Carnitine palmitoyl transferase-1A (CPT1A): a new tumor specific target in human breast cancer

Identification of ACAA1 and HADHB as potential prognostic biomarkers based on a novel fatty acid oxidation-related gene model in head and neck squamous cell carcinoma: A retrospective study

OBJECTIVES

To investigate the importance of fatty acid oxidation (FAO)-related genes in predicting the progression and prognosis of head and neck squamous cell carcinoma (HNSCC).

METHODS

The FAO-related gene prognostic model was established employing Cox regression analyses, during which accuracy and sensitivity of the gene model were evaluated in The Cancer Genome Atlas (TCGA) internal testing and Gene Expression Omnibus (GEO) external validation cohorts. Ultimately, hub genes were identified among 13 model genes using STRING and Cytoscape, with preliminary validation carried out through immunohistochemistry.

RESULTS

The model, which comprised 13 genes (ABCD2, ACAA1, ACACB, AKT1, CNR1, CPT1C, CROT, ECHDC2, ETFA, HADHB, IRS2, LONP2, and SLC25A17), was established. On the basis of the median risk score, the two cohorts were grouped into low-and high-risk groups in the subsequent test and validation, and the former exhibited significantly higher survival rates than the latter. Nomograms were established based on prognostic factors, including stage and risk score, and individualized for the prediction of HNSCC patients. Ultimately, immunohistochemical staining showed that ACAA1 and HADHB were significantly under-expressed in HNSCC, with a favorable prognosis associated with low HADHB and high ACAA1.

CONCLUSIONS

The gene prognostic model has illustrated promising capability in predicting the prognosis, and ACAA1 and HADHB might serve as potential therapeutic biomarkers for HNSCC patients.

ACSL3 regulates breast cancer progression via lipid metabolism reprogramming and the YES1/YAP axis

OBJECTIVE

Mitochondrial fatty acid oxidation is a metabolic pathway whose dysregulation is recognized as a critical factor in various cancers, because it sustains cancer cell survival, proliferation, and metastasis. The acyl-CoA synthetase long-chain (ACSL) family is known to activate long-chain fatty acids, yet the specific role of ACSL3 in breast cancer has not been determined.

METHODS

We assessed the prognostic value of ACSL3 in breast cancer by using data from tumor samples. Gain-of-function and loss-of-function assays were also conducted to determine the roles and downstream regulatory mechanisms of ACSL3 in vitro and in vivo.

RESULTS

ACSL3 expression was notably downregulated in breast cancer tissues compared with normal tissues, and this phenotype correlated with improved survival outcomes. Functional experiments revealed that ACSL3 knockdown in breast cancer cells promoted cell proliferation, migration, and epithelial-mesenchymal transition. Mechanistically, ACSL3 was found to inhibit β-oxidation and the formation of associated byproducts, thereby suppressing malignant behavior in breast cancer. Importantly, ACSL3 was found to interact with YES proto-oncogene 1, a member of the Src family of tyrosine kinases, and to suppress its activation through phosphorylation at Tyr419. The decrease in activated YES1 consequently inhibited YAP1 nuclear colocalization and transcriptional complex formation, and the expression of its downstream genes in breast cancer cell nuclei.

CONCLUSIONS

ACSL3 suppresses breast cancer progression by impeding lipid metabolism reprogramming, and inhibiting malignant behaviors through phospho-YES1 mediated inhibition of YAP1 and its downstream pathways. These findings suggest that ACSL3 may serve as a potential biomarker and target for comprehensive therapeutic strategies for breast cancer.

Myoglobin Inhibits Breast Cancer Cell Fatty Acid Oxidation and Migration via Heme-dependent Oxidant Production and Not Fatty Acid Binding

The monomeric heme protein myoglobin (Mb), traditionally thought to be expressed exclusively in cardiac and skeletal muscle, is now known to be expressed in approximately 40% of breast tumors. While Mb expression is associated with better patient prognosis, the molecular mechanisms by which Mb limits cancer progression are unclear. In muscle, Mb's predominant function is oxygen storage and delivery, which is dependent on the protein's heme moiety. However, prior studies demonstrate that the low levels of Mb expressed in cancer cells preclude this function. Recent studies propose a novel fatty acid binding function for Mb via a lysine residue (K46) in the heme pocket. Given that cancer cells can upregulate fatty acid oxidation (FAO) to maintain energy production for cytoskeletal remodeling during cell migration, we tested whether Mb-mediated fatty acid binding modulates FAO to decrease breast cancer cell migration. We demonstrate that the stable expression of human Mb in MDA-MB-231 breast cancer cells decreases cell migration and FAO. Site-directed mutagenesis of Mb to disrupt Mb fatty acid binding did not reverse Mb-mediated attenuation of FAO or cell migration in these cells. In contrast, cells expressing Apo-Mb, in which heme incorporation was disrupted, showed a reversal of Mb-mediated attenuation of FAO and cell migration, suggesting that Mb attenuates FAO and migration via a heme-dependent mechanism rather than through fatty acid binding. To this end, we show that Mb's heme-dependent oxidant generation propagates dysregulated gene expression of migratory genes, and this is reversed by catalase treatment. Collectively, these data demonstrate that Mb decreases breast cancer cell migration, and this effect is due to heme-mediated oxidant production rather than fatty acid binding. The implication of these results will be discussed in the context of therapeutic strategies to modulate oxidant production and Mb in tumors.

Highlights

Myoglobin (Mb) expression in MDA-MB-231 breast cancer cells slows migration.Mb expression decreases mitochondrial respiration and fatty acid oxidation.Mb-dependent fatty acid binding does not regulate cell migration or respiration.Mb-dependent oxidant generation decreases mitochondrial metabolism and migration.Mb-derived oxidants dysregulate migratory gene expression.

The lipid metabolism remodeling: A hurdle in breast cancer therapy

Lipids, as one of the three primary energy sources, provide energy for all cellular life activities. Lipids are also known to be involved in the formation of cell membranes and play an important role as signaling molecules in the intracellular and microenvironment. Tumor cells actively or passively remodel lipid metabolism, using the function of lipids in various important cellular life activities to evade therapeutic attack. Breast cancer has become the leading cause of cancer-related deaths in women, which is partly due to therapeutic resistance. It is necessary to fully elucidate the formation and mechanisms of chemoresistance to improve breast cancer patient survival rates. Altered lipid metabolism has been observed in breast cancer with therapeutic resistance, indicating that targeting lipid reprogramming is a promising anticancer strategy.

circPSD3 is a promising inhibitor of uPA system to inhibit vascular invasion and metastasis in hepatocellular carcinoma

BACKGROUND

Vascular invasion is a major route for intrahepatic and distant metastasis in hepatocellular carcinoma (HCC) and is a strong negative prognostic factor. Circular RNAs (circRNAs) play important roles in tumorigenesis and metastasis. However, the regulatory functions and underlying mechanisms of circRNAs in the development of vascular invasion in HCC are largely unknown.

METHODS

High throughput sequencing was used to screen dysregulated circRNAs in portal vein tumor thrombosis (PVTT) tissues. The biological functions of candidate circRNAs in the migration, vascular invasion, and metastasis of HCC cells were examined in vitro and in vivo. To explore the underlying mechanisms, RNA sequencing, MS2-tagged RNA affinity purification, mass spectrometry, and RNA immunoprecipitation assays were performed.

RESULTS

circRNA sequencing followed by quantitative real-time PCR (qRT-PCR) revealed that circRNA pleckstrin and Sect. 7 domain containing 3 (circPSD3) was significantly downregulated in PVTT tissues. Decreased circPSD3 expression in HCC tissues was associated with unfavourable characteristics and predicted poor prognosis in HCC. TAR DNA-binding protein 43 (TDP43) inhibited the biogenesis of circPSD3 by interacting with the downstream intron of pre-PSD3. circPSD3 inhibited the intrahepatic vascular invasion and metastasis of HCC cells in vitro and in vivo. Serpin family B member 2 (SERPINB2), an endogenous bona fide inhibitor of the urokinase-type plasminogen activator (uPA) system, is the downstream target of circPSD3. Mechanistically, circPSD3 interacts with histone deacetylase 1 (HDAC1) to sequester it in the cytoplasm, attenuating the inhibitory effect of HDAC1 on the transcription of SERPINB2. In vitro and in vivo studies demonstrated that circPSD3 is a promising inhibitor of the uPA system.

CONCLUSIONS

circPSD3 is an essential regulator of vascular invasion and metastasis in HCC and may serve as a prognostic biomarker and therapeutic target.

