Activation of androgen receptor, lipogenesis, and oxidative stress converged by SREBP-1 is responsible for regulating growth and progression of prostate cancer cells

SREBF1 Activity Is Regulated by an AR/mTOR Nuclear Axis in Prostate Cancer

Reprogramming of cellular metabolism is an important feature of prostate cancer, including altered lipid metabolism. Recently, it was observed that the nuclear fraction of mTOR is essential for the androgen-mediated metabolic reprogramming of prostate cancer cells. Herein, it is demonstrated that the androgen receptor (AR) and mTOR bind to regulatory regions of sterol regulatory element-binding transcription factor 1 (SREBF1) to control its expression, whereas dual activation of these signaling pathways also promotes SREBF1 cleavage and its translocation to the nucleus. Consequently, SREBF1 recruitment to regulatory regions of its target genes is induced upon treatment with the synthetic androgen R1881, an effect abrogated upon inhibition of the mTOR signaling pathway. In turn, pharmacologic and genetic inhibition of SREBF1 activity impairs the androgen-mediated induction of the key lipogenic genes fatty acid synthase (FASN) and stearoyl-CoA desaturase (SCD1). Consistent with these observations, the expression of the SREBF1, FASN, and SCD1 genes is significantly correlated in human prostate cancer tumor clinical specimens. Functionally, blockade of SREBF1 activity reduces the androgen-driven lipid accumulation. Interestingly, decreased triglyceride accumulation observed upon SREBF1 inhibition is paralleled by an increase in mitochondrial respiration, indicating a potential rewiring of citrate metabolism in prostate cancer cells. Altogether, these data define an AR/mTOR nuclear axis, in the context of prostate cancer, as a novel pathway regulating SREBF1 activity and citrate metabolism.Implications: The finding that an AR/mTOR complex promotes SREBF1 expression and activity enhances our understanding of the metabolic adaptation necessary for prostate cancer cell growth and suggests novel therapeutic approaches to target metabolic vulnerabilities in tumors. Mol Cancer Res; 16(9); 1396-405. ©2018 AACR.

Lipid metabolism reprogramming and its potential targets in cancer

Reprogramming of lipid metabolism is a newly recognized hallmark of malignancy. Increased lipid uptake, storage and lipogenesis occur in a variety of cancers and contribute to rapid tumor growth. Lipids constitute the basic structure of membranes and also function as signaling molecules and energy sources. Sterol regulatory element-binding proteins (SREBPs), a family of membrane-bound transcription factors in the endoplasmic reticulum, play a central role in the regulation of lipid metabolism. Recent studies have revealed that SREBPs are highly up-regulated in various cancers and promote tumor growth. SREBP cleavage-activating protein is a key transporter in the trafficking and activation of SREBPs as well as a critical glucose sensor, thus linking glucose metabolism and de novo lipid synthesis. Targeting altered lipid metabolic pathways has become a promising anti-cancer strategy. This review summarizes recent progress in our understanding of lipid metabolism regulation in malignancy, and highlights potential molecular targets and their inhibitors for cancer treatment.

The histone demethylase KDM3A regulates the transcriptional program of the androgen receptor in prostate cancer cells

The lysine demethylase 3A (KDM3A, JMJD1A or JHDM2A) controls transcriptional networks in a variety of biological processes such as spermatogenesis, metabolism, stem cell activity, and tumor progression. We matched transcriptomic and ChIP-Seq profiles to decipher a genome-wide regulatory network of epigenetic control by KDM3A in prostate cancer cells. ChIP-Seq experiments monitoring histone 3 lysine 9 (H3K9) methylation marks show global histone demethylation effects of KDM3A. Combined assessment of histone demethylation events and gene expression changes presented major transcriptional activation suggesting that distinct oncogenic regulators may synergize with the epigenetic patterns by KDM3A. Pathway enrichment analysis of cells with KDM3A knockdown prioritized androgen signaling indicating that KDM3A plays a key role in regulating androgen receptor activity. Matched ChIP-Seq and knockdown experiments of KDM3A in combination with ChIP-Seq of the androgen receptor resulted in a gain of H3K9 methylation marks around androgen receptor binding sites of selected transcriptional targets in androgen signaling including positive regulation of KRT19, NKX3-1, KLK3, NDRG1, MAF, CREB3L4, MYC, INPP4B, PTK2B, MAPK1, MAP2K1, IGF1, E2F1, HSP90AA1, HIF1A, and ACSL3. The cancer systems biology analysis of KDM3A-dependent genes identifies an epigenetic and transcriptional network in androgen response, hypoxia, glycolysis, and lipid metabolism. Genome-wide ChIP-Seq data highlights specific gene targets and the ability of epigenetic master regulators to control oncogenic pathways and cancer progression.

Downregulation of SREBP inhibits tumor growth and initiation by altering cellular metabolism in colon cancer

Sterol regulatory element-binding proteins (SREBPs) belong to a family of transcription factors that regulate the expression of genes required for the synthesis of fatty acids and cholesterol. Three SREBP isoforms, SREBP1a, SREBP1c, and SREBP2, have been identified in mammalian cells. SREBP1a and SREBP1c are derived from a single gene through the use of alternative transcription start sites. Here we investigated the role of SREBP-mediated lipogenesis in regulating tumor growth and initiation in colon cancer. Knockdown of either SREBP1 or SREBP2 decreased levels of fatty acids as a result of decreased expression of SREBP target genes required for lipid biosynthesis in colon cancer cells. Bioenergetic analysis revealed that silencing SREBP1 or SREBP2 expression reduced the mitochondrial respiration, glycolysis, as well as fatty acid oxidation indicating an alteration in cellular metabolism. Consequently, the rate of cell proliferation and the ability of cancer cells to form tumor spheroids in suspension culture were significantly decreased. Similar results were obtained in colon cancer cells in which the proteolytic activation of SREBP was blocked. Importantly, knockdown of either SREBP1 or SREBP2 inhibited xenograft tumor growth in vivo and decreased the expression of genes associated with cancer stem cells. Taken together, our findings establish the molecular basis of SREBP-dependent metabolic regulation and provide a rationale for targeting lipid biosynthesis as a promising approach in colon cancer treatment.

Increased expression of the gene encoding stearoyl-CoA desaturase 1 in human bladder cancer

Bladder cancer is a common disease and a significant cause of death worldwide. There is thus great interest in identifying a diagnostic and prognostic biomarker, as well as gaining an understanding of the molecular basis of bladder cancer. Stearoyl-CoA desaturase 1 gene (SCD1) is highly overexpressed in many human cancers. However, the expression of SCD1 has not yet been investigated in patients with bladder cancer. Here, we document that (a) the SCD1 is highly overexpressed in human bladder cancer; (b) high expression of SCD1 is more frequently observed in the late stage of disease and patients with lymph node metastasis; (c) bladder cancer patients with a higher SCD1 mRNA level have a poorer survival rate than those with normal SCD1 expression. Overall, this is the first report to indicate an association between SCD1 mRNA level and clinical indicators of human bladder cancer. Our study has provided evidence supporting the potential role of SCD1 as a biomarker for human bladder cancer prognosis.

Metabolism and Transcription in Cancer: Merging Two Classic Tales

Cellular plasticity, or the ability of a cancer cell to adapt to changes in the microenvironment, is a major determinant of cell survival and functionality that require the coordination of transcriptional programs with signaling and metabolic pathways. In this scenario, these pathways sense and integrate nutrient signals for the induction of coordinated gene expression programs in cancer. This minireview focuses on recent advances that shed light on the bidirectional relationship between metabolism and gene transcription, and their biological outcomes in cancer. Specifically, we will discuss how metabolic changes occurring in cancer cells impact on gene expression, both at the level of the epigenetic landscape and transcription factor regulation.

