Quantification of microenvironmental metabolites in murine cancers reveals determinants of tumor nutrient availability

Impact of mtG3PDH inhibitors on proliferation and metabolism of androgen receptor-negative prostate cancer cells: Role of extracellular pyruvate

Mitochondrial glycerol 3-P dehydrogenase (mtG3PDH) plays a significant role in cellular bioenergetics by serving as a rate-limiting element in the glycerophosphate shuttle, which connects cytosolic glycolysis to mitochondrial oxidative metabolism. mtG3PDH was identified as an important site of electron leakage leading to ROS production to the mitochondrial matrix and intermembrane space. Our research focused on the role of two published mtG3PDH inhibitors (RH02211 and iGP-1) on the proliferation and metabolism of PC-3 and DU145 prostate cancer cells characterized by different mtG3PDH activities. Since pyruvate as a substrate of lactate dehydrogenase (LDH) may represent an escape mechanism for the recycling of cytosolic NAD+ via the glycerophosphate shuttle, we investigated the effect of pyruvate on the mode of action of the mtG3PDH inhibitors. Extracellular pyruvate weakened the growth-inhibitory effects of RH02211 and iGP-1 in PC-3 cells but not in DU145 cells, which correlated with higher H-type LDH and lower mitochondrial glutamate-oxaloacetate transaminase in DU145 cells. In the pyruvate-low medium, the strength of inhibition was more pronounced in PC-3 cells, characterized by higher mtG3PDH activities compared to DU145 cells. Pyruvate conversion rates (production in pyruvate-low and consumption in pyruvate-high PC-3 cells) were not impaired by RH02211 and iGP-1, suggesting that the conversion of extracellular pyruvate to lactate was not the primary factor responsible for the weakening effect of extracellular pyruvate on the RH02211-induced inhibition of PC-3 proliferation. In pyruvate-high PC-3 cells, the intracellular glycerol-3-P and dihydroxyacetone-P concentrations were consistent with an inhibition of mtG3PDH. In contrast, in pyruvate-low cells, the concentrations of these metabolites suggested an activation of mtG3PDH in parallel with an impairment of cytosolic G3PDH by RH02211. Of all metabolic characterizations recorded in this study (fluxes, intracellular intermediates, O2 consumption and H2O2 production), the decrease in glutaminolysis correlated best with the RH02211-induced inhibition of proliferation in pyruvate-low and pyruvate-high PC-3 cells.

Harnessing nutrient scarcity for enhanced CAR-T-cell potency and safety in solid tumors

Despite significant advancements, the effectiveness of chimeric antigen receptor (CAR)-T-cell-based therapies in solid tumors remains limited. Key challenges include on-target effects, off-tumor toxicity and reduced CAR-T-cell function within the tumor microenvironment, which is often characterized by metabolic stress triggered by factors such as amino acid scarcity. Activating transcription factor-4 (ATF4) and its upstream regulator GCN2 play crucial roles in the metabolic reprogramming and functionality of CD4+ and CD8+ T cells. ATF4 can be activated by various cellular stress signals, including amino acid deprivation. While ATF4 activation may be associated with T-cell dysfunction, its role in stress adaptation presents an opportunity for therapeutic intervention-particularly in the tumor microenvironment, where T-cell exhaustion is a major challenge. In this study, we developed a strategy to harness the GCN2‒ATF4 axis in CAR-T cells. We employed an amino acid-dependent inducible promoter, which triggers ATF4-dependent gene expression to regulate CAR expression in T cells under conditions of amino acid scarcity within the tumor microenvironment. In vitro and murine xenograft models demonstrate the potential of this system to effectively restrict CAR expression to the tumor site. This targeted strategy not only enhances safety by minimizing off-tumor activity but also CAR-T-cell fitness by reducing exhaustion. By validating this pathophysiologically regulatable CAR expression system for solid tumors, our findings address key limitations of current CAR-T-cell therapies and pave the way for innovative strategies targeting solid malignancies.

Engineered Probiotics-Based Biohybrid-Driven Tumor Metabolic Remodeling To Boost Tumor Photoimmunotherapy

Bioengineered probiotics enable new opportunities to address abnormal cancer metabolism and suppressive immune-environment interactions for improved therapeutic susceptibility. Here, Escherichia coli Nissle 1917 (EcN) was constructed to convert ammonia into l-arginine continuously and was further modified with polydopamine (PDA) to form living biotherapeutic argEcN@P for enhanced colorectal cancer eradication. Benefiting from the movement of EcN, argEcN@P could colonize and penetrate deep in tumors through hypoxia targeting and increase the intratumoral l-arginine concentrations. Upon near-infrared light (NIR) irradiation, heating induced by PDA could ablate tumor cells efficiently and release tumor antigens, which induce immunogenic cell death (ICD). More interestingly, argEcN@P remarkably promotes differentiation into M1-like macrophages in tumor tissues, inhibiting primary, distant tumor growth by inducing potent adaptive antitumor immunity. More importantly, argEcN@P treatment efficiently prevented postoperative tumor recurrence by inducing long-term immune memory. Taken together, this platform based on bioengineered probiotics provides a promising strategy for tumor metabolic reprogramming sensitized photothermal immunotherapy in deep tumors.

Cumulative risk assessment as the pathway to public health protection for behavioral neurotoxicity

The formulation of adverse outcome pathways (AOPs) based on high-throughput in vitro new approach methods linking biochemical/mechanistic data with an apical endpoint considered an adverse outcome (AO), is increasingly proposed to accelerate the process of risk assessment for environmental chemical exposures. While a laudable goal, this approach ignores the extensive evidence demonstrating context-dependence of neurotoxicological consequences, including behavioral toxicity of chemical exposures. Such contextual modifiers can include environmental conditions (poverty, psychosocial stress, behavioral experience/history), physiological conditions (sex, period of exposure, nutritional status, brain region, exposure parameters), and genetic background. Context dependence represents a serious omission for AOP formulation because an environmental context can alter a chemical's molecular targets, or potentially enhance toxicity through interactions with other contextual conditions, thus leading to potential underestimation of neurological risks due to such exposures. The integrative physiological basis of AOs requires cumulative risk assessments that model environmental contexts across scales of biology, i.e., integration and testing in whole-animal models. AOPs contribute to the derivation of cumulative risk considerations regarding factors to incorporate into cumulative risk assessments by defining risk factors with shared biological targets. Epidemiological and animal model studies can provide information to prioritize interactive effects of greatest magnitude. Additionally, a focus on how a single risk factor in different physiological contexts may attribute risk across multiple neurologic conditions, rather than to a single unique condition, would provide broader public health protection. Realistic acknowledgement of context-dependence is requisite to understanding both the etiological basis of neurological diseases and disorders and to human health protection.

Uptake of lipids from ascites drives NK cell metabolic dysfunction in ovarian cancer

High-grade serous ovarian cancer (HGSOC) remains an urgent unmet clinical need, with more than 70% of patients presenting with metastatic disease. Many patients develop large volumes of ascites, which promotes metastasis and is associated with poor therapeutic response and survival. Immunotherapy trials have shown limited success, highlighting the need to better understand HGSOC immunology. Here, we analyzed cytotoxic lymphocytes [natural killer (NK), T, and innate T cells] from patients with HGSOC and observed widespread dysfunction across primary and metastatic sites. Although nutrient rich, ascites was immunosuppressive for all lymphocyte subsets. NK cell dysfunction was driven by uptake of polar lipids, with associated dysregulation in lipid storage. Phosphatidylcholine was a key immunosuppressive metabolite, disrupting NK cell membrane order and cytotoxicity. Blocking lipid uptake through SR-B1 protected NK cell antitumor functions in ascites. These findings offer insights into immune suppression in HGSOC and have important implications for the design of future immunotherapies.