The Physiological and Pathological Role of Acyl-CoA Oxidation

Fatty acid metabolism, including β-oxidation (βOX), plays an important role in human physiology and pathology. βOX is an essential process in the energy metabolism of most human cells. Moreover, βOX is also the source of acetyl-CoA, the substrate for (a) ketone bodies synthesis, (b) cholesterol synthesis, (c) phase II detoxication, (d) protein acetylation, and (d) the synthesis of many other compounds, including N-acetylglutamate-an important regulator of urea synthesis. This review describes the current knowledge on the importance of the mitochondrial and peroxisomal βOX in various organs, including the liver, heart, kidney, lung, gastrointestinal tract, peripheral white blood cells, and other cells. In addition, the diseases associated with a disturbance of fatty acid oxidation (FAO) in the liver, heart, kidney, lung, alimentary tract, and other organs or cells are presented. Special attention was paid to abnormalities of FAO in cancer cells and the diseases caused by mutations in gene-encoding enzymes involved in FAO. Finally, issues related to α- and ω- fatty acid oxidation are discussed.

The Carnitine Palmitoyltransferase 1A Inhibitor Teglicar Shows Promising Antitumour Activity against Canine Mammary Cancer Cells by Inducing Apoptosis

Canine mammary tumours (CMTs) are the most common cancer in intact female dogs. In addition to surgery, additional targeted and non-targeted therapies may offer survival benefits to these patients. Therefore, exploring new treatments for CMT is a promising area in veterinary oncology. CMT cells have an altered lipid metabolism and use the oxidation of fatty acids for their energy needs. Here we investigated the tumoricidal effects of teglicar, a reversible inhibitor of carnitine palmitoyl transferase 1A (CPT1A), the rate-limiting enzyme for fatty acid import into mitochondria, on two CMT cells, P114 and CMT-U229. Viability and apoptosis were examined in CMT cells using the crystal violet assay, trypan blue assay, and flow cytometry analysis. The expression of mediators of apoptosis signalling (e.g., caspase-9, caspase-8, and caspase-3) was assessed by quantitative real-time polymerase chain reaction and western blot analyses. Teglicar was able to decrease cell viability and induce apoptosis in P114 and CMT-U229 cells. At the molecular level, the effect of teglicar was associated with an upregulation of the mRNA expression levels of caspase-9, caspase-8, and caspase-3 and an increase in their protein levels. In summary, our results show that teglicar has a potential effect against CMTs through the induction of apoptotic cell death, making it a promising therapeutic agent against CMTs.

Targeting Mitochondria with ClpP Agonists as a Novel Therapeutic Opportunity in Breast Cancer

Breast cancer is the most frequently diagnosed malignancy worldwide and the leading cause of cancer mortality in women. Despite the recent development of new therapeutics including targeted therapies and immunotherapy, triple-negative breast cancer remains an aggressive form of breast cancer, and thus improved treatments are needed. In recent decades, it has become increasingly clear that breast cancers harbor metabolic plasticity that is controlled by mitochondria. A myriad of studies provide evidence that mitochondria are essential to breast cancer progression. Mitochondria in breast cancers are widely reprogrammed to enhance energy production and biosynthesis of macromolecules required for tumor growth. In this review, we will discuss the current understanding of mitochondrial roles in breast cancers and elucidate why mitochondria are a rational therapeutic target. We will then outline the status of the use of mitochondria-targeting drugs in breast cancers, and highlight ClpP agonists as emerging mitochondria-targeting drugs with a unique mechanism of action. We also illustrate possible drug combination strategies and challenges in the future breast cancer clinic.

A palmitate-rich metastatic niche enables metastasis growth via p65 acetylation resulting in pro-metastatic NF-κB signaling

Metabolic rewiring is often considered an adaptive pressure limiting metastasis formation; however, some nutrients available at distant organs may inherently promote metastatic growth. We find that the lung and liver are lipid-rich environments. Moreover, we observe that pre-metastatic niche formation increases palmitate availability only in the lung, whereas a high-fat diet increases it in both organs. In line with this, targeting palmitate processing inhibits breast cancer-derived lung metastasis formation. Mechanistically, breast cancer cells use palmitate to synthesize acetyl-CoA in a carnitine palmitoyltransferase 1a-dependent manner. Concomitantly, lysine acetyltransferase 2a expression is promoted by palmitate, linking the available acetyl-CoA to the acetylation of the nuclear factor-kappaB subunit p65. Deletion of lysine acetyltransferase 2a or carnitine palmitoyltransferase 1a reduces metastasis formation in lean and high-fat diet mice, and lung and liver metastases from patients with breast cancer show coexpression of both proteins. In conclusion, palmitate-rich environments foster metastases growth by increasing p65 acetylation, resulting in a pro-metastatic nuclear factor-kappaB signaling.

The emerging role of PPAR-alpha in breast cancer

Breast cancer has been confirmed to have lipid disorders in the tumour microenvironment. Peroxisome proliferator-activated receptor alpha (PPARα) is a ligand-activated transcriptional factor that belongs to the family of nuclear receptors. PPARα regulates the expression of genes involved in fatty acid homeostasis and is a major regulator of lipid metabolism. Because of its effects on lipid metabolism, an increasing number of studies have investigated the relationship of PPARα with breast cancer. PPARα has been shown to impact the cell cycle and apoptosis in normal cells and tumoral cells through regulating genes of the lipogenic pathway, fatty acid oxidation, fatty acid activation, and uptake of exogenous fatty acids. Besides, PPARα is involved in the regulation of the tumour microenvironment (anti-inflammation and inhibition of angiogenesis) by modulating different signal pathways such as NF-κB and PI3K/AKT/mTOR. Some synthetic PPARα ligands are used in adjuvant therapy for breast cancer. PPARα agonists are reported to reduce the side effects of chemotherapy and endocrine therapy. In addition, PPARα agonists enhance the curative effects of targeted therapy and radiation therapy. Interestingly, with the emerging role of immunotherapy, attention has been focused on the tumour microenvironment. The dual functions of PPARα agonists in immunotherapy need further research. This review aims to consolidate the operations of PPARα in lipid-related and other ways, as well as discuss the current and potential applications of PPARα agonists in tackling breast cancer.

Catechol-O-methyl transferase suppresses cell invasion and interplays with MET signaling in estrogen dependent breast cancer

Catechol-O-methyl transferase (COMT) is involved in detoxification of catechol estrogens, playing cancer-protective role in cells producing or utilizing estrogen. Moreover, COMT suppressed migration potential of breast cancer (BC) cells. To delineate COMT role in metastasis of estrogen receptor (ER) dependent BC, we investigated the effect of COMT overexpression on invasion, transcriptome, proteome and interactome of MCF7 cells, a luminal A BC model, stably transduced with lentiviral vector carrying COMT gene (MCF7-COMT). 2D and 3D assays revealed that COMT overexpression associates with decreased cell invasion (p < 0.0001 for Transwell assay, p < 0.05 for spheroid formation). RNA-Seq and LC-DIA-MS/MS proteomics identified genes associated with invasion (FTO, PIR, TACSTD2, ANXA3, KRT80, S100P, PREX1, CLEC3A, LCP1) being downregulated in MCF7-COMT cells, while genes associated with less aggressive phenotype (RBPMS, ROBO2, SELENBP, EPB41L2) were upregulated both at transcript (|log2FC|> 1, adj. p < 0.05) and protein (|log2FC|> 0.58, q < 0.05) levels. Importantly, proteins driving MET signaling were less abundant in COMT overexpressing cells, and pull-down confirmed interaction between COMT and Kunitz-type protease inhibitor 2 (SPINT2), a negative regulator of MET (log2FC = 5.10, q = 1.04-7). In conclusion, COMT may act as tumor suppressor in ER dependent BC not only by detoxification of catechol estrogens but also by suppressing cell invasion and interplay with MET pathway.

The impact of variance in carnitine palmitoyltransferase-1 expression on breast cancer prognosis is stratified by clinical and anthropometric factors

CPT1A is a rate-limiting enzyme in fatty acid oxidation and is upregulated in high-risk breast cancer. Obesity and menopausal status' relationship with breast cancer prognosis is well established, but its connection with fatty acid metabolism is not. We utilized RNA sequencing data in the Xena Functional Genomics Explorer, to explore CPT1A's effect on breast cancer patients' survival probability. Using [18F]-fluorothymidine positron emission tomography-computed tomography images from The Cancer Imaging Archive, we segmented these analyses by obesity and menopausal status. In 1214 patients, higher CPT1A expression is associated with lower breast cancer survivability. We confirmed a previously observed protective relationship between obesity and breast cancer in pre-menopausal patients and supported this data using two-sided Pearson correlations. Taken together, these analyses using open-access databases bolster the potential role of CPT1A-dependent fatty acid metabolism as a pathogenic factor in breast cancer.

