Antiangiogenic and tumour inhibitory effects of downregulating tumour endothelial FABP4

Bone Marrow Adipose Tissue

Bone marrow (BM) acts as a dynamic organ within the bone cavity, responsible for hematopoiesis, skeletal remodeling, and immune system control. Bone marrow adipose tissue (BMAT) was long simply considered a filler of space, but now it is known that it instead constitutes an essential element of the BM microenvironment that participates in homeostasis, influences bone health and bone remodeling, alters hematopoietic stem cell functions, contributes to the commitment of mesenchymal stem cells, provides effects to immune homeostasis and defense against infections, and participates in energy metabolism and inflammation. BMAT has emerged as a significant contributor to the development and progression of various diseases, shedding light on its complex relationship with health. Notably, BMAT has been implicated in metabolic disorders, hematological malignancies, and skeletal conditions. BMAT has been shown to support the proliferation of tumor cells in acute myeloid leukemia and niche adipocytes have been found to protect cancer cells against chemotherapy, contributing to treatment resistance. Moreover, BMAT's impact on bone density and remodeling can lead to conditions like osteoporosis, where high levels of BMAT are inversely correlated with bone mineral density, increasing the risk of fractures. BMAT has also been associated with diabetes, obesity, and anorexia nervosa, with varying effects on individuals depending on their weight and health status. Understanding the interaction between adipocytes and different diseases may lead to new therapeutic strategies.

The Notch signaling-regulated angiogenesis in rheumatoid arthritis: pathogenic mechanisms and therapeutic potentials

Angiogenesis plays a key role in the pathological process of inflammation and invasion of the synovium, and primarily drives the progression of rheumatoid arthritis (RA). Recent studies have demonstrated that the Notch signaling may represent a new therapeutic target of RA. Although the Notch signaling has been implicated in the M1 polarization of macrophages and the differentiation of lymphocytes, little is known about its role in angiogenesis in RA. In this review, we discourse the unique roles of stromal cells and adipokines in the angiogenic progression of RA, and investigate how epigenetic regulation of the Notch signaling influences angiogenesis in RA. We also discuss the interaction of the Notch-HIF signaling in RA's angiogenesis and the potential strategies targeting the Notch signaling to improve the treatment outcomes of RA. Taken together, we further suggest new insights into future research regarding the challenges in the therapeutic strategies of RA.

Omentum provides a special cell microenvironment for ovarian cancer

BACKGROUND

Ovarian cancer seriously threatens women's health because of its poor prognosis and high mortality. Due to the lack of efficient early detection and screening methods, when patients seek doctors' help with complaints of abdominal distension, back pain and other nonspecific signs, the clinical results always hint at the widespread metastasis of disease. When referring to the metastasis of this disease, the omentum always takes precedence.

RECENT FINDINGS

The distinguishing feature of the omentum is adipose tissue, which satisfies the energy demand of cancer cells and supplies a more aggressive environment for ovarian cancer cells. In this review, we mainly focus on three important cell types: adipocytes, macrophages, and mesenchymal stem cells. Besides, several mechanisms underlying cancer-associated adipocytes (CAA)-facilitated ovarian cancer cell development have been revealed, including their capacities for storing lipids and endocrine function, and the release of hormones, growth factors, and adipokines. Blocking the reciprocity among cancer cells and various cells located on the omentum might contribute to ovarian cancer therapy. The inhibition of hormones, growth factors and adipokines produced by adipocytes will be a novel therapeutic strategy. However, a sufficient number of trials has not been performed. In spite of this, the therapeutic potential of metformin and the roles of exercise in ovarian cancer will be worth mentioning.

CONCLUSION

It is almost impossible to overcome completely ovarian cancer at the moment. What we can do is trying our best to improve these patients' prognoses. In this process, adipocytes may bring promising future for the therapy of ovarian cancer.

Role of bone marrow adipocytes in bone metastasis development and progression: a systematic review

Purpose

Bone marrow adipocytes (BMAs) are the most plentiful cells in the bone marrow and function as an endocrine organ by producing fatty acids, cytokines, and adipokines. Consequently, BMAs can interact with tumor cells, influencing both tumor growth and the onset and progression of bone metastasis. This review aims to systematically evaluate the role of BMAs in the development and progression of bone metastasis.

Methods

A comprehensive search was conducted on PubMed, Web of Science, and Scopus electronic databases, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement standards, to identify studies published from March 2013 to June 2023. Two independent reviewers assessed and screened the literature, extracted the data, and evaluated the quality of the studies. The body of evidence was evaluated and graded using the ROBINS-I tool for non-randomized studies of interventions and the Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE) tool for in vivo studies. The results were synthesized using descriptive methods.

Results

The search yielded a total of 463 studies, of which 17 studies were included in the final analysis, including 15 preclinical studies and two non-randomized clinical studies. Analysis of preclinical studies revealed that BMAs play a significant role in bone metastasis, particularly in prostate cancer followed by breast and malignant melanoma cancers. BMAs primarily influence cancer cells by inducing a glycolytic phenotype and releasing or upregulating soluble factors, chemokines, cytokines, adipokines, tumor-derived fatty acid-binding protein (FABP), and members of the nuclear receptor superfamily, such as chemokine (C-C motif) ligand 7 (CCL7), C-X-C Motif Chemokine Ligand (CXCL)1, CXCL2, interleukin (IL)-1β, IL-6, FABP4, and peroxisome proliferator-activated receptor γ (PPARγ). These factors also contribute to adipocyte lipolysis and regulate a pro-inflammatory phenotype in BMAs. However, the number of clinical studies is limited, and definitive conclusions cannot be drawn.

Conclusion

The preclinical studies reviewed indicate that BMAs may play a crucial role in bone metastasis in prostate, breast, and malignant melanoma cancers. Nevertheless, further preclinical and clinical studies are needed to better understand the complex role and relationship between BMAs and cancer cells in the bone microenvironment. Targeting BMAs in combination with standard treatments holds promise as a potential therapeutic strategy for bone metastasis.

Endothelial-derived FABP4 constitutes the majority of basal circulating hormone and regulates lipolysis-driven insulin secretion

Fatty acid binding protein 4 (FABP4) is a lipid chaperone secreted from adipocytes upon stimulation of lipolysis. Circulating FABP4 levels strongly correlate with obesity and metabolic pathologies in experimental models and humans. While adipocytes have been presumed to be the major source of hormonal FABP4, this question has not been addressed definitively in vivo. We generated mice with Fabp4 deletion in cells known to express the gene - adipocytes (Adipo-KO), endothelial cells (Endo-KO), myeloid cells (Myeloid-KO), and the whole body (Total-KO) - to examine the contribution of these cell types to basal and stimulated plasma FABP4 levels. Unexpectedly, baseline plasma FABP4 was not significantly reduced in Adipo-KO mice, whereas Endo-KO mice showed ~87% reduction versus WT controls. In contrast, Adipo-KO mice exhibited ~62% decreased induction of FABP4 responses to lipolysis, while Endo-KO mice showed only mildly decreased induction, indicating that adipocytes are the main source of increases in FABP4 during lipolysis. We did not detect any myeloid contribution to circulating FABP4. Surprisingly, despite the nearly intact induction of FABP4, Endo-KO mice showed blunted lipolysis-induced insulin secretion, identical to Total-KO mice. We conclude that the endothelium is the major source of baseline hormonal FABP4 and is required for the insulin response to lipolysis.

