactate accumulation and lysine lactylation of IGF2BP3. This lactylation is crucial for capturing PCK2 and NRF2 mRNAs, thereby enhancing their expression. This process reprograms serine metabolism and strengthens the antioxidant defense system. Additionally, altered serine metabolism increases the availability of methylated substrates, such as S-adenosylmethionine (SAM), for N6-methyladenosine (m6A) methylation of PCK2 and NRF2 mRNAs. The lactylated IGF2BP3-PCK2-SAM-m6A loop maintains elevated PCK2 and NRF2 levels, enhancing the antioxidant system and promoting lenvatinib resistance in HCC. Treatment with liposomes carrying siRNAs targeting IGF2BP3 or the glycolysis inhibitor 2-DG restored lenvatinib sensitivity in vivo. These findings highlight the connection between metabolic reprogramming and epigenetic regulation and suggest that targeting metabolic pathways may offer new strategies to overcome lenvatinib resistance in HCC.

Nanomaterial-based regulation of redox metabolism for enhancing cancer therapy

Altered redox metabolism is one of the hallmarks of tumor cells, which not only contributes to tumor proliferation, metastasis, and immune evasion, but also has great relevance to therapeutic resistance. Therefore, regulation of redox metabolism of tumor cells has been proposed as an attractive therapeutic strategy to inhibit tumor growth and reverse therapeutic resistance. In this respect, nanomedicines have exhibited significant therapeutic advantages as intensively reported in recent studies. In this review, we would like to summarize the latest advances in nanomaterial-assisted strategies for redox metabolic regulation therapy, with a focus on the regulation of redox metabolism-related metabolite levels, enzyme activity, and signaling pathways. In the end, future expectations and challenges of such emerging strategies have been discussed, hoping to enlighten and promote their further development for meeting the various demands of advanced cancer therapies. It is highly expected that these therapeutic strategies based on redox metabolism regulation will play a more important role in the field of nanomedicine.

Physical performance and plasma metabolic profile as potential prognostic factors in metastatic lung cancer patients

BACKGROUND

Low physical performance is associated with higher mortality rate in multiple pathological conditions. Here, we aimed to determine whether body composition and physical performance could be prognostic factors in non-small cell lung cancer (NSCLC) patients. Moreover, we performed an exploratory approach to determine whether plasma samples from NSCLC patients could directly affect metabolic and structural phenotypes in primary muscle cells.

METHODS

This prospective cohort study included 55 metastatic NSCLC patients and seven age-matched control subjects. Assessments included physical performance, body composition, quality of life and overall survival rate. Plasma samples from a sub cohort of 18 patients were collected for exploratory studies in cell culture and metabolomic analysis.

RESULTS

We observed a higher survival rate in NSCLC patients with high performance in the timed up-and-go (+320%; p = .007), sit-to-stand (+256%; p = .01) and six-minute walking (+323%; p = .002) tests when compared to NSCLC patients with low physical performance. There was no significant association for similar analysis with body composition measurements (p > .05). Primary human myotubes incubated with plasma from NSCLC patients with low physical performance had impaired oxygen consumption rate (-54.2%; p < .0001) and cell proliferation (-44.9%; p = .007). An unbiased metabolomic analysis revealed a list of specific metabolites differentially expressed in the plasma of NSCLC patients with low physical performance.

CONCLUSION

These novel findings indicate that physical performance is a prognostic factor for overall survival in NSCLC patients and provide novel insights into circulating factors that could impair skeletal muscle metabolism.

