Uridine-derived ribose fuels glucose-restricted pancreatic cancer

From monocyte-derived macrophages to resident macrophages-how metabolism leads their way in cancer

Macrophages are innate immune cells that play key roles during both homeostasis and disease. Depending on the microenvironmental cues sensed in different tissues, macrophages are known to acquire specific phenotypes and exhibit unique features that, ultimately, orchestrate tissue homeostasis, defense, and repair. Within the tumor microenvironment, macrophages are referred to as tumor-associated macrophages (TAMs) and constitute a heterogeneous population. Like their tissue resident counterpart, TAMs are plastic and can switch function and phenotype according to the niche-derived stimuli sensed. While changes in TAM phenotype are known to be accompanied by adaptive alterations in their cell metabolism, it is reported that metabolic reprogramming of macrophages can dictate their activation state and function. In line with these observations, recent research efforts have been focused on defining the metabolic traits of TAM subsets in different tumor malignancies and understanding their role in cancer progression and metastasis formation. This knowledge will pave the way to novel therapeutic strategies tailored to cancer subtype-specific metabolic landscapes. This review outlines the metabolic characteristics of distinct TAM subsets and their implications in tumorigenesis across multiple cancer types.

tRNA-derived RNA fragment, tRF-18-8R6546D2, promotes pancreatic adenocarcinoma progression by directly targeting ASCL2

Pancreatic adenocarcinoma (PAAD) is a life-threatening cancer. Exploring new diagnosis and treatment targets helps improve its prognosis. tRNA-derived small non-coding RNAs (tsRNAs) are a novel type of gene expression regulators and their dysregulation is closely related to many human cancers. Yet the expression and functions of tsRNAs in PAAD are not well understood. Our study used RNA sequencing to identify tsRNA expression profiles in PAAD cells cultured in no or high glucose media and found tRF-18-8R6546D2 was an uncharacterized tsRNA, which has significantly high expression in PAAD cells and tissues. Clinically, tRF-18-8R6546D2 is linked to poor prognosis in PAAD patients and can be used to distinguish them from healthy populations. Functionally, in vitro and vivo, tRF-18-8R6546D2 over-expression promoted PAAD cell proliferation, migration and invasion, inhibited apoptosis, whereas tRF-18-8R6546D2 knock-down showed opposite effects. Mechanistically, tRF-18-8R6546D2 promoted PAAD malignancy partly by directly silencing ASCL2 and further regulating its downstream genes such as MYC and CASP3. These findings show that tRF-18-8R6546D2 is a novel oncogenic factor and can be a promising diagnostic or prognostic biomarker and therapeutic target for PAAD.

Nucleotide metabolism-related host proteins RNA polymerase II subunit and uridine phosphorylase 1 interacting with porcine epidemic diarrhea virus N proteins affect viral replication

Porcine epidemic diarrhea virus (PEDV) is a highly infectious pathogen that targets pig intestines to cause disease. It is globally widespread and causes huge economic losses to the pig industry. PEDV N protein is the protein that constitutes the core of PEDV virus particles, and most of it is expressed in the cytoplasm, and a small part can also be expressed in the nucleus. However, the role of related proteins in host nucleotide metabolic pathways in regulating PEDV replication have not been fully elucidated. In this study, PEDV-N-labeled antibodies were co-immunoprecipitated and combined with LC-MS to screen for host proteins that interact with N proteins. Bioinformatics analyses showed that the selected host proteins were mainly enriched in metabolic pathways. Moreover, co-immunoprecipitation and confocal microscopy confirmed that the second-largest subunit of RNA polymerase II (RPB2) and uridine phosphorylase 1 (UPP1) interacted with the N protein. RPB2 is the main subunit of RNA polymerase II and plays an important role in eukaryotic transcription. UPP1 is an enzyme that catalyzes reversible phosphorylation of uridine to uracil and ribo-1-phosphate to promote catabolism and bio anabolism. RPB2 overexpression significantly promoted viral replication, whereas UPP1 overexpression significantly inhibited viral replication. Studies on interactions between the PEDV N and host proteins are helpful in elucidating the pathogenesis and immune escape mechanism of PEDV.

