Effect of FABP5 gene silencing on the proliferation, apoptosis and invasion of human gastric SGC-7901 cancer cells

Concomitant decrease of E- and A-FABP expression predicts worse survival in urothelial bladder cancer patients

Non-muscle invasive bladder cancers (NMIBC) pTa-pT1 are depicted by a high risk of recurrence and/or progression with an unpredictable clinical evolution. Our aim was to identify, from the original resection specimen, tumors that will progress to better manage patients. We previously showed that A-FABP (Adipocyte- Fatty Acid Binding Protein) loss predicted NMIBC progression. Here we determined by immunohistochemistry the prognostic value of E-FABP (Epidermal-Fatty Acid Binding Protein) expression in 210 tumors (80 pTa, 75 pT1, 55 pT2-T4). Thus, E-FABP low expression was correlated with a high grade/stage, the presence of metastatic lymph nodes, and visceral metastases (p < 0.001). Unlike A-FABP in NMIBC, E-FABP low expression was not associated with RFS or PFS in Kaplan-Meier analysis. But patients of the overall cohort with a high E-FABP expression had a longer mOS (53.8 months vs. 29.3 months, p = 0.029). The immunohistochemical analysis on the same NMIBC tissue sections revealed that when A-FABP is absent, a high E-FABP expression is detected. E-FABP could compensate A-FABP loss. Interestingly, patients, whose original tumor presents both low E-FABP and negative A-FABP, had the worse survival, those maintaining the expression of both markers had better survival. To conclude, the combined evaluation of A- and E-FABP expression allowed to stratify patients with urothelial carcinoma for optimizing treatment and follow-up.

SBFI26 induces triple-negative breast cancer cells ferroptosis via lipid peroxidation

SBFI26, an inhibitor of FABP5, has been shown to suppress the proliferation and metastasis of tumour cells. However, the underlying mechanism by which SBFI26 induces ferroptosis in breast cancer cells remains largely unknown. Three breast cancer cell lines were treated with SBFI26 and CCK-8 assessed cytotoxicity. Transcriptome was performed on the Illumina platform and verified by qPCR. Western blot evaluated protein levels. Malondialdehyde (MDA), total superoxide dismutase (T-SOD), Fe, glutathione (GSH) and oxidized glutathione (GSSG) were measured. SBFI26 induced cell death time- and dose-dependent, with a more significant inhibitory effect on MDA-MB-231 cells. Fer-1, GSH and Vitamin C attenuated the effects but not erastin. RNA-Seq analysis revealed that SBFI26 treatment significantly enriched differentially expressed genes related to ferroptosis. Furthermore, SBFI26 increased intracellular MDA, iron ion, and GSSG levels while decreasing T-SOD, total glutathione (T-GSH), and GSH levels.SBFI26 dose-dependently up-regulates the expression of HMOX1 and ALOX12 at both gene and protein levels, promoting ferroptosis. Similarly, it significantly increases the expression of SAT1, ALOX5, ALOX15, ALOXE3 and CHAC1 that, promoting ferroptosis while downregulating the NFE2L2 gene and protein that inhibit ferroptosis. SBFI26 leads to cellular accumulation of fatty acids, which triggers excess ferrous ions and subsequent lipid peroxidation for inducing ferroptosis.

FABP5 regulates lipid metabolism to facilitate pancreatic neuroendocrine neoplasms progression via FASN mediated Wnt/β-catenin pathway

Pancreatic neuroendocrine neoplasms (pNENs) are among the most frequently occurring neuroendocrine neoplasms (NENs) and require targeted therapy. High levels of fatty acid binding protein 5 (FABP5) are involved in tumor progression, but its role in pNENs remains unclear. We investigated the mRNA and protein levels of FABP5 in pNEN tissues and cell lines and found them to be upregulated. We evaluated changes in cell proliferation using CCK-8, colony formation, and 5-ethynyl-2'-deoxyuridine assays and examined the effects on cell migration and invasion using transwell assays. We found that knockdown of FABP5 suppressed the proliferation, migration, and invasion of pNEN cell lines, while overexpression of FABP5 had the opposite effect. Co-immunoprecipitation experiments were performed to clarify the interaction between FABP5 and fatty acid synthase (FASN). We further showed that FABP5 regulates the expression of FASN via the ubiquitin proteasome pathway and both proteins facilitate the progression of pNENs. Our study demonstrated that FABP5 acts as an oncogene by promoting lipid droplet deposition and activating the WNT/β-catenin signaling pathway. Moreover, the carcinogenic effects of FABP5 can be reversed by orlistat, providing a novel therapeutic intervention option.