NADPH oxidase 5 (NOX5)-induced reactive oxygen signaling modulates normoxic HIF-1α and p27Kip1 expression in malignant melanoma and other human tumors

NADPH oxidase 5 (NOX5) generated reactive oxygen species (ROS) have been implicated in signaling cascades that regulate cancer cell proliferation. To evaluate and validate NOX5 expression in human tumors, we screened a broad range of tissue microarrays (TMAs), and report substantial overexpression of NOX5 in malignant melanoma and cancers of the prostate, breast, and ovary. In human UACC-257 melanoma cells that possesses high levels of functional endogenous NOX5, overexpression of NOX5 resulted in enhanced cell growth, increased numbers of BrdU positive cells, and increased γ-H2AX levels. Additionally, NOX5-overexpressing (stable and inducible) UACC-257 cells demonstrated increased normoxic HIF-1α expression and decreased p27Kip1 expression. Similarly, increased normoxic HIF-1α expression and decreased p27Kip1 expression were observed in stable NOX5-overexpressing clones of KARPAS 299 human lymphoma cells and in the human prostate cancer cell line, PC-3. Conversely, knockdown of endogenous NOX5 in UACC-257 cells resulted in decreased cell growth, decreased HIF-1α expression, and increased p27Kip1 expression. Likewise, in an additional human melanoma cell line, WM852, and in PC-3 cells, transient knockdown of endogenous NOX5 resulted in increased p27Kip1 and decreased HIF-1α expression. Knockdown of endogenous NOX5 in UACC-257 cells resulted in decreased Akt and GSK3β phosphorylation, signaling pathways known to modulate p27Kip1 levels. In summary, our findings suggest that NOX5 expression in human UACC-257 melanoma cells could contribute to cell proliferation due, in part, to the generation of high local concentrations of extracellular ROS that modulate multiple pathways that regulate HIF-1α and networks that signal through Akt/GSK3β/p27Kip1 .

SREBP-2 promotes stem cell-like properties and metastasis by transcriptional activation of c-Myc in prostate cancer

Sterol regulatory element-binding protein-2 (SREBP-2) transcription factor mainly controls cholesterol biosynthesis and homeostasis in normal cells. The role of SREBP-2 in lethal prostate cancer (PCa) progression remains to be elucidated. Here, we showed that expression of SREBP-2 was elevated in advanced pathologic grade and metastatic PCa and significantly associated with poor clinical outcomes. Biofunctional analyses demonstrated that SREBP-2 induced PCa cell proliferation, invasion and migration. Furthermore, overexpression of SREBP-2 increased the PCa stem cell population, prostasphere-forming ability and tumor-initiating capability, whereas genetic silencing of SREBP-2 inhibited PCa cell growth, stemness, and xenograft tumor growth and metastasis. Clinical and mechanistic data showed that SREBP-2 was positively correlated with c-Myc and induced c-Myc activation by directly interacting with an SREBP-2-binding element in the 5′-flanking c-Myc promoter region to drive stemness and metastasis. Collectively, these clinical and experimental results reveal a novel role of SREBP-2 in the induction of a stem cell-like phenotype and PCa metastasis, which sheds light on translational potential by targeting SREBP-2 as a promising therapeutic approach in PCa.

RNF20 Suppresses Tumorigenesis by Inhibiting the SREBP1c-PTTG1 Axis in Kidney Cancer

Elevated lipid metabolism promotes cancer cell proliferation. Clear cell renal cell carcinoma (ccRCC) is the most common subtype of kidney cancers, characterized by ectopic lipid accumulation. However, the relationship between aberrant lipid metabolism and tumorigenesis in ccRCC is not thoroughly understood. Here, we demonstrate that ring finger protein 20 (RNF20) acts as a tumor suppressor in ccRCC. RNF20 overexpression repressed lipogenesis and cell proliferation by inhibiting sterol regulatory element-binding protein 1c (SREBP1c), and SREBP1 suppression, either by knockdown or by the pharmacological inhibitor betulin, attenuated proliferation and cell cycle progression in ccRCC cells. Notably, SREBP1c regulates cell cycle progression by inducing the expression of pituitary tumor-transforming gene 1 (PTTG1), a novel target gene of SREBP1c. Furthermore, RNF20 overexpression reduced tumor growth and lipid storage in xenografts. In ccRCC patients, RNF20 downregulation and SREBP1 activation are markers of poor prognosis. Therefore, RNF20 suppresses tumorigenesis in ccRCC by inhibiting the SREBP1c-PTTG1 axis.

A Mini-Review of Reactive Oxygen Species in Urological Cancer: Correlation with NADPH Oxidases, Angiogenesis, and Apoptosis

Oxidative stress refers to elevated reactive oxygen species (ROS) levels, and NADPH oxidases (NOXs), which are one of the most important sources of ROS. Oxidative stress plays important roles in the etiologies, pathological mechanisms, and treatment strategies of vascular diseases. Additionally, oxidative stress affects mechanisms of carcinogenesis, tumor growth, and prognosis in malignancies. Nearly all solid tumors show stimulation of neo-vascularity, termed angiogenesis, which is closely associated with malignant aggressiveness. Thus, cancers can be seen as a type of vascular disease. Oxidative stress-induced functions are regulated by complex endogenous mechanisms and exogenous factors, such as medication and diet. Although understanding these regulatory mechanisms is important for improving the prognosis of urothelial cancer, it is not sufficient, because there are controversial and conflicting opinions. Therefore, we believe that this knowledge is essential to discuss observations and treatment strategies in urothelial cancer. In this review, we describe the relationships between members of the NOX family and tumorigenesis, tumor growth, and pathological mechanisms in urological cancers including prostate cancer, renal cell carcinoma, and urothelial cancer. In addition, we introduce natural compounds and chemical agents that are associated with ROS-induced angiogenesis or apoptosis.

Telomerase reverse transcriptase (TERT) - enhancer of zeste homolog 2 (EZH2) network regulates lipid metabolism and DNA damage responses in glioblastoma

Elevated expression of enhancer of zeste homolog 2 (EZH2), a histone H3K27 methyltransferase, was observed in gliomas harboring telomerase reverse transcriptase (TERT) promoter mutations. Given the known involvement of TERT and EZH2 in glioma progression, the correlation between the two and subsequently its involvement in metabolic programming was investigated. Inhibition of human telomerase reverse transcriptase either pharmacologically or through genetic manipulation not only decreased EZH2 expression, but also (i) abrogated FASN levels, (ii) decreased de novo fatty acid accumulation, and (iii) increased ataxia-telangiectasia-mutated (ATM) phosphorylation levels. Conversely, diminished TERT and FASN levels upon siRNA-mediated EZH2 knockdown indicated a positive correlation between TERT and EZH2. Interestingly, ATM kinase inhibitor rescued TERT inhibition-mediated decrease in FASN and EZH2 levels. Importantly, TERT promoter mutant tumors exhibited greater microsatellite instability, heightened FASN levels and lipid accumulation. Coherent with in vitro findings, pharmacological inhibition of TERT by costunolide decreased lipid accumulation and elevated ATM expression in heterotypic xenograft glioma mouse model. By bringing TERT-EZH2 network at the forefront as driver of dysregulated metabolism, our findings highlight the non-canonical but distinct role of TERT in metabolic reprogramming and DNA damage responses in glioblastoma.