Asparagine as a signal for glutamine sufficiency via asparagine synthetase: a fresh evidence-based framework in physiology and oncology

Among the 20 proteinogenic amino acids, glutamine (GLN) and asparagine (ASN) represent a unique cohort in containing a terminal amide in their side chain, and share a direct metabolic relationship, with glutamine generating asparagine through the ATP-dependent asparagine synthetase (ASNS) reaction. Circulating glutamine levels and metabolic flux through cells and tissues greatly exceed those for asparagine, and "glutamine addiction" in cancer has likewise received considerable attention. However, historic and recent evidence collectively suggest that in spite of its modest presence, asparagine plays an outsized regulatory role in cellular function. Here, we present a unifying evidence-based hypothesis that the amides constitute a regulatory signaling circuit, with glutamine as a driver and asparagine as a second messenger that allosterically regulates key biochemical and physiological functions, particularly cell growth and survival. Specifically, it is proposed that ASNS serves as a sensor of substrate sufficiency for S-phase entry and progression in proliferating cells. ASNS-generated asparagine serves as a subsequent second messenger that modulates the activity of key regulatory proteins and promotes survival in the face of cellular stress, and serves as a feed-forward driver of S-phase progression in cell growth. We propose that this signaling pathway be termed the amide signaling circuit (ASC) in homage to the SLC1A5-encoded ASCT2 that transports both glutamine and asparagine in a bidirectional manner, and has been implicated in the pathogenesis of a broad spectrum of human cancers. Support for the ASC model is provided by the recent discovery that glutamine is sensed in primary cilia via ASNS during metabolic stress.

Hypoxia-induced SHMT2 protein lactylation facilitates glycolysis and stemness of esophageal cancer cells

Esophageal cancer (EC) is a familiar digestive tract tumor with highly lethal. The hypoxic environment has been demonstrated to be a significant factor in modulating malignant tumor progression and is strongly associated with the abnormal energy metabolism of tumor cells. Serine hydroxymethyl transferase 2 (SHMT2) is one of the most frequently expressed metabolic enzymes in human malignancies. The study was designed to investigate the biological functions and regulation mechanisms of SHMT2 in EC under hypoxia. We conducted RT-qPCR to assess SHMT2 levels in EC tissues and cells (TE-1 and EC109). EC cells were incubated under normoxia and hypoxia, respectively, and altered SHMT2 expression was evaluated through RT-qPCR, western blot, and immunofluorescence. The biological functions of SHMT2 on EC cells were monitored by performing CCK-8, EdU, transwell, sphere formation, glucose uptake, and lactate production assays. The SHMT2 protein lactylation was measured by immunoprecipitation and western blot. In addition, SHMT2-interacting proteins were analyzed by bioinformatics and validated by rescue experiments. SHMT2 was notably upregulated in EC tissues and cells. Hypoxia elevated SHMT2 protein expression, augmenting EC cell proliferation, migration, invasion, stemness, and glycolysis. In addition, hypoxia triggered lactylation of the SHMT2 protein and enhanced its stability. SHMT2 knockdown impeded the malignant phenotype of EC cells. Further mechanistic studies disclosed that SHMT2 is involved in EC progression by interacting with MTHFD1L. Hypoxia-induced SHMT2 protein lactylation and upregulated its protein level, which in turn enhanced MTHFD1L expression and accelerated the malignant progression of EC cells.

A metabolic crosstalk between liposarcoma and muscle sustains tumor growth

Dedifferentiated and Well-differentiated liposarcoma are characterized by a systematic amplification of the Murine Double Minute 2 (MDM2) oncogene. We demonstrate that p53-independent metabolic functions of chromatin-bound MDM2 are exacerbated in liposarcoma and mediate an addiction to serine metabolism to sustain tumor growth. However, the origin of exogenous serine remains unclear. Here, we show that elevated serine levels in mice harboring liposarcoma-patient derived xenograft, released by distant muscle is essential for liposarcoma cell survival. Repressing interleukine-6 expression, or treating liposarcoma cells with Food and Drugs Administration (FDA) approved anti-interleukine-6 monoclonal antibody, decreases de novo serine synthesis in muscle, impairs proliferation, and increases cell death in vitro and in vivo. This work reveals a metabolic crosstalk between muscle and liposarcoma tumor and identifies anti-interleukine-6 as a plausible treatment for liposarcoma patients.

