SLC25A1 promotes tumor growth and survival by reprogramming energy metabolism in colorectal cancer

Hypoxia-induced BNIP3 facilitates the progression and metastasis of uveal melanoma by driving metabolic reprogramming

Uveal melanoma (UM) is an aggressive intraocular malignancy derived from melanocytes in the uvea tract of the eye. Up to 50% of patients with UM develop distant metastases which is usually fatal within one year; preventing metastases is therefore essential. Metabolic reprogramming plays a critical role in UM progression and metastasis. However, the metabolic phenotype of UM cells in the hypoxic tumor is not well understood. Here, we report that hypoxia-induced BNIP3 reprograms tumor cell metabolism, promoting their survival and metastasis. In response to hypoxia, BNIP3-mediated mitophagy alleviates mitochondrial dysfunction and enhances mitochondrial oxidative phosphorylation (OXPHOS) while simultaneously reducing mitochondrial reactive oxygen species (mtROS) production. This, in turn, impairs HIF1A/HIF-1α protein stability and inhibits glycolysis. Inhibition of mitophagy significantly suppresses BNIP3-induced UM progression and metastasis in vitro and in vivo. Collectively, these observations demonstrate a novel mechanism whereby BNIP3 promotes UM metabolic reprogramming and malignant progression by mediating hypoxia-induced mitophagy and suggest that BNIP3 could be an important therapeutic target to prevent metastasis in patients with UM.Abbreviations: AOD: average optical density; BNIP3: BCL2/adenovirus E1B interacting protein 3; CQ: chloroquine; CoCl2: cobalt chloride; GEPIA: Gene Expression Profiling Interactive Analysis; HIF1A: hypoxia inducible factor 1, alpha subunit; IHC: immunohistochemistry; mtROS: mitochondrial reactive oxygen species; NAC: N-acetylcysteine; OCR: oxygen consumption rate; OXPHOS: oxidative phosphorylation; ROS: reactive oxygen species; TCGA: The Cancer Genome Atlas; UM: uveal melanoma.

Metabolic Control During Macrophage Polarization by a Citrate-Functionalized Scaffold for Maintaining Bone Homeostasis

Metabolites, as markers of phenotype at the molecular level, can regulate the function of DNA, RNA, and proteins through chemical modifications or interactions with large molecules. Citrate is an important metabolite that affects macrophage polarization and osteoporotic bone function. Therefore, a better understanding of the precise effect of citrate on macrophage polarization may provide an effective alternative strategy to reverse osteoporotic bone metabolism. In this study, a citrate functional scaffold to control the metabolic pathway during macrophage polarization based on the metabolic differences between pro-inflammatory and anti-inflammatory phenotypes for maintaining bone homeostasis, is fabricated. Mechanistically, only outside M1 macrophages are accumulated high concentrations of citrate, in contrast, M2 macrophages consume massive citrate. Therefore, citrate-functionalized scaffolds exert more sensitive inhibitory effects on metabolic enzyme activity during M1 macrophage polarization than M2 macrophage polarization. Citrate can block glycolysis-related enzymes by occupying the binding-site and ensure sufficient metabolic flux in the TCA cycle, so as to turn the metabolism of macrophages to oxidative phosphorylation of M2 macrophage, largely maintaining bone homeostasis. These studies indicate that exogenous citrate can realize metabolic control of macrophage polarization for maintaining bone homeostasis in osteoporosis.

Inhibiting mitochondrial citrate shuttling induces hepatic triglyceride deposition in Nile tilapia (Oreochromis niloticus) through lipid anabolic remodeling