ACSL3 promotes intratumoral steroidogenesis in prostate cancer cells

Long‐chain acyl‐coenzyme A (CoA) synthetase 3 (ACSL3) is an androgen‐responsive gene involved in the generation of fatty acyl‐CoA esters. ACSL3 is expressed in both androgen‐sensitive and castration‐resistant prostate cancer (CRPC). However, its role in prostate cancer remains elusive. We overexpressed ACSL3 in androgen‐dependent LNCaP cells and examined the downstream effectors of ACSL3. Furthermore, we examined the role of ACSL3 in the androgen metabolism of prostate cancer. ACSL3 overexpression led to upregulation of several genes such as aldo‐keto reductase 1C3 (AKR1C3) involved in steroidogenesis, which utilizes adrenal androgen dehydroepiandrosterone sulfate (DHEAS) as substrate, and downregulated androgen‐inactivating enzyme UDP‐glucuronosyltransferase 2 (UGT2B). Exposure to DHEAS significantly increased testosterone levels and cell proliferative response in ACSL3‐overexpressing cells when compared to that in control cells. A public database showed that ACSL3 level was higher in CRPC than in hormone‐sensitive prostate cancer. CRPC cells showed an increased expression of ACSL3 and an expression pattern of AKR1C3 and UGT2B similar to ACSL3‐overexpressing cells. DHEAS stimulation significantly promoted the proliferation of CRPC cells when compared to that of LNCaP cells. These findings suggest that ACSL3 contributes to the growth of CRPC through intratumoral steroidogenesis (i.e. promoting androgen synthesis from DHEAS and preventing the catabolism of active androgens).

An Overview of Lipid Droplets in Cancer and Cancer Stem Cells

For decades, lipid droplets have been considered as the main cellular organelles involved in the fat storage, because of their lipid composition. However, in recent years, some new and totally unexpected roles have been discovered for them: (i) they are active sites for synthesis and storage of inflammatory mediators, and (ii) they are key players in cancer cells and tissues, especially in cancer stem cells. In this review, we summarize the main concepts related to the lipid droplet structure and function and their involvement in inflammatory and cancer processes.

RGS12 Is a Novel Tumor-Suppressor Gene in African American Prostate Cancer That Represses AKT and MNX1 Expression

African American (AA) men exhibit a relatively high incidence and mortality due to prostate cancer even after adjustment for socioeconomic factors, but the biological basis for this disparity is unclear. Here, we identify a novel region on chromosome 4p16.3 that is lost selectively in AA prostate cancer. The negative regulator of G-protein signaling RGS12 was defined as the target of 4p16.3 deletions, although it has not been implicated previously as a tumor-suppressor gene. RGS12 transcript levels were relatively reduced in AA prostate cancer, and prostate cancer cell lines showed decreased RGS12 expression relative to benign prostate epithelial cells. Notably, RGS12 exhibited potent tumor-suppressor activity in prostate cancer and prostate epithelial cell lines in vitro and in vivo We found that RGS12 expression correlated negatively with the oncogene MNX1 and regulated its expression in vitro and in vivo Further, MNX1 was regulated by AKT activity, and RGS12 expression decreased total and activated AKT levels. Our findings identify RGS12 as a candidate tumor-suppressor gene in AA prostate cancer, which acts by decreasing expression of AKT and MNX1, establishing a novel oncogenic axis in this disparate disease setting. Cancer Res; 77(16); 4247-57. ©2017 AACR.

ROS signalling in the biology of cancer

Increased reactive oxygen species (ROS) production has been detected in various cancers and has been shown to have several roles, for example, they can activate pro-tumourigenic signalling, enhance cell survival and proliferation, and drive DNA damage and genetic instability. Counterintuitively ROS can also promote anti-tumourigenic signalling, initiating oxidative stress-induced tumour cell death. Tumour cells express elevated levels of antioxidant proteins to detoxify elevated ROS levels, establish a redox balance, while maintaining pro-tumourigenic signalling and resistance to apoptosis. Tumour cells have an altered redox balance to that of their normal counterparts and this identifies ROS manipulation as a potential target for cancer therapies. This review discusses the generation and sources of ROS within tumour cells, the regulation of ROS by antioxidant defence systems, as well as the effect of elevated ROS production on their signalling targets in cancer. It also provides an insight into how pro- and anti-tumourigenic ROS signalling pathways could be manipulated in the treatment of cancer.

Inhibition of the sterol regulatory element-binding protein pathway suppresses hepatocellular carcinoma by repressing inflammation in mice

Obesity is a critical risk factor for hepatocellular carcinoma (HCC). However, it remains unknown whether inhibition of de novo lipid biosynthesis can suppress HCC. In this study, we blocked the sterol regulatory element-binding protein (SREBP) pathway, one of the key determinants of lipid homeostasis, by ablating 78-kDa cell-surface glycoprotein or SREBP cleavage-activating protein in hepatocytes, as well as by administering a chemical compound called betulin. We found that either genetically or pharmacologically inhibiting the SREBP pathway dramatically reduced diethylnitrosamine-induced HCC progression by down-regulating tumor-promoting cytokines, including interleukin (IL)-6, tumor necrosis factor alpha, and IL-1β.

CONCLUSION

Inhibition of de novo lipid biosynthesis by suppressing the SREBP pathway prevents HCC. This study identifies a previously underappreciated role of the SREBP pathway in HCC and suggests a novel metabolic strategy to control liver cancer. (Hepatology 2017;65:1936-1947).

Sterol regulatory element-binding protein 1 inhibitors decrease pancreatic cancer cell viability and proliferation

Sterol regulatory element-binding protein1 (SREBP1) is a key regulatory factor that controls lipid homeostasis. Overactivation of SREBP1 and elevated lipid biogenesis are considered the major characteristics in malignancies of prostate cancer, endometrial cancer, and glioblastoma. However, the impact of SREBP1 activation in the progression of pancreatic cancer has not been explored. The present study examines the effect of suppression of SREBP1 activation by its inhibitors like fatostatin and PF429242 besides analyzing the impact of inhibitory effects on SREBP1 downstream signaling cascade such as fatty acid synthase (FAS), hydroxymethylglutaryl-CoA reductase (HMGCoAR), stearoyl-CoA desaturase-1 (SCD-1), and tumor suppressor protein p53 in MIA PaCa-2 pancreatic cancer cells. Both fatostatin and PF429242 inhibited the growth of MIA PaCa-2 cells in a time and concentration-dependent manner with maximal inhibition attained at 72 h time period with IC₅₀ values of 14.5 μM and 24.5 μM respectively. Detailed Western blot analysis performed using fatostatin and PF429242 at 72 h time point led to significant decrease in the levels of the active form of SREBP1 and its downstream signaling proteins such as FAS, SCD-1 and HMGCoAR and the mutant form of tumor suppressor protein, p53, levels in comparison to the levels observed in vehicle treated control group of MIA PaCa-2 pancreatic cells over the same time period. Our in vitro data suggest that SREBP1 may contribute to pancreatic tumor growth and its inhibitors could be considered as a potential target in the management of pancreatic cancer cell proliferation.

Understanding tumor anabolism and patient catabolism in cancer-associated cachexia

Cachexia is a multifactorial paraneoplastic syndrome commonly associated with advanced stages of cancer. Cachexia is responsible for poor responses to antitumoral treatment and death in close to one-third of affected patients. There is still an incomplete understanding of the metabolic dysregulation induced by a tumor that leads to the appearance and persistence of cachexia. Furthermore, cachexia is irreversible, and there are currently no guidelines for its diagnosis or treatments for it. In this review, we aim to discuss the current knowledge about cancer-associated cachexia, starting with generalities about cancer as the generator of this syndrome, then analyzing the characteristics of cachexia at the biochemical and metabolic levels in both the tumor and the patient, and finally discussing current therapeutic approaches to treating cancer-associated cachexia.

