Inhibition of fatty acid synthase (FASN) affects the proliferation and apoptosis of HepG2 hepatoma carcinoma cells via the β-catenin/C-myc signaling pathway

Fatty Acid Synthase Promotes Hepatocellular Carcinoma Growth via S-Phase Kinase-Associated Protein 2/p27KIP1 Regulation

Background and Objectives: Aberrant upregulation of fatty acid synthase (FASN), catalyzing de novo synthesis of fatty acids, occurs in various tumor types, including human hepatocellular carcinoma (HCC). Although FASN oncogenic activity seems to reside in its pro-lipogenic function, cumulating evidence suggests that FASN's tumor-supporting role might also be metabolic-independent. Materials and Methods: In the present study, we show that FASN inactivation by specific small interfering RNA (siRNA) promoted the downregulation of the S-phase kinase associated-protein kinase 2 (SKP2) and the consequent induction of p27KIP1 in HCC cell lines. Results: Expression levels of FASN and SKP2 directly correlated in human HCC specimens and predicted a dismal outcome. In addition, forced overexpression of SKP2 rendered HCC cells resistant to the treatment with the FASN inhibitor C75. Furthermore, FASN deletion was paralleled by SKP2 downregulation and p27KIP1 induction in the AKT-driven HCC preclinical mouse model. Moreover, forced overexpression of an SKP2 dominant negative form or a p27KIP1 non-phosphorylatable (p27KIP1-T187A) construct completely abolished AKT-dependent hepatocarcinogenesis in vitro and in vivo. Conclusions: In conclusion, the present data indicate that SKP2 is a critical downstream effector of FASN and AKT-dependent hepatocarcinogenesis in liver cancer, envisaging the possibility of effectively targeting FASN-positive liver tumors with SKP2 inhibitors or p27KIP1 activators.

Targeting metabolic reprogramming to overcome drug resistance in advanced bladder cancer: insights from gemcitabine- and cisplatin-resistant models

Gemcitabine plus cisplatin (GC) combination chemotherapy is the primary treatment for advanced bladder cancer (BC) with unresectable or metastatic disease. However, most cases develop resistance to this therapy. We investigated whether drug resistance could be targeted through metabolic reprogramming therapies. Metabolomics analyses in our lab's gemcitabine- and cisplatin-resistant cell lines revealed increased phosphoglycerate dehydrogenase (PHGDH) expression in gemcitabine-resistant cells compared with parental cells. Isocitrate dehydrogenase 2 (IDH2) gain of function stabilized hypoxia-inducible factor1α (HIF1α) expression, stimulating aerobic glycolysis. In gemcitabine-resistant cells, elevated fumaric acid suppressed prolyl hydroxylase domain-containing protein 2/Egl nine homolog 1 (PHD2) and stabilized HIF1α expression. PHGDH downregulation or inhibition in gemcitabine-resistant BC cells inhibited their proliferation, migration, and invasion. Cisplatin-resistant cells showed elevated fatty acid metabolism, upregulating fatty acid synthase (FASN) downstream of tyrosine kinase. Using the fibroblast growth factor receptor (FGFR) tyrosine kinase inhibitor erdafitinib, we inhibited malonyl-CoA production, which is crucial for fatty acid synthesis, and thereby suppressed upregulated HIF1α expression. Combination treatment with NCT503 and erdafitinib synergistically suppressed tumor cell proliferation and induced apoptosis in vitro and in vivo. Understanding these mechanisms could enable innovative BC therapeutic strategies to be developed.

The Regulation of Fatty Acid Synthase by Exosomal miR-143-5p and miR-342-5p in Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive disease caused by an aberrant repair of injured alveolar epithelial cells. The maintenance of the alveolar epithelium and its regeneration after the damage is fueled by alveolar type II (ATII) cells. Injured cells release exosomes containing microRNAs (miRNAs), which can alter the recipient cells' function. Lung tissue, ATII cells, fibroblasts, plasma, and exosomes were obtained from naive patients with IPF, patients with IPF taking pirfenidone or nintedanib, and control organ donors. miRNA expression was analyzed to study their impact on exosome-mediated effects in IPF. High miR-143-5p and miR-342-5p levels were detected in ATII cells, lung tissue, plasma, and exosomes in naive patients with IPF. Decreased FASN (fatty acid synthase) and ACSL-4 (acyl-CoA-synthetase long-chain family member 4) expression was found in ATII cells. miR-143-5p and miR-342-5p overexpression or ATII cell treatment with IPF-derived exosomes containing these miRNAs lowered FASN and ACSL-4 levels. Also, this contributed to ATII cell injury and senescence. However, exosomes isolated from patients with IPF taking nintedanib or pirfenidone increased FASN expression in ATII cells compared with naive patients with IPF. Furthermore, fibroblast treatment with exosomes obtained from naive patients with IPF increased SMAD3, CTGF, COL3A1, and TGFβ1 expression. Our results suggest that IPF-derived exosomes containing miR-143-5p and miR-342-5p inhibited the de novo fatty acid synthesis pathway in ATII cells. They also induced the profibrotic response in fibroblasts. Pirfenidone and nintedanib improved ATII cell function and inhibited fibrogenesis. This study highlights the importance of exosomes in IPF pathophysiology.

