Acidosis Drives the Reprogramming of Fatty Acid Metabolism in Cancer Cells through Changes in Mitochondrial and Histone Acetylation

Regulation of cancer cell lipid metabolism and oxidative phosphorylation by microenvironmental acidosis

The expansion of cancer cell mass in solid tumors generates a harsh environment characterized by dynamically varying levels of acidosis, hypoxia, and nutrient deprivation. Because acidosis inhibits glycolytic metabolism and hypoxia inhibits oxidative phosphorylation, cancer cells that survive and grow in these environments must rewire their metabolism and develop a high degree of metabolic plasticity to meet their energetic and biosynthetic demands. Cancer cells frequently upregulate pathways enabling the uptake and utilization of lipids and other nutrients derived from dead or recruited stromal cells, and in particular lipid uptake is strongly enhanced in acidic microenvironments. The resulting lipid accumulation and increased reliance on β-oxidation and mitochondrial metabolism increase susceptibility to oxidative stress, lipotoxicity, and ferroptosis, in turn driving changes that may mitigate such risks. The spatially and temporally heterogeneous tumor microenvironment thus selects for invasive, metabolically flexible, and resilient cancer cells capable of exploiting their local conditions and of seeking out more favorable surroundings. This phenotype relies on the interplay between metabolism, acidosis, and oncogenic mutations, driving metabolic signaling pathways such as peroxisome proliferator-activated receptors (PPARs). Understanding the particular vulnerabilities of such cells may uncover novel therapeutic liabilities of the most aggressive cancer cells.

Sulforaphane reverses the enhanced NSCLC metastasis by regulating the miR-7-5p/c-Myc/LDHA axis in the acidic tumor microenvironment

BACKGROUND

The presence of distant metastasis at the time of initial diagnosis is a prevalent issue in non-small cell lung cancer (NSCLC), affecting around 30-40 % of the patients. Acidic tumor microenvironment (TME) provides favorable conditions that increase the invasiveness and aggressiveness of NSCLC. The activity of the glycolytic enzyme lactate dehydrogenase (LDHA) increases intracellular lactate accumulation, which creates an acidic TME. However, it is not yet known whether LDHA is involved in enhancing the metastatic potential of NSCLC and if LDHA is a druggable therapeutic target for NSCLC.

PURPOSE

We aimed to investigate the molecular mechanisms underlying the enhanced NSCLC metastasis in acidic TME, and to explore whether sulforaphane (SFN), an active compound in Raphani Semen, can serve as a LDHA inhibitor to inhibit NSCLC metastasis in the acidic TME.

METHODS

To mimic the acidic TME, NSCLC cells were cultured in acidic medium (pH 6.6), normal medium (pH 7.4) served as control. Western blotting, bioinformatic analysis, luciferase assay and rescue experiments were used to explore the mechanism and investigate the anti-metastatic effect of SFN both in vitro and in vivo.

RESULTS

Acidic environment increases the expression of LDHA which in turn increases the production of lactic acid that contributes to the acidity of TME. Interestingly, elevated LDHA expression results from increased c-Myc expression, which transactivates LDHA. c-Myc expression is directly regulated by miR-7-5p. In vitro study shows that overexpression of miR-7-5p reverses the acidic pH-enhanced c-Myc and LDHA expressions and also abolishes the enhanced NSCLC cell migration. More importantly, SFN significantly inhibits NSCLC growth and metastasis by reducing lactate production via the miR-7-5p/c-Myc/LDHA axis. Besides, it also regulates the expressions of monocarboxylate transporter 1 (MCT1) and MCT4 that transport lactate across cell membrane.

CONCLUSIONS

The miR-7-5p/c-Myc/LDHA axis is involved in the enhanced NSCLC metastasis in the acidic TME. SFN, a novel LDHA inhibitor, reduces lactate production by targeting the miR-7-5p/c-Myc/LDHA axis, and hence inhibits NSCLC metastasis. Our findings not only delineate a novel mechanism, but also support the clinical translation of SFN as a novel therapeutic agent for treating metastatic NSCLC.

Bridging the gap: advancing cancer cell culture to reveal key metabolic targets

Metabolic rewiring is a defining characteristic of cancer cells, driving their ability to proliferate. Leveraging these metabolic vulnerabilities for therapeutic purposes has a long and impactful history, with the advent of antimetabolites marking a significant breakthrough in cancer treatment. Despite this, only a few in vitro metabolic discoveries have been successfully translated into effective clinical therapies. This limited translatability is partially due to the use of simplistic in vitro models that do not accurately reflect the tumor microenvironment. This Review examines the effects of current cell culture practices on cancer cell metabolism and highlights recent advancements in establishing more physiologically relevant in vitro culture conditions and technologies, such as organoids. Applying these improvements may bridge the gap between in vitro and in vivo findings, facilitating the development of innovative metabolic therapies for cancer.

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.

Metabolic ripple effects - deciphering how lipid metabolism in cancer interfaces with the tumor microenvironment

Cancer cells require a constant supply of lipids. Lipids are a diverse class of hydrophobic molecules that are essential for cellular homeostasis, growth and survival, and energy production. How tumors acquire lipids is under intensive investigation, as these mechanisms could provide attractive therapeutic targets for cancer. Cellular lipid metabolism is tightly regulated and responsive to environmental stimuli. Thus, lipid metabolism in cancer is heavily influenced by the tumor microenvironment. In this Review, we outline the mechanisms by which the tumor microenvironment determines the metabolic pathways used by tumors to acquire lipids. We also discuss emerging literature that reveals that lipid availability in the tumor microenvironment influences many metabolic pathways in cancers, including those not traditionally associated with lipid biology. Thus, metabolic changes instigated by the tumor microenvironment have 'ripple' effects throughout the densely interconnected metabolic network of cancer cells. Given the interconnectedness of tumor metabolism, we also discuss new tools and approaches to identify the lipid metabolic requirements of cancer cells in the tumor microenvironment and characterize how these requirements influence other aspects of tumor metabolism.

Exploring the impact of flavin homeostasis on cancer cell metabolism

Flavins and their associated proteins have recently emerged as compelling players in the landscape of cancer biology. Flavins, encompassing flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), serve as coenzymes in a multitude of cellular processes, such as metabolism, apoptosis, and cell proliferation. Their involvement in oxidative phosphorylation, redox homeostasis, and enzymatic reactions has long been recognized. However, recent research has unveiled an extended role for flavins in the context of cancer. In parallel, riboflavin transporters (RFVTs), FAD synthase (FADS), and riboflavin kinase (RFK) have gained prominence in cancer research. These proteins, responsible for riboflavin uptake, FAD biosynthesis, and FMN generation, are integral components of the cellular machinery that governs flavin homeostasis. Dysregulation in the expression/function of these proteins has been associated with various cancers, underscoring their potential as diagnostic markers, therapeutic targets, and key determinants of cancer cell behavior. This review embarks on a comprehensive exploration of the multifaceted role of flavins and of the flavoproteins involved in nucleus-mitochondria crosstalk in cancer. We journey through the influence of flavins on cancer cell energetics, the modulation of RFVTs in malignant transformation, the diagnostic and prognostic significance of FADS, and the implications of RFK in drug resistance and apoptosis. This review also underscores the potential of these molecules and processes as targets for novel diagnostic and therapeutic strategies, offering new avenues for the battle against this relentless disease.

Nervonic acid triggered ovarian inflammation by inducing mitochondrial oxidative stress to activate NLRP3/ IL-1β pathway

INTRODUCTION

Metabolic syndrome is a serious public health concern across the globe. However, the typical metabolites and mechanisms underlying the decreased fertility related to metabolic syndrome is still elusive.

OBJECTIVES

The aim of the present study was to explore the typical metabolites and mechanisms underlying the decreased fertility related with metabolic syndrome.

METHODS

Utilizing metabolomics, a comparative analysis was conducted on fatty acid compositions in various tissues of sows with high and low reproductive performance. Additionally, serum fatty acid compositions in a metabolic syndrome model (obese mice) induced by a high-fat diet (HFD) were investigated to elucidate the lipid metabolites associated with metabolic syndrome. Furthermore, the impact of nervonic acid (NA) on ovarian function was examined using rodent animal models (rats and mice). Through biological techniques such as transcriptomics, CUT&Tag, and analysis of post-translational protein modifications, the molecular mechanisms underlying NA mediated ovarian inflammation were further elucidated based on models utilizing ovarian granulosa cells from pigs, humans, and mice. Finally, validation was performed on ovaries from patients diagnosed with polycystic ovary syndrome.