The Multifunctional Family of Mammalian Fatty Acid-Binding Proteins

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

Aberrant DNA methylation-mediated NF-κB/fatty acid-binding protein 5 (FABP5) feed-forward loop promotes malignancy of colorectal cancer cells

Fatty acid-binding proteins (FABPs) are intracellular lipid-binding proteins that play roles in fatty acid transport and the regulation of gene expression. Dysregulated FABP expression and/or activity have been associated with cancer pathogenesis; in particular, epidermal-type FABP (FABP5) is upregulated in many types of cancer. However, the mechanisms regulating FABP5 expression and its involvement in cancer remain largely unknown. Here, we examined the regulation of FABP5 gene expression in non-metastatic and metastatic human colorectal cancer (CRC) cells. We found that FABP5 expression was upregulated in metastatic compared with non-metastatic CRC cells as well as in human CRC tissues compared with adjacent normal tissue. Analysis of the DNA methylation status of the FABP5 promoter showed that hypomethylation correlated with the malignant potential of the CRC cell lines. Moreover, FABP5 promoter hypomethylation also correlated with the expression pattern of splice variants of the DNA methyltransferase DNMT3B. ChIP assays and luciferase reporter assays demonstrated that the transcription factor nuclear factor-kappa B (NF-κB) was involved in regulating FABP5 expression. FABP5 expression could be upregulated in metastatic CRC cells by sequential promotion of DNA demethylation followed by activation of NF-κB. We also found that upregulated FABP5 in turn controlled NF-κB activity through IL-8 production. Collectively, these findings suggest the existence of a DNA methylation-dependent NF-κB /FABP5 positive feed-forward loop that may lead to constitutive activation of NF-κB signaling pathway and play a crucial role in CRC progression.

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.

Naturally-occurring carboxylic acids from traditional antidiabetic plants as potential pancreatic islet FABP3 inhibitors. A molecular docking-aided study

The antidiabetic action of traditional plants is mostly attributed to their antioxidant and anti-inflammatory properties. These plants are still having some secrets, making them an attractive source that allows for investigating new drugs or uncovering precise pharmacologic antidiabetic functions of their constituents. In diabetes, which is a lipid disease, long-term exposure of pancreatic islet beta cells to fatty acids (FAs) increases basal insulin release, reduces glucose-stimulated insulin secretion, causes islet beta cell inflammation, failure and apoptosis. Pancreatic islet beta cells express fatty acid binding protein 3 (FABP3) that receives long-chain FAs and traffics them throughout different cellular compartments to be metabolized and render their effects. Inhibition of this FABP3 may retard FA metabolism and protect islet beta cells. Since FAs interact with FABPs by their carboxylic group, some traditionally-known antidiabetic plants were reviewed in the present study, searching for their components that have common features of FABP ligands, namely carboxylic group and hydrophobic tail. Many of these carboxylic acids were computationally introduced into the ligand-binding pocket of FABP3 and some of them exhibited FABP3 ligand possibilities. Among others, the naturally occurring ferulic, cleomaldeic, caffeic, sinapic, hydroxycinnamic, 4-p-coumaroylquinic, quinoline-2-carboxylic, chlorogenic, 6-hydroxykynurenic, and rosmarinic acids in many plants are promising candidates for being FABP3-specific inhibitors. The study shed light on repurposing these phyto-carboxylic acids to function as FABP inhibitors. However, more in-depth biological and pharmacological studies to broaden the understanding of this function are needed.

The Role of Lipid Metabolism in Gastric Cancer

Gastric cancer has been one of the most common cancers worldwide with extensive metastasis and high mortality. Chemotherapy has been found as a main treatment for metastatic gastric cancer, whereas drug resistance limits the effectiveness of chemotherapy and leads to treatment failure. Chemotherapy resistance in gastric cancer has a complex and multifactorial mechanism, among which lipid metabolism plays a vital role. Increased synthesis of new lipids or uptake of exogenous lipids can facilitate the rapid growth of cancer cells and tumor formation. Lipids form the structural basis of biofilms while serving as signal molecules and energy sources. It is noteworthy that lipid metabolism is capable of inducing drug resistance in gastric cancer cells by reshaping the tumor micro-environment. In this study, new mechanisms of lipid metabolism in gastric cancer and the metabolic pathways correlated with chemotherapy resistance are reviewed. In particular, we discuss the effects of lipid metabolism on autophagy, biomarkers treatment and drug resistance in gastric cancer from the perspective of lipid metabolism. In brief, new insights can be gained into the development of promising therapies through an in-depth investigation of the mechanism of lipid metabolism reprogramming and resensitization to chemotherapy in gastric cancer cells, and scientific treatment can be provided by applying lipid-key enzyme inhibitors as cancer chemical sensitizers in clinical settings.

