A novel fatty acid-binding protein 5-estrogen-related receptor α signaling pathway promotes cell growth and energy metabolism in prostate cancer cells

Fatty acid binding protein 5 inhibitors as novel anticancer agents against metastatic castration-resistant prostate cancer

Prostate cancer (PCa) is one of the most common malignancies diagnosed among men and is the second leading cause of cancer-related death. Despite recent advancements in early diagnosis of PCa, androgen deprivation therapy (ADT) remains the most common treatment of PCa. Docetaxel (DTX) and Cabazitaxel (CTX) are two of the most extensively used drugs for metastatic castration-resistant prostate cancer (mCRPC). However, there is a clear medical need for newer and more efficacious therapies for CRPC. FABP5 is overexpressed in prostate cancer cells and chaperones fatty acids to PPARs, which leads to the upregulation of proangiogenic factors, resulting in cell survival and metastasis. The critical role and upregulation of FABP5 in PCa make FABP5 an excellent druggable target for CRPC. We reported a promising anti-PCa activity of truxillic acid monoester (TAME)-based FABP5 inhibitors (SB-FIs) and their synergy with DTX and CTX in vitro and in vivo against PC-3 cells and PC-3 tumor xenografts. In the present work, we performed an extensive SAR study on the potencies of 2nd- and 3rd-generation SB-FIs against PC-3 and RCaP cell lines. RCaP is a mouse PCa cell line, resistant to anti-androgen and first-line taxane chemotherapies, and shows a high level of the Fabp5-gene. This SAR study led to the identification of a number of 3rd-generation SB-FIs with strong cytotoxicity against these two PCa cell lines. Cell cycle analysis of selected SB-FIs revealed a clear evolution of apoptotic potency in the 1st-, 2nd- and 3rd-generation SB-FIs. Since taxanes, DTX and CTX, are ineffective against RCaP cell line, we selected a topoisomerase I inhibitor, topotecan (TPT) as a replacement for taxanes. We screened the library of SB-FIs for synergy with TPT and identified 3 SB-FIs (L3, α-11 and α-4), exhibiting strong synergy, which could remarkably expand the therapeutic window of TPT.

Effects of FABP5 Expression on Clinicopathological and Survival Characteristics in Digestive System Malignancies: A Systematic Review and Meta-Analysis

BACKGROUND

Digestive system malignancies are a major global health burden, and the role of fatty acid binding protein 5 (FABP5) in these tumors remains controversial.

AIMS

This meta-analysis aimed to evaluate the correlation between FABP5 expression and clinicopathological features, as well as survival outcomes in digestive system malignancies.

MATERIALS AND METHODS

Data from 11 studies (1207 patients) retrieved from PubMed, Embase, Cochrane Library, CNKI, and WanFang were analyzed.

RESULTS

FABP5 overexpression was associated with poorer overall survival (OS), larger tumor size, advanced UICC stage, and increased risk of vascular invasion and lymph node metastasis. Notably, FABP5 overexpression is particularly associated with poorer OS in the subgroup of digestive tract malignancies and larger tumor sizes in the subgroup of Chinese patients.

DISCUSSION

Cellular experiments demonstrated that FABP5 overexpression enhances proliferation, migration, and invasion in hepatocellular carcinoma (Huh7) and gastric cancer (HGC-27) cell lines, while FABP5 knockdown reduces these effects. Mechanistically, FABP5 may drive tumor progression through PPARβ/δ signaling, epithelial-mesenchymal transition induction, angiogenesis regulation, and potential effects on fatty acid metabolism and hypoxia-related pathways.

CONCLUSION

FABP5 overexpression correlates with adverse clinicopathological features and prognosis in digestive system malignancies, suggesting its potential as a biomarker for these tumors. Further research is warranted.

Oleate alters the immune response in non-small cell lung adenocarcinoma through regulation of HMGB1 release

Background: Cancer cell evasion of the immune response is critical to cancer development and metastases. Clinicians' ability to kickstart the immune system to target these rogue cells is an ever-growing area of research and medicine. This study delved into the relationship between lipid metabolism, High Mobility Group Box 1 protein (HMGB1)-a pro-inflammatory damage-associated molecular pattern protein-and immune regulation within non-small cell lung adenocarcinoma (NSCLC). Method: To address this question, we used a combination of proteomics, molecular biology, and bioinformatic techniques to investigate the relationship between fatty acids and immune signals within NSCLC. Results: We found that the expression of stearoyl CoA desaturase 1 (SCD1) was decreased in NSCLC tumors compared to normal tissues. This emphasized the critical role of lipid metabolism in tumor progression. Interestingly, monounsaturated fatty acid (MUFA) availability affected the expression of programmed death ligand-1 (PD-L1), a pivotal immune checkpoint target in lung cancer cells and immune cells, as well as HMGB1, suggesting a novel approach to modulating the immune response. This study uncovered a complex interplay between SCD1, PD-L1, and HMGB1, influencing the immunological sensitivity of tumors. Conclusion: Our work underscores the critical importance of understanding the intricate relationships between lipid metabolism and immune modulation to develop more effective NSCLC treatments and personalized therapies. As we continue to explore these connections, we hope to contribute significantly to the ever-evolving field of cancer research, improving patient outcomes and advancing precision medicine in NSCLC.