The solute carrier family 25 member 1 (Slc25a1)-dependent mitochondrial citrate shuttle is responsible for exporting citrate from the mitochondria to the cytoplasm for supporting lipid biosynthesis and protein acetylation. Previous studies on Slc25a1 concentrated on pathological models. However, the importance of Slc25a1 in maintaining metabolic homeostasis under normal nutritional conditions remains poorly understood. Here, we investigated the mechanism of mitochondrial citrate shuttle in maintaining lipid metabolism homeostasis in male Nile tilapia (Oreochromis niloticus). To achieve the objective, we blocked the mitochondrial citrate shuttle by inhibiting Slc25a1 under normal nutritional conditions. Slc25a1 inhibition was established by feeding Nile tilapia with 250 mg/kg 1,2,3-benzenetricarboxylic acid hydrate for 6 weeks or intraperitoneal injecting them with dsRNA to knockdown slc25a1b for 7 days. The Nile tilapia with Slc25a1 inhibition exhibited an obesity-like phenotype accompanied by fat deposition, liver damage and hyperglycemia. Moreover, Slc25a1 inhibition decreased hepatic citrate-derived acetyl-CoA, but increased hepatic triglyceride levels. Furthermore, Slc25a1 inhibition replenished cytoplasmic acetyl-CoA through enhanced acetate pathway, which led to hepatic triglycerides accumulation. However, acetate-derived acetyl-CoA caused by hepatic Slc25a1 inhibition did not activate de novo lipogenesis, but rather modified protein acetylation. In addition, hepatic Slc25a1 inhibition enhanced fatty acids esterification through acetate-derived acetyl-CoA, which increased Lipin1 acetylation and its protein stability. Collectively, our results illustrate that inhibiting mitochondrial citrate shuttle triggers lipid anabolic remodeling and results in lipid accumulation, indicating the importance of mitochondrial citrate shuttle in maintaining lipid metabolism homeostasis.

Cell type-specific molecular mechanisms and implications of necroptosis in inflammatory respiratory diseases

Necroptosis is generally considered as an inflammatory cell death form. The core regulators of necroptotic signaling are receptor-interacting serine-threonine protein kinases 1 (RIPK1) and RIPK3, and the executioner, mixed lineage kinase domain-like pseudokinase (MLKL). Evidence demonstrates that necroptosis contributes profoundly to inflammatory respiratory diseases that are common public health problem. Necroptosis occurs in nearly all pulmonary cell types in the settings of inflammatory respiratory diseases. The influence of necroptosis on cells varies depending upon the type of cells, tissues, organs, etc., which is an important factor to consider. Thus, in this review, we briefly summarize the current state of knowledge regarding the biology of necroptosis, and focus on the key molecular mechanisms that define the necroptosis status of specific cell types in inflammatory respiratory diseases. We also discuss the clinical potential of small molecular inhibitors of necroptosis in treating inflammatory respiratory diseases, and describe the pathological processes that engage cross talk between necroptosis and other cell death pathways in the context of respiratory inflammation. The rapid advancement of single-cell technologies will help understand the key mechanisms underlying cell type-specific necroptosis that are critical to effectively treat pathogenic lung infections and inflammatory respiratory diseases.

The immunometabolic ecosystem in cancer

Our increased understanding of how key metabolic pathways are activated and regulated in malignant cells has identified metabolic vulnerabilities of cancers. Translating this insight to the clinics, however, has proved challenging. Roadblocks limiting efficacy of drugs targeting cancer metabolism may lie in the nature of the metabolic ecosystem of tumors. The exchange of metabolites and growth factors between cancer cells and nonmalignant tumor-resident cells is essential for tumor growth and evolution, as well as the development of an immunosuppressive microenvironment. In this Review, we will examine the metabolic interplay between tumor-resident cells and how targeted inhibition of specific metabolic enzymes in malignant cells could elicit pro-tumorigenic effects in non-transformed tumor-resident cells and inhibit the function of tumor-specific T cells. To improve the efficacy of metabolism-targeted anticancer strategies, a holistic approach that considers the effect of metabolic inhibitors on major tumor-resident cell populations is needed.

A comprehensive analysis of SLC25A1 expression and its oncogenic role in pan-cancer

OBJECTIVE

The solute carrier family 25 member 1 (SLC25A1) is currently the only known human transporter for citrate in the mitochondrial membrane. However, its role in cancer development remains to be elucidated. We aim to analyze the expression profile, prognostic value, potential immunological significance, and effect on tumor growth of SLC25A1 at a pan-cancer level.