Recreating metabolic interactions of the tumour microenvironment

Tumours are heterogeneous tissues containing diverse populations of cells and an abundant extracellular matrix (ECM). This tumour microenvironment prompts cancer cells to adapt their metabolism to survive and grow. Besides epigenetic factors, the metabolism of cancer cells is shaped by crosstalk with stromal cells and extracellular components. To date, most experimental models neglect the complexity of the tumour microenvironment and its relevance in regulating the dynamics of the metabolism in cancer. We discuss emerging strategies to model cellular and extracellular aspects of cancer metabolism. We highlight cancer models based on bioengineering, animal, and mathematical approaches to recreate cell-cell and cell-matrix interactions and patient-specific metabolism. Combining these approaches will improve our understanding of cancer metabolism and support the development of metabolism-targeting therapies.

Stable Isotope Tracing Analysis in Cancer Research: Advancements and Challenges in Identifying Dysregulated Cancer Metabolism and Treatment Strategies

Metabolic reprogramming is a hallmark of cancer, driving the development of therapies targeting cancer metabolism. Stable isotope tracing has emerged as a widely adopted tool for monitoring cancer metabolism both in vitro and in vivo. Advances in instrumentation and the development of new tracers, metabolite databases, and data analysis tools have expanded the scope of cancer metabolism studies across these scales. In this review, we explore the latest advancements in metabolic analysis, spanning from experimental design in stable isotope-labeling metabolomics to sophisticated data analysis techniques. We highlight successful applications in cancer research, particularly focusing on ongoing clinical trials utilizing stable isotope tracing to characterize disease progression, treatment responses, and potential mechanisms of resistance to anticancer therapies. Furthermore, we outline key challenges and discuss potential strategies to address them, aiming to enhance our understanding of the biochemical basis of cancer metabolism.

Targeting metabolism to enhance immunotherapy within tumor microenvironment

Cancer metabolic reprogramming has been considered an emerging hallmark in tumorigenesis and the antitumor immune response. Like cancer cells, immune cells within the tumor microenvironment or premetastatic niche also undergo extensive metabolic reprogramming, which profoundly impacts anti-tumor immune responses. Numerous evidence has illuminated that immunosuppressive TME and the metabolites released by tumor cells, including lactic acid, Prostaglandin E2 (PGE2), fatty acids (FAs), cholesterol, D-2-Hydroxyglutaric acid (2-HG), adenosine (ADO), and kynurenine (KYN) can contribute to CD8+ T cell dysfunction. Dynamic alterations of these metabolites between tumor cells and immune cells can similarly initiate metabolic competition in the TME, leading to nutrient deprivation and subsequent microenvironmental acidosis, which impedes immune response. This review summarizes the new landscape beyond the classical metabolic pathways in tumor cells, highlighting the pivotal role of metabolic disturbance in the immunosuppressive microenvironment, especially how nutrient deprivation in TME leads to metabolic reprogramming of CD8+ T cells. Likewise, it emphasizes the current therapeutic targets or strategies related to tumor metabolism and immune response, providing therapeutic benefits for tumor immunotherapy and drug development in the future. Cancer metabolic reprogramming has been considered an emerging hallmark in tumorigenesis and the antitumor immune response. Dynamic alterations of metabolites between tumor cells and immune cells initiate metabolic competition in the TME, leading to nutrient deprivation and subsequent microenvironmental acidosis, which impedes immune response.

Cellular collusion: cracking the code of immunosuppression and chemo resistance in PDAC

Despite the efforts, pancreatic ductal adenocarcinoma (PDAC) is still highly lethal. Therapeutic challenges reside in late diagnosis and establishment of peculiar tumor microenvironment (TME) supporting tumor outgrowth. This stromal landscape is highly heterogeneous between patients and even in the same patient. The organization of functional sub-TME with different cellular compositions provides evolutive advantages and sustains therapeutic resistance. Tumor progressively establishes a TME that can suit its own needs, including proliferation, stemness and invasion. Cancer-associated fibroblasts and immune cells, the main non-neoplastic cellular TME components, follow soluble factors-mediated neoplastic instructions and synergize to promote chemoresistance and immune surveillance destruction. Unveiling heterotypic stromal-neoplastic interactions is thus pivotal to breaking this synergism and promoting the reprogramming of the TME toward an anti-tumor milieu, improving thus the efficacy of conventional and immune-based therapies. We underscore recent advances in the characterization of immune and fibroblast stromal components supporting or dampening pancreatic cancer progression, as well as novel multi-omic technologies improving the current knowledge of PDAC biology. Finally, we put into context how the clinic will translate the acquired knowledge to design new-generation clinical trials with the final aim of improving the outcome of PDAC patients.