Importance of fatty acid binding proteins in cellular function and organismal metabolism

Fatty acid binding proteins (Fabps) are small soluble proteins that are abundant in the cytosol. These proteins are known to bind a myriad of small hydrophobic molecules and have been postulated to serve a variety of roles, yet their precise functions have remained an enigma over half a century of study. Here, we consider recent findings, along with the cumulative findings contributed by many laboratories working on Fabps over the last half century, to synthesize a new outlook for what functions Fabps serve in cells and organisms. Collectively, the findings illustrate that Fabps function as versatile multi-purpose devices serving as sensors, conveyors and modulators to enable cells to detect and handle a specific class of metabolites, and to adjust their metabolic capacity and efficiency.

FABP5 Inhibition against PTEN-Mutant Therapy Resistant Prostate Cancer

Resistance to standard of care taxane and androgen deprivation therapy (ADT) causes the vast majority of prostate cancer (PC) deaths worldwide. We have developed RapidCaP, an autochthonous genetically engineered mouse model of PC. It is driven by the loss of PTEN and p53, the most common driver events in PC patients with life-threatening diseases. As in human ADT, surgical castration of RapidCaP animals invariably results in disease relapse and death from the metastatic disease burden. Fatty Acid Binding Proteins (FABPs) are a large family of signaling lipid carriers. They have been suggested as drivers of multiple cancer types. Here we combine analysis of primary cancer cells from RapidCaP (RCaP cells) with large-scale patient datasets to show that among the 10 FABP paralogs, FABP5 is the PC-relevant target. Next, we show that RCaP cells are uniquely insensitive to both ADT and taxane treatment compared to a panel of human PC cell lines. Yet, they share an exquisite sensitivity to the small-molecule FABP5 inhibitor SBFI-103. We show that SBFI-103 is well tolerated and can strongly eliminate RCaP tumor cells in vivo. This provides a pre-clinical platform to fight incurable PC and suggests an important role for FABP5 in PTEN-deficient PC.

Fatty-Acid-Binding Proteins: From Lipid Transporters to Disease Biomarkers

Fatty-acid-binding proteins (FABPs) serve a crucial role in the metabolism and transport of fatty acids and other hydrophobic ligands as an intracellular protein family. They are also recognized as a critical mediator in the inflammatory and ischemic pathways. FABPs are found in a wide range of tissues and organs, allowing them to contribute to various disease/injury developments that have not been widely discussed. We have collected and analyzed research journals that have investigated the role of FABPs in various diseases. Through this review, we discuss the findings on the potential of FABPs as biomarkers for various diseases in different tissues and organs, looking at their expression levels and their roles in related diseases according to available literature data. FABPs have been reported to show significantly increased expression levels in various tissues and organs associated with metabolic and inflammatory diseases. Therefore, FABPs are a promising novel biomarker that needs further development to optimize disease diagnosis and prognosis methods along with previously discovered markers.

Unsaturated fatty acid alters the immune response in non-small cell lung adenocarcinoma through regulation of HMGB1 trafficking

Cancer cell evasion of the immune response is critical to cancer development and metastases. The ability of clinicians to kickstart the immune system to target these rogue cells is an ever-growing area of research and medicine. In this study, we delved into the relationship between lipid metabolism, High Mobility Group Box 1 protein (HMGB1), and immune regulation within non-small cell lung adenocarcinoma (NSCLC), shedding light on novel therapeutic avenues and potential personalized approaches for patients. We found that the expression of stearoyl CoA desaturase 1 (SCD1) was decreased in NSCLC tumors compared to normal tissues. This emphasized the critical role of lipid metabolism in tumor progression. Interestingly, monounsaturated fatty acid (MUFA) availability impacted the expression of programmed death receptor ligand -1 (PD-L1), a pivotal immune checkpoint target in lung cancer cells and immune cells, suggesting a novel approach to modulating the immune response. This study uncovered a complex interplay between HMGB1, SCD1, and PD-L1, influencing the immunological sensitivity of tumors. Our work underscores the importance of understanding the intricate relationships between lipid metabolism and immune modulation to develop more effective NSCLC treatments and personalized therapies. As we continue to explore these connections, we hope to contribute to the ever-evolving field of cancer research, improving patient outcomes and advancing precision medicine in NSCLC.