Lipid quantification by Raman microspectroscopy as a potential biomarker in prostate cancer

Metastatic castration-resistant prostate cancer (mCRPC) remains incurable and is one of the leading causes of cancer-related death among American men. Therefore, detection of prostate cancer (PCa) at early stages may reduce PCa-related mortality in men. We show that lipid quantification by vibrational Raman Microspectroscopy and Biomolecular Component Analysis may serve as a potential biomarker in PCa. Transcript levels of lipogenic genes including sterol regulatory element-binding protein-1 (SREBP-1) and its downstream effector fatty acid synthase (FASN), and rate-limiting enzyme acetyl CoA carboxylase (ACACA) were upregulated corresponding to both Gleason score and pathologic T stage in the PRAD TCGA cohort. Increased lipid accumulation in late-stage transgenic adenocarcinoma of mouse prostate (TRAMP) tumors compared to early-stage TRAMP and normal prostate tissues were observed. FASN along with other lipogenesis enzymes, and SREBP-1 proteins were upregulated in TRAMP tumors compared to wild-type prostatic tissues. Genetic alterations of key lipogenic genes predicted the overall patient survival using TCGA PRAD cohort. Correlation between lipid accumulation and tumor stage provides quantitative marker for PCa diagnosis. Thus, Raman spectroscopy-based lipid quantification could be a sensitive and reliable tool for PCa diagnosis and staging.

Kukoamine A attenuates insulin resistance and fatty liver through downregulation of Srebp-1c

Nonalcoholic fatty liver disease (NAFLD) refers to a pathological condition of hepatic steatosis. Insulin resistance is believed to be the key mechanism mediating initial accumulation of fat in the liver, resulting in hepatic steatosis. Kukoamine A (KuA), a spermine alkaloid, is a major bioactive component extracted from the root barks of Lycium chinense (L. chinense) Miller. In the current study, we aimed to explore the possible effect of KuA on insulin resistance and fatty liver. We showed that KuA significantly inhibited the increase of fasting blood glucose level and insulin level, and the glucose levels in response to glucose and insulin load in HFD-fed mice, which was in a dose-dependent manner. KuA dose-dependently decreased the histological injury of liver, levels of hepatic triglyceride (TG), and serum AST and ALT activities in HFD-fed mice. The increase of serum levels of TNFɑ, IL-1β, IL-6 and C reactive protein in HFD-fed mice was inhibited by KuA. HFD feeding-induced increase of hepatic expression of Srebp-1c and its target genes, including fatty acid synthase (FAS) and acetyl CoA carboxylase 1 (ACC1), was significantly inhibited by KuA. Moreover, upregulation of Srebp-1c notably inhibited KuA-induced improvement of insulin-stimulated glucose uptake, decrease of lipid accumulation and H₂O₂ level in palmitic acid-treated AML-12 cells. In conclusion, we reported that KuA inhibited Srebp-1c and downstream genes expression and resulted in inhibition of lipid accumulation, inflammation, insulin resistance and oxidative stress. Overall, our results provide a better understanding of the pharmacological activities of KuA against insulin resistance and hepatic steatosis.

Anti-Cancer Effects of Green Tea by Either Anti- or Pro- Oxidative Mechanisms

Tea derived from the leaves and buds of Camellia sinensis (Theaceae) is consumed worldwide. Green tea contains various components with specific health-promoting effects, and is believed to exert protective effects against diseases including cancer, diabetes and hepatitis, as well as obesity. Of the various tea components, the polyphenol catechins have been the subject of extensive investigation and among the catechins, (-)-epigallocatechin gallate has the strongest bioactivity in most cases. Our research group has postulated that hepatocyte nuclear factor-4α, sterol regulatory element-binding proteins, and tumor necrosis factor-α are targets of green tea constituents including (-)-epigallocatechin gallate for their anti-diabetes, anti-obesity, and anti-hepatitis effects, respectively. Published papers were reviewed to determine whether the observed changes in these factors can be correlated with anti-cancer effects of green tea. Two major action mechanisms of (-)-epigallocatechin gallate have been proposed; one associated with its anti-oxidative properties and the other with its pro-oxidative activity. When reactive oxygen species are assumed to be involved, our findings that (-)-epigallocatechin gallate down- regulated hepatocyte nuclear factor-4α, sterol regulatory element-binding proteins, and tumor necrosis factor-α may explain the anti-cancer effect of green tea as well. However, further studies are required to elucidate which determinant directs (-)-epigallocatechin gallate action as an anti-oxidant or a pro-oxidant for favorable activity.

Key Genes in Stomach Adenocarcinoma Identified via Network Analysis of RNA-Seq Data

RNA-seq data of stomach adenocarcinoma (STAD) were analyzed to identify critical genes in STAD. Meanwhile, relevant small molecule drugs, transcription factors (TFs) and microRNAs (miRNAs) were also investigated. Gene expression data of STAD were downloaded from The Cancer Genome Atlas (TCGA). Differential analysis was performed with package edgeR. Relationships with correlation coefficient > 0.6 were retained in the gene co-expression network. Functional enrichment analysis was performed for the genes in the network with DAVID and KOBASS 2.0. Modules were identified using Cytoscape. Relevant small molecules drugs, transcription factors (TFs) and microRNAs (miRNAs) were revealed by using CMAP and WebGestalt databases. A total of 520 DEGs were identified between 285 STAD samples and 33 normal controls, including 244 up-regulated and 276 down-regulated genes. A gene co-expression network containing 53 DEGs and 338 edges was constructed, the genes of which were significantly enriched in focal adhesion, ECM-receptor interaction and vascular smooth muscle contraction pathways. Three modules were identified from the gene co-expression network and they were associated with skeletal system development, inflammatory response and positive regulation of cellular process, respectively. A total of 20 drugs, 9 TFs and 6 miRNAs were acquired that may regulate the DEGs. NFAT-COL1A1/ANXA1, HSF2-FOS, SREBP-IL1RN and miR-26-COL5A2 regulation axes may be important mechanisms for STAD.

Farnesoid X receptor ligand CDCA suppresses human prostate cancer cells growth by inhibiting lipid metabolism via targeting sterol response element binding protein 1

AIM

A wealth of studies have demonstrated that abnormal cellular lipid metabolism plays an important role in prostate cancer (PCa) development. Therefore, manipulating lipid metabolism is a potential PCa therapy strategy. In this study, our goal is to investigate the role of farnesoid X receptor (FXR) in regulating the proliferation and lipid metabolism of human PCa cells following its ligand chenodexycholic acid (CDCA) treatment.

METHODS

Oil Red O was used to stain lipid contents in PCa cells, and siRNA knockdown was performed to deplete FXR expression. To study the cell proliferation when treated by CDCA or FXR knockdown, cell counting kit 8 (CCK8) was adopted to evaluate tumor cell growth. Western blot was used for protein analysis.

RESULTS

Our data suggest that activation of FXR by CDCA reduces lipid accumulation and significantly inhibits cells proliferation in prostate tumor cells. Instead, CDCA treatment doesn't affect normal prostate epithelial RWPE-1 cells growth in vitro. FXR activation decreases mRNA and protein levels of sterol regulatory element binding protein 1 (SREBP1) and some other key regulators involved in lipid metabolism. Depletion of FXR by siRNA attenuates the inhibitory effects.

