Evidence for an alternative fatty acid desaturation pathway increasing cancer plasticity

Targeting lipid metabolism is an emerging strategy to enhance the efficacy of anti-HER2 therapies in HER2-positive breast cancer

De novo or acquired resistance of cancer cells to currently available Human Epidermal Growth Factor Receptor 2 (HER2) inhibitors represents a clinical challenge. Several resistance mechanisms have been identified in recent years, with lipid metabolism reprogramming, a well-established hallmark of cancer, representing the last frontier of preclinical and clinical research in this field. Fatty Acid Synthase (FASN), the key enzyme required for fatty acids (FAs) biosynthesis, is frequently overexpressed/activated in HER2-positive (HER2+) breast cancer (BC), and it crucially sustains HER2+ BC cell growth, proliferation and survival. After the synthesis of new, selective and well tolerated FASN inhibitors, clinical trials have been initiated to test if these compounds are able to re-sensitize cancer cells with acquired resistance to HER2 inhibition. More recently, the upregulation of FA uptake by cancer cells has emerged as a potentially new and targetable mechanism of resistance to anti-HER2 therapies in HER2+ BC, thus opening a new era in the field of targeting metabolic reprogramming in clinical setting. Here, we review the available preclinical and clinical evidence supporting the inhibition of FA biosynthesis and uptake in combination with anti-HER2 therapies in patients with HER2+ BC, and we discuss ongoing clinical trials that are investigating these combination approaches.

Lipid metabolism in cancer: New perspectives and emerging mechanisms

Tumors undergo metabolic transformations to sustain uncontrolled proliferation, avoid cell death, and seed in secondary organs. An increased focus on cancer lipid metabolism has unveiled a number of mechanisms that promote tumor growth and survival, many of which are independent of classical cellular bioenergetics. These mechanisms include modulation of ferroptotic-mediated cell death, support during tumor metastasis, and interactions with the cells of the tumor microenvironment. As such, targeting lipid metabolism for anti-cancer therapies is attractive, with recent work on small-molecule inhibitors identifying compounds to target lipid metabolism. Here, we discuss these topics and identify open questions.

Paradigm shift: the primary function of the "Adiponectin Receptors" is to regulate cell membrane composition

The ADIPOR1 and ADIPOR2 proteins (ADIPORs) are generally considered as adiponectin receptors with anti-diabetic properties. However, studies on the yeast and C. elegans homologs of the mammalian ADIPORs, and of the ADIPORs themselves in various mammalian cell models, support an updated/different view. Based on findings in these experimental models, the ADIPORs are now emerging as evolutionarily conserved regulators of membrane homeostasis that do not require adiponectin to act as membrane fluidity sensors and regulate phospholipid composition. More specifically, membrane rigidification activates ADIPOR signaling to promote fatty acid desaturation and incorporation of polyunsaturated fatty acids into membrane phospholipids until fluidity is restored. The present review summarizes the evidence supporting this new view of the ADIPORs, and briefly examines physiological consequences.

The ZMYND8-regulated mevalonate pathway endows YAP-high intestinal cancer with metabolic vulnerability

Cholesterol metabolism is tightly associated with colorectal cancer (CRC). Nevertheless, the clinical benefit of statins, the inhibitor of cholesterol biogenesis mevalonate (MVA) pathway, is inconclusive, possibly because of a lack of patient stratification criteria. Here, we describe that YAP-mediated zinc finger MYND-type containing 8 (ZMYND8) expression sensitizes intestinal tumors to the inhibition of the MVA pathway. We show that the oncogenic activity of YAP relies largely on ZMYND8 to enhance intracellular de novo cholesterol biogenesis. Disruption of the ZMYND8-dependent MVA pathway greatly restricts the self-renewal capacity of Lgr5⁺ intestinal stem cells (ISCs) and intestinal tumorigenesis. Mechanistically, ZMYND8 and SREBP2 drive the enhancer-promoter interaction to facilitate the recruitment of Mediator complex, thus upregulating MVA pathway genes. Together, our results establish that the epigenetic reader ZMYND8 endows YAP-high intestinal cancer with metabolic vulnerability.

The metabolic adaptation mechanism of metastatic organotropism

Metastasis is a complex multistep cascade of cancer cell extravasation and invasion, in which metabolism plays an important role. Recently, a metabolic adaptation mechanism of cancer metastasis has been proposed as an emerging model of the interaction between cancer cells and the host microenvironment, revealing a deep and extensive relationship between cancer metabolism and cancer metastasis. However, research on how the host microenvironment affects cancer metabolism is mostly limited to the impact of the local tumour microenvironment at the primary site. There are few studies on how differences between the primary and secondary microenvironments promote metabolic changes during cancer progression or how secondary microenvironments affect cancer cell metastasis preference. Hence, we discuss how cancer cells adapt to and colonize in the metabolic microenvironments of different metastatic sites to establish a metastatic organotropism phenotype. The mechanism is expected to accelerate the research of cancer metabolism in the secondary microenvironment, and provides theoretical support for the generation of innovative therapeutic targets for clinical metastatic diseases.

mTOR Signaling and SREBP Activity Increase FADS2 Expression and Can Activate Sapienate Biosynthesis

Cancer cells display an increased plasticity in their lipid metabolism, which includes the conversion of palmitate to sapienate via the enzyme fatty acid desaturase 2 (FADS2). We find that FADS2 expression correlates with mammalian target of rapamycin (mTOR) signaling and sterol regulatory element-binding protein 1 (SREBP-1) activity across multiple cancer types and is prognostic in some cancer types. Accordingly, activating mTOR signaling by deleting tuberous sclerosis complex 2 (Tsc2) or overexpression of SREBP-1/2 is sufficient to increase FADS2 mRNA expression and sapienate metabolism in mouse embryonic fibroblasts (MEFs) and U87 glioblastoma cells, respectively. Conversely, inhibiting mTOR signaling decreases FADS2 expression and sapienate biosynthesis in MEFs with Tsc2 deletion, HUH7 hepatocellular carcinoma cells, and orthotopic HUH7 liver xenografts. In conclusion, we show that mTOR signaling and SREBP activity are sufficient to activate sapienate metabolism by increasing FADS2 expression. Consequently, targeting mTOR signaling can reduce sapienate metabolism in vivo.

Fatty acid desaturase activity in mature red blood cells and implications for blood storage quality

BACKGROUND

Increases in the red blood cell (RBC) degree of fatty acid desaturation are reported in response to exercise, aging, or diseases associated with systemic oxidant stress. However, no studies have focused on the presence and activity of fatty acid desaturases (FADS) in the mature RBC.

STUDY DESIGN AND METHODS

Steady state metabolomics and isotope-labeled tracing experiments, immunofluorescence approaches, and pharmacological interventions were used to determine the degree of fatty acid unsaturation, FADS activity as a function of storage, oxidant stress, and G6PD deficiency in human and mouse RBCs.