Fatty acid binding protein 5 regulates docetaxel sensitivity in taxane-resistant prostate cancer cells

Prostate cancer is a leading cause of cancer-related deaths in men in the United States. Although treatable when detected early, prostate cancer commonly transitions to an aggressive castration-resistant metastatic state. While taxane chemotherapeutics such as docetaxel are mainstay treatment options for prostate cancer, taxane resistance often develops. Fatty acid binding protein 5 (FABP5) is an intracellular lipid chaperone that is upregulated in advanced prostate cancer and is implicated as a key driver of its progression. The recent demonstration that FABP5 inhibitors produce synergistic inhibition of tumor growth when combined with taxane chemotherapeutics highlights the possibility that FABP5 may regulate other features of taxane function, including resistance. Employing taxane-resistant DU145-TXR cells and a combination of cytotoxicity, apoptosis, and cell cycle assays, our findings demonstrate that FABP5 knockdown sensitizes the cells to docetaxel. In contrast, docetaxel potency was unaffected by FABP5 knockdown in taxane-sensitive DU145 cells. Taxane-resistance in DU145-TXR cells stems from upregulation of the P-glycoprotein ATP binding cassette subfamily B member 1 (ABCB1). Expression analyses and functional assays confirmed that FABP5 knockdown in DU145-TXR cells markedly reduced ABCB1 expression and activity, respectively. Our study demonstrates a potential new function for FABP5 in regulating taxane sensitivity and the expression of a major P-glycoprotein efflux pump in prostate cancer cells.

The Multifunctional Family of Mammalian Fatty Acid-Binding Proteins

Fatty acid-binding proteins (FABPs) are small lipid-binding proteins abundantly expressed in tissues that are highly active in fatty acid (FA) metabolism. Ten mammalian FABPs have been identified, with tissue-specific expression patterns and highly conserved tertiary structures. FABPs were initially studied as intracellular FA transport proteins. Further investigation has demonstrated their participation in lipid metabolism, both directly and via regulation of gene expression, and in signaling within their cells of expression. There is also evidence that they may be secreted and have functional impact via the circulation. It has also been shown that the FABP ligand binding repertoire extends beyond long-chain FAs and that their functional properties also involve participation in systemic metabolism. This article reviews the present understanding of FABP functions and their apparent roles in disease, particularly metabolic and inflammation-related disorders and cancers.

The emerging role of fatty acid binding protein 5 (FABP5) in cancers

Fatty acid binding protein 5 (FABP5, or epidermal FABP) is an intracellular chaperone of fatty acid molecules that regulates lipid metabolism and cell growth. In patient-derived tumours, FABP5 expression is increased up to tenfold, often co-expressed with other cancer-related proteins. High tumoral FABP5 expression is associated with poor prognosis. FABP5 activates transcription factors (TFs) leading to increased expression of proteins involved in tumorigenesis. Genetic and pharmacological preclinical studies show that inhibiting FABP5 reduces protumoral markers, whereas elevation of FABP5 promotes tumour growth and spread. Thus, FABP5 might be a valid target for novel therapeutics. The evidence base is currently strongest for liver, prostate, breast, and brain cancers, and squamous cell carcinoma (SCC), which could represent relevant patient populations for any drug discovery programme. Teaser: This review presents the growing evidence that upregulated fatty acid binding protein 5 (FABP5) plays a role in the progression of multiple cancer types, and may represent a novel therapeutic target.

ERRα expression in ovarian cancer and promotes ovarian cancer cells migration in vitro

PURPOSE

Ovarian cancer is the leading cause of death from a gynaecological malignancy in the developed world, and is characterized by invasion and metastasis and thus causes a high fatality rate. Estrogen-related receptor alpha (ERRα) has been demonstrated to play a widespread and pathophysiological relevant role in tumourigenesis and development. The aim of this study was to investigate the effect of ERRα expression on the progression of ovarian cancer.

METHODS

The correlation between ERRα expression level and clinical pathological parameters in ovarian cancer tissues were analysed via cancer public database CPTAC. The expression level of ERRα in ovarian cancer cells were confirmed by RT-qPCR and Western blot methods. The cellular ERRα expression was up-regulated by lentivirus transfection and down-regulated by specific antagonist. The invasion and metastasis capabilities of ovarian cancer cells were characterized by wound healing assay and trans-well chamber assay.

RESULTS

The CPTAC database showed that the ERRα expression levels were higher in the late-stage and high-grade ovarian cancer tissues than in early-stage and low-grade tissues. Ovarian cancer cells with higher-expression ERRα exhibited stronger invasion and metastasis capabilities in vitro. After up-regulating the ERRα expression level, the invasion and metastasis capabilities of ovarian cancer cells were enhanced, while down-regulation weakened. Moreover, the wound sealing rate was positively correlated with the expression of ERRα mRNA expression level (r = 0.921, P < 0.01), and the cell invasiveness was also positively correlated with the cellular ERRα mRNA expression level (r = 0.926, P < 0.01).

CONCLUSIONS

Our results suggest that ERRα may promote the progression of ovarian cancer, and may serve as a promising predictive biomarker.

Fatty acid binding protein 5 regulates lipogenesis and tumor growth in lung adenocarcinoma

AIMS

Lung cancer is the leading cause of cancer-related death. Unfortunately, targeted-therapies have been unsuccessful for most patients with lung adenocarcinoma (LUAD). Thus, new early biomarkers and treatment options are a pressing need. Fatty acid binding protein 5 (FABP5) has been associated with various types of cancers. Its contribution to LUAD onset, progression and metabolic reprogramming is, however, not fully understood. In this study we assessed the importance of FABP5 in LUAD and its role in cancer lipid metabolism.