CONCLUSION

Our study indicates that activation of FXR inhibits lipid metabolism via SREBP1 pathway and further suppresses prostate tumor growth in vitro.

The interplay between cell signalling and the mevalonate pathway in cancer

The mevalonate (MVA) pathway is an essential metabolic pathway that uses acetyl-CoA to produce sterols and isoprenoids that are integral to tumour growth and progression. In recent years, many oncogenic signalling pathways have been shown to increase the activity and/or the expression of MVA pathway enzymes. This Review summarizes recent advances and discusses unique opportunities for immediately targeting this metabolic vulnerability in cancer with agents that have been approved for other therapeutic uses, such as the statin family of drugs, to improve outcomes for cancer patients.

Anti-cancer efficacy of SREBP inhibitor, alone or in combination with docetaxel, in prostate cancer harboring p53 mutations

Mutant p53 proteins (mutant p53s) have oncogenic gain-of-function properties correlated with tumor grade, castration resistance, and prostate cancer (PCa) tumor recurrence. Docetaxel is a standard first-line treatment for metastatic castration-resistant PCa (mCRPC) after the failure of hormone therapy. However, most mCRPC patients who receive docetaxel experience only transient benefits and rapidly develop incurable drug resistance, which is closely correlated with the p53 mutation status. Mutant p53s were recently reported to regulate the metabolic pathways via sterol regulatory element-binding proteins (SREBPs). Therefore, targeting the SREBP metabolic pathways with docetaxel as a combination therapy may offer a potential strategy to improve anti-tumor efficacy and delay cellular drug resistance in mCRPC harboring mutant p53s. Our previous data showed that fatostatin, a new SREBP inhibitor, inhibited cell proliferation and induced apoptosis in androgen receptor (AR)-positive PCa cell lines and xenograft mouse models. In this study, we demonstrated that mutant p53s activate the SREBP-mediated metabolic pathways in metastatic AR-negative PCa cells carrying mutant p53s. By blocking the SREBP pathways, fatostatin inhibited cell growth and induced apoptosis in metastatic AR-negative PCa cells harboring mutant p53s. Furthermore, the combination of fatostatin and docetaxel resulted in greater proliferation inhibition and apoptosis induction compared with single agent treatment in PCa cells in vitro and in vivo, especially those with mutant p53s. These data suggest for the first time that fatostatin alone or in combination with docetaxel could be exploited as a novel and promising therapy for metastatic PCa harboring p53 mutations.

The emerging role of obesity, diet and lipid metabolism in prostate cancer

Obesity is associated with an increased risk of a number of serious medical conditions, including cancer. As far as prostate cancer is concerned, obesity is associated with an increased risk of high-grade tumors, which is possibly related to lower androgen levels. Diet may also affect prostate cancer risk since countries with a higher dietary fat intake also present higher prostate cancer mortality rates. Interestingly, prostate cancer is associated with a number of metabolic alterations that may provide valuable diagnostic and therapeutic targets. This review explores the available clinical as well as biological evidence supporting the relationship between obesity, diet, alteration in metabolic pathways and prostate cancer.

Refinement of the androgen response element based on ChIP-Seq in androgen-insensitive and androgen-responsive prostate cancer cell lines

Sequence motifs are short, recurring patterns in DNA that can mediate sequence-specific binding for proteins such as transcription factors or DNA modifying enzymes. The androgen response element (ARE) is a palindromic, dihexameric motif present in promoters or enhancers of genes targeted by the androgen receptor (AR). Using chromatin immunoprecipitation sequencing (ChIP-Seq) we refined AR-binding and AREs at a genome-scale in androgen-insensitive and androgen-responsive prostate cancer cell lines. Model-based searches identified more than 120,000 ChIP-Seq motifs allowing for expansion and refinement of the ARE. We classified AREs according to their degeneracy and their transcriptional involvement. Additionally, we quantified ARE utilization in response to somatic copy number amplifications, AR splice-variants, and steroid treatment. Although imperfect AREs make up 99.9% of the motifs, the degree of degeneracy correlates negatively with validated transcriptional outcome. Weaker AREs, particularly ARE half sites, benefit from neighboring motifs or cooperating transcription factors in regulating gene expression. Taken together, ARE full sites generate a reliable transcriptional outcome in AR positive cells, despite their low genome-wide abundance. In contrast, the transcriptional influence of ARE half sites can be modulated by cooperating factors.

Lipid Droplets: A Key Cellular Organelle Associated with Cancer Cell Survival under Normoxia and Hypoxia

The Warburg effect describes the phenomenon by which cancer cells obtain energy from glycolysis even under normoxic (O₂-sufficient) conditions. Tumor tissues are generally exposed to hypoxia owing to inefficient and aberrant vasculature. Cancer cells have multiple molecular mechanisms to adapt to such stress conditions by reprogramming the cellular metabolism. Hypoxia-inducible factors are major transcription factors induced in cancer cells in response to hypoxia that contribute to the metabolic changes. In addition, cancer cells within hypoxic tumor areas have reduced access to serum components such as nutrients and lipids. However, the effect of such serum factor deprivation on cancer cell biology in the context of tumor hypoxia is not fully understood. Cancer cells are lipid-rich under normoxia and hypoxia, leading to the increased generation of a cellular organelle, the lipid droplet (LD). In recent years, the LD-mediated stress response mechanisms of cancer cells have been revealed. This review focuses on the production and functions of LDs in various types of cancer cells in relation to the associated cellular environment factors including tissue oxygenation status and metabolic mechanisms. This information will contribute to the current understanding of how cancer cells adapt to diverse tumor environments to promote their survival.

MNX1 Is Oncogenically Upregulated in African-American Prostate Cancer

Incidence and mortality rates for prostate cancer are higher in African-American (AA) men than in European-American (EA) men, but the biologic basis for this disparity is unclear. We carried out a detailed analysis of gene expression changes in prostate cancer compared with their matched benign tissues in a cohort of AA men and compared them with existing data from EA men. In this manner, we identified MNX1 as a novel oncogene upregulated to a relatively greater degree in prostate cancer from AA men. Androgen and AKT signaling play a central role in the pathogenesis of prostate cancer and we found that both of these signaling pathways increased MNX1 expression. MNX1 in turn upregulated lipid synthesis by stimulating expression of SREBP1 and fatty acid synthetase. Our results define MNX1 as a novel targetable oncogene increased in AA prostate cancer that is associated with aggressive disease. Cancer Res; 76(21); 6290-8. ©2016 AACR.

Biomarker Discovery in Human Prostate Cancer: an Update in Metabolomics Studies

Prostate cancer (PCa) is the most frequently diagnosed cancer and the second leading cause of cancer death among men in Western countries. Current screening techniques are based on the measurement of serum prostate specific antigen (PSA) levels and digital rectal examination. A decisive diagnosis of PCa is based on prostate biopsies; however, this approach can lead to false-positive and false-negative results. Therefore, it is important to discover new biomarkers for the diagnosis of PCa, preferably noninvasive ones. Metabolomics is an approach that allows the analysis of the entire metabolic profile of a biological system. As neoplastic cells have a unique metabolic phenotype related to cancer development and progression, the identification of dysfunctional metabolic pathways using metabolomics can be used to discover cancer biomarkers and therapeutic targets. In this study, we review several metabolomics studies performed in prostatic fluid, blood plasma/serum, urine, tissues and immortalized cultured cell lines with the objective of discovering alterations in the metabolic phenotype of PCa and thus discovering new biomarkers for the diagnosis of PCa. Encouraging results using metabolomics have been reported for PCa, with sarcosine being one of the most promising biomarkers identified to date. However, the use of sarcosine as a PCa biomarker in the clinic remains a controversial issue within the scientific community. Beyond sarcosine, other metabolites are considered to be biomarkers for PCa, but they still need clinical validation. Despite the lack of metabolomics biomarkers reaching clinical practice, metabolomics proved to be a powerful tool in the discovery of new biomarkers for PCa detection.