RESULTS

In 250 blood units from the REDS III RBC Omics recalled donor population, we report a storage-dependent accumulation of free mono-, poly-(PUFAs), and highly unsaturated fatty acids (HUFAs), which occur at a faster rate than saturated fatty acid accumulation. Through a combination of immunofluorescence, pharmacological inhibition, tracing experiments with stable isotope-labeled fatty acids, and oxidant challenge with hydrogen peroxide, we demonstrate the presence and redox-sensitive activity of FADS2, FADS1, and FADS5 in the mature RBC. Increases in PUFAs and HUFAs in human and mouse RBCs correlate negatively with storage hemolysis and positively with posttransfusion recovery. Inhibition of these enzymes decreases accumulation of free PUFAs and HUFAs in stored RBCs, concomitant to increases in pyruvate/lactate ratios. Alterations of this ratio in G6PD deficient patients or units supplemented with pyruvate-rich rejuvenation solutions corresponded to decreased PUFA and HUFA accumulation.

CONCLUSION

Fatty acid desaturases are present and active in mature RBCs. Their activity is sensitive to oxidant stress, storage duration, and alterations of the pyruvate/lactate ratio.

Monomethyl Auristatin E Grafted-Liposomes to Target Prostate Tumor Cell Lines

Novel nanomedicines have been engineered to deliver molecules with therapeutic potentials, overcoming drawbacks such as poor solubility, toxicity or short half-life. Lipid-based carriers such as liposomes represent one of the most advanced classes of drug delivery systems. A Monomethyl Auristatin E (MMAE) warhead was grafted on a lipid derivative and integrated in fusogenic liposomes, following the model of antibody drug conjugates. By modulating the liposome composition, we designed a set of particles characterized by different membrane fluidities as a key parameter to obtain selective uptake from fibroblast or prostate tumor cells. Only the fluid liposomes made of palmitoyl-oleoyl-phosphatidylcholine and dioleoyl-phosphatidylethanolamine, integrating the MMAE-lipid derivative, showed an effect on prostate tumor PC-3 and LNCaP cell viability. On the other hand, they exhibited negligible effects on the fibroblast NIH-3T3 cells, which only interacted with rigid liposomes. Therefore, fluid liposomes grafted with MMAE represent an interesting example of drug carriers, as they can be easily engineered to promote liposome fusion with the target membrane and ensure drug selectivity.

Extinguishing the Embers: Targeting AML Metabolism

Acute myeloid leukemia (AML) is a cancer derived from the myeloid lineage of blood cells, characterized by overproduction of leukemic blasts. Although therapeutic improvements have made a significant impact on the outcomes of patients with AML, survival rates remain low due to a high incidence of relapse. Similar to how wildfires can reignite from hidden embers not extinguished from an initial round of firefighting, leukemic stem cells (LSCs) are the embers remaining after completion of traditional chemotherapeutic treatments. LSCs exhibit a unique metabolic profile and contain metabolically distinct subpopulations. In this review, we detail the metabolic features of LSCs and how thetse characteristics promote resistance to traditional chemotherapy. We also discuss new therapeutic approaches that target metabolic vulnerabilities of LSC to selectively eradicate them.

Role of Aberrant Lipid Metabolism of Cancer Stem Cells in Cancer Progression

Cancer stem cells (CSCs) represent a small population of cancer cells that are able to self-renew and initiate tumors, which undergo epigenetic, epithelial-mesenchymal, immunological, and metabolic reprogramming to adapt to the tumor microenvironment as well as survive host defense or therapeutic insults. The metabolic reprogramming that accompanies cancer onset is known to be critical for the disease pathogenesis. A coordinated dysregulation of lipid metabolism is observed in nearly all cancer types. In addition to fulfilling basic requirements of structural lipids for membrane synthesis, lipids function importantly as signaling molecules and contribute to energy homeostasis. In this review, we summarize the current progress in the attractive research field of aberrant lipid metabolism regarding CSCs in cancer progression, which provides insights into therapeutic agents targeting CSCs based upon their modulation of lipid metabolism.

Lipid Metabolism and Ferroptosis

Simple Summary

Ferroptosis is a type of cell death, which is morphologically and mechanistically distinct from other type of cell death pathways such as apoptosis and necroptosis. Lipid peroxidation is a hallmark of ferroptosis and directly destroys cellular membranes, thereby causing ferroptosis. Since lipid peroxidation, which induces ferroptosis, occurs in polyunsaturated fatty acid on specific phospholipids, various lipid metabolic pathways are involved in lipid peroxidation and ferroptosis. Besides, various metabolic and signaling pathways directly and indirectly regulate lipid peroxidation and ferroptosis. Since ferroptosis is associated with a variety of human diseases such as cancer, myocardial infarction, atherosclerosis, kidney diseases, liver diseases, and neuronal diseases, a better understanding of the regulatory mechanisms of ferroptosis can provide insights and treatment strategies for related diseases.

Abstract

Ferroptosis is a type of iron-dependent regulated necrosis induced by lipid peroxidation that occurs in cellular membranes. Among the various lipids, polyunsaturated fatty acids (PUFAs) associated with several phospholipids, such as phosphatidylethanolamine (PE) and phosphatidylcholine (PC), are responsible for ferroptosis-inducing lipid peroxidation. Since the de novo synthesis of PUFAs is strongly restricted in mammals, cells take up essential fatty acids from the blood and lymph to produce a variety of PUFAs via PUFA biosynthesis pathways. Free PUFAs can be incorporated into the cellular membrane by several enzymes, such as ACLS4 and LPCAT3, and undergo lipid peroxidation through enzymatic and non-enzymatic mechanisms. These pathways are tightly regulated by various metabolic and signaling pathways. In this review, we summarize our current knowledge of how various lipid metabolic pathways are associated with lipid peroxidation and ferroptosis. Our review will provide insight into treatment strategies for ferroptosis-related diseases.

The metabolism of cancer cells during metastasis

Metastasis formation is the major cause of death in most patients with cancer. Despite extensive research, targeting metastatic seeding and colonization is still an unresolved challenge. Only recently, attention has been drawn to the fact that metastasizing cancer cells selectively and dynamically adapt their metabolism at every step during the metastatic cascade. Moreover, many metastases display different metabolic traits compared with the tumours from which they originate, enabling survival and growth in the new environment. Consequently, the stage-dependent metabolic traits may provide therapeutic windows for preventing or reducing metastasis, and targeting the new metabolic traits arising in established metastases may allow their eradication.

Comparison of the Fatty Acid Metabolism Pathway in Pan-Renal Cell Carcinoma: Evidence from Bioinformatics

This study analyzed and compared the potential role of fatty acid metabolism pathways in three subtypes of renal cell carcinoma. Biological pathways that were abnormally up- and downregulated were identified through gene set variation analysis in the subtypes. Abnormal downregulation of the fatty acid metabolism pathway occurred in all three renal cell carcinoma subtypes. Alteration of the fatty acid metabolism pathway was vital in the development of pan-renal cell carcinoma. Bioinformatics methods were used to obtain a panoramic view of copy number variation, single-nucleotide variation, mRNA expression, and the survival landscape of fatty acid metabolism pathway-related genes in pan-renal cell carcinoma. Most importantly, we used genes related to the fatty acid metabolism pathway to establish a prognostic-related risk model in the three subtypes of renal cell carcinoma. The data will be valuable for future clinical treatment and scientific research.

