A novel cutaneous Fatty Acid-binding protein-related signaling pathway leading to malignant progression in prostate cancer cells

FABP5 can substitute for androgen receptor in malignant progression of prostate cancer cells

Fatty acid‑binding protein 5 (FABP5) and androgen receptor (AR) are critical promoters of prostate cancer. In the present study, the effects of knocking out the FABP5 or AR genes on malignant characteristics of prostate cancer cells were investigated, and changes in the expression of certain key proteins in the FABP5 (or AR)‑peroxisome proliferator activated receptor‑γ (PPARγ)‑vascular endothelial growth factor (VEGF) signaling pathway were monitored. The results obtained showed that FABP5‑ or AR‑knockout (KO) led to a marked suppression of the malignant characteristics of the cells, in part, through disrupting this signaling pathway. Moreover, FABP5 and AR are able to interact with each other to regulate this pathway, with FABP5 controlling the dominant AR splicing variant 7 (ARV7), and AR, in return, regulates the expression of FABP5. Comparisons of the RNA profiles revealed the existence of numerous differentially expressed genes (DEGs) comparing between the parental and the FABP5‑ or AR‑KO cells. The six most abundant changes in DEGs were found to be attributable to the transition from androgen‑responsive to androgen‑unresponsive, castration‑resistant prostate cancer (CRPC) cells. These findings have provided novel insights into the complex molecular pathogenesis of CRPC cells, and have demonstrated that interactions between FABP5 and AR contribute to the transition of prostate cancer cells to an androgen‑independent state. Moreover, gene enrichment analysis revealed that the most highly enriched biological processes associated with the DEGs included those responsive to fatty acids, cholesterol and sterol biosynthesis, as well as to lipid and fatty acid transportation. Since these pathways regulated by FABP5 or AR may be crucial in terms of transducing signals for cancer cell progression, targeting FABP5, AR and their associated pathways, rather than AR alone, may provide a new avenue for the development of therapeutic strategies geared towards suppressing the malignant progression to CRPC cells.

Experimental treatment efficacy of dmrFABP5 on prostate cancer singly or in combination with drugs in use

Enzalutamide is a drug used to treat prostate cancer (PC) and docetaxel is a drug for chemotherapeutic treatment of diverse cancer types, including PC. The effectiveness of these drugs in treating castration-resistant prostate cancer (CRPC) is poor and therefore CRPC is still largely incurable. However, the bio-inhibitor of fatty acid-binding protein 5 (FABP5), dmrFABP5, which is a mutant form of FABP5 incapable of binding to fatty acids, has been shown recently to be able to suppress the tumorigenicity and metastasis of cultured CRPC cells. The present study investigated the possible synergistic effect of dmrFABP5 combined with either enzalutamide or docetaxel on suppressing the tumorigenic properties of PC cells, including cell viability, migration, invasion and colony proliferation in soft agar. A highly significant synergistic inhibitory effect on these properties was observed when dmrFABP5 was used in combination with enzalutamide on androgen-responsive PC 22RV1 cells. Moreover, a highly significant synergistic inhibitory effect was also observed when dmrFABP5 was combined with docetaxel, and added to 22RV1 cells and to the highly malignant, androgen-receptor (AR)-negative Du145 cells. DmrFABP5 alone failed to produce any suppressive effect when added to the FABP5-negative cell line LNCaP, although enzalutamide could significantly suppress LNCaP cells when used as a single agent. These synergistic inhibitory effects of dmrFABP5 were produced by interrupting the FABP5-related signal transduction pathway in PC cells. Thus, dmrFABP5 appears to be not only a potential single therapeutic agent, but it may also be used in combination with existing drugs to suppress both AR-positive and AR-negative 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.

Melatonin Modulates the SIRT1-Related Pathways via Transdermal Cryopass-Laser Administration in Prostate Tumor Xenograft

Melatonin displays antitumor activity in several types of malignancies; however, the best delivery route and the underlying mechanisms are still unclear. Alternative non-invasive delivery route based on transdermal administration of melatonin by cryopass-laser treatment demonstrated efficiency in reducing the progression of LNCaP prostate tumor cells xenografted into nude mice by impairing the biochemical pathways affecting redox balance. Here, we investigated the impact of transdermal melatonin on the tumor dimension, microenvironment structure, and SIRT1-modulated pathways. Two groups (vehicle cryopass-laser and melatonin cryopass-laser) were treated for 6 weeks (3 treatments per week), and the tumors collected were analyzed for hematoxylin eosin staining, sirius red, and SIRT1 modulated proteins such as PGC-1α, PPARγ, and NFkB. Melatonin in addition to simple laser treatment was able to boost the antitumor cancer activity impairing the tumor microenvironment, increasing the collagen structure around the tumor, and modulating the altered SIRT1 pathways. Transdermal application is effective, safe, and feasible in humans as well, and the significance of these findings necessitates further studies on the antitumor mechanisms exerted by melatonin.

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 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.

Lycorine induces apoptosis of acute myeloid leukemia cells and inhibits triglyceride production via binding and targeting FABP5

Acute myeloid leukemia (AML) is the most common hematopoietic malignancy with abnormal lipid metabolism. However, currently available information on the involvement of the alterations in lipid metabolism in AML development is limited. In this study, we demonstrate that FABP5 expression facilitates AML cell viability, protects AML cells from apoptosis, and maintains triglyceride production. Our bioinformatics analysis revealed that FABP5 expression was upregulated and correlated with unfavorable overall survival of AML patients. FABP5 expression may be used to distinguish normal and AML with high accuracy. FABP5-based risk score was an independent risk factor for AML patients. AML patients with highly expressed FABP5 predicted resistance to drugs. In vitro study showed that FABP5 expression was remarkably elevated in primary AML blasts and an AML cell line. Silencing FABP5 expression attenuated AML cell viability, reduced triglyceride production and lipid droplet accumulation, and induced apoptosis. We utilized AutoDock online tool to identify lycorine as an FABP5 inhibitor by binding FABP5 at amino acid residues Ile54, Thr56, Thr63, and Arg109. Lycorine treatment downregulated the expression levels of FABP5 and its target PPARγ, impaired AML cell viability, triggered apoptosis, and reduced triglyceride production in AML cells. These results demonstrate that FABP5 is critical for AML cell survival and highlight a novel metabolic vulnerability for AML.