SREBP-1 is an independent prognostic marker and promotes invasion and migration in breast cancer

Re-programming of lipogenic signaling has been previously demonstrated to result in significant alterations in tumor cell pathology. Sterol regulatory element-binding protein 1 (SREBP-1) is a known transcription factor of lipogenic genes. Despite the fact that its functions in proliferation and apoptosis have been elucidated in recent studies, its role in tumor cell migration and invasion, particularly in breast cancer, remains unclear. In present study, the messenger RNA and protein expression levels of SREBP-1 in cancer tissues were observed to be overexpressed compared with those in matched para-cancerous tissues (P<0.01). SREBP-1 level was highly positively correlated with tumor differentiation (P<0.001), tumor-node-metastasis stage (P=0.044) and lymph node metastasis (P<0.001). High expression of SREBP-1 predicted poor prognosis in patients with breast cancer. Additionally, multivariate analysis revealed that SREBP-1 was an independent factor of 5-year overall and disease-specific survival in breast cancer patients (P<0.01). In vitro studies revealed that the suppression of SREBP-1 expression in both MDA-MB-231 and MCF7 cells significantly inhibited cell migration and invasion (P<0.01). The present data indicate that SREBP-1 plays a critical role in breast cancer migration and invasion, and may serve as a prognostic marker of this malignancy.

The metastasis inducer CCN1 (CYR61) activates the fatty acid synthase (FASN)-driven lipogenic phenotype in breast cancer cells

The angiogenic inducer CCN1 (Cysteine-rich 61, CYR61) is differentially activated in metastatic breast carcinomas. However, little is known about the precise mechanisms that underlie the pro-metastatic actions of CCN1. Here, we investigated the impact of CCN1 expression on fatty acid synthase (FASN), a metabolic oncogene thought to provide cancer cells with proliferative and survival advantages. Forced expression of CCN1 in MCF-7 cells robustly up-regulated FASN protein expression and also significantly increased FASN gene promoter activity 2- to 3-fold, whereas deletion of the sterol response element-binding protein (SREBP) binding site in the FASN promoter completely abrogated CCN1-driven transcriptional activation. Pharmacological blockade of MAPK or PI-3'K activation similarly prevented the ability of CCN1 to induce FASN gene activation. Pharmacological inhibition of FASN activity with the mycotoxin cerulenin or the small compound C75 reversed CCN1-induced acquisition of estrogen independence and resistance to hormone therapies such as tamoxifen and fulvestrant in anchorage-independent growth assays. This study uncovers FASNdependent endogenous lipogenesis as a new mechanism controlling the metastatic phenotype promoted by CCN1. Because estrogen independence and progression to a metastatic phenotype are hallmarks of therapeutic resistance and mortality in breast cancer, this previously unrecognized CCN1-driven lipogenic phenotype represents a novel metabolic target to clinically manage metastatic disease progression.

Silibinin: a potential old drug for cancer therapy

INTRODUCTION

Silibinin is mixture of flavonolignans extracted from milk thistle and often has been used in the treatment of acute and chronic liver disorders caused by toxins, drug, alcohol and hepatitis and gall bladder disorders for its antioxidant and hepatoprotective properties. Areas covered: However, increasing evidence suggest that silibinin is not solely limited in the treatment of these diseases. Further research suggests that silymarin may function diversely and may serve as a novel therapy for cancer therapy, such as lung cancer, prostatic cancer, colon cancer, breast cancer, bladder cancer and hepatocellular carcinoma by regulating cancer cells growth, proliferation, apoptosis, angiogenesis and many other mechanism. Expert commentary: In this review, in order to provide potential new treatment for these cancer, we summarize the recent anti-cancer findings of silibinin in these cancer and clarify the mechanisms of this effect.

p53 attenuates AKT signaling by modulating membrane phospholipid composition

The p53 tumor suppressor is the central component of a complex network of signaling pathways that protect organisms against the propagation of cells carrying oncogenic mutations. Here we report a previously unrecognized role of p53 in membrane phospholipids composition. By repressing the expression of stearoyl-CoA desaturase 1, SCD, the enzyme that converts saturated to mono-unsaturated fatty acids, p53 causes a shift in the content of phospholipids with mono-unsaturated acyl chains towards more saturated phospholipid species, particularly of the phosphatidylinositol headgroup class. This shift affects levels of phosphatidylinositol phosphates, attenuates the oncogenic AKT pathway, and contributes to the p53-mediated control of cell survival. These findings expand the p53 network to phospholipid metabolism and uncover a new molecular pathway connecting p53 to AKT signaling.

Global gene deregulations in FASN silenced retinoblastoma cancer cells: molecular and clinico-pathological correlations

Activation of fatty acid synthase (FASN) enzyme in the de novo lipogenic pathway has been reported in various cancers including retinoblastoma (RB), a pediatric ocular cancer. The present study investigates lipogenesis-dependent survival of RB cancer cells and the associated molecular pathways in FASN silenced RB cells. The siRNA-mediated FASN gene knockdown in RB cancer cells (Y79, WERI RB1) repressed FASN mRNA and protein expressions, and decreased cancer cell viability. Global gene expression microarray analysis was performed in optimized FASN siRNA transfected and untransfected RB cells. Deregulation of various downstream cell signaling pathways such as EGFR (n = 55 genes), TGF-beta (n = 45 genes), cell cycle (n = 41 genes), MAPK (n = 39 genes), lipid metabolism (n = 23 genes), apoptosis (n = 21 genes), GPCR signaling (n = 21 genes), and oxidative phosporylation (n = 18 genes) were observed. The qRT-PCR validation in FASN knockdown RB cells revealed up-regulation of ANXA1, DAPK2, and down-regulation of SKP2, SREBP1c, RXRA, ACACB, FASN, HMGCR, USP2a genes that favored the anti-cancer effect of lipogenic inhibition in RB. The expression of these genes in primary RB tumor tissues were correlated with FASN expression, based on their clinico-pathological features. The differential phosphorylation status of the various PI3K/AKT pathway proteins (by western analysis) indicated that the FASN gene silencing indeed mediated apoptosis in RB cells through the PI3K/AKT pathway. Scratch assay clearly revealed that FASN silencing reduced the invading property of RB cancer cells. Dependence of RB cancer cells on lipid metabolism for survival and progression is implicated. Thus targeting FASN is a promising strategy in RB therapy.

Modeling of Cancer Classifier to Predict Site of Origin

Cancer classification based on site of origin is very significant research issue for prediction and treatment of cancer. This paper is addressing the problem of cancer classification for Homo Sapiens genes composed of amino acid chain. Cancer gene network is realized by equivalent electrical circuits based on hydrophilic/ hydrophobic property of amino acid and a classifier is modeled to determine the cancer origin. The phase value, peak gain value and shape of Nyquist curve of network model are investigated to characterize different types of cancer gene origins. The model achieves 81.09% of classification accuracy and proves to be more sensitive and simple, since it shows 69% better performance compare to the existing nucleotide based method. The proposed classifier successfully predicts the site of origin of 93 cancer gene samples.