Transketolase promotes MAFLD by limiting inosine-induced mitochondrial activity

Metabolic dysfunction-associated fatty liver disease (MAFLD) has a global prevalence of about 25% and no approved therapy. Using metabolomic and proteomic analyses, we identified high expression of hepatic transketolase (TKT), a metabolic enzyme of the pentose phosphate pathway, in human and mouse MAFLD. Hyperinsulinemia promoted TKT expression through the insulin receptor-CCAAT/enhancer-binding protein alpha axis. Utilizing liver-specific TKT overexpression and knockout mouse models, we demonstrated that TKT was sufficient and required for MAFLD progression. Further metabolic flux analysis revealed that Tkt deletion increased hepatic inosine levels to activate the protein kinase A-cAMP response element binding protein cascade, promote phosphatidylcholine synthesis, and improve mitochondrial function. Moreover, insulin induced hepatic TKT to limit inosine-dependent mitochondrial activity. Importantly, N-acetylgalactosamine (GalNAc)-siRNA conjugates targeting hepatic TKT showed promising therapeutic effects on mouse MAFLD. Our study uncovers how hyperinsulinemia regulates TKT-orchestrated inosine metabolism and mitochondrial function and provides a novel therapeutic strategy for MAFLD prevention and treatment.

Metabolic disturbance of short- and medium-chain chlorinated paraffins to zebrafish larva

Chlorinated paraffins (CPs) are widely produced chemicals. Short-chain CPs (SCCPs) and medium-chain CPs (MCCPs) were listed as Persistent Organic Pollutants (POPs) and candidate POPs under the Stockholm Convention, respectively. The present study explored the developmental toxicity and metabolic disruption caused by SCCPs and MCCPs in zebrafish (Danio rerio) larvae. CPs exposure at environmentally relevant levels caused no obvious phenotypic changes with zebrafish larvae except that the body length shortening was observed after exposure to CPs at 1-200 μg/L for 7 day post fertilization. A further metabolomic approach was conducted to explore the early biological responses of developmental toxicity induced by CPs at low dose (1, 5, and 10 μg/L). The results of metabolic disorder, pathway analysis and chronic values indicated that, compared with SCCPs, MCCPs exhibited more risks to zebrafish larvae at low doses. Lipid metabolism was markedly affected in SCCPs exposure group, whereas MCCPs primarily disturbed lipid metabolism, amino acid, and nucleotide metabolisms. Compare with SCCPs, the relatively higher lipid solubility, protein affinity and metabolic rate of MCCPs can probably explain why MCCP-mediated metabolic disruption was significantly higher than that of SCCP. Notably, SCCPs and MCCPs have the same potential to cause cancer, but no evidence indicates the mutagenicity. In summary, our study provides insight into the potential adverse outcome for SCCP and MCCP at low doses.

Long non-coding RNA HOTAIR: from pan-cancer analysis to colorectal cancer-related uridine metabolism

Long non-coding RNAs (lncRNAs) are involved significantly in the development of human cancers. lncRNA HOTAIR has been reported to play an oncogenic role in many human cancers. Its specific regulatory role is still elusive. And it might have enormous potential to interpret the malignant progression of tumors in a broader perspective, that is, in pan-cancer. We comprehensively investigated the effect of HOTAIR expression on tumor prognosis across human malignancies by analyzing multiple cancer-related databases like The Cancer Genome Atlas (TCGA) and Tumor Immune Estimation Resource (TIMER). Bioinformatics data indicated that HOTAIR was overexpressed in most of these human malignancies and was significantly associated with the prognosis of patients with cancer, especially in colorectal cancer (CRC). Subsequently, this study further clarified the utility of HOTAIR that downregulation of its expression could result in reduced proliferation and invasion of CRC cells. Mechanistically, HOTAIR upregulated the metabolic enzymes UPP1 by recruiting histone methyltransferase EZH2, thereby increasing the tumor progression. Our results highlight the essential role of HOTAIR in pan-cancer and uridine bypass, suggesting that the HOTAIR/EZH2/UPP1 axis might be a novel target for overcoming CRC. We anticipate that the role of HOTAIR in metabolism could be important in the context of CRC and even exploited for therapeutic purposes.