Molecular mechanisms on how FABP5 inhibitors promote apoptosis-induction sensitivity of prostate cancer cells

Previous work showed that FABP5 inhibitors suppressed the malignant progression of prostate cancer cells, and this suppression might be achieved partially by promoting apoptosis. But the mechanisms involved were not known. Here, we investigated the effect of inhibitors on apoptosis and studied the relevant mechanisms. WtrFABP5 significantly reduced apoptotic cells in 22Rv1 and PC3 by 18% and 42%, respectively. In contrast, the chemical inhibitor SB-FI-26 produced significant increases in percentages of apoptotic cells in 22Rv1 and PC3 by 18.8% (±4.1) and 4.6% (±1.1), respectively. The bio- inhibitor dmrFABP5 also did so by 23.1% (±2.4) and 15.8% (±3.0), respectively, in these cell lines. Both FABP5 inhibitors significantly reduced the levels of the phosphorylated nuclear fatty acid receptor PPARγ, indicating that these inhibitors promoted apoptosis-induction sensitivity of the cancer cells by suppressing the biological activity of PPARγ. Thus, the phosphorylated PPARγ levels were reduced by FABP5 inhibitors, the levels of the phosphorylated AKT and activated nuclear factor kapper B (NFκB) were coordinately altered by additions of the inhibitors. These changes eventually led to the increased levels of cleaved caspase-9 and cleaved caspase-3; and thus, increase in the percentage of cells undergoing apoptosis. In untreated prostate cancer cells, increased FABP5 suppressed the apoptosis by increasing the biological activity of PPARγ, which, in turn, led to a reduced apoptosis by interfering with the AKT or NFκB signaling pathway. Our results suggested that the FABP5 inhibitors enhanced the apoptosis-induction of prostate cancer cells by reversing the biological effect of FABP5 and its related pathway.

m6A-induced lncDBET promotes the malignant progression of bladder cancer through FABP5-mediated lipid metabolism

The limited effect of adjuvant therapy for advanced bladder cancer (BCa) leads to a poor prognosis. Increasing evidence has shown that RNA N6-methyladenosine (m⁶A) modification plays important functional roles in tumorigenesis. Nevertheless, the role and mechanism of m6A-modified noncoding RNAs (ncRNAs) in BCa remain largely unknown.

Methods: RT-PCR, western blotting and ONCOMINE dataset were used to determine the dominant m⁶A-related enzyme in BCa. M⁶A-lncRNA epitranscriptomic microarray was used to screen candidate targets of METTL14. RT-PCR, MeRIP and TCGA dataset were carried out to confirm the downstream target of METTL14. CHIRP/MS was conducted to identify the candidate proteins binding to lncDBET. RT-PCR, western blotting, RIP and KEGG analysis were used to confirm the target of lncDBET. The levels of METTL14, lncDBET and FABP5 were tested in vitro and in vivo. CCK-8, EdU, transwell and flow cytometry assays were performed to determine the oncogenic function of METTL14, lncDBET and FABP5, and their regulatory networks.

Results: We identified that the m⁶A level of total RNA was elevated and that METTL14 was the dominant m6A-related enzyme in BCa. m⁶A modification mediated by METTL14 promoted the malignant progression of BCa by promoting the expression of lncDBET. Upregulated lncDBET activated the PPAR signalling pathway to promote the lipid metabolism of cancer cells through direct interaction with FABP5, thus promoting the malignant progression of BCa in vitro and in vivo.

Conclusions: Our study establishes METTL14/lncDBET/FABP5 as a critical oncogenic axis in BCa.

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.

Transcriptome-based biomarker gene screening and evaluation of the extracellular fatty acid-binding protein (Ex-FABP) on immune and angiogenesis-related genes in chicken erythrocytes of tibial dyschondroplasia

BACKGROUND

Tibial dyschondroplasia (TD) is a bone disorder in which dead chondrocytes accumulate as a result of apoptosis and non-vascularization in the tibial bone of broiler chickens. The pathogenicity of TD is under extensive research but is yet not fully understood. Several studies have linked it to apoptosis and non-vascularization in the tibial growth plate (GP). We conceived the idea to find the differentially expressed genes (DEGs) in chicken erythrocytes which vary in expression over time using a likelihood-ratio test (LRT). Thiram was used to induce TD in chickens, and then injected Ex-FABP protein at 0, 20, and 50 μg^.kg^-1 to evaluate its therapeutic effect on 30 screened immunity and angiogenesis-related genes using quantitative PCR (qPCR). The histopathology was also performed in TD chickens to explore the shape, circularity, arrangements of chondrocytes and blood vessels.

RESULTS

Clinical lameness was observed in TD chickens, which decreased with the injection of Ex-FABP. Histopathological findings support Ex-FABP as a therapeutic agent for the morphology and vascularization of affected chondrocytes in TD chickens. qPCR results of 10 immunity (TLR2, TLR3, TLR4, TLR5, TLR7, TLR15, IL-7, MyD88, MHCII, and TRAF6) and 20 angiogenesis-related genes (ITGAV, ITGA2, ITGB2, ITGB3, ITGA5, IL1R1, TBXA2R, RPL17, F13A1, CLU, RAC2, RAP1B, GIT1, FYN, IQGAP2, PTCH1, NCOR2, VAV-like, PTPN11, MAML3) regulated when Ex-FABP is injected to TD chickens.

CONCLUSION

Immunity and angiogenesis-related genes can be responsible for apoptosis of chondrocytes and vascularization in tibial GP. Injection of Ex-FABP protein to thiram induced TD chickens decrease the chondrocytes damage and improves vascularization.