Scutellarin, a promising flavonoid in cancer treatment

Natural substances are increasingly being used as cancer treatments. Scutellarin, as a flavonoid, recently has been identified in a Chinese herbal extract called Erigeron breviscapus (Vant.). Scutellarin is being researched for its potential benefits due to the discovery that it possesses a variety of biological effects, such as neuroprotective, anti-coagulant, and anti-viral. In addition to these biological functions, scutellarin has also been found to have anti-tumor properties. Scutellarin first inhibits the activity of tumor cells by altering cancer cell signaling pathways such as Jak/STAT, ERK/AMPK, and Wnt/β-catenin. Additionally, scutellarin activates intrinsic and extrinsic apoptotic pathways, which causes the death of tumor cells, interrupts the cell cycle, and promotes its arrest. By limiting metastasis, angiogenesis, drug resistance, and other tumorigenic processes, scutellarin also reduces the aggressiveness of tumors. Utilizing scutellarin in combination with other anti-tumor therapies like 5-fluorouracil is another method to overcome tumor cell resistance. Moreover, it has been suggested that certain modifications, such as conjugation with cyclodextrin, aliphatic chains, and hybridization with nitric oxide, can enhance the pharmacogenetic capabilities of scutellarin to decrease its limited water solubility. It is believed that scutellarin may provide innovative chemotherapeutic treatments for cancer in the future.

Comprehensive analysis of the immune implication of FABP4 in colon adenocarcinoma

Background

Fatty acid-binding protein 4 (FABP4) has been reported to be associated with tumor progress and poor prognosis in various cancers. However, the relationship between FABP4 expression and tumor immunity in colon adenocarcinoma (COAD) is still poorly understood.

Methods

FABP4 mRNA expression was analyzed using The Cancer Genome Atlas (TCGA)-COAD data. FABP4 protein staining was performed by immunohistochemistry (IHC) staining in our 10 paired COAD samples and corresponding adjacent noncancerous tissues. The association between FABP4 and immune cell infiltration was evaluated by Tumor Immune Estimation Resource (TIMER) database. FABP4 coexpressed genes were identified based on Cancer Cell Line Encyclopedia (CCLE) database, which were employed for further enrichment analysis. FABP4 related immunomodulators was identified by Tumor and Immune System Interaction Database (TISIDB) database, and a prognostic risk signature was constructed based on FABP4-related immunomodulators using stepwise Cox regression analysis. A nomogram consists of FABP4 related immunomodulators signature and clinical parameters was developed to predict the overall survival (OS).

Results

In TCGA data, we found that the decreased FABP4 mRNA expression in COAD samples compared with normal samples, and low FABP4 mRNA expression was associated with B cells, CD4+ T cells, CD8+ T cells, myeloid dendritic cells, macrophages, and neutrophils. In our 10 paired samples, the protein levels of COAD were lower in all COAD tissues than in their adjacent noncancerous tissues. Functional enrichment analysis revealed that FABP4 coexpressed genes were mostly enriched in immune-related pathways. Based on 54 FABP4-related immunomodulators, a 2-gene FABP4-related prognostic risk signature was developed, and the signature stratified the patients into the high-risk and low-risk groups with statistically different survival outcomes. The Nomogram consists of the prognostic signature and clinical parameters had a certain predictability for prognosis of COAD patients.

Conclusion

These findings suggest that FABP4 is associated with 2-gene immune signature which also correlate with the prognosis of COAD patients.

Bioinformatics analysis reveals the potential target of rosiglitazone as an antiangiogenic agent for breast cancer therapy

Background

Several studies have demonstrated the antitumor activity of rosiglitazone (RGZ) in cancer cells, including breast cancer cells. However, the molecular targets of RGZ in the inhibition of angiogenesis in breast cancer cells remain unclear. This study aimed to explore the potential targets of RGZ in inhibiting breast cancer angiogenesis using bioinformatics-based analysis.

Results

Venn diagram analysis revealed 29 TR proteins. KEGG pathway enrichment analysis demonstrated that TR regulated the adipocytokine, AMPK, and PPAR signaling pathways. Oncoprint analysis showed genetic alterations in FABP4 (14%), ADIPOQ (2.9%), PPARG (2.8%), PPARGC1A (1.5%), CD36 (1.7%), and CREBBP (11%) in patients with breast cancer in a TCGA study. The mRNA levels of FABP4, ADIPOQ, PPARG, CD36, and PPARGC1A were significantly lower in patients with breast cancer than in those without breast cancer. Analysis of gene expression using bc-GenExMiner showed that the mRNA levels of FABP, ADIPOQ, PPARG, CD36, PPARGC1A, and CREBBP were significantly lower in basal-like and triple-negative breast cancer (TNBC) cells than in non-basal-like and non-TNBC cells. In general, the protein levels of these genes were low, except for that of CREBBP. Patients with breast cancer who had low mRNA levels of FABP4, ADIPOQ, PPARG, and PPARGC1A had lower overall survival rates than those with high mRNA levels, which was supported by the overall survival related to DNA methylation. Correlation analysis of immune cell infiltration with TR showed a correlation between TR and immune cell infiltration, highlighting the potential of RGZ for immunotherapy.

Conclusion

This study explored the potential targets of RGZ as antiangiogenic agents in breast cancer therapy and highlighted FABP4, ADIPOQ, PPARG, PPARGC1A, CD36, and CREBBP as potential targets of RGZ. These findings require further validation to explore the potential of RGZ as an antiangiogenic agent.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12863-022-01086-2.

Recent studies have focused on the development of indirect angiogenesis inhibitors.

Bioinformatics-based identification of potential rosiglitazone target genes to inhibit breast cancer angiogenesis.

FABP4, ADIPOQ, PPARG, PPARGC1A, CD36, and CREBBP are potential targets of rosiglitazone.

FABP4 secreted by M1-polarized macrophages promotes synovitis and angiogenesis to exacerbate rheumatoid arthritis

Increasing evidence shows that adipokines play a vital role in the development of rheumatoid arthritis (RA). Fatty acid-binding protein 4 (FABP4), a novel adipokine that regulates inflammation and angiogenesis, has been extensively studied in a variety of organs and diseases. However, the effect of FABP4 on RA remains unclear. Here, we found that FABP4 expression was upregulated in synovial M1-polarized macrophages in RA. The increase in FABP4 promoted synovitis, angiogenesis, and cartilage degradation to exacerbate RA progression in vivo and in vitro, whereas BMS309403 (a FABP4 inhibitor) and anagliptin (dipeptidyl peptidase 4 inhibitor) inhibited FABP4 expression in serum and synovial M1-polarized macrophages in mice to alleviate RA progression. Further studies showed that constitutive activation of mammalian target of rapamycin complex 1 (mTORC1) by TSC1 deletion specifically in the myeloid lineage regulated FABP4 expression in macrophages to exacerbate RA progression in mice. In contrast, inhibition of mTORC1 by ras homolog enriched in brain (Rheb1) disruption specifically in the myeloid lineage reduced FABP4 expression in macrophages to attenuate RA development in mice. Our findings established an essential role of FABP4 that is secreted by M1-polarized macrophages in synovitis, angiogenesis, and cartilage degradation in RA. BMS309403 and anagliptin inhibited FABP4 expression in synovial M1-polarized macrophages to alleviate RA development. Hence, FABP4 may represent a potential target for RA therapy.

Fatty acid binding protein 4 regulates pancreatic cancer cell proliferation via activation of nuclear factor E2-related factor 2

BACKGROUND

Obesity and diabetes are associated with an increased incidence of pancreatic cancer. Fatty acid binding protein 4 (FABP4), noted to be higher in patients with severe obesity, is linked to the development and progression of several cancers, and its level in the circulation decreases after bariatric surgery.

OBJECTIVE

In this paper, we evaluate the role of FABP4 in pancreatic cancer progression.

SETTING

University Hospital and Laboratories, United States.

METHODS AND RESULTS

When Panc-1 (human) and Pan02 (mouse) pancreatic cancer cells were treated with FABP4 or the-single-point mutant FABP4 (R126Q, fatty acid binding site mutant), only FABP4 stimulated cellular proliferation. The transcriptional activity of nuclear factor E2-related factor 2 (NRF2) was increased in response to FABP4 but not the R126Q. FABP4 treatment also led to downregulation of reactive oxygen species (ROS) activity. Consistent with induced cell propagation by FABP4, the growth of Pan02 tumor was decreased in FABP4-null animals compared with C57BL/6J controls.