Dual derivatization strategy for the comprehensive quantification and double bond location characterization of fatty acids by ultra-high performance liquid chromatography-tandem mass spectrometry

Comprehensive analysis of fatty acids (FAs) has long been challenging due to their poor ionization efficiency, lack of characteristic fragment ions and difficulty of identifying C=C bond locations. In this study, a high coverage ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was established for the quantification and C=C bond location characterization of FAs using two structural analogues, 2-hydrazinyl-4,6-dimethylpyrimidine (DMP) and 2-hydrazinylpyrimidine (DP), as dual derivatization reagents. DP-labeled FA standards were used as internal standards to reduced matrix effects, which guaranteed the accurate quantification of FAs. The derivatization yields of FAs were larger than 99% and the sensitivities were increased by 400-fold compared with non-derivatized FAs. Pretreatment and instrumental analysis of FAs can be completed in 20 minutes. Only 5 μL rat plasma can satisfy the quantification of 36 FAs with good linearity (r>0.99). Both intra-day and inter-day accuracies were in the range of 85-105%, and the precisions were less than 15%. The extraction recoveries were investigated to be in the range of 88-112%. No obvious matrix effects were observed for the derivatized FAs. In addition, the locations of C=C bonds in DMP-derivatized FAs could be identified by diagnostic fragment ions generated from 1,4-hydrogen elimination and allylic cleavage under low energy collision induced dissociation (CID). The new method was finally employed for FA profiling in plasma from rats with moxifloxacin-induced liver injury. Significant downregulation of butyric acid was observed in moxifloxacin treated model rats, which was believed to be related to the liver injury.

Cancer metabolism and intervention therapy

Metabolic reprogramming with heterogeneity is a hallmark of cancer and is at the basis of malignant behaviors. It supports the proliferation and metastasis of tumor cells according to the low nutrition and hypoxic microenvironment. Tumor cells frantically grab energy sources (such as glucose, fatty acids, and glutamine) from different pathways to produce a variety of biomass to meet their material needs via enhanced synthetic pathways, including aerobic glycolysis, glutaminolysis, fatty acid synthesis (FAS), and pentose phosphate pathway (PPP). To survive from stress conditions (e.g., metastasis, irradiation, or chemotherapy), tumor cells have to reprogram their metabolism from biomass production towards the generation of abundant adenosine triphosphate (ATP) and antioxidants. In addition, cancer cells remodel the microenvironment through metabolites, promoting an immunosuppressive microenvironment. Herein, we discuss how the metabolism is reprogrammed in cancer cells and how the tumor microenvironment is educated via the metabolic products. We also highlight potential metabolic targets for cancer therapies.

New perspective toward nutritional support for malnourished cancer patients: Role of lipids

To improve the difficulties related to malnutrition, nutritional support has become an essential part of multidisciplinary comprehensive treatment for cancer. Lipids are essential nutrient source for the human body, and nowadays in clinical practices, it has a positive interventional effect on patients suffering from cancer. However, contribution of lipids in nutritional support of cancer patients is still poorly understood. Moreover, the sensory and physicochemical properties of lipids can severely restrict their applications in lipid-rich formula foods. In this review article, for the first time, we have presented a summary of the existing studies which were related to the associations between different lipids and improved malnutrition in cancer patients and discussed possible mechanisms. Subsequently, we discussed the challenges and effective solutions during processing of lipids into formula foods. Further, by considering existing problems in current lipid nutritional support, we proposed a novel method for the treatment of malnutrition, including developing individualized lipid nutrition for different patients depending on the individual's genotype and enterotype. Nonetheless, this review study provides a new direction for future research on nutritional support and the development of lipid-rich formula foods for cancer patients, and probably will help to improve the efficacy of lipids in the treatment of cancer malnutrition.

LXRα activation and Raf inhibition trigger lethal lipotoxicity in liver cancer

The success of molecular therapies targeting specific metabolic pathways in cancer is often limited by the plasticity and adaptability of metabolic networks. Here we show that pharmacologically induced lipotoxicity represents a promising therapeutic strategy for the treatment of hepatocellular carcinoma (HCC). LXRα-induced liponeogenesis and Raf-1 inhibition are synthetic lethal in HCC owing to a toxic accumulation of saturated fatty acids. Raf-1 was found to bind and activate SCD1, and conformation-changing DFG-out Raf inhibitors could disrupt this interaction, thereby blocking fatty acid desaturation and inducing lethal lipotoxicity. Studies in genetically engineered and nonalcoholic steatohepatitis-induced HCC mouse models and xenograft models of human HCC revealed that therapies comprising LXR agonists and Raf inhibitors were well tolerated and capable of overcoming therapy resistance in HCC. Conceptually, our study suggests pharmacologically induced lipotoxicity as a new mode for metabolic targeting of liver cancer.

Mechanisms of stearoyl CoA desaturase inhibitor sensitivity and acquired resistance in cancer

The lipogenic enzyme stearoyl CoA desaturase (SCD) plays a key role in tumor lipid metabolism and membrane architecture. SCD is often up-regulated and a therapeutic target in cancer. Here, we report the unexpected finding that median expression of SCD is low in glioblastoma relative to normal brain due to hypermethylation and unintentional monoallelic co-deletion with phosphatase and tensin homolog (PTEN) in a subset of patients. Cell lines from this subset expressed undetectable SCD, yet retained residual SCD enzymatic activity. Unexpectedly, these lines evolved to survive independent of SCD through unknown mechanisms. Cell lines that escaped such genetic and epigenetic alterations expressed higher levels of SCD and were highly dependent on SCD for survival. Last, we identify that SCD-dependent lines acquire resistance through a previously unknown FBJ murine osteosarcoma viral oncogene homolog B (FOSB)-mediated mechanism. Accordingly, FOSB inhibition blunted acquired resistance and extended survival of tumor-bearing mice treated with SCD inhibitor.

Apocryphal FADS2 activity promotes fatty acid diversification in cancer

Canonical fatty acid metabolism describes specific enzyme-substrate interactions that result in products with well-defined chain lengths, degree(s), and positions of unsaturation. Deep profiling of lipids across a range of prostate cancer cell lines reveals a variety of fatty acids with unusual site(s) of unsaturation that are not described by canonical pathways. The structure and abundance of these unusual lipids correlate with changes in desaturase expression and are strong indicators of cellular phenotype. Gene silencing and stable isotope tracing demonstrate that direct Δ6 and Δ8 desaturation of 14:0 (myristic), 16:0 (palmitic), and 18:0 (stearic) acids by FADS2 generate new families of unsaturated fatty acids (including n-8, n-10, and n-12) that have rarely-if ever-been reported in human-derived cells. Isomer-resolved lipidomics reveals the selective incorporation of these unusual fatty acids into complex structural lipids and identifies their presence in cancer tissues, indicating functional roles in membrane structure and signaling.

Tumor Cells and Cancer-Associated Fibroblasts: An Updated Metabolic Perspective

Simple Summary

Tumors are a complex ecosystem including not only cancer cells, but also many distinct cell types of the tumor micro-environment. While the Warburg effect assessing high glucose uptake in tumors was recognized a long time ago, metabolic heterogeneity within tumors has only recently been demonstrated. Indeed, several recent studies have highlighted other sources of carbon than glucose, including amino acids, fatty acids and lactate. These newly identified metabolic trajectories modulate key cancer cell features, such as invasion capacities. In addition, cancer metabolic heterogeneity is not restricted to cancer cells. Here, we also describe heterogeneity of Cancer-Associated Fibroblast (CAF) subpopulations and their complex metabolic crosstalk with cancer cells.