Key Molecules of Fatty Acid Metabolism in Gastric Cancer

Fatty acid metabolism is closely linked to the progression of gastric cancer (GC), a very aggressive and life-threatening tumor. This study examines linked molecules, such as Sterol Regulatory Element-Binding Protein 1 (SREBP1), ATP Citrate Lyase (ACLY), Acetyl-CoA Synthases (ACSs), Acetyl-CoA Carboxylase (ACC), Fatty Acid Synthase (FASN), Stearoyl-CoA Desaturase 1 (SCD1), CD36, Fatty Acid Binding Proteins (FABPs), and Carnitine palmitoyltransferase 1 (CPT1), as well as their latest studies and findings in gastric cancer to unveil its core mechanism. The major enzymes of fatty acid de novo synthesis are ACLY, ACSs, ACC, FASN, and SCD1, while SREBP1 is the upstream molecule of fatty acid anabolism. Fatty acid absorption is mediated by CD36 and FABPs, and fatty acid catabolism is mediated by CPT1. If at all possible, we will discover novel links between fatty acid metabolism and a prospective gastric cancer target.

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.

Exploration of prognostic index based on immune-related genes in patients with liver hepatocellular carcinoma

The present study aimed to screen the immune-related genes (IRGs) in patients with liver hepatocellular carcinoma (LIHC) and construct a synthetic index for indicating the prognostic outcomes. The bioinformatic analysis was performed on the data of 374 cancer tissues and 50 normal tissues, which were downloaded from TCGA database. We observed that 17 differentially expressed IRGs were significantly associated with survival in LIHC patients. These LIHC-specific IRGs were validated with function analysis and molecular characteristics. Cox analysis was applied for constructing a RiskScore for predicting the survival. The RiskScore involved six IRGs and corresponding coefficients, which was calculated with the following formula: RiskScore = [Expression level of FABP5 *(0.064)] + [Expression level of TRAF3 * (0.198)] + [Expression level of CSPG5 * (0.416)] + [Expression level of IL17D * (0.197)] + [Expression level of STC2 * (0.036)] + [Expression level of BRD8 * (0.140)]. The RiskScore was positively associated with the poor survival, which was verified with the dataset from ICGC database. Further analysis revealed that the RiskScore was independent of any other clinical feature, while it was linked with the infiltration levels of six types of immune cells. Our study reported the survival-associated IRGs in LIHC and then constructed IRGs-based RiskScore as prognostic indicator for screening patients with high risk of short survival. Both the screened IRGs and IRGs-based RiskScore were clinically significant, which may be informative for promoting the individualized immunotherapy against LIHC.

FABP5 enhances malignancies of lower-grade gliomas via canonical activation of NF-κB signaling

Low‐grade gliomas (LGGs) are grade III gliomas based on the WHO classification with significant genetic heterogeneity and clinical properties. Traditional histological classification of gliomas has been challenged by the improvement of molecular stratification; however, the reproducibility and diagnostic accuracy of LGGs classification still remain poor. Herein, we identified fatty acid binding protein 5 (FABP5) as one of the most enriched genes in malignant LGGs and elevated FABP5 revealed severe outcomes in LGGs. Functionally, lentiviral suppression of FABP5 reduced malignant characters including proliferation, cloning formation, immigration, invasion and TMZ resistance, contrarily, the malignancies of LGGs were enhanced by exogenous overexpression of FABP5. Mechanistically, epithelial‐mesenchymal transition (EMT) was correlated to FABP5 expression in LGGs and tumour necrosis factor α (TNFα)‐dependent NF‐κB signalling was involved in this process. Furthermore, FABP5 induced phosphorylation of inhibitor of nuclear factor kappa‐B kinase α (IKKα) thus activated nuclear factor kappa‐B (NF‐κB) signalling. Taken together, our study indicated that FABP5 enhances malignancies of LGGs through canonical activation of NF‐κB signalling, which could be used as individualized prognostic biomarker and potential therapeutic target of LGGs.

Berberine Suppressed Tumor Growth through Regulating Fatty Acid Metabolism and Triggering Cell Apoptosis via Targeting FABPs

Aim

To further investigate the mechanism behind the antitumor properties of berberine regarding lipid metabolism.

Methods

Cell viability, proliferation, and apoptosis assays were performed to determine the antigrowth effects of berberine in vitro. Ectopic xenograft models in Balb/c nude mice were established to determine the antitumor effects of berberine in vivo.

Results

Berberine inhibited cell viability and proliferation of MGC803 human gastric cancer cell lines in a time- and dose-dependent manner. Berberine induced apoptosis of MGC803 and increased the apoptotic rate with higher doses. Berberine induced the accumulation of fatty acid of MGC803 and suppressed the protein expression of FABPs and PPARα. The FABP inhibitor BMS309403 recapitulated the effects of berberine on MGC803 cells. In the xenograft model, berberine significantly decreased the tumor volume and tumor weight and induced apoptosis in tumor tissues. Berberine significantly elevated the fatty acid content and inhibited the expression of FABPs and PPARα in the MGC803 xenograft models.