The Biological Functions and Regulatory Mechanisms of Fatty Acid Binding Protein 5 in Various Diseases

In recent years, fatty acid binding protein 5 (FABP5), also known as fatty acid transporter, has been widely researched with the help of modern genetic technology. Emerging evidence suggests its critical role in regulating lipid transport, homeostasis, and metabolism. Its involvement in the pathogenesis of various diseases such as metabolic syndrome, skin diseases, cancer, and neurological diseases is the key to understanding the true nature of the protein. This makes FABP5 be a promising component for numerous clinical applications. This review has summarized the most recent advances in the research of FABP5 in modulating cellular processes, providing an in-depth analysis of the protein’s biological properties, biological functions, and mechanisms involved in various diseases. In addition, we have discussed the possibility of using FABP5 as a new diagnostic biomarker and therapeutic target for human diseases, shedding light on challenges facing future research.

The covalent reactivity of functionalized 5-hydroxy-butyrolactams is the basis for targeting of fatty acid binding protein 5 (FABP5) by the neurotrophic agent MT-21

Covalently acting compounds experience a strong interest within chemical biology both as molecular probes in studies of fundamental biological mechanisms and/or as novel drug candidates. In this context, the identification of new classes of reactive groups is particularly important as these can expose novel reactivity modes and, consequently, expand the ligandable proteome. Here, we investigated the electrophilic reactivity of the 3-acyl-5-hydroxy-1,5-dihydro-2H-pyrrole-2-one (AHPO) scaffold, a heterocyclic motif that is e.g. present in various bioactive natural products. Our investigations were focused on the compound MT-21 – a simplified structural analogue of the natural product epolactaene – which is known to have both neurotrophic activity and ability to trigger apoptotic cell death. We found that the central N-acyl hemiaminal group of MT-21 can function as an electrophilic centre enabling divergent reactivity with both amine- and thiol-based nucleophiles, which furthermore translated to reactivity with proteins in both cell lysates and live cells. We found that in live cells MT-21 strongly engaged the lipid transport protein fatty acid-binding protein 5 (FABP5) by direct binding to a cysteine residue in the bottom of the ligand binding pocket. Through preparation of a series of MT-21 derivatives, we probed the specificity of this interaction which was found to be strongly dependent on subtle structural changes. Our study suggests that MT-21 may be employed as a tool compound in future studies of the biology of FABP5, which remains incompletely understood. Furthermore, our study has also made clear that other natural products containing the AHPO-motif may likewise possess covalent reactivity and that this property may underlie their biological activity.

In this work, it is shown that an N-acyl hemiaminal motif present in many natural products can function as an electrophilic centre, mediating covalent reactivity in biological systems, reacting with both thiols and amines.

Expression Profiles and Prognostic Value of FABPs in Colorectal Adenocarcinomas

Colorectal cancer (CRC) is one of the world's leading causes of cancer-related deaths; thus, it is important to detect it as early as possible. Obesity is thought to be linked to a large rise in the CRC incidence as a result of bad dietary choices, such as a high intake of animal fats. Fatty acid-binding proteins (FABPs) are a set of molecules that coordinate intracellular lipid responses and are highly associated with metabolism and inflammatory pathways. There are nine types of FABP genes that have been found in mammals, which are FABP1-7, FABP9, and FABP12. Each FABP gene has its own roles in different organs of the body; hence, each one has different expression levels in different cancers. The roles of FABP family genes in the development of CRC are still poorly understood. We used a bioinformatics approach to examine FABP family gene expression profiles using the Oncomine, GEPIA, PrognoScan, STRING, cBioPortal, MetaCore, and TIMER platforms. Results showed that the FABP6 messenger (m)RNA level is overexpressed in CRC cells compared to normal cells. The overexpression of FABP6 was found to be related to poor prognosis in CRC patients' overall survival. The immunohistochemical results in the Human Protein Atlas showed that FABP1 and FABP6 exhibited strong staining in CRC tissues. An enrichment analysis showed that high expression of FABP6 was significantly correlated with the role of microRNAs in cell proliferation in the development of CRC through the insulin-like growth factor (IGF) signaling pathway. FABP6 functions as an intracellular bile-acid transporter in the ileal epithelium. We looked at FABP6 expression in CRC since bile acids are important in the carcinogenesis of CRC. In conclusion, high FABP6 expression is expected to be a potential biomarker for detecting CRC at the early stage.

Expression of fatty acid-binding protein-4 in gastrointestinal stromal tumors and its significance for prognosis

Background

Fatty acid‐binding proteins (FABPs) have been found to be involved in tumorigenesis and development. However, the role of FABP4, a member of the FABPs, in GISTs (Gastrointestinal stromal tumors) remains unclear. This study aimed to investigate the expression of FABP4 and its prognostic value in GISTs.

Methods

FABP4 expression in 125 patients with GISTs was evaluated by immunohistochemical analysis of tissue microarrays. The relationship between FABP4 expression and clinicopathological features and prognosis of GISTs was analyzed.

Results

Multiple logistic regression analysis showed that expression of FABP4 correlated with tumor size and mitotic index. Furthermore, FABP4 level, tumor size, mitotic index, and high AFIP‐Miettinen risk were independent prognostic factors in GISTs. The Kaplan‐Meier survival curve showed that the 5‐year survival rate of patients with high‐FABP4 expression GISTs was lower.

Conclusions

These results suggested that high‐FABP4 expression might be a marker of malignant phenotype of GISTs and poor prognosis.

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.

Fatty acids and evolving roles of their proteins in neurological, cardiovascular disorders and cancers

The dysregulation of fat metabolism is involved in various disorders, including neurodegenerative, cardiovascular, and cancers. The uptake of long-chain fatty acids (LCFAs) with 14 or more carbons plays a pivotal role in cellular metabolic homeostasis. Therefore, the uptake and metabolism of LCFAs must constantly be in tune with the cellular, metabolic, and structural requirements of cells. Many metabolic diseases are thought to be driven by the abnormal flow of fatty acids either from the dietary origin and/or released from adipose stores. Cellular uptake and intracellular trafficking of fatty acids are facilitated ubiquitously with unique combinations of fatty acid transport proteins and cytoplasmic fatty acid-binding proteins in every tissue. Extensive data are emerging on the defective transporters and metabolism of LCFAs and their clinical implications. Uptake and metabolism of LCFAs are crucial for the brain's functional development and cardiovascular health and maintenance. In addition, data suggest fatty acid metabolic transporter can normalize activated inflammatory response by reprogramming lipid metabolism in cancers. Here we review the current understanding of how LCFAs and their proteins contribute to the pathophysiology of three crucial diseases and the mechanisms involved in the processes.