CONCLUSION

These results suggest that FABP4 increases pancreatic cancer proliferation via activation of NRF2 and downregulation of ROS activity.

Exploring the clinical value of tumor microenvironment in platinum-resistant ovarian cancer

Platinum resistance in epithelial ovarian cancer (OvCa) is rising at an alarming rate, with recurrence of chemo-resistant high grade serous OvCa (HGSC) in roughly 75 % of all patients. Additionally, HGSC has an abysmal five-year survival rate, standing at 39 % and 17 % for FIGO stages III and IV, respectively. Herein we review the crucial cellular interactions between HGSC cells and the cellular and non-cellular components of the unique peritoneal tumor microenvironment (TME). We highlight the role of the extracellular matrix (ECM), ascitic fluid as well as the mesothelial cells, tumor associated macrophages, neutrophils, adipocytes and fibroblasts in platinum-resistance. Moreover, we underscore the importance of other immune-cell players in conferring resistance, including natural killer cells, myeloid-derived suppressive cells (MDSCs) and T-regulatory cells. We show the clinical relevance of the key platinum-resistant markers and their correlation with the major pathways perturbed in OvCa. In parallel, we discuss the effect of immunotherapies in re-sensitizing platinum-resistant patients to platinum-based drugs. Through detailed analysis of platinum-resistance in HGSC, we hope to advance the development of more effective therapy options for this aggressive disease.

Inhibition of FABP6 Reduces Tumor Cell Invasion and Angiogenesis through the Decrease in MMP-2 and VEGF in Human Glioblastoma Cells

Malignant glioma is one of the most lethal cancers with rapid progression, high recurrence, and poor prognosis in the central nervous system. Fatty acid-binding protein 6 (FABP6) is a bile acid carrier protein that is overexpressed in colorectal cancer. This study aimed to assess the involvement of FABP6 expression in the progression of malignant glioma. Immunohistochemical analysis revealed that FABP6 expression was higher in glioma than in normal brain tissue. After the knockdown of FABP6, a decrease in the migration and invasion abilities of glioma cells was observed. The phosphorylation of the myosin light chain was inhibited, which may be associated with migration ability. Moreover, expression levels of invasion-related proteins, matrix metalloproteinase-2 (MMP-2) and cathepsin B, were reduced. Furthermore, tube formation was inhibited in the human umbilical vein endothelial cells with a decreased concentration of vascular endothelial growth factor (VEGF) in the conditioned medium after the knockdown of FABP6. The phosphorylation of the extracellular signal-regulated kinase (ERK), c-Jun NH2-terminal kinase (JNK), and p65 were also decreased after FABP6 reduction. Finally, the bioluminescent images and immunostaining of MMP-2, cluster of differentiation 31 (CD31), and the VEGF receptor 1 (VEGFR1) revealed attenuated tumor progression in the combination of the FABP6-knocked-down and temozolomide (TMZ)-treated group in an orthotopic xenograft mouse tumor model. This is the first study that revealed the impact of FABP6 on the invasion, angiogenesis, and progression of glioma. The results of this study show that FABP6 may be a potential therapeutic target combined with TMZ for malignant gliomas.

Metabolic Hormones Modulate Macrophage Inflammatory Responses

Simple Summary

Macrophages are a type of immune cell which play an important role in the development of cancer. Obesity increases the risk of cancer and obesity also causes disruption to the normal levels of hormones that are produced to coordinate metabolism. Recent research now shows that these metabolic hormones also play important roles in macrophage immune responses and so through macrophages, disrupted metabolic hormone levels may promote cancer. This review article aims to highlight and summarise these recent findings so that the scientific community may better understand how important this new area of research is, and how these findings can be capitalised on for future scientific studies.

Abstract

Macrophages are phagocytotic leukocytes that play an important role in the innate immune response and have established roles in metabolic diseases and cancer progression. Increased adiposity in obese individuals leads to dysregulation of many hormones including those whose functions are to coordinate metabolism. Recent evidence suggests additional roles of these metabolic hormones in modulating macrophage inflammatory responses. In this review, we highlight key metabolic hormones and summarise their influence on the inflammatory response of macrophages and consider how, in turn, these hormones may influence the development of different cancer types through the modulation of macrophage functions.

Molecular processes mediating hyperhomocysteinemia-induced metabolic reprogramming, redox regulation and growth inhibition in endothelial cells

Hyperhomocysteinemia (HHcy) is an established and potent independent risk factor for degenerative diseases, including cardiovascular disease (CVD), Alzheimer disease, type II diabetes mellitus, and chronic kidney disease. HHcy has been shown to inhibit proliferation and promote inflammatory responses in endothelial cells (EC), and impair endothelial function, a hallmark for vascular injury. However, metabolic processes and molecular mechanisms mediating HHcy-induced endothelial injury remains to be elucidated. This study examined the effects of HHcy on the expression of microRNA (miRNA) and mRNA in human aortic EC treated with a pathophysiologically relevant concentration of homocysteine (Hcy 500 μM). We performed a set of extensive bioinformatics analyses to identify HHcy-altered metabolic and molecular processes. The global functional implications and molecular network were determined by Gene Set Enrichment Analysis (GSEA) followed by Cytoscape analysis. We identified 244 significantly differentially expressed (SDE) mRNA, their relevant functional pathways, and 45 SDE miRNA. HHcy-altered SDE inversely correlated miRNA-mRNA pairs (45 induced/14 reduced mRNA) were discovered and applied to network construction using an experimentally verified database. We established a hypothetical model to describe the biochemical and molecular network with these specified miRNA/mRNA axes, finding: 1) HHcy causes metabolic reprogramming by increasing glucose uptake and oxidation, by glycogen debranching and NAD⁺/CoA synthesis, and by stimulating mitochondrial reactive oxygen species production via NNT/IDH2 suppression-induced NAD⁺/NADP-NADPH/NADP⁺ metabolism disruption; 2) HHcy activates inflammatory responses by activating inflammasome-pyroptosis mainly through ↓miR193b→↑CASP-9 signaling and by inducing IL-1β and adhesion molecules through the ↓miR29c→↑NEDD9 and the ↓miR1256→↑ICAM-1 axes, as well as GPCR and interferon α/β signaling; 3) HHcy promotes cell degradation by the activation of lysosome autophagy and ubiquitin proteasome systems; 4) HHcy causes cell cycle arrest at G1/S and S/G2 transitions, suppresses spindle checkpoint complex and cytokinetic abscission, and suppresses proliferation through ↓miRNA335/↑VASH1 and other axes. These findings are in accordance with our previous studies and add a wealth of heretofore-unexplored molecular and metabolic mechanisms underlying HHcy-induced endothelial injury. This is the first study to consider the effects of HHcy on both global mRNA and miRNA expression changes for mechanism identification. Molecular axes and biochemical processes identified in this study are useful not only for the understanding of mechanisms underlying HHcy-induced endothelial injury, but also for discovering therapeutic targets for CVD in general.

•

Identified multiple HHcy-altered metabolic and molecular processes potentially responsible for HHcy-induced endothelial injury via examining global mRNA/miRNA expression changes in Hcy-treated EC and performing comprehensive bioinformatic studies.

•

HHcy may activate glucose uptake signaling via the ↓miR148b→↑SLC2A axis.

•

HHcy may induce glucose oxidation signaling by switching pyruvate metabolism from lactate synthesis to mitochondrial oxidation via expression changes of ↑MPC1 & ↓LDHB.

•

HHcy may disrupt redox homeostasis mostly by suppressing NNT/IDH2-related mt-NADPH/mt-NAD⁺ signaling.

•

HHcy may increase FA β-oxidation, glutamine, TCA cycle and OXPHOS signaling.

•

HHcy may activate inflammatory signaling via the ↓miR29c→↑NEDD9 and the ↓miR1256→↑ICAM-1 axes.

•

HHcy may activate inflammasome/pyroptosis-related signaling by the ↓miR137→↑TLR3, the ↓miR574→↑TRAF5, and the ↓miR193b→↑CASP-9 axes, and induce IL1α/β and CASP-10/7.