Glycogen drives tumour initiation and progression in lung adenocarcinoma

Lung adenocarcinoma (LUAD) is an aggressive cancer defined by oncogenic drivers and metabolic reprogramming. Here we leverage next-generation spatial screens to identify glycogen as a critical and previously underexplored oncogenic metabolite. High-throughput spatial analysis of human LUAD samples revealed that glycogen accumulation correlates with increased tumour grade and poor survival. Furthermore, we assessed the effect of increasing glycogen levels on LUAD via dietary intervention or via a genetic model. Approaches that increased glycogen levels provided compelling evidence that elevated glycogen substantially accelerates tumour progression, driving the formation of higher-grade tumours, while the genetic ablation of glycogen synthase effectively suppressed tumour growth. To further establish the connection between glycogen and cellular metabolism, we developed a multiplexed spatial technique to simultaneously assess glycogen and cellular metabolites, uncovering a direct relationship between glycogen levels and elevated central carbon metabolites essential for tumour growth. Our findings support the conclusion that glycogen accumulation drives LUAD cancer progression and provide a framework for integrating spatial metabolomics with translational models to uncover metabolic drivers of cancer.

An ISR-independent role of GCN2 prevents excessive ribosome biogenesis and mRNA translation

The integrated stress response (ISR) is a corrective physiological programme to restore cellular homeostasis that is based on the attenuation of global protein synthesis and a resource-enhancing transcriptional programme. GCN2 is the oldest of four kinases that are activated by diverse cellular stresses to trigger the ISR and acts as the primary responder to amino acid shortage and ribosome collisions. Here, using a broad multi-omics approach, we uncover an ISR-independent role of GCN2. GCN2 inhibition or depletion in the absence of discernible stress causes excessive protein synthesis and ribosome biogenesis, perturbs the cellular translatome, and results in a dynamic and broad loss of metabolic homeostasis. Cancer cells that rely on GCN2 to keep protein synthesis in check under conditions of full nutrient availability depend on GCN2 for survival and unrestricted tumour growth. Our observations describe an ISR-independent role of GCN2 in regulating the cellular proteome and translatome and suggest new avenues for cancer therapies based on unleashing excessive mRNA translation.

Tumour interstitial fluid-enriched phosphoethanolamine suppresses T cell function

Nutrient stress represents an important barrier for anti-tumour immunity, and tumour interstitial fluid often contains metabolites that hinder immune function. However, it is difficult to isolate the effects of tumour nutrient stress from other suppressive factors. Thus, we used a chemically defined cell culture medium based on the metabolomic profile of tumour interstitial fluid: tumour interstitial fluid medium (TIFM). Culture of CD8+ T cells in TIFM limited cell expansion and impaired CD8+ T cell effector functions upon restimulation, suggesting that tumour nutrient stress alone is sufficient to drive T cell dysfunction. We identified phosphoethanolamine (pEtn), a phospholipid intermediate, as a driver of T cell dysfunction. pEtn dampened T cell receptor signalling by depleting T cells of diacylglycerol required for T cell receptor signal transduction. The reduction of pEtn accumulation in tumours improved intratumoural T cell function and tumour control, suggesting that pEtn accumulation plays a dominant role in immunosuppression in the tumour microenvironment.

Polyamine metabolism in prostate cancer

PURPOSE OF REVIEW

Normal and malignant prostate engage in high rates of de novo polyamine synthesis. This review considers how polyamine metabolism regulates prostate cancer initiation and progression.

RECENT FINDINGS

The androgen receptor (AR) establishes a metabolic program to drive robust polyamine synthesis in the normal prostate. Upon malignant transformation, this AR-driven metabolic program persists and is optimized for oncogenesis by the proto-oncogene MYC and/or alterations to PI3K signaling. A deeper understanding of the function of polyamines in prostate cancer may be obtained by considering their function in the normal prostate.

SUMMARY

Recent findings support ongoing research into the role of polyamines in driving prostate cancer initiation and progression and suggest targeting polyamine metabolism remains a promising therapeutic strategy for prevention and treatment of prostate cancer.

Post-transcriptional regulator HuR promotes immune evasion in pancreatic ductal adenocarcinoma

The tumor microenvironment (TME) of pancreatic ductal adenocarcinoma (PDAC) is characterized by a limited infiltration of tumor-specific T cells and anti-tumor T cell activity. Extracellular factors in the PDAC TME have been widely reported to mediate immune suppression, but the contribution from tumor-intrinsic factors is not well understood. The RNA-binding protein, HuR (ELAVL1), is enriched in PDAC and negatively correlates with T cell infiltration. In an immunocompetent Kras-p53-Cre (KPC) orthotopic model of PDAC, we found that genetic disruption of HuR impaired tumor growth due to a novel role of HuR inducing T-cell suppression. Importantly, we found that HuR depletion in tumors enhanced both T cell number and activation states and diminished myeloid phenotypes by comprehensive spatial profiling of the PDAC TME. Mechanistically, HuR mediated the stabilization of mTOR pathway transcripts, and inhibition of mTOR activity rescued the impaired function of local T cells. Translating these findings, we demonstrated that HuR depletion sensitized PDAC tumors to immune checkpoint blockade, while isogenic, wildtype tumors are resistant. For the first time, we show that HuR facilitates tumor immune suppression in PDAC by inhibiting T cell infiltration and function and implicate targeting HuR as a potential therapeutic strategy in combination with immunotherapy.

Can the Tumor Microenvironment Alter Ion Channels? Unraveling Their Role in Cancer

Neoplastic cells are characterized by metabolic reprogramming, known as the Warburg effect, in which glucose metabolism is predominantly directed toward aerobic glycolysis, with reduced mitochondrial oxidative phosphorylation and increased lactate production even in the presence of oxygen. This phenomenon provides cancer cells with a proliferative advantage, allowing them to rapidly produce energy (in the form of ATP) and generate metabolic intermediates necessary for the biosynthesis of macromolecules essential for cell growth. It is important to understand the role of ion channels in the tumor context since they participate in various physiological processes and in the regulation of the tumor microenvironment. These changes may contribute to the development and transformation of cancer cells, as well as affect the communication between cells and the surrounding microenvironment, including impaired or altered expression and functionality of ion channels. Therefore, the aim of this review is to elucidate the impact of the tumor microenvironment on the electrical properties of the cellular membranes in several cancers as a possible therapeutic target.