Molecular fingerprint of female bovine embryos produced in vitro with high competence to establish and maintain pregnancy†

The objective was to identify the transcriptomic profile of in vitro-derived embryos with high competence to establish and maintain gestation. Embryos produced with X-sorted sperm were cultured from day 5 to day 7 in serum-free medium containing 10 ng/ml recombinant bovine colony-stimulating factor 2 (CSF2) or vehicle. The CSF2 was administered because this molecule can increase blastocyst competence for survival after embryo transfer. Blastocysts were harvested on day 7 of culture and manually bisected. One demi-embryo from a single blastocyst was transferred into a synchronized recipient and the other half was used for RNA-seq analysis. Using P < 0.01 and a fold change >2-fold or <0.5 fold as cutoffs, there were 617 differentially expressed genes (DEG) between embryos that survived to day 30 of gestation vs those that did not, 470 DEG between embryos that survived to day 60 and those that did not, 432 DEG between embryos that maintained pregnancy from day 30 to day 60 vs those where pregnancy failed after day 30, and 635 DEG regulated by CSF2. Pathways and ontologies in which DEG were overrepresented included many related to cellular responses to stress and cell survival. It was concluded that gene expression in the blastocyst is different between embryos that are competent to establish and maintain pregnancy vs those that are not. The relationship between expression of genes related to cell stress and subsequent embryonic survival probably reflects cellular perturbations caused by embryonic development taking place in the artificial environment associated with cell culture.

The role of PPARγ in chemotherapy-evoked pain

Although millions of people are diagnosed with cancer each year, survival has never been greater thanks to early diagnosis and treatments. Powerful chemotherapeutic agents are highly toxic to cancer cells, but because they typically do not target cancer cells selectively, they are often toxic to other cells and produce a variety of side effects. In particular, many common chemotherapies damage the peripheral nervous system and produce neuropathy that includes a progressive degeneration of peripheral nerve fibers. Chemotherapy-induced peripheral neuropathy (CIPN) can affect all nerve fibers, but sensory neuropathies are the most common, initially affecting the distal extremities. Symptoms include impaired tactile sensitivity, tingling, numbness, paraesthesia, dysesthesia, and pain. Since neuropathic pain is difficult to manage, and because degenerated nerve fibers may not grow back and regain normal function, considerable research has focused on understanding how chemotherapy causes painful CIPN so it can be prevented. Due to the fact that both therapeutic and side effects of chemotherapy are primarily associated with the accumulation of reactive oxygen species (ROS) and oxidative stress, this review focuses on the activation of endogenous antioxidant pathways, especially PPARγ, in order to prevent the development of CIPN and associated pain. The use of synthetic and natural PPARγ agonists to prevent CIPN is discussed.

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.

The FABP12/PPARγ pathway promotes metastatic transformation by inducing epithelial-to-mesenchymal transition and lipid-derived energy production in prostate cancer cells

Early stage localized prostate cancer (PCa) has an excellent prognosis; however, patient survival drops dramatically when PCa metastasizes. The molecular mechanisms underlying PCa metastasis are complex and remain unclear. Here, we examine the role of a new member of the fatty acid‐binding protein (FABP) family, FABP12, in PCa progression. FABP12 is preferentially amplified and/or overexpressed in metastatic compared to primary tumors from both PCa patients and xenograft animal models. We show that FABP12 concurrently triggers metastatic phenotypes (induced epithelial‐to‐mesenchymal transition (EMT) leading to increased cell motility and invasion) and lipid bioenergetics (increased fatty acid uptake and accumulation, increased ATP production from fatty acid β‐oxidation) in PCa cells, supporting increased reliance on fatty acids for energy production. Mechanistically, we show that FABP12 is a driver of PPARγ activation which, in turn, regulates FABP12's role in lipid metabolism and PCa progression. Our results point to a novel role for a FABP‐PPAR pathway in promoting PCa metastasis through induction of EMT and lipid bioenergetics.

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.

Molecular docking and machine learning analysis of Abemaciclib in colon cancer

BACKGROUND

The main challenge in cancer research is the identification of different omic variables that present a prognostic value and personalised diagnosis for each tumour. The fact that the diagnosis is personalised opens the doors to the design and discovery of new specific treatments for each patient. In this context, this work offers new ways to reuse existing databases and work to create added value in research. Three published signatures with significante prognostic value in Colon Adenocarcinoma (COAD) were indentified. These signatures were combined in a new meta-signature and validated with main Machine Learning (ML) and conventional statistical techniques. In addition, a drug repurposing experiment was carried out through Molecular Docking (MD) methodology in order to identify new potential treatments in COAD.

RESULTS

The prognostic potential of the signature was validated by means of ML algorithms and differential gene expression analysis. The results obtained supported the possibility that this meta-signature could harbor genes of interest for the prognosis and treatment of COAD. We studied drug repurposing following a molecular docking (MD) analysis, where the different protein data bank (PDB) structures of the genes of the meta-signature (in total 155) were confronted with 81 anti-cancer drugs approved by the FDA. We observed four interactions of interest: GLTP - Nilotinib, PTPRN - Venetoclax, VEGFA - Venetoclax and FABP6 - Abemaciclib. The FABP6 gene and its role within different metabolic pathways were studied in tumour and normal tissue and we observed the capability of the FABP6 gene to be a therapeutic target. Our in silico results showed a significant specificity of the union of the protein products of the FABP6 gene as well as the known action of Abemaciclib as an inhibitor of the CDK4/6 protein and therefore, of the cell cycle.

CONCLUSIONS

The results of our ML and differential expression experiments have first shown the FABP6 gene as a possible new cancer biomarker due to its specificity in colonic tumour tissue and no expression in healthy adjacent tissue. Next, the MD analysis showed that the drug Abemaciclib characteristic affinity for the different protein structures of the FABP6 gene. Therefore, in silico experiments have shown a new opportunity that should be validated experimentally, thus helping to reduce the cost and speed of drug screening. For these reasons, we propose the validation of the drug Abemaciclib for the treatment of colon cancer.