RESULTS

In vitro, targeted serum lipidomic analysis revealed that sows with low embryo survival rates exhibited abnormal lipid metabolism characterized by abnormal accumulation of NA in the liver, ovary, and adipose tissue. Additionally, elevated NA levels trigger ovarian inflammation to cause ovarian dysfunction in both sows and rats. Mechanistically, NA induce mitochondrial oxidative stress through inhibiting respiratory chain proteins CYTB and NDFUB8 to activate NLRP3 inflammasome, which triggers procaspase-1 into active caspase-1, and convert the cytokine precursors pro-IL-1β into biologically active IL-1β in ovarian granulosa cells. Notably, we evidenced that NA promotes IL-1β activities by increasing H3K9ac modification level of IL-1β promoter regions and regulating the expression of the transcription factor AP-1. Finally, we found that the decreased expression of CerS2 in ovaries and the increased level of chemokine CXCL14 may be the cause of abnormal NA accumulation. Surprisingly, individuals with polycystic ovary syndrome, obesity, non-alcoholic fatty liver or gestational diabetes mellitus exhibit a high level of serum NA.

CONCLUSION

Collectively, our current study suggests that NA is a typical metabolite of metabolic syndrome, which strongly influences the ovarian function and embryo survival and also provides that interfering with mitochondrial ROS production is a potential strong strategy for target solving abnormal NA accumulation.

The Emerging Roles of Hydrogen Sulfide in Ferroptosis

Significance: Ferroptosis, a form of regulated cell death characterized by a large amount of lipid peroxidation-mediated membrane damage, joins the evolution of multisystem diseases, for instance, neurodegenerative diseases, chronic obstructive pulmonary disease, acute respiratory distress syndrome, osteoporosis, osteoarthritis, and so forth. Since being identified as the third gasotransmitter in living organisms, the intricate role of hydrogen sulfide (H2S) in ferroptosis has emerged at the forefront of research. Recent Advances: Novel targets in the relevant metabolic pathways have been found, including transferrin receptor 1, cystine/glutamate antiporter, and others, coupled with the exploration of new signaling pathways, particularly the p53 signaling pathway, the nitric oxide/nuclear factor erythroid 2-related factor 2 signaling pathway, and so on. Many diseases such as emphysema and airway inflammation, myocardial diseases, endothelial dysfunction in aging arteries, and traumatic brain injury have recently been found to be alleviated directly by H2S inhibition of ferroptosis. Safe, effective, and tolerable novel H2S donors have been developed and have shown promising results in phase I clinical trials. Critical Issues: Complicated cross talk between the ferroptosis signaling pathway and oncogenic factors results in the risk of cancer when inhibiting ferroptosis. Notably, targeted delivery of H2S is still a challenging task. Future Directions: Discovering more reliable and stable novel H2S donors and achieving their targeted delivery will enable further clinical trials for diseases associated with ferroptosis inhibition by H2S, determining their safety, efficacy, and tolerance.

ASIC3-activated key enzymes of de novo lipid synthesis supports lactate-driven EMT and the metastasis of colorectal cancer cells

Acidic microenvironments is a cancer progression driver, unclear core mechanism hinders the discovery of new diagnostic or therapeutic targets. ASIC3 is an extracellular proton sensor and acid-sensitive, but its role in acidic tumor microenvironment of colorectal cancer is not reported. Functional analysis data show that colorectal cancer cells respond to specific concentration of lactate to accelerate invasion and metastasis, and ASIC3 is the main actor in this process. Mechanism reveal de novo lipid synthesis is a regulatory process of ASIC3, down-regulated ASIC3 increases and interacts with ACC1 and SCD1, which are key enzymes in de novo lipid synthesis pathway, this interaction results in increased unsaturated fatty acids, which in turn induce EMT to promote metastasis, and overexpression of ASIC3 reduces acidic TME-enhanced colorectal cancer metastasis. Clinical samples of colorectal cancer also exhibit decreased ASIC3 expression, and low ASIC3 expression is associated with metastasis and stage of colorectal cancer. This study is the first to identify the role of the ASIC3-ACC1/SCD1 axis in acid-enhanced colorectal cancer metastasis. The expression pattern of ASIC3 in colorectal cancer differs significantly from that in other types of cancers, ASIC3 may serve as a novel and reliable marker for acidic microenvironmental in colorectal cancer, and potentially a therapeutic target.

Intracellular acidification and glycolysis modulate inflammatory pathway in senescent cells

Senescent cells accumulate in various organs with ageing, and its accumulation induces chronic inflammation and age-related physiological dysfunctions. Several remodelling of intracellular environments have been identified in senescent cells, including enlargement of cell/nuclear size and intracellular acidification. Although these alterations of intracellular environments were reported to be involved in the unique characteristics of senescent cells, the contribution of intracellular acidification to senescence-associated cellular phenotypes is poorly understood. Here, we identified that the upregulation of TXNIP and its paralog ARRDC4 as a hallmark of intracellular acidification in addition to KGA-type GLS1. These genes were also upregulated in response to senescence-associated intracellular acidification. Neutralization of the intracellular acidic environment ameliorated not only senescence-related upregulation of TXNIP, ARRDC4 and KGA but also inflammation-related genes, possibly through suppression of PDK-dependent anaerobic glycolysis. Furthermore, we found that expression of the intracellular acidification-induced genes, TXNIP and ARRDC4, correlated with inflammatory gene expression in heterogeneous senescent cell population in vitro and even in vivo, implying that the contribution of intracellular pH to senescence-associated cellular features, such as SASP.

Acidity and hypoxia of tumor microenvironment, a positive interplay in extracellular vesicle release by tumor cells

The complex and continuously evolving features of the tumor microenvironment, varying between tumor histotypes, are characterized by the presence of host cells and tumor cells embedded in a milieu shaped by hypoxia and low pH, resulting from the frequent imbalance between vascularity and tumor cell proliferation. These microenvironmental metabolic stressors play a crucial role in remodeling host cells and tumor cells, contributing to the stimulation of cancer cell heterogeneity, clonal evolution, and multidrug resistance, ultimately leading to progression and metastasis. The extracellular vesicles (EVs), membrane-enclosed structures released into the extracellular milieu by tumor/host cells, are now recognized as critical drivers in the complex intercellular communication between tumor cells and the local cellular components in a hypoxic/acidic microenvironment. Understanding the intricate molecular mechanisms governing the interactions between tumor and host cells within a hypoxic and acidic microenvironment, triggered by the release of EVs, could pave the way for innovative strategies to disrupt the complex interplay of cancer cells with their microenvironment. This approach may contribute to the development of an efficient and safe therapeutic strategy to combat cancer progression. Therefore, we review the major findings on the release of EVs in a hypoxic/acidic tumor microenvironment to appreciate their role in tumor progression toward metastatic disease.

Modulation of mitochondrial function by extracellular acidosis in tumor cells and normal fibroblasts: Role of signaling pathways

In many tumors pronounced extracellular acidosis resulting from glycolytic metabolism is found. Since several environmental stress factors affect the mitochondrial activity the aim of the study was to analyze the impact of acidosis on cellular oxygen consumption and which signaling pathways may be involved in the regulation. In two tumor cell lines and normal fibroblasts cellular oxygen consumption rate (OCR) and mitochondrial function were measured after 3 h at pH 6.6. Besides the activation of ERK1/2, p38 and PI3K signaling in the cytosolic and mitochondrial compartment, the mitochondrial structure and proteins related to mitochondria fission were analyzed. The acidic extracellular environment increased OCR in tumor cells but not in fibroblasts. In parallel, the mitochondrial membrane potential increased at low pH. In both tumor lines (but not in fibroblasts), the phosphorylation of ERK1/2 and PI3K/Akt was significantly increased, and both cascades were involved in OCR modulation. The activation of signaling pathways was located predominantly in the mitochondrial compartment of the cells. At low pH, the mitochondrial structure in tumor cells showed structural changes related to elongation whereas mitochondria fragmentation was reduced indicating mitochondria fusion. However, these morphological changes were not related to ERK1/2 or PI3K signaling. Acidic stress seems to induce an increased oxygen consumption, which might further aggravate tumor hypoxia. Low pH also induces mitochondria fusion that is not mediated by ERK1/2 or PI3K signaling. The mechanism by which these signaling cascades modulate the respiratory activity of tumor cells needs further investigation.