•

HHcy may induce inflammation signaling via GPCR activation through the ↓miRNA335→↑CXCR4/↑GNA14 axes.

•

HHcy may activate molecular degradation process signaling through the ↓miRNA335→↑ASAH1/↑ABCB9 axes.

•

HHcy may suppress cell cycle and proliferation through the miR491→↓HMGA2→↓CCNA2/CCNB2, the ↓miR335→↑VASH1, the ↓miR181a→↑PHLDA1, the miR6045→↓CENPH, the miR22→↓PRR11/↓BRCA2, and the miR605/miR497/miR514a→CEP55 axes

FABP4 deactivates NF-κB-IL1α pathway by ubiquitinating ATPB in tumor-associated macrophages and promotes neuroblastoma progression

Neuroblastoma (NB) is the most common and deadliest pediatric solid tumor. Targeting and reactivating tumor-associated macrophages (TAMs) is necessary for reversing immune suppressive state and stimulating immune defense to exert tumoricidal function. However, studies on the function and regulation of TAMs in NB progression are still limited. Fatty acid binding protein 4 (FABP4) in TAMs was correlated with advanced clinical stages and unfavorable histology of NB. FABP4-mediated macrophages increased migration, invasion, and tumor growth of NB cells. Mechanically, FABP4 could directly bind to ATPB to accelerate ATPB ubiquitination in macrophages. The consequently decreased ATP levels could deactivate NF-κB/RelA-IL1α pathway, which subsequently results in macrophages reprogrammed to an anti-inflammatory phenotype. We also demonstrated that FABP4-enhanced migration and invasion were significantly suppressed by IL1α blocking antibody. Furthermore, circulating FABP4 was also associated with the clinical stages of NB. Our findings suggest that FABP4-mediated macrophages may promote proliferation and migration phenotypes in NB cells through deactivating NF-κB-IL1α pathway by ubiquitinating ATPB. This study reveals the pathologic and biologic role of FABP4-mediated macrophages in NB development and exhibits a novel application of targeting FABP4 in macrophages for NB treatment.

Endothelial Cell Glucose Metabolism and Angiogenesis

Angiogenesis, a process of new blood vessel formation from the pre-existing vascular bed, is a critical event in various physiological and pathological settings. Over the last few years, the role of endothelial cell (EC) metabolism in angiogenesis has received considerable attention. Accumulating studies suggest that ECs rely on aerobic glycolysis, rather than the oxidative phosphorylation pathway, to produce ATP during angiogenesis. To date, numerous critical regulators of glucose metabolism, fatty acid oxidation, and glutamine metabolism have been identified to modulate the EC angiogenic switch and pathological angiogenesis. The unique glycolytic feature of ECs is critical for cell proliferation, migration, and responses to environmental changes. In this review, we provide an overview of recent EC glucose metabolism studies, particularly glycolysis, in quiescent and angiogenic ECs. We also summarize and discuss potential therapeutic strategies that take advantage of EC metabolism. The elucidation of metabolic regulation and the precise underlying mechanisms could facilitate drug development targeting EC metabolism to treat angiogenesis-related diseases.

Functional inhibition of fatty acid binding protein 4 ameliorates impaired ciliogenesis in GCs

Ciliogenesis is often impaired in some cancer cells, leading to acceleration of cancer phenotypes such as cell migration and proliferation. From the investigation of primary cilia of 16 gastric cancer cells (GCs), we found that GCs could be grouped into four primary cilia (PC)-positive GCs and 12 PC-negative GCs. The proliferation of the PC-positive GCs was lower than that of PC-negative GCs. To explore the role of fatty acid binding protein 4 (FABP4), which is a known oncogenic factor, in ciliogenesis, FABP4 expression and function were inhibited by transfection of cells with short interfering RNA targeting FABP4 (siFABP4) or FABP4 inhibitor treatment. Notably, the proliferation and migration of the cilia-forming GCs was effectively suppressed by inhibition of FABP4. In addition, the primary cilia in GCs were restored by a factor greater than two, suggesting a negative role of FABP4 in ciliogenesis in these GCs and FABP4 as a potential anticancer target.

Thermal Shift Assay for Exploring Interactions Between Fatty Acid-Binding Protein and Inhibitors

Thermal shift assay (TSA) is a widely used method in discovering potential compounds (e.g., ligands, inhibitors, and other additives) to the target protein for structural genomics and drug screening in both academia and industry. The presence of sensitive fluorescent dye enables to monitor thermal stability of protein and compounds affecting this stability. By using a conventional real-time PCR instrument, it is determined as a low-cost and high efficacy experiment applied to identify optimal conditions for ligand binds to protein. Fatty acid-binding proteins (FABPs) are small molecular proteins in transporting fatty acids and other lipophilic substances in physiological and pathological responses. This chapter presents a comprehensive workflow to monitor recombinant FABP-compound interactions for an initial screening for inhibitors using TSA with SYPRO Orange dye.

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.

Obesity-Related Fatty Acid and Cholesterol Metabolism in Cancer-Associated Host Cells

Obesity-derived disturbances in fatty acid and cholesterol metabolism are linked to numerous diseases, including various types of malignancy. In tumor cells, metabolic alterations have been long recognized and intensively studied. However, metabolic changes in host cells in the tumor microenvironment and their contribution to tumor development have been largely overlooked. During the last decade, research advances show that fatty acid oxidation, cholesterol metabolism, and lipid accumulation play critical roles in cancer-associated host cells such as endothelial cells, lymph endothelial cells, cancer-associated fibroblasts, tumor-associated myeloid cells, and tumor-associated lymphocytes. In addition to anti-angiogenic therapies and immunotherapy that have been practiced in the clinic, metabolic regulation is considered another promising cancer therapy targeting non-tumor host cells. Understanding the obesity-associated metabolism changes in cancer-associated host cells may ultimately be translated into therapeutic options that benefit cancer patients. In this mini-review, we briefly summarize the lipid metabolism associated with obesity and its role in host cells in the tumor microenvironment. We also discuss the current understanding of the molecular pathways involved and future perspectives to benefit from this metabolic complexity.

The Relationship Between Reactive Oxygen Species and Endothelial Cell Metabolism

Cardiovascular disease (CVD) has been the leading cause of death for many decades, highlighting the importance of new research and treatments in the field. The role of hypoxia and subsequent free radical production [reactive oxygen species (ROS)] have become an area of particular interest in CVD. Interestingly, our laboratory and other laboratories have recently reported positive roles of subcellular ROS in modulating endothelial cell (EC) metabolism, proliferation, and angiogenesis. This bidirectional relationship between ROS and EC metabolism, as well as functional changes, continues to be an area of active research. Interestingly, ECs have been shown to rely on anaerobic processes for ATP generation, despite their direct access to oxygen. This paradox has proven to be beneficial as the major reliance on glycolysis produces ATP faster, preserves oxygen, and results in reduced ROS levels in contrast to oxidative phosphorylation. This review will address the relationship between ROS and carbohydrate, lipid, and nitrogen metabolism in ECs, and their effects on EC phenotype such as sprouting angiogenesis.

FABP4 promotes invasion and metastasis of colon cancer by regulating fatty acid transport

Background

The prognosis of colon cancer is poor for metastasis, while the mechanism, especially adipocytes related, is not yet clear. The purpose of this study is to determine the effects of fatty acid binding protein 4 (FABP4), a transporter for lipids, on colon cancer progression.

Methods

The distribution of lipids and FABP4 was tested in the colon cancer tissues and adjacent normal tissues, and their relationship was also verified in vitro. Experiments about cellular invasion, migration and proliferation were performed to detect the impacts of FABP4 on the biological behaviors of colon cancer, and the positive results were checked in vivo. Meanwhile, the regulatory role of FABP4 in the energy and lipid metabolism was evaluated by the levels of triglyceride, ATP, LDH, glycerol and NEFA. At last, GO and KEGG analysis based on FABP4 overexpressed cells was performed, and the AKT pathway and epithelial-mesenchymal transition (EMT)-related proteins were determined by Western blot.