Androgen Receptor Dependence

Androgens and the androgen receptor (AR) play crucial roles in the biology of normal and diseased prostate tissue, including prostate cancer (PCa). This dependence is evidenced by the use of androgen depletion therapy (ADT) as the primary treatment for locally advanced, metastatic, or relapsed PCa. This dependence is further evidenced by the various mechanisms employed by PCa cells to re-activate the AR to circumvent the growth-inhibitory effects of ADT. Re-activation of the AR during ADT is central to the disease evolving into the lethal castration resistant PCa (CRPC) phenotype, which is responsible for nearly all PCa mortality. Thus, understanding the regulation of AR and AR signaling is important for understanding the development and progression of PCa. This understanding provides the foundation for development of newer approaches for targeting CRPC therapeutically.

Docetaxel/cabazitaxel and fatty acid binding protein 5 inhibitors produce synergistic inhibition of prostate cancer growth

BACKGROUND

Prostate cancer (PCa) remains the second leading cause of cancer-related death among men. Taxanes, such as docetaxel and cabazitaxel are utilized in standard treatment regimens for chemotherapy naïve castration-resistant PCa. However, tumors often develop resistance to taxane chemotherapeutics, highlighting a need to identify additional therapeutic targets. Fatty acid-binding protein 5 (FABP5) is an intracellular lipid carrier whose expression is upregulated in metastatic PCa and increases cell growth, invasion, and tumor formation. Here, we assessed whether FABP5 inhibitors synergize with semi-synthetic taxanes to induce cytotoxicity in vitro and attenuate tumor growth in vivo.

METHODS

PC3, DU-145, and 22Rv1 PCa cells were incubated with FABP5 inhibitors Stony Brook fatty acid-binding protein inhibitor 102 (SBFI-102) or SBFI-103 in the presence or absence of docetaxel or cabazitaxel, and cytotoxicity was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide assay. Cytotoxicity of SBFI-102 and SBFI-103 was also evaluated in noncancerous cells. For the in vivo studies, PC3 cells were subcutaneously implanted into BALB/c nude mice, which were subsequently treated with FABP5 inhibitors, docetaxel, or a combination of both.

RESULTS

SBFI-102 and SBFI-103 produced cytotoxicity in the PCa cells. Coincubation of the PCa cells with FABP5 inhibitors and docetaxel or cabazitaxel produced synergistic cytotoxic effects in vitro. Treatment of mice with FABP5 inhibitors reduced tumor growth and a combination of FABP5 inhibitors with a submaximal dose of docetaxel reduced tumor growth to a larger extent than treatment with each drug alone.

CONCLUSIONS

FABP5 inhibitors increase the cytotoxic and tumor-suppressive effects of taxanes in PCa cells. The ability of these drugs to synergize could permit more efficacious antitumor activity while allowing for dosages of docetaxel or cabazitaxel to be lowered, potentially decreasing taxane-resistance.

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.

High expression of FABP4 and FABP6 in patients with colorectal cancer

Objective

To explore the relationship between FABP4 and FABP6 expression and the pathogenesis of colorectal cancer (CRC) and their potential as biomarkers in the diagnosis of CRC.

Methods

In total, 100 CRC patients and 100 controls were enrolled. The serum levels of FABP4 and FABP6 were detected by enzyme-linked immunosorbent assay (ELISA) before and 2 weeks after radical resection of CRC. The protein expressions of FABP4 and FABP6 were observed in colorectal tumor tissues and adjacent tissues by immunohistochemistry and western blot, respectively. The diagnostic performance of FABP4 and FABP6 in patients with CRC was evaluated by receiver operating characteristic (ROC) curve analysis.

Results

The serum levels of FABP4 and FABP6 in patients with CRC were higher than the levels in the controls before surgery (P < 0.001), and significantly decreased at 2 weeks after operation (P < 0.001). Immunohistochemistry showed that FABP4 and FABP6 were mainly distributed in the cytoplasm of human colorectal tumor tissues, and only a small amount distributed in adjacent tissues. Western blot revealed that the protein expressions of FABP4 and FABP6 were significantly higher in tumor tissues than in adjacent tissues (P < 0.001, P = 0.002, respectively). Tumors with high and low FABP4 and FABP6 expression have no significant correlation in tumor size, tumor site, distant organ and lymph node metastasis, histologic grade, lymphatic permeation, neurological invasion, vascular invasion, and Duke’s and TNM classification. Multivariate logistic regression analysis showed that FABP4 and FABP6 were independent risk factors for CRC (adjusted odds ratio 1.916; 95%CI 1.340–2.492; P < 0.001; adjusted odds ratio 2.162; 95%CI 1.046, 1.078); P < 0.001, respectively). In discriminating CRC from the normal control, the optimal sensitivity of FABP4 and FABP6 were 93.20% (95%CI 87.8–96.7) and 83.70% (95%CI 76.7–89.3), respectively, while the optimal specificity of FABP4 and FABP6 were 48.8% (95%CI 39.8–57.9) and 58.4% (95%CI 49.2–67.1), respectively. When combined detection of serum carcinoembryonic (CEA) and FABP4 and FABP6, the optimal sensitivity and specificity were 61.33% (95%CI 53.0–69.2) and 79.82% (95%CI 71.3–86.8), respectively.

Conclusion

Increased expression of FABP4 and FABP6 not only were strong risk factors for the development of CRC but could also represent a potential biomarker for CRC diagnosis in Chinese patients. Combined detection of CEA with FABP4 and FABP6 could improve the diagnostic efficacy of CRC.