The emerging role of lactate in tumor microenvironment and its clinical relevance

In recent years, the significant impact of lactate in the tumor microenvironment has been greatly documented. Acting not only as an energy substance in tumor metabolism, lactate is also an imperative signaling molecule. It plays key roles in metabolic remodeling, protein lactylation, immunosuppression, drug resistance, epigenetics and tumor metastasis, which has a tight relation with cancer patients' poor prognosis. This review illustrates the roles lactate plays in different aspects of tumor progression and drug resistance. From the comprehensive effects that lactate has on tumor metabolism and tumor immunity, the therapeutic targets related to it are expected to bring new hope for cancer therapy.

Palmitic Acid Exerts Anti-Tumorigenic Activities by Modulating Cellular Stress and Lipid Droplet Formation in Endometrial Cancer

Epidemiological and clinical evidence have extensively documented the role of obesity in the development of endometrial cancer. However, the effect of fatty acids on cell growth in endometrial cancer has not been widely studied. Here, we reported that palmitic acid significantly inhibited cell proliferation of endometrial cancer cells and primary cultures of endometrial cancer and reduced tumor growth in a transgenic mouse model of endometrial cancer, in parallel with increased cellular stress and apoptosis and decreased cellular adhesion and invasion. Inhibition of cellular stress by N-acetyl-L-cysteine effectively reversed the effects of palmitic acid on cell proliferation, apoptosis, and invasive capacity in endometrial cancer cells. Palmitic acid increased the intracellular formation of lipid droplets in a time- and dose-dependent manner. Depletion of lipid droplets by blocking DGAT1 and DGAT2 effectively increased the ability of palmitic acid to inhibit cell proliferation and induce cleaved caspase 3 activity. Collectively, this study provides new insight into the effect of palmitic acid on cell proliferation and invasion and the formation of lipid droplets that may have potential clinical relevance in the treatment of obesity-driven endometrial cancer.

Emerging roles of lactate in acute and chronic inflammation

Traditionally, lactate has been considered a 'waste product' of cellular metabolism. Recent findings have shown that lactate is a substance that plays an indispensable role in various physiological cellular functions and contributes to energy metabolism and signal transduction during immune and inflammatory responses. The discovery of lactylation further revealed the role of lactate in regulating inflammatory processes. In this review, we comprehensively summarize the paradoxical characteristics of lactate metabolism in the inflammatory microenvironment and highlight the pivotal roles of lactate homeostasis, the lactate shuttle, and lactylation ('lactate clock') in acute and chronic inflammatory responses from a molecular perspective. We especially focused on lactate and lactate receptors with either proinflammatory or anti-inflammatory effects on complex molecular biological signalling pathways and investigated the dynamic changes in inflammatory immune cells in the lactate-related inflammatory microenvironment. Moreover, we reviewed progress on the use of lactate as a therapeutic target for regulating the inflammatory response, which may provide a new perspective for treating inflammation-related diseases.

Targeting lipid reprogramming in the tumor microenvironment by traditional Chinese medicines as a potential cancer treatment

In the last ten years, there has been a notable rise in the study of metabolic abnormalities in cancer cells. However, compared to glucose or glutamine metabolism, less attention has been paid to the importance of lipid metabolism in tumorigenesis. Recent developments in lipidomics technologies have allowed for detailed analysis of lipid profiles within cancer cells and other cellular players present within the tumor microenvironment (TME). Traditional Chinese medicine (TCM) and its bioactive components have a long history of use in cancer treatments and are also being studied for their potential role in regulating metabolic reprogramming within TME. This review focuses on four core abnormalities altered by lipid reprogramming in cancer cells: de novo synthesis and exogenous uptake of fatty acids (FAs), upregulated fatty acid oxidation (FAO), cholesterol accumulation, which offer benefits for tumor growth and metastasis. The review also discusses how altered lipid metabolism impacts infiltrating immune cell function and phenotype as these interactions between cancer-stromal become more pronounced during tumor progression. Finally, recent literature is highlighted regarding how cancer cells can be metabolically reprogrammed by specific Chinese herbal components with potential therapeutic benefits related to lipid metabolic and signaling pathways.

Control of Inflammatory Response by Tissue Microenvironment

Inflammation is an essential defense response but operates at the cost of normal functions. Whether and how the negative impact of inflammation is monitored remains largely unknown. Acidification of the tissue microenvironment is associated with inflammation. Here we investigated whether macrophages sense tissue acidification to adjust inflammatory responses. We found that acidic pH restructured the inflammatory response of macrophages in a gene-specific manner. We identified mammalian BRD4 as a novel intracellular pH sensor. Acidic pH disrupts the transcription condensates containing BRD4 and MED1, via histidine-enriched intrinsically disordered regions. Crucially, decrease in macrophage intracellular pH is necessary and sufficient to regulate transcriptional condensates in vitro and in vivo, acting as negative feedback to regulate the inflammatory response. Collectively, these findings uncovered a pH-dependent switch in transcriptional condensates that enables environmental sensing to directly control inflammation, with a broader implication for calibrating the magnitude and quality of inflammation by the inflammatory cost.

Ferroptosis: a potential therapeutic target for stroke

Ferroptosis is a form of regulated cell death characterized by massive iron accumulation and iron-dependent lipid peroxidation, differing from apoptosis, necroptosis, and autophagy in several aspects. Ferroptosis is regarded as a critical mechanism of a series of pathophysiological reactions after stroke because of iron overload caused by hemoglobin degradation and iron metabolism imbalance. In this review, we discuss ferroptosis-related metabolisms, important molecules directly or indirectly targeting iron metabolism and lipid peroxidation, and transcriptional regulation of ferroptosis, revealing the role of ferroptosis in the progression of stroke. We present updated progress in the intervention of ferroptosis as therapeutic strategies for stroke in vivo and in vitro and summarize the effects of ferroptosis inhibitors on stroke. Our review facilitates further understanding of ferroptosis pathogenesis in stroke, proposes new targets for the treatment of stroke, and suggests that more efforts should be made to investigate the mechanism of ferroptosis in stroke.

Tumoral acidosis promotes adipose tissue depletion by fostering adipocyte lipolysis

OBJECTIVE

Tumour progression drives profound alterations in host metabolism, such as adipose tissue depletion, an early event of cancer cachexia. As fatty acid consumption by cancer cells increases upon acidosis of the tumour microenvironment, we reasoned that fatty acids derived from distant adipose lipolysis may sustain tumour fatty acid craving, leading to the adipose tissue loss observed in cancer cachexia.

METHODS

To evaluate the pro-lipolytic capacities of acid-exposed cancer cells, primary mouse adipocytes from subcutaneous and visceral adipose tissue were exposed to pH-matched conditioned medium from human and murine acid-exposed cancer cells (pH 6.5), compared to naive cancer cells (pH 7.4). To further address the role of tumoral acidosis on adipose tissue loss, a pH-low insertion peptide was injected into tumour-bearing mice, and tumoral acidosis was neutralised with a sodium bicarbonate buffer. Prolipolytic mediators were identified by transcriptomic approaches and validated on murine and human adipocytes.

RESULTS

Here, we reveal that acid-exposed cancer cells promote lipolysis from subcutaneous and visceral adipocytes and that dampening acidosis in vivo inhibits adipose tissue depletion. We further found a set of well-known prolipolytic factors enhanced upon acidosis adaptation and unravelled a role for β-glucuronidase (GUSB) as a promising new actor in adipocyte lipolysis.

CONCLUSIONS

Tumoral acidosis promotes the mobilization of fatty acids derived from adipocytes via the release of soluble factors by cancer cells. Our work paves the way for therapeutic approaches aimed at tackling cachexia by targeting the tumour acidic compartment.

Potential role of lipophagy impairment for anticancer effects of glycolysis-suppressed pancreatic ductal adenocarcinoma cells

Although increased aerobic glycolysis is common in various cancers, pancreatic ductal adenocarcinoma (PDAC) cells can survive a state of glycolysis suppression. We aimed to identify potential therapeutic targets in glycolysis-suppressed PDAC cells. By screening anticancer metabolic compounds, we identified SP-2509, an inhibitor of lysine-specific histone demethylase 1A (LSD1), which dramatically decreased the growth of PDAC PANC-1 cells and showed an anti-tumoral effect in tumor-bearing mice. The growth of glycolysis-suppressed PANC-1 cells was also inhibited by another LSD1 inhibitor, OG-L002. Similarly, the other two PDAC cells (PK-1 and KLM-1) with suppressed glycolysis exhibited anticancer effects against SP-2509. However, the anticancer effects on PDAC cells were unrelated to LSD1. To investigate how PDAC cells survive in a glycolysis-suppressed condition, we conducted proteomic analyses. These results combined with our previous findings suggested that glucose-starvation causes PDAC cells to enhance mitochondrial oxidative phosphorylation. In particular, mitochondrial fatty acid metabolism was identified as a key factor contributing to the survival of PDAC cells under glycolysis suppression. We further demonstrated that SP-2509 and OG-L002 disturbed fatty acid metabolism and induced lipid droplet accumulation through the impairment of lipophagy, but not bulk autophagy. These findings indicate a significant potential association of lipophagy and anticancer effects in glycolysis-suppressed PDAC cells, offering ideas for new therapeutic strategies for PDAC by dual inhibition of glycolysis and fatty acids metabolism.