Deciphering the Matrisome: Extracellular Matrix Remodeling in Liver Cirrhosis and Hepatocellular Carcinoma

Liver cirrhosis and hepatocellular carcinoma (HCC) are major public health concerns due to their high morbidity and mortality rates. The liver, a vital organ for metabolism, detoxification, and homeostasis, depends on the matrisome, a complex and dynamic network of extracellular matrix (ECM) components for maintaining structural and functional integrity. Chronic liver inflammation, induced by factors such as alcohol abuse, viral hepatitis, and non-alcoholic fatty liver disease, leads to fibrosis and cirrhosis, progressing to HCC. The matrisome, composed of ECM proteins including collagen, fibronectin, and laminin, plays a critical role in regulating tissue homeostasis, cell signaling, and tissue repair. Dysregulation of ECM components contributes to the pathogenesis of both liver cirrhosis and cancer. In cirrhosis, matrisome alterations are characterized by excessive ECM deposition and fibrosis, which disrupt the liver's architecture and impair its function. Activated hepatic stellate cells (HSCs) are the principal mediators of fibrosis, producing large quantities of ECM components. In liver cancer, matrisome remodeling facilitates tumorigenesis by promoting cancer cell proliferation, invasion, and metastasis. The tumor microenvironment, shaped by ECM alterations, further supports tumor growth and dissemination. Matrix metalloproteinases (MMPs) play a pivotal role in ECM degradation, fibrosis progression, and tumor invasion, while tissue inhibitors of metalloproteinases (TIMPs) modulate MMP activity. A comprehensive understanding of the molecular mechanisms that link matrisome alterations with the progression from cirrhosis to liver cancer is essential for identifying novel diagnostic and therapeutic targets. This review highlights the dynamic responses of the hepatic matrisome to both acute and chronic insults, emphasizing the complex interplay between ECM components, cellular behavior, and disease progression. Elucidating these interactions may inform strategies aimed at improving clinical outcomes for patients with liver cirrhosis and HCC.

Metabolic interplays between the tumour and the host shape the tumour macroenvironment

Metabolic reprogramming of cancer cells and the tumour microenvironment are pivotal characteristics of cancers, and studying these processes offer insights and avenues for cancer diagnostics and therapeutics. Recent advancements have underscored the impact of host systemic features, termed macroenvironment, on facilitating cancer progression. During tumorigenesis, these inherent features of the host, such as germline genetics, immune profile and the metabolic status, influence how the body responds to cancer. In parallel, as cancer grows, it induces systemic effects beyond the primary tumour site and affects the macroenvironment, for example, through inflammation, the metabolic end-stage syndrome of cachexia, and metabolic dysregulation. Therefore, understanding the intricate metabolic interplay between the tumour and the host is a growing frontier in advancing cancer diagnosis and therapy. In this Review, we explore the specific contribution of the metabolic fitness of the host to cancer initiation, progression and response to therapy. We then delineate the complex metabolic crosstalk between the tumour, the microenvironment and the host, which promotes disease progression to metastasis and cachexia. The metabolic relationships among the host, cancer pathogenesis and the consequent responsive systemic manifestations during cancer progression provide new perspectives for mechanistic cancer therapy and improved management of patients with cancer.

Myeloid cells: key players in tumor microenvironments

Cancer is the result of evolving crosstalk between neoplastic cell and its immune microenvironment. In recent years, immune therapeutics targeting T lymphocytes, such as immune checkpoint blockade (ICB) and CAR-T, have made significant progress in cancer treatment and validated targeting immune cells as a promising approach to fight human cancers. However, responsiveness to the current immune therapeutic agents is limited to only a small proportion of solid cancer patients. As major components of most solid tumors, myeloid cells played critical roles in regulating the initiation and sustentation of adaptive immunity, thus determining tumor progression as well as therapeutic responses. In this review, we discuss emerging data on the diverse functions of myeloid cells in tumor progression through their direct effects or interactions with other immune cells. We explain how different metabolic reprogramming impacts the characteristics and functions of tumor myeloid cells, and discuss recent progress in revealing different mechanisms-chemotaxis, proliferation, survival, and alternative sources-involved in the infiltration and accumulation of myeloid cells within tumors. Further understanding of the function and regulation of myeloid cells is important for the development of novel strategies for therapeutic exploitation in cancer.

CDKN2A Low cancer cells outcompete macrophages for microenvironmental zinc to drive immunotherapy resistance

Approximately 50% of cancers exhibit decreased CDKN2A expression ( CDKN2A Low ), which is linked to immune checkpoint blockade (ICB) resistance. While CDKN2A is traditionally recognized as a tumor suppressor and cell cycle regulator, we have previously put forth a new paradigm demonstrating its role in intracellular metabolic reprogramming. Whether the metabolic derangement due to CDKN2A loss alters metabolites within the tumor microenvironment (TME) and how that affects the immune compartment and ICB response has never been investigated. Here we found that CDKN2A Low cancer cells reorganize zinc compartmentalization by upregulating the zinc importer SLC39A9 in the plasma membrane, leading to intracellular zinc accumulation in cancer cells and concurrent zinc depletion in the TME. This competition for zinc results in zinc-starved tumor-associated macrophages (TAMs), leading to reduced phagocytic activity. Increasing zinc in TAMs through multiple approaches, including a dietary intervention that increases availability of TME zinc, re-educates these TAMs to a pro-phagocytic phenotype. Remarkably, both knockdown of Slc39a9 in cancer cells or providing a high zinc diet sensitizes Cdkn2a Low tumors to ICB. TAMs, not T cells, are indispensable for ICB response. Clinically, TAMs from CDKN2A Low cancer patients have decreased zinc signatures, corresponding to reduced phagocytosis signatures. Moreover, patients with low circulating zinc levels have reduced time-to-event outcomes compared to those with higher zinc levels. Our work reveals a previously unrecognized mechanism through which CDKN2A Low cancer cells outcompete TAMs for zinc, directly disrupting their function and ICB efficacy.

The tumor microenvironment is an ecosystem sustained by metabolic interactions

Cancer-associated fibroblasts (CAFs) and immune cells make up two major components of the tumor microenvironment (TME), contributing to an ecosystem that can either support or restrain cancer progression. Metabolism is a key regulator of the TME, providing a means for cells to communicate with and influence each other, modulating tumor progression and anti-tumor immunity. Cells of the TME can metabolically interact directly through metabolite secretion and consumption or by influencing other aspects of the TME that, in turn, stimulate metabolic rewiring in target cells. Recent advances in understanding the subtypes and plasticity of cells in the TME both open up new avenues and create challenges for metabolically targeting the TME to hamper tumor growth and improve response to therapy. This perspective explores ways in which the CAF and immune components of the TME could metabolically influence each other, based on current knowledge of their metabolic states, interactions, and subpopulations.

NLRP4 unlocks an NK/macrophages-centered ecosystem to suppress non-small cell lung cancer

BACKGROUND

Tumor immune evasion extends beyond T cells, affecting innate immune elements like natural killer cells (NK) and macrophages within the tumor-immune microenvironment (TIME). Nevertheless, translational strategies to trigger collaboration of NK cells and macrophages to initiate sufficient anti-tumor cytoxicity remain scarce and are urgently needed.

METHODS

In this study, TCGA datasets was used to confirm the prognosis value of the expression level of NLR family pyrin domain containing 4 (NLRP4) in NSCLC and the tumor tissues microarray was used to further check its clinical-relevance at protein-level. Subsequently, a tumor cell line with stable NLRP4 overexpression was established and subcutaneous tumor models in C57BL/6J mice were used to validate the anti-tumor characteristics of NLRP4. After analyzing the tumor microenvironment using flow cytometry and multiplex immunofluorescence, we further validated our findings through co-culture transwell assays and TCGA analysis. Utilizing bulk-RNA sequencing, proteomics, and mass spectrometry of mouse tumor tissues, we innovatively identified the downstream pathways of NLRP4 and verified them through co-immunoprecipitation (co-IP) and Western blot (WB) experiments.

RESULTS

NLRP4 could trigger a distinct anti-tumor ecosystem organized by TIGIT+TNFA+ NK and iNOS+ M1 in lung cancer, discovered in TCGA analysis and verified in murine model. NLRP4-eco exerted tumor-suppression capacity through chemokine reprogramming including CCL5 and CXCL2. Meanwhile, the cytoxicity of NK could be facilitated by iNOS+M1. Mechanistically, NLRP4 stimulated PI3K/Akt-NF-kB axis through suppression of the activity of PP2A. Besides, knockdown of CCL5 and blockade of CXCL2-CXCR2 axis abolished chemotaxis of TIGIT+TNFA+ NK and iNOS+ M1 respectively, as well as for LB-100, a PP2A inhibitor.