Fatty acid-binding protein 5 (FABP5)-related signal transduction pathway in castration-resistant prostate cancer cells: a potential therapeutic target

In this short communication, a novel fatty acid-binding protein 5 (FABP5)-related signal transduction pathway in prostate cancer is reviewed. In castration-resistant prostate cancer (CRPC) cells, the FABP5-related signal transduction pathway plays an important role during transformation of the cancer cells from androgen-dependent state to androgen-independent state. The detailed route of this signal transduction pathway can be described as follows: when FABP5 expression is increased as the increasing malignancy, excessive amounts of fatty acids from intra- and extra-cellular sources are transported into the nucleus of the cancer cells where they act as signalling molecules to stimulate their nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ). The phosphorylated or biologically activated PPARγ then modulates the expression of its downstream target regulatory genes to trigger a series of molecular events that eventually lead to enhanced tumour expansion and aggressiveness caused by an overgrowth of the cancer cells with a reduced apoptosis and an increased angiogenesis. Suppressing the FABP5-related pathway via RNA interference against FABP5 has produced a 63-fold reduction in the average size of the tumours developed from CRPC cells in nude mice, a seven-fold reduction of tumour incidence, and a 100% reduction of metastasis rate. Experimental treatments of CRPC with novel FABP5 inhibitors have successfully inhibited the malignant progression of CRPC cells both in vitro and in nude mouse. These studies suggest that FABP5-related signal transduction pathway is a novel target for therapeutic intervention of CRPC cells.

Inactivated FABP5 suppresses malignant progression of prostate cancer cells by inhibiting the activation of nuclear fatty acid receptor PPARγ

Previous study has suggested that the FABP5-PPARγ-signalling transduction pathway gradually replaces the androgen receptor activated pathway in promoting malignant progression of castration-resistant prostate cancer (CRPC) cells. To interfere with this newly discovered FABP5-related signalling pathway, we have produced a highly efficient recombinant FABP5 inhibitor, named dmrFABP5. Treatment with dmrFABP5 significantly supressed the proliferation, migration, invasion and colony formation of the highly malignant prostate cancer cells PC3-M in vitro. To test dmrFABP5's suppressive effect in CRPC, the human PC3-M cells were implanted orthotopically into the prostate gland of immunosuppressed mice to produce tumours. These mice were then treated with dmrFABP5 and produced a highly significant reduction of 100% in metastatic rate and a highly significant reduction of 13-fold in the average size of primary tumours. Immunocytochemial staining showed that the staining intensity of dmrFABP5 treated tumours was reduced by 67%. When tested in vitro, dmrFABP5 suppressed the cancer cells by blocking fatty acid stimulation of PPARγ, and thereby prevented it activating down-stream cancer-promoting or inhibiting cancer-suppressing genes. Our results show that the FABP5 inhibitor dmrFABP5 is a novel molecule for treatment of experimental CRPC and its inhibitory effect is much greater than that produced by SB-FI-26 reported in our previous work.

Differentially expressed proteins in positive versus negative HNSCC lymph nodes

Background

Lymph node metastasis is one of the most important prognostic factors in head and neck squamous cell carcinomas (HNSCCs) and critical for delineating their treatment. However, clinical and histological criteria for the diagnosis of nodal status remain limited. In the present study, we aimed to characterize the proteomic profile of lymph node metastasis from HNSCC patients.

Methods

In the present study, we used one- and two-dimensional electrophoresis and mass spectrometry analysis to characterize the proteomic profile of lymph node metastasis from HNSCC.

Results

Comparison of metastatic and non-metastatic lymph nodes showed 52 differentially expressed proteins associated with neoplastic development and progression. The results reinforced the idea that tumors from different anatomical subsites have dissimilar behaviors, which may be influenced by micro-environmental factor including the lymphatic network. The expression pattern of heat shock proteins and glycolytic enzymes also suggested an effect of the lymph node environment in controlling tumor growth or in metabolic reprogramming of the metastatic cell. Our study, for the first time, provided direct evidence of annexin A1 overexpression in lymph node metastasis of head and neck cancer, adding information that may be useful for diagnosing aggressive disease.

Conclusions

In brief, this study contributed to our understanding of the metastatic phenotype of HNSCC and provided potential targets for diagnostic in this group of carcinomas.

Electronic supplementary material

The online version of this article (10.1186/s12920-018-0382-6) contains supplementary material, which is available to authorized users.

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

Epidermal or cutaneous fatty acid-binding protein is an intracellular lipid-binding protein, also known as FABP5, and its expression level is closely related to cancer cell proliferation and metastatic activities in various types of carcinoma. However, the molecular mechanisms of FABP5 in cancer cell proliferation and its other functions have remained unclear. In the present study, we have clearly revealed that FABP5 activated expression of metabolic genes (ATP5B, LCHAD, ACO2, FH and MFN2) via a novel signaling pathway in an ERRα (estrogen-related receptor α)-dependent manner in prostate cancer cell lines. To clarify the novel function of FABP5, we examined the activation mechanisms of the ERRα target genes via FABP5. A direct protein-protein interaction between FABP5 and ERRα was demonstrated by immunoprecipitation and GST pull-down assays. We have clearly revealed that FABP5 interacted directly with transcriptional complex containing ERRα and its co-activator PGC-1β to increase expression of the ERRα target genes. In addition, we have shown that FABP5 knockdown induced high energy stress leading to induction of apoptosis and cell cycle arrest via AMPK-FOXO3A signaling pathway in prostate cancer cells, suggesting that FABP5 plays an important role in cellular energy status directing metabolic adaptation to support cellular proliferation and survival.

RNA sequencing reveals upregulation of a transcriptomic program associated with stemness in metastatic prostate cancer cells selected for taxane resistance

Patients with metastatic castration-resistant prostate cancer (mCRPC) develop resistance to conventional therapies including docetaxel (DTX). Identifying molecular pathways underlying DTX resistance is critical for developing novel combinatorial therapies to prevent or reverse this resistance. To identify transcriptomic signatures associated with acquisition of chemoresistance we profiled gene expression in DTX-sensitive and -resistant mCRPC cells using RNA sequencing (RNA-seq). PC3 and DU145 cells were selected for DTX resistance and this phenotype was validated by immunoblotting using DTX resistance markers (e.g. clusterin, ABCB1/P-gp, and LEDGF/p75). Overlapping genes differentially regulated in the DTX-sensitive and -resistant cells were ranked by Gene Set Enrichment Analysis (GSEA) and validated to correlate transcript with protein expression. GSEA revealed that genes associated with cancer stem cells (CSC) (e.g., NES, TSPAN8, DPPP, DNAJC12, and MYC) were highly ranked and comprised 70% of the top 25 genes differentially upregulated in the DTX-resistant cells. Established markers of epithelial-to-mesenchymal transition (EMT) and CSCs were used to evaluate the stemness of adherent DTX-resistant cells (2D cultures) and tumorspheres (3D cultures). Increased formation and frequency of cells expressing CSC markers were detected in DTX-resistant cells. DU145-DR cells showed a 2-fold increase in tumorsphere formation and increased DTX resistance compared to DU145-DR 2D cultures. These results demonstrate the induction of a transcriptomic program associated with stemness in mCRPC cells selected for DTX resistance, and strengthen the emerging body of evidence implicating CSCs in this process. In addition, they provide additional candidate genes and molecular pathways for potential therapeutic targeting to overcome DTX resistance.