E-Cadherin Induces Serine Synthesis to Support Progression and Metastasis of Breast Cancer

The loss of E-cadherin, an epithelial cell adhesion molecule, has been implicated in metastasis by mediating the epithelial-mesenchymal transition, which promotes invasion and migration of cancer cells. However, recent studies have demonstrated that E-cadherin supports the survival and proliferation of metastatic cancer cells. Here, we identified a metabolic role for E-cadherin in breast cancer by upregulating the de novo serine synthesis pathway (SSP). The upregulated SSP provided metabolic precursors for biosynthesis and resistance to oxidative stress, enabling E-cadherin+ breast cancer cells to achieve faster tumor growth and enhanced metastases. Inhibition of phosphoglycerate dehydrogenase, a rate-limiting enzyme in the SSP, significantly and specifically hampered proliferation of E-cadherin+ breast cancer cells and rendered them vulnerable to oxidative stress, inhibiting their metastatic potential. These findings reveal that E-cadherin reprograms cellular metabolism, promoting tumor growth and metastasis of breast cancers. Significance: E-Cadherin promotes the progression and metastasis of breast cancer by upregulating the de novo serine synthesis pathway, offering promising targets for inhibiting tumor growth and metastasis in E-cadherin-expressing tumors.

Knockdown of ERN1 disturbs the expression of phosphoserine aminotransferase 1 and related genes in glioblastoma cells

BACKGROUND

Endoplasmic reticulum stress and synthesis of serine are essential for tumor growth, but the mechanism of their interaction is not clarified yet. The overarching goal of this work was to investigate the impact of ERN1 (endoplasmic reticulum to nucleus signaling 1) inhibition on the expression of serine synthesis genes in U87MG glioblastoma cells concerning the suppression of cell proliferation.

METHODS

Wild type U87MG glioblastoma cells and their clones with overexpression of transgenes dnERN1 (without cytoplasmic domain of ERN1) and dnrERN1 (with mutation in endoribonuclease of ERN1), and empty vector (as control) were used. The silencing of ERN1 and XBP1 was also used to inhibition of ERN1 and its function. Gene expression was measured by qPCR.

RESULTS

We show that the expression of PSAT1 and several other related to serine synthesis genes is suppressed in cells with ERN1 inhibition by dissimilar mechanisms: PHGDH gene through ERN1 protein kinase, because its expression was resistant to inhibition of ERN1 endoribonuclease, but ATF4 gene via endoribonuclease of ERN1. However, in the control of PSAT1 and PSPH genes both enzymatic activities of ERN1 signaling protein are involved. At the same time, ERN1 knockdown strongly increased SHMT1 expression, which controls serine metabolism and enhances the proliferation and invasiveness of glioma cells. The level of microRNAs, which have binding sites in PSAT1, SHMT1, and PSPH mRNAs, was also changed in cells harboring dnERN1 transgene. Inhibition of ERN1 suppressed cell proliferation and enzymatic activity of PHGDH, a rate-limiting enzyme for serine synthesis.

CONCLUSION

Changes in the expression of phosphoserine aminotransferase 1 and other genes related to serine synthesis are mediated by diverse ERN1-dependent mechanisms and contributed to suppressed proliferation and enhanced invasiveness of ERN1 knockdown glioblastoma cell.

Enzymes of sphingolipid metabolism as transducers of metabolic inputs

Sphingolipids (SLs) constitute a discrete subdomain of metabolism, and they display both structural and signaling functions. Accumulating evidence also points to intimate connections between intermediary metabolism and SL metabolism. Given that many SLs exhibit bioactive properties (i.e. transduce signals), these raise the possibility that an important function of SLs is to relay information on metabolic changes into specific cell responses. This could occur at various levels. Some metabolites are incorporated into SLs, whereas others may initiate regulatory or signaling events that, in turn, modulate SL metabolism. In this review, we elaborate on the former as it represents a poorly appreciated aspect of SL metabolism, and we develop the hypothesis that the SL network is highly sensitive to several specific metabolic changes, focusing on amino acids (serine and alanine), various fatty acids, choline (and ethanolamine), and glucose.