Role of pH-sensing receptors in colitis

Low pH in the gut is associated with severe inflammation, fibrosis, and colorectal cancer (CRC) and is a hallmark of active inflammatory bowel disease (IBD). Subsequently, pH-sensing mechanisms are of interest for the understanding of IBD pathophysiology. Tissue hypoxia and acidosis-two contributing factors to disease pathophysiology-are linked to IBD, and understanding their interplay is highly relevant for the development of new therapeutic options. One member of the proton-sensing G protein-coupled receptor (GPCR) family, GPR65 (T-cell death-associated gene 8, TDAG8), was identified as a susceptibility gene for IBD in a large genome-wide association study. In response to acidic extracellular pH, GPR65 induces an anti-inflammatory response, whereas the two other proton-sensing receptors, GPR4 and GPR68 (ovarian cancer G protein-coupled receptor 1, OGR1), mediate pro-inflammatory responses. Here, we review the current knowledge on the role of these proton-sensing receptors in IBD and IBD-associated fibrosis and cancer, as well as colitis-associated cancer (CAC). We also describe emerging small molecule modulators of these receptors as therapeutic opportunities for the treatment of IBD.

Phenotypic screen of sixty-eight colorectal cancer cell lines identifies CEACAM6 and CEACAM5 as markers of acid resistance

Elevated cancer metabolism releases lactic acid and CO2 into the under-perfused tumor microenvironment, resulting in extracellular acidosis. The surviving cancer cells must adapt to this selection pressure; thus, targeting tumor acidosis is a rational therapeutic strategy to manage tumor growth. However, none of the major approved treatments are based explicitly on disrupting acid handling, signaling, or adaptations, possibly because the distinction between acid-sensitive and acid-resistant phenotypes is not clear. Here, we report pH-related phenotypes of sixty-eight colorectal cancer (CRC) cell lines by measuring i) extracellular acidification as a readout of acid production by fermentative metabolism and ii) growth of cell biomass over a range of extracellular pH (pHe) levels as a measure of the acid sensitivity of proliferation. Based on these measurements, CRC cell lines were grouped along two dimensions as "acid-sensitive"/"acid-resistant" versus "low metabolic acid production"/"high metabolic acid production." Strikingly, acid resistance was associated with the expression of CEACAM6 and CEACAM5 genes coding for two related cell-adhesion molecules, and among pH-regulating genes, of CA12. CEACAM5/6 protein levels were strongly induced by acidity, with a further induction under hypoxia in a subset of CRC lines. Lack of CEACAM6 (but not of CEACAM5) reduced cell growth and their ability to differentiate. Finally, CEACAM6 levels were strongly increased in human colorectal cancers from stage II and III patients, compared to matched samples from adjacent normal tissues. Thus, CEACAM6 is a marker of acid-resistant clones in colorectal cancer and a potential motif for targeting therapies to acidic regions within the tumors.

ACOT7 promotes retinoblastoma resistance to vincristine by regulating fatty acid metabolism reprogramming

The rate of vincristine (VCR) resistance in the treatment of retinoblastoma (RB) is relatively high, and the exact role and mechanism of autophagy and fatty acid (FA) metabolism in RB are still unknown. The aim of this study was to elucidate the molecular mechanism by which acyl-CoA thioesterase 7 (ACOT7) regulates FA metabolism and autophagy, which may lead to potential therapeutic strategies for RB. In the present study, the relationship between FA metabolism and cellular drug sensitivity was evaluated through ACOT7 overexpression or inhibition tests in RB-resistant cells. The lipase inhibitor orlistat and the autophagy inhibitor CQ were used to determine the effects of ACOT7 on FA metabolism, autophagy, and cellular drug sensitivity, as well as the therapeutic value of ACOT7 targeting. The results showed that ACOT7 was upregulated in VCR-resistant RB cells, significantly enhancing cell resistance and indicating that ACOT7 may serve as a biomarker for VCR resistance in RB cells. Knockdown of ACOT7 inhibited FA metabolism and reduced cell viability in VCR-resistant RB cells. The effect of ACOT7 overexpression was opposite to that of ACOT7 knockdown, and ACOT7 overexpression promoted autophagy in VCR-resistant RB cells. After treatment with orlistat or CQ, FA metabolism in VCR-resistant RB cells decreased, cell viability and autophagy were inhibited, EMT was inhibited, and the sensitivity of RB cells to VCR was increased. In conclusion, ACOT7 knockdown can mediate FA metabolism to inhibit autophagy and the migration of RB cells, thereby improving the sensitivity of RB cells to VCR.

Mitochondrial dysfunction route as a possible biomarker and therapy target for human cancer

Mitochondria are vital organelles found within living cells and have signalling, biosynthetic, and bioenergetic functions. Mitochondria play a crucial role in metabolic reprogramming, which is a characteristic of cancer cells and allows them to assure a steady supply of proteins, nucleotides, and lipids to enable rapid proliferation and development. Their dysregulated activities have been associated with the growth and metastasis of different kinds of human cancer, particularly ovarian carcinoma. In this review, we briefly demonstrated the modified mitochondrial function in cancer, including mutations in mtDNA, reactive oxygen species production, dynamics, apoptosis of cells, autophagy, and calcium excess to maintain cancer genesis, progression, and metastasis. Furthermore, the mitochondrial dysfunction pathway for some genomic, proteomic, and metabolomics modifications in ovarian cancer has been studied. Additionally, ovarian cancer has been linked to targeted therapies and biomarkers found through various alteration processes underlying mitochondrial dysfunction, notably targeting reactive oxygen species, metabolites, rewind metabolic pathways, and chemo-resistant ovarian carcinoma cells.

Tumor acidosis-induced DNA damage response and tetraploidy enhance sensitivity to ATM and ATR inhibitors

Tumor acidosis is associated with increased invasiveness and drug resistance. Here, we take an unbiased approach to identify vulnerabilities of acid-exposed cancer cells by combining pH-dependent flow cytometry cell sorting from 3D colorectal tumor spheroids and transcriptomic profiling. Besides metabolic rewiring, we identify an increase in tetraploid cell frequency and DNA damage response as consistent hallmarks of acid-exposed cancer cells, supported by the activation of ATM and ATR signaling pathways. We find that regardless of the cell replication error status, both ATM and ATR inhibitors exert preferential growth inhibitory effects on acid-exposed cancer cells. The efficacy of a combination of these drugs with 5-FU is further documented in 3D spheroids as well as in patient-derived colorectal tumor organoids. These data position tumor acidosis as a revelator of the therapeutic potential of DNA repair blockers and as an attractive clinical biomarker to predict the response to a combination with chemotherapy.

Metabolomic Profiling of Blood Plasma in Females with Hyperplasia and Endometrial Cancer

Uterine cancer is the most prevalent gynecologic malignancy in women worldwide. Endometrial cancer (EC) has an 81% five-year survival rate, depending on disease stage and time of diagnosis. While endometrial cancer is largely treatable when detected early, no established screening techniques are available in clinical practice. As a result, one of the most significant issues in the medical field is the development of novel ways for early cancer identification, which could boost treatment success rates. Liquid chromatography-high-resolution mass spectrometry (LC-HRMS)-based metabolomics was employed to explore the metabolomic markers and pathways unique to this cancer type and link them to the benign endometrial hyperplasia that may progress to cancer in 5% to 25% of patients. The study involved 59 postmenopausal participants, 20 with EC type 1, 20 with benign hyperplasia, and 19 healthy participants. Metabolite distribution changes were analyzed, and 338 of these features were dysregulated and significant. The first two main components, PC1 and PC2, were responsible for 11.5% and 12.2% of the total metabolites, respectively. Compared with the control group (CO), EC samples had 203 differentially expressed metabolites (180 upregulated and 23 downregulated); in hyperplasia (HP), 157 metabolites were dysregulated (127 upregulated and 30 downregulated) compared to the CO group while 21 metabolites exhibited differential regulation (16 upregulated and 5 downregulated) in EC plasma samples compared to the HP group. Hyperplasia samples exhibited similar metabolic changes to those reported in cancer, except for alterations in triglyceride levels, 7a,12 b-dihydroxy-5b-Cholan-24-oic acid, and Hept-2-enedioyl carnitine levels. The metabolites N-heptanoyl glycine and -(Methylthio)-2,3-isopentyl phosphate and formimino glutamic acid can be specific markers for hyperplasia conditions and dimethyl phosphatidyl ethanolamine and 8-isoprostaglandin E2 can be specific markers for EC conditions. Metabolic activities rely on mitochondrial oxidative phosphorylation for energy generation. The changes in metabolites identified in our study indicate that endometrial cancer cells adopt alternative strategies to increase energy production to meet the energy demand, thereby supporting proliferation.