Khalas date flavonoids inhibited cell viability, induced apoptosis and expression of the pro-autophagy LC3-B gene in human hepatocellular carcinoma cells (HepG2)

Autophagy is a protective mechanism important in human diseases as cancer. We evaluated the impact of khalas date extract (KDE) (20-60 mg/mL) on cell viability, morphological changes, DNA fragmentation and gene expression of LC3B-II associated with autophagosome on HepG2 cell line. The GC/MS identification of KDE showed its high content of flavonoids including quercetin, myricetin, kaempferol and catechol. KDE reduced cell viability of HepG2 with IC50 (31.52 mg/mL). Cells treated with KDE showed two band of DNA fragments at (30 and 40 mg) indicating that KDE induced DNA damage and apoptosis in HepG2. The analysis RT-PCR data showed a 0.2-fold increase in the expression of LC3-B in the cells treated with KDE versus control. We concluded that, KDE flavonoids such as quercetin, myricetin kaempferol exhibited anticancer properties manifested by inhibition of HepG2 cell viability and induction of apoptosis and upregulation of the pro-autophagy LC3-B gene.

Investigating the Function of Human Jumping Translocation Breakpoint Protein (hJTB) and Its Interacting Partners through In-Solution Proteomics of MCF7 Cells

Human jumping translocation breakpoint (hJTB) gene is located on chromosome 1q21 and is involved in unbalanced translocation in many types of cancer. JTB protein is ubiquitously present in normal cells but it is found to be overexpressed or downregulated in various types of cancer cells, where this protein and its isoforms promote mitochondrial dysfunction, resistance to apoptosis, genomic instability, proliferation, invasion and metastasis. Hence, JTB could be a tumor biomarker for different types of cancer, such as breast cancer (BC), and could be used as a drug target for therapy. However, the functions of the protein or the pathways through which it increases cell proliferation and invasiveness of cancer cells are not well-known. Therefore, we aim to investigate the functions of JTB by using in-solution digestion-based cellular proteomics of control and upregulated and downregulated JTB protein in MCF7 breast cancer cell line, taking account that in-solution digestion-based proteomics experiments are complementary to the initial in-gel based ones. Proteomics analysis allows investigation of protein dysregulation patterns that indicate the function of the protein and its interacting partners, as well as the pathways and biological processes through which it functions. We concluded that JTB dysregulation increases the epithelial-mesenchymal transition (EMT) potential and cell proliferation, harnessing cytoskeleton organization, apical junctional complex, metabolic reprogramming, and cellular proteostasis. Deregulated JTB expression was found to be associated with several proteins involved in mitochondrial organization and function, oxidative stress (OS), apoptosis, and interferon alpha and gamma signaling. Consistent and complementary to our previous results emerged by using in-gel based proteomics of transfected MCF7 cells, JTB-related proteins that are overexpressed in this experiment suggest the development of a more aggressive phenotype and behavior for this luminal type A non-invasive/poor-invasive human BC cell line that does not usually migrate or invade compared with the highly metastatic MDA-MB-231 cells. This more aggressive phenotype of MCF7 cells related to JTB dysregulation and detected by both in-gel and in-solution proteomics could be promoted by synergistic upregulation of EMT, Mitotic spindle and Fatty acid metabolism pathways. However, in both JTB dysregulated conditions, several downregulated JTB-interacting proteins predominantly sustain antitumor activities, attenuating some of the aggressive phenotypical and behavioral traits promoted by the overexpressed JTB-related partners.

