Loss of stearoyl-CoA desaturase expression is a frequent event in prostate carcinoma

Lipid metabolism in cancer: A systematic review

Preclinical studies and clinical trials have emphasized the decisive role of lipid metabolism in tumor proliferation and metastasis. This systematic review aimed to explore the existing literature to evaluate the role and significance of the genes and pathways most commonly involved in the regulation of lipid metabolism in cancer. The literature search was performed as per Preferred Reporting Items for Systematic Reviews and Meta-analyses. Approximately 2396 research articles were initially selected, of which 215 were identified as potentially relevant for abstract review. Upon further scrutiny, 62 of the 215 studies were reviews, seminars, or presentations, and 44 were original study articles and were thus included in the systematic review. The predominant gene involved in lipid metabolism in cancer was stearoyl-coenzyme A desaturase 1 (SCD1), followed by fatty acid synthase (FASN). The pathway most commonly involved in lipid metabolism in cancer was the phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) signaling pathway, followed by the mitogen activated protein kinase (MAPK) pathway. SCD1 and FASN play significant roles in the initiation and progression of cancer and represent attractive targets for potentially effective anti-cancer treatment strategies. The regulation of cancer metabolism by the Akt kinases will be an interesting topic of future study.

Mechanisms of stearoyl CoA desaturase inhibitor sensitivity and acquired resistance in cancer

The lipogenic enzyme stearoyl CoA desaturase (SCD) plays a key role in tumor lipid metabolism and membrane architecture. SCD is often up-regulated and a therapeutic target in cancer. Here, we report the unexpected finding that median expression of SCD is low in glioblastoma relative to normal brain due to hypermethylation and unintentional monoallelic co-deletion with phosphatase and tensin homolog (PTEN) in a subset of patients. Cell lines from this subset expressed undetectable SCD, yet retained residual SCD enzymatic activity. Unexpectedly, these lines evolved to survive independent of SCD through unknown mechanisms. Cell lines that escaped such genetic and epigenetic alterations expressed higher levels of SCD and were highly dependent on SCD for survival. Last, we identify that SCD-dependent lines acquire resistance through a previously unknown FBJ murine osteosarcoma viral oncogene homolog B (FOSB)-mediated mechanism. Accordingly, FOSB inhibition blunted acquired resistance and extended survival of tumor-bearing mice treated with SCD inhibitor.

Revisiting prostate cancer metabolism: From metabolites to disease and therapy

Prostate cancer (PCa), one of the most commonly diagnosed cancers worldwide, still presents important unmet clinical needs concerning treatment. In the last years, the metabolic reprogramming and the specificities of tumor cells emerged as an exciting field for cancer therapy. The unique features of PCa cells metabolism, and the activation of specific metabolic pathways, propelled the use of metabolic inhibitors for treatment. The present work revises the knowledge of PCa metabolism and the metabolic alterations that underlie the development and progression of the disease. A focus is given to the role of bioenergetic sources, namely, glucose, lipids, and glutamine sustaining PCa cell survival and growth. Moreover, it is described as the action of oncogenes/tumor suppressors and sex steroid hormones in the metabolic reprogramming of PCa. Finally, the status of PCa treatment based on the inhibition of metabolic pathways is presented. Globally, this review updates the landscape of PCa metabolism, highlighting the critical metabolic alterations that could have a clinical and therapeutic interest.

Expression of SCD and FADS2 Is Lower in the Necrotic Core and Growing Tumor Area than in the Peritumoral Area of Glioblastoma Multiforme

The expression of desaturases is higher in many types of cancer, and despite their recognized role in oncogenesis, there has been no research on the expression of desaturases in glioblastoma multiforme (GBM). Tumor tissue samples were collected during surgery from 28 patients (16 men and 12 women) diagnosed with GBM. The effect of necrotic conditions and nutritional deficiency (mimicking conditions in the studied tumor zones) was studied in an in vitro culture of human brain (glioblastoma astrocytoma) U-87 MG cells. Analysis of desaturase expression was made by qRT-PCR and the immunohistochemistry method. In the tumor, the expression of stearoyl–coenzyme A desaturase (SCD) and fatty acid desaturases 2 (FADS2) was lower than in the peritumoral area. The expression of other desaturases did not differ in between the distinguished zones. We found no differences in the expression of SCD, fatty acid desaturases 1 (FADS1), or FADS2 between the sexes. Necrotic conditions and nutritional deficiency increased the expression of the studied desaturase in human brain (glioblastoma astrocytoma) U-87 MG cells. The obtained results suggest that (i) biosynthesis of monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) in a GBM tumor is less intense than in the peritumoral area; (ii) expressions of SCD, SCD5, FADS1, and FADS2 correlate with each other in the necrotic core, growing tumor area, and peritumoral area; (iii) expressions of desaturases in a GBM tumor do not differ between the sexes; and (iv) nutritional deficiency increases the biosynthesis of MUFA and PUFA in GBM cells.