ASCT2 is a major contributor to serine uptake in cancer cells

The non-essential amino acid serine is a critical nutrient for cancer cells due to its diverse biosynthetic functions. While some tumors can synthesize serine de novo, others are auxotrophic and therefore reliant on serine uptake. Importantly, despite several transporters being known to be capable of transporting serine, the transporters that mediate serine uptake in cancer cells are not known. Here, we characterize the amino acid transporter ASCT2 (SLC1A5) as a major contributor to serine uptake in cancer cells. ASCT2 is well known as a glutamine transporter in cancer, and our work demonstrates that serine and glutamine compete for uptake through ASCT2. We further show that ASCT2-mediated serine uptake is essential for purine nucleotide biosynthesis and that estrogen receptor α (ERα) promotes serine uptake by directly activating SLC1A5 transcription. Collectively, our work defines an additional important role for ASCT2 as a serine transporter in cancer and evaluates ASCT2 as a potential therapeutic target.

Serine Depletion Promotes Antitumor Immunity by Activating Mitochondrial DNA-Mediated cGAS-STING Signaling

Serine is critical for supporting cancer metabolism, and depriving malignant cells of this nonessential amino acid exerts antineoplastic effects, in large part, through disrupting metabolic pathways. Given the intricate relationship between cancer metabolism and the immune system, the metabolic defects imposed by serine deprivation might impact tumor-targeting immunity. In this study, we demonstrated that restricting endogenous and exogenous sources of serine in colorectal cancer cells results in mitochondrial dysfunction, leading to mitochondrial DNA (mtDNA) accumulation in the cytosol and consequent cGAS-STING1-driven type I IFN secretion. Depleting mtDNA or blocking its release attenuated cGAS-STING1 activation during serine deprivation. In vivo studies revealed that serine deprivation limits tumor growth, accompanied by enhanced type I IFN signaling and intratumoral infiltration of immune effector cells. Notably, the tumor-suppressive and immune-enhancing effects of serine restriction were impaired by T-cell depletion and IFN receptor blockade. Moreover, disrupting cGAS-STING1 signaling in colorectal cancer cells limited the immunostimulatory and tumor-suppressive effects of serine deprivation. Lastly, serine depletion increased the sensitivity of tumors to an immune checkpoint inhibitor targeting PD-1. Taken together, these findings reveal a role for serine as a suppressor of antitumor immunity, suggesting that serine deprivation may be employed to enhance tumor immunogenicity and improve responsiveness to immune checkpoint inhibitors. Significance: Depriving cancer cells of serine provokes mitochondrial perturbations that induce cytosolic mitochondrial DNA accumulation and subsequent activation of cGAS-STING signaling, stimulating tumor-targeting immune responses that can be enhanced with PD-1 targeted therapy. See related commentary by Borges and Garg, p. 2569.

Cyclic fasting-mimicking diet in cancer treatment: Preclinical and clinical evidence

In preclinical tumor models, cyclic fasting and fasting-mimicking diets (FMDs) produce antitumor effects that become synergistic when combined with a wide range of standard anticancer treatments while protecting normal tissues from treatment-induced adverse events. More recently, results of phase 1/2 clinical trials showed that cyclic FMD is safe, feasible, and associated with positive metabolic and immunomodulatory effects in patients with different tumor types, thus paving the way for larger clinical trials to investigate FMD anticancer activity in different clinical contexts. Here, we review the tumor-cell-autonomous and immune-system-mediated mechanisms of fasting/FMD antitumor effects, and we critically discuss new metabolic interventions that could synergize with nutrient starvation to boost its anticancer activity and prevent or reverse tumor resistance while minimizing toxicity to patients. Finally, we highlight potential future applications of FMD approaches in combination with standard anticancer strategies as well as strategies to implement the design and conduction of clinical trials.