METHODS

Herein, the role of SLC25A1 in tumorigenesis and progression was investigated based on the Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO), Genotype-Tissue Expression (GTEx), Clinical Proteomic Tumor Analysis Consortium (CPTAC), GeneMANIA, STRING and Cancer Dependency Map Project (DepMap) database via online websites or the R software. The protein expression levels were validated in tissue microarrays, and the effects on tumor cell lines were accessed through MTS and colony formation assays.

RESULTS

The expression of SLC25A1 increased in most cancers, and the upregulation of SLC25A1 in colon adenocarcinoma and lung adenocarcinoma was further confirmed by immunohistochemistry. Meanwhile, SLC25A1 was linked to clinical outcomes across multiple tumor types, particularly in lung adenocarcinoma, where its high expression predicted poor prognosis. Moreover, SLC25A1 was positively associated with MSI, TMB, and CD276 and tightly correlated with tumor-infiltrating immune cells. Furthermore, the knockout of SLC25A1 demonstrated inhibitory effects in most cancer cell lines in the DepMap project. Cellular experiments showed that SLC25A1 knockdown significantly reduced the proliferation of lung adenocarcinoma cells.

CONCLUSIONS

Our findings suggest the potential of SLC25A1 as a prognostic biomarker for cancers and a therapeutic target for precise antitumor strategy and cancer immunotherapy.

Pan-tissue mitochondrial phenotyping reveals lower OXPHOS expression and function across cancer types

Targeting mitochondrial oxidative phosphorylation (OXPHOS) to treat cancer has been hampered due to serious side-effects potentially arising from the inability to discriminate between non-cancerous and cancerous mitochondria. Herein, comprehensive mitochondrial phenotyping was leveraged to define both the composition and function of OXPHOS across various murine cancers and compared to both matched normal tissues and other organs. When compared to both matched normal tissues, as well as high OXPHOS reliant organs like heart, intrinsic expression of the OXPHOS complexes, as well as OXPHOS flux were discovered to be consistently lower across distinct cancer types. Assuming intrinsic OXPHOS expression/function predicts OXPHOS reliance in vivo, these data suggest that pharmacologic blockade of mitochondrial OXPHOS likely compromises bioenergetic homeostasis in healthy oxidative organs prior to impacting tumor mitochondrial flux in a clinically meaningful way. Although these data caution against the use of indiscriminate mitochondrial inhibitors for cancer treatment, considerable heterogeneity was observed across cancer types with respect to both mitochondrial proteome composition and substrate-specific flux, highlighting the possibility for targeting discrete mitochondrial proteins or pathways unique to a given cancer type.

Reduced 2,4-dienoyl-CoA reductase 1 is served as an unfavorable biomarker and is related to immune infiltration in cervical cancer

BACKGROUND

Worldwide, cervical cancer (CC) remains the most prevalent malignancy of the female reproductive system, posing a threat to women's life and health, and increasing the medical and economic burden on society. Therefore, the search for tumor biomarkers for CC remains an important research direction. Immunotherapy has significantly improved patient outcomes, and genes related to tumor immune infiltration have been clinically relevant and highly reproducible biomarkers that affect the prognosis and response to treatment of CC. 2,4-dienoyl-CoA reductase 1 (DECR1) was considered to be an oncogene in a previous study, but relationship between DECR1 and immune infiltration was not mentioned. Our study aimed to reveal the clinical value of DECR1 in CC and to investigate its relationship with immune infiltration.

METHODS

Human Protein Atlas was used to identify the localization of DECR1. The Ualcan database, TCGA, and IHC were used to assess the prognostic value of DECR1. GSEA was used to assess the possible signaling pathways of DECR1 in CC. The TIMER database was applied to reveal the relevance between DECR1 and immune infiltration. GEPIA was conducted to detect the co-relationship among DECR1, immune markers, and typical molecules of apoptosis.