Abstract

During the past decades, metabolism and redox imbalance have gained considerable attention in the cancer field. In addition to the well-known Warburg effect occurring in tumor cells, numerous other metabolic deregulations have now been reported. Indeed, metabolic reprograming in cancer is much more heterogeneous than initially thought. In particular, a high diversity of carbon sources used by tumor cells has now been shown to contribute to this metabolic heterogeneity in cancer. Moreover, the molecular mechanisms newly highlighted are multiple and shed light on novel actors. Furthermore, the impact of this metabolic heterogeneity on tumor microenvironment has also been an intense subject of research recently. Here, we will describe the new metabolic pathways newly uncovered in tumor cells. We will also have a particular focus on Cancer-Associated Fibroblasts (CAF), whose identity, function and metabolism have been recently under profound investigation. In that sense, we will discuss about the metabolic crosstalk between tumor cells and CAF.

Combined transcriptomic and lipidomic analysis reveals aberrant lipid metabolism in central nervous system hemangioblastomas

Peritumoral cysts are commonly detected in the central nervous system tumors, especially hemangioblastomas (HBs). However, the molecular mechanisms driving their formation and propagation are still unknown. We conducted an integrated lipidomics and transcriptomics analysis on solid and cystic HB samples in order to elucidate the changes in the lipid profile and expression of lipid metabolism-related genes during cyst formation. Transcriptomic analysis revealed differential expression of several genes between the solid and cystic HBs, and those associated with lipid metabolism, such as ADCY4, MGLL, ACOT2, DGKG, SHC1 and LPAR2, were markedly dysregulated in the cystic HBs. The lipidomic analysis further showed a significant reduction in the abundance of triacylglycerol, ceramide, lysophosphatidylcholine and lysophosphatidylethanolamine, and an increase in phosphatidylcholine and phosphatidylethanolamine levels in the cystic HBs. Furthermore, bioinformatics analysis revealed altered lipid biosynthesis, glycerophospholipid metabolism and phospholipase activity in the cystic HBs. Taken together, our findings indicate that cyst formation in HBs is related with aberrant lipid metabolism.

SREBP1 suppresses the differentiation and epithelial function of hiPSC-derived endothelial cells by inhibiting the microRNA199b-5p pathway

Human induced pluripotent stem cell (hiPSC)-derived endothelial cell (hiPSC-EC) transplantation is a promising therapy for treating peripheral artery disease (PAD). However, the poor differentiation of hiPSCs limits their clinical application. Therefore, finding key factors that regulate cellular differentiation is crucial for improving the therapeutic efficacy of hiPSC-EC transplantation. Sterol regulatory element binding protein 1 (SREBP1) is a key regulator of lipid metabolism and stem cell differentiation. However, it remains unknown whether SREPBP1 modulates hiPSC differentiation. In this study, we showed that SREBP1 expression was negatively associated with hiPSC differentiation and EC function. The results show that SREBP1 binds to the promoter region of miR199b-5p and suppresses its transcription, resulting in the activation of Notch1 signaling. Blocking SREBP1 increased both hiPSC differentiation and EC angiogenesis. These findings demonstrate a novel role for SREBP1 in hiPSC differentiation and EC angiogenesis.

Extensive transcription mis-regulation and membrane defects in AdipoR2-deficient cells challenged with saturated fatty acids

How cells maintain vital membrane lipid homeostasis while obtaining most of their constituent fatty acids from a varied diet remains largely unknown. Here, we used transcriptomics, lipidomics, growth and respiration assays, and membrane property analyses in human HEK293 cells or human umbilical vein endothelial cells (HUVEC) to show that the function of AdipoR2 is to respond to membrane rigidification by regulating many lipid metabolism genes. We also show that AdipoR2-dependent membrane homeostasis is critical for growth and respiration in cells challenged with saturated fatty acids. Additionally, we found that AdipoR2 deficiency causes transcriptome and cell physiological defects similar to those observed in SREBP-deficient cells upon SFA challenge. Finally, we compared several genes considered important for lipid homeostasis, namely AdipoR2, SCD, FADS2, PEMT and ACSL4, and found that AdipoR2 and SCD are the most important among these to prevent membrane rigidification and excess saturation when human cells are challenged with exogenous SFAs. We conclude that AdipoR2-dependent membrane homeostasis is one of the primary mechanisms that protects against exogenous SFAs.

The diversity and breadth of cancer cell fatty acid metabolism

Tumor cellular metabolism exhibits distinguishing features that collectively enhance biomass synthesis while maintaining redox balance and cellular homeostasis. These attributes reflect the complex interactions between cell-intrinsic factors such as genomic-transcriptomic regulation and cell-extrinsic influences, including growth factor and nutrient availability. Alongside glucose and amino acid metabolism, fatty acid metabolism supports tumorigenesis and disease progression through a range of processes including membrane biosynthesis, energy storage and production, and generation of signaling intermediates. Here, we highlight the complexity of cellular fatty acid metabolism in cancer, the various inputs and outputs of the intracellular free fatty acid pool, and the numerous ways that these pathways influence disease behavior.

Metabolic crosstalk in the tumor microenvironment regulates antitumor immunosuppression and immunotherapy resisitance

The successful treatment of human cancers by immunotherapy has been made possible by breakthroughs in the discovery of immune checkpoint regulators, including CTLA-4 and PD-1/PD-L1. However, the immunosuppressive effect of the tumor microenvironment still represents an important bottleneck that limits the success of immunotherapeutic approaches. The tumor microenvironment influences the metabolic crosstalk between tumor cells and tumor-infiltrating immune cells, creating competition for the utilization of nutrients and promoting immunosuppression. In addition, tumor-derived metabolites regulate the activation and effector function of immune cells through a variety of mechanisms; in turn, the metabolites and other factors secreted by immune cells can also become accomplices to cancer development. Immune-metabolic checkpoint regulation is an emerging concept that is being studied with the aim of restoring the immune response in the tumor microenvironment. In this review, we summarize the metabolic reprogramming of various cell types present in the tumor microenvironment, with a focus on the interaction between the metabolic pathways of these cells and antitumor immunosuppression. We also discuss the main metabolic checkpoints that could provide new means of enhancing antitumor immunotherapy.

Differential gene expression in cisplatin-resistant and -sensitive testicular germ cell tumor cell lines

Testicular germ cell tumors (TGCTs) represent a well curable malignity due to their exceptional response to cisplatin (CDDP). Despite remarkable treatment results, approximately 5% of TGCT patients develop CDDP resistance and die. Exceptional curability makes TGCTs a highly valuable model system for studying the molecular mechanisms of CDDP sensitivity. Our study was aimed at revealing difference in gene expression between the CDDP-resistant and -sensitive TGCT cell lines, and hence at identifying candidate genes that could serve as potential biomarkers of CDDP response. Using gene expression array, we identified 281 genes that are differentially expressed in CDDP-resistant compared to -sensitive TGCT cell lines. The expression of 25 genes with the highest fold change was validated by RT-qPCR. Of them, DNMT3L, GAL, IGFBP2, IGFBP7, L1TD1, NANOG, NTF3, POU5F1, SOX2, WNT6, ZFP42, ID2, PCP4, SLC40A1 and TRIB3, displayed comparable expression change in gene expression array and RT-qPCR, when all CDDP-resistant TGCT cell lines were pairwise combined with all -sensitive ones. Products of the identified genes are pluripotency factors, or are involved in processes, such as cell metabolism, proliferation or migration. We propose that, after clinical validation, these genes could serve as prognostic biomarkers for early detection of CDDP response in TGCT patients.