Phenylalanine deprivation inhibits multiple myeloma progression by perturbing endoplasmic reticulum homeostasis

Amino acid metabolic remodeling is a hallmark of cancer, driving an increased nutritional demand for amino acids. Amino acids are pivotal for energetic regulation, biosynthetic support, and homeostatic maintenance to stimulate cancer progression. However, the role of phenylalanine in multiple myeloma (MM) remains unknown. Here, we demonstrate that phenylalanine levels in MM patients are decreased in plasma but elevated in bone marrow (BM) cells. After the treatment, phenylalanine levels increase in plasma and decrease in BM. This suggests that changes in phenylalanine have diagnostic value and that phenylalanine in the BM microenvironment is an essential source of nutrients for MM progression. The requirement for phenylalanine by MM cells exhibits a similar pattern. Inhibiting phenylalanine utilization suppresses MM cell growth and provides a synergistic effect with Bortezomib (BTZ) treatment in vitro and murine models. Mechanistically, phenylalanine deprivation induces excessive endoplasmic reticulum stress and leads to MM cell apoptosis through the ATF3-CHOP-DR5 pathway. Interference with ATF3 significantly affects phenylalanine deprivation therapy. In conclusion, we have identified phenylalanine metabolism as a characteristic feature of MM metabolic remodeling. Phenylalanine is necessary for MM proliferation, and its aberrant demand highlights the importance of low-phenylalanine diets as an adjuvant treatment for MM.

Subcellular one carbon metabolism in cancer, aging and epigenetics

The crosstalk between metabolism and epigenetics is an emerging field that is gaining importance in different areas such as cancer and aging, where changes in metabolism significantly impacts the cellular epigenome, in turn dictating changes in chromatin as an adaptive mechanism to bring back metabolic homeostasis. A key metabolic pathway influencing an organism's epigenetic state is one-carbon metabolism (OCM), which includes the folate and methionine cycles. Together, these cycles generate S-adenosylmethionine (SAM), the universal methyl donor essential for DNA and histone methylation. SAM serves as the sole methyl group donor for DNA and histone methyltransferases, making it a crucial metabolite for chromatin modifications. In this review, we will discuss how SAM and its byproduct, S-adenosylhomocysteine (SAH), along with the enzymes and cofactors involved in OCM, may function in the different cellular compartments, particularly in the nucleus, to directly regulate the epigenome in aging and cancer.

Current advances in cancer energy metabolism under dietary restriction: a mini review

The manipulation of the energy or source of food for cancer cells has attracted significant attention in oncology research. Metabolic reprogramming of the immune system allows for a deeper understanding of cancer cell mechanisms, thereby impeding their progression. A more targeted approach is the restriction of cancer cells through dietary restriction (CR), which deprives cancer cells of the preferred energy sources within the tumor microenvironment, thereby enhancing immune cell efficacy. Although there is a plethora of CR strategies that can be employed to impede cancer progression, there is currently no comprehensive review that delineates the specific dietary restrictions that target the diverse metabolic pathways of cancer cells. This mini-review introduces amino acids as anti-cancer agents and discusses the role of dietary interventions in cancer prevention and treatment. It highlights the potential of a ketogenic diet as a therapeutic approach for cancer, elucidating its distinct mechanisms of action in tumor progression. Additionally, the potential of plant-based diets as anti-cancer agents and the role of polyphenols and vitamins in anti-cancer therapy were also discussed, along with some prospective interventions for CR as anti-tumor progression.

A Multimodal Drug-Diet-Immunotherapy Combination Restrains Melanoma Progression and Metastasis