Results

Higher accumulation of lipids and stronger FABP4 transcription were observed in colon cancer tissues. Having been incubated with adipose tissue extract and overexpressed FABP4, colon cancer cells demonstrated enhanced lipid accumulation. In functional experiments, co-culture with adipose tissue extract significantly enhanced the invasion and migration of colon cancer cells, as well as the energy and lipid metabolism, and all these processes were reversed by FABP4 inhibitor. In addition, the metastasis of FABP4-overexpressed colon cancer cells was also significantly enhanced in vitro and in vivo. In terms of mechanism, the bioinformatics analysis showed that FABP4 was enriched in 11 pathways related to metabolic processes in FABP4 overexpressed cells. Finally, FABP4 overexpression improved EMT progression of colon cancer, as evidenced by the upregulation of Snail, MMP-2 and MMP-9, the downregulation of E-cadherin. The expression of p-Akt was also elevated.

Conclusion

FABP4 overexpression could increase FAs transport to enhance energy and lipid metabolism, and activate AKT pathway and EMT to promote the migration and invasion of colon cancer cells.

Knockdown of fatty acid binding protein 4 exacerbates Bacillus Calmette-Guerin infection-induced RAW264.7 cell apoptosis via the endoplasmic reticulum stress pathway

Mycobacterial infection can induce alveolar macrophage apoptosis, which plays a vital role in the pathogenesis of tuberculosis. Accumulating evidence has demonstrated that fatty acid oxidation is involved in apoptosis during various pathological processes, including bacterial infection. However, whether fatty acid oxidation regulates mycobacterial infection-induced macrophage apoptosis remains unclear. Hence, the present study aimed to investigate the role of fatty acid binding protein 4 (FABP4) which is a carrier protein for fatty acids, in regulating apoptosis in RAW264.7 cells infected with Bacillus Calmette-Guerin (BCG). In our study, the impact of BCG infection on apoptosis and fatty acid oxidation in RAW264.7 cells was examined. Notably, we found that FABP4 was overexpressed during this process. Furthermore, small interfering RNAs targeting FABP4 were used to investigate the role of FABP4 in regulating apoptosis and fatty acid oxidation in BCG-infected RAW264.7 cells. The results indicated that mycobacterial infection promoted apoptosis and enhanced fatty acid oxidation in RAW264.7 cells. Moreover, FABP4 knockdown exacerbated BCG-induced apoptosis and upregulated the expression of p-PERK, p-eIF2α and chop, which are endoplasmic reticulum (ER) stress markers. In addition, FABP4 knockdown promoted fatty acid oxidation and ROS production, which result in the activation of ER stress. Our data suggested that FABP4 knockdown exacerbated BCG-induced apoptosis in RAW264.7 cells via the ER stress pathway.

Intrarenal Renin Angiotensin System Imbalance During Postnatal Life Is Associated With Increased Microvascular Density in the Mature Kidney

Environmental stress during early life is an important factor that affects the postnatal renal development. We have previously shown that male rats exposed to maternal separation (MatSep), a model of early life stress, are normotensive but display a sex-specific reduced renal function and exacerbated angiotensin II (AngII)-mediated vascular responses as adults. Since optimal AngII levels during postnatal life are required for normal maturation of the kidney, this study was designed to investigate both short- and long-term effect of MatSep on (1) the renal vascular architecture and function, (2) the intrarenal renin-angiotensin system (RAS) components status, and (3) the genome-wide expression of genes in isolated renal vasculature. Renal tissue and plasma were collected from male rats at different postnatal days (P) for intrarenal RAS components mRNA and protein expression measurements at P2, 6, 10, 14, 21, and 90 and microCT analysis at P21 and 90. Although with similar body weight and renal mass trajectories from P2 to P90, MatSep rats displayed decreased renal filtration capacity at P90, while increased microvascular density at both P21 and P90 (p < 0.05). MatSep increased renal expression of renin, and angiotensin type 1 (AT1) and type 2 (AT2) receptors (p < 0.05), but reduced ACE2 mRNA expression and activity from P2-14 compared to controls. However, intrarenal levels of AngII peptide were reduced (p < 0.05) possible due to the increased degradation to AngIII by aminopeptidase A. In isolated renal vasculature from neonates, Enriched Biological Pathways functional clusters (EBPfc) from genes changed by MatSep reported to modulate extracellular structure organization, inflammation, and pro-angiogenic transcription factors. Our data suggest that male neonates exposed to MatSep could display permanent changes in the renal microvascular architecture in response to intrarenal RAS imbalance in the context of the atypical upregulation of angiogenic factors.

ECM1 secreted by HER2-overexpressing breast cancer cells promotes formation of a vascular niche accelerating cancer cell migration and invasion

The tumor microenvironment is increasingly recognized as key player in cancer progression. Investigating heterotypic interactions between cancer cells and their microenvironment is important for understanding how specific cell types support cancer. Forming the vasculature, endothelial cells (ECs) are a prominent cell type in the microenvironment of both normal and neoplastic breast gland. Here, we sought out to analyze epithelial-endothelial cross talk in the breast using isogenic non-tumorigenic vs. tumorigenic breast epithelial cell lines and primary ECs. The cellular model used here consists of D492, a breast epithelial cell line with stem cell properties, and two isogenic D492-derived EMT cell lines, D492M and D492HER2. D492M was generated by endothelial-induced EMT and is non-tumorigenic while D492HER2 is tumorigenic, expressing the ErbB2/HER2 oncogene. To investigate cellular cross talk, we used both conditioned medium (CM) and 2D/3D co-culture systems. Secretome analysis of D492 cell lines was performed using mass spectrometry and candidate knockdown (KD), and overexpression (OE) was done using siRNA and CRISPRi/CRISPRa technology. D492HER2 directly enhances endothelial network formation and activates a molecular axis in ECs promoting D492HER2 migration and invasion, suggesting an endothelial feedback response. Secretome analysis identified extracellular matrix protein 1 (ECM1) as potential angiogenic inducer in D492HER2. Confirming its involvement, KD of ECM1 reduced the ability of D492HER2-CM to increase endothelial network formation and induce the endothelial feedback, while recombinant ECM1 (rECM1) increased both. Interestingly, NOTCH1 and NOTCH3 expression was upregulated in ECs upon treatment with D492HER2-CM or rECM1 but not by CM from D492HER2 with ECM1 KD. Blocking endothelial NOTCH signaling inhibited the increase in network formation and the ability of ECs to promote D492HER2 migration and invasion. In summary, our data demonstrate that cancer-secreted ECM1 induces a NOTCH-mediated endothelial feedback promoting cancer progression by enhancing migration and invasion. Targeting this interaction may provide a novel possibility to improve cancer treatment.

Targeting Cancer Stem Cells to Overcome Therapy Resistance in Ovarian Cancer

Ovarian cancer is the most lethal gynecological malignancy due to its late detection and high recurrence rate. Resistance to conventional platinum-based therapies and metastasis are attributed to a population of cells within tumors called cancer stem cells, which possess stem-like features and are able to recapitulate new tumors. Recent studies have deepened the understanding of the biology of ovarian cancer stem cells and their special properties and have identified multiple markers and signaling pathways responsible for their self-renewal abilities. Targeting cancer stem cells represents the most promising strategy for overcoming therapy resistance and reducing mortality in ovarian cancer, but further efforts must be made to improve our understanding of the mechanisms involved in therapy resistance. In this review, we summarize our current knowledge about ovarian cancer stem cells, their involvement in metastasis and their interactions with the tumor microenvironment; we also discuss the therapeutic approaches that are being developed to target them to prevent tumor relapse.