The role of serum acylcarnitine profiling for the detection of multiple solid tumors in humans

Metabolic reprogramming is an essential hallmark of cancer. Several studies have reported the dysregulation of acylcarnitine (ACar) metabolism in tumor cells, suggesting that changes in the blood ACar may be related to tumor growth. Accordingly, this study aimed to understand the alteration of serum ACar profiles in various solid tumors and explore the potential of differential serum ACars as diagnostic biomarkers. A series of 69 relatively abundant ACars were identified via untargeted analysis. Then, targeted metabolomics was used to describe the metabolic alterations in ACars between normal controls and patients with six types of solid tumors. The results suggested that changes in ACars correlated with their carbon chain length and saturation. The six tumor types had highly similar ACar metabolic profiles, indicating similar fatty acid oxidation (FAO) metabolic pathways. Moreover, the receiver operating curve analysis of differential ACars showed that 16 ACars (C8-C14) had high diagnostic capability towards the studied solid tumors. Specifically, the area under the curve of ACar 10:2 isomer2 and ACar 12:2 isomer2 was greater than 0.95. In conclusion, the marked decrease in the levels of medium- and long-chain ACars (C8-C18) in the six solid tumors suggests that they may have similar FAO-based metabolic pathways, which could afford a common target for cancer therapy. Additionally, 16 ACars (C8-C14) were identified as potential biomarkers for diagnosing six types of solid tumors.

Role of bio-flavonols and their derivatives in improving mitochondrial dysfunctions associated with pancreatic tumorigenesis

Mitochondria, a cellular metabolic center, efficiently fulfill cellular energy needs and regulate crucial metabolic processes, including cellular proliferation, differentiation, apoptosis, and generation of reactive oxygen species. Alteration in the mitochondrial functions leads to metabolic imbalances and altered extracellular matrix dynamics in the host, utilized by solid tumors like pancreatic cancer (PC) to get energy benefits for fast-growing cancer cells. PC is highly heterogeneous and remains unidentified for a longer time because of its complex pathophysiology, retroperitoneal position, and lack of efficient diagnostic approaches, which is the foremost reason for accounting for the seventh leading cause of cancer-related deaths worldwide. PC cells often respond poorly to current therapeutics because of dense stromal barriers in the pancreatic tumor microenvironment, which limit the drug delivery and distribution of antitumor immune cell populations. As an alternative approach, various natural compounds like flavonoids are reported to possess potent antioxidant and anticancerous properties and are less toxic than current chemotherapeutic drugs. Therefore, we aim to summarize the current state of knowledge regarding the pharmacological properties of flavonols in PC in this review from the perspective of mitigating mitochondrial dysfunctions associated with cancer cells. Our literature survey indicates that flavonols efficiently regulate cellular metabolism by scavenging reactive oxygen species, mitigating inflammation, and arresting the cell cycle to promote apoptosis in tumor cells via intrinsic mitochondrial pathways. In particular, flavonols proficiently inhibit the cancer-associated proliferation and inflammatory pathways such as EGFR/MAPK, PI3K/Akt, and nuclear factor κB in PC. Overall, this review provides in-depth evidence about the therapeutic potential of flavonols for future anticancer strategies against PC; still, more multidisciplinary human interventional studies are required to dissect their pharmacological effect accurately.

Metabolic Adaptation and Cellular Stress Response As Targets for Cancer Therapy

Cancer cells, which divide indefinitely and without control, are frequently exposed to various stress factors but manage to adapt and survive. The mechanisms by which cancer cells maintain cellular homeostasis and exploit stress conditions are not yet clear. Here, we elucidate the roles of diverse cellular metabolism and its regulatory mechanisms, highlighting the essential role of metabolism in cellular composition and signal transduction. Cells respond to various stresses, including DNA damage, energy stress, and oxidative stress, thereby causing metabolic alteration. We provide profound insight into the adaptive mechanisms employed by cancer cells to ensure their survival among internal and external stressors through a comprehensive analysis of the correlation between metabolic alterations and cellular stress. Furthermore, this research establishes a robust framework for the development of innovative therapeutic strategies that specifically target the cellular adaptations of cancer cells.

PRRG4 regulates mitochondrial function and promotes migratory behaviors of breast cancer cells through the Src-STAT3-POLG axis

BACKGROUND

Breast cancer is the leading cause of cancer death for women worldwide. Most of the breast cancer death are due to disease recurrence and metastasis. Increasingly accumulating evidence indicates that mitochondria play key roles in cancer progression and metastasis. Our recent study revealed that transmembrane protein PRRG4 promotes the metastasis of breast cancer. However, it is not clear whether PRRG4 can affect the migration and invasion of breast cancer cells through regulating mitochondria function.

METHODS

RNA-seq analyses were performed on breast cancer cells expressing control and PRRG4 shRNAs. Quantitative PCR analysis and measurements of mitochondrial ATP content and oxygen consumption were carried out to explore the roles of PRRG4 in regulating mitochondrial function. Luciferase reporter plasmids containing different lengths of promoter fragments were constructed. Luciferase activities in breast cancer cells transiently transfected with these reporter plasmids were analyzed to examine the effects of PRRG4 overexpression on promoter activity. Transwell assays were performed to determine the effects of PRRG4-regulated pathway on migratory behaviors of breast cancer cells.

RESULTS

Analysis of the RNA-seq data revealed that PRRG4 knockdown decreased the transcript levels of all the mitochondrial protein-encoding genes. Subsequently, studies with PRRG4 knockdown and overexpression showed that PRRG4 expression increased mitochondrial DNA (mtDNA) content. Mechanistically, PRRG4 via Src activated STAT3 in breast cancer cells. Activated STAT3 in turn promoted the transcription of mtDNA polymerase POLG through a STAT3 DNA binding site present in the POLG promoter region, and increased mtDNA content as well as mitochondrial ATP production and oxygen consumption. In addition, PRRG4-mediated activation of STAT3 also enhanced filopodia formation, migration, and invasion of breast cancer cells. Moreover, PRRG4 elevated migratory behaviors and mitochondrial function of breast cancer cells through POLG.

CONCLUSION

Our results indicate that PRRG4 via the Src-STAT3-POLG axis enhances mitochondrial function and promotes migratory behaviors of breast cancer cells.

How protons pave the way to aggressive cancers

Cancers undergo sequential changes to proton (H+) concentration and sensing that are consequences of the disease and facilitate its further progression. The impact of protonation state on protein activity can arise from alterations to amino acids or their titration. Indeed, many cancer-initiating mutations influence pH balance, regulation or sensing in a manner that enables growth and invasion outside normal constraints as part of oncogenic transformation. These cancer-supporting effects become more prominent when tumours develop an acidic microenvironment owing to metabolic reprogramming and disordered perfusion. The ensuing intracellular and extracellular pH disturbances affect multiple aspects of tumour biology, ranging from proliferation to immune surveillance, and can even facilitate further mutagenesis. As a selection pressure, extracellular acidosis accelerates disease progression by favouring acid-resistant cancer cells, which are typically associated with aggressive phenotypes. Although acid-base disturbances in tumours often occur alongside hypoxia and lactate accumulation, there is now ample evidence for a distinct role of H+-operated responses in key events underpinning cancer. The breadth of these actions presents therapeutic opportunities to change the trajectory of disease.