Lipid Metabolism Heterogeneity and Crosstalk with Mitochondria Functions Drive Breast Cancer Progression and Drug Resistance

Breast cancer (BC) is a heterogeneous disease that can be triggered by genetic alterations in mammary epithelial cells, leading to diverse disease outcomes in individual patients. The metabolic heterogeneity of BC enhances its ability to adapt to changes in the tumor microenvironment and metabolic stress, but unfavorably affects the patient's therapy response, prognosis and clinical effect. Extrinsic factors from the tumor microenvironment and the intrinsic parameters of cancer cells influence their mitochondrial functions, which consequently alter their lipid metabolism and their ability to proliferate, migrate and survive in a harsh environment. The balanced interplay between mitochondria and fatty acid synthesis or fatty acid oxidation has been attributed to a combination of environmental factors and to the genetic makeup, oncogenic signaling and activities of different transcription factors. Hence, understanding the mechanisms underlying lipid metabolic heterogeneity and alterations in BC is gaining interest as a major target for drug resistance. Here we review the major recent reports on lipid metabolism heterogeneity and bring to light knowledge on the functional contribution of diverse lipid metabolic pathways to breast tumorigenesis and therapy resistance.

Augmented CPT1A Expression Is Associated with Proliferation and Colony Formation during Barrett’s Tumorigenesis

Obesity is a known risk factor for the development of gastroesophageal reflux disease (GERD), Barrett’s Esophagus (BE) and the progression to esophageal adenocarcinoma. The mechanisms by which obesity contributes to GERD, BE and its progression are currently not well understood. Recently, changes in lipid metabolism especially in the context of a high fat diet have been linked to GERD and BE leading us to explore whether fatty acid oxidation plays a role in the disease progression from GERD to esophageal adenocarcinoma. To that end, we analyzed the expression of the rate-limiting enzyme, carnitine palmytoyltransferase 1A (CPT1A), in human tissues and cell lines representing different stages in the sequence from normal squamous esophagus to cancer. We determined uptake of palmitic acid, the most abundant fatty acid in human serum, with fluorescent dye-labeled lipids as well as functional consequences of stimulation with palmitic acid relevant to Barrett’s tumorigenesis, e.g., proliferation, characteristics of stemness and IL8 mediated inflammatory signaling. We further employed different mouse models including a genetic model of Barrett’s esophagus based on IL1β overexpression in the presence and absence of a high fat diet and deoxycholic acid to physiologically mimic gastrointestinal reflux in the mice. Together, our data demonstrate that CPT1A is upregulated in Barrett’s tumorigenesis and that experimental palmitic acid is delivered to mitochondria and associated with increased cell proliferation and stem cell marker expression.

The role of CPT1A as a biomarker of breast cancer progression: a bioinformatic approach

Breast cancer is the commonest malignancy of women and with its incidence on the rise, the need to identify new targets for treatment is imperative. There is a growing interest in the role of lipid metabolism in cancer. Carnitine palmitoyl-transferase-1 (CPT-1); the rate limiting step in fatty acid oxidation, has been shown to be overexpressed in a range of tumours. There are three isoforms of CPT-1; A, B and C. It is CPT-1A that has been shown to be the predominant isoform which is overexpressed in breast cancer. We performed a bioinformatic analysis using readily available online platforms to establish the prognostic and predictive effects related to CPT-1A expression. These include the KM plotter, the Human Protein Atlas, the cBioPortal, the G2O, the MethSurvand the ROC plotter. A Network analysis was performed using the Oncomine platform and signalling pathways constituting the cancer hallmarks, including immune regulation as utilised by NanoString. The epigenetic pathways were obtained from the EpiFactor website. Spearman correlations (r) to determine the relationship between CPT-1A and the immune response were obtained using the TISIDB portal. Overexpression of CPT-1A largely confers a worse prognosis and CPT-1A progressively recruits a range of pathways as breast cancer progresses. CPT-1A's interactions with cancer pathways is far wider than previously realised and includes associations with epigenetic regulation and immune evasion pathways, as well as wild-type moderate to high penetrant genes involved in hereditary breast cancer. Although CPT-1A genomic alterations are detected in 9% of breast carcinomas, both the alteration and the metagene associated with it, confers a poor prognosis. CPT-1A expression can be utilised as a biomarker of disease progression and as a potential therapeutic target.

The role of lipid metabolism in tumor immune microenvironment and potential therapeutic strategies

Aberrant lipid metabolism is nonnegligible for tumor cells to adapt to the tumor microenvironment (TME). It plays a significant role in the amount and function of immune cells, including tumor-associated macrophages, T cells, dendritic cells and marrow-derived suppressor cells. It is well-known that the immune response in TME is suppressed and lipid metabolism is closely involved in this process. Immunotherapy, containing anti-PD1/PDL1 therapy and adoptive T cell therapy, is a crucial clinical cancer therapeutic strategy nowadays, but they display a low-sensibility in certain cancers. In this review, we mainly discussed the importance of lipid metabolism in the formation of immunosuppressive TME, and explored the effectiveness and sensitivity of immunotherapy treatment by regulating the lipid metabolism.

A Proof-of-Concept Inhibitor of Endothelial Lipase Suppresses Triple-Negative Breast Cancer Cells by Hijacking the Mitochondrial Function

Simple Summary

Endothelial lipase (EL/LIPG) is a key regulator of tumor cell metabolism. In triple-negative breast cancer (TNBC) cells, we find that the expression of LIPG is associated with long non-coding RNA DANCR and positively correlates with gene signatures of mitochondrial metabolism-oxidative phosphorylation (OXPHOS). DANCR binds to LIPG, which enables tumor cells to maintain the expression. Importantly, LIPG knockdown inhibits OXPHOS and TNBC tumor formation. Finally, our study identifies a natural compound, the LIPG inhibitor cynaroside, which provides a new therapeutic strategy against TNBC.

Abstract

Triple-negative breast cancer (TNBC) cells reprogram their metabolism to provide metabolic flexibility for tumor cell growth and survival in the tumor microenvironment. While our previous findings indicated that endothelial lipase (EL/LIPG) is a hallmark of TNBC, the precise mechanism through which LIPG instigates TNBC metabolism remains undefined. Here, we report that the expression of LIPG is associated with long non-coding RNA DANCR and positively correlates with gene signatures of mitochondrial metabolism-oxidative phosphorylation (OXPHOS). DANCR binds to LIPG, enabling tumor cells to maintain LIPG protein stability and OXPHOS. As one mechanism of LIPG in the regulation of tumor cell oxidative metabolism, LIPG mediates histone deacetylase 6 (HDAC6) and histone acetylation, which contribute to changes in IL-6 and fatty acid synthesis gene expression. Finally, aided by a relaxed docking approach, we discovered a new LIPG inhibitor, cynaroside, that effectively suppressed the enzyme activity and DANCR in TNBC cells. Treatment with cynaroside inhibited the OXPHOS phenotype of TNBC cells, which severely impaired tumor formation. Taken together, our study provides mechanistic insights into the LIPG modulation of mitochondrial metabolism in TNBC and a proof-of-concept that targeting LIPG is a promising new therapeutic strategy for the treatment of TNBC.

The role of liver kinase B1 in tumor progression through regulation of lipid metabolism

The somatic mutation of liver kinase B1 (LKB1) has been implicated in various tumors, which is reflected in the survival, proliferation, and metastasis of tumor cells. However, the regulation of LKB1 in lipid metabolism, a process that is involved in tumor progression is not completely clear. We conclude that LKB1 deficiency results in abnormal expression and activation of multiple molecules related to lipid metabolism which locate downstream of AMP-activated protein kinase (AMPK) or salt-induced kinase (SIK). Abnormal lipid metabolism induced by LKB1 deficiency contributes to the proliferation and metastasis of tumor cells through energy regulation.

CPT1A-mediated fatty acid oxidation promotes cell proliferation via nucleoside metabolism in nasopharyngeal carcinoma

As the first rate-limiting enzyme in fatty acid oxidation (FAO), CPT1 plays a significant role in metabolic adaptation in cancer pathogenesis. FAO provides an alternative energy supply for cancer cells and is required for cancer cell survival. Given the high proliferation rate of cancer cells, nucleotide synthesis gains prominence in rapidly proliferating cells. In the present study, we found that CPT1A is a determining factor for the abnormal activation of FAO in nasopharyngeal carcinoma (NPC) cells. CPT1A is highly expressed in NPC cells and biopsies. CPT1A dramatically affects the malignant phenotypes in NPC, including proliferation, anchorage-independent growth, and tumor formation ability in nude mice. Moreover, an increased level of CPT1A promotes core metabolic pathways to generate ATP, inducing equivalents and the main precursors for nucleotide biosynthesis. Knockdown of CPT1A markedly lowers the fraction of ¹³C-palmitate-derived carbons into pyrimidine. Periodic activation of CPT1A increases the content of nucleoside metabolic intermediates promoting cell cycle progression in NPC cells. Targeting CPT1A-mediated FAO hinders the cell cycle G1/S transition. Our work verified that CPT1A links FAO to cell cycle progression in NPC cellular proliferation, which supplements additional experimental evidence for developing a therapeutic mechanism based on manipulating lipid metabolism.

CPT1A and fatty acid β-oxidation are essential for tumor cell growth and survival in hormone receptor-positive breast cancer

Chromosome 11q13-14 amplification is a defining feature of high-risk hormone receptor-positive (HR+) breast cancer; however, the mechanism(s) by which this amplicon contributes to breast tumorigenesis remains unclear. In the current study, proteogenomic analyses of >3000 breast tumors from the TCGA, METABRIC and CPTAC studies demonstrated that carnitine palmitoyltransferase 1A (CPT1A), which is localized to this amplicon, is overexpressed at the mRNA and protein level in aggressive luminal tumors, strongly associated with indicators of tumor proliferation and a predictor of poor prognosis. In vitro genetic studies demonstrated that CPT1A is required for and can promote luminal breast cancer proliferation, survival, as well as colony and mammosphere formation. Since CPT1A is the rate-limiting enzyme during fatty acid oxidation (FAO), our data indicate that FAO may be essential for these tumors. Pharmacologic inhibition of FAO prevented in vitro and in vivo tumor growth and cell proliferation as well as promoted apoptosis in luminal breast cancer cells and orthotopic xenograft tumor models. Collectively, our data establish an oncogenic role for CPT1A and FAO in HR+ luminal tumors and provide preclinical evidence and rationale supporting further investigation of FAO as a potential therapeutic opportunity for the treatment of HR+ breast cancer.

Multi-Omic Approaches to Breast Cancer Metabolic Phenotyping: Applications in Diagnosis, Prognosis, and the Development of Novel Treatments

Breast cancer (BC) is characterized by high disease heterogeneity and represents the most frequently diagnosed cancer among women worldwide. Complex and subtype-specific gene expression alterations participate in disease development and progression, with BC cells known to rewire their cellular metabolism to survive, proliferate, and invade. Hence, as an emerging cancer hallmark, metabolic reprogramming holds great promise for cancer diagnosis, prognosis, and treatment. Multi-omics approaches (the combined analysis of various types of omics data) offer opportunities to advance our understanding of the molecular changes underlying metabolic rewiring in complex diseases such as BC. Recent studies focusing on the combined analysis of genomics, epigenomics, transcriptomics, proteomics, and/or metabolomics in different BC subtypes have provided novel insights into the specificities of metabolic rewiring and the vulnerabilities that may guide therapeutic development and improve patient outcomes. This review summarizes the findings of multi-omics studies focused on the characterization of the specific metabolic phenotypes of BC and discusses how they may improve clinical BC diagnosis, subtyping, and treatment.

The role and therapeutic implication of CPTs in fatty acid oxidation and cancers progression

Cancer cells must maintain metabolic homeostasis under a wide range of conditions and meet their own energy needs in order to survive and reproduce. In addition to glycolysis, cancer cells can also perform various metabolic strategies, such as fatty acid oxidation (FAO). It has been found that the proliferation, survival, drug resistance and metastasis of cancer cells depend on FAO. The carnitine palmitoyltransferase (CPT), including CPT1 and CPT2, located on the mitochondrial membrane, are important mediators of FAO. In recent years, many researchers have found that CPT has a close relationship with the metabolic development of tumor cells, not only provides energy for cancer cells development and metastasis by promoting FAO but also affects the occurrence and invasion through other signal pathways or cytokines or microRNA. This review summarized the role of CPTs in several kinds of tumors and the developed targeted inhibitors of CPTs, as well as the potential gene therapy and immunotherapy of CPTs, hoping to better explore the mechanism and role of CPTs in the future and providing useful ideas for clinical treatment.

Carnitine palmitoyl transferase 1A is a novel diagnostic and predictive biomarker for breast cancer

BACKGROUND

Carnitine palmitoyl transferase 1A (CPT1A), the key regulator of fatty acid oxidation, contributes to tumor metastasis and therapeutic resistance. We aimed to identify its clinical significance as a biomarker for the diagnosis and prediction of breast cancer.

METHODS

Western blot, ELISA and in silico analysis were used to confirm CPT1A levels in breast cancer cell lines, cell culture medium and breast cancer tissues. Four hundred thirty breast cancer patients, 200 patients with benign breast disease, and 400 healthy controls were enrolled and randomly divided into a training set and a test set with a 7:3 ratio. Training set was used to build diagnostic models and 10-fold cross validation was used to demonstrate the performance of the models. Then test set was aimed to validate the effectiveness of the diagnostic models. ELISA was conducted to detect individual serum CPT1A levels. Receiver operating characteristic (ROC) curves were generated, and binary logistic regression analyses were performed to evaluate the effectiveness of CPT1A as a biomarker in breast cancer diagnosis. CPT1A levels between post-operative and pre-operative samples were also compared.

RESULTS

CPT1A was overexpressed in breast cancer tissues, cell lines and cell culture medium. Serum CPT1A levels were higher in breast cancer patients than in controls and were significantly associated with metastasis, TNM stage, histological grading and molecular subtype. CPT1A levels were decreased in post-operative samples compared with paired pre-operative samples. Moreover, CPT1A exhibited a higher efficacy in differentiating breast cancer patients from healthy controls (training set: area under the curve, AUC, 0.892, 95% CI, 0.872-0.920; test set, AUC, 0.904, 95% CI, 0.869-0.939) than did CA15-3, CEA, or CA125.

CONCLUSION

CPT1A is overexpressed in breast cancer and can be secreted out of breast cancer cell. Serum CPT1A is positively associated with breast cancer progression and could serve as an indicator for disease monitoring. Serum CPT1A displayed a remarkably high diagnostic efficiency for breast cancer and could be a novel biomarker for the diagnosis of breast cancer.

The metabolism of cancer cells during metastasis

Metastasis formation is the major cause of death in most patients with cancer. Despite extensive research, targeting metastatic seeding and colonization is still an unresolved challenge. Only recently, attention has been drawn to the fact that metastasizing cancer cells selectively and dynamically adapt their metabolism at every step during the metastatic cascade. Moreover, many metastases display different metabolic traits compared with the tumours from which they originate, enabling survival and growth in the new environment. Consequently, the stage-dependent metabolic traits may provide therapeutic windows for preventing or reducing metastasis, and targeting the new metabolic traits arising in established metastases may allow their eradication.

ACSS3 represses prostate cancer progression through downregulating lipid droplet-associated protein PLIN3

Current endocrine therapy for prostate cancer (PCa) mainly inhibits androgen/androgen receptor (AR) signaling. However, due to increased intratumoural androgen synthesis and AR variation, PCa progresses to castration-resistant prostate cancer (CRPC), which ultimately becomes resistant to endocrine therapy. A search for new therapeutic perspectives is urgently needed. Methods: By screening lipid metabolism-related gene sets and bioinformatics analysis in prostate cancer database, we identified the key lipid metabolism-related genes in PCa. Bisulfite genomic Sequence Polymerase Chain Reaction (PCR) (BSP) and Methylation-Specific Polymerase Chain Reaction (PCR) (MSP) were preformed to detect the promoter methylation of ACSS3. Gene expression was analyzed by qRT-PCR, Western blotting, IHC and co-IP. The function of ACSS3 in PCa was measured by CCK-8, Transwell assays. LC/MS, Oil Red O assays and TG and cholesterol measurement assays were to detect the levels of TG and cholesterol in cells. Resistance to Enzalutamide in C4-2 ENZR cells was examined in a xenograft tumorigenesis model in vivo. Results: We found that acyl-CoA synthetase short chain family member 3 (ACSS3) was downregulated and predicted a poor prognosis in PCa. Loss of ACSS3 expression was due to gene promoter methylation. Restoration of ACSS3 expression in PCa cells significantly reduced LD deposits, thus promoting apoptosis by increasing endoplasmic reticulum (ER) stress, and decreasing de novo intratumoral androgen synthesis, inhibiting CRPC progression and reversing Enzalutamide resistance. Mechanistic investigations demonstrated that ACSS3 reduced LD deposits by regulating the stability of the LD coat protein perilipin 3 (PLIN3). Conclusions: Our study demonstrated that ACSS3 represses prostate cancer progression through downregulating lipid droplet-associated protein PLIN3.

Vascular endothelial growth factor encoded by Parapoxviruses can regulate metabolism and survival of triple negative breast cancer cells

Dysbiotic microbiomes are linked to many pathological outcomes including different metabolic disorders like diabetes, atherosclerosis and even cancer. Breast cancer is the second leading cause of cancer associated death in women, and triple negative breast cancer (TNBC) is the most aggressive type with major challenges for intervention. Previous reports suggested that Parapoxvirus signatures are one of the predominant dysbiotic viral signatures in TNBC. These viruses encode several genes that are homologs of human genes. In this study, we show that the VEGF homolog encoded by Parapoxviruses, can induce cell proliferation, and alter metabolism of breast cancer and normal breast cells, through alteration of MAPK-ERK and PI3K-AKT signaling. In addition, the activity of the transcription factor FoxO1 was altered by viral-encoded VEGF through activation of the PI3K-AKT pathway, leading to reprogramming of cellular metabolic gene expression. Therefore, this study provides new insights into the function of viral-encoded VEGFs, which promoted the growth of the breast cancer cells and imparted proliferative phenotype with altered metabolism in normal breast cells.

Insights into the Role of microRNAs in Colorectal Cancer (CRC) Metabolism

Colorectal cancer (CRC) is one of the most frequently diagnosed cancers, with a high mortality rate globally. The pathophysiology of CRC is mainly initiated by alteration in gene expression, leading to dysregulation in multiple signalling pathways and cellular processes. Metabolic reprogramming is one of the important cancer hallmarks in CRC, which involves the adaptive changes in tumour cell metabolism to sustain the high energy requirements for rapid cell proliferation. There are several mechanisms in the metabolic reprogramming of cancer cells, such as aerobic glycolysis, oxidative phosphorylation, lactate and fatty acids metabolism. MicroRNAs (miRNAs) are a class of non-coding RNAs that are responsible for post-transcriptional regulation of gene expression. Differential expression of miRNAs has been shown to play an important role in different aspects of tumorigenesis, such as proliferation, apoptosis, and drug resistance, as well as metabolic reprogramming. Increasing evidence also reports that miRNAs could function as potential regulators of metabolic reprogramming in CRC cells. This review provides an insight into the role of different miRNAs in regulating the metabolism of CRC cells as well as to discuss the potential role of miRNAs as biomarkers or therapeutic targets in CRC tumour metabolism.

Metabolic Remodeling Induced by Adipocytes: A New Achilles' Heel in Invasive Breast Cancer?

Metabolic reprogramming represents an important hallmark of cancer cells. Besides de novo fatty acid synthesis, it is now clear that cancer cells can acquire Fatty Acids (FA) from tumor-surrounding adipocytes to increase their invasive capacities. Indeed, adipocytes release FA in response to tumor secreted factors that are transferred to tumor cells to be either stored as triglycerides and other complex lipids or oxidized in mitochondria. Like all cells, FA can be released over time from triglyceride stores through lipolysis and then oxidized in mitochondria in cancer cells. This metabolic interaction results in specific metabolic remodeling in cancer cells, and underpins adipocyte stimulated tumor progression. Lipolysis and fatty acid oxidation therefore represent novel targets of interest in the treatment of cancer. In this review, we summarize the recent advances in our understanding of the metabolic reprogramming induced by adipocytes, with a focus on breast cancer. Then, we recapitulate recent reports studying the effect of lipolysis and fatty acid oxidation inhibitors on tumor cells and discuss the interest to target these metabolic pathways as new therapeutic approaches for cancer.

Sodium Butyrate-Modulated Mitochondrial Function in High-Insulin Induced HepG2 Cell Dysfunction

The liver plays a pivotal role in maintaining euglycemia. Biogenesis and function of mitochondria within hepatocytes are often the first to be damaged in a diabetic population, and restoring its function is recently believed to be a promising strategy on inhibiting the progression of diabetes. Previously, we demonstrated that the gut microbiota metabolite butyrate could reduce hyperglycemia and modulate the metabolism of glycogen in both db/db mice and HepG2 cells. To further explore the mechanism of butyrate in controlling energy metabolism, we investigated its influence and underlying mechanism on the biogenesis and function of mitochondria within high insulin-induced hepatocytes in this study. We found that butyrate significantly modulated the expression of 54 genes participating in mitochondrial energy metabolism by a PCR array kit, both the content of mitochondrial DNA and production of ATP were enhanced, expressions of histone deacetylases 3 and 4 were inhibited, beta-oxidation of fatty acids was increased, and oxidative stress damage was ameliorated at the same time. A mechanism study showed that expression of GPR43 and its downstream protein beta-arrestin2 was increased on butyrate administration and that activation of Akt was inhibited, while the AMPK-PGC-1alpha signaling pathway and expression of p-GSK3 were enhanced. In conclusion, we found in the present study that butyrate could significantly promote biogenesis and function of mitochondria under high insulin circumstances, and the GPR43-β-arrestin2-AMPK-PGC1-alpha signaling pathway contributed to these effects. Our present findings will bring new insight on the pivotal role of metabolites from microbiota on maintaining euglycemia in diabetic population.

Mass spectrometry imaging-based metabolomics to visualize the spatially resolved reprogramming of carnitine metabolism in breast cancer

New insights into tumor-associated metabolic reprogramming have provided novel vulnerabilities that can be targeted for cancer therapy. Here, we propose a mass spectrometry imaging (MSI)-based metabolomic strategy to visualize the spatially resolved reprogramming of carnitine metabolism in heterogeneous breast cancer. Methods: A wide carnitine coverage MSI method was developed to investigate the spatial alternations of carnitines in cancer tissues of xenograft mouse models and human samples. Spatial expression of key metabolic enzymes that are closely associated with the altered carnitines was examined in adjacent cancer tissue sections. Results: A total of 17 carnitines, including L-carnitine, 6 short-chain acylcarnitines, 3 middle-chain acylcarnitines, and 7 long-chain acylcarnitines were imaged. L-carnitine and short-chain acylcarnitines are significantly reprogrammed in breast cancer. A classification model based on the carnitine profiles of 170 cancer samples and 128 normal samples enables an accurate identification of breast cancer. CPT 1A, CPT 2, and CRAT, which are extensively involved in carnitine system-mediated fatty acid β-oxidation pathway were also found to be abnormally expressed in breast cancer. Remarkably, the expressions of CPT 2 and CRAT were found for the first time to be altered in breast cancer. Conclusion: These data not only expand our understanding of the complex tumor metabolic reprogramming, but also provide the first evidence that carnitine metabolism is reprogrammed at both the metabolite and enzyme levels in breast cancer.

Tissue-based metabolomics reveals potential biomarkers for cervical carcinoma and HPV infection

Aberrant metabolic regulation has been observed in human cancers, but the corresponding regulation in human papillomavirus (HPV) infection-associated cervical cancer is not well understood. Here, we explored potential biomarkers for the early prediction of cervical carcinoma based on the metabolic profile of uterine cervical tissue specimens that were positive for HPV16 infection. Fifty-two fresh cervical tissues were collected from women confirmed to have cervical squamous cell carcinoma (SCC; n = 21) or cervical intraepithelial neoplasia (CIN) stages II-III (n = 20). Eleven healthy women constituted the controls (negative controls [NCs]). Real-time polymerase chain reaction (PCR) was performed to detect HPV infection in the tissues. High-resolution magic angle spinning nuclear magnetic resonance was utilized for the analysis of the metabolic profile in the tissues. The expression of rate-limiting enzymes involved in key metabolic pathways was detected by reverse-transcription quantitative PCR. An independent immunohistochemical analysis was performed using 123 cases of paraffin-embedded cervical specimens. A profile of 17 small molecular metabolites that showed differential expression in HPV16-positive cervical SCC or CIN II-III compared with HPV-negative NC group was identified. According to the profile, the levels of α- and β-glucose decreased, those of lactate and low-density lipoproteins increased, and the expression of multiple amino acids was altered. Significantly increased transcript and protein levels of glycogen synthase kinase 3 beta (GSK3β) and glutamate decarboxylase 1 (GAD1) and decreased transcript and protein levels of pyruvate kinase muscle isozyme 2 (PKM2) and carnitine palmitoyltransferase 1A (CPT1A) were observed in the patient group (p < 0.05). HPV infection and cervical carcinogenesis drive metabolic modifications that might be associated with the aberrant regulation of enzymes related to metabolic pathways.

Lung cancer cells survive epidermal growth factor receptor tyrosine kinase inhibitor exposure through upregulation of cholesterol synthesis

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) provide clinical benefits over chemotherapy for lung cancer patients with EGFR activating mutations. Despite initial clinical responses, long-term efficacy is not possible because of acquired resistance to these therapies. We have developed EGFR TKI drug-tolerant (DT) human lung cancer cell lines as a model for de novo resistance. Mass spectroscopic analysis revealed that the cytochrome P450 protein, CYP51A1 (Lanosterol 14α-demethylase), which is directly involved with cholesterol synthesis, was significantly upregulated in the DT cells. Total cellular cholesterol, and more specifically, mitochondrial cholesterol, were found to be upregulated in DT cells. We then used the CYP51A1 inhibitor, ketoconazole, to downregulate cholesterol synthesis. In both parental and DT cells, ketoconazole and EGFR TKIs acted synergistically to induce apoptosis and overcome the development of EGFR tolerance. Lastly, this combination therapy was shown to shrink the growth of tumors in an in vivo mouse model of EGFR TKI resistance. Thus, our study demonstrates for the first time that ketoconazole treatment inhibits upregulation of mitochondrial cholesterol and thereby overcomes EGFR-TKI resistance in lung cancer cells.

MYC regulates fatty acid metabolism through a multigenic program in claudin-low triple negative breast cancer

Background

Recent studies have suggested that fatty acid oxidation (FAO) is a key metabolic pathway for the growth of triple negative breast cancers (TNBCs), particularly those that have high expression of MYC. However, the underlying mechanism by which MYC promotes FAO remains poorly understood.

Methods

We used a combination of metabolomics, transcriptomics, bioinformatics, and microscopy to elucidate a potential mechanism by which MYC regulates FAO in TNBC.

Results

We propose that MYC induces a multigenic program that involves changes in intracellular calcium signalling and fatty acid metabolism. We determined key roles for fatty acid transporters (CD36), lipases (LPL), and kinases (PDGFRB, CAMKK2, and AMPK) that each contribute to promoting FAO in human mammary epithelial cells that express oncogenic levels of MYC. Bioinformatic analysis further showed that this multigenic program is highly expressed and predicts poor survival in the claudin-low molecular subtype of TNBC, but not other subtypes of TNBCs, suggesting that efforts to target FAO in the clinic may best serve claudin-low TNBC patients.

Conclusion

We identified critical pieces of the FAO machinery that have the potential to be targeted for improved treatment of patients with TNBC, especially the claudin-low molecular subtype.

Long non‑coding RNA nuclear paraspeckle assembly transcript 1 interacts with microRNA‑107 to modulate breast cancer growth and metastasis by targeting carnitine palmitoyltransferase‑1

Previous studies revealed that the long non‑coding RNA nuclear paraspeckle assembly transcript 1 (NEAT1) exhibits abnormal expression in numerous cancer types, including breast cancer (BC); however, the regulatory mechanism of NEAT1 in BC remains unclear. In the present study, the effect of NEAT1 on the progression of BC and its regulation mechanism was investigated. The expression levels of NEAT1 and microRNA‑107 (miR‑107) in BC cells were analyzed using the reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR). NEAT1 was knocked down in BC cells, and mimics‑miR‑107 or inhibitor‑miR‑107 were transfected into BC cells. Subsequently, cell proliferation, invasion and migration, apoptosis and cell cycle distribution were determined. The regulatory mechanism of NEAT1, miR‑107 and carnitine palmitoyltransferase‑1 (CPT1A) was analyzed using a luciferase reporter assay system, western blotting and RT‑qPCR. NEAT1 expression was increased in BC cells, whereas miR‑107 expression was decreased, compared with normal mammary gland cells. NEAT1 promoted the progression of BC cells through inhibiting apoptosis‑associated genes and promoting cell cycle‑ and invasion‑associated gene expression, whereas miR‑107 served the opposite function. Furthermore, NEAT1 promoted the expression of CPT1A, which was mediated by miR‑107. The results of the present study indicate that NEAT1 promotes the expression of CPT1A by inhibiting miR‑107 to improve the progression of BC cells; therefore, NEAT1 is a potential therapeutic target of BC.

Ginkgolide C reduced oleic acid-induced lipid accumulation in HepG2 cells

Ginkgolide C, isolated from Ginkgo biloba, is a diterpene lactone that has multiple biological functions and can improve Alzheimer disease and platelet aggregation. Ginkgolide C also inhibits adipogenesis in 3T3-L1 adipocytes. The present study evaluated whether ginkgolide C reduced lipid accumulation and regulated the molecular mechanism of lipogenesis in oleic acid-induced HepG2 hepatocytes. HepG2 cells were treated with 0.5 mM oleic acid for 48 h to induce a fatty liver cell model. Then, the cells were exposed to various concentrations of ginkgolide C for 24 h. Staining with Oil Red O and the fluorescent dye BODIPY 493/503 revealed that ginkgolide C significantly reduced excessive lipid accumulation in HepG2 cells. Ginkgolide C decreased peroxisome proliferator-activated receptor γ and sterol regulatory element-binding protein 1c to block the expression of fatty acid synthase. Ginkgolide C treatment also promoted the expression of adipose triglyceride lipase and the phosphorylation level of hormone-sensitive lipase to enhance the decomposition of triglycerides. In addition, ginkgolide C stimulated CPT-1 to activate fatty acid β-oxidation, significantly increased sirt1 and phosphorylation of AMP-activated protein kinase (AMPK), and decreased expression of acetyl-CoA carboxylase for suppressed fatty acid synthesis in hepatocytes. Taken together, our results suggest that ginkgolide C reduced lipid accumulation and increased lipolysis through the sirt1/AMPK pathway in oleic acid-induced fatty liver cells.

Differential Impact of Flavonoids on Redox Modulation, Bioenergetics, and Cell Signaling in Normal and Tumor Cells: A Comprehensive Review

SIGNIFICANCE

Flavonoids can interact with multiple molecular targets to elicit their cellular effects, leading to changes in signal transduction, gene expression, and/or metabolism, which can, subsequently, affect the entire cell and organism. Immortalized cell lines, derived from tumors, are routinely employed as a surrogate for mechanistic studies, with the results extrapolated to tissues in vivo. Recent Advances: We review the activities of selected flavonoids on cultured tumor cells derived from various tissues in comparison to corresponding primary cells or tissues in vivo, mainly using quercetin and flavanols (epicatechin and (-)-epigallocatechin gallate) as exemplars. Several studies have indicated that flavonoids could retard cancer progression in vivo in animal models as well as in tumor cell models.

CRITICAL ISSUES

Extrapolation from in vitro and animal models to humans is not straightforward given both the extensive conjugation and complex microbiota-dependent metabolism of flavonoids after consumption, as well as the heterogeneous metabolism of different tumors.

FUTURE DIRECTIONS

Comparison of data from studies on primary cells or in vivo are essential not only to validate results obtained from cultured cell models, but also to highlight whether any differences may be further exploited in the clinical setting for chemoprevention. Tumor cell models can provide a useful mechanistic tool to study the effects of flavonoids, provided that the limitations of each model are understood and taken into account in interpretation of the data.

A System-wide Approach to Monitor Responses to Synergistic BRAF and EGFR Inhibition in Colorectal Cancer Cells

Intrinsic and/or acquired resistance represents one of the great challenges in targeted cancer therapy. A deeper understanding of the molecular biology of cancer has resulted in more efficient strategies, where one or multiple drugs are adopted in novel therapies to tackle resistance. This beneficial effect of using combination treatments has also been observed in colorectal cancer patients harboring the BRAF(V600E) mutation, whereby dual inhibition of BRAF(V600E) and EGFR increases antitumor activity. Notwithstanding this success, it is not clear whether this combination treatment is the only or most effective treatment to block intrinsic resistance to BRAF inhibitors. Here, we investigate molecular responses upon single and multi-target treatments, over time, using BRAF(V600E) mutant colorectal cancer cells as a model system. Through integration of transcriptomic, proteomic and phosphoproteomics data we obtain a comprehensive overview, revealing both known and novel responses. We primarily observe widespread up-regulation of receptor tyrosine kinases and metabolic pathways upon BRAF inhibition. These findings point to mechanisms by which the drug-treated cells switch energy sources and enter a quiescent-like state as a defensive response, while additionally compensating for the MAPK pathway inhibition.

Challenges and perspectives in the treatment of diabetes associated breast cancer

Type 2 diabetes mellitus is one of the most common chronic disease worldwide and affects all cross-sections of the society including children, women, youth and adults. Scientific evidence has linked diabetes to higher incidence, accelerated progression and increased aggressiveness of different cancers. Among the different forms of cancer, research has reinforced a link between diabetes and the risk of breast cancer. Some studies have specifically linked diabetes to the highly aggressive, triple negative breast cancers (TNBCs) which do not respond to conventional hormonal/HER2 targeted interventions, have chances of early recurrence, metastasize, tend to be more invasive in nature and develop drug resistance. Commonly used anti-diabetic drugs, such as metformin, have recently gained importance in the treatment of breast cancer due to their proposed anti-cancer properties. Here we discuss the link between diabetes and breast cancer, the metabolic disturbances in diabetes that support the development of breast cancer, the challenges involved and future perspective and directions. We link the three main metabolic disturbances (dyslipidemia, hyperinsulinemia and hyperglycemia) that occur in diabetes to potential aberrant molecular pathways that may lead to the development of an oncogenic phenotype of the breast tissue, thereby leading to acceleration of cell growth, proliferation, migration, inflammation, angiogenesis, EMT and metastasis and inhibition of apoptosis in breast cancer cells. Furthermore, managing diabetes and treating cancer using a combination of anti-diabetic and classical anti-cancer drugs should prove to be more efficient in the treatment diabetes associated cancers.

When fats commit crimes: fatty acid metabolism, cancer stemness and therapeutic resistance

The role of fatty acid metabolism, including both anabolic and catabolic reactions in cancer has gained increasing attention in recent years. Many studies have shown that aberrant expression of the genes involved in fatty acid synthesis or fatty acid oxidation correlate with malignant phenotypes including metastasis, therapeutic resistance and relapse. Such phenotypes are also strongly associated with the presence of a small percentage of unique cells among the total tumor cell population. This distinct group of cells may have the ability to self-renew and propagate or may be able to develop resistance to cancer therapies independent of genetic alterations. Therefore, these cells are referred to as cancer stem cells/tumor-initiating cells/drug-tolerant persisters, which are often refractory to cancer treatment and difficult to target. Moreover, interconversion between cancer cells and cancer stem cells/tumor-initiating cells/drug-tolerant persisters may occur and makes treatment even more challenging. This review highlights recent findings on the relationship between fatty acid metabolism, cancer stemness and therapeutic resistance and prompts discussion about the potential mechanisms by which fatty acid metabolism regulates the fate of cancer cells and therapeutic resistance.

Protective Effect of Glycyrrhizic Acid on Alcoholic Liver Injury in Rats by Modulating Lipid Metabolism

Glycyrrhhizic acid (GA), including 18α-glycyrrhizic acid (18α-GA) and 18β-glycyrrhizic acid (18β-GA), is the main active ingredient of licorice. GA is generally considered an effective pharmacological strategy protecting against hepatic disease; however, the optimal compatibility proportion of 18α-GA and 18β-GA against alcoholic liver disease (ALD) and the underlying mechanism are not well established. Hence, this study was designed to explore the optimal compatibility proportion of 18α-GA and 18β-GA against ALD, followed by investigating the underlying mechanisms. SD rats were administered 40% ethanol once a day, accompanied by treatment with different proportions of 18α-GA and 18β-GA for four weeks. Then all rats were anesthetized with chloral hydrate and blood samples were taken from the abdominal aorta for biochemical assay. Livers were also collected and the liver function, lipid profile, ROS production, and mRNA and protein levels of related genes involved in lipid metabolism were assessed. The results showed that 18α-GA and 18β-GA, particularly at a proportion of 4:6, significantly reduced liver damage, lipid accumulation, and oxidative stress in ethanol-induced rats, as indicated by the decreased levels of alanine aminotransferase (ALT) and aminotransferase (AST) in serum, improvement of liver histopathological changes, regulation of total cholesterol (TC), total triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C), and modulation of superoxide dismutase (SOD), glutathione (GSH), and malonaldehyde (MDA). Moreover, the combination treatment with 18α-GA and 18β-GA substantially reduced the mRNA and protein levels of sterol regulatory element-binding protein-1c (SREBP-1c) and acetyl-coal carboxylase (ACC); meanwhile, increased levels of peroxisome proliferators activated receptor-α (PPAR-α) and carnitine palmitoy transferase-1 (CTP-1) in the liver tissues of ethanol-induced rats. In conclusion, our results indicated that the optimal compatibility proportion of 18α-GA and 18β-GA protecting against ALD was 4:6, and the mechanism was associated with the regulation of oxidative stress and lipid metabolism.

CPT1A regulates breast cancer-associated lymphangiogenesis via VEGF signaling

BACKGROUND

Lymphangiogenesis is critical for metastasis of a variety of cancers, including breast cancer. CPT1A (carnitine palmitoyltransferase 1a) has been reported to play a critical role in breast cancer progress. However, the molecular mechanism remains elusive.

METHODS

In order to investigate the role of CPT1A in HDLEC cells, short hairpin RNA approach was utilized to knock down the CPT1A gene expression. We employed transwell and lymphatic vessel formation assay to examine invasion and lymphangiogenesis of HDLEC (Human dermal lymphatic endothelial cells). RT-qPCR and westernblot analyses were used to determine genes expression in HDLEC and breast cancer cells. Finally, we determined the relative rate of acetyl-CoA/CoA in shNC and shCPT1A HDLEC cells by LC-MS approach.

RESULTS

Knockdown of CPT1A in breast cancer cells (MCF-7 and MDA-MB-231) abolished invasion and lymphangiogenesis of HDLEC cells. Mechanistically, CPT1A depletion suppressed the expression of VEGF-C and VEGF-D in MCF-7 and MDA-MB-231 cells. Interestingly, CPT1A knockdown in HDLEC cells exhibited attenuated expression of lymphangiogenic markers (podoplanin, VEGFR-3, VEGF-C, VEGF-D and PROX-1). Consistently, CPT1A -null HDLEC cells displayed compromised invasion and lymphangiogenesis compared with negative control. Further investigation revealed that CPT1A regulated VEGFR3 via acetyl-CoA mediated H3K9ac, which could be abrogated by supplement of acetate.

CONCLUSIONS

In present study, we revealed the mechanism by which CPT1A regulates breast cancer-associated invasion and lymphangiogenesis. Our findings provide insights into CPT1A -promoted breast tumor metastasis and provide rationale for understanding breast cancer metastasis.

Emerging role of lipid metabolism alterations in Cancer stem cells

BACKGROUND

Cancer stem cells (CSCs) or tumor-initiating cells (TICs) represent a small population of cancer cells with self-renewal and tumor-initiating properties. Unlike the bulk of tumor cells, CSCs or TICs are refractory to traditional therapy and are responsible for relapse or disease recurrence in cancer patients. Stem cells have distinct metabolic properties compared to differentiated cells, and metabolic rewiring contributes to self-renewal and stemness maintenance in CSCs.

MAIN BODY

Recent advances in metabolomic detection, particularly in hyperspectral-stimulated raman scattering microscopy, have expanded our knowledge of the contribution of lipid metabolism to the generation and maintenance of CSCs. Alterations in lipid uptake, de novo lipogenesis, lipid droplets, lipid desaturation, and fatty acid oxidation are all clearly implicated in CSCs regulation. Alterations on lipid metabolism not only satisfies the energy demands and biomass production of CSCs, but also contributes to the activation of several important oncogenic signaling pathways, including Wnt/β-catenin and Hippo/YAP signaling. In this review, we summarize the current progress in this attractive field and describe some recent therapeutic agents specifically targeting CSCs based on their modulation of lipid metabolism.

CONCLUSION

Increased reliance on lipid metabolism makes it a promising therapeutic strategy to eliminate CSCs. Targeting key players of fatty acids metabolism shows promising to anti-CSCs and tumor prevention effects.

Carnitine palmitoyltransferase gene upregulation by linoleic acid induces CD4+ T cell apoptosis promoting HCC development

Hepatocellular carcinoma (HCC) is a common cause of cancer-related death worldwide. As obesity and diabetes become more prevalent, the contribution of non-alcoholic fatty liver disease (NAFLD) to HCC is rising. Recently, we reported intrahepatic CD4⁺ T cells are critical for anti-tumor surveillance in NAFLD. Lipid accumulation in the liver is the hallmark of NAFLD, which may perturb T cell function. We sought to investigate how the lipid-rich liver environment influences CD4⁺ T cells by focusing on carnitine palmitoyltransferase (CPT) family members, which control the mitochondrial β-oxidation of fatty acids and act as key molecules in lipid catabolism. Linoleic acid (C18:2) co-localized within the mitochondria along with a corresponding increase in CPT gene upregulation. This CPT upregulation can be recapitulated by feeding mice with a high-C18:2 diet or the NAFLD promoting methionine-choline-deficient (MCD) diet. Using an agonist and antagonist, the induction of CPT genes was found to be mediated by peroxisome proliferator-activated receptor alpha (PPAR-α). CPT gene upregulation increased mitochondrial reactive oxygen species (ROS) and led to cell apoptosis. In vivo, using liver-specific inducible MYC transgenic mice fed MCD diet, blocking CPT with the pharmacological inhibitor perhexiline decreased apoptosis of intrahepatic CD4⁺ T cells and inhibited HCC tumor formation. These results provide useful information for potentially targeting the CPT family to rescue intrahepatic CD4⁺ T cells and to aid immunotherapy for NAFLD-promoted HCC.

Fatty acid metabolism in breast cancer subtypes

Dysregulation of fatty acid metabolism is recognized as a component of malignant transformation in many different cancers, including breast; yet the potential for targeting this pathway for prevention and/or treatment of cancer remains unrealized. Evidence indicates that proteins involved in both synthesis and oxidation of fatty acids play a pivotal role in the proliferation, migration and invasion of breast cancer cells. The following essay summarizes data implicating specific fatty acid metabolic enzymes in the genesis and progression of breast cancer, and further categorizes the relevance of specific metabolic pathways to individual intrinsic molecular subtypes of breast cancer. Based on mRNA expression data, the less aggressive luminal subtypes appear to rely on a balance between de novo fatty acid synthesis and oxidation as sources for both biomass and energy requirements, while basal-like, receptor negative subtypes overexpress genes involved in the utilization of exogenous fatty acids. With these differences in mind, treatments may need to be tailored to individual subtypes.

Targeting CPT1A-mediated fatty acid oxidation sensitizes nasopharyngeal carcinoma to radiation therapy

Nasopharyngeal carcinoma (NPC) has a particularly high prevalence in southern China, southeastern Asia and northern Africa. Radiation resistance remains a serious obstacle to successful treatment in NPC. This study aimed to explore the metabolic feature of radiation-resistant NPC cells and identify new molecular-targeted agents to improve the therapeutic effects of radiotherapy in NPC. Methods: Radiation-responsive and radiation-resistant NPC cells were used as the model system in vitro and in vivo. Metabolomics approach was used to illustrate the global metabolic changes. ¹³C isotopomer tracing experiment and Seahorse XF analysis were undertaken to determine the activity of fatty acid oxidation (FAO). qRT-PCR was performed to evaluate the expression of essential FAO genes including CPT1A. NPC tumor tissue microarray was used to investigate the prognostic role of CPT1A. Either RNA interference or pharmacological blockade by Etomoxir were used to inhibit CPT1A. Radiation resistance was evaluated by colony formation assay. Mitochondrial membrane potential, apoptosis and neutral lipid content were measured by flow cytometry analysis using JC-1, Annexin V and LipidTOX Red probe respectively. Molecular markers of mitochondrial apoptosis were detected by western blot. Xenografts were treated with Etomoxir, radiation, or a combination of Etomoxir and radiation. Mitochondrial apoptosis and lipid droplets content of tumor tissues were detected by cleaved caspase 9 and Oil Red O staining respectively. Liquid chromatography coupled with tandem mass spectrometry approach was used to identify CPT1A-binding proteins. The interaction of CPT1A and Rab14 were detected by immunoprecipitation, immunofluorescence and in situ proximity ligation analysis. Fragment docking and direct coupling combined computational protein-protein interaction prediction method were used to predict the binding interface. Fatty acid trafficking was measured by pulse-chase assay using BODIPY C16 and MitoTracker Red probe. Results: FAO was active in radiation-resistant NPC cells, and the rate-limiting enzyme of FAO, carnitine palmitoyl transferase 1 A (CPT1A), was consistently up-regulated in these cells. The protein level of CPT1A was significantly associated with poor overall survival of NPC patients following radiotherapy. Inhibition of CPT1A re-sensitized NPC cells to radiation therapy by activating mitochondrial apoptosis both in vitro and in vivo. In addition, we identified Rab14 as a novel CPT1A binding protein. The CPT1A-Rab14 interaction facilitated fatty acid trafficking from lipid droplets to mitochondria, which decreased radiation-induced lipid accumulation and maximized ATP production. Knockdown of Rab14 attenuated CPT1A-mediated fatty acid trafficking and radiation resistance. Conclusion: An active FAO is a vital signature of NPC radiation resistance. Targeting CPT1A could be a beneficial regimen to improve the therapeutic effects of radiotherapy in NPC patients. Importantly, the CPT1A-Rab14 interaction plays roles in CPT1A-mediated radiation resistance by facilitating fatty acid trafficking. This interaction could be an attractive interface for the discovery of novel CPT1A inhibitors.

Novel RNA-Affinity Proteogenomics Dissects Tumor Heterogeneity for Revealing Personalized Markers in Precision Prognosis of Cancer

To discriminate the patient subpopulations with different clinical outcomes within each breast cancer (BC) subtype, we introduce a robust, clinical-practical, activity-based proteogenomic method that identifies, in their oncogenically active states, candidate biomarker genes bearing patient-specific transcriptomic/genomic alterations of prognostic value. First, we used the intronic splicing enhancer (ISE) probes to sort ISE-interacting trans-acting protein factors (trans-interactome) directly from a tumor tissue for subsequent mass spectrometry characterization. In the retrospective, proteogenomic analysis of patient datasets, we identified those ISE trans-factor-encoding genes showing interaction-correlated expression patterns (iCEPs) as new BC-subtypic genes. Further, patient-specific co-alterations in mRNA expression of select iCEP genes distinguished high-risk patient subsets/subpopulations from other patients within a single BC subtype. Function analysis further validated a tumor-phenotypic trans-interactome contained the drivers of oncogenic splicing switches, representing the predominant tumor cells in a tissue, from which novel personalized biomarkers were clinically characterized/validated for precise prognostic prediction and subsequent individualized alignment of optimal therapy.

Identifying off-target effects of etomoxir reveals that carnitine palmitoyltransferase I is essential for cancer cell proliferation independent of β-oxidation

It has been suggested that some cancer cells rely upon fatty acid oxidation (FAO) for energy. Here we show that when FAO was reduced approximately 90% by pharmacological inhibition of carnitine palmitoyltransferase I (CPT1) with low concentrations of etomoxir, the proliferation rate of various cancer cells was unaffected. Efforts to pharmacologically inhibit FAO more than 90% revealed that high concentrations of etomoxir (200 μM) have an off-target effect of inhibiting complex I of the electron transport chain. Surprisingly, however, when FAO was reduced further by genetic knockdown of CPT1, the proliferation rate of these same cells decreased nearly 2-fold and could not be restored by acetate or octanoic acid supplementation. Moreover, CPT1 knockdowns had altered mitochondrial morphology and impaired mitochondrial coupling, whereas cells in which CPT1 had been approximately 90% inhibited by etomoxir did not. Lipidomic profiling of mitochondria isolated from CPT1 knockdowns showed depleted concentrations of complex structural and signaling lipids. Additionally, expression of a catalytically dead CPT1 in CPT1 knockdowns did not restore mitochondrial coupling. Taken together, these results suggest that transport of at least some long-chain fatty acids into the mitochondria by CPT1 may be required for anabolic processes that support healthy mitochondrial function and cancer cell proliferation independent of FAO.