CONCLUSION

Altogether, we delineated NLRP4's unexplored facets and discovered an NLRP4-driven anti-tumor ecosystem composed of TIGIT+TNFA+ NK and iNOS+ M1. Finally, targeting PP2A by its inhibitor successfully mimicked the anti-tumor capacity of the overexpression of NLRP4.

Direct sensing of dietary ω-6 linoleic acid through FABP5-mTORC1 signaling

Diet influences macronutrient availability to cells, and although mechanisms of sensing dietary glucose and amino acids are well characterized, less is known about sensing lipids. We defined a nutrient signaling mechanism involving fatty acid-binding protein 5 (FABP5) and mechanistic target of rapamycin complex 1 (mTORC1) that is activated by the essential polyunsaturated fatty acid (PUFA) ω-6 linoleic acid (LA). FABP5 directly bound to the regulatory-associated protein of mTOR (Raptor) to enhance formation of functional mTORC1 and substrate binding, ultimately converging on increased mTOR signaling and proliferation. The amounts of FABP5 protein were increased in tumors and serum from triple-negative compared with those from receptor-positive breast cancer patients, which highlights its potential role as a biomarker that mediates cellular responses to ω-6 LA intake in this disease subtype.

Interleukin-16 enhances anti-tumor immune responses by establishing a Th1 cell-macrophage crosstalk through reprogramming glutamine metabolism in mice

Overcoming immunosuppression in the tumor microenvironment (TME) is crucial for developing novel cancer immunotherapies. Here, we report that IL-16 administration enhances the polarization of T helper 1 (Th1) cells by inhibiting glutamine catabolism through the downregulation of glutaminase in CD4+ T cells and increases the production of Th1 effector cytokine IFN-γ, thus improving anti-tumor immune responses. Moreover, we find that establishing an IL-16-dependent, Th1-dominant TME relies on mast cell-produced histamine and results in the increased expression of the CXCR3 ligands in tumor-associated macrophages (TAM), thereby improving the therapeutic effectiveness of immune checkpoint blockade (ICB). Cancer patients exhibit impaired production of IL-16, which correlates with poorer prognosis. Additionally, low IL-16 production is associated with unresponsiveness to immunotherapy in cancer patients. Collectively, our findings provided new insights into the biological function of IL-16, emphasizing its potential clinical significance as a therapeutic approach to augment anti-tumor immunity and sensitize ICB-based cancer immunotherapy.

Arginine: at the crossroads of nitrogen metabolism

L-arginine is the most nitrogen-rich amino acid, acting as a key precursor for the synthesis of nitrogen-containing metabolites and an essential intermediate in the clearance of excess nitrogen. Arginine's side chain possesses a guanidino group which has unique biochemical properties, and plays a primary role in nitrogen excretion (urea), cellular signaling (nitric oxide) and energy buffering (phosphocreatine). The post-translational modification of protein-incorporated arginine by guanidino-group methylation also contributes to epigenetic gene control. Most human cells do not synthesize sufficient arginine to meet demand and are dependent on exogenous arginine. Thus, dietary arginine plays an important role in maintaining health, particularly upon physiologic stress. How cells adapt to changes in extracellular arginine availability is unclear, mostly because nearly all tissue culture media are supplemented with supraphysiologic levels of arginine. Evidence is emerging that arginine-deficiency can influence disease progression. Here, we review new insights into the importance of arginine as a metabolite, emphasizing the central role of mitochondria in arginine synthesis/catabolism and the recent discovery that arginine can act as a signaling molecule regulating gene expression and organelle dynamics.

Targeting metabolic dysfunction of CD8 T cells and natural killer cells in cancer

The importance of metabolic pathways in regulating immune responses is now well established, and a mapping of the bioenergetic metabolism of different immune cell types is under way. CD8 T cells and natural killer (NK) cells contribute to cancer immunosurveillance through their cytotoxic functions and secretion of cytokines and chemokines, complementing each other in target recognition mechanisms. Several immunotherapies leverage these cell types by either stimulating their activity or redirecting their specificity against tumour cells. However, the anticancer activity of CD8 T cells and NK cells is rapidly diminished in the tumour microenvironment, closely linked to a decline in their metabolic capacities. Various strategies have been developed to restore cancer immunosurveillance, including targeting bioenergetic metabolism or genetic engineering. This Review provides an overview of metabolic dysfunction in CD8 T cells and NK cells within the tumour microenvironment, highlighting current therapies aiming to overcome these issues.

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.

Deciphering Colorectal Cancer-Hepatocyte Interactions: A Multiomics Platform for Interrogation of Metabolic Crosstalk in the Liver-Tumor Microenvironment

Metabolic reprogramming is a hallmark of cancer, enabling tumor cells to adapt to and exploit their microenvironment for sustained growth. The liver is a common site of metastasis, but the interactions between tumor cells and hepatocytes remain poorly understood. In the context of liver metastasis, these interactions play a crucial role in promoting tumor survival and progression. This study leverages multiomics coverage of the microenvironment via liquid chromatography and high-resolution, high-mass-accuracy mass spectrometry-based untargeted metabolomics, 13C-stable isotope tracing, and RNA sequencing to uncover the metabolic impact of co-localized primary hepatocytes and a colon adenocarcinoma cell line, SW480, using a 2D co-culture model. Metabolic profiling revealed disrupted Warburg metabolism with an 80% decrease in glucose consumption and 94% decrease in lactate production by hepatocyte-SW480 co-cultures relative to SW480 control cultures. Decreased glucose consumption was coupled with alterations in glutamine and ketone body metabolism, suggesting a possible fuel switch upon co-culturing. Further, integrated multiomics analysis indicates that disruptions in metabolic pathways, including nucleoside biosynthesis, amino acids, and TCA cycle, correlate with altered SW480 transcriptional profiles and highlight the importance of redox homeostasis in tumor adaptation. Finally, these findings were replicated in three-dimensional microtissue organoids. Taken together, these studies support a bioinformatic approach to study metabolic crosstalk and discovery of potential therapeutic targets in preclinical models of the tumor microenvironment.

Innovative Applications of Bacteria and Their Derivatives in Targeted Tumor Therapy

Despite significant progress in cancer treatment, traditional therapies still face considerable challenges, including poor targeting, severe toxic side effects, and the development of resistance. Recent advances in biotechnology have revealed the potential of bacteria and their derivatives as drug delivery systems for tumor therapy by leveraging their biological properties. Engineered bacteria, including Escherichia coli, Salmonella, and Listeria monocytogenes, along with their derivatives─outer membrane vesicles (OMVs), bacterial ghosts (BGs), and bacterial spores (BSPs)─can be loaded with a variety of antitumor agents, enabling precise targeting and sustained drug release within the tumor microenvironment (TME). These bacteria and their derivatives possess intrinsic properties that stimulate the immune system, enhancing both innate and adaptive immune responses to further amplify therapeutic effects. The ability of bacteria to naturally accumulate in hypoxic tumor regions and their versatility in genetic modifications allow for tailored drug delivery strategies that synergistically enhance the effectiveness of chemotherapy, immunotherapy, and targeted therapies. This review comprehensively examines the fundamental principles of bacterial therapy, focusing on the strategies employed for bacterial engineering, drug loading, and the use of bacteria and their derivatives in targeted tumor therapy. It also discusses the challenges faced in optimizing bacterial delivery systems, such as safety concerns, unintended immune responses, and scalability for clinical applications. By exploring these aspects, this review provides a theoretical framework for improving bacterial-based drug delivery systems, contributing to the development of more effective and personalized cancer treatments.