RESULTS

DECR1 was mainly distributed in the cytoplasm and overlapped with the endoplasmic reticulum. DECR1 was downregulated in CC compared to adjacent tissue. Survival analysis showed that patients with lower expression of DECR1 have a worse prognosis in CC. GSEA suggested that DECR1 was closely related to apoptosis signaling. TIMER showed that DECR1 was positively correlated with CD8+ T cell and CD4+ T cell but not with B cell in CC.

CONCLUSION

DECR1 may be a potential cancer suppressor in CC and may be involved in apoptotic pathways and associated with immune infiltration.

A novel SLC25A1 inhibitor, parthenolide, suppresses the growth and stemness of liver cancer stem cells with metabolic vulnerability

Liver cancer stem cells (LCSCs) are recognized as key contributors to hepatocarcinogenesis, progression, and recurrence. Consequently, eradicating LCSCs has a great chance of increasing long-term survival in patients with liver cancer. Parthenolide (PTL), a natural sesquiterpene lactone product, possesses robust antitumor activity. However, the effects of PTL on LCSCs and underlying mechanisms remain unknown. Here we show that administration of PTL stimulated cell cycle arrest at the G1 phase, induced apoptosis, and decreased the stemness of LCSCs. Further research indicates that PTL caused the production of ROS and the reduction of oxidative phosphorylation (OXPHOS) and mitochondrial membrane potential (MMP) levels of LCSCs. RNA sequencing (RNA-Seq) further shows that PTL decreased SLC25A1 expression at the mRNA level and that inhibition of SLC25A1 synergistically decreased the expression of IDH2 and several pivotal genes involved in mitochondrial respiratory chain complex, resulting in the production of ROS and mitochondrial dysfunction. In addition, the inhibitory effect of PTL on mitochondrial function and self-renewal capacity of LCSCs was abolished by the knockdown of SLC25A1 or treatment with SLC25A1 inhibitor CTPI-2. Importantly, PTL prevented liver cancer growth in vivo without clearly causing toxicity. Our research shows that PTL inhibits the growth and stemness of LCSCs through SLC25A1-mediated mitochondrial function. PTL may be a potential candidate natural agent for liver cancer treatment.

Multiomics data analyses to identify SLC25A17 as a novel biomarker to predict the prognosis and immune microenvironment in head and neck squamous cell carcinoma

OBJECTIVE

This study aims to explore the predictive value of SLC25A17 in the prognosis and tumor microenvironment (TME) of patients with head and neck squamous cell carcinoma (HNSCC) and to provide ideas for individual clinical treatment.

METHODS

A pancancer analysis of the differential expression of SLC25A17 among different tumors was first conducted via the TIMER 2.0 database. Subsequently, the expression of SLC25A17 and related clinical information of HNSCC patients were obtained from the TCGA database, and patients were divided into two groups according to the median value of SLC25A17 expression. K‒M survival analysis was conducted to compare the overall survival (OS) and progression-free survival (PFS) between the groups. The Wilcoxon test was used to compare the distribution of SLC25A17 in different clinical characteristics, and univariate Cox and multivariate Cox analyses were performed to analyze independent prognostic factors to establish a predictive nomogram. Calibration curves were generated to verify the reliability of predicting 1-year, 3-year and 5-year survival rates and another cohort (GSE65858) was used for external validation. Gene set enrichment analysis was conducted to compare the enriched pathways, and the immune microenvironment was assessed using the CIBERSORT and estimate packages. Furthermore, the expression levels of SLC25A17 in immune cells were also analyzed with single-cell RNA-seq via the TISCH. Moreover, the immunotherapeutic response and chemotherapy drug sensitivity were compared between the two groups to guide precise treatment. The TIDE database was applied to predict the possibility of immune escape in the TCGA-HNSC cohort.