Lipid pathway deregulation in advanced prostate cancer

The link between prostate cancer (PC) development and lipid metabolism is well established, with AR intimately involved in a number of lipogenic processes involving SREBP1, PPARG, FASN, ACC, ACLY and SCD1. Recently, there is growing evidence implicating the role of obesity and peri-prostatic adipose tissue (PPAT) in PC aggressiveness and related mortality, suggesting the importance of lipid pathways in both localised and disseminated disease. A number of promising agents are in development to target the lipogenic axis in PC, and the likelihood is that these agents will form part of combination drug strategies, with targeting of multiple metabolic pathways (e.g. FASN and CPT1), or in combination with AR pathway inhibitors (SCD1 and AR).

The role of peroxisome proliferator-activated receptor gamma in prostate cancer

Despite great progress in the detection and treatment of prostate cancer, this disease remains an incredible health and economic burden. Although androgen receptor (AR) signaling plays a key role in the development and progression of prostate cancer, aberrations in other molecular pathways also contribute to the disease, making it essential to identify and develop drugs against novel targets, both for the prevention and treatment of prostate cancer. One promising target is the peroxisome proliferator-activated receptor gamma (PPARγ) protein. PPARγ was originally thought to act as a tumor suppressor in prostate cells because agonist ligands inhibited the growth of prostate cancer cells; however, additional studies found that PPARγ agonists inhibit cell growth independent of PPARγ. Furthermore, PPARγ expression increases with cancer grade/stage, which would suggest that it is not a tumor suppressor but instead that PPARγ activity may play a role in prostate cancer development and/or progression. Indeed, two new studies, taking vastly different, unbiased approaches, have identified PPARγ as a target in prostate cancer and suggest that PPARγ inhibition might be useful in prostate cancer prevention and treatment. These findings could lead to a new therapeutic weapon in the fight against prostate cancer.

Inhibitor SBFI26 suppresses the malignant progression of castration-resistant PC3-M cells by competitively binding to oncogenic FABP5

Castration resistant-prostate cancer is largely impervious to feather hormonal therapy and hence the outlook for patients is grim. Here we use an approach to attach the recently discovered Achilles heel. The experimental treatment established in this study is based on the recent discovery that it is the FABP5-PPARγ-VEGF signalling axis, rather than the androgen receptor pathway, played a dominant role in promoting the malignant progression of castration resistant prostate cancer cells. Treatments have been established in mice by suppressing the biological activity of FABP5 using a chemical inhibitor SBFI26. The inhibitor significantly suppressed the proliferation, migration, invasiveness and colony formation of PC3-M cells in vitro. It also produced a highly significant suppression of both the metastases and the primary tumours developed from cancer cells implanted orthotopically into the prostate glands of the mice. The inhibitor SBFI26 interferes with the FABP5-PPARγ- signalling pathway at the initial stage of the signal transduction by binding competitively to FABP5 to inhibit cellular fatty acid uptake. This avoids the fatty-acid stimulation of PPARγ and prevents it activating the down-stream regulated cancer-promoting genes. This entirely novel experimental approach to treating castration- resistant prostate cancer is completely different from current treatments that are based on androgen-blockade therapy.

The increased expression of fatty acid-binding protein 9 in prostate cancer and its prognostic significance

In contrast to numerous studies conducted to investigate the crucial role of fatty acid binding protein 5 (FABP5) in prostate cancer, investigations on the possible involvement of other FABPs are rare. Here we first measured the mRNA levels of 10 FABPs in benign and malignant prostate cell lines and identified the differentially expressed FABP6 and FABP9 mRNAs whose levels in all malignant cell lines were higher than those in the benign cells. Thereafter we assessed the expression status of FABP6 and FABP9 in both prostate cell lines and in human tissues. FABP6 protein was overexpressed only in 1 of the 5 malignant cell lines and its immunostaining intensities were not significantly different between benign and malignant prostate tissues. In contrast, FABP9 protein was highly expressed in highly malignant cell lines PC-3 and PC3-M, but its level in the benign PNT-2 and other malignant cell lines was not detectable. When analysed in an archival set of human prostate tissues, immunohistochemical staining intensity for FABP9 was significantly higher in carcinomas than in benign cases and the increase in FABP9 was significantly correlated with reduced patient survival times. Moreover, the increased level of staining for FABP9 was significantly associated with the increased joint Gleason scores (GS) and androgen receptor index (AR). Suppression of FABP9 expression in highly malignant PC3-M cells inhibited their invasive potential. Our results suggest that FABP9 is a valuable prognostic marker to predict the outcomes of prostate cancer patients, perhaps by playing an important role in prostate cancer cell invasion.

Antiangiogenic and tumour inhibitory effects of downregulating tumour endothelial FABP4

Fatty acid binding protein 4 (FABP4) is a fatty acid chaperone, which is induced during adipocyte differentiation. Previously we have shown that FABP4 in endothelial cells is induced by the NOTCH1 signalling pathway, the latter of which is involved in mechanisms of resistance to antiangiogenic tumour therapy. Here, we investigated the role of FABP4 in endothelial fatty acid metabolism and tumour angiogenesis. We analysed the effect of transient FABP4 knockdown in human umbilical vein endothelial cells on fatty acid metabolism, viability and angiogenesis. Through therapeutic delivery of siRNA targeting mouse FABP4, we investigated the effect of endothelial FABP4 knockdown on tumour growth and blood vessel formation. In vitro, siRNA-mediated FABP4 knockdown in endothelial cells led to a marked increase of endothelial fatty acid oxidation, an increase of reactive oxygen species and decreased angiogenesis. In vivo, we found that increased NOTCH1 signalling in tumour xenografts led to increased expression of endothelial FABP4 that decreased when NOTCH1 and VEGFA inhibitors were used in combination. Angiogenesis, growth and metastasis in ovarian tumour xenografts were markedly inhibited by therapeutic siRNA delivery targeting mouse endothelial FABP4. Therapeutic targeting of endothelial FABP4 by siRNA in vivo has antiangiogenic and antitumour effects with minimal toxicity and should be investigated further.