MAIN METHODS

By radioactive labeling and metabolite quantification, we studied the function of FABP5 in fatty acid metabolism using genetic/pharmacologic inhibition and overexpression models in LUAD cell lines. Flow cytometry, heterologous transplantation and bioinformatic analysis were used, in combination with other methodologies, to assess the importance of FABP5 for cellular proliferation in vitro and in vivo and in patient survival.

KEY FINDINGS

We show that high expression of FABP5 is associated with poor prognosis in patients with LUAD. FABP5 regulates lipid metabolism, diverting fatty acids towards complex lipid synthesis, whereas it does not affect their catabolism in vitro. Moreover, FABP5 is required for de novo fatty acid synthesis and regulates the expression of enzymes involved in the pathway (including FASN and SCD1). Consistently with the changes in lipid metabolism, FABP5 is required for cell cycle progression, migration and in vivo tumor growth.

SIGNIFICANCE

Our results suggest that FABP5 is a regulatory hub of lipid metabolism and tumor progression in LUAD, placing it as a new putative therapeutic target for this disease.

Estrogen-related receptor alpha in select host functions and cancer: new frontiers

Eukaryotic gene expression is under the tight control of transcription factors, which includes the estrogen-related receptor alpha (ERRα). The endogenous ligand(s) acting as ERRα agonist has not been identified and confirmed. ERRα is a prominent member of the nuclear receptors super-family with major roles in energy metabolism, including immunity, cell growth, proliferation and differentiation and a host of other functions in animals. The actions exerted by ERRα towards gene expression regulation are often in association with other transcriptional factors, receptors and signal mediators. Metabolic regulation by ERRα is known for some time that has tremendous impact on host biology like autophagy, angiogenesis, mitochondrial activity, including lipid metabolism. Cellular metabolism and cancer has intricate relationship. On account of the participation of ERRα in metabolism, it has been implicated in various types of cancer onset and progression. In a number of findings, ERRα has been demonstrated to influence several types of cancers, exhibiting as a negative prognostic marker for many. Such diverse role associated with ERRα is due to its interaction with numerous transcriptional factors and other signalling pathways that culminate in providing optimal gene regulation. These observations points to the crucial regulatory roles of ERRα in health and disease. In this article, some of the new findings on the influence of ERRα in host metabolism and biology including cancer, shall be reviewed that will provide a concise understanding of this receptor.

Fatty acid-binding proteins and fatty acid synthase influence glial reactivity and promote the formation of Müller glia-derived progenitor cells in the chick retina

A recent comparative transcriptomic study of Müller glia (MG) in vertebrate retinas revealed that fatty acid binding proteins (FABPs) are among the most highly expressed genes in chick ( Hoang et al., 2020). Here, we investigate how FABPs and fatty acid synthase (FASN) influence glial cells in the chick retina. During development, FABP7 is highly expressed by retinal progenitor cells and maturing MG, whereas FABP5 is upregulated in maturing MG. PMP2 (FABP8) is expressed by oligodendrocytes and FABP5 is expressed by non-astrocytic inner retinal glial cells, and both of these FABPs are upregulated by activated MG. In addition to suppressing the formation of Müller glia-derived progenitor cells (MGPCs), we find that FABP-inhibition suppresses the proliferation of microglia. FABP-inhibition induces distinct changes in single cell transcriptomic profiles, indicating transitions of MG from resting to reactive states and suppressed MGPC formation, with upregulation of gene modules for gliogenesis and decreases in neurogenesis. FASN-inhibition increases the proliferation of microglia and suppresses the formation of MGPCs. We conclude that fatty acid metabolism and cell signaling involving fatty acids are important in regulating the reactivity and dedifferentiation of MG, and the proliferation of microglia and MGPCs.

Lipid metabolism reprogramming in renal cell carcinoma

Metabolic reprogramming is recognized as a hallmark of cancer. Lipids are the essential biomolecules required for membrane biosynthesis, energy storage, and cell signaling. Altered lipid metabolism allows tumor cells to survive in the nutrient-deprived environment. However, lipid metabolism remodeling in renal cell carcinoma (RCC) has not received the same attention as in other cancers. RCC, the most common type of kidney cancer, is associated with almost 15,000 death in the USA annually. Being refractory to conventional chemotherapy agents and limited available targeted therapy options has made the treatment of metastatic RCC very challenging. In this article, we review recent findings that support the importance of synthesis and metabolism of cholesterol, free fatty acids (FFAs), and polyunsaturated fatty acids (PUFAs) in the carcinogenesis and biology of RCC. Delineating the detailed mechanisms underlying lipid reprogramming can help to better understand the pathophysiology of RCC and to design novel therapeutic strategies targeting this malignancy.