RESULTS

Compared with normal samples, the expression of SLC25A17 was much higher in HNSCC tumor samples. For patients with high SLC25A17 expression, the OS and PFS were shorter than those with low SLC25A17 expression, indicating a worse prognosis. The expression of SLC25A17 varied in different clinical features. Univariate Cox and multivariate COX analyses showed that SLC25A17, age, and lymph node metastasis are independent prognostic risk factors for HNSCC, and the survival prediction model based on these factors had reliable predictive value. Patients in the low-expression group exhibited more immune cell infiltration, higher TME scores, higher IPS scores and lower TIDE scores than those in the high-expression groups, suggesting better immunotherapeutic response with lower SLC25A17 expression. Moreover, patients in the high-expression group were more sensitive to chemotherapy.

CONCLUSIONS

SLC25A17 can effectively predict the prognosis of HNSCC patients and could be a precise individual-targeted indicator for the treatment of HNSCC patients.

FABP5 suppresses colorectal cancer progression via mTOR-mediated autophagy by decreasing FASN expression

Lipid metabolism plays an important role in the occurrence and development of cancer, in particular, digestive system tumors such as colon cancer. Here, we investigated the role of the fatty acid-binding protein 5 (FABP5) in colorectal cancer (CRC). We observed marked down-regulation of FABP5 in CRC. Data from functional assays revealed inhibitory effects of FABP5 on cell proliferation, colony formation, migration, invasion as well as tumor growth in vivo. In terms of mechanistic insights, FABP5 interacted with fatty acid synthase (FASN) and activated the ubiquitin proteasome pathway, leading to a decrease in FASN expression and lipid accumulation, moreover, suppressing mTOR signaling and facilitating cell autophagy. Orlistat, a FASN inhibitor, exerted anti-cancer effects both in vivo and in vitro. Furthermore, the upstream RNA demethylase ALKBH5 positively regulated FABP5 expression via an m⁶A-independent mechanism. Overall, our collective findings offer valuable insights into the critical role of the ALKBH5/FABP5/FASN/mTOR axis in tumor progression and uncover a potential mechanism linking lipid metabolism to development of CRC, providing novel therapeutic targets for future interventions.

Single-molecule methylation profiles of cell-free DNA in cancer with nanopore sequencing

Epigenetic characterization of cell-free DNA (cfDNA) is an emerging approach for detecting and characterizing diseases such as cancer. We developed a strategy using nanopore-based single-molecule sequencing to measure cfDNA methylomes. This approach generated up to 200 million reads for a single cfDNA sample from cancer patients, an order of magnitude improvement over existing nanopore sequencing methods. We developed a single-molecule classifier to determine whether individual reads originated from a tumor or immune cells. Leveraging methylomes of matched tumors and immune cells, we characterized cfDNA methylomes of cancer patients for longitudinal monitoring during treatment.

Crosstalk between oxidative phosphorylation and immune escape in cancer: a new concept of therapeutic targets selection

BACKGROUND

Cancer is increasingly recognized as a metabolic disease, with evidence suggesting that oxidative phosphorylation (OXPHOS) plays a significant role in the progression of numerous cancer cells. OXPHOS not only provides sufficient energy for tumor tissue survival but also regulates conditions for tumor proliferation, invasion, and metastasis. Alterations in OXPHOS can also impair the immune function of immune cells in the tumor microenvironment, leading to immune evasion. Therefore, investigating the relationship between OXPHOS and immune escape is crucial in cancer-related research. This review aims to summarize the effects of transcriptional, mitochondrial genetic, metabolic regulation, and mitochondrial dynamics on OXPHOS in different cancers. Additionally, it highlights the role of OXPHOS in immune escape by affecting various immune cells. Finally, it concludes with an overview of recent advances in antitumor strategies targeting both immune and metabolic processes and proposes promising therapeutic targets by analyzing the limitations of current targeted drugs.

CONCLUSIONS

The metabolic shift towards OXPHOS contributes significantly to tumor proliferation, progression, metastasis, immune escape, and poor prognosis. A thorough investigation of concrete mechanisms of OXPHOS regulation in different types of tumors and the combination usage of OXPHOS-targeted drugs with existing immunotherapies could potentially uncover new therapeutic targets for future antitumor therapies.