The genetic landscape of cancer cells can lead to specific metabolic dependencies for tumor growth. Dietary interventions represent an attractive strategy to restrict the availability of key nutrients to tumors. In this study, we identified that growth of a subset of melanoma was severely restricted by a rationally designed combination therapy of a stearoyl-CoA desaturase (SCD) inhibitor with an isocaloric low-oleic acid diet. Despite its importance in oncogenesis, SCD underwent monoallelic codeletion along with PTEN on chromosome 10q in approximately 47.5% of melanoma, and the other SCD allele was methylated, resulting in very low-SCD expression. Although this SCD-deficient subset was refractory to SCD inhibitors, the subset of PTEN wild-type melanoma that retained SCD was sensitive. As dietary oleic acid could potentially blunt the effect of SCD inhibitors, a low oleic acid custom diet was combined with an SCD inhibitor. The combination reduced monounsaturated fatty acids and increased saturated fatty acids, inducing robust apoptosis and growth suppression and inhibiting lung metastasis with minimal toxicity in preclinical mouse models of PTEN wild-type melanoma. When combined with anti-PD1 immunotherapy, the SCD inhibitor improved T-cell functionality and further constrained melanoma growth in mice. Collectively, these results suggest that optimizing SCD inhibitors with diets low in oleic acid may offer a viable and efficacious therapeutic approach for improving melanoma treatment. Significance: Blockade of endogenous production of fatty acids essential for melanoma combined with restriction of dietary intake blocks tumor growth and enhances response to immunotherapy, providing a rational drug-diet treatment regimen for melanoma.

Metabolic Reprogramming Is an Initial Step in Pancreatic Carcinogenesis That Can Be Targeted to Inhibit Acinar-to-Ductal Metaplasia

Metabolic reprogramming is a hallmark of cancer and is crucial for cancer progression, making it an attractive therapeutic target. Understanding the role of metabolic reprogramming in cancer initiation could help identify prevention strategies. To address this, we investigated metabolism during acinar-to-ductal metaplasia (ADM), the first step of pancreatic carcinogenesis. Glycolytic markers were elevated in ADM lesions compared with normal tissue from human samples. Comprehensive metabolic assessment in three mouse models with pancreas-specific activation of KRAS, PI3K, or MEK1 using Seahorse measurements, nuclear magnetic resonance metabolome analysis, mass spectrometry, isotope tracing, and RNA sequencing analysis revealed a switch from oxidative phosphorylation to glycolysis in ADM. Blocking the metabolic switch attenuated ADM formation. Furthermore, mitochondrial metabolism was required for de novo synthesis of serine and glutathione (GSH) but not for ATP production. MYC mediated the increase in GSH intermediates in ADM, and inhibition of GSH synthesis suppressed ADM development. This study thus identifies metabolic changes and vulnerabilities in the early stages of pancreatic carcinogenesis. Significance: Metabolic reprogramming from oxidative phosphorylation to glycolysis mediated by MYC plays a crucial role in the development of pancreatic cancer, revealing a mechanism driving tumorigenesis and potential therapeutic targets. See related commentary by Storz, p. 2225.

Emerging roles of long noncoding RNAs in enzymes related intracellular metabolic pathways in cancer biology

Metabolic reprogramming plays critical roles in the development and progression of tumor by providing cancer cells with a sufficient supply of nutrients and other factors needed for fast-proliferating. Emerging evidence indicates that long noncoding RNAs (lncRNAs) are involved in the initiation of metastasis via regulating the metabolic reprogramming in various cancers. In this paper, we aim to summarize that lncRNAs could participate in intracellular nutrient metabolism including glucose, amino acid, lipid, and nucleotide, regardless of whether lncRNAs have tumor-promoting or tumor-suppressor function. Meanwhile, modulation of lncRNAs in glucose metabolic enzymes in glycolysis, pentose phosphate pathway and tricarboxylic acid cycle (TCA) in cancer is reviewed. We also discuss therapeutic strategies targeted at interfering with enzyme activity to decrease the utilization of glucoses, amino acid, nucleotide acid and lipid in tumor cells. This review focuses on our current understanding of lncRNAs participating in cancer cell metabolic reprogramming, paving the way for further investigation into the combination of such approaches with existing anti-cancer therapies.