Crosstalk between metabolic remodeling and epigenetic reprogramming: A new perspective on pancreatic cancer

Pancreatic cancer is a highly malignant solid tumor with a poor prognosis and a high mortality rate. Thus, exploring the mechanisms underlying the development and progression of pancreatic cancer is critical for identifying targets for diagnosis and treatment. Two important hallmarks of cancer-metabolic remodeling and epigenetic reprogramming-are interconnected and closely linked to regulate one another, creating a complex interaction landscape that is implicated in tumorigenesis, invasive metastasis, and immune escape. For example, metabolites can be involved in the regulation of epigenetic enzymes as substrates or cofactors, and alterations in epigenetic modifications can in turn regulate the expression of metabolic enzymes. The crosstalk between metabolic remodeling and epigenetic reprogramming in pancreatic cancer has gained considerable attention. Here, we review the emerging data with a focus on the reciprocal regulation of metabolic remodeling and epigenetic reprogramming. We aim to highlight how these mechanisms could be applied to develop better therapeutic strategies.

Nucleosides are overlooked fuels in central carbon metabolism

From our daily nutrition and synthesis within cells, nucleosides enter the bloodstream and circulate throughout the body and tissues. Nucleosides and nucleotides are classically viewed as precursors of nucleic acids, but recently they have emerged as a novel energy source for central carbon metabolism. Through catabolism by nucleoside phosphorylases, the ribose sugar group is released and can provide substrates for lower steps in glycolysis. In environments with limited glucose, such as at sites of infection or in the tumor microenvironment (TME), cells can use, and may even require, this alternative energy source. Here, we discuss the implications of these new findings in health and disease and speculate on the potential new roles of nucleosides and nucleic acids in energy metabolism.

Targeting PIKfyve-driven lipid homeostasis as a metabolic vulnerability in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) subsists in a nutrient-deregulated microenvironment, making it particularly susceptible to treatments that interfere with cancer metabolism12. For example, PDAC utilizes and is dependent on high levels of autophagy and other lysosomal processes3-5. Although targeting these pathways has shown potential in preclinical studies, progress has been hampered by the challenge of identifying and characterizing favorable targets for drug development6. Here, we characterize PIKfyve, a lipid kinase integral to lysosomal functioning7, as a novel and targetable vulnerability in PDAC. In human patient and murine PDAC samples, we discovered that PIKFYVE is overexpressed in PDAC cells compared to adjacent normal cells. Employing a genetically engineered mouse model, we established the essential role of PIKfyve in PDAC progression. Further, through comprehensive metabolic analyses, we found that PIKfyve inhibition obligated PDAC to upregulate de novo lipid synthesis, a relationship previously undescribed. PIKfyve inhibition triggered a distinct lipogenic gene expression and metabolic program, creating a dependency on de novo lipid metabolism pathways, by upregulating genes such as FASN and ACACA. In PDAC, the KRAS-MAPK signaling pathway is a primary driver of de novo lipid synthesis, specifically enhancing FASN and ACACA levels. Accordingly, the simultaneous targeting of PIKfyve and KRAS-MAPK resulted in the elimination of tumor burden in a syngeneic orthotopic model and tumor regression in a xenograft model of PDAC. Taken together, these studies suggest that disrupting lipid metabolism through PIKfyve inhibition induces synthetic lethality in conjunction with KRAS-MAPK-directed therapies for PDAC.