Targeting Mitochondrial Metabolic Reprogramming as a Potential Approach for Cancer Therapy

Abnormal energy metabolism is a characteristic of tumor cells, and mitochondria are important components of tumor metabolic reprogramming. Mitochondria have gradually received the attention of scientists due to their important functions, such as providing chemical energy, producing substrates for tumor anabolism, controlling REDOX and calcium homeostasis, participating in the regulation of transcription, and controlling cell death. Based on the concept of reprogramming mitochondrial metabolism, a range of drugs have been developed to target the mitochondria. In this review, we discuss the current progress in mitochondrial metabolic reprogramming and summarized the corresponding treatment options. Finally, we propose mitochondrial inner membrane transporters as new and feasible therapeutic targets.

SLC25A1-associated prognostic signature predicts poor survival in acute myeloid leukemia patients

Background: Acute myeloid leukemia (AML) is a heterogeneous malignant disease. SLC25A1, the gene encoding mitochondrial carrier subfamily of solute carrier proteins, was reported to be overexpressed in certain solid tumors. However, its expression and value as prognostic marker has not been assessed in AML. Methods: We retrieved RNA profile and corresponding clinical data of AML patients from the Beat AML, TCGA, and TARGET databases (TARGET_AML). Patients in the TCGA cohort were well-grouped into two group based on SLC25A1 and differentially expressed genes were determined between the SLC25A1 high and low group. The expression of SLC25A1 was validated with clinical samples. The survival and apoptosis of two AML cell lines were analyzed with SLC25A1 inhibitor (CTPI-2) treatment. Cox and the least absolute shrinkage and selection operator (LASSO) regression analyses were applied to Beat AML database to identify SLC25A1-associated genes for the construction of a prognostic risk-scoring model. Survival analysis was performed by Kaplan-Meier and receiver operator characteristic curves. Results: Our analysis revealed that high expressed level of SLC25A1 in AML patients correlates with unfavorable prognosis. Moreover, SLC25A1 expression was positively associated with metabolism activity. We further demonstrated that the inhibition of SLC25A1 could inhibit the proliferation and increase the apoptosis of AML cells. In addition, a panel of SLC25A1-associated genes, was identified to construct a prognostic risk-scoring model. This SLC25A1-associated prognostic signature (SPS) is an independent risk factor with high area under curve (AUC) values of receiver operating characteristic (ROC) curves. A high SPS in leukemia patients is associated with poor survival. A Prognostic nomogram including the SPS and other clinical parameters, was constructed and its predictive efficiency was confirmed. Conclusion: We have successfully established a SPS prognostic model that predict outcome and risk stratification in AML. This risk model can be used as an independent biomarker to assess prognosis of AML.

Mutational signature of mtDNA confers mechanistic insight into oxidative metabolism remodeling in colorectal cancer

Rationale: Mitochondrial dysfunction caused by mitochondrial DNA (mtDNA) mutations and subsequent metabolic defects are closely involved in tumorigenesis and progression in a cancer-type specific manner. To date, the mutational pattern of mtDNA somatic mutations in colorectal cancer (CRC) tissues and its clinical implication are still not completely clear. Methods: In the present study, we generated a large mtDNA somatic mutation dataset from three CRC cohorts (432, 1,015, and 845 patients, respectively) and then most comprehensively characterized the CRC-specific evolutionary pattern and its clinical implication. Results: Our results showed that the mtDNA control region (mtCTR) with a high mutation density exhibited a distinct mutation spectrum characterizing a high enrichment of L-strand C > T mutations, which was contrary to the H-strand C > T mutational bias observed in the mtDNA coding region (mtCDR) (P < 0.001). Further analysis clearly confirmed the relaxed evolutionary selection of mtCTR mutations, which was mainly characterized by the similar distribution of hypervariable region (HVS) and non-HVS mutation density. Moreover, significant negative selection was identified in mutations of mtDNA complex V (ATP6/ATP8) and tRNA loop regions. Although our data showed that oxidative metabolism was commonly increased in CRC cells, mtDNA somatic mutations in CRC tissues were not closely associated with mitochondrial biogenesis, oxidative metabolism, and clinical progression, suggesting a cancer-type specific relationship between mtDNA mutations and mitochondrial metabolic functions in CRC cells. Conclusion: Our study identified the CRC-specific evolutionary mode of mtDNA mutations, which is possibly matched to specific mitochondrial metabolic remodeling and confers new mechanic insight into CRC tumorigenesis.