Fat and Furious: Lipid Metabolism in Antitumoral Therapy Response and Resistance

Lipid metabolic reprogramming is an established trait of cancer metabolism that guides response and resistance to antitumoral therapies. Enhanced lipogenesis, increased lipid content (either free or stored into lipid droplets), and lipid-dependent catabolism sustain therapy desensitization and the emergence of a resistant phenotype of tumor cells exposed to chemotherapy or targeted therapies. Aberrant lipid metabolism, therefore, has emerged as a potential metabolic vulnerability of therapy-resistant cancers that could be exploited for therapeutic interventions or for identifying tumors more likely to respond to further lines of therapies. This review gathers recent findings on the role of aberrant lipid metabolism in influencing antitumoral therapy response and in sustaining the emergence of resistance.

Monoacylglycerol Lipase Knockdown Inhibits Cell Proliferation and Metastasis in Lung Adenocarcinoma

Abnormal metabolism is one of the hallmarks of cancer cells. Monoacylglycerol lipase (MGLL), a key enzyme in lipid metabolism, has emerged as an important regulator of tumor progression. In this study, we aimed to characterize the role of MGLL in the development of lung adenocarcinoma (LUAD). To this end, we used tissue microarrays to evaluate the expression of MGLL in LUAD tissue and assessed whether the levels of this protein are correlated with clinicopathological characteristics of LUAD. We found that the expression of MGLL is higher in LUAD samples than that in adjacent non-tumor tissues. In addition, elevated MGLL expression was found to be associated with advanced tumor progression and poor prognosis in LUAD patients. Functional studies further demonstrated that stable short hairpin RNA (shRNA)-mediated knockdown of MGLL inhibits tumor proliferation and metastasis, both in vitro and in vivo, and mechanistically, our data indicate that MGLL regulates Cyclin D1 and Cyclin B1 in LUAD cells. Moreover, we found that knockdown of MGLL suppresses the expression of matrix metalloproteinase 14 (MMP14) in A549 and H322 cells, and in clinical samples, expression of MMP14 is significantly correlated with MGLL expression. Taken together, our results indicate that MGLL plays an oncogenic role in LUAD progression and metastasis and may serve as a potential biomarker for disease prognosis and as a target for the development of personalized therapies.

Hepatic lipid profile in mice fed a choline-deficient, low-methionine diet resembles human non-alcoholic fatty liver disease

BACKGROUND

Emerging data support a role for lipids in non-alcoholic steatohepatitis (NASH) and hepatocellular carcinoma (HCC) in humans. With experimental models such data can be challenged or validated. Mice fed a low-methionine, choline-deficient (LMCD) diet develop NASH and, when injected with diethylnitrosamine (DEN), HCC. Here, lipidomic analysis was used to elucidate whether the NASH and HCC associated lipid derangements resemble the lipid profile of the human disease.

METHODS

Lipids were measured in the liver of mice fed a control or a LMCD diet for 16 weeks. DEN was injected at young age to initiate hepatocarcinogenesis. DEN treatment associated changes of the lipid composition and the tumor lipidome were evaluated.

RESULTS

LMCD diet fed mice accumulated ceramides and triacylglycerols in the liver. Phospholipids enriched with monounsaturated fatty acids were also increased, whereas hepatic cholesterol levels remained unchanged in the LMCD model. Phosphatidylcholine and lysophosphatidylcholine concentrations declined in the liver of LMCD diet fed mice. The changes of most lipids associated with LMCD diet feeding were similar between water and DEN injected mice. Several polyunsaturated (PU) diacylglycerol species were already low in the liver of DEN injected mice fed the control diet. Tumors developed in the liver of LMCD diet fed mice injected with DEN. The tumor specific lipid profile, however, did not resemble the decrease of ceramides and PU phospholipids, which was consistently described in human HCC. Triacylglycerols declined in the cancer tissues, which is in accordance with a low expression of lipogenic enzymes in the tumors.

CONCLUSIONS

The LMCD model is suitable to study NASH associated lipid reprogramming. Hepatic lipid profile was modestly modified in the DEN injected mice suggesting a function of these derangements in carcinogenesis. Lipid composition of liver tumors did not resemble the human HCC lipidome, and most notably, lipogenesis and triacylglycerol levels were suppressed.

The Lipid Metabolic Landscape of Cancers and New Therapeutic Perspectives

Lipid metabolism reprograming, as a hallmark of malignancy, has received renewed interest in recent years in such areas as energy sources, cell membrane components, and signaling molecules involved in the rapid tumor growth and the adaptation to the tumor microenvironment. Lipid metabolism deregulation in cancer involves multiple aspects, including an increased lipid uptake, endogenous de novo fatty acid synthesis, fatty acid oxidation, and cholesterol accumulation, thereby promoting tumor growth and progression. Recent advances in the understanding of specific metabolic alterations in cancer reveal novel pathogenesis mechanisms and a growing number of drugs targeting lipid metabolism have been applied in anti-tumor therapy. Thus, this review discusses the lipid metabolic landscape of cancers and the interplay with oncogenic signaling, and summarizes potential therapeutic targets to improve the therapeutic efficiency in cancer patients, in order to provide more reference and thinking for the treatment of lipid metabolism of cancer patients.

Multifaceted regulation and functions of fatty acid desaturase 2 in human cancers

As an important hallmark of metabolic reprogramming in cancer, a disruption in fatty acid metabolism contributes to tumor proliferation, cell migration and invasion, and other tumor cell behaviors. In recent years, more and more studies have been conducted on fatty acid desaturase 2 (FADS2), the first rate-limiting enzyme for the biosynthesis of polyunsaturated fatty acids. These studies have found that FADS2 is abnormally expressed in cancers of the breast, lung, liver, and esophagus; melanoma; leukemia; and other malignant tumors. Furthermore, its expression is significantly correlated with tumor proliferation, cell migration and invasion, clonal formation, angiogenesis, ferroptosis, resistance to radiotherapy, histological grade, metastasis to lymph nodes, clinical stage, and prognosis. The abnormal expression of FADS2 results in an imbalance of cell membrane phospholipids, which disrupts the fluidity of the membrane structure and the transmission of signals and promotes the production of proinflammatory factors and arachidonic acid (AA) metabolites, ultimately harming human health. This article aims to systematically review the structural characteristics of FADS2; its function, expression, and mechanism of action; and the factors affecting its activity. This review also provides new ideas and strategies for the development of treatments aimed at the metabolic reprogramming of tumors.

Targeting Metabolic Plasticity and Flexibility Dynamics for Cancer Therapy

Cancer cells continuously rewire their metabolism to fulfill their need for rapid growth and survival while subject to changes in environmental cues. Thus, a vital component of a cancer cell lies in its metabolic adaptability. The constant demand for metabolic alterations requires flexibility, that is, the ability to utilize different metabolic substrates; as well as plasticity, that is, the ability to process metabolic substrates in different ways. In this review, we discuss how dynamic changes in cancer metabolism affect tumor progression and the consequential implications for cancer therapy. SIGNIFICANCE: Recognizing cancer dynamic metabolic adaptability as an entity can lead to targeted therapy that is expected to decrease drug resistance.