Androgen control of lipid metabolism in prostate cancer: novel insights and future applications

One of the most typical hallmarks of prostate cancer cells is their exquisite dependence on androgens, which is the basis of the widely applied androgen deprivation therapy. Among the variety of key cellular processes and functions that are regulated by androgens, lipid metabolism stands out by its complex regulation and its many intricate links with cancer cell biology. Here, we review our current knowledge on the links between androgens and lipid metabolism in prostate cancer, and highlight recent developments and insights into the links between key oncogenic stimuli and altered lipid synthesis and/or uptake that may hold significant potential for biomarker development and provide new vulnerabilities for therapeutic intervention.

Metabolomic profiling of hormone-dependent cancers: a bird's eye view

Hormone-dependent cancers present a significant public health challenge, because they are among the most common cancers in the world. One factor associated with cancer development and progression is metabolic reprogramming. By understanding these alterations, we can identify potential markers and novel biochemical therapeutic targets. Metabolic profiling is an advanced technology that allows investigators to assess low-molecular-weight compounds that reflect physiological alterations. Current research in metabolomics on prostate (PCa) and breast cancer (BCa) have made great strides in uncovering specific metabolic pathways that are associated with cancer development, progression, and resistance. In this review, we highlight some of the major findings and potential therapeutic advances that have been reported utilizing this technology.

LMP1 Increases Expression of NADPH Oxidase (NOX) and Its Regulatory Subunit p22 in NP69 Nasopharyngeal Cells and Makes Them Sensitive to a Treatment by a NOX Inhibitor

Oxidative stress is thought to contribute to cancer development. Epstein–Barr virus (EBV) and its encoded oncoprotein, latent membrane protein 1 (LMP1), are closely associated with the transformation of nasopharyngeal carcinoma (NPC) and Burkitt’s lymphoma (BL). In this study, we used LMP1-transformed NP cells and EBV-related malignant cell lines to assess the effects of LMP1 on reactive oxygen species (ROS) accumulation and glycolytic activity. Using NPC tissue samples and a tissue array to address clinical implications, we report that LMP1 activates NAD(P)H oxidases to generate excessive amount of ROS in EBV-related malignant diseases. By evaluating NAD(P)H oxidase (NOX) subunit expression, we found that the expression of the NAD(P)H oxidase regulatory subunit p22^phox was significantly upregulated upon LMP1-induced transformation. Furthermore, this upregulation was mediated by the c-Jun N-terminal kinase (JNK) pathway. In addition, LMP1 markedly stimulated anaerobic glycolytic activity through the PI3K/Akt pathway. Additionally, in both NPC cells and tissue samples, p22^phox expression correlated with LMP1 expression. The NAD(P)H oxidase inhibitor diphenyleneiodonium (DPI) also exerted a marked cytotoxic effect in LMP1-transformed and malignant cells, providing a novel strategy for anticancer therapy.

Silibinin inhibits aberrant lipid metabolism, proliferation and emergence of androgen-independence in prostate cancer cells via primarily targeting the sterol response element binding protein 1

Prostate cancer (PCA) kills thousands of men every year, demanding additional approaches to better understand and target this malignancy. Recently, critical role of aberrant lipogenesis is highlighted in prostate carcinogenesis, offering a unique opportunity to target it to reduce PCA. Here, we evaluated efficacy and associated mechanisms of silibinin in inhibiting lipid metabolism in PCA cells. At physiologically achievable levels in human, silibinin strongly reduced lipid and cholesterol accumulation specifically in human PCA cells but not in non-neoplastic prostate epithelial PWR-1E cells. Silibinin also decreased nuclear protein levels of sterol regulatory element binding protein 1 and 2 (SREBP1/2) and their target genes only in PCA cells. Mechanistically, silibinin activated AMPK, thereby increasing SREBP1 phosphorylation and inhibiting its nuclear translocation; AMPK inhibition reversed silibinin-mediated decrease in nuclear SREBP1 and lipid accumulation. Additionally, specific SREBP inhibitor fatostatin and stable overexpression of SREBP1 further confirmed the central role of SREBP1 in silibinin-mediated inhibition of PCA cell proliferation and lipid accumulation and cell cycle arrest. Importantly, silibinin also inhibited synthetic androgen R1881-induced lipid accumulation and completely abrogated the development of androgen-independent LNCaP cell clones via targeting SREBP1/2. Together, these mechanistic studies suggest that silibinin would be effective against PCA by targeting critical aberrant lipogenesis.

The fatty acid synthase inhibitor triclosan: repurposing an anti-microbial agent for targeting prostate cancer

Inhibition of FASN has emerged as a promising therapeutic target in cancer, and numerous inhibitors have been investigated. However, severe pharmacological limitations have challenged their clinical testing. The synthetic FASN inhibitor triclosan, which was initially developed as a topical antibacterial agent, is merely affected by these pharmacological limitations. Yet, little is known about its mechanism in inhibiting the growth of cancer cells. Here we compared the cellular and molecular effects of triclosan in a panel of eight malignant and non-malignant prostate cell lines to the well-known FASN inhibitors C75 and orlistat, which target different partial catalytic activities of FASN. Triclosan displayed a superior cytotoxic profile with a several-fold lower IC50 than C75 or orlistat. Structure-function analysis revealed that alcohol functionality of the parent phenol is critical for inhibitory action. Rescue experiments confirmed that end product starvation was a major cause of cytotoxicity. Importantly, triclosan, C75 and orlistat induced distinct changes to morphology, cell cycle, lipid content and the expression of key enzymes of lipid metabolism, demonstrating that inhibition of different partial catalytic activities of FASN activates different metabolic pathways. These finding combined with its well-documented pharmacological safety profile make triclosan a promising drug candidate for the treatment of prostate cancer.

Keap1/Nrf2 pathway in the frontiers of cancer and non-cancer cell metabolism

Cancer cells adapt their metabolism to their increased needs for energy and substrates for protein, lipid and nucleic acid synthesis. Nuclear erythroid factor 2-like 2 (Nrf2) pathway is usually activated in cancers and has been suggested to promote cancer cell survival mainly by inducing a large battery of cytoprotective genes. This mini review focuses on metabolic pathways, beyond cytoprotection, which can be directly or indirectly regulated by Nrf2 in cancer cells to affect their survival. The pentose phosphate pathway (PPP) is enhanced by Nrf2 in cancers and aids their growth. PPP has also been found to be up-regulated in non-cancer tissues and other pathways, such as de novo lipogenesis, have been found to be repressed after activation of the Nrf2 pathway. The importance of these Nrf2-regulated metabolic pathways in cancer compared with non-cancer state remains to be determined. Last but not least, the importance of context about Nrf2 and cancer is highlighted as the Nrf2 pathway may be activated in cancers but its pharmacological activators are useful in chemoprevention.

SREBP-1c overactivates ROS-mediated hepatic NF-κB inflammatory pathway in dairy cows with fatty liver

Dairy cows with fatty liver are characterized by hepatic lipid accumulation and a severe inflammatory response. Sterol receptor element binding protein-1c (SREBP-1c) and nuclear factor κB (NF-κB) are components of the main pathways for controlling triglyceride (TG) accumulation and inflammatory levels, respectively. A previous study demonstrated that hepatic inflammatory levels are positively correlated with hepatic TG content. We therefore speculated that SREBP-1c might play an important role in the overactivation of the hepatic NF-κB inflammatory pathway in cows with fatty liver. Compared with healthy cows, cows with fatty liver exhibited severe hepatic injury and high blood concentrations of the inflammatory cytokines TNF-α, IL-6 and IL-1β. Hepatic SREBP-1c-mediated lipid synthesis and the NF-κB inflammatory pathway were both overinduced in cows with fatty liver. In vitro, treatment with non-esterified fatty acids (NEFA) further increased SREBP-1c expression and NF-κB pathway activation, which then promoted TG and inflammatory cytokine synthesis. SREBP-1c overexpression overactivated the NF-κB inflammatory pathway in hepatocytes by increasing ROS content and not through TLR4. Furthermore, SREBP-1c silencing decreased ROS content and further attenuated the activation of the NEFA-induced NF-κB pathway, thereby decreasing TNF-α, IL-6 and IL-1β synthesis. SREBP-1c-overexpressing mice exhibited hepatic steatosis and an overinduced hepatic NF-κB pathway. Taken together, these results indicate that SREBP-1c enhances the NEFA-induced overactivation of the NF-κB inflammatory pathway by increasing ROS in cow hepatocytes, thereby further increasing hepatic inflammatory injury in cows with fatty liver.