Proteomics-Based Identification of Dysregulated Proteins in Breast Cancer

Immunohistochemistry (IHC) is still widely used as a morphology-based assay for in situ analysis of target proteins as specific tumor antigens. However, as a very heterogeneous collection of neoplastic diseases, breast cancer (BC) requires an accurate identification and characterization of larger panels of candidate biomarkers, beyond ER, PR, and HER2 proteins, for diagnosis and personalized treatment, without the limited availability of antibodies that are required to identify specific proteins. Top-down, middle-down, and bottom-up mass spectrometry (MS)-based proteomics approaches complement traditional histopathological tissue analysis to examine expression, modification, and interaction of hundreds to thousands of proteins simultaneously. In this review, we discuss the proteomics-based identification of dysregulated proteins in BC that are essential for the following issues: discovery and validation of new biomarkers by analysis of solid and liquid/non-invasive biopsies, cell lines, organoids and xenograft models; identification of panels of biomarkers for early detection and accurate discrimination between cancer, benign and normal tissues; identification of subtype-specific and stage-specific protein expression profiles in BC grading and measurement of disease progression; characterization of new subtypes of BC; characterization and quantitation of post-translational modifications (PTMs) and aberrant protein-protein interactions (PPI) involved in tumor development; characterization of the global remodeling of BC tissue homeostasis, diagnosis and prognostic information; and deciphering of molecular functions, biological processes and mechanisms through which the dysregulated proteins cause tumor initiation, invasion, and treatment resistance.

Epigallocatechin gallate triggers apoptosis by suppressing de novo lipogenesis in colorectal carcinoma cells

The de novo lipogenesis (DNL) pathway has been identified as a regulator of cancer progression and aggressiveness. Downregulation of key lipogenesis enzymes has been shown to activate apoptosis in cancerous cells. Epigallocatechin gallate (EGCG) inhibits cancer cell proliferation without causing cytotoxicity in healthy cells. The aim of the present study is to investigate the effects of EGCG on the promotion of apoptosis associated with the DNL pathway inhibition in cancer cells, both in vitro and in vivo. We observed that two colorectal cancer (CRC) cell lines (HCT116 and HT-29) had a higher cytotoxic response to EGCG treatment than hepatocellular carcinoma cells, including HepG2 and HuH-7. EGCG treatment decreased cell viability and increased mitochondrial damage-triggered apoptosis in both HCT116 and HT-29 cancer cells. Additionally, we treated mice transplanted with HCT116 cells with 30 or 50 mg/kg EGCG for 7 days to evaluate the apoptotic effects of EGCN treatment in a xenograft mouse model of cancer. We observed a decrease in intracellular fatty acid levels, which suggested that EGCG-induced apoptosis was associated with a decrease in fatty acid levels in cancer. Suppression of adenosine triphosphate synthesis by EGCG indicated that cell death induction in cancer cells could be mediated by shared components of the DNL and energy metabolism pathways. In addition, EGCG-induced apoptosis suppressed the expression of the phosphorylation protein kinase B and extracellular signal-regulated kinase 1/2 signaling proteins in tumors from xenografted mice. Cytotoxic effects in unaffected organs and tissues of the mouse xenograft model were absent upon EGCG treatment.

Differential growth inhibition, cell cycle arrest and apoptosis of MCF-7 and MDA-MB-231 cells to holocarboxylase synthetase suppression

Holocarboxylase synthetase (HLCS) catalyzes the covalent attachment of biotin onto the biotin-dependent carboxylases. Recent studies have shown that HLCS is over-expressed in breast cancer patients. Here we investigated the functional roles of free biotin and HLCS in supporting growth and migration of breast cancer cell lines. Depletion of biotin from culture medium markedly reduced biotinylation of the two most abundant biotin-carboxylases, acetyl-CoA carboxylase and pyruvate carboxylase. This was accompanied by a marked decrease in cell growth. Suppression of HLCS expression in the low invasive breast cancer cell line MCF-7 resulted in an 80% reduction of biotinylated ACC, but not PC. HLCS knockdown MCF-7 cell lines showed 40-50% reduction of proliferation and 35% reduction of migration, accompanied by G1 cell cycle-arrest-induced apoptosis. In contrast, knockdown of HLCS expression in the highly invasive cell line MDA-MB-231 resulted in only marginal reduction of biotinylation of both ACC and PC, accompanied by 30% reduction of proliferation and 30% reduction of migration. Our studies provide new insights to use HLCS as a novel anti-cancer drug target.