The Metabolic Underpinnings of Ferroptosis

Acute or chronic cellular stress resulting from aberrant metabolic and biochemical processes may trigger a pervasive non-apoptotic form of cell death, generally known as ferroptosis. Ferroptosis is unique among the different cell death modalities, as it has been mostly linked to pathophysiological conditions and because several metabolic pathways, such as (seleno)thiol metabolism, fatty acid metabolism, iron handling, mevalonate pathway, and mitochondrial respiration, directly impinge on the cells' sensitivity toward lipid peroxidation and ferroptosis. Additionally, key cellular redox systems, such as selenium-dependent glutathione peroxidase 4 and the NAD(P)H/ferroptosis suppressor protein-1/ubiquinone axis, are at play that constantly surveil and neutralize oxidative damage to cellular membranes. Since this form of cell death emerges to be the root cause of a number of diseases and since it offers various pharmacologically tractable nodes for therapeutic intervention, there has been overwhelming interest in the last few years aiming for a better molecular understanding of the ferroptotic death process.

Lipid Regulatory Proteins as Potential Therapeutic Targets for Ovarian Cancer in Obese Women

Obesity has become a recognized global epidemic that is associated with numerous comorbidities including type II diabetes, cardiovascular disease, hypertension, and cancer incidence and progression. Ovarian cancer (OvCa) has a unique mechanism of intra-peritoneal metastasis, already present in 80% of women at the time of diagnosis, making it the fifth leading cause of death from gynecological malignancy. Meta-analyses showed that obesity increases the risk of OvCa progression, leads to enhanced overall and organ-specific tumor burden, and adversely effects survival of women with OvCa. Recent data discovered that tumors grown in mice fed on a western diet (40% fat) have elevated lipid levels and a highly increased expression level of sterol regulatory element binding protein 1 (SREBP1). SREBP1 is a master transcription factor that regulates de novo lipogenesis and lipid homeostasis, and induces lipogenic reprogramming of tumor cells. Elevated SREBP1 levels are linked to cancer cell proliferation and metastasis. This review will summarize recent findings to provide a current understanding of lipid regulatory proteins in the ovarian tumor microenvironment with emphasis on SREBP1 expression in the obese host, the role of SREBP1 in cancer progression and metastasis, and potential therapeutic targeting of SREBPs and SREBP-pathway genes in treating cancers, particularly in the context of host obesity.

A Lipidomic Signature Complements Stemness Features Acquisition in Liver Cancer Cells

Lipid catabolism and anabolism changes play a role in stemness acquisition by cancer cells, and cancer stem cells (CSCs) are particularly dependent on the activity of the enzymes involved in these processes. Lipidomic changes could play a role in CSCs’ ability to cause disease relapse and chemoresistance. The exploration of lipid composition and metabolism changes in CSCs in the context of hepatocellular cancer (HCC) is still incomplete and their lipidomic scenario continues to be elusive. We aimed to evaluate through high-throughput mass spectrometry (MS)-based lipidomics the levels of the members of the six major classes of sphingolipids and phospholipids in two HCC cell lines (HepG2 and Huh-7) silenced for the expression of histone variant macroH2A1 (favoring stemness acquisition), or silenced for the expression of focal adhesion tyrosine kinase (FAK) (hindering aggressiveness and stemness). Transcriptomic changes were evaluated by RNA sequencing as well. We found definite lipidomic and transcriptomic changes in the HCC lines upon knockdown (KD) of macroH2A1 or FAK, in line with the acquisition or loss of stemness features. In particular, macroH2A1 KD increased total sphingomyelin (SM) levels and decreased total lysophosphatidylcholine (LPC) levels, while FAK KD decreased total phosphatidylcholine (PC) levels. In conclusion, in HCC cell lines knocked down for specific signaling/epigenetic processes driving opposite stemness potential, we defined a lipidomic signature that hallmarks hepatic CSCs to be exploited for therapeutic strategies.

Polyunsaturated fatty acid biosynthesis pathway and genetics. implications for interindividual variability in prothrombotic, inflammatory conditions such as COVID-19✰,✰✰,★,★★

COVID-19 symptoms vary from silence to rapid death, the latter mediated by both a cytokine storm and a thrombotic storm. SARS-CoV (2003) induces Cox-2, catalyzing the synthesis, from highly unsaturated fatty acids (HUFA), of eicosanoids and docosanoids that mediate both inflammation and thrombosis. HUFA balance between arachidonic acid (AA) and other HUFA is a likely determinant of net signaling to induce a healthy or runaway physiological response. AA levels are determined by a non-protein coding regulatory polymorphisms that mostly affect the expression of FADS1, located in the FADS gene cluster on chromosome 11. Major and minor haplotypes in Europeans, and a specific functional insertion-deletion (Indel), rs66698963, consistently show major differences in circulating AA (>50%) and in the balance between AA and other HUFA (47-84%) in free living humans; the indel is evolutionarily selective, probably based on diet. The pattern of fatty acid responses is fully consistent with specific genetic modulation of desaturation at the FADS1-mediated 20:3→20:4 step. Well established principles of net tissue HUFA levels indicate that the high linoleic acid and low alpha-linoleic acid in populations drive the net balance of HUFA for any individual. We predict that fast desaturators (insertion allele at rs66698963; major haplotype in Europeans) are predisposed to higher risk and pathological responses to SARS-CoV-2 could be reduced with high dose omega-3 HUFA.

Therapy-Induced Modulation of the Tumor Microenvironment: New Opportunities for Cancer Therapies

Advances in immunotherapy have achieved remarkable clinical outcomes in tumors with low curability, but their effects are limited, and increasing evidence has implicated tumoral and non-tumoral components of the tumor microenvironment as critical mediators of cancer progression. At the same time, the clinical successes achieved with minimally invasive and optically-guided surgery and image-guided and ablative radiation strategies have been successfully implemented in clinical care. More effective, localized and safer treatments have fueled strong research interest in radioimmunotherapy, which has shown the potential immunomodulatory effects of ionizing radiation. However, increasingly more observations suggest that immunosuppressive changes, metabolic remodeling, and angiogenic responses in the local tumor microenvironment play a central role in tumor recurrence. In this review, we address challenges to identify responders vs. non-responders to the immune checkpoint blockade, discuss recent developments in combinations of immunotherapy and radiotherapy for clinical evaluation, and consider the clinical impact of immunosuppressive changes in the tumor microenvironment in the context of surgery and radiation. Since the therapy-induced modulation of the tumor microenvironment presents a multiplicity of forms, we propose that overcoming microenvironment related resistance can become clinically relevant and represents a novel strategy to optimize treatment immunogenicity and improve patient outcome.

Epistatic evidence for gender-dependant slow neurotransmission signalling in substance use disorders: PPP1R12B versus PPP1R1B

BACKGROUND

Slow neurotransmission including DARPP-32 signalling is implicated in substance use disorders (SUDs) by experimental systems but not yet in the human aetiology. PPP1R12B, encoding another protein in the DARPP-32 family, hasn't been studied in the brain.