Nebulized inhalation of LPAE-HDAC10 inhibits acetylation-mediated ROS/NF-κB pathway for silicosis treatment

Silicosis is a serious silica-induced respiratory disease for which there is currently no effective treatment. Irreversible pulmonary fibrosis caused by persistent inflammation is the main feature of silicosis. As an underlying mechanism, acetylation regulated by histone deacetylases (HDACs) are believed to be closely associated with persistent inflammation and pulmonary fibrosis. However, details of the mechanisms associated with the regulation of acetylated modification in silicosis have yet to be sufficiently established. Furthermore, studies on the efficient delivery of DNA to lung tissues by nebulized inhalation for the treatment of silicosis are limited. In this study, we established a mouse model of silicosis successfully. Differentially expressed genes (DEGs) between the lung tissues of silicosis and control mice were identified based on transcriptomic analysis, and HDAC10 was the only DEG among the HDACs. Acetylomic and combined acetylomic/proteomic analysis were performed and found that the differentially expressed acetylated proteins have diverse biological functions, among which 12 proteins were identified as the main targets of HDAC10. Subsequently, HDAC10 expression levels were confirmed to increase following nebulized inhalation of linear poly(β-amino ester) (LPAE)-HDAC10 nanocomplexes. The levels of oxidative stress, the phosphorylation of IKKβ, IκBα and p65, as well as inflammation were inhibited by HDAC10. Pulmonary fibrosis, and lung function in silicosis showed significant improvements in response to the upregulation of HDAC10. Similar results were obtained for the silica-treated macrophages in vitro. In conclusion, HDAC10 was identified as the main mediator of acetylation in silicosis. Nebulized inhalation of LPAE-HDAC10 nanocomplexes was confirmed to be a promising treatment option for silicosis. The ROS/NF-κB pathway was identified as an essential signaling pathway through which HDAC10 attenuates oxidative stress, inflammation, and pulmonary fibrosis in silicosis. This study provides a new theoretical basis for the treatment of silicosis.

HMGB1/SET/HAT1 complex-mediated SASH1 repression drives glycolysis and metastasis in lung adenocarcinoma

High-mobility group box 1 (HMGB1) can enhance the stability and accessibility of nucleus binding sites to nucleosomes and transcription factors. Recently, HMGB1 has been recognized as a positive regulator of tumor glutamine, and its overexpression has been correlated with tumorigenesis and cancer progression. However, functions and mechanisms of HMGB1 in regulation of glycolysis during cancer progression in lung adenocarcinoma (LUAD) is still unclear. Here, we found that intracellular HMGB1 was consistently upregulated in LUAD specimens, and positively relevant to tumor grade and poor survival. HMGB1 facilitated glycolysis and promoted metastasis through physical interaction with SET and HAT1, forming HMGB1/SET/HAT1 complex that inhibited H3K9 and H3K27 acetylation in LUAD. The functional proteins complex coordinated histone modification to suppress the expression of SASH1, thus further facilitating glycolysis and inducing the metastasis in vitro and in vivo. Consistent with this, the expression of SASH1 was negatively correlated with HMGB1, SET and GLUT1, and positively correlated with HAT1 in human LUAD specimens. Clinically, LUAD patients with high expression of HMGB1 and low expression of SASH1 exhibited the worst clinical outcomes. Overall, the findings of this study revealed the critical role of HMGB1 in glycolysis and metastasis by attenuating H3K9ace and H3K27ace through physical interacted with SET and HAT1, which may facilitate future targeted therapies.

The dual role of citrate in cancer

Citrate is a key metabolite of the Krebs cycle that can also be exported in the cytosol, where it performs several functions. In normal cells, citrate sustains protein acetylation, lipid synthesis, gluconeogenesis, insulin secretion, bone tissues formation, spermatozoid mobility, and immune response. Dysregulation of citrate metabolism is implicated in several pathologies, including cancer. Here we discuss how cancer cells use citrate to sustain their proliferation, survival, and metastatic progression. Also, we propose two paradoxically opposite strategies to reduce tumour growth by targeting citrate metabolism in preclinical models. In the first strategy, we propose to administer in the tumor microenvironment a high amount of citrate, which can then act as a glycolysis inhibitor and apoptosis inducer, whereas the other strategy targets citrate transporters to starve cancer cells from citrate. These strategies, effective in several preclinical in vitro and in vivo cancer models, could be exploited in clinics, particularly to increase sensibility to current anti-cancer agents.

pH sensing at the intersection of tissue homeostasis and inflammation

pH is tightly maintained at cellular, tissue, and systemic levels, and altered pH - particularly in the acidic range - is associated with infection, injury, solid tumors, and physiological and pathological inflammation. However, how pH is sensed and regulated and how it influences immune responses remain poorly understood at the tissue level. Applying conceptual frameworks of homeostatic and inflammatory circuitries, we categorize cellular and tissue components engaged in pH regulation, drawing parallels from established cases in physiology. By expressing various intracellular (pHi) and extracellular pH (pHe)-sensing receptors, the immune system may integrate information on tissue and cellular states into the regulation of homeostatic and inflammatory programs. We introduce the novel concept of resistance and adaptation responses to rationalize pH-dependent immunomodulation intertwined with homeostatic equilibrium and inflammatory control. We discuss emerging challenges and opportunities in understanding the immunological roles of pH sensing, which might reveal new strategies to combat inflammation and restore tissue homeostasis.

Lactate acidosis and simultaneous recruitment of TGF-β leads to alter plasticity of hypoxic cancer cells in tumor microenvironment

Lactate acidosis is often observed in the tumor microenvironment (TME) of solid tumors. This is because glucose breaks down quickly via glycolysis, causing lactate acidity. Lactate is harmful to healthy cells, but is a major oncometabolite for solid cancer cells that do not receive sufficient oxygen. As an oncometabolite, it helps tumor cells perform different functions, which helps solid hypoxic tumor cells spread to other parts of the body. Studies have shown that the acidic TME contains VEGF, Matrix metalloproteinases (MMPs), cathepsins, and transforming growth factor-β (TGF-β), all of which help spread in direct and indirect ways. Although each cytokine is important in its own manner in the TME, TGF-β has received much attention for its role in metastatic transformation. Several studies have shown that lactate acidosis can cause TGF-β expression in solid hypoxic cancers. TGF-β has also been reported to increase the production of fatty acids, making cells more resistant to treatment. TGF-β has also been shown to control the expression of VEGF and MMPs, which helps solid hypoxic tumors become more aggressive by helping them spread and create new blood vessels through an unknown process. The role of TGF-β under physiological conditions has been described previously. In this study, we examined the role of TGF-β, which is induced by lactate acidosis, in the spread of solid hypoxic cancer cells. We also found that TGF-β and lactate work together to boost fatty acid production, which helps angiogenesis and invasiveness.

CPT2-mediated fatty acid oxidation inhibits tumorigenesis and enhances sorafenib sensitivity via the ROS/PPARγ/NF-κB pathway in clear cell renal cell carcinoma

Kidney cancer is a common kind of tumor with approximately 400,000 new diagnoses each year. Clear cell renal cell carcinoma (ccRCC) accounts for 70-80% of all renal cell carcinomas. Lipid metabolism disorder is a hallmark of ccRCC. With a better knowledge of the importance of fatty acid oxidation (FAO) in cancer, carnitine palmitoyltransferase 2 (CPT2) has gained prominence as a major mediator in the cancer metabolic pathway. However, the biological functions and mechanism of CPT2 in the progression of ccRCC are still unclear. Herein, we performed assays in vitro and in vivo to explore CPT2 functions in ccRCC. Moreover, we discovered that CPT2 induced FAO, which inhibited the generation of reactive oxygen species (ROS) by increasing nicotinamide adenine dinucleotide phosphate (NADPH) production. Additionally, we demonstrated that CPT2 suppresses tumor proliferation, invasion, and migration by inhibiting the ROS/ PPARγ /NF-κB pathway. Gene set enrichment analysis (GSEA) and drug sensitivity analysis showed that high expression of CPT2 in ccRCC was associated with higher sorafenib sensitivity, which was also validated in vitro and in vivo. In summary, our results suggest that CPT2 acts as a tumor suppressor in the development of ccRCC through the ROS/PPARγ/NF-κB pathway. Moreover, CPT2 is a potential therapeutic target for increasing sorafenib sensitivity in ccRCC.

Enhancing prognostic accuracy in head and neck squamous cell carcinoma chemotherapy via a lipid metabolism-related clustered polygenic model

OBJECTIVE

Systemic chemotherapy is the first-line therapeutic option for head and neck squamous cell carcinoma (HNSCC), but it often fails. This study aimed to develop an effective prognostic model for evaluating the therapeutic effects of systemic chemotherapy.