Targeting Mitochondrial OXPHOS and Their Regulatory Signals in Prostate Cancers

Increasing evidence suggests that tumor development requires not only oncogene/tumor suppressor mutations to drive the growth, survival, and metastasis but also metabolic adaptations to meet the increasing energy demand for rapid cellular expansion and to cope with the often nutritional and oxygen-deprived microenvironment. One well-recognized strategy is to shift the metabolic flow from oxidative phosphorylation (OXPHOS) or respiration in mitochondria to glycolysis or fermentation in cytosol, known as Warburg effects. However, not all cancer cells follow this paradigm. In the development of prostate cancer, OXPHOS actually increases as compared to normal prostate tissue. This is because normal prostate epithelial cells divert citrate in mitochondria for the TCA cycle to the cytosol for secretion into seminal fluid. The sustained level of OXPHOS in primary tumors persists in progression to an advanced stage. As such, targeting OXPHOS and mitochondrial activities in general present therapeutic opportunities. In this review, we summarize the recent findings of the key regulators of the OXPHOS pathway in prostate cancer, ranging from transcriptional regulation, metabolic regulation to genetic regulation. Moreover, we provided a comprehensive update of the current status of OXPHOS inhibitors for prostate cancer therapy. A challenge of developing OXPHOS inhibitors is to selectively target cancer mitochondria and spare normal counterparts, which is also discussed.

Oxidative stress-induced FABP5 S-glutathionylation protects against acute lung injury by suppressing inflammation in macrophages

Oxidative stress contributes to the pathogenesis of acute lung injury. Protein S-glutathionylation plays an important role in cellular antioxidant defense. Here we report that the expression of deglutathionylation enzyme Grx1 is decreased in the lungs of acute lung injury mice. The acute lung injury induced by hyperoxia or LPS is significantly relieved in Grx1 KO and Grx1^fl/flLysM^cre mice, confirming the protective role of Grx1-regulated S-glutathionylation in macrophages. Using a quantitative redox proteomics approach, we show that FABP5 is susceptible to S-glutathionylation under oxidative conditions. S-glutathionylation of Cys127 in FABP5 promotes its fatty acid binding ability and nuclear translocation. Further results indicate S-glutathionylation promotes the interaction of FABP5 and PPARβ/δ, activates PPARβ/δ target genes and suppresses the LPS-induced inflammation in macrophages. Our study reveals a molecular mechanism through which FABP5 S-glutathionylation regulates macrophage inflammation in the pathogenesis of acute lung injury.

Redox-dependent regulation plays a key role in the pathogenesis of acute lung injury, but its mechanism is unclear. Here the authors show Grx1-regulated S-glutathionylation of FABP5 controls macrophage inflammation and alleviates acute lung injury.

Tumor-intrinsic FABP5 is a novel driver for colon cancer cell growth via the HIF-1 signaling pathway

Dysfunctional lipid metabolism is a known cause of cancer development and progression, yet little is known about the underlying molecular mechanisms that contribute to cancer progression. In this study, we demonstrate that fatty acid binding protein 5 (FABP5) is elevated in colon cancer tissue and this increased expression is linked to upregulation of the hypoxia-inducible factor-1 (HIF-1) signaling pathway. Under physiologically in vivo mimicked conditions via a polydimethylsiloxane (PDMS)-based three-dimensional (3D) culture chip, FABP5-knockdown colon cancer cells exhibited attenuated cell growth throughout the culture period. FABP5 was found to regulate HIF-1α protein levels and gene expression levels within the HIF-1α signaling pathway under hypoxic conditions. Our results provide evidence that supports the use of FABP5 as a prognostic factor in colon cancer. The FABP5/HIF-1α axis is a promising target for ameliorating fatty acid-triggered cancer progression.

Molecular Profile Study of Extracellular Vesicles for the Identification of Useful Small “Hit” in Cancer Diagnosis

Tumor-secreted extracellular vesicles (EVs) are the main mediators of cell-cell communication, permitting cells to exchange proteins, lipids, and metabolites in varying physiological and pathological conditions. They contain signature tumor-derived molecules that reflect the intracellular status of their cell of origin. Recent studies have shown that tumor cell-derived EVs can aid in cancer metastasis through the modulation of the tumor microenvironment, suppression of the immune system, pre-metastatic niche formation, and subsequent metastasis. EVs can easily be isolated from a variety of biological fluids, and their content makes them useful biomarkers for the diagnosis, prognosis, monitorization of cancer progression, and response to treatment. This review aims to explore the biomarkers of cancer cell-derived EVs obtained from liquid biopsies, in order to understand cancer progression and metastatic evolution for early diagnosis and precision therapy.

Transcriptomic analysis of the mouse retina after acute and chronic normobaric and hypobaric hypoxia

Oxygen delivery to the retinal pigment epithelium and the outer retina is essential for metabolism, function, and survival of photoreceptors. Chronically reduced oxygen supply leads to retinal pathologies in patients and causes age-dependent retinal degeneration in mice. Hypoxia can result from decreased levels of inspired oxygen (normobaric hypoxia) or reduced barometric pressure (hypobaric hypoxia). Since the response of retinal cells to chronic normobaric or hypobaric hypoxia is mostly unknown, we examined the effect of six hypoxic conditions on the retinal transcriptome and photoreceptor morphology. Mice were exposed to short- and long-term normobaric hypoxia at 400 m or hypobaric hypoxia at 3450 m above sea level. Longitudinal studies over 11 weeks in normobaric hypoxia revealed four classes of genes that adapted differentially to the hypoxic condition. Seventeen genes were specifically regulated in hypobaric hypoxia and may affect the structural integrity of the retina, resulting in the shortening of photoreceptor segment length detected in various hypoxic groups. This study shows that retinal cells have the capacity to adapt to long-term hypoxia and that consequences of hypobaric hypoxia differ from those of normobaric hypoxia. Our datasets can be used as references to validate and compare retinal disease models associated with hypoxia.