Pharmaceutical Manipulation of Mitochondrial F0F1-ATP Synthase Enables Imaging and Protection of Myocardial Ischemia/Reperfusion Injury Through Stress-induced Selective Enrichment

To rescue ischemic myocardium from progressing to myocardial infarction, timely identification of the infarct size and reperfusion is crucial. However, fast and accurate identification, as well as the targeted protection of injured cardiomyocytes following ischemia/reperfusion (I/R) injury, remain significantly challenging. Here, a near infrared heptamethine dye IR-780 is shown that has the potential to quickly monitor the area at risk following I/R injury by selectively entering the cardiomyocytes of the at-risk heart tissues. Preconditioning with IR-780 or timely IR-780 administration before reperfusion significantly protects the heart from ischemia and oxidative stress-induced cell death, myocardial remodeling, and heart failure in both rat and pig models. Furthermore, IR-780 can directly bind to F0F1-ATP synthase of cardiomyocytes, rapidly decrease the mitochondrial membrane potential, and subsequently slow down the mitochondrial energy metabolism, which induces the mitochondria into a "quiescent state" and results in mitochondrial permeability transition pore inhibition by preventing mitochondrial calcium overload. Collectively, the findings show the feasibility of IR-780-based imaging and protection strategy for I/R injury in a preclinical context and indicate that moderate mitochondrial function depression is a mode of action that can be targeted in the development of cardioprotective reagents.

Uridine and its role in metabolic diseases, tumors, and neurodegenerative diseases

Uridine is a pyrimidine nucleoside found in plasma and cerebrospinal fluid with a concentration higher than the other nucleosides. As a simple metabolite, uridine plays a pivotal role in various biological processes. In addition to nucleic acid synthesis, uridine is critical to glycogen synthesis through the formation of uridine diphosphate glucose in which promotes the production of UDP-GlcNAc in the hexosamine biosynthetic pathway and supplies UDP-GlcNAc for O-GlcNAcylation. This process can regulate protein modification and affect its function. Moreover, Uridine has an effect on body temperature and circadian rhythms, which can regulate the metabolic rate and the expression of metabolic genes. Abnormal levels of blood uridine have been found in people with diabetes and obesity, suggesting a link of uridine dysregulation and metabolic disorders. At present, the role of uridine in glucose metabolism and lipid metabolism is controversial, and the mechanism is not clear, but it shows the trend of long-term damage and short-term benefit. Therefore, maintaining uridine homeostasis is essential for maintaining basic functions and normal metabolism. This article summarizes the latest findings about the metabolic effects of uridine and the potential of uridine metabolism as therapeutic target in treatment of metabolic disorders.

Metabolites that feed upper glycolytic branches support glucose independent human cytomegalovirus replication

The broad tissue distribution and cell tropism of human cytomegalovirus indicates that the virus successfully replicates in tissues with various nutrient environments. HCMV requires and reprograms central carbon metabolism for viral replication. However, many studies focus on reprogramming of metabolism in high nutrient conditions that do not recapitulate physiological nutrient environments in the body. In this study, we investigate how HCMV successfully replicates when nutrients are suboptimal. We limited glucose following HCMV infection to determine how glucose supports virus replication and how nutrients potentially present in the physiological environment contribute to successful glucose independent HCMV replication. Glucose is required for HCMV viral genome synthesis, viral protein production and glycosylation, and virus production. However, supplement of glucose-free cultures with uridine, ribose, or UDP-GlcNAc-metabolites that support upper glycolytic branches-resulted in partially restored viral genome synthesis and subsequent partial restoration of viral protein levels. Low levels of virus production were also restored. Supplementing lower glycolysis in glucose-free cultures using pyruvate had no effect on virus replication. These results indicate nutrients that support upper glycolytic branches like the pentose phosphate pathway and hexosamine pathway can compensate for glucose during HCMV replication to support low levels of virus production. More broadly, our findings suggest that HCMV could successfully replicate in diverse metabolic niches, including those in the body with low levels of glucose, through alternative nutrient usage.

UPP1 promotes lung adenocarcinoma progression through the induction of an immunosuppressive microenvironment