METHODS

This study utilized CRISPR/cas9 whole gene loss-of-function library screening and data from The Cancer Genome Atlas (TCGA) HNSCC patients who have undergone systemic therapy to examine differentially expressed genes (DEGs). A lipid metabolism-related clustered polygenic model called the lipid metabolism related score (LMRS) model was established based on the identified functionally enriched DEGs. The prediction efficiency of the model for survival outcome, chemotherapy, and immunotherapy response was evaluated using HNSCC datasets, the GEO database and clinical samples.

RESULTS

Screening results from the study demonstrated that genes those were differentially expressed were highly associated with lipid metabolism-related pathways, and patients receiving systemic therapy had significantly different prognoses based on lipid metabolism gene characteristics. The LMRS model, consisting of eight lipid metabolism-related genes, outperformed each lipid metabolism gene-based model in predicting outcome and drug response. Further validation of the LMRS model in HNSCCs confirmed its prognostic value.

CONCLUSION

In conclusion, the LMRS polygenic prognostic model is helpful to assess outcome and drug response for HNSCCs and could assist in the timely selection of the appropriate treatment for HNSCC patients. This study provides important insights for improving systemic chemotherapy and enhancing patient outcomes.

Metabolic Alteration of MCF-7 Cells upon Indirect Exposure to E. coli Secretome: A Model of Studying the Microbiota Effect on Human Breast Tissue

According to studies, the microbiome may contribute to the emergence and spread of breast cancer. E. coli is one of the Enterobacteriaceae family recently found to be present as part of the breast tissue microbiota. In this study, we focused on the effect of E. coli secretome free of cells on MCF-7 metabolism. Liquid chromatography-mass spectrometry (LC-MS) metabolomics was used to study the E. coli secretome and its role in MCF-7 intra- and extracellular metabolites. A comparison was made between secretome-exposed cells and unexposed controls. Our analysis revealed significant alterations in 31 intracellular and 55 extracellular metabolites following secretome exposure. Several metabolic pathways, including lactate, aminoacyl-tRNA biosynthesis, purine metabolism, and energy metabolism, were found to be dysregulated upon E. coli secretome exposure. E. coli can alter the breast cancer cells' metabolism through its secretome which disrupts key metabolic pathways of MCF-7 cells. These microbial metabolites from the secretome hold promise as biomarkers of drug resistance or innovative approaches for cancer treatment, either as standalone therapies or in combination with other medicines.

Breast cancers as ecosystems: a metabolic perspective

Breast cancer (BC) is the most frequently diagnosed cancer and one of the major causes of cancer death. Despite enormous progress in its management, both from the therapeutic and early diagnosis viewpoints, still around 700,000 patients succumb to the disease each year, worldwide. Late recurrency is the major problem in BC, with many patients developing distant metastases several years after the successful eradication of the primary tumor. This is linked to the phenomenon of metastatic dormancy, a still mysterious trait of the natural history of BC, and of several other types of cancer, by which metastatic cells remain dormant for long periods of time before becoming reactivated to initiate the clinical metastatic disease. In recent years, it has become clear that cancers are best understood if studied as ecosystems in which the impact of non-cancer-cell-autonomous events-dependent on complex interaction between the cancer and its environment, both local and systemic-plays a paramount role, probably as significant as the cell-autonomous alterations occurring in the cancer cell. In adopting this perspective, a metabolic vision of the cancer ecosystem is bound to improve our understanding of the natural history of cancer, across space and time. In BC, many metabolic pathways are coopted into the cancer ecosystem, to serve the anabolic and energy demands of the cancer. Their study is shedding new light on the most critical aspect of BC management, of metastatic dissemination, and that of the related phenomenon of dormancy and fostering the application of the knowledge to the development of metabolic therapies.

VNN1 as a potential biomarker for sepsis diagnosis and its implications in immune infiltration and tumor prognosis

Background

This study explored novel biomarkers for diagnosing sepsis, a severe disease prevalent in clinical settings, particularly threatening to elderly patients.

Methods

Using microarray gene expression datasets and fatty acid metabolism signatures, we identified differentially expressed genes between sepsis and healthy control groups. Correlations between candidate genes, immune cells, and immune function were assessed. Logistic regression analysis and single-gene GSEA analysis were performed to identify potential biomarkers. The biomarkers' association with different types of tumors was investigated.

Results

Twelve genes related to fatty acid metabolism were excluded. CA4, OLAN, and VNN1 were found relevant to immune cells and function. Among these, only VNN1 showed statistical significance (p < 0.05), with a strong area under the ROC curve (0.995). High VNN1 expression indicated activation of certain metabolic pathways, while low expression suggested potential autoimmune responses. VNN1 was up-regulated in eight tumors and down-regulated in eight others. High VNN1 expression was linked to poor prognosis in six types of tumors, and low expression was linked to poor prognosis in four types of tumors. VNN1 expression showed correlations with stromal scores, immune scores, and cancer purity in different types of tumors.

Conclusion

VNN1 holds promise as a potential biomarker for sepsis diagnosis and is significant in identifying immune infiltration in tumor tissue and predicting tumor prognosis.

Obesity-induced changes in cancer cells and their microenvironment: Mechanisms and therapeutic perspectives to manage dysregulated lipid metabolism

Obesity has been closely related to cancer progression, recurrence, metastasis, and treatment resistance. We aim to review recent progress in the knowledge on the obese macroenvironment and the generated adipose tumor microenvironment (TME) inducing lipid metabolic dysregulation and their influence on carcinogenic processes. Visceral white adipose tissue expansion during obesity exerts systemic or macroenvironmental effects on tumor initiation, growth, and invasion by promoting inflammation, hyperinsulinemia, growth-factor release, and dyslipidemia. The dynamic relationship between cancer and stromal cells of the obese adipose TME is critical for cancer cell survival and proliferation as well. Experimental evidence shows that secreted paracrine signals from cancer cells can induce lipolysis in cancer-associated adipocytes, causing them to release free fatty acids and acquire a fibroblast-like phenotype. Such adipocyte delipidation and phenotypic change is accompanied by an increased secretion of cytokines by cancer-associated adipocytes and tumor-associated macrophages in the TME. Mechanistically, the availability of adipose TME free fatty acids and tumorigenic cytokines concomitant with the activation of angiogenic processes creates an environment that favors a shift in the cancer cells toward an aggressive phenotype associated with increased invasiveness. We conclude that restoring the aberrant metabolic alterations in the host macroenvironment and in adipose TME of obese subjects would be a therapeutic option to prevent cancer development. Several dietary, lipid-based, and oral antidiabetic pharmacological therapies could potentially prevent tumorigenic processes associated with the dysregulated lipid metabolism closely linked to obesity.

An immune-related gene prognostic index for predicting prognosis in patients with colorectal cancer

Background

Colorectal cancer (CRC) is one of the most common solid malignant burdens worldwide. Cancer immunology and immunotherapy have become fundamental areas in CRC research and treatment. Currently, the method of generating Immune-Related Gene Prognostic Indices (IRGPIs) has been found to predict patient prognosis as an immune-related prognostic biomarker in a variety of tumors. However, their role in patients with CRC remains mostly unknown. Therefore, we aimed to establish an IRGPI for prognosis evaluation in CRC.

Methods

RNA-sequencing data and clinical information of CRC patients were retrieved from The Cancer Genome Atlas (TCGA) and The Gene Expression Omnibus (GEO) databases as training and validation sets, respectively. Immune-related gene data was obtained from the ImmPort and InnateDB databases. The weighted gene co-expression network analysis (WGCNA) was used to identify hub immune-related genes. An IRGPI was then constructed using Cox regression methods. Based on the median risk score of IRGPI, patients could be divided into high-risk and low-risk groups. To further investigate the immunologic differences, Gene set variation analysis (GSVA) studies were conducted. In addition, immune cell infiltration and related functional analysis were used to identify the differential immune cell subsets and related functional pathways.

Results

We identified 49 immune-related genes associated with the prognosis of CRC, 17 of which were selected for an IRGPI. The IRGPI model significantly differentiates the survival rates of CRC patients in the different groups. The IRGPI as an independent prognostic factor significantly correlates with clinico-pathological factors such as age and tumor stage. Furthermore, we developed a nomogram to improve the clinical utility of the IRGPI score. Immuno-correlation analysis in different IRGPI groups revealed distinct immune cell infiltration (CD4⁺ T cells resting memory) and associated pathways (macrophages, Type I IFNs responses, iDCs.), providing new insights into the tumor microenvironment. At last, drug sensitivity analysis revealed that the high-risk IRGPI group was sensitive to 11 and resistant to 15 drugs.