Fatty Acid-binding Protein 4 Expression in Tumor Cells as a Potential Marker for Anaplastic Meningiomas

Meningiomas are highly vascularized tumors originating from arachnoid cap cells of the leptomeninges. The majority of meningiomas are classified as World Health Organization (WHO) grade I and display a benign clinical course with a low risk of recurrence. In contrast, WHO grade III meningiomas carry a high risk of recurrence and poor prognosis. However, it is commonly recognized that histopathologic grading does not always reliably predict recurrence or progression of meningiomas. Fatty acid-binding protein 4 (FABP4) is a small molecular weight lipid chaperone that plays a proangiogenic role in vascular endothelial cells. FABP4 is not expressed in normal brain vasculature but is detected in some glioblastoma and arteriovenous malformations. The expression pattern of FABP4 in meningiomas have not been reported to date. We analyzed FABP4 expression in a cohort of paraffin-embedded meningioma specimens by immunohistochemistry and double immunofluorescence analyses. FABP4 expression was detected in a subset of endothelial cells in 47 of 48 meningioma samples analyzed. Interestingly, tumor cell-FABP4 expression was also detected in only 1 of 22 grade I, none of grade II, but 10 of 12 grade III meningiomas (P<0.0001). These results demonstrate that FABP4 is commonly expressed in meningioma vascular endothelial cells while tumor cell expression of FABP4 is primarily observed in anaplastic meningiomas. A combination of FABP4 immunostaining with histopathologic grading might provide a more accurate prediction of the biological behavior of meningiomas than histopathologic grading alone.

Adipocyte-Induced FABP4 Expression in Ovarian Cancer Cells Promotes Metastasis and Mediates Carboplatin Resistance

Adipocytes are critical for ovarian cancer cells to home to the omentum, but the metabolic changes initiated by this interaction are unknown. To this end, we carried out unbiased mass spectrometry-based metabolomic and proteomic profiling of cancer cells cocultured with primary human omental adipocytes. Cancer cells underwent significant proteo-metabolomic alteration(s), typified by changes in the lipidome with corresponding upregulation of lipid metabolism proteins. FABP4, a lipid chaperone protein, was identified as the critical regulator of lipid responses in ovarian cancer cells cocultured with adipocytes. Subsequently, knockdown of FABP4 resulted in increased 5-hydroxymethylcytosine levels in the DNA, downregulation of gene signatures associated with ovarian cancer metastasis, and reduced clonogenic cancer cell survival. In addition, clustered regularly interspaced short palindromic repeats (CRISPR)-mediated knockout of FABP4 in high-grade serous ovarian cancer cells reduced metastatic tumor burden in mice. Consequently, a small-molecule inhibitor of FABP4 (BMS309403) not only significantly reduced tumor burden in a syngeneic orthotopic mouse model but also increased the sensitivity of cancer cells toward carboplatin both in vitro and in vivo. Taken together, these results show that targeting FABP4 in ovarian cancer cells can inhibit their ability to adapt and colonize lipid-rich tumor microenvironments, providing an opportunity for specific metabolic targeting of ovarian cancer metastasis. SIGNIFICANCE: Ovarian cancer metastatic progression can be restricted by targeting a critical regulator of lipid responses, FABP4.

PAX2 promotes epithelial ovarian cancer progression involving fatty acid metabolic reprogramming

Ovarian cancer is the fifth most common type of cancer afflicting women and frequently presents at a late stage with a poor prognosis. While paired box 2 (PAX2) expression is frequently lost in high-grade serous ovarian cancer, it is expressed in a subset of ovarian tumors and may play a role in tumorigenesis. This study investigated the expression of PAX2 in ovarian cancer. The expression of PAX2 in a murine allograft model of ovarian cancer, the RM model, led to a more rapidly growing cell line both in vitro and in vivo. This finding was in accordance with the shorter progression-free survival observed in patients with a higher PAX2 expression, as determined in this study cohort by immunohistochemistry. iTRAQ-based proteomic profiling revealed that proteins involved in fatty acid metabolism and oxidative phosphorylation were found to be upregulated in RM tumors expressing PAX2. The expression of two key fatty acid metabolic genes was also found to be upregulated in PAX2-expressing human ovarian cancer samples. The analysis of existing datasets also indicated that a high expression of key enzymes in fatty acid metabolism was associated with a shorter progression-free survival time in patients with serous ovarian cancer. Thus, on the whole, the findings of this study indicate that PAX2 may promote ovarian cancer progression, involving fatty acid metabolic reprograming.

Role of fatty acid binding proteins (FABPs) in cancer development and progression

Fatty acid binding proteins (FABPs) are small, water soluble proteins that bind long chain fatty acids and other biologically active ligands to facilitate intracellular localization. Twelve FABP family members have been identified to date, with 10 isoforms expressed in humans. Functionally, FABPs are important in fatty acid metabolism and transport, with distinct family members having the capacity to influence gene transcription. Expression of FABPs is usually cell/tissue specific to one predominant FABP family member. Dysregulation of FABP expression can occur through genetic mutation and/or environmental-lifestyle influences. In addition to intracellular function, exogenous, circulating FABP expression can occur and is associated with specific disease states such as insulin resistance. A role for FABPs is increasingly being reported in tumor biology with elevated exogenous FABP expression being associated with tumor progression and invasiveness. However, a less clear role has been appreciated for dysregulated FABP expression during cell transformation and early expansion.

RDH1 suppresses adiposity by promoting brown adipose adaptation to fasting and re-feeding

RDH1 is one of the several enzymes that catalyze the first of the two reactions to convert retinol into all-trans-retinoic acid (atRA). Here, we show that Rdh1-null mice fed a low-fat diet gain more weight as adiposity (17% males, 13% females) than wild-type mice by 20 weeks old, despite neither consuming more calories nor decreasing activity. Glucose intolerance and insulin resistance develop following increased adiposity. Despite the increase in white fat pads, epididymal white adipose does not express Rdh1, nor does muscle. Brown adipose tissue (BAT) and liver express Rdh1 at relatively high levels compared to other tissues. Rdh1 ablation lowered body temperatures during ambient conditions. Given the decreased body temperature, we focused on BAT. A lack of differences in BAT adipogenic gene expression between Rdh1-null mice and wild-type mice, including Pparg, Prdm16, Zfp516 and Zfp521, indicated that the phenotype was not driven by brown adipose hyperplasia. Rather, Rdh1 ablation eliminated the increase in BAT atRA that occurs after re-feeding. This disruption of atRA homeostasis increased fatty acid uptake, but attenuated lipolysis in primary brown adipocytes, resulting in increased lipid content and larger lipid droplets. Rdh1 ablation also decreased mitochondrial proteins, including CYCS and UCP1, the mitochondria oxygen consumption rate, and disrupted the mitochondria membrane potential, further reflecting impaired BAT function, resulting in both BAT and white adipose hypertrophy. RNAseq revealed dysregulation of 424 BAT genes in null mice, which segregated predominantly into differences after fasting vs after re-feeding. Exceptions were Rbp4 and Gbp2b, which increased during both dietary conditions. Rbp4 encodes the serum retinol-binding protein-an insulin desensitizer. Gbp2b encodes a GTPase. Because Gbp2b increased several hundred-fold, we overexpressed it in brown adipocytes. This caused a shift to larger lipid droplets, suggesting that GBP2b affects signaling downstream of the β-adrenergic receptor during basal thermogenesis. Thus, Rdh1-generated atRA in BAT regulates multiple genes that promote BAT adaptation to whole-body energy status, such as fasting and re-feeding. These gene expression changes promote optimum mitochondria function and thermogenesis, limiting adiposity. Attenuation of adiposity and insulin resistance suggests that RDH1 mitigates metabolic syndrome.