The complexity of the tumor microenvironment (TME) is a crucial factor in lung adenocarcinoma (LUAD) progression. To gain deeper insights into molecular mechanisms of LUAD, we perform an integrative single-cell RNA sequencing (scRNA-seq) data analysis of 377,574 cells from 117 LUAD patient samples. By linking scRNA-seq data with bulk gene expression data, we identify a cluster of prognostic-related UPP1high tumor cells. These cells, primarily situated at the invasive front of tumors, display a stronger association with the immunosuppressive components in the TME. Our cytokine array analysis reveals that the upregulation of UPP1 in tumor cells leads to the increased release of various immunosuppressive cytokines, with TGF-β1 being particularly prominent. Furthermore, this UPP1 upregulation also elevates the expression of PD-L1 through the PI3K/AKT/mTOR pathway, which contributes to the suppression of CD8 + T cells. Cytometry by time-of-flight (CyTOF) analysis provides additional evidence of the role of UPP1 in shaping the immunosuppressive nature of the TME. Using patient-derived organoids (PDOs), we discover that UPP1high tumors exhibit relatively increased sensitivity to Bosutinib and Dasatinib. Collectively, our study highlights the immunosuppressive role of UPP1 in LUAD, and these findings may provide insights into the molecular features of LUAD and facilitate the development of personalized treatment strategies.

Rethinking the Roles of Cancer-Associated Fibroblasts in Pancreatic Cancer

Bearing a dismal 5-year survival rate, pancreatic ductal adenocarcinoma (PDAC) is a challenging disease that features a unique fibroinflammatory tumor microenvironment. As major components of the PDAC tumor microenvironment, cancer-associated fibroblasts are still poorly understood and their contribution to the several hallmarks of PDAC, such as resistance to therapies, immunosuppression, and high incidence of metastasis, is likely underestimated. There have been encouraging advances in the understanding of these fascinating cells, but many controversies remain, leaving the field still actively exploring the full scope of their contributions in PDAC progression. Here we pose several important considerations regarding PDAC cancer-associated fibroblast functions. We posit that transcriptomic analyses be interpreted with caution, when aiming to uncover the functional contributions of these cells. Moreover, we propose that normalizing these functions, rather than eliminating them, will provide the opportunity to enhance therapeutic response. Finally, we propose that cancer-associated fibroblasts should not be studied in isolation, but in conjunction with its extracellular matrix, because their respective functions are coordinated and concordant.

UPP1 enhances bladder cancer progression and gemcitabine resistance through AKT

UPP1, a crucial pyrimidine metabolism-related enzyme, catalyzes the reversible phosphorylation of uridine to uracil and ribose-1-phosphate. However, the effects of UPP1 in bladder cancer (BLCA) have not been elucidated. AKT, which is activated mainly through dual phosphorylation (Thr308 and Ser473), promotes tumorigenesis by phosphorylating downstream substrates. This study demonstrated that UPP1 promotes BLCA cell proliferation, migration, invasion, and gemcitabine resistance by activating the AKT signaling pathway in vitro and in vivo. Additionally, UPP1 promoted AKT activation by facilitating the binding of AKT to PDK1 and PDK2 and the recruitment of phosphatidylinositol 3,4,5-triphosphate to AKT. Moreover, the beneficial effects of UPP1 on BLCA tumorigenesis were mitigated upon UPP1 mutation with Arg94 or MK2206 treatment (AKT-specific inhibitor). AKT overexpression or SC79 (AKT-specific activator) treatment restored tumor malignancy and drug resistance. Thus, this study revealed that UPP1 is a crucial oncogene and a potential therapeutic target for BLCA and that UPP1 activates the AKT signaling pathway and enhances tumorigenesis and drug resistance to gemcitabine.

N-acetylaspartate from fat cells regulates postprandial body temperature

N-acetylaspartate (NAA), the brain's second most abundant metabolite, provides essential substrates for myelination through its hydrolysis. However, activities and physiological roles of NAA in other tissues remain unknown. Here, we show aspartoacylase (ASPA) expression in white adipose tissue (WAT) governs systemic NAA levels for postprandial body temperature regulation. Proteomics and mass spectrometry revealed NAA accumulation in WAT of Aspa knockout mice stimulated the pentose phosphate pathway and pyrimidine production. Stable isotope tracing confirmed higher incorporation of glucose-derived carbon into pyrimidine metabolites in Aspa knockout cells. Additionally, serum NAA positively correlates with the pyrimidine intermediate orotidine and this relationship predicted lower body mass index in humans. Using whole-body and tissue-specific knockout mouse models, we demonstrate that fat cells provided plasma NAA and suppressed postprandial body temperature elevation. Furthermore, exogenous NAA supplementation reduced body temperature. Our study unveils WAT-derived NAA as an endocrine regulator of postprandial body temperature and physiological homeostasis.