SLC7A5 is required for cancer cell growth under arginine-limited conditions

Tumor cells must optimize metabolite acquisition between synthesis and uptake from a microenvironment characterized by hypoxia, lactate accumulation, and depletion of many amino acids, including arginine. We performed a metabolism-focused functional screen using CRISPR-Cas9 to identify pathways and factors that enable tumor growth in an arginine-depleted environment. Our screen identified the SLC-family transporter SLC7A5 as required for growth, and we hypothesized that this protein functions as a high-affinity citrulline transporter. Using isotope tracing experiments, we show that citrulline uptake and metabolism into arginine are dependent upon expression of SLC7A5. Pharmacological inhibition of SLC7A5 blocks growth under low-arginine conditions across a diverse group of cancer cell lines. Loss of SLC7A5 reduces tumor growth and citrulline import in a mouse tumor model. We identify a conditionally essential role for SLC7A5 in arginine metabolism, and we propose that SLC7A5-targeting therapeutic strategies in cancer may be effective in the context of arginine limitation.

FLT3 is associated with dendritic cell infiltration, tertiary lymphoid structure construction, and predict response to checkpoint inhibitors immunotherapy in solid cancers

The crosstalk between cancers and the immune microenvironment plays a critical role in malignant progression. FMS-like tyrosine kinase 3 (FLT3) is a frequently mutated gene in acute myeloid leukemia (AML). However, its role in solid cancers remains poorly understood. We analyzed the frequency of FLT3 alterations, its mRNA expression levels, and its prognostic implications across multiple cancer types. Additionally, we explored genes co-expressed with FLT3 and performed gene ontology analysis to identify associated biological processes. We also examined the relationship between FLT3 expression and markers of various immune cells, tertiary lymphoid structures (TLSs), and epithelial-mesenchymal transition. Furthermore, we validated these findings in our own cohort of hepatocellular carcinoma (HCC) patients. We found that FLT3 alteration and expression were both significantly upregulated in AML and were associated with poor prognosis, which is opposite to its role in solid cancers. The genes co-expressed with FLT3 in solid cancers were correlated with the regulation of the immune microenvironment. FLT3 was positively correlated with the formation of TLSs in only solid cancers, which was especially relevant to central memory T cells. We also found that FLT3 was positively correlated with the infiltration of NK cells, B cells, and DCs. It also positively correlated with the occurrence of apoptosis in solid cancers, but exhibited opposite roles in AML. The structural factors of the TLSs were positively correlated with FLT3 in solid cancers, but exhibited a negative correlation in AML. Meanwhile, we further validated the above conclusions in our own HCC cohort and demonstrated that FLT3 could serve as a predictive indicator of PD-1 treatment efficacy in HCC. In summary, the role of FLT3 is different in AML and solid cancers. FLT3 is associated with dendritic cell infiltration, tertiary lymphoid structure construction, and predict response to checkpoint inhibitors immunotherapy in HCC.

Tumor metabolic regulators: key drivers of metabolic reprogramming and the promising targets in cancer therapy

Metabolic reprogramming within the tumor microenvironment (TME) is a hallmark of cancer and a crucial determinant of tumor progression. Research indicates that various metabolic regulators form a metabolic network in the TME and interact with immune cells, coordinating the tumor immune response. Metabolic dysregulation creates an immunosuppressive TME, impairing the antitumor immune response. In this review, we discuss how metabolic regulators affect the tumor cell and the crosstalk of TME. We also summarize recent clinical trials involving metabolic regulators and the challenges of metabolism-based tumor therapies in clinical translation. In a word, our review distills key regulatory factors and their mechanisms of action from the complex reprogramming of tumor metabolism, identified as tumor metabolic regulators. These regulators provide a theoretical basis and research direction for the development of new strategies and targets in cancer therapy based on tumor metabolic reprogramming.

Genetics and biology of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) poses a grim prognosis for patients. Recent multidisciplinary research efforts have provided critical insights into its genetics and tumor biology, creating the foundation for rational development of targeted and immune therapies. Here, we review the PDAC genomic landscape and the role of specific oncogenic events in tumor initiation and progression, as well as their contributions to shaping its tumor biology. We further summarize and synthesize breakthroughs in single-cell and metabolic profiling technologies that have illuminated the complex cellular composition and heterotypic interactions of the PDAC tumor microenvironment, with an emphasis on metabolic cross-talk across cancer and stromal cells that sustains anabolic growth and suppresses tumor immunity. These conceptual advances have generated novel immunotherapy regimens, particularly cancer vaccines, which are now in clinical testing. We also highlight the advent of KRAS targeted therapy, a milestone advance that has transformed treatment paradigms and offers a platform for combined immunotherapy and targeted strategies. This review provides a perspective summarizing current scientific and therapeutic challenges as well as practice-changing opportunities for the PDAC field at this major inflection point.

HIF2α inhibits glutaminase clustering in mitochondria to sustain growth of clear cell Renal Cell Carcinoma

Clear cell renal cell carcinomas (ccRCC) are largely driven by HIF2α and are avid consumers of glutamine. However, inhibitors of glutaminase1 (GLS1), the first step in glutaminolysis, have not shown benefit in phase III trials, and HIF2α inhibition, recently FDA-approved for treatment of ccRCC, shows great but incomplete benefits, underscoring the need to better understand the roles of glutamine and HIF2α in ccRCC. Here, we report that glutamine deprivation rapidly redistributes GLS1 into isolated clusters within mitochondria across diverse cell types, but not in ccRCC. GLS1 clustering is rapid (1-3 hours) and reversible, is specifically driven by reduced intracellular glutamate, and is mediated by mitochondrial fission. Clustered GLS1 markedly enhances glutaminase activity and promotes cell death under glutamine-deprived conditions. HIF2α prevents GLS1 clustering, independently of its transcriptional activity, thereby protecting ccRCC cells from cell death induced by glutamine deprivation. Reversing this protection, by genetic expression of GLS1 mutants that constitutively cluster, enhances ccRCC cell death in culture and suppresses ccRCC growth in vivo. These findings provide multiple insights into cellular glutamine handling, including a novel metabolic pathway by which HIF2α promotes ccRCC, and reveals a potential therapeutic avenue to synergize with HIF2α inhibition in the treatment of ccRCC.

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.

Machine learning based identification of an amino acid metabolism related signature for predicting prognosis and immune microenvironment in pancreatic cancer

BACKGROUND

Pancreatic cancer is a highly aggressive neoplasm characterized by poor diagnosis. Amino acids play a prominent role in the occurrence and progression of pancreatic cancer as essential building blocks for protein synthesis and key regulators of cellular metabolism. Understanding the interplay between pancreatic cancer and amino acid metabolism offers potential avenues for improving patient clinical outcomes.

METHODS

A comprehensive analysis integrating 10 machine learning algorithms was executed to pinpoint amino acid metabolic signature. The signature was validated across both internal and external cohorts. Subsequent GSEA was employed to unveil the enriched gene sets and signaling pathways within high- and low-risk subgroups. TMB and drug sensitivity analyses were carried out via Maftools and oncoPredict R packages. CIBERSORT and ssGSEA were harnessed to delve into the immune landscape disparities. Single-cell transcriptomics, qPCR, and Immunohistochemistry were performed to corroborate the expression levels and prognostic significance of this signature.