Prostate Cancer Progression: as a Matter of Fats

Advanced prostate cancer (PCa) represents the fifth cause of cancer death worldwide. Although survival has improved with second-generation androgen signaling and Parp inhibitors, the benefits are not long-lasting, and new therapeutic approaches are sorely needed. Lipids and their metabolism have recently reached the spotlight with accumulating evidence for their role as promoters of PCa development, progression, and metastasis. As a result, interest in targeting enzymes/transporters involved in lipid metabolism is rapidly growing. Moreover, the use of lipogenic signatures to predict prognosis and resistance to therapy has been recently explored with promising results. Despite the well-known association between obesity with PCa lethality, the underlying mechanistic role of diet/obesity-derived metabolites has only lately been unveiled. Furthermore, the role of lipids as energy source, building blocks, and signaling molecules in cancer cells has now been revisited and expanded in the context of the tumor microenvironment (TME), which is heavily influenced by the external environment and nutrient availability. Here, we describe how lipids, their enzymes, transporters, and modulators can promote PCa development and progression, and we emphasize the role of lipids in shaping TME. In a therapeutic perspective, we describe the ongoing efforts in targeting lipogenic hubs. Finally, we highlight studies supporting dietary modulation in the adjuvant setting with the purpose of achieving greater efficacy of the standard of care and of synthetic lethality. PCa progression is "a matter of fats", and the more we understand about the role of lipids as key players in this process, the better we can develop approaches to counteract their tumor promoter activity while preserving their beneficial properties.

An Amplified Fatty Acid-Binding Protein Gene Cluster in Prostate Cancer: Emerging Roles in Lipid Metabolism and Metastasis

Treatment for early stage and localized prostate cancer (PCa) is highly effective. Patient survival, however, drops dramatically upon metastasis due to drug resistance and cancer recurrence. The molecular mechanisms underlying PCa metastasis are complex and remain unclear. It is therefore crucial to decipher the key genetic alterations and relevant molecular pathways driving PCa metastatic progression so that predictive biomarkers and precise therapeutic targets can be developed. Through PCa cohort analysis, we found that a fatty acid-binding protein (FABP) gene cluster (containing five FABP family members) is preferentially amplified and overexpressed in metastatic PCa. All five FABP genes reside on chromosome 8 at 8q21.13, a chromosomal region frequently amplified in PCa. There is emerging evidence that these FABPs promote metastasis through distinct biological actions and molecular pathways. In this review, we discuss how these FABPs may serve as drivers/promoters for PCa metastatic transformation using patient cohort analysis combined with a review of the literature.

Crystal Engineering Construction of Caffeic Acid Derivatives with Potential Applications in Pharmaceuticals and Degradable Polymeric Materials

Natural products are precious feedstock in drug discovery and sustainable materials. This work using crystal engineering strategy, visible light, and solvent-free cycloaddition successfully constructed two caffeic acid derivatives, rel-(1R,2R,3S,4S)-2,4-bis(3,4-dihydroxyphenyl)cyclobutane-1,3-dicarboxylate and rel-(1R,2R,3S,4S)-2,4-bis(3,4-dihydroxyphenyl)cyclobutane-1,3-dicarboxylic acid. Because of the multiple stereocenters, it is challenging to prepare those compounds using traditional organic synthesis methods. The crystal engineering Hirshfeld surface analysis and 2D intermolecular interaction fingerprints were applied to synthetic route design. The light resources used in this work was visible LED or free, clean, and renewable sunlight. The evidence suggested that pure stereoisomer was obtained demonstrating the stereospecificity and efficiency of the topochemical cycloaddition reaction. The derivatives exhibited free radical scavenging and antioxidant biological activities, as well as the potential inhibitory activity of fatty acid binding proteins. One of the derivatives is the precursor of the natural product Shimobashiric acid C which paves the way for the total synthesis and further study of Shimobashiric acid C. In addition, the derivatives possess photodegradability at a specific wavelength, which is very attractive for "green" degradable polymeric materials.

Fatty-acid-induced FABP5/HIF-1 reprograms lipid metabolism and enhances the proliferation of liver cancer cells

Hypoxia-inducible factor-1 alpha (HIF-1α) is a transcription factor essential for cancer cell survival. The reprogramming of lipid metabolism has emerged as a hallmark of cancer, yet the relevance of HIF-1α to this process remains elusive. In this study, we profile HIF-1α-interacting proteins using proteomics analysis and identify fatty acid-binding protein 5 (FABP5) as a critical HIF-1α-binding partner. In hepatocellular carcinoma (HCC) tissues, both FABP5 and HIF-1α are upregulated, and their expression levels are associated with poor prognosis. FABP5 enhances HIF-1α activity by promoting HIF-1α synthesis while disrupting FIH/HIF-1α interaction at the same time. Oleic-acid treatment activates the FABP5/HIF-1α axis, thereby promoting lipid accumulation and cell proliferation in HCC cells. Our results indicate that fatty-acid-induced FABP5 upregulation drives HCC progression through HIF-1-driven lipid metabolism reprogramming.