Deciphering pathophysiological mechanisms underlying cystathionine beta-synthase-deficient homocystinuria using targeted metabolomics, liver proteomics, sphingolipidomics and analysis of mitochondrial function

BACKGROUND

Cystathionine β-synthase (CBS)-deficient homocystinuria (HCU) is an inherited disorder of sulfur amino acid metabolism with varying severity and organ complications, and a limited knowledge about underlying pathophysiological processes. Here we aimed at getting an in-depth insight into disease mechanisms using a transgenic mouse model of HCU (I278T).

METHODS

We assessed metabolic, proteomic and sphingolipidomic changes, and mitochondrial function in tissues and body fluids of I278T mice and WT controls. Furthermore, we evaluated the efficacy of methionine-restricted diet (MRD) in I278T mice.

RESULTS

In WT mice, we observed a distinct tissue/body fluid compartmentalization of metabolites with up to six-orders of magnitude differences in concentrations among various organs. The I278T mice exhibited the anticipated metabolic imbalance with signs of an increased production of hydrogen sulfide and disturbed persulfidation of free aminothiols. HCU resulted in a significant dysregulation of liver proteome affecting biological oxidations, conjugation of compounds, and metabolism of amino acids, vitamins, cofactors and lipids. Liver sphingolipidomics indicated upregulation of the pro-proliferative sphingosine-1-phosphate signaling pathway. Liver mitochondrial function of HCU mice did not seem to be impaired compared to controls. MRD in I278T mice improved metabolic balance in all tissues and substantially reduced dysregulation of liver proteome.

CONCLUSION

The study highlights distinct tissue compartmentalization of sulfur-related metabolites in normal mice, extensive metabolome, proteome and sphingolipidome disruptions in I278T mice, and the efficacy of MRD to alleviate some of the HCU-related biochemical abnormalities.

PHGDH: a novel therapeutic target in cancer

Serine is a key contributor to the generation of one-carbon units for DNA synthesis during cellular proliferation. In addition, it plays a crucial role in the production of antioxidants that prevent abnormal proliferation and stress in cancer cells. In recent studies, the relationship between cancer metabolism and the serine biosynthesis pathway has been highlighted. In this context, 3-phosphoglycerate dehydrogenase (PHGDH) is notable as a key enzyme that functions as the primary rate-limiting enzyme in the serine biosynthesis pathway, facilitating the conversion of 3-phosphoglycerate to 3-phosphohydroxypyruvate. Elevated PHGDH activity in diverse cancer cells is mediated through genetic amplification, posttranslational modification, increased transcription, and allosteric regulation. Ultimately, these characteristics allow PHGDH to not only influence the growth and progression of cancer but also play an important role in metastasis and drug resistance. Consequently, PHGDH has emerged as a crucial focal point in cancer research. In this review, the structural aspects of PHGDH and its involvement in one-carbon metabolism are investigated, and PHGDH is proposed as a potential therapeutic target in diverse cancers. By elucidating how PHGDH expression promotes cancer growth, the goal of this review is to provide insight into innovative treatment strategies. This paper aims to reveal how PHGDH inhibitors can overcome resistance mechanisms, contributing to the development of effective cancer treatments.

Glucose metabolism in B cell malignancies: a focus on glycolysis branching pathways

Glucose catabolism, one of the essential pathways sustaining cellular bioenergetics, has been widely studied in the context of tumors. Nevertheless, the function of various branches of glucose metabolism that stem from 'classical' glycolysis have only been partially explored. This review focuses on discussing general mechanisms and pathological implications of glycolysis and its branching pathways in the biology of B cell malignancies. We summarize here what is known regarding pentose phosphate, hexosamine, serine biosynthesis, and glycogen synthesis pathways in this group of tumors. Despite most findings have been based on malignant B cells themselves, we also discuss the role of glucose metabolism in the tumor microenvironment, with a focus on T cells. Understanding the contribution of glycolysis branching pathways and how they are hijacked in B cell malignancies will help to dissect the role they have in sustaining the dissemination and proliferation of tumor B cells and regulating immune responses within these tumors. Ultimately, this should lead to deciphering associated vulnerabilities and improve current therapeutic schedules.