RESULTS

A four gene based amino acid metabolic signature with superior prognostic capabilities was identified by the combination of 10 machine learning methods. It showed that the novel prognostic model could effectively distinguish patients into high- and low-risk groups in both internal and external cohorts. Notably, the risk score from this novel signature showed significant correlations with TMB, drug resistance, as well as a heightened likelihood of immune evasion and suboptimal responses to immunotherapeutic interventions.

CONCLUSION

Our findings suggested that amino acid metabolism-related signature was closely related to the development, prognosis and immune microenvironment of pancreatic cancer.

Creating Physiological Cell Environments In Vitro: Adjusting Cell Culture Media Composition and Oxygen Levels to Investigate Mitochondrial Function and Cancer Metabolism

In vitro and ex vivo studies are crucial for mitochondrial research, offering valuable insights into cellular mechanisms and aiding in diagnostic and therapeutic strategies. Accurate in vitro models rely on adequate cell culture conditions, such as the composition of culture media and oxygenation levels. These conditions can influence energy metabolism and mitochondrial activities, thus impacting studies involving mitochondrial components, such as the effectiveness of anticancer drugs. This chapter focuses on practical guidance for creating setups that replicate in vivo microenvironments, capturing the original metabolic context of cells. We explore protocols to better mimic the physiological cell environment, promote cellular reconfiguration, and prime cells according to the modeled context. The first part is dedicated to the use of human dermal fibroblasts, which are a promising model for pre-clinical mitochondrial research due to their adaptability and relevance to human mitochondrial physiology. We present an optimized protocol for gradually adjusting extracellular glucose levels, which demonstrated significant mitochondrial, metabolic, and redox remodeling in normal adult dermal fibroblasts. The second part is dedicated to replication of tumor microenvironments, which are relevant for studies targeting cellular energy metabolism to inhibit tumor growth. Currently available physiological media can mimic blood plasma metabolome but not the specific tumor microenvironment. To address this, we describe optimized media formulation and oxygenation protocols, which can simulate the tumor microenvironment in cell culture experiments. Replicating in vivo microenvironments in in vitro and ex vivo studies can enhance our understanding of cellular processes, facilitate drug development, and advance personalized therapeutics in mitochondrial medicine.

The influence of endothelial metabolic reprogramming on the tumor microenvironment

Endothelial cells (ECs) that line blood vessels act as gatekeepers and shape the metabolic environment of every organ system. In normal conditions, endothelial cells are relatively quiescent with organ-specific expression signatures and metabolic profiles. In cancer, ECs are metabolically reprogrammed to promote the formation of new blood vessels to fuel tumor growth and metastasis. In addition to EC's role on tumor cells, the tortuous tumor vasculature contributes to an immunosuppressive environment by limiting T lymphocyte infiltration and activity while also promoting the recruitment of other accessory pro-angiogenic immune cells. These elements aid in the metastatic spreading of cancer cells and contribute to therapeutic resistance. The concept of restoring a more stabilized vasculature in concert with cancer immunotherapy is emerging as a potential approach to overcoming barriers in cancer treatment. This review summarizes the metabolism of endothelial cells, their regulation of nutrient uptake and delivery, and their impact in shaping the tumor microenvironment and anti-tumor immunity. We highlight new therapeutic approaches that target the tumor vasculature and harness the immune response. Appreciating the integration of metabolic state and nutrient levels and the crosstalk among immune cells, tumor cells, and ECs in the TME may provide new avenues for therapeutic intervention.

Fuel for thought: targeting metabolism in lung cancer

For over a century, we have appreciated that the biochemical processes through which micro- and macronutrients are anabolized and catabolized-collectively referred to as "cellular metabolism"-are reprogrammed in malignancies. Cancer cells in lung tumors rewire pathways of nutrient acquisition and metabolism to meet the bioenergetic demands for unchecked proliferation. Advances in precision medicine have ushered in routine genotyping of patient lung tumors, enabling a deeper understanding of the contribution of altered metabolism to tumor biology and patient outcomes. This paradigm shift in thoracic oncology has spawned a new enthusiasm for dissecting oncogenotype-specific metabolic phenotypes and creates opportunity for selective targeting of essential tumor metabolic pathways. In this review, we discuss metabolic states across histologic and molecular subtypes of lung cancers and the additional changes in tumor metabolic pathways that occur during acquired therapeutic resistance. We summarize the clinical investigation of metabolism-specific therapies, addressing successes and limitations to guide the evaluation of these novel strategies in the clinic. Beyond changes in tumor metabolism, we also highlight how non-cellular autonomous processes merit particular consideration when manipulating metabolic processes systemically, such as efforts to disentangle how lung tumor cells influence immunometabolism. As the future of metabolic therapeutics hinges on use of models that faithfully recapitulate metabolic rewiring in lung cancer, we also discuss best practices for harmonizing workflows to capture patient specimens for translational metabolic analyses.

Adaptation to cystine limitation stress promotes PDAC tumor growth and metastasis through translational upregulation of OxPPP

Cystine/cysteine is critical for antioxidant response and sulfur metabolism in cancer cells and is one of the most depleted amino acids in the PDAC microenvironment. The effects of cystine limitation stress (CLS) on PDAC progression are poorly understood. Here we report that adaptation to CLS (CLSA) promotes PDAC cell proliferation and tumor growth through translational upregulation of the oxidative pentose phosphate pathway (OxPPP). OxPPP activates the de novo synthesis of nucleotides and fatty acids to support tumor growth. Our data suggested that much like hypoxia, CLS in the tumor microenvironment could promote PDAC tumor growth and metastasis through upregulating anabolic metabolism of nucleotides and lipids.

Deciphering Colorectal Cancer-Hepatocyte Interactions: A Multiomic Platform for Interrogation of Metabolic Crosstalk in the Liver-Tumor Microenvironment

Metabolic reprogramming is a hallmark of cancer, enabling tumor cells to adapt to and exploit their microenvironment for sustained growth. The liver is a common site of metastasis, but the interactions between tumor cells and hepatocytes remain poorly understood. In the context of liver metastasis, these interactions play a crucial role in promoting tumor survival and progression. This study leverages multiomics coverage of the microenvironment via liquid chromatography and high-resolution, high-mass accuracy mass spectrometry-based untargeted metabolomics, 13C-stable isotope tracing, and RNA sequencing to uncover the metabolic impact of co-localized primary hepatocytes and a colon adenocarcinoma cell line, SW480, using a 2D co-culture model. Metabolic profiling revealed disrupted Warburg metabolism with an 80% decrease in glucose consumption and 94% decrease in lactate production by hepatocyte-SW480 co-cultures relative to SW480 control cultures. Decreased glucose consumption was coupled with alterations in glutamine and ketone body metabolism, suggesting a possible fuel switch upon co-culturing. Further, integrated multiomic analysis indicates that disruptions in metabolic pathways, including nucleoside biosynthesis, amino acids, and TCA cycle, correlate with altered SW480 transcriptional profiles and highlight the importance of redox homeostasis in tumor adaptation. Finally, these findings were replicated in 3-dimensional microtissue organoids. Taken together, these studies support a bioinformatic approach to study metabolic crosstalk and discovery of potential therapeutic targets in preclinical models of the tumor microenvironment.