Integrative Analyses of Pyrimidine Salvage Pathway-Related Genes Revealing the Associations Between UPP1 and Tumor Microenvironment

Background

The pyrimidine salvage pathway plays a critical role in tumor progression and patient outcomes. The roles of pyrimidine salvage pathway-related genes (PSPGs) in cancer, however, are not fully understood. This study aims to depict the characteristics of PSPGs across various cancers.

Methods

An integrative pan-cancer analysis of six PSPGs (CDA, UCK1, UCK2, UCKL1, UPP1, and UPP2) was conducted using TCGA data, single-cell RNA sequencing datasets, and patient samples. Single-cell transcriptome analysis and RT-qPCR were used to validate the relation between UPP1 and cytokines. Flow cytometry was performed to validate the role of UPP1 in immune checkpoint regulation. The correlation between UPP1 and tumor associated neutrophils (TAN) were investigated and validated by single-cell transcriptome analysis and tissue microarrays (TMAs).

Results

PSPGs showed low mutation rates but significant copy number variations, particularly amplifications in UCKL1, UPP1, and UCK2 across various cancers. DNA methylation patterns varied, with notable negative correlations between methylation and gene expression in UPP1. PSPGs were broadly up-regulated in multiple cancers, with correlations to clinical staging and prognosis. Proteomic data further confirmed these findings. Functional analysis revealed PSPGs' associations with tumor proliferation, metastasis, and various signaling pathways. UPP1 showed strong correlations with the tumor microenvironment (TME), particularly with cytokines, immune checkpoints, and various immune cells. Single-cell transcriptome analysis confirmed these associations, highlighting UPP1's influence on cytokine expression and immune checkpoint regulation. In esophageal squamous cell carcinoma (ESCC), UPP1-high tumor cells were significantly associated with immunosuppressive cells in the TME. Spatial analysis using TMAs revealed that UPP1+ tumor cells were predominantly located at the invasive margin and closely associated with neutrophils, correlating with poorer patient prognosis.

Conclusion

Our study depicted the multi-dimensional view of PSPGs in cancer, with a particular focus on UPP1's role in the TME. Targeting UPP1 holds promise as a potential strategy for cancer therapy.

Serum Metabolomics of Retinoblastoma: Assessing the Differential Serum Metabolic Signatures of Unilateral and Bilateral Patients

Retinoblastoma (Rb) is the most common pediatric eye cancer. To identify the biomarkers for early diagnosis and monitoring the progression of Rb in patients, mapping of the alterations in their metabolic profiles is essential. The present study aims at exploring the metabolic disparity in serum from Rb patients and controls using NMR-based metabolomics. A total of 72 metabolites, including carbohydrates, amino acids, and organic acids, were quantified in serum samples from 24 Rb patients and 26 controls. Distinct clusters of Rb patients and controls were obtained using the partial least-squares discriminant analysis (PLS-DA) model. Further, univariate and multivariate analyses of unilateral and bilateral Rb patients with respect to their age-matched controls depicted their distinct metabolic fingerprints. Metabolites including 2-phosphoglycerate, 4-aminobutyrate, proline, O-phosphocholine, O-phosphoethanolamine, and Sn-glycero-3-phosphocholine (Sn-GPC) showed significant perturbation in both unilateral and bilateral Rb patients. However, metabolic differences among the bilateral Rb cases were more pronounced than those in unilateral Rb cases with respect to controls. In addition to major discriminatory metabolites for Rb, unilateral and bilateral Rb cases showed specific metabolic changes, which might be the result of their differential genetic/somatic mutational backgrounds. This further suggests that the aberrant metabolic perturbation in bilateral patients signifies the severity of the disease in Rb patients. The present study demonstrated that identified serum metabolites have potential to serve as a noninvasive method for detection of Rb, discriminate bilateral from unilateral Rb patients, and aid in better understanding of the RB tumor biology.