Adipokine FABP4 integrates energy stores and counterregulatory metabolic responses

Although counterregulatory hormones and mediators of the fight-or-flight responses are well defined at many levels, how energy stores per se are integrated into this system remains an enigmatic question. Recent years have seen the adipose tissue become a central focus for mediating intracellular signaling and communication through the release of a variety of bioactive lipids and substrates, as well as various adipokines. A critical integration node among these mediators and responses is controlled by FA binding protein 4 (FABP4), also known as adipocyte protein 2 (aP2), which is highly expressed in adipose tissue and functions as a lipid chaperone protein. Recently, it was demonstrated that FABP4 is a secreted hormone that has roles in maintaining glucose homeostasis, representing a key juncture facilitating communication between energy-storage systems and distant organs to respond to life-threatening situations. However, chronic engagement of FABP4 under conditions of immunometabolic stress, such as obesity, exacerbates a number of immunometabolic diseases, including diabetes, asthma, cancer, and atherosclerosis. In both preclinical mouse models and humans, levels of circulating FABP4 have been correlated with metabolic disease incidence, and reducing FABP4 levels or activity is associated with improved metabolic health. In this review, we will discuss the intriguing emerging biology of this protein, including potential therapeutic options for targeting circulating FABP4.

Regulation of the bi-directional cross-talk between ovarian cancer cells and adipocytes by SPARC

Ovarian cancer (OvCa) exhibits a specific predilection for metastasis to the omentum. Our earlier studies highlighted the tumour-suppressor effect of secreted protein acidic and rich in cysteine (SPARC) in OvCa through multi-faceted roles inhibiting cancer cell interactions within the peritoneal milieu. The goal of this study is to investigate the role of SPARC in OvCa interactions with omental adipocytes and its role in OvCa colonization in the omentum. We employed multi-pronged approach using primary omental adipocytes from Sparc knockout mice, genetically engineered human omental adipocytes in 3D co-cultures with OvCa cells, as well as treatment with recombinant SPARC protein. We show that SPARC suppresses multistep cascade in OvCa omental metastasis. SPARC inhibited in vivo and adipocyte-induced homing, proliferation, and invasion of OvCa cells. SPARC suppressed metabolic programming of both adipocytes and OvCa cells and exerted an inhibitory effect of adipocyte differentiation and their phenotypic switch to cancer-associated phenotype. Mechanistic studies revealed that this effect is mediated through inhibition of cEBPβ-NFkB-AP-1 transcription machinery. These findings define a novel and functionally important role of SPARC in OvCa and not only bridge the knowledge gap but highlight the need to consider SPARC protein expression in therapeutic development.

FABP4 inhibitors 3D-QSAR model and isosteric replacement of BMS309403 datasets

The data have been obtained from FABP4 inhibitor molecules previously published. The 120 compounds were used to build a 3D-QSAR model. The development of the QSAR model has been undertaken with the use of Forge software using the PM3 optimized structure and the experimental IC₅₀ of each compound. The QSAR model was also employed to predict the activity of 3000 new isosteric derivatives of BMS309403. The isosteric replacement was also validated by the synthesis and the biological screening of three new compounds reported in the related research article “3D-QSAR assisted identification of FABP4 inhibitors: An effective scaffold hopping analysis/QSAR evaluation” (Floresta et al., 2019).

An evolving story of the metastatic voyage of ovarian cancer cells: cellular and molecular orchestration of the adipose-rich metastatic microenvironment

Metastasis is a complex multistep process that involves critical interactions between cancer cells and a variety of stromal components in the tumor microenvironment, which profoundly influence the different aspects of the metastatic cascade and organ tropism of disseminating cancer cells. Ovarian cancer is the most lethal gynecological malignancy and is characterized by peritoneal disseminated metastasis. Evidence has demonstrated that ovarian cancer possesses specific metastatic tropism for the adipose-rich omentum, which has a pivotal role in the creation of the metastatic tumor microenvironment in the intraperitoneal cavity. Considering the distinct biology of ovarian cancer metastasis, the elucidation of the cellular and molecular mechanisms underlying the reciprocal interplay between ovarian cancer cells and surrounding stromal cell types in the adipose-rich metastatic microenvironment will provide further insights into the development of novel therapeutic approaches for patients with advanced ovarian cancer. Herein, we review the biological mechanisms that regulate the highly orchestrated crosstalk between ovarian cancer cells and various cancer-associated stromal cells in the metastatic tumor microenvironment with regard to the omentum by illustrating how different stromal cells concertedly contribute to the development of ovarian cancer metastasis and metastatic tropism for the omentum.

Quiescent Endothelial Cells Upregulate Fatty Acid β-Oxidation for Vasculoprotection via Redox Homeostasis

Little is known about the metabolism of quiescent endothelial cells (QECs). Nonetheless, when dysfunctional, QECs contribute to multiple diseases. Previously, we demonstrated that proliferating endothelial cells (PECs) use fatty acid β-oxidation (FAO) for de novo dNTP synthesis. We report now that QECs are not hypometabolic, but upregulate FAO >3-fold higher than PECs, not to support biomass or energy production but to sustain the tricarboxylic acid cycle for redox homeostasis through NADPH regeneration. Hence, endothelial loss of FAO-controlling CPT1A in CPT1A^ΔEC mice promotes EC dysfunction (leukocyte infiltration, barrier disruption) by increasing endothelial oxidative stress, rendering CPT1A^ΔEC mice more susceptible to LPS and inflammatory bowel disease. Mechanistically, Notch1 orchestrates the use of FAO for redox balance in QECs. Supplementation of acetate (metabolized to acetyl-coenzyme A) restores endothelial quiescence and counters oxidative stress-mediated EC dysfunction in CPT1A^ΔEC mice, offering therapeutic opportunities. Thus, QECs use FAO for vasculoprotection against oxidative stress-prone exposure.

FABP4 regulates eosinophil recruitment and activation in allergic airway inflammation

Fatty acid binding protein 4 (FABP4), a member of a family of lipid-binding proteins, is known to play a role in inflammation by virtue of its ability to regulate intracellular events such as lipid fluxes and signaling. Studies have indicated a proinflammatory role for FABP4 in allergic asthma although its expression and function in eosinophils, the predominant inflammatory cells recruited to allergic airways, were not investigated. We examined expression of FABP4 in murine eosinophils and its role in regulating cell recruitment in vitro as well as in cockroach antigen (CRA)-induced allergic airway inflammation. CRA exposure led to airway recruitment of FABP4-expressing inflammatory cells, specifically eosinophils, in wild-type (WT) mice. FABP4 expression in eosinophils was induced by TNF-α as well as IL-4 and IL-13. FABP4-deficient eosinophils exhibited markedly decreased cell spreading/formation of leading edges on vascular cell adhesion molecule-1 and significantly decreased adhesion to intercellular adhesion molecule-1 associated with reduced β2-integrin expression relative to WT cells. Furthermore, FABP4-deficient eosinophils exhibited decreased migration, F-actin polymerization, calcium flux, and ERK(1/2) phosphorylation in response to eotaxin-1. In vivo, CRA-challenged FABP4-deficient mice exhibited attenuated eosinophilia and significantly reduced airway inflammation (improved airway reactivity, lower IL-5, IL-13, TNF-α, and cysteinyl leukotriene C4 levels, decreased airway structural changes) compared with WT mice. In conclusion, expression of FABP4 in eosinophils is induced during conditions of inflammation and plays a proinflammatory role in the development of allergic asthma by promoting eosinophil adhesion and migration and contributing to the development of various aspects of airway inflammation.

FABP4 as a key determinant of metastatic potential of ovarian cancer

The standard treatment for high-grade serous ovarian cancer is primary debulking surgery followed by chemotherapy. The extent of metastasis and invasive potential of lesions can influence the outcome of these primary surgeries. Here, we explored the underlying mechanisms that could increase metastatic potential in ovarian cancer. We discovered that FABP4 (fatty acid binding protein) can substantially increase the metastatic potential of cancer cells. We also found that miR-409-3p regulates FABP4 in ovarian cancer cells and that hypoxia decreases miR-409-3p levels. Treatment with DOPC nanoliposomes containing either miR-409-3p mimic or FABP4 siRNA inhibited tumor progression in mouse models. With RPPA and metabolite arrays, we found that FABP4 regulates pathways associated with metastasis and affects metabolic pathways in ovarian cancer cells. Collectively, these findings demonstrate that FABP4 is functionally responsible for aggressive patterns of disease that likely contribute to poor prognosis in ovarian cancer.