Androgen receptor drives polyamine synthesis creating a vulnerability for prostate cancer

Supraphysiological androgen (SPA) treatment can paradoxically restrict growth of castration-resistant prostate cancer with high androgen receptor (AR) activity, which is the basis for use of Bipolar Androgen Therapy (BAT) for patients with this disease. While androgens are widely appreciated to enhance anabolic metabolism, how SPA-mediated metabolic changes alter prostate cancer progression and therapy response is unknown. Here, we report that SPA markedly increased intracellular and secreted polyamines in prostate cancer models. This occurred through AR binding at enhancer sites upstream of the ODC1 promoter to increase abundance of ornithine decarboxylase (ODC), a rate-limiting enzyme of polyamine synthesis, and de novo synthesis of polyamines from arginine. SPA-stimulated polyamines enhance prostate cancer fitness, as dCas9-KRAB-mediated inhibition of AR regulation of ODC1 or direct ODC inhibition by difluoromethylornithine (DFMO) increased efficacy of SPA. Mechanistically, this occurred in part due to increased activity of S-adenosylmethionine decarboxylase 1 (AMD1), which was stimulated both by AR and by loss of negative feedback by polyamines, leading to depletion of its substrate S-adenosylmethionine and global protein methylation. These data provided the rationale for a clinical trial testing the safety and efficacy of BAT in combination with DFMO for patients with metastatic castration-resistant prostate cancer. Pharmacodynamic studies of this drug combination in the first five patients on trial indicated that the drug combination resulted in effective polyamine depletion in plasma. Thus, the AR potently stimulates polyamine synthesis, which constitutes a vulnerability in prostate cancer treated with SPA that can be targeted therapeutically.

Plasticity and Tumor Microenvironment in Pancreatic Cancer: Genetic, Metabolic, and Immune Perspectives

Cancer has long been believed to be a genetic disease caused by the accumulation of mutations in key genes involved in cellular processes. However, recent advances in sequencing technology have demonstrated that cells with cancer driver mutations are also present in normal tissues in response to aging, environmental damage, and chronic inflammation, suggesting that not only intrinsic factors within cancer cells, but also environmental alterations are important key factors in cancer development and progression. Pancreatic cancer tissue is mostly comprised of stromal cells and immune cells. The desmoplasmic microenvironment characteristic of pancreatic cancer is hypoxic and hypotrophic. Pancreatic cancer cells may adapt to this environment by rewiring their metabolism through epigenomic changes, enhancing intrinsic plasticity, creating an acidic and immunosuppressive tumor microenvironment, and inducing noncancerous cells to become tumor-promoting. In addition, pancreatic cancer has often metastasized to local and distant sites by the time of diagnosis, suggesting that a similar mechanism is operating from the precancerous stage. Here, we review key recent findings on how pancreatic cancers acquire plasticity, undergo metabolic reprogramming, and promote immunosuppressive microenvironment formation during their evolution. Furthermore, we present the following two signaling pathways that we have identified: one based on the small G-protein ARF6 driven by KRAS/TP53 mutations, and the other based on the RNA-binding protein Arid5a mediated by inflammatory cytokines, which promote both metabolic reprogramming and immune evasion in pancreatic cancer. Finally, the striking diversity among pancreatic cancers in the relative importance of mutational burden and the tumor microenvironment, their clinical relevance, and the potential for novel therapeutic strategies will be discussed.

Macropinocytosis controls metabolic stress-driven CAF subtype identity in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) tumors are deficient in glutamine, an amino acid that tumor cells and CAFs use to sustain their fitness. In PDAC, both cell types stimulate macropinocytosis as an adaptive response to glutamine depletion. CAFs play a critical role in sculpting the tumor microenvironment, yet how adaptations to metabolic stress impact the stromal architecture remains elusive. In this study, we find that macropinocytosis functions to control CAF subtype identity when glutamine is limiting. Our data demonstrate that metabolic stress leads to an intrinsic inflammatory CAF (iCAF) program driven by MEK/ERK signaling. Utilizing in vivo models, we find that blocking macropinocytosis alters CAF subtypes and reorganizes the tumor stroma. Importantly, these changes in stromal architecture can be exploited to sensitize PDAC to immunotherapy and chemotherapy. Our findings demonstrate that metabolic stress plays a role in shaping the tumor microenvironment, and that this attribute can be harnessed for therapeutic impact.

Isolation and characterization of microbiota from human pancreatic tumors and small intestine

Pancreatic ductal adenocarcinoma has a unique tumor microbiome and the systemic depletion of bacteria or fungi using antibiotic/antifungal cocktails leads to a decrease in pancreatic tumor burden in mice. However, functional studies remain rare due to the limited availability of clinically relevant microbiota. Here, we describe in detail the isolation of bacteria and fungi from the small intestine and tumor of pancreatic cancer patients at the Rogel Cancer Center. We then further characterized the impact of a newly isolated Klebsiella oxytoca strain ( UMKO1 ) on the pancreatic tumor microenvironment using bacterial genome sequencing, untargeted and targeted metabolomics, as well as an ex vivo tumor transplant system. We found that UMKO1 possesses a gene for the long form of cytidine deaminase, which can inactivate the standard PDAC chemotherapeutic agent gemcitabine. In addition, we found that UMKO1 can produce several indoles when grown in tumor-like conditions, metabolites that can lead to an immune suppressive environment and interfere with therapy outcome. To test this in detail, we assessed changes in immune populations in pancreatic tumor explants upon exposure to the supernatant of UMKO1 and other isolated bacteria grown in tumor Interstitial fluid media (TIFM). We found that while none of the bacterial supernatants changed the abundance of CD8 T cells, granzyme B positive CD8 T cells were the lowest in tumor explants exposed to UMKO1 , and not other isolated Klebsiella species or the non-pathogenic laboratory strain E. coli K12 . In summary, the isolated collection of bacteria and fungi from this study are a valuable toolbox to study the impact of microbiota on pancreatic cancer.

Diet and Cancer Metabolism

Diet and exercise are modifiable lifestyle factors known to have a major influence on metabolism. Clinical practice addresses diseases of altered metabolism such as diabetes or hypertension by altering these factors. Despite enormous public interest, there are limited defined diet and exercise regimens for cancer patients. Nevertheless, the molecular basis of cancer has converged over the past 15 years on an essential role for altered metabolism in cancer. However, our understanding of the molecular mechanisms that underlie the impact of diet and exercise on cancer metabolism is in its very early stages. In this work, we propose conceptual frameworks for understanding the consequences of diet and exercise on cancer cell metabolism and tumor biology and also highlight recent developments. By advancing our mechanistic understanding, we also discuss actionable ways that such interventions could eventually reach the mainstay of both medical oncology and cancer control and prevention.

A Targetable Secreted Neural Protein Drives Pancreatic Cancer Metastatic Colonization and HIF1α Nuclear Retention

Pancreatic ductal adenocarcinoma (PDAC) is an increasingly diagnosed cancer that kills 90% of afflicted patients, with most patients receiving palliative chemotherapy. We identified neuronal pentraxin 1 (NPTX1) as a cancer-secreted protein that becomes overexpressed in human and murine PDAC cells during metastatic progression and identified adhesion molecule with Ig-like domain 2 (AMIGO2) as its receptor. Molecular, genetic, biochemical, and pharmacologic experiments revealed that secreted NPTX1 acts cell-autonomously on the AMIGO2 receptor to drive PDAC metastatic colonization of the liver-the primary site of PDAC metastasis. NPTX1-AMIGO2 signaling enhanced hypoxic growth and was critically required for hypoxia-inducible factor-1α (HIF1α) nuclear retention and function. NPTX1 is overexpressed in human PDAC tumors and upregulated in liver metastases. Therapeutic targeting of NPTX1 with a high-affinity monoclonal antibody substantially reduced PDAC liver metastatic colonization. We thus identify NPTX1-AMIGO2 as druggable critical upstream regulators of the HIF1α hypoxic response in PDAC. Significance: We identified the NPTX1-AMIGO2 axis as a regulatory mechanism upstream of HIF1α-driven hypoxia response that promotes PDAC liver metastasis. Therapeutic NPTX1 targeting outperformed a common chemotherapy regimen in inhibiting liver metastasis and suppressed primary tumor growth in preclinical models, revealing a novel therapeutic strategy targeting hypoxic response in PDAC.