Nucleotide metabolism in the regulation of tumor microenvironment and immune cell function

Nucleotide metabolism plays a crucial role in the regulation of the tumor microenvironment (TME) and immune cell function. In the TME, limited availability of nucleotide precursors due to increased consumption by tumor cells and T cells affects both tumor development and immune function. Metabolic reprogramming in tumor cells favors pathways supporting growth and proliferation, including nucleotide synthesis. Additionally, extracellular nucleotides, such as ATP and adenosine, exhibit dual roles in modulating immune function and tumor cell survival. ATP stimulates antitumor immunity by activating purinergic receptors, while adenosine acts as a potent immunosuppressor. Targeting nucleotide metabolism in the TME holds immense promise for cancer therapy. Understanding the intricate relationship between nucleotide metabolism, the TME, and immune responses will pave the way for innovative therapeutic interventions.

Multivariate modeling of metabolic state vulnerabilities across diverse cancer contexts reveals synthetically lethal associations

Targeting the distinct metabolic needs of tumor cells has recently emerged as a promising strategy for cancer therapy. The heterogeneous, context-dependent nature of cancer cell metabolism, however, poses challenges in identifying effective therapeutic interventions. Here, we utilize various unsupervised and supervised multivariate modeling approaches to systematically pinpoint recurrent metabolic states within hundreds of cancer cell lines, elucidate their association with tissue lineage and growth environments, and uncover vulnerabilities linked to their metabolic states across diverse genetic and tissue contexts. We validate key findings using data from an independent set of cell lines, pharmacological screens, and via single-cell analysis of patient-derived tumors. Our analysis uncovers new synthetically lethal associations between the tumor metabolic state (e.g., oxidative phosphorylation), driver mutations (e.g., loss of tumor suppressor PTEN), and actionable biological targets (e.g., mitochondrial electron transport chain). Investigating these relationships could inform the development of more precise and context-specific, metabolism-targeted cancer therapies.

The clinical terrain of immunotherapies in heterogeneous pancreatic cancer: unravelling challenges and opportunities

Pancreatic ductal adenocarcinoma (PDAC) is the most common and aggressive type of pancreatic cancer and has abysmal survival rates. In the past two decades, immunotherapeutic agents with success in other cancer types have gradually been trialled against PDACs at different stages of cancer progression, either as a monotherapy or in combination with chemotherapy. Unfortunately, to this day, chemotherapy still prolongs the survival rates the most and is prescribed in clinics despite the severe side effects in other cancer types. The low success rates of immunotherapy against PDAC have been attributed most frequently to its complex and multi-faceted tumour microenvironment (TME) and low mutational burden. In this review, we give a comprehensive overview of the immunotherapies tested in PDAC clinical trials thus far, their limitations, and potential explanations for their failure. We also discuss the existing classification of heterogenous PDACs into cancer, cancer-associated fibroblast, and immune subtypes and their potential opportunity in patient selection as a form of personalisation of PDAC immunotherapy. © 2023 The Pathological Society of Great Britain and Ireland.

Salvage of ribose from uridine or RNA supports glycolysis in nutrient-limited conditions

Glucose is vital for life, serving as both a source of energy and carbon building block for growth. When glucose is limiting, alternative nutrients must be harnessed. To identify mechanisms by which cells can tolerate complete loss of glucose, we performed nutrient-sensitized genome-wide genetic screens and a PRISM growth assay across 482 cancer cell lines. We report that catabolism of uridine from the medium enables the growth of cells in the complete absence of glucose. While previous studies have shown that uridine can be salvaged to support pyrimidine synthesis in the setting of mitochondrial oxidative phosphorylation deficiency1, our work demonstrates that the ribose moiety of uridine or RNA can be salvaged to fulfil energy requirements via a pathway based on: (1) the phosphorylytic cleavage of uridine by uridine phosphorylase UPP1/UPP2 into uracil and ribose-1-phosphate (R1P), (2) the conversion of uridine-derived R1P into fructose-6-P and glyceraldehyde-3-P by the non-oxidative branch of the pentose phosphate pathway and (3) their glycolytic utilization to fuel ATP production, biosynthesis and gluconeogenesis. Capacity for glycolysis from uridine-derived ribose appears widespread, and we confirm its activity in cancer lineages, primary macrophages and mice in vivo. An interesting property of this pathway is that R1P enters downstream of the initial, highly regulated steps of glucose transport and upper glycolysis. We anticipate that 'uridine bypass' of upper glycolysis could be important in the context of disease and even exploited for therapeutic purposes.