Conclusion

Our study established a promising immune-related risk model for predicting survival in CRC patients. This could help to better understand the correlation between immunity and the prognosis of CRC providing a new perspective for personalized treatment of CRC.

Mitochondria Deregulations in Cancer Offer Several Potential Targets of Therapeutic Interventions

Mitochondria play a key role in cancer and their involvement is not limited to the production of ATP only. Mitochondria also produce reactive oxygen species and building blocks to sustain rapid cell proliferation; thus, the deregulation of mitochondrial function is associated with cancer disease development and progression. In cancer cells, a metabolic reprogramming takes place through a different modulation of the mitochondrial metabolic pathways, including oxidative phosphorylation, fatty acid oxidation, the Krebs cycle, glutamine and heme metabolism. Alterations of mitochondrial homeostasis, in particular, of mitochondrial biogenesis, mitophagy, dynamics, redox balance, and protein homeostasis, were also observed in cancer cells. The use of drugs acting on mitochondrial destabilization may represent a promising therapeutic approach in tumors in which mitochondrial respiration is the predominant energy source. In this review, we summarize the main mitochondrial features and metabolic pathways altered in cancer cells, moreover, we present the best known drugs that, by acting on mitochondrial homeostasis and metabolic pathways, may induce mitochondrial alterations and cancer cell death. In addition, new strategies that induce mitochondrial damage, such as photodynamic, photothermal and chemodynamic therapies, and the development of nanoformulations that specifically target drugs in mitochondria are also described. Thus, mitochondria-targeted drugs may open new frontiers to a tailored and personalized cancer therapy.

The Role of CD36 in Cancer Progression and Its Value as a Therapeutic Target

Cluster of differentiation 36 (CD36) is a cell surface scavenger receptor that plays critical roles in many different types of cancer, notably breast, brain, and ovarian cancers. While it is arguably most well-known for its fatty acid uptake functions, it is also involved in regulating cellular adhesion, immune response, and apoptosis depending on the cellular and environmental contexts. Here, we discuss the multifaceted role of CD36 in cancer biology, such as its role in mediating metastasis, drug resistance, and immune evasion to showcase its potential as a therapeutic target. We will also review existing approaches to targeting CD36 in pre-clinical studies, as well as discuss the only CD36-targeting drug to advance to late-stage clinical trials, VT1021. Given the roles of CD36 in the etiology of metabolic disorders, such as atherosclerosis, diabetes, and non-alcoholic fatty liver disease, the clinical implications of CD36-targeted therapy are wide-reaching, even beyond cancer.

Intermittent Fasting Sustainably Improves Glucose Tolerance in Normal Weight Male Mice Through Histone Hyperacetylation

To explore the mechanism by which intermittent fasting (IF) exerts prolonged effects after discontinuation, we examined mice that had been subjected to 4 cycles of fasting for 72 hours and ad libitum feeding for 96 hours per week (72hIF), followed by 4 weeks of ad libitum feeding, focusing on expression of genes for lipid metabolism in the skeletal muscle and histone acetylation in the promoter region. The 72hIF regimen resulted in metabolic remodeling, characterized by enhanced lipid utilization and mitochondrial activation in the muscle. This long-term IF (72hIF) caused stronger metabolic effects than alternate day fasting (24hIF) wherein fasting and refeeding are repeated every 24 hours. Upregulation of lipid oxidation genes and an increase in oxygen utilization were sustained even at 4 weeks after discontinuation of 72hIF, associated with histone hyperacetylation of the promoter region of uncoupling protein 3 (Ucp3) and carnitine palmitoyl transferase 1b (Cpt1b) genes. An increase in leucine owing to fasting-induced muscle degradation was suggested to lead to the histone acetylation. These findings support the previously unappreciated notion that sustainable promotion of histone acetylation in lipid oxidation genes of the muscle and adipose tissues during and after IF may contribute to sustained metabolic effects of IF.

Impact of context-dependent autophagy states on tumor progression

Macroautophagy is a cellular quality-control process that degrades proteins, protein aggregates and damaged organelles. Autophagy plays a fundamental role in cancer where, in the presence of stressors (for example, nutrient starvation, hypoxia, mechanical pressure), tumor cells activate it to degrade intracellular substrates and provide energy. Cell-autonomous autophagy in tumor cells and cell-nonautonomous autophagy in the tumor microenvironment and in the host converge on mechanisms that modulate metabolic fitness, DNA integrity and immune escape and, consequently, support tumor growth. In this Review, we will discuss insights into the tumor-modulating roles of autophagy in different contexts and reflect on how future studies using physiological culture systems may help to understand the complexity and open new therapeutic avenues.

Targeting monocarboxylate transporters (MCTs) in cancer: How close are we to the clinics?

As a result of metabolic reprogramming, cancer cells display high rates of glycolysis, causing an excess production of lactate along with an increase in extracellular acidity. Proton-linked monocarboxylate transporters (MCTs) are crucial in the maintenance of this metabolic phenotype, by mediating the proton-coupled lactate flux across cell membranes, also contributing to cancer cell pH regulation. Among the proteins codified by the SLC16 gene family, MCT1 and MCT4 isoforms are the most explored in cancers, being overexpressed in many cancer types, from solid tumours to haematological malignancies. Similarly to what occurs in particular physiological settings, MCT1 and MCT4 are able to mediate lactate shuttles among cancer cells, and also between cancer and stromal cells in the tumour microenvironment. This form of metabolic cooperation is responsible for important cancer aggressiveness features, such as cell proliferation, survival, angiogenesis, migration, invasion, metastasis, immune tolerance and therapy resistance. The growing understanding of MCT functions and regulation is offering a new path to the design of novel inhibitors that can be foreseen in clinical practices. This review provides an overview of the role of MCT isoforms in cancer and summarizes the recent advances in their pharmacological targeting, highlighting the potential of new potent and selective MCT1 and/or MCT4 inhibitors in cancer therapeutics, and anticipating its inclusion in clinical practice.

CPT1C-mediated fatty acid oxidation facilitates colorectal cancer cell proliferation and metastasis

Fatty acid oxidation (FAO) has been proven to be an accomplice in tumor progression. Carnitine palmitoyltransferase 1C (CPT1C), a rate-limiting enzyme in FAO, mainly functions to catalyze fatty acid carnitinylation and guarantee subsequent entry into the mitochondria for FAO in colorectal cancer (CRC). Gene expression data and clinical information extracted from The Cancer Genome Atlas (TCGA) database show significantly higher expression of CPT1C in patients with metastatic CRC ( P=0.005). Moreover, overexpression of CPT1C is correlated with worse relapse-free survival in CRC (HR 2.1, P=0.0006), while no statistical significance is indicated for CPT1A and CPT1B. Further experiments demonstrate that downregulation of CPT1C expression leads to a decrease in the FAO rate, suppression of cell proliferation, cell cycle arrest and repression of cell migration in CRC, whereas opposite results are obtained when CPT1C is overexpressed. Furthermore, an FAO inhibitor almost completely reverses the enhanced cell proliferation and migration induced by CPT1C overexpression. In addition, analysis of TCGA data illustrates a positive association between CPT1C expression and HIF1α level, suggesting that CPT1C is a transcriptional target of HIF1α. In conclusion, CPT1C overexpression indicates poor relapse-free survival of patients with CRC, and CPT1C is transcriptionally activated by HIF1α, thereby promoting the proliferation and migration of CRC cells.

The role of HDAC3 and its inhibitors in regulation of oxidative stress and chronic diseases

HDAC3 is a specific and crucial member of the HDAC family. It is required for embryonic growth, development, and physiological function. The regulation of oxidative stress is an important factor in intracellular homeostasis and signal transduction. Currently, HDAC3 has been found to regulate several oxidative stress-related processes and molecules dependent on its deacetylase and non-enzymatic activities. In this review, we comprehensively summarize the knowledge of the relationship of HDAC3 with mitochondria function and metabolism, ROS-produced enzymes, antioxidant enzymes, and oxidative stress-associated transcription factors. We also discuss the role of HDAC3 and its inhibitors in some chronic cardiovascular, kidney, and neurodegenerative diseases. Due to the simultaneous existence of enzyme activity and non-enzyme activity, HDAC3 and the development of its selective inhibitors still need further exploration in the future.