Aspartate in tumor microenvironment and beyond: Metabolic interactions and therapeutic perspectives

Aspartate is a proteinogenic non-essential amino acid with several essential functions in proliferating cells. It is mostly produced in a cell autonomous manner from oxalacetate via glutamate oxalacetate transaminases 1 or 2 (GOT1 or GOT2), but in some cases it can also be salvaged from the microenvironment via transporters such as SLC1A3 or by macropinocytosis. In this review we provide an overview of biosynthetic pathways that produce aspartate endogenously during proliferation. We discuss conditions that favor aspartate uptake as well as possible sources of exogenous aspartate in the microenvironment of tumors and bone marrow, where most available data have been generated. We highlight metabolic fates of aspartate, its various functions, and possible approaches to target aspartate metabolism for cancer therapy.

Thermogenic Adipocytes Promote M2 Macrophage Polarization through CNNM4-Mediated Mg Secretion

M2 macrophages promote adipose tissue thermogenesis which dissipates energy in the form of heat to combat obesity. However, the regulation of M2 macrophages by thermogenic adipocytes is unclear. Here, it is identified magnesium (Mg) as a thermogenic adipocyte-secreted factor to promote M2 macrophage polarization. Mg transporter Cyclin and CBS domain divalent metal cation transport mediator 4 (CNNM4) induced by ADRB3-PKA-CREB signaling in thermogenic adipocytes during cold exposure mediates Mg efflux and Mg in turn binds to the DFG motif in mTOR to facilitate mTORC2 activation and M2 polarization in macrophages. In obesity, downregulation of CNNM4 expression inhibits Mg secretion from thermogenic adipocytes, which leads to decreased M2 macrophage polarization and thermogenesis. As a result, CNNM4 overexpression in adipocytes or Mg supplementation in adipose tissue ameliorates obesity by promoting thermogenesis. Importantly, an Mg wire implantation (AMI) approach is introduced to achieve adipose tissue-specific long-term Mg supplement. AMI promotes M2 macrophage polarization and thermogenesis and ameliorates obesity in mice. Taken together, a reciprocal regulation of thermogenic adipocytes and M2 macrophages important for thermogenesis is identified, and AMI is offered as a promising strategy against obesity.

Glucose limitation protects cancer cells from apoptosis induced by pyrimidine restriction and replication inhibition

Cancer cells often experience nutrient-limiting conditions because of their robust proliferation and inadequate tumour vasculature, which results in metabolic adaptation to sustain proliferation. Most cancer cells rapidly consume glucose, which is severely reduced in the nutrient-scarce tumour microenvironment. In CRISPR-based genetic screens to identify metabolic pathways influenced by glucose restriction, we find that tumour-relevant glucose concentrations (low glucose) protect cancer cells from inhibition of de novo pyrimidine biosynthesis, a pathway that is frequently targeted by chemotherapy. We identify two mechanisms to explain this result, which is observed broadly across cancer types. First, low glucose limits uridine-5-diphosphate-glucose synthesis, preserving pyrimidine nucleotide availability and thereby prolonging the time to replication fork stalling. Second, low glucose directly modulates apoptosis downstream of replication fork stalling by suppressing BAK activation and subsequent cytochrome c release, key events that activate caspase-9-dependent mitochondrial apoptosis. These results indicate that the low glucose levels frequently observed in tumours may limit the efficacy of specific chemotherapeutic agents, highlighting the importance of considering the effects of the tumour nutrient environment on cancer therapy.

Lipids and adipocytes involvement in tumor progression with a focus on obesity and diet

The adipose tissue is a complex organ that can play endocrine, metabolic, and immune regulatory roles in cancer. In particular, adipocytes provide metabolic substrates for cancer cell proliferation and produce signaling molecules that can stimulate cell adhesion, migration, invasion, angiogenesis, and inflammation. Cancer cells, in turn, can reprogram adipocytes towards a more inflammatory state, resulting in a vicious cycle that fuels tumor growth and evolution. These mechanisms are enhanced in obesity, which is associated with the risk of developing certain tumors. Diet, an exogenous source of lipids with pro- or anti-inflammatory functions, has also been connected to cancer risk. This review analyzes how adipocytes and lipids are involved in tumor development and progression, focusing on the relationship between obesity and cancer. In addition, we discuss how diets with varying lipid intakes can affect the disease outcomes. Finally, we introduce novel metabolism-targeted treatments and adipocyte-based therapies in oncology.

Dietary fructose enhances tumour growth indirectly via interorgan lipid transfer

Fructose consumption has increased considerably over the past five decades, largely due to the widespread use of high-fructose corn syrup as a sweetener1. It has been proposed that fructose promotes the growth of some tumours directly by serving as a fuel2,3. Here we show that fructose supplementation enhances tumour growth in animal models of melanoma, breast cancer and cervical cancer without causing weight gain or insulin resistance. The cancer cells themselves were unable to use fructose readily as a nutrient because they did not express ketohexokinase-C (KHK-C). Primary hepatocytes did express KHK-C, resulting in fructolysis and the excretion of a variety of lipid species, including lysophosphatidylcholines (LPCs). In co-culture experiments, hepatocyte-derived LPCs were consumed by cancer cells and used to generate phosphatidylcholines, the major phospholipid of cell membranes. In vivo, supplementation with high-fructose corn syrup increased several LPC species by more than sevenfold in the serum. Administration of LPCs to mice was sufficient to increase tumour growth. Pharmacological inhibition of ketohexokinase had no direct effect on cancer cells, but it decreased circulating LPC levels and prevented fructose-mediated tumour growth in vivo. These findings reveal that fructose supplementation increases circulating nutrients such as LPCs, which can enhance tumour growth through a cell non-autonomous mechanism.

Cancer-associated fibroblasts maintain critical pancreatic cancer cell lipid homeostasis in the tumor microenvironment

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy with abundant cancer-associated fibroblasts (CAFs) creating hallmark desmoplasia that limits oxygen and nutrient delivery. This study explores the importance of lipid homeostasis under stress. Exogenous unsaturated lipids, rather than de novo synthesis, sustain PDAC cell viability by relieving endoplasmic reticulum (ER) stress under nutrient scarcity. Furthermore, CAFs are less hypoxic than adjacent malignant cells in vivo, nominating them as a potential source of unsaturated lipids. CAF-conditioned medium promotes PDAC cell survival upon nutrient and oxygen deprivation, an effect reversed by delipidation. Lysophosphatidylcholines (LPCs) are particularly enriched in CAF-conditioned medium and preferentially taken up by PDAC cells, where they are converted to phosphatidylcholine (PC) to sustain membrane integrity. Blocking LPC-to-PC conversion inhibits PDAC cell survival and increases ER stress. These findings show a critical lipid "cross-feeding" mechanism that promotes PDAC cell survival, offering a potential metabolic target for treatment.