Seo et al. identify fatty acid-binding protein 5 (FABP5) as a booster of HIF-1α activity. They find that oleic-acid treatment activates the FABP5/HIF-1α axis, promoting lipid accumulation and cell proliferation in liver cancer cells. This study provides insights into how fatty acids drive the progression of cancer.

FABP5 as a novel molecular target in prostate cancer

Emerging evidence suggests that dysregulated lipid signaling is a key factor in prostate cancer (PC), through fatty acid activation of the nuclear receptors peroxisome proliferator-activated receptors (PPARs), leading to the upregulation of protumoral genes. Fatty acid-binding proteins (FABPs) are intracellular lipid-binding proteins that transport fatty acid to PPARs, facilitating their activation. FABP5 is overexpressed in PC, and correlates with poor patient prognosis and survival. Genetic knockdown or silencing of FABP5 decreases the proliferation and invasiveness of PC cells in vitro, and reduces tumor growth and metastasis in vivo. Pharmacological FABP5-specific inhibitors also reduce tumor growth and metastases, and produce synergistic effects with taxanes. In this review, we present current data supporting FABP5 as a novel molecular target for PC.

Expression of fatty-acid-binding protein 5 in intrahepatic and extrahepatic cholangiocarcinoma: the possibility of different energy metabolisms in anatomical location

The biliary tract cancer (BTC) covers a range of carcinomas, including intrahepatic cholangiocarcinoma (ICC), cholangiolocellular carcinoma (CoCC), perihilar cholangiocarcinoma (perihilar CC), extrahepatic cholangiocarcinoma (ECC), and gallbladder cancer (GBC), defined according to the anatomical location. These adenocarcinomas mostly comprise biliary epithelial cell-derived malignant cells. In addition to anatomical differences, there are morphological and biological differences in BTC starting from embryonic development of the tissues extending to physiological differences. Fatty acid-binding proteins (FABPs) are closely associated with the energy metabolism. Using surgical specimens from 74 BTCs, we performed immunohistochemistry for FABP5 and its associated molecules, including peroxisome proliferator-activated receptor γ (PPARγ), PPARγ coactivator 1 (PGC-1), and estrogen-related receptor α (ERRα). We found that the expression patterns of small BTCs (ICC and CoCC) considerably differed from those of large BTCs (perihilar CC, ECC, and GBC). Expression of FABP5 and PGC-1 in large BTCs was high compared with those of small BTCs, but no difference in the expression of PPARγ and ERRα was observed. FABP5 appears to play a role in malignant progression in large BTCs. Small and large BTCs possess different energy metabolism systems owing to their different anatomical locations and course of carcinogenesis, although all BTCs originate from biliary epithelial cells.

FABP5 coordinates lipid signaling that promotes prostate cancer metastasis

Prostate cancer (PCa) is defined by dysregulated lipid signaling and is characterized by upregulation of lipid metabolism-related genes including fatty acid binding protein 5 (FABP5), fatty acid synthase (FASN), and monoacylglycerol lipase (MAGL). FASN and MAGL are enzymes that generate cellular fatty acid pools while FABP5 is an intracellular chaperone that delivers fatty acids to nuclear receptors to enhance PCa metastasis. Since FABP5, FASN, and MAGL have been independently implicated in PCa progression, we hypothesized that FABP5 represents a central mechanism linking cytosolic lipid metabolism to pro-metastatic nuclear receptor signaling. Here, we show that the abilities of FASN and MAGL to promote nuclear receptor activation and PCa metastasis are critically dependent upon co-expression of FABP5 in vitro and in vivo. Our findings position FABP5 as a key driver of lipid-mediated metastasis and suggest that disruption of lipid signaling via FABP5 inhibition may constitute a new avenue to treat metastatic PCa.

Fatty acids - from energy substrates to key regulators of cell survival, proliferation and effector function

Recent advances in immunology and cancer research show that fatty acids, their metabolism and their sensing have a crucial role in the biology of many different cell types. Indeed, they are able to affect cellular behaviour with great implications for pathophysiology. Both the catabolic and anabolic pathways of fatty acids present us with a number of enzymes, receptors and agonists/antagonists that are potential therapeutic targets, some of which have already been successfully pursued. Fatty acids can affect the differentiation of immune cells, particularly T cells, as well as their activation and function, with important consequences for the balance between anti- and pro-inflammatory signals in immune diseases, such as rheumatoid arthritis, psoriasis, diabetes, obesity and cardiovascular conditions. In the context of cancer biology, fatty acids mainly provide substrates for energy production, which is of crucial importance to meet the energy demands of these highly proliferating cells. Fatty acids can also be involved in a broader transcriptional programme as they trigger signals necessary for tumorigenesis and can confer to cancer cells the ability to migrate and generate distant metastasis. For these reasons, the study of fatty acids represents a new research direction that can generate detailed insight and provide novel tools for the understanding of immune and cancer cell biology, and, more importantly, support the development of novel, efficient and fine-tuned clinical interventions. Here, we review the recent literature focusing on the involvement of fatty acids in the biology of immune cells, with emphasis on T cells, and cancer cells, from sensing and binding, to metabolism and downstream effects in cell signalling.