Conclusion

Berberine exerted anticancer effects on human gastric cancer both in vitro and in vivo by inducing apoptosis, which was due to the reduced protein expression of FABPs and the accumulation of fatty acid.

The Damaging Effects of Pedunsaponin A on Pomacea canaliculata Hemocytes

Pomacea canaliculata hemocytes are the main functional cells in the immune defense system, and hemocyte destruction disrupts the immune response mechanism of P. canaliculata, resulting in abnormal growth, development, reproduction, and even death. Our previous study found that Pedunsaponin A significantly affects P. canaliculata hemocyte structure. This study further investigated the damaging effects of Pedunsaponin A on P. canaliculata hemocytes. The cell mortality rate results showed that the hemocyte mortality was significantly increased after treatment with Pedunsaponin A, and the mortality rate exhibited a significant positive correlation with treatment time and dose. The membrane potential results showed that the cell membranes of P. canaliculata hemocytes exhibited time-dependent membrane depolarization after 40 mg/L Pedunsaponin A treatment. At 36 h, the cell depolarization rate in the Pedunsaponin A treatment group was 41.43%, which was significantly greater than the control group (6.24%). The cytoskeleton results showed that Pedunsaponin A led to disordered and dispersed arrangement of microfilaments and changes in the cytoskeletal structure. The apoptosis and cell cycle results showed that Pedunsaponin A induced apoptosis and influenced the cell cycle to some extent. These results showed that the cell membrane and cytoskeleton of P. canaliculata hemocytes were damaged after treatment with Pedunsaponin A, which led to an increase in cell mortality, dysfunction, cell cycle abnormalities and apoptosis. This study provides a foundation for further identification of the site of Pedunsaponin A activity on hemocytes.

FABP5 regulates the proliferation of clear cell renal cell carcinoma cells via the PI3K/AKT signaling pathway

Clear cell renal cell carcinoma (ccRCC) has been associated with one of the highest mortality rates among all cancers. Fatty acid binding proteins (FABPs) are 14‑15 kDa proteins that are highly abundant in the cytosol of most tissues. FABP5, a member of the FABP family, has been observed to promote tumor cell growth in numerous cancer types. In order to investigate the function of FABP5 in ccRCC cells in the present study, RNA sequencing data from The Cancer Genome Atlas were analyzed to determine the expression levels of FABP5 in ccRCC patient samples. Survival and Cox regression analyses were performed to measure the association between FABP5 expression and clinicopathological features of patients with ccRCC. Subsequent in vitro experiments downregulated or overexpressed FABP5 in Caki‑1 and 786O ccRCC cells using lentiviral vectors to evaluate cell proliferation ability, and a xenograft transplantation model was established to examine the effect of FABP5 on tumorigenesis in vivo. The results demonstrated that FABP5 expression was significantly upregulated in samples from patients with ccRCC when compared with normal tissue samples. High FABP5 expression was also significantly correlated with tumor and metastasis classifications and predicted poor survival in patients with ccRCC. In ccRCC cells, silencing of FABP5 significantly inhibited cell proliferation, while overexpression of FABP5 promoted cell proliferation when compared to the respective controls. In addition, treatment with the phosphatidylinositol‑4,5‑bisphosphate 3‑kinase (PI3K)/AKT inhibitor, LY294002, attenuated the pro‑proliferative effects of exogenous FABP5 expression in Caki‑1 and 786O cells. This indicated that the PI3K/AKT signaling pathway may be partially involved in the FABP5‑mediated increase in ccRCC cell proliferation. Furthermore, FABP5 was observed to regulate tumor growth in nude mice in vivo. In conclusion, the results of the present study suggest that FABP5 may exert a pro‑proliferative role in ccRCC and may be associated with malignant progression and tumorigenesis.

Diverse roles of fatty acid binding proteins (FABPs) in development and pathogenesis of cancers

One of the most importantly involved pathways in cancer development is fatty-acid signaling pathway. Synthesized lipids as energetic sources are consumed by cancer cells for proliferation, growth, survival, invasion and angiogenesis. Fatty acids as signaling compounds regulate metabolic and transcriptional networks, survival pathways and inflammatory responses. Aggregation of fatty acids with fatty acid binding proteins (FABPs) facilitates their transportation to different cell organelles. FABPs, a group of lipid binding proteins modulate fatty acid metabolism, cell growth and proliferation and cancer development. They may be used as tumor marker in some cancers. FABPs are expressed in most malignancies such as prostate, breast, liver, bladder and lung cancer which are associated with the incidence, proliferation, metastasis, invasion of tumors. This review introduces several isoforms of FABPs (FABP1-12) and summarizes their function and their possible roles in cancer development through some proposed mechanisms.