Fatty Acid Binding Protein 4 (FABP4) Overexpression in Intratumoral Hepatic Stellate Cells within Hepatocellular Carcinoma with Metabolic Risk Factors

Metabolic syndrome is a newly identified risk factor for hepatocellular carcinoma (HCC); however, tumor-specific biomarkers still remain unclear. We performed cross-species analysis to compare gene signatures of HCC from human patients and melanocortin 4 receptor-knockout mice, which develop HCC with obesity, insulin resistance, and dyslipidemia. Unsupervised hierarchical clustering and principle component analysis of 746 differentially expressed orthologous genes classified HCC of 152 human patients and melanocortin 4 receptor-knockout mice into two distinct subgroups, one of which included mouse HCC and was causatively associated with metabolic risk factors. Nine genes commonly overexpressed in human and mouse metabolic disease-associated HCC were identified; fatty acid binding protein 4 (FABP4) was remarkably enriched in intratumoral activated hepatic stellate cells (HSCs). Subclones constitutively expressing FABP4 were established from a human HSC cell line in which expression levels of inflammatory chemokines, including IL-1A and IL-6, were up-regulated through NF-κB nuclear translocation, resulting in recruitment of macrophages. An immunohistochemical validation study of 106 additional human HCC samples indicated that FABP4-positive HSCs were distributed in tumors of 38 cases, and the FABP4-high group consisted of patients with nonviral and nonalcoholic HCC (P = 0.027) and with multiple metabolic risk factors (P < 0.001) compared with the FABP4-low group. Thus, FABP4 overexpression in HSCs may contribute to hepatocarcinogenesis in patients with metabolic risk factors by modulation of inflammatory pathways.

A lipid-based cell penetrating nano-assembly for RNAi-mediated anti-angiogenic cancer therapy

A tissue infiltrating peptide amphiphile-decorated nano-assembly induces significant mouse tumor growth inhibition via substantial tumor infiltration of encapsulated anti-angiogenic siRNA.

Endothelial Cell Metabolism

Endothelial cells (ECs) are more than inert blood vessel lining material. Instead, they are active players in the formation of new blood vessels (angiogenesis) both in health and (life-threatening) diseases. Recently, a new concept arose by which EC metabolism drives angiogenesis in parallel to well-established angiogenic growth factors (e.g., vascular endothelial growth factor). 6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3-driven glycolysis generates energy to sustain competitive behavior of the ECs at the tip of a growing vessel sprout, whereas carnitine palmitoyltransferase 1a-controlled fatty acid oxidation regulates nucleotide synthesis and proliferation of ECs in the stalk of the sprout. To maintain vascular homeostasis, ECs rely on an intricate metabolic wiring characterized by intracellular compartmentalization, use metabolites for epigenetic regulation of EC subtype differentiation, crosstalk through metabolite release with other cell types, and exhibit EC subtype-specific metabolic traits. Importantly, maladaptation of EC metabolism contributes to vascular disorders, through EC dysfunction or excess angiogenesis, and presents new opportunities for anti-angiogenic strategies. Here we provide a comprehensive overview of established as well as newly uncovered aspects of EC metabolism.

Fatty acid binding protein 4 enhances prostate cancer progression by upregulating matrix metalloproteinases and stromal cell cytokine production

Fatty acid binding protein 4 (FABP4) is an abundant protein in adipocytes, and its production is influenced by high-fat diet (HFD) or obesity. The prostate stromal microenvironment induces proinflammatory cytokine production, which is key for the development and progression of prostate cancer (PCa). Here, we show that high FABP4 expression and its secretion by PCa cells directly stimulated PCa cell invasiveness by upregulating matrix metalloproteinases through phosphatidylinositol 3-kinase and mitogen-activated protein kinase signaling pathways. In addition, prostate stromal cells augmented PCa cell invasiveness by secreting interleukin-8 and -6 in response to FABP4. This was abrogated by the FABP4 specific inhibitor, BMS309403. Furthermore, a mouse xenograft experiment showed HFD enhanced PCa metastasis and invasiveness by the upregulation of FABP4 and interleukin-8. Clinically, the serum level of FABP4 was significantly associated with an aggressive type of PCa rather than obesity. Taken together, FABP4 may enhance PCa progression and invasiveness by upregulating matrix metalloproteinases and cytokine production in the PCa stromal microenvironment, especially under HFD or obesity.

Scutellarin suppresses human colorectal cancer metastasis and angiogenesis by targeting ephrinb2

Tumor induced angiogenesis is an attractive target for anti-cancer drug treatment. Scutellarin, which is a native compound derived from scutellaria altissima leaves, has already been proved to possess anti-tumor activities. Nevertheless, their effects in colorectal cancer metastasis and angiogenesis have not been evaluated. In order to reveal the anti-angiogenic and anti-metastasis capacity of scutellarin, wound healing and Transwell chamber inserts invasion were done in colorectal cancer cells, and cell proliferation as wells colony formation were conducted to identify the proliferation inhibition of colorectal cancer in vitro. The growth inhibition of scutellarin was further definite by a mouse colorectal xenograft model in vivo. Herein, we demonstrated scutellarin suppressed colorectal cancer cell viability and colony formation in vitro, and remarkably reduced tumor growth in vivo mouse xenografts. Additionally, scutellarin restrained colorectal cancer cells-induced angiogenesis, inhibited human umbilical vascular endothelial cells (HUVECs) migration, tube formation of HUVECs, and micro-vessel formation in chick embnyo chorioallantoic menbreme (CAM) assay. Altogether, our results exhibited the evidence that scutellarin inhibit colorectal cancer angiogenesis and metastasis via targeting ephrinb2 signaling, with the potential of an anti-tumor agent for cancer treatment.

Revisiting ovarian cancer microenvironment: a friend or a foe?

Development of ovarian cancer involves the co-evolution of neoplastic cells together with the adjacent microenvironment. Steps of malignant progression including primary tumor outgrowth, therapeutic resistance, and distant metastasis are not determined solely by genetic alterations in ovarian cancer cells, but considerably shaped by the fitness advantage conferred by benign components in the ovarian stroma. As the dynamic cancer topography varies drastically during disease progression, heterologous cell types within the tumor microenvironment (TME) can actively determine the pathological track of ovarian cancer. Resembling many other solid tumor types, ovarian malignancy is nurtured by a TME whose dark side may have been overlooked, rather than overestimated. Further, harnessing breakthrough and targeting cures in human ovarian cancer requires insightful understanding of the merits and drawbacks of current treatment modalities, which mainly target transformed cells. Thus, designing novel and precise strategies that both eliminate cancer cells and manipulate the TME is increasingly recognized as a rational avenue to improve therapeutic outcome and prevent disease deterioration of ovarian cancer patients.

Opportunities and Challenges for Fatty Acid Mimetics in Drug Discovery

Fatty acids beyond their role as an endogenous energy source and storage are increasingly considered as signaling molecules regulating various physiological effects in metabolism and inflammation. Accordingly, the molecular targets involved in formation and physiological activities of fatty acids hold significant therapeutic potential. A number of these fatty acid targets are addressed by some of the oldest and most widely used drugs such as cyclooxygenase inhibiting NSAIDs, whereas others remain unexploited. Compounds orthosterically binding to proteins that endogenously bind fatty acids are considered as fatty acid mimetics. On the basis of their structural resemblance, fatty acid mimetics constitute a family of bioactive compounds showing specific binding thermodynamics and following similar pharmacokinetic mechanisms. This perspective systematically evaluates targets for fatty acid mimetics, investigates their common structural characteristics, and highlights demands in their discovery and design. In summary, fatty acid mimetics share particularly favorable characteristics justifying the conclusion that their therapeutic potential vastly outweighs the challenges in their design.