Fatty acid-binding proteins: functional understanding and diagnostic implications

PURPOSE OF REVIEW

Fatty acid-binding proteins (FABPs) are a family of small, abundant proteins with highly tissue-specific expression patterns whose different functions remain incompletely understood. The purpose of this review is to summarize recent findings regarding FABP functions and mechanisms of action, including their potential utilization as serum markers of tissue-specific metabolic diseases.

RECENT FINDINGS

FABPs are important not only in their tissues of origin but also appear to influence the metabolism and function of tissues distal to their sites of expression. This may be secondary to metabolic changes in their primary tissues, and/or a result of FABP secretion from these tissues leading to effects on distal sites. Their levels in the circulation are increasingly explored as potential biomarkers for tissue-specific disease prognosis and progression.

SUMMARY

The nine fatty acid-binding members of the FABP family have unique tissue-specific functions and important secondary effects on tissues in which they are not expressed. For many of the FABPs, circulating levels may be indicative of disease processes related to their primary tissues, and may influence physiological function in distal tissues.

Exposure to an environmentally relevant phthalate mixture during prostate development induces microRNA upregulation and transcriptome modulation in rats

Environmental exposure to phthalates during intrauterine development might increase susceptibility to neoplasms in reproductive organs such as the prostate. Although studies have suggested an increase in prostatic lesions in adult animals submitted to perinatal exposure to phthalates, the molecular pathways underlying these alterations remain unclear. Genome-wide levels of mRNAs and miRNAs were monitored with RNA-seq to determine if perinatal exposure to a phthalate mixture in pregnant rats is capable of modifying gene expression expression during prostate development of the filial generation. The mixture contains diethyl-phthalate, di-(2-ethylhexyl)-phthalate, dibutyl-phthalate, di-isononyl-phthalate, di-isobutyl-phthalate, and benzylbutyl-phthalate. Pregnant females were divided into 4 groups and orally dosed daily from GD10 to PND21 with corn oil (Control:C) or the phthalate mixture at three doses (20 μg/kg/d:T1; 200 μg/kg/d:T2; 200 mg/kg/d:T3). The phthalate mixture decreased anogenital distance, prostate weight and decreased testosterone level at the lowest exposure dose at PND22. The mixture also increased inflammatory foci and focal hyperplasia incidence at PND120. miR-184 was upregulated in all treated groups in relation to control and miR-141-3p was only upregulated at the lowest dose. In addition, 120 genes were deregulated at the lowest dose with several of these genes related to developmental, differentiation and oncogenesis. The data indicate that phthalate exposure at lower doses can cause greater gene expression modulation as well as other downstream phenotypes than exposure at higher doses. A significant fraction of the downregulated genes were predicted to be targets of miR-141-3p and miR-184, both of which were induced at the lower exposure doses.

Fatty Acid Signaling Mechanisms in Neural Cells: Fatty Acid Receptors

Fatty acids (FAs) are typically associated with structural and metabolic roles, as they can be stored as triglycerides, degraded by β-oxidation or used in phospholipids’ synthesis, the main components of biological membranes. It has been shown that these lipids exhibit also regulatory functions in different cell types. FAs can serve as secondary messengers, as well as modulators of enzymatic activities and substrates for cytokines synthesis. More recently, it has been documented a direct activity of free FAs as ligands of membrane, cytosolic, and nuclear receptors, and cumulative evidence has emerged, demonstrating its participation in a wide range of physiological and pathological conditions. It has been long known that the central nervous system is enriched with poly-unsaturated FAs, such as arachidonic (C20:4ω-6) or docosohexaenoic (C22:6ω-3) acids. These lipids participate in the regulation of membrane fluidity, axonal growth, development, memory, and inflammatory response. Furthermore, a whole family of low molecular weight compounds derived from FAs has also gained special attention as the natural ligands for cannabinoid receptors or key cytokines involved in inflammation, largely expanding the role of FAs as precursors of signaling molecules. Nutritional deficiencies, and alterations in lipid metabolism and lipid signaling have been associated with developmental and cognitive problems, as well as with neurodegenerative diseases. The molecular mechanism behind these effects still remains elusive. But in the last two decades, different families of proteins have been characterized as receptors mediating FAs signaling. This review focuses on different receptors sensing and transducing free FAs signals in neural cells: (1) membrane receptors of the family of G Protein Coupled Receptors known as Free Fatty Acid Receptors (FFARs); (2) cytosolic transport Fatty Acid-Binding Proteins (FABPs); and (3) transcription factors Peroxisome Proliferator-Activated Receptors (PPARs). We discuss how these proteins modulate and mediate direct regulatory functions of free FAs in neural cells. Finally, we briefly discuss the advantages of evaluating them as potential targets for drug design in order to manipulate lipid signaling. A thorough characterization of lipid receptors of the nervous system could provide a framework for a better understanding of their roles in neurophysiology and, potentially, help for the development of novel drugs against aging and neurodegenerative processes.