Accumulation of oncometabolite D-2-Hydroxyglutarate by SLC25A1 inhibition: A metabolic strategy for induction of HR-ness and radiosensitivity

Oncogenic mutations in metabolic genes and associated oncometabolite accumulation support cancer progression but can also restrict cellular functions needed to cope with DNA damage. For example, gain-of-function mutations in isocitrate dehydrogenase (IDH) and the resulting accumulation of the oncometabolite D-2-hydroxyglutarate (D-2-HG) enhanced the sensitivity of cancer cells to inhibition of poly(ADP-ribose)-polymerase (PARP)1 and radiotherapy (RT). In our hand, inhibition of the mitochondrial citrate transport protein (SLC25A1) enhanced radiosensitivity of cancer cells and this was associated with increased levels of D-2-HG and a delayed repair of radiation-induced DNA damage. Here we aimed to explore the suggested contribution of D-2-HG-accumulation to disturbance of DNA repair, presumably homologous recombination (HR) repair, and enhanced radiosensitivity of cancer cells with impaired SLC25A1 function. Genetic and pharmacologic inhibition of SLC25A1 (SLC25A1i) increased D-2-HG-levels and sensitized lung cancer and glioblastoma cells to the cytotoxic action of ionizing radiation (IR). SLC25A1i-mediated radiosensitization was abrogated in MEFs with a HR-defect. D-2-HG-accumulation was associated with increased DNA damage and delayed resolution of IR-induced γH2AX and Rad51 foci. Combining SLC25A1i with PARP- or the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs)-inhibitors further potentiated IR-induced DNA damage, delayed DNA repair kinetics resulting in radiosensitization of cancer cells. Importantly, proof of concept experiments revealed that combining SLC25A1i with IR without and with PARPi also reduced tumor growth in the chorioallantoic membrane (CAM) model in vivo. Thereby SLC25A1i offers an innovative strategy for metabolic induction of context-dependent lethality approaches in combination with RT and clinically relevant inhibitors of complementary DNA repair pathways.

Multiple roles played by the mitochondrial citrate carrier in cellular metabolism and physiology

The citrate carrier (CIC) is an integral protein of the inner mitochondrial membrane which catalyzes the efflux of mitochondrial citrate (or other tricarboxylates) in exchange with a cytosolic anion represented by a tricarboxylate or a dicarboxylate or phosphoenolpyruvate. In this way, the CIC provides the cytosol with citrate which is involved in many metabolic reactions. Several studies have been carried out over the years on the structure, function and regulation of this metabolite carrier protein both in mammals and in many other organisms. A lot of data on the characteristics of this protein have therefore accumulated over time thereby leading to a complex framework of metabolic and physiological implications connected to the CIC function. In this review, we critically analyze these data starting from the multiple roles played by the mitochondrial CIC in many cellular processes and then examining the regulation of its activity in different nutritional and hormonal states. Finally, the metabolic significance of the citrate flux, mediated by the CIC, across distinct subcellular compartments is also discussed.

Emerging roles of fatty acid metabolism in cancer and their targeted drug development

Metabolic reprogramming is now considered as one of hallmark of tumor cells and provides them with a selective survival/growth advantage to resist harsh micro-environmental stress. Fatty acid (FA) metabolism of tumor cells supports the biosynthetic needs and provides fuel sources for energy supply. Since FA metabolic reprogramming is a critical link in tumor metabolism, its various roles in tumors have attracted increasing interest. Herein, we review the mechanisms through which cancer cells rewire their FA metabolism with a focus on the pathway of FA metabolism and its targeting drug development. The failure and successful cases of targeting tumor FA metabolism are expected to bypass the metabolic vulnerability and improve the efficacy of targeted therapy.