METHODS

Brain-regional gene activity was assessed in three different animal models of SUDs for mRNA level alterations. Genetic associations were assessed by meta-analysis of pre-existing dbGaP GWAS datasets for main effects and epistasis with known genetic risks, followed by cell type-specific pathway delineation. Parkinson's disease (PD) was included as a dopamine-related disease control for SUDs.

FINDINGS

In animal models of SUDs, environmentally-altered PPP1R12B expression sex-dependently involves motivation-related brain regions. In humans with polysubstance abuse, meta-analysis of pre-existing datasets revealed that PPP1R12B and PPP1R1B, although expressed in dopamine vs. dopamine-recipient neurons, exerted similar interactions with known genetic risks such as ACTR1B and DRD2 in men but with ADH1B, HGFAC and DRD3 in women. These interactions reached genome-wide significances (P_meta<10^-20) for SUDs but not for PD (disease selectivity: P = 4.8 × 10^-142, OR = 6.7 for PPP1R12B; P = 8.0 × 10^-8, OR = 2.1 for PPP1R1B). CADM2 was the common risk in the molecular signalling regardless of gender and cell type.

INTERPRETATION

Gender-dependant slow neurotransmission may convey both genetic and environmental vulnerabilities selectively to SUDs.

FUNDING

Grants from National Institute on Drug Abuse (NIDA) and National Institute on Alcohol Abuse and Alcoholism (NIAAA) of U.S.A. and National Natural Science Foundation of China (NSFC).

Cancer Plasticity: The Role of mRNA Translation

Tumor progression is associated with dedifferentiated histopathologies concomitant with cancer cell survival within a changing, and often hostile, tumor microenvironment. These processes are enabled by cellular plasticity, whereby intracellular cues and extracellular signals are integrated to enable rapid shifts in cancer cell phenotypes. Cancer cell plasticity, at least in part, fuels tumor heterogeneity and facilitates metastasis and drug resistance. Protein synthesis is frequently dysregulated in cancer, and emerging data suggest that translational reprograming collaborates with epigenetic and metabolic programs to effectuate phenotypic plasticity of neoplasia. Herein, we discuss the potential role of mRNA translation in cancer cell plasticity, highlight emerging histopathological correlates, and deliberate on how this is related to efforts to improve understanding of the complex tumor ecology.

Nutrient metabolism and cancer in the in vivo context: a metabolic game of give and take

Nutrients are indispensable resources that provide the macromolecular building blocks and energy requirements for sustaining cell growth and survival. Cancer cells require several key nutrients to fulfill their changing metabolic needs as they progress through stages of development. Moreover, both cell-intrinsic and microenvironment-influenced factors determine nutrient dependencies throughout cancer progression-for which a comprehensive characterization remains incomplete. In addition to the widely studied role of genetic alterations driving cancer metabolism, nutrient use in cancer tissue may be affected by several factors including the following: (i) diet, the primary source of bodily nutrients which influences circulating metabolite levels; (ii) tissue of origin, which can influence the tumor's reliance on specific nutrients to support cell metabolism and growth; (iii) local microenvironment, which dictates the accessibility of nutrients to tumor cells; (iv) tumor heterogeneity, which promotes metabolic plasticity and adaptation to nutrient demands; and (v) functional demand, which intensifies metabolic reprogramming to fuel the phenotypic changes required for invasion, growth, or survival. Here, we discuss the influence of these factors on nutrient metabolism and dependence during various steps of tumor development and progression.

Metabolic adaptation of acute lymphoblastic leukemia to the central nervous system microenvironment is dependent on Stearoyl CoA desaturase

Metabolic reprogramming is a key hallmark of cancer, but less is known about metabolic plasticity of the same tumor at different sites. Here, we investigated the metabolic adaptation of leukemia in two different microenvironments, the bone marrow and the central nervous system (CNS). We identified a metabolic signature of fatty-acid synthesis in CNS leukemia, highlighting Stearoyl-CoA desaturase (SCD1) as a key player. In vivo SCD1 overexpression increases CNS disease, whilst genetic or pharmacological inhibition of SCD1 decreases CNS load. Overall, we demonstrated that leukemic cells dynamically rewire metabolic pathways to suit local conditions and that targeting these adaptations can be exploited therapeutically.

Multifunctional Reactive MALDI Matrix Enabling High-Lateral Resolution Dual Polarity MS Imaging and Lipid C═C Position-Resolved MS2 Imaging

Local lipid variations in tissues are readily revealed with mass spectrometry imaging (MSI) methods, and the resulting lipid distributions serve as bioanalytical signatures to reveal cell- or tissue-specific lipids. Comprehensive MSI lipid mapping requires measurements in both ion polarities. Additionally, structural lipid characterization is necessary to link the lipid structure to lipid function. Whereas some structural elements of lipids are readily derived from high-resolution mass spectrometry (MS) and tandem-MS (MSⁿ), the localization of C═C double bonds (DBs) requires specialized fragmentation and/or functionalization methods. In this work, we identify a multifunctional matrix-assisted laser desorption/ionization (MALDI) matrix for spatially resolved lipidomics investigations that reacts with lipids in Paternò-Büchi (PB) reactions during laser irradiation facilitating DB-position assignment and allows dual-polarity high-resolution MALDI-MSI and MALDI MS²I studies. By screening 12 compounds for improved ionization efficiency in positive-/negative-ion mode and the functionalization yield compared to the previously introduced reactive MALDI matrix benzophenone, 2-benzoylpyridine (BzPy) is identified as the best candidate. The new matrix enables DB localization of authentic standards belonging to 12 lipid classes and helps to assign 133/58 lipid features in positive-/negative-ion mode from mouse cerebellum tissue. The analytical capabilities of BzPy as a multifunctional MALDI-MSI matrix are demonstrated by imaging endogenous and PB-functionalized lipids in mouse kidney sections with 7 μm lateral resolution in both ion modes. Tracking diagnostic lipid DB-position fragment ions in mouse pancreatic tissue with down to 10 μm pixel size allows us to identify the islets of Langerhans associated with lipid isomer upregulation and depletion.

Emerging mechanisms and applications of ferroptosis in the treatment of resistant cancers

The development of chemotherapy drugs has promoted anticancer treatment, but the effect on tumours is not clear because of treatment resistance; thus, it is necessary to further understand the mechanism of cell death to explore new therapeutic targets. As a new type of programmed cell death, ferroptosis is increasingly being targeted in the treatment of many cancers with clinical drugs and experimental compounds. Ferroptosis is stimulated in tumours with inherently high levels of ferrous ions by a reaction with abundant polyunsaturated fatty acids and the inhibition of antioxidant enzymes, which can overcome treatment resistance in cancers mainly through GPX4. In this review, we focus on the intrinsic cellular regulators against ferroptosis in cancer resistance, such as GPX4, NRF2 and the thioredoxin system. We summarize the application of novel compounds and drugs to circumvent treatment resistance. We also introduce the application of nanoparticles for the treatment of resistant cancers. In conclusion, targeting ferroptosis represents a considerable strategy for resistant cancer treatment.