Fatty acid activated PPARγ promotes tumorigenicity of prostate cancer cells by up regulating VEGF via PPAR responsive elements of the promoter

In previous work, it is suggested that the excessive amount of fatty acids transported by FABP5 may facilitate the malignant progression of prostate cancer cells through a FABP5-PPARγ-VEGF signal transduction axis to increase angiogenesis. To further functionally characterise the FABP5-PPARγ-VEGF signal transduction pathway, we have, in this work, investigated the molecular mechanisms involved in its tumorigenicity promoting role in prostate cancer. Suppression of PPARγ in highly malignant prostate cancer cells produced a significant reduction (up to 53%) in their proliferation rate, invasiveness (up to 89%) and anchorage-independent growth (up to 94%) in vitro. Knockdown of PPARγ gene in PC3-M cells by siRNA significantly reduced the average size of tumours formed in nude mice by 99% and tumour incidence by 90%, and significantly prolonged the latent period by 3.5 fold. Results in this study combined with some previous results suggested that FABP5 promoted VEGF expression and angiogenesis through PPARγ which was activated by fatty acids transported by FABP5. Further investigations showed that PPARγ up-regulated VEGF expression through acting with the PPAR-responsive elements in the promoter region of VEGF gene in prostate cancer cells. Although androgen can modulate VEGF expression through Sp1/Sp3 binding site on VEGF promoter in androgen-dependent prostate cancer cells, this route, disappeared as the cells gradually lost their androgen dependency; was replaced by the FABP5-PPARγ-VEGF signalling pathway. These results suggested that the FABP5-PPARγ-VEGF signal transduction axis, rather than androgen modulated route, may be a more important novel therapeutic target for angiogenesis-suppression treatment of castration resistant prostate cancer.

Proteomic Upregulation of Fatty Acid Synthase and Fatty Acid Binding Protein 5 and Identification of Cancer- and Race-Specific Pathway Associations in Human Prostate Cancer Tissues

Protein profiling studies of prostate cancer have been widely used to characterize molecular differences between diseased and non-diseased tissues. When combined with pathway analysis, profiling approaches are able to identify molecular mechanisms of prostate cancer, group patients by cancer subtype, and predict prognosis. This strategy can also be implemented to study prostate cancer in very specific populations, such as African Americans who have higher rates of prostate cancer incidence and mortality than other racial groups in the United States. In this study, age-, stage-, and Gleason score-matched prostate tumor specimen from African American and Caucasian American men, along with non-malignant adjacent prostate tissue from these same patients, were compared. Protein expression changes and altered pathway associations were identified in prostate cancer generally and in African American prostate cancer specifically. In comparing tumor to non-malignant samples, 45 proteins were significantly cancer-associated and 3 proteins were significantly downregulated in tumor samples. Notably, fatty acid synthase (FASN) and epidermal fatty acid-binding protein (FABP5) were upregulated in human prostate cancer tissues, consistent with their known functions in prostate cancer progression. Aldehyde dehydrogenase family 1 member A3 (ALDH1A3) was also upregulated in tumor samples. The Metastasis Associated Protein 3 (MTA3) pathway was significantly enriched in tumor samples compared to non-malignant samples. While the current experiment was unable to detect statistically significant differences in protein expression between African American and Caucasian American samples, differences in overrepresentation and pathway enrichment were found. Structural components (Cytoskeletal Proteins and Extracellular Matrix Protein protein classes, and Biological Adhesion Gene Ontology (GO) annotation) were overrepresented in African American but not Caucasian American tumors. Additionally, 5 pathways were enriched in African American prostate tumors: the Small Cell Lung Cancer, Platelet-Amyloid Precursor Protein, Agrin, Neuroactive Ligand-Receptor Interaction, and Intrinsic pathways. The protein components of these pathways were either basement membrane proteins or coagulation proteins.

High expression of Fatty Acid-Binding Protein 5 promotes cell growth and metastatic potential of colorectal cancer cells

Fatty acid‐binding proteins (FABPs) are responsible for binding and storing hydrophobic ligands such as long‐chain fatty acids, and for transporting these ligands to the appropriate compartments within the cell. The present study demonstrates that the FABP5 gene is upregulated in colorectal cancer cells compared to normal colon cells in a manner that correlates with disease stage and that FABP5 significantly promotes colorectal cancer cell growth and metastatic potential. Thus, FABP5 might be a promising prognostic or therapeutic biomarker candidate in human colorectal cancer.

The cancer-promoting gene fatty acid-binding protein 5 (FABP5) is epigenetically regulated during human prostate carcinogenesis

The DNA methylation status of CpG islands in the FABP5 promoter is critical for its expression. Epigenetic regulation of FABP5 gene expression plays an important role during human prostate carcinogenesis, along with up-regulation of c-Myc and Sp1.

Obesity and cancer progression: is there a role of fatty acid metabolism?

Currently, there is renewed interest in elucidating the metabolic characteristics of cancer and how these characteristics may be exploited as therapeutic targets. Much attention has centered on glucose, glutamine and de novo lipogenesis, yet the metabolism of fatty acids that arise from extracellular, as well as intracellular, stores as triacylglycerol has received much less attention. This review focuses on the key pathways of fatty acid metabolism, including uptake, esterification, lipolysis, and mitochondrial oxidation, and how the regulators of these pathways are altered in cancer. Additionally, we discuss the potential link that fatty acid metabolism may serve between obesity and changes in cancer progression.