Triclosan down-regulates fatty acid synthase through microRNAs in HepG2 cells

Triclosan is a promising candidate of fatty acid synthase (FASN) inhibitor by blocking FASN activity, but its effect on FASN expression and the underling epigenetic mechanism remain elusive. In this study, the effect of triclosan on FASN mRNA and protein expressions in human HepG2 cells and the regulatory role of microRNAs (miRNAs) in the downregulation of FASN induced by triclosan were explored through experiments and bioinformatics analysis. The results showed that triclosan not only directly inhibited FASN activity, but also significantly decreased FASN mRNA and protein levels in human liver HepG2 cells. Nine miRNAs targeting FASN mRNA degradation were identified by miRNA prediction tools, and the expression levels of these nine miRNAs were then detected by real-time quantitative PCR. Triclosan significantly increased the expressions of the six miRNAs, namely miR-15a, miR-107, miR-195, miR-424, miR-497 and miR-503, leading to the downregulation of FASN. Further investigation revealed that the six triclosan-upregulated miRNAs played an important regulatory role in lipid metabolism and cell cycle by gene ontology annotations and pathway analysis. Consistent with the results of bioinformatics analyses, triclosan significantly reduced the intracellular lipid content by triglyceride assay, oil red O, BODIPY 493/503 and Nile Red staining, thereby inhibiting the growth of HepG2 cells through apoptosis. Taken together, our study reveals that triclosan downregulates FASN expression through a variety of miRNAs, providing new insight for triclosan as a FASN inhibitor candidate to regulate lipid metabolism in human hepatoma cells.

Review on target domains and natural compound-based inhibitors of fatty acid synthase for anticancer drug discovery

Cancer cells require a higher amount of energy in the form of fatty acids for their uncontrolled proliferation and growth. Fatty acid synthase (FASN) plays a crucial role in the synthesis of palmitate, which is involved in most of the critical malignant pathways. Hence, by targeting FASN, tumour growth can be controlled. By designing and developing FASN inhibitors with catalytic domain specificity, safe and potential anticancer drugs can be achieved. The article draws light towards the catalytic domains of FASN, their active site residues and interaction of some of the reported natural FASN inhibitors (resveratrol, lavandulyl flavonoids, catechins, stilbene derivatives, etc). The rationality (structure-activity relationship) behind the variation in the activity of the reported natural FASN inhibitors (butyrolactones, polyphenolics, galloyl esters and thiolactomycins) has also been covered. Selective, safe and potentially active FASN inhibitors could be developed by: (i) having proper understanding of the function of all catalytic domains of FASN (ii) studying the upstream and downstream FASN regulators (iii) identifying cancer-specific FASN biomarkers (that are non-essential/absent in the normal healthy cells) (iv) exploring the complete protein structure of FASN, e-screening of the compounds prior to synthesis and study their ADME properties (v) predicting the selectivity based on their strong affinity at the catalytic site of FASN.

Expression and prognostic significance of fatty acid synthase in clear cell renal cell carcinoma

Fatty acid synthase (FASN), a key enzyme essential for fatty acid (FA) synthesis, was reportedly implicated in the initiation and progression of various cancers. However, the clinical significance of FASN in renal cell carcinoma (RCC) has not been fully elucidated yet. Here we compare the expression profile and evaluate the prognostic significance of FASN in clear cell RCC (ccRCC) patients. FASN expression was examined in 3 pairs ccRCC and their adjacent nontumor tissues by western blotting (WB) analysis, and its expression was assessed in 145 ccRCC and 13 nontumor tissues by immunohistochemistry (IHC) analysis with tissue microarrays (TMAs). The prognosis of FASN was further investigated in large-scale database using LinkedOmics (n = 537) and The Cancer Protein Atlas (TCPA, n = 445), respectively. WB detected higher FASN expression in ccRCC than normal tissues, then IHC analysis revealed that FASN expression was positively associated with histological grade, pathological stage, tumor size and metastasis status, and negatively associated with cancer-specific survival (CSS). Univariate survival analysis demonstrated that high grade, advanced stage, large tumor, metastasis, and high FASN expression were significantly associated with a shorter CSS, and multivariate analysis revealed tumor grade, stage, metastasis and FASN were identified as independent predictors for CSS in patients with ccRCC. Further LinkedOmics and TCPA analyses confirmed that high FASN expression was correlated with a poorer overall survival (OS) of ccRCC. Collectively, these findings demonstrated FASN could be a poor prognostic factor in ccRCC patients, which indicated that FA synthesis might be implicated in the tumorigenesis and progression of ccRCC.