NASH, Fibrosis and Hepatocellular Carcinoma: Lipid Synthesis and Glutamine/Acetate Signaling

Primary liver cancer is predicted to be the sixth most common cancer and the fourth leading cause of cancer mortality worldwide. Recent studies identified nonalcoholic fatty liver disease (NAFLD) as the underlying cause in 13-38.2% of patients with hepatocellular carcinoma unrelated to viral hepatitis and alcohol abuse. NAFLD progresses to nonalcoholic steatohepatitis (NASH), which increases the risk for the development of liver fibrosis, cirrhosis, and hepatocellular carcinoma. NAFLD is characterized by dysregulation of lipid metabolism. In addition, lipid metabolism is effected not only in NAFLD, but also in a broad range of chronic liver diseases and tumor development. Cancer cells manipulate a variety of metabolic pathways, including lipid metabolism, in order to build up their own cellular components. Identifying tumor dependencies on lipid metabolism would provide options for novel targeting strategies. This review article summarizes the research evidence on metabolic reprogramming and focuses on lipid metabolism in NAFLD, NASH, fibrosis, and cancer. As alternative routes of acetyl-CoA production for fatty acid synthesis, topics on glutamine and acetate metabolism are included. Further, studies on small compound inhibitors targeting lipid metabolism are discussed. Understanding reprogramming strategies in liver diseases, as well as the visualization of the metabolism reprogramming networks, could uncover novel therapeutic options.

Cancer diets for cancer patients: Lessons from mouse studies and new insights from the study of fatty acid metabolism in tumors

Specific diets for cancer patients have the potential to offer an adjuvant modality to conventional anticancer therapy. If the concept of starving cancer cells from nutrients to inhibit tumor growth is quite simple, the translation into the clinics is not straightforward. Several diets have been described including the Calorie-restricted diet based on a reduction in carbohydrate intake and the Ketogenic diet wherein the low carbohydrate content is compensated by a high fat intake. As for other diets that deviate from normal composition only by one or two amino acids, these diets most often revealed a reduction in tumor growth in mice, in particular when associated with chemo- or radiotherapy. By contrast, in cancer patients, the interest of these diets is almost exclusively supported by case reports precluding any conclusions on their real capacity to influence disease outcome. In parallel, the field of tumor lipid metabolism has emerged in the last decade offering a better understanding of how fatty acids are captured, synthesized or stored as lipid droplets in cancers. Fatty acids participate to cancer cell survival in the hypoxic and acidic tumor microenvironment and also support proliferation and invasiveness. Interestingly, while such addiction for fatty acids may account for cancer progression associated with high fat diet, it could also represent an Achilles heel for tumors. In particular n-3 polyunsaturated fatty acids represent a class of lipids that can exert potent cytotoxic effects in tumors and therefore represent an attractive diet supplementation to improve cancer patient outcomes.

In Situ Metabolic Characterisation of Breast Cancer and Its Potential Impact on Therapy

In spite of tremendous developments in breast cancer treatment, the relatively high incidence of relapsing cases indicates a great need to find new therapeutic strategies in recurrent, metastatic and advanced cases. The bioenergetic needs of growing tumours at the primary site or in metastases-accumulating genomic alterations and further heterogeneity-are supported by metabolic rewiring, an important hallmark of cancer. Adaptation mechanisms as well as altered anabolic and catabolic processes balance according to available nutrients, energy, oxygen demand and overgrowth or therapeutic resistance. Mammalian target of rapamycin (mTOR) hyperactivity may contribute to this metabolic plasticity and progression in breast carcinomas. We set out to assess the metabolic complexity in breast cancer cell lines and primary breast cancer cases. Cellular metabolism and mTOR-related protein expression were characterised in ten cell lines, along with their sensitivity to specific mTOR and other metabolic inhibitors. Selected immunohistochemical reactions were performed on ~100 surgically removed breast cancer specimens. The obtained protein expression scores were correlated with survival and other clinicopathological data. Metabolic and mTOR inhibitor mono-treatments had moderate antiproliferative effects in the studied cell lines in a subtype-independent manner, revealing their high adaptive capacity and survival/growth potential. Immunohistochemical analysis of p-S6, Rictor, lactate dehydrogenase A, glutaminase, fatty acid synthase and carnitine palmitoyltransferase 1A in human samples identified high mTOR activity and potential metabolic plasticity as negative prognostic factors for breast cancer patients, even in subtypes generally considered as low-risk. According to our results, breast cancer is characterised by considerable metabolic diversity, which can be targeted by combining antimetabolic treatments and recent therapies. Alterations in these pathways may provide novel targets for future drug development in breast cancer. We also propose a set of immunostainings for scoring metabolic heterogeneity in individual cases in order to select patients who may benefit from more accurate follow-up and specific therapies.

Y-box binding protein 1 acts as a negative regulator of stearoyl CoA desaturase 1 in clear cell renal cell carcinoma

Y-box binding protein 1 (YB-1) is a regulatory protein associated with oncogenesis and poor prognosis in patients with cancer. In the cell, YB-1 functions as a DNA and RNA binding protein that promotes or suppresses expression of target genes. The cancer-promoting activity of YB-1 is mediated through its activation of oncogenes and repression of tumor suppressor genes. Lipogenic enzyme stearoyl-CoA desaturase (SCD1) drives the production of endogenous monounsaturated fatty acids (MUFAs) in cells and protects against toxic buildup of saturated fatty acids. Clear cell renal cell carcinoma (ccRCC) is often characterized by aberrantly high SCD1 expression and cytosolic accumulation of unsaturated fatty acids. In the present study, a proteomics screen of cells treated with inhibitors of SCD1 supported a potential relationship between YB-1 and SCD1. It was revealed that the presence of MUFAs led to increased protein synthesis and increased expression of high molecular weight forms of YB-1 in ccRCC cells, but not in non-tumorigenic cells. Ectopic expression of YB-1 led to decreased expression levels of SCD1 protein and mRNA in ccRCC cell lines. Conversely, targeted knockdown of YB-1 increased SCD1 mRNA abundance. Analysis of ccRCC patient data from The Cancer Proteome Atlas database showed YB-1 expression was negatively associated with survival, whereas SCD1 was associated with improved survival. These data suggested an antagonistic relationship between YB-1 and SCD1 that may influence survival of patients with ccRCC.

Fatty Acids and Membrane Lipidomics in Oncology: A Cross-Road of Nutritional, Signaling and Metabolic Pathways

Fatty acids are closely involved in lipid synthesis and metabolism in cancer. Their amount and composition are dependent on dietary supply and tumor microenviroment. Research in this subject highlighted the crucial event of membrane formation, which is regulated by the fatty acids' molecular properties. The growing understanding of the pathways that create the fatty acid pool needed for cell replication is the result of lipidomics studies, also envisaging novel fatty acid biosynthesis and fatty acid-mediated signaling. Fatty acid-driven mechanisms and biological effects in cancer onset, growth and metastasis have been elucidated, recognizing the importance of polyunsaturated molecules and the balance between omega-6 and omega-3 families. Saturated and monounsaturated fatty acids are biomarkers in several types of cancer, and their characterization in cell membranes and exosomes is under development for diagnostic purposes. Desaturase enzymatic activity with unprecedented de novo polyunsaturated fatty acid (PUFA) synthesis is considered the recent breakthrough in this scenario. Together with the link between obesity and cancer, fatty acids open interesting perspectives for biomarker discovery and nutritional strategies to control cancer, also in combination with therapies. All these subjects are described using an integrated approach taking into account biochemical, biological and analytical aspects, delineating innovations in cancer prevention, diagnostics and treatments.