Role of Oleic Acid in the Gut-Liver Axis: From Diet to the Regulation of Its Synthesis via Stearoyl-CoA Desaturase 1 (SCD1)

The consumption of an olive oil rich diet has been associated with the diminished incidence of cardiovascular disease and cancer. Several studies have attributed these beneficial effects to oleic acid (C18 n-9), the predominant fatty acid principal component of olive oil. Oleic acid is not an essential fatty acid since it can be endogenously synthesized in humans. Stearoyl-CoA desaturase 1 (SCD1) is the enzyme responsible for oleic acid production and, more generally, for the synthesis of monounsaturated fatty acids (MUFA). The saturated to monounsaturated fatty acid ratio affects the regulation of cell growth and differentiation, and alteration in this ratio has been implicated in a variety of diseases, such as liver dysfunction and intestinal inflammation. In this review, we discuss our current understanding of the impact of gene-nutrient interactions in liver and gut diseases, by taking advantage of the role of SCD1 and its product oleic acid in the modulation of different hepatic and intestinal metabolic pathways.

Polymorphisms in the 3'-UTR of SCD5 gene are associated with hepatocellular carcinoma in Korean population

The purpose of the study was to assess the relationship between polymorphisms of the SCD5 and MMP1 gene and hepatocellular carcinoma (HCC). The gene polymorphisms with a minor allele frequency (MAF) > 0.05 were selected eight SNPs (rs6840, rs1065403, rs3821974, and rs3733230 in 3'-UTR; rs4693472, rs3733227, rs1848067, and rs6535374 in intron region) of SCD5 gene and two SNPs (rs1799750 and rs1144393 in promoter region) of MMP1 gene. The genotype of SCD5 and MMP1 gene SNPs were determined by direct sequencing and pyrosequencing, respectively. One hundred sixty-two patients with HCC and two hundred twenty-five control subjects were recruited in Korean male population. In terms of genotype frequencies, SCD5 genotype TC, GA, AG, and CG of rs6840, rs1065403, rs3821974, and rs3733230, respectively were higher in control group than HCC. In addition, these genotype decreased the risk (rs6840; OR 0.55, 95% CI 0.31-0.99; rs1065403; OR 0.46, 95% CI 0.26-0.83; rs3821974; OR 0.56, 95% CI 0.31-0.99; rs3733230; OR 0.62, 95% CI 0.34-1.12) of HCC, which may work as a prevention of HCC. At least one minor allele carrier of SCD5 gene polymorphisms were related to decreased risk of HCC for AFP cut-point levels > 200 or > 400 ng/ml, respectively. Our results indicate that polymorphisms in the 3'-UTR of the SCD5 gene may associated with HCC in the Korean male population.

Stearoyl coenzyme A desaturase

Background:

Oral cancer is a major public health problem in many parts of South Asia and ranking third among the cancer types in India. Numerous diagnostic, prognostic and metastatic biomarkers have been employed till date to assess various carcinomas. Stearoyl coenzyme A desaturase (SCD) is one such recently introduced biomarker that regulates key cell cycle events in normal cells and during carcinogenesis in neoplastic cells. Although SCD has been used to analyze the prognosis of breast and renal cell carcinomas, its role in oral epithelial dysplasia (OED) and oral squamous cell carcinoma (OSCC) remains unexplored. Therefore, there is a need to analyze the role of SCD in OED and OSCC to predict their biologic behaviour.

Objectives:

To assess the expression levels of SCD in OED and OSCC samples and correlate them with normal oral mucosa (NOM) to determine their prognostic potential.

Methodology:

Fifty five tissue samples of OED (20), OSCC (20) and NOM (15) was subjected to immunohistochemistry using SCD. Clinical details and follow-up data (3 years) were recorded. Clinical and histopathological parameters were statistically analyzed using descriptive statistics, univariate and multivariate analyses, Kruskal–Wallis analysis of variance test and Mann–Whitney U tests.

Results:

Descriptive analysis on OED and NOM showed a statistically significant difference in age between OED and NOM ( p = 0.002). Univariate analysis of OSCC cases by log-rank test revealed significant results in the usage of smoked and smokeless tobacco and clinical staging of OSCC ( p = 0.044). Significantly increased SCD expression was identified with poor survival rate ( p = 0.028). However, multivariate analysis of OSCC was statistically insignificant ( p = 1.00). A significantly increased SCD expression was observed in OED and OSCC when compared to NOM ( p = 0.001). The expression of SCD was significantly high in OSCC when compared to OED ( p = 0.029). Although an increased expression of SCD was appreciated in higher grades of OED and poorly differentiated squamous cell carcinoma, a statistical significance was not achieved ( p = 0.546 and 0.388, respectively).

Conclusion:

The expression of SCD in OED was