Metabolomic profiling for the identification of novel diagnostic markers in prostate cancer

Metabolomic profiling offers a powerful methodology for understanding the perturbations of biochemical systems occurring during a disease process. During neoplastic transformation, prostate cells undergo metabolic reprogramming to satisfy the demands of growth and proliferation. An early event in prostate cell transformation is the loss of capacity to accumulate zinc. This change is associated with a higher energy efficiency and increased lipid biosynthesis for cellular proliferation, membrane formation and cell signaling. Moreover, recent studies have shown that sarcosine, an N-methyl derivative of glycine, was significantly increased during disease progression from normal to localized to metastatic prostate cancer. Mapping the metabolomic profiles to their respective biochemical pathways showed an upregulation of androgen-induced protein synthesis, an increased amino acid metabolism and a perturbation of nitrogen breakdown pathways, along with high total choline-containing compounds and phosphocholine levels. In this review, the role of emerging biomarkers is summarized, based on the current understanding of the prostate cancer metabolome.

Broad Anti-tumor Activity of a Small Molecule that Selectively Targets the Warburg Effect and Lipogenesis

Malignant cells exhibit aerobic glycolysis (the Warburg effect) and become dependent on de novo lipogenesis, which sustains rapid proliferation and resistance to cellular stress. The nuclear receptor liver-X-receptor (LXR) directly regulates expression of key glycolytic and lipogenic genes. To disrupt these oncogenic metabolism pathways, we designed an LXR inverse agonist SR9243 that induces LXR-corepressor interaction. In cancer cells, SR9243 significantly inhibited the Warburg effect and lipogenesis by reducing glycolytic and lipogenic gene expression. SR9243 induced apoptosis in tumors without inducing weight loss, hepatotoxicity, or inflammation. Our results suggest that LXR inverse agonists may be an effective cancer treatment approach.

Understanding the biology of reactive oxygen species and their link to cancer: NADPH oxidases as novel pharmacological targets

Reactive oxygen species (ROS), the cellular products of myriad physiological processes, have long been understood to lead to cellular damage if produced in excess and to be a causative factor in cancer through the oxidation and nitration of various macromolecules. Reactive oxygen species influence various hallmarks of cancer, such as cellular proliferation and angiogenesis, through the promotion of cell signalling pathways intrinsic to these processes and can also regulate the function of key immune cells, such as macrophages and regulatory T cells, which promote angiogenesis in the tumour environment. Herein we emphasize the family of NADPH oxidase enzymes as the most likely source of ROS, which promote angiogenesis and tumourigenesis through signalling pathways within endothelial, immune and tumour cells. In this review we focus on the pharmacological inhibitors of NADPH oxidases and suggest that, compared with traditional anti-oxidants, they are likely to offer better alternatives for suppression of tumour angiogenesis. Despite the emerging enthusiasm towards the use of NADPH oxidase inhibitors for cancer therapy, this field is still in its infancy; in particular, there is a glaring lack of knowledge of the roles of NADPH oxidases in in vivo animal models and in human cancers. Certainly a clearer understanding of the relevant signalling pathways influenced by NADPH oxidases during angiogenesis in cancer is likely to yield novel therapeutic approaches.

[6]-Gingerol inhibits de novo fatty acid synthesis and carnitine palmitoyltransferase-1 activity which triggers apoptosis in HepG2

The de novo fatty acid synthesis catalyzed by key lipogenic enzymes, including fatty acid synthase (FASN) has emerged as one of the novel targets of anti-cancer approaches. The present study explored the possible inhibitory efficacy of [6]-gingerol on de novo fatty acid synthesis associated with mitochondrial-dependent apoptotic induction in HepG2 cells. We observed a dissipation of mitochondrial membrane potential accompanied by a reduction of fatty acid levels. [6]-gingerol administration manifested inhibition of FASN expression, indicating FASN is a major target of [6]-gingerol inducing apoptosis in HepG2 cells. Indeed, we found that increased ROS generation could likely be a mediator of the anti-cancer effect of [6]-gingerol. A reduction of fatty acid levels and induction of apoptosis were restored by inhibition of acetyl-CoA carboxylase (ACC) activity, suggesting an accumulation of malonyl-CoA level could be the major cause of apoptotic induction of [6]-gingerol in HepG2 cells. The present study also showed that depletion of fatty acid following [6]-gingerol treatment caused an inhibitory effect on carnitine palmitoyltransferase-1 activity (CPT-1), whereas C75 augmented CPT-1 activity, indicating that [6]-gingerol exhibits the therapeutic benefit on suppression of fatty acid β-oxidation.

SREBP1 regulates tumorigenesis and prognosis of pancreatic cancer through targeting lipid metabolism

Sterol regulatory element-binding protein 1 (SREBP1) is a known transcription factor of lipogenic genes, which plays important roles in regulating de novo lipogenesis. Accumulating evidences indicate SREBP1 is involved in tumorigenesis, yet its role in pancreatic cancer remains unclear. Here, we explored the expression characteristic and function of SREBP1 in pancreatic cancer. Analysis of 60 patients with pancreatic ducat cancer showed that SREBP1 level was significantly higher in pancreatic cancer than that in adjacent normal tissues. High expression of SREBP1 predicted poor prognosis in patients with pancreatic cancer. Multivariate analysis revealed that SREBP1 was an independent factor affecting overall survival. SREBP1 silencing resulted in proliferation inhibition and induction of apoptosis in pancreatic cancer cells. Mechanistically, lipogenic genes (acetyl-CoA carboxylase (ACC), fatty acid synthase (FASN), and stearoyl-CoA desaturase-1 (SCD1)) and de novo lipogenesis were promoted by SREBP1. Inhibition of lipogenic genes through specific inhibitors ablated SREBP1-mediated growth regulation. Furthermore, depletion of SREBP1 could suppress lipid metabolism and tumor growth in vivo. Our results indicate that SREBP1 had important role in tumor progression and appears to be a novel prognostic marker for pancreatic cancer.

Dietary lipids and adipocytes: potential therapeutic targets in cancers

Lipids play an important role to support the rapid growth of cancer cells, which can be derived from both the endogenous synthesis and exogenous supplies. Enhanced de novo fatty acid synthesis and mobilization of stored lipids in cancer cells promote tumorigenesis. Besides, lipids and fatty acids derived from diet or transferred from neighboring adipocytes also influence the proliferation and metastasis of cancer cells. Indeed, the pathogenic roles of adipocytes in the tumor microenvironment have been recognized recently. The adipocyte-derived mediators or the cross talk between adipocytes and cancer cells in the microenvironment is gaining attention. This review will focus on the impacts of lipids on cancers and the pathogenic roles of adipocytes in tumorigenesis and discuss the possible anticancer therapeutic strategies targeting lipids in the cancer cells.