Combined inhibition of glycolysis and AMPK induces synergistic breast cancer cell killing

Metabolic reprogramming in septic acute kidney injury: pathogenesis and therapeutic implications

Acute kidney injury (AKI) is a frequent and severe complication of sepsis and is characterized by significant mortality and morbidity. However, the pathogenesis of septic acute kidney injury (S-AKI) remains elusive. Metabolic reprogramming, which was originally referred to as the Warburg effect in cancer, is strongly related to S-AKI. At the onset of sepsis, both inflammatory cells and renal parenchymal cells, such as macrophages, neutrophils and renal tubular epithelial cells, undergo metabolic shifts toward aerobic glycolysis to amplify proinflammatory responses and fortify cellular resilience to septic stimuli. As the disease progresses, these cells revert to oxidative phosphorylation, thus promoting anti-inflammatory reactions and enhancing functional restoration. Alterations in mitochondrial dynamics and metabolic reprogramming are central to the energetic changes that occur during S-AKI. In this review, we summarize the current understanding of the pathogenesis of metabolic reprogramming in S-AKI, with a focus on each cell type involved. By identifying relevant key regulatory factors, we also explored potential metabolic reprogramming-related therapeutic targets for the management of S-AKI.

Autophagy inhibition potentiates energy restriction-induced cell death in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) significantly contributes to cancer-related mortality due to the limited response of HCC to current anticancer therapies, thereby necessitating more effective treatment approaches. Energy restriction mimetic agents (ERMAs) have emerged as potential therapies in targeting the Warburg effect, a unique metabolic process in cancer cells. However, ERMAs exhibit limited efficacy when used as monotherapy. Additionally, ERMAs have been found to induce autophagy in cancer cells. The role of autophagy in cancer survival remains a subject of debate. Thus, it is crucial to ascertain whether ERMA-induced autophagy is a mechanism for cell survival or cell death in HCC. Our study aims to investigate the effect of autophagy inhibition on the survival of HCC cells treated with ERMAs while also examining the potential of combining an autophagy inhibitor such as spautin-1 with ERMAs to enhance HCC cell death. Our results suggest a cytoprotective role for ERMA-induced autophagy in HCC cells, as combining the autophagy inhibitor spautin-1 with ERMAs effectively suppressed ERMA-induced autophagy and synergistically enhanced their antitumor activity. The treatment combination promoted HCC death through apoptosis, cell cycle arrest, and inhibition of AKT and ERK activation, which are known to play a key role in cellular proliferation. Collectively, our findings highlight a potential strategy to combat HCC by combining energy restriction with autophagy inhibition.

To be or not to be a fat burner, that is the question for cpt1c in cancer cells

There is an urgent need to identify reliable genetic biomarkers for accurate diagnosis, prognosis, and treatment of different tumor types. Described as a prognostic marker for many tumors is the neuronal protein carnitine palmitoyltransferase 1 C (CPT1C). Several studies report that CPT1C is involved in cancer cell adaptation to nutrient depletion and hypoxia. However, the molecular role played by CPT1C in cancer cells is controversial. Most published studies assume that, like canonical CPT1 isoforms, CPT1C is a mediator of fatty acid transport to mitochondria for beta-oxidation, despite the fact that CPT1C has inefficient catalytic activity and is located in the endoplasmic reticulum. In this review, we collate existing evidence on CPT1C in neurons, showing that CPT1C is a sensor of nutrients that interacts with and regulates other proteins involved in lipid metabolism and transport, lysosome motility, and the secretory pathway. We argue, therefore, that CPT1C expression in cancer cells is not a direct regulator of fat burn, but rather is a regulator of lipid metabolic reprograming and cell adaptation to environmental stressors. We also review the clinical relevance of CPT1C as a prognostic indicator and its contribution to tumor growth, cancer invasiveness, and cell senescence. This new and integrated vision of CPT1C function can help better understand the metabolic plasticity of cancer cells and improve the design of therapeutic strategies.

Novel Anti-Cancer Products Targeting AMPK: Natural Herbal Medicine against Breast Cancer

Breast cancer is a common cancer in women worldwide. The existing clinical treatment strategies have been able to limit the progression of breast cancer and cancer metastasis, but abnormal metabolism, immunosuppression, and multidrug resistance involving multiple regulators remain the major challenges for the treatment of breast cancer. Adenosine 5'-monophosphate (AMP)-Activated Protein Kinase (AMPK) can regulate metabolic reprogramming and reverse the "Warburg effect" via multiple metabolic signaling pathways in breast cancer. Previous studies suggest that the activation of AMPK suppresses the growth and metastasis of breast cancer cells, as well as stimulating the responses of immune cells. However, some other reports claim that the development and poor prognosis of breast cancer are related to the overexpression and aberrant activation of AMPK. Thus, the role of AMPK in the progression of breast cancer is still controversial. In this review, we summarize the current understanding of AMPK, particularly the comprehensive bidirectional functions of AMPK in cancer progression; discuss the pharmacological activators of AMPK and some specific molecules, including the natural products (including berberine, curcumin, (-)-epigallocatechin-3-gallate, ginsenosides, and paclitaxel) that influence the efficacy of these activators in cancer therapy; and elaborate the role of AMPK as a potential therapeutic target for the treatment of breast cancer.

Cpt1c Downregulation Causes Plasma Membrane Remodelling and Anthracycline Resistance in Breast Cancer

Breast cancer (BC) is the most common malignancy in women worldwide. While the main systemic treatment option is anthracycline-containing chemotherapy, chemoresistance continues to be an obstacle to patient survival. Carnitine palmitoyltransferase 1C (CPT1C) has been described as a poor-prognosis marker for several tumour types, as it favours tumour growth and hinders cells from entering senescence. At the molecular level, CPT1C has been associated with lipid metabolism regulation and important lipidome changes. Since plasma membrane (PM) rigidity has been associated with reduced drug uptake, we explored whether CPT1C expression could be involved in PM remodelling and drug chemoresistance. Liquid chromatography-high resolution mass spectrometry (LC-HRMS) lipid analysis of PM-enriched fractions of MDA-MB-231 BC cells showed that CPT1C silencing increased PM phospholipid saturation, suggesting a rise in PM rigidity. Moreover, CPT1C silencing increased cell survival against doxorubicin (DOX) treatment in different BC cells due to reduced drug uptake. These findings, further complemented by ROC plotter analysis correlating lower CPT1C expression with a lower pathological complete response to anthracyclines in patients with more aggressive types of BC, suggest CPT1C as a novel predictive biomarker for BC chemotherapy.

AMPK: An odyssey of a metabolic regulator, a tumor suppressor, and now a contextual oncogene

Metabolic reprogramming is a unique but complex biochemical adaptation that allows solid tumors to tolerate various stresses that challenge cancer cells for survival. Under conditions of metabolic stress, mammalian cells employ adenosine monophosphate (AMP)-activated protein kinase (AMPK) to regulate energy homeostasis by controlling cellular metabolism. AMPK has been described as a cellular energy sensor that communicates with various metabolic pathways and networks to maintain energy balance. Earlier studies characterized AMPK as a tumor suppressor in the context of cancer. Later, a paradigm shift occurred in support of the oncogenic nature of AMPK, considering it a contextual oncogene. In support of this, various cellular and mouse models of tumorigenesis and clinicopathological studies demonstrated increased AMPK activity in various cancers. This review will describe AMPK's pro-tumorigenic activity in various malignancies and explain the rationale and context for using AMPK inhibitors in combination with anti-metabolite drugs to treat AMPK-driven cancers.

A Novel Metabolic Reprogramming Strategy for the Treatment of Diabetes-Associated Breast Cancer

Diabetes is directly related to the risk of breast cancer (BC) occurrence and worsened BC prognosis. Currently, there are no specific treatments for diabetes-associated BC. This paper aims to understand the fundamental mechanisms of diabetes-induced BC progression and to develop personalized treatments. It reports a metabolic reprogramming strategy (MRS) that pharmaceutical induction of glucose import and glycolysis with metformin and NF-κB inhibitor (NF-κBi) while blocking the export of excessive lactate via inhibiting monocarboxylate transporter 4 (MCT4) leads to a metabolic crisis within the cancer cells. It demonstrates that the MRS shifts the metabolism of BC cells toward higher production of lactate, blocks lactate secretion, prompts intracellular acidification and induces significant cytotoxicity. Moreover, a novel MCT4 inhibitor CB-2 has been identified by structure-based virtual screening. A triple combination of metformin, CB-2, and trabectedin, a drug that impedes NF-κB signaling, strongly inhibits BC cells. Compared to normal glucose condition, MRS elicits more potent cancer cell-killing effects under high glucose condition. Animal model studies show that diabetic conditions promote the proliferation and progression of BC xenografts in nude mice and that MRS treatment significantly inhibits HG-induced BC progression. Therefore, inhibition of MCT4 combined with metformin/NF-κBi is a promising cancer therapy, especially for diabetes-associated BC.

Breast Cancer Cell Subtypes Display Different Metabolic Phenotypes That Correlate with Their Clinical Classification

Simple Summary

Recent studies on cancer cell metabolism have achieved notable breakthroughs that have led to a new scientific paradigm. How cancer cell metabolic reprogramming is orchestrated and the decisive role of this reprogramming in the oncogenic process and tumor adaptative evolution has been characterized at the molecular level. Despite this knowledge, it is essential to understand how cancer cells can metabolically respond as a living whole to ensure their survival and adaptation potential. In this work, we investigated whether different cancers and different subtypes display different metabolic phenotypes with a focus on breast cancer cell models representative of each clinical subtype. The potential results might have significant translational implications for diagnostic, prognostic and therapeutic applications.

Abstract

Metabolic reprogramming of cancer cells represents an orchestrated network of evolving molecular and functional adaptations during oncogenic progression. In particular, how metabolic reprogramming is orchestrated in breast cancer and its decisive role in the oncogenic process and tumor evolving adaptations are well consolidated at the molecular level. Nevertheless, potential correlations between functional metabolic features and breast cancer clinical classification still represent issues that have not been fully studied to date. Accordingly, we aimed to investigate whether breast cancer cell models representative of each clinical subtype might display different metabolic phenotypes that correlate with current clinical classifications. In the present work, functional metabolic profiling was performed for breast cancer cell models representative of each clinical subtype based on the combination of enzyme inhibitors for key metabolic pathways, and isotope-labeled tracing dynamic analysis. The results indicated the main metabolic phenotypes, so-called ‘metabophenotypes’, in terms of their dependency on glycolytic metabolism or their reliance on mitochondrial oxidative metabolism. The results showed that breast cancer cell subtypes display different metabophenotypes. Importantly, these metabophenotypes are clearly correlated with the current clinical classifications.

AMPK-Mediated Metabolic Switching Is High Effective for Phytochemical Levo-Tetrahydropalmatine (l-THP) to Reduce Hepatocellular Carcinoma Tumor Growth

Targeting cancer cell metabolism has been an attractive approach for cancer treatment. However, the role of metabolic alternation in cancer is still unknown whether it functions as a tumor promoter or suppressor. Applying the cancer gene-metabolism integrative network model, we predict adenosine monophosphate-activated protein kinase (AMPK) to function as a central hub of metabolic landscape switching in specific liver cancer subtypes. For the first time, we demonstrate that the phytochemical levo-tetrahydropalmatine (l-THP), a Corydalis yanhusuo-derived clinical drug, as an AMPK activator via autophagy-mediated metabolic switching could kill the hepatocellular carcinoma HepG2 cells. Mechanistically, l-THP promotes the autophagic response by activating the AMPK-mTOR-ULK1 and the ROS-JNK-ATG cascades and impairing the ERK/AKT signaling. All these processes ultimately synergize to induce the decreased mitochondrial oxidative phosphorylation (OXPHOS) and mitochondrial damage. Notably, silencing AMPK significantly inhibits the autophagic flux and recovers the decreased OXPHOS metabolism, which results in HepG2 resistance to l-THP treatment. More importantly, l-THP potently reduces the growth of xenograft HepG2 tumor in nude mice without affecting other organs. From this perspective, our findings support the conclusion that metabolic change is an alternative approach to influence the development of HCC.

Suppression of ACADM-Mediated Fatty Acid Oxidation Promotes Hepatocellular Carcinoma via Aberrant CAV1/SREBP1 Signaling

Lipid accumulation exacerbates tumor development, as it fuels the proliferative growth of cancer cells. The role of medium-chain acyl-CoA dehydrogenase (ACADM), an enzyme that catalyzes the first step of mitochondrial fatty acid oxidation, in tumor biology remains elusive. Therefore, investigating its mode of dysregulation can shed light on metabolic dependencies in cancer development. In hepatocellular carcinoma (HCC), ACADM was significantly underexpressed, correlating with several aggressive clinicopathologic features observed in patients. Functionally, suppression of ACADM promoted HCC cell motility with elevated triglyceride, phospholipid, and cellular lipid droplet levels, indicating the tumor suppressive ability of ACADM in HCC. Sterol regulatory element-binding protein-1 (SREBP1) was identified as a negative transcriptional regulator of ACADM. Subsequently, high levels of caveolin-1 (CAV1) were observed to inhibit fatty acid oxidation, which revealed its role in regulating lipid metabolism. CAV1 expression negatively correlated with ACADM and its upregulation enhanced nuclear accumulation of SREBP1, resulting in suppressed ACADM activity and contributing to increased HCC cell aggressiveness. Administration of an SREBP1 inhibitor in combination with sorafenib elicited a synergistic antitumor effect and significantly reduced HCC tumor growth in vivo. These findings indicate that deregulation of fatty acid oxidation mediated by the CAV1/SREBP1/ACADM axis results in HCC progression, which implicates targeting fatty acid metabolism to improve HCC treatment. SIGNIFICANCE: This study identifies tumor suppressive effects of ACADM in hepatocellular carcinoma and suggests promotion of β-oxidation to diminish fatty acid availability to cancer cells could be used as a therapeutic strategy.

The role of HIF-1α in BCG-stimulated macrophages polarization and their tumoricidal effects in vitro

BCG is widely used for cancer treatment, where macrophages play an important role. However, the mechanism of BCG affecting macrophages remains poorly understood. In this study, we used BCG to stimulate myeloid-derived macrophages lacking HIF-1α, the levels of TNF-α, IL-1β, CD86 of macrophages and their effects on the growth of tumor cells MCA207 and B16-F10 were detected. We found that the absence of HIF-1α prevents BCG-stimulated macrophages from polarizing towards the M (BCG) and attenuating its killing effect on tumor cells. In addition, we demonstrated that the tumors of mice lacking HIF-1α in macrophages were significantly increased by the experiment of mice transplantation. Our study provides relevant evidence for exploring the mechanism of the BCG vaccine in the prevention and treatment of related diseases.

The rate of aerobic glycolysis is a pivotal regulator of tumor progression

Purpose

Cancer cells depend on glucose metabolism via exclusive glycolysis pathway is named Aerobic glycolysis or Warburg effect. The aim of this study was investigation of different glucose accessibility conditions on the rate of Warburg effect and its impact on Hypoxia inducible factors-1 α (HIF-1 α)/vascular endothelium growth factor (VEGF) pathway in breast cancer cells lines.

Methods

MDA-MB-231 (Warburg phenomenon) and MCF-7 (oxidative) cell lines were cultured in DMEM and exposed to three different glucose accessibility medium for 48 h (5.5 mM as normal glucose (NG), 25 mM as high glucose (HG) and 2-Deoxyglucose (2-DG) as restricted glucose accessibility). Glucose uptake, intra/extracellular lactate and pyruvate, HIF-1α accumulation and vascular endothelium growth factor (VEGF) expression were evaluated by standard methods.

Results

Our results showed in NG condition both of cell lines produce lactate, but it was higher in MDA-MB-231. HG condition increased extracellular lactate in both cell lines especially in MCF-7 cells whereas intracellular lactate and pyruvate raised only in MCF-7. 2-DG decreased extracellular and intracellular lactate and pyruvate in both cell lines especially in MDA-MB-231. HIF-1α accumulation was detectable in NG condition in both cell lines. HG condition increased HIF-1α accumulation in MCF-7 cells but not in MDA-MB-231 and 2-DG decreased it in both call lines, especially in MDA-MB-231. Expression of VEGF had similar pattern with HIF-1α in different conditions.

Conclusions

Our findings revealed the rate of Warburg effect is an important indicator for tumor promotion and invasion due to its impacts on important transcription factors like HIF-1α.

Continuous flow synthesis of lipophilic cations derived from benzoic acid as new cytotoxic chemical entities in human head and neck carcinoma cell lines

Continuous flow chemistry was used for the synthesis of a series of delocalized lipophilic triphenylphosphonium cations (DLCs) linked by means of an ester functional group to several hydroxylated benzoic acid derivatives and evaluated in terms of both reaction time and selectivity. The synthesized compounds showed cytotoxic activity and selectivity in head and neck tumor cell lines. The mechanism of action of the molecules involved a mitochondrial uncoupling effect and a decrease in both intracellular ATP production and apoptosis induction.

Cellular toxicity of the metabolic inhibitor 2-deoxyglucose and associated resistance mechanisms

Most malignant cells display increased glucose absorption and metabolism compared to surrounding tissues. This well-described phenomenon results from a metabolic reprogramming occurring during transformation, that provides the building blocks and supports the high energetic cost of proliferation by increasing glycolysis. These features led to the idea that drugs targeting glycolysis might prove efficient in the context of cancer treatment. One of these drugs, 2-deoxyglucose (2-DG), is a synthetic glucose analog that can be imported into cells and interfere with glycolysis and ATP generation. Its preferential targeting to sites of cell proliferation is supported by the observation that a derived molecule, 2-fluoro-2-deoxyglucose (FDG) accumulates in tumors and is used for cancer imaging. Here, we review the toxicity mechanisms of this drug, from the early-described effects on glycolysis to its other cellular consequences, including inhibition of protein glycosylation and endoplasmic reticulum stress, and its interference with signaling pathways. Then, we summarize the current data on the use of 2-DG as an anti-cancer agent, especially in the context of combination therapies, as novel 2-DG-derived drugs are being developed. We also show how the use of 2-DG helped to decipher glucose-signaling pathways in yeast and favored their engineering for biotechnologies. Finally, we discuss the resistance strategies to this inhibitor that have been identified in the course of these studies and which may have important implications regarding a medical use of this drug.

A novel miR-1291-ERRα-CPT1C axis modulates tumor cell proliferation, metabolism and tumorigenesis

Rationale: MicroRNAs are known to influence the development of a variety of cancers. Previous studies revealed that miR-1291 has antiproliferative functions in cancer cells. Carnitine palmitoyltransferase 1C (CPT1C) has a vital role in mitochondrial energy metabolism and modulation of cancer cell proliferation. Since both miR-1291 and CPT1C regulate tumor cell metabolism and cancer progression, we hypothesized that they might be regulated synergistically. Methods: A series of cell phenotype indicators, such as BrdU, colony formation, cell cycle, ATP production, ROS accumulation and cell ability to resist metabolic stress, were performed to clarify the effects of miR-1291 and ERRα expression on tumor cell proliferation and metabolism. A xenograft tumor model was used to evaluate cell tumorigenesis. Meta-analysis and bioinformatic prediction were applied in the search for the bridge-link between miR-1291 and CPT1C. RT-qPCR, western-blot and IHC analysis were used for the detection of mRNA and protein expression. Luciferase assays and ChIP assays were conducted for in-depth mechanism studies. Results: The expression of miR-1291 inhibited growth and tumorigenesis as a result of modulation of metabolism. CPT1C expression was indirectly and negatively correlated with miR-1291 levels. ESRRA was identified as a prominent differentially expressed gene in both breast and pancreatic cancer samples, and estrogen-related receptor α (ERRα) was found to link miR-1291 and CPT1C. MiR-1291 targeted ERRα and CPT1C was identified as a newly described ERRα target gene. Moreover, ERRα was found to influence cancer cell metabolism and proliferation, consistent with the cellular changes caused by miR-1291. Conclusion: This study demonstrated the existence and mechanism of action of a novel miR-1291-ERRα-CPT1C cancer metabolism axis that may provide new insights and strategies for the development of miRNA-based therapies for malignant cancers.

Disulfide Cleavage in a Dimeric Epipolythiodioxopiperazine Natural Product Diminishes Its Apoptosis-Inducing Effect but Enhances Autophagy in Tumor Cells

Gliocladicillin C (3) is a cytotoxic epipolythiodioxopiperazine (ETP) isolated from the Ophiocordyceps-associated fungus Clonostachys rogersoniana. Although the disulfides/polysulfides in ETPs are believed to account for their cytotoxicity, and 11'-deoxyverticillin A was demonstrated to induce apoptosis and autophagy, how they mediate apoptosis and autophagy remained unknown. Here, we revealed that 3 activated caspase-dependent apoptosis and autophagy in human tumor cells, while the prepared disulfide-cleavage product failed to induce reactive oxygen species production and PARP cleavage, but further enhanced the autophagic flux compared to 3. Gliocladicillin C and its derivative also increased the phosphorylation of AMP-activated protein kinase and stimulated autophagy by affecting the glycolytic pathway. These results demonstrated that the disulfides played an essential role in inducing apoptosis, but not autophagy.

Non-coding RNAs: Key regulators of aerobic glycolysis in breast cancer

Although extensive research progress has been made in breast cancer in recent years, yet the morbidity and mortality rates of breast cancer are rising, making it the major disease that endangers women's health. Energy metabolism reprogramming is featured by a state termed "aerobic glycolysis" or the Warburg effect that glycolysis is preferred even under aerobic conditions in neoplastic diseases. Widely acknowledged as an emerging hallmark in cancers, this metabolic switch shows a sophisticated role in the pathogenesis of breast cancer. The regulating effect of non-coding RNAs (ncRNAs) composed of microRNAs, long non-coding RNAs and circular RNAs is closely related to the glycolysis in breast cancer. Therefore, understand the mechanisms of ncRNAs of aerobic glycolysis in breast cancer may provide new strategy for the disease.

PP2Cδ inhibits p300-mediated p53 acetylation via ATM/BRCA1 pathway to impede DNA damage response in breast cancer

Although nuclear type 2C protein phosphatase (PP2Cδ) has been demonstrated to be pro-oncogenic with an important role in tumorigenesis, the underlying mechanisms that link aberrant PP2Cδ levels with cancer development remain elusive. Here, we found that aberrant PP2Cδ activity decreases p53 acetylation and its transcriptional activity and suppresses doxorubicin-induced cell apoptosis. Mechanistically, we show that BRCA1 facilitates p300-mediated p53 acetylation by complexing with these two proteins and that S1423/1524 phosphorylation is indispensable for this regulatory process. PP2Cδ, via dephosphorylation of ATM, suppresses DNA damage-induced BRCA1 phosphorylation, leading to inhibition of p300-mediated p53 acetylation. Furthermore, PP2Cδ levels correlate with histological grade and are inversely associated with BRCA1 phosphorylation and p53 acetylation in breast cancer specimens. C23, our newly developed PP2Cδ inhibitor, promotes the anticancer effect of doxorubicin in MCF-7 xenograft-bearing nude mice. Together, our data indicate that PP2Cδ impairs p53 acetylation and DNA damage response by compromising BRCA1 function.

Cardamonin inhibits breast cancer growth by repressing HIF-1α-dependent metabolic reprogramming

Background

Cardamonin, a chalcone isolated from Alpiniae katsumadai, has anti-inflammatory and anti-tumor activities. However, the molecular mechanism by which cardamonin inhibits breast cancer progression largely remains to be determined.

Methods

CCK-8 and Hoechst 33258 staining were used to detect cell growth and apoptosis, respectively. HIF-1α driven transcription was measured by luciferase reporter assay. Glucose uptake and lactate content were detected with 2-NBDG and L-Lactate Assay Kit. Cell metabolism assays were performed on Agilent’s Seahorse Bioscience XF96 Extracellular Flux Analyzer. Mitochondrial membrane potential was measured with JC-1 probe. DCFH-DA was used to measure ROS level. Protein expression was detected by western blotting assay. Immunohistochemistry was performed to measure the expression of HIF-1α, LDHA and CD31 in tumor tissues.

Results

Cardamonin inhibited growth of the triple negative breast cancer cell line MDA-MB-231 in vitro and in vivo by suppressing HIF-1α mediated cell metabolism. Cardamonin inhibited the expression of HIF-1α at mRNA and protein levels by repressing the mTOR/p70S6K pathway, and subsequently enhanced mitochondrial oxidative phosphorylation and induced reactive oxygen species (ROS) accumulation. We also found that cardamonin inhibited the Nrf2-dependent ROS scavenging system which further increased intracellular ROS levels. Eventually, accumulation of the intracellular ROS induced apoptosis in breast cancer cells. In addition, cardamonin treatment reduced glucose uptake as well as lactic acid production and efflux, suggesting its function in repressing the glycolysis process.

Conclusions

These results reveal novel function of cardamonin in modulating cancer cell metabolism and suppressing breast cancer progression, and suggest its potential for breast cancer treatment.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1351-4) contains supplementary material, which is available to authorized users.

Metabolic Regulation of Glycolysis and AMP Activated Protein Kinase Pathways during Black Raspberry-Mediated Oral Cancer Chemoprevention

Oral cancer is a public health problem with an incidence of almost 50,000 and a mortality of 10,000 each year in the USA alone. Black raspberries (BRBs) have been shown to inhibit oral carcinogenesis in several preclinical models, but our understanding of how BRB phytochemicals affect the metabolic pathways during oral carcinogenesis remains incomplete. We used a well-established rat oral cancer model to determine potential metabolic pathways impacted by BRBs during oral carcinogenesis. F344 rats were exposed to the oral carcinogen 4-nitroquinoline-1-oxide in drinking water for 14 weeks, then regular drinking water for six weeks. Carcinogen exposed rats were fed a 5% or 10% BRB supplemented diet or control diet for six weeks after carcinogen exposure. RNA-Seq transcriptome analysis on rat tongue, and mass spectrometry and NMR metabolomics analysis on rat urine were performed. We tentatively identified 57 differentially or uniquely expressed metabolites and over 662 modulated genes in rats being fed with BRB. Glycolysis and AMPK pathways were modulated during BRB-mediated oral cancer chemoprevention. Glycolytic enzymes Aldoa, Hk2, Tpi1, Pgam2, Pfkl, and Pkm2 as well as the PKA-AMPK pathway genes Prkaa2, Pde4a, Pde10a, Ywhag, and Crebbp were downregulated by BRBs during oral cancer chemoprevention. Furthermore, the glycolysis metabolite glucose-6-phosphate decreased in BRB-administered rats. Our data reveal the novel metabolic pathways modulated by BRB phytochemicals that can be targeted during the chemoprevention of oral cancer.

Targeting of PP2Cδ By a Small Molecule C23 Inhibits High Glucose-Induced Breast Cancer Progression In Vivo

Aims: Epidemiologic evidence indicates that diabetes may increase risk of breast cancer (BC) and mortality in patients with cancer. The pathophysiological relationships between diabetes and cancer are not fully understood, and personalized treatments for diabetes-associated BC are urgently needed. Results: We observed that high glucose (HG), via activation of nuclear phosphatase PP2Cδ, suppresses p53 function, and consequently promotes BC cell proliferation, migration, and invasion. PP2Cδ expression is higher in tumor tissues from BC patients with hyperglycemia than those with normoglycemia. The mechanisms underlying HG stimulation of PP2Cδ involve classical/novel protein kinase-C (PKC) activation and GSK3β phosphorylation. Reactive oxygen species (ROS)/NF-κB pathway also mediates HG induction of PP2Cδ. Furthermore, we identified a 1,5-diheteroarylpenta-1,4-dien-3-one (Compound 23, or C23) as a novel potent PP2Cδ inhibitor with a striking cytotoxicity on MCF-7 cells through cell-based screening assay for growth inhibition and activity of a group of curcumin mimics. Beside directly inhibiting PP2Cδ activity, C23 blocks HG induction of PP2Cδ expression via heat shock protein 27 (HSP27) induction and subsequent ablation of ROS/NF-κB activation. C23 can thus significantly block HG-triggered inhibition of p53 activity, leading to the inhibition of cancer cell proliferation, migration, and invasion. In addition, hyperglycemia promotes BC development in diabetic nude mice, and C23 inhibits the xenografted BC tumor growth. Conclusions and Innovation: Our findings elucidate mechanisms that may have contributed to diabetes-associated BC progression, and provide the first evidence to support the possible alternative therapeutic approach to BC patients with diabetes. Antioxid. Redox Signal. 30, 1983-1998.

AMP-activated protein kinase: a potential therapeutic target for triple-negative breast cancer

Triple-negative breast cancer (TNBC) is an aggressive subset of breast carcinomas that lack expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor-2 (HER2). Unlike other breast cancer subtypes, targeted therapy is presently unavailable for patients with TNBC. In spite of initial responses to chemotherapy, drug resistance tends to develop rapidly and the prognosis of metastatic TNBC is poor. Hence, there is an urgent need for novel-targeted treatment methods or development of safe and effective alternatives with recognized mechanism(s) of action. AMP-activated protein kinase (AMPK), an energy sensor, can regulate protein and lipid metabolism responding to alterations in energy supply. In the past 10 years, interest in AMPK has increased widely since it appeared as an attractive targeting molecule for cancer therapy. There has been a deep understanding of the possible role of abnormal AMPK signaling pathways in the regulation of growth and survival and the development of drug resistance in TNBC. The increasing popularity of using AMPK regulators for TNBC-targeted therapy is supported by a considerable development in ascertaining the molecular pathways implicated. This review highlights the available evidence for AMPK-targeted anti-TNBC activity of various agents or treatment strategies, with special attention placed on recent preclinical and clinical advances in the manipulation of AMPK in TNBC. The elaborative analysis of these AMPK-related signaling pathways will have a noteworthy impact on the development of AMPK regulators, resulting in efficacious treatments for this lethal disease.

Crosstalk between Estrogen Signaling and Breast Cancer Metabolism

Estrogens and estrogen receptors (ERs) regulate metabolism in both normal physiology and in disease. The metabolic characteristics of intrinsic breast cancer subtypes change based on their ER expression. Crosstalk between estrogen signaling elements and several key metabolic regulators alters metabolism in breast cancer cells, and enables tumors to rewire their metabolism to adapt to poor perfusion, transient nutrient deprivation, and increased acidity. This leads to the selection of drug-resistant and metastatic clones. In this review we discuss studies revealing the role of estrogen signaling elements in drug resistance development and metabolic adaptation during breast cancer progression.

The utility of HepaRG cells for bioenergetic investigation and detection of drug-induced mitochondrial toxicity

The importance of mitochondrial toxicity in drug-induced liver injury is well established. The bioenergetic phenotype of the HepaRG cell line was defined in order to assess their suitability as a model of mitochondrial hepatotoxicity. Bioenergetic phenotyping categorised the HepaRG cells as less metabolically active when measured beside the more energetic HepG2 cells. However, inhibition of mitochondrial ATP synthase induced an increase in glycolytic activity of both HepaRG and HepG2 cells suggesting an active Crabtree Effect in both cell lines. The suitability of HepaRG cells for the acute metabolic modification assay as a screen for mitotoxicity was confirmed using a panel of compounds, including both positive and negative mitotoxic compounds. Seahorse respirometry studies demonstrated that a statistically significant decrease in spare respiratory capacity is the first indication of mitochondrial dysfunction. Furthermore, based upon comparing changes in respiratory parameters to those of the positive controls, rotenone and carbonyl cyanide m-chlorophenyl hydrazone, compounds were categorised into two mechanistic groups; inhibitors or uncouplers of the electron transport chain. Overall, the findings from this study have demonstrated that HepaRG cells, despite having different resting bioenergetic phenotype to HepG2 cells are a suitable model to detect drug-induced mitochondrial toxicity with similar detection rates to HepG2 cells.

The carnitine system and cancer metabolic plasticity

Metabolic flexibility describes the ability of cells to respond or adapt its metabolism to support and enable rapid proliferation, continuous growth, and survival in hostile conditions. This dynamic character of the cellular metabolic network appears enhanced in cancer cells, in order to increase the adaptive phenotype and to maintain both viability and uncontrolled proliferation. Cancer cells can reprogram their metabolism to satisfy the energy as well as the biosynthetic intermediate request and to preserve their integrity from the harsh and hypoxic environment. Although several studies now recognize these reprogrammed activities as hallmarks of cancer, it remains unclear which are the pathways involved in regulating metabolic plasticity. Recent findings have suggested that carnitine system (CS) could be considered as a gridlock to finely trigger the metabolic flexibility of cancer cells. Indeed, the components of this system are involved in the bi-directional transport of acyl moieties from cytosol to mitochondria and vice versa, thus playing a fundamental role in tuning the switch between the glucose and fatty acid metabolism. Therefore, the CS regulation, at both enzymatic and epigenetic levels, plays a pivotal role in tumors, suggesting new druggable pathways for prevention and treatment of human cancer.

Eugenol inhibits oxidative phosphorylation and fatty acid oxidation via downregulation of c-Myc/PGC-1β/ERRα signaling pathway in MCF10A-ras cells

Alteration in cellular energy metabolism plays a critical role in the development and progression of cancer. Targeting metabolic pathways for cancer treatment has been investigated as potential preventive or therapeutic methods. Eugenol (Eu), a major volatile constituent of clove essential oil mainly obtained from Syzygium, has been reported as a potential chemopreventive drug. However, the mechanism by which Eu regulates cellular energy metabolism is still not well defined. This study was designed to determine the effect of Eu on cellular energy metabolism during early cancer progression employing untransformed and H-ras oncogene transfected MCF10A human breast epithelial cells. Eu showed dose-dependent selective cytotoxicity toward MCF10A-ras cells but exhibited no apparent cytotoxicity in MCF10A cells. Treatment with Eu also significantly reduced intracellular ATP levels in MCF10A-ras cells but not in MCF10A cells. This effect was mediated mainly through inhibiting oxidative phosphorylation (OXPHOS) complexs and the expression of fatty acid oxidation (FAO) proteins including PPARα, MCAD and CPT1C by downregulating c-Myc/PGC-1β/ERRα pathway and decreasing oxidative stress in MCF10A-ras cells. These results indicate a novel mechanism involving the regulation of cellular energy metabolism by which Eu may prevent breast cancer progression.

Reactive oxygen species (ROS) are a key determinant of cancer's metabolic phenotype

Cancer cells exhibit a wide range of metabolic phenotypes, ranging from strict aerobic glycolysis to increased mitochondrial respiration. The cause and utility of this metabolic variation is poorly understood. Given that cancer cells experience heavy selection within their microenvironment, survival requires metabolic adaptation to both extracellular and intracellular conditions. Herein, we suggest that reactive oxygen species (ROS) are a key determinant of cancer's metabolic phenotype. Intracellular ROS levels can be modified by an assortment of critical parameters including oxygenation, glucose availability and growth factors. ROS act as integrators of environmental information as well as downstream effectors of signaling pathways. Maintaining ROS within a narrow range allows malignant cells to enhance growth and invasion while limiting their apoptotic susceptibility. Cancer cells actively modify their metabolism to optimize intracellular ROS levels and thereby improve survival. Furthermore, we highlight distinct metabolic phenotypes in response to oxidative stress and their tumorigenic drivers.

Cell-Intrinsic Glycogen Metabolism Supports Early Glycolytic Reprogramming Required for Dendritic Cell Immune Responses

Dendritic cell (DC) activation by Toll-like receptor (TLR) agonists causes rapid glycolytic reprogramming that is required to meet the metabolic demands of their immune activation. Recent efforts in the field have identified an important role for extracellular glucose sourcing to support DC activation. However, the contributions of intracellular glucose stores to these processes have not been well characterized. We demonstrate that DCs possess intracellular glycogen stores and that cell-intrinsic glycogen metabolism supports the early effector functions of TLR-activated DCs. Inhibition of glycogenolysis significantly attenuates TLR-mediated DC maturation and impairs their ability to initiate lymphocyte activation. We further report that DCs exhibit functional compartmentalization of glucose- and glycogen-derived carbons, where these substrates preferentially contribute to distinct metabolic pathways. This work provides novel insights into nutrient homeostasis in DCs, demonstrating that differential utilization of glycogen and glucose metabolism regulates their optimal immune function.

Insulin-like growth factor 1 signaling is essential for mitochondrial biogenesis and mitophagy in cancer cells

Mitochondrial activity and metabolic reprogramming influence the phenotype of cancer cells and resistance to targeted therapy. We previously established that an insulin-like growth factor 1 (IGF-1)-inducible mitochondrial UTP carrier (PNC1/SLC25A33) promotes cell growth. This prompted us to investigate whether IGF signaling is essential for mitochondrial maintenance in cancer cells and whether this contributes to therapy resistance. Here we show that IGF-1 stimulates mitochondrial biogenesis in a range of cell lines. In MCF-7 and ZR75.1 breast cancer cells, IGF-1 induces peroxisome proliferator-activated receptor γ coactivator 1β (PGC-1β) and PGC-1α-related coactivator (PRC). Suppression of PGC-1β and PRC with siRNA reverses the effects of IGF-1 and disrupts mitochondrial morphology and membrane potential. IGF-1 also induced expression of the redox regulator nuclear factor-erythroid-derived 2-like 2 (NFE2L2 alias NRF-2). Of note, MCF-7 cells with acquired resistance to an IGF-1 receptor (IGF-1R) tyrosine kinase inhibitor exhibited reduced expression of PGC-1β, PRC, and mitochondrial biogenesis. Interestingly, these cells exhibited mitochondrial dysfunction, indicated by reactive oxygen species expression, reduced expression of the mitophagy mediators BNIP3 and BNIP3L, and impaired mitophagy. In agreement with this, IGF-1 robustly induced BNIP3 accumulation in mitochondria. Other active receptor tyrosine kinases could not compensate for reduced IGF-1R activity in mitochondrial protection, and MCF-7 cells with suppressed IGF-1R activity became highly dependent on glycolysis for survival. We conclude that IGF-1 signaling is essential for sustaining cancer cell viability by stimulating both mitochondrial biogenesis and turnover through BNIP3 induction. This core mitochondrial protective signal is likely to strongly influence responses to therapy and the phenotypic evolution of cancer.

PPARα regulates tumor cell proliferation and senescence via a novel target gene carnitine palmitoyltransferase 1C

Carnitine palmitoyltransferase 1C (CPT1C), an enzyme located in the outer mitochondria membrane, has a crucial role in fatty acid transport and oxidation. It is also involved in cell proliferation and is a potential driver for cancer cell senescence. However, its upstream regulatory mechanism is unknown. Peroxisome proliferator activated receptor α (PPARα) is a ligand-activated transcription factor that regulates lipid metabolism and tumor progression. The current study aimed to elucidate whether and how PPARα regulates CPT1C and then affects cancer cell proliferation and senescence. Here, for the first time we report that PPARα directly activated CPT1C transcription and CPT1C was a novel target gene of PPARα, as revealed by dual-luciferase reporter and chromatin immunoprecipitation (ChIP) assays. Moreover, regulation of CPT1C by PPARα was p53-independent. We further confirmed that depletion of PPARα resulted in low CPT1C expression and then inhibited proliferation and induced senescence of MDA-MB-231 and PANC-1 tumor cell lines in a CPT1C-dependent manner, while forced PPARα overexpression promoted cell proliferation and reversed cellular senescence. Taken together, these results indicate that CPT1C is a novel PPARα target gene that regulates cancer cell proliferation and senescence. The PPARα-CPT1C axis may be a new target for the intervention of cancer cellular proliferation and senescence.

Aberrant Phosphorylation of SMAD4 Thr277-Mediated USP9x-SMAD4 Interaction by Free Fatty Acids Promotes Breast Cancer Metastasis

Obesity increases the risk of distant metastatic recurrence and reduces breast cancer survival. However, the mechanisms behind this pathology and identification of relevant therapeutic targets are poorly defined. Plasma free fatty acids (FFA) levels are elevated in obese individuals. Here we report that TGFβ transiently activates ERK and subsequently phosphorylates SMAD4 at Thr277, which facilitates a SMAD4-USP9x interaction, SMAD4 nuclear retention, and stimulates TGFβ/SMAD3-mediated transcription of Twist and Snail. USP9x inhibited the E3 ubiquitin-protein ligase TIF1γ from binding and monoubiquitinating SMAD4, hence maintaining the SMAD4 nuclear retention. FFA further facilitated TGFβ-induced ERK activation, SMAD4 phosphorylation, and nuclear retention, promoting TGFβ-dependent cancer progression. Inhibition of ERK and USP9x suppressed obesity-induced metastasis. In addition, clinical data indicated that phospho-ERK and -SMAD4 levels correlate with activated TGFβ signaling and metastasis in overweight/obese patient breast cancer specimens. Altogether, we demonstrate the vital interaction of USP9x and SMAD4 for governing TGFβ signaling and dyslipidemia-induced aberrant TGFβ activation during breast cancer metastasis. Cancer Res; 77(6); 1383-94. ©2017 AACR.

Activation of AMPKα mediates additive effects of solamargine and metformin on suppressing MUC1 expression in castration-resistant prostate cancer cells

Prostate cancer is the second most common cause of cancer-related deaths worldwide. The mucin 1 (MUC1) oncoprotein is highly expressed in human prostate cancers with aggressive features. However, the role for MUC1 in occurrence and progression of castration-resistant prostate cancer (CRPC) remained elusive. In this study, we showed that solamargine, a major steroidal alkaloid glycoside, inhibited the growth of CRPC cells, which was enhanced in the presence of metformin. Furthermore, we found that solamargine increased phosphorylation of AMPKα, whereas reducing the protein expression and promoter activity of MUC1. A greater effect was observed in the presence of metformin. In addition, solamargine reduced NF-κB subunit p65 protein expression. Exogenously expressed p65 resisted solamargine-reduced MUC1 protein and promoter activity. Interestingly, exogenously expressed MUC1 attenuated solamargine-stimulated phosphorylation of AMPKα and, more importantly reversed solamargine-inhibited cell growth. Finally, solamargine increased phosphorylation of AMPKα, while inhibiting MUC1, p65 and tumor growth were observed in vivo. Overall, our results show that solamargine inhibits the growth of CRPC cells through AMPKα-mediated inhibition of p65, followed by reduction of MUC1 expression in vitro and in vivo. More importantly, metformin facilitates the antitumor effect of solamargine on CRPC cells.

Cytotoxic activity of physodic acid and acetone extract from Hypogymnia physodes against breast cancer cell lines

CONTEXT

Lichens produce specific secondary metabolites with different biological activity.

OBJECTIVE

This study investigated the cytotoxic effects of physodic acid, in addition to the total phenolic content and cytotoxic and antioxidant activity of acetone extract from Hypogymnia physodes (L.) Nyl. (Parmeliaceae).

MATERIALS AND METHODS

Cytotoxicity of physodic acid (0.1-100 μM) was assessed in MDA-MB-231, MCF-7 and T-47D breast cancer cell lines and a nontumorigenic MCF-10A cell line using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, neutral red uptake and crystal violet assays during 72 h of incubation. An MTT assay was also used to assess the cytotoxic effects of the acetone extract (0.1-100 μg/mL) in the MDA-MB-231, MCF-7, T-47D breast cancer cell lines after 72 h. The total phenolic content of the acetone extract, expressed as the gallic acid equivalent, was investigated using Folin-Ciocalteu reagent. The antioxidant activity of the extract was assessed by 2,2-diphenyl-1-picrylhydrazyl and ferric-reducing antioxidant power assays.

RESULTS

The cytotoxic activity of physodic acid appeared to be strong in the tumorigenic cell lines (IC₅₀ 46.0-93.9 μM). The compound was inactive against the nontumorigenic MCF-10A cell line (IC₅₀>100 μM). The acetone extract showed cytotoxicity in the breast cancer cell lines (IC₅₀ 46.2-110.4 μg/mL). The acetone extract was characterized by a high content of polyphenols, and it had significant antioxidant activity.

DISCUSSION AND CONCLUSION

Physodic acid and acetone extract from H. physodes displayed cytotoxic effects in the breast cancer cell lines. Furthermore, acetone extract from H. physodes possessed significant antioxidant properties.

Chinese herbal medicine Xiaoji decoction inhibited growth of lung cancer cells through AMPKα-mediated inhibition of Sp1 and DNA methyltransferase 1

ETHNOPHARMACOLOGICAL RELEVANCE

Xiaoji decoction (XJD), which was considered as a Chinese herbal prescription, has been used for cancer treatment, especially lung cancer, for decades to improve quality of life and prolong the patient survival. However, the molecular mechanisms underlying the therapeutic potential have not been well elucidated.

MATERIALS AND METHODS

The cell viability was examined by MTT assays. The phosphorylation and expression of AMP-activated protein kinase alpha (AMPKα), DNA methyltransferase 1 (DNMT1) and transcription factor Sp1 proteins were assessed by Western Blot. Exogenous expression of Sp1 and DNMT1 were performed by transient transfection methods. The effects of XJD on the growth of xenograft tumors were evaluated by in vivo bioluminescence imaging.

RESULTS

We showed that XJD inhibited growth of human non small cell lung cancer (NSCLC) cells in vitro. We also found that XJD increased phosphorylation of AMPKα and inhibited protein expression of DNTM1, the latter was not observed in the presence of the inhibitor of AMPK (compound C). Overexpression of DNTM1 reversed the effect of XJD on cell growth. In addition, XJD decreased Sp1 protein expression, which was eliminated by compound C. Conversely, exogenous expressed Sp1 abrogated XJD-inhibited DNTM1 protein expression. Interestingly, exogenous expression of DNMT1 feedback antagonized the XJD-induced phosphorylation of AMPKα. In in vivo studies, we found that XJD inhibited tumor growth in xenograft nude mice model, which was accompanied by induction of phosphorylation of AMPKα and suppression of DNMT1 protein from xenograft tumors.

CONCLUSION

Our results show that XJD inhibits NSCLC cell growth via AMPKα-mediated inhibition of transcription of Sp1, followed by the reduction of DNMT1 expression both in vitro and in vivo. The negative feedback regulation loop of AMPKα further demonstrates the critical role of DNMT1 in mediating the overall effects of XJD in this process. This study unveils novel molecular mechanism by which XJD controls NSCLC cell growth.

Co-targeting hexokinase 2-mediated Warburg effect and ULK1-dependent autophagy suppresses tumor growth of PTEN- and TP53-deficiency-driven castration-resistant prostate cancer

Currently, no therapeutic options exist for castration-resistant prostate cancer (CRPC) patients who have developed resistance to the second generation anti-androgen receptor (AR) axis therapy. Here we report that co-deletion of Pten and p53 in murine prostate epithelium, often observed in human CRPC, leads to AR-independent CRPC and thus confers de novo resistance to second generation androgen deprivation therapy (ADT) in multiple independent yet complementary preclinical mouse models. In contrast, mechanism-driven co-targeting hexokinase 2 (HK2)-mediated Warburg effect with 2-deoxyglucose (2-DG) and ULK1-dependent autophagy with chloroquine (CQ) selectively kills cancer cells through intrinsic apoptosis to cause tumor regression in xenograft, leads to a near-complete tumor suppression and remarkably extends survival in Pten-/p53-deficiency-driven CRPC mouse model. Mechanistically, 2-DG causes AMPK phosphorylation, which in turn inhibits mTORC1-S6K1 translation signaling to preferentially block anti-apoptotic protein MCL-l synthesis to prime mitochondria-dependent apoptosis while simultaneously activates ULK1-driven autophagy for cell survival to counteract the apoptotic action of anti-Warburg effect. Accordingly, inhibition of autophagy with CQ sensitizes cancer cells to apoptosis upon 2-DG challenge. Given that 2-DG is recommended for phase II clinical trials for prostate cancer and CQ has been clinically used as an anti-malaria drug for many decades, the preclinical results from our proof-of-principle studies in vivo are imminently translatable to clinical trials to evaluate the therapeutic efficacy by the combination modality for a subset of currently incurable CRPC harboring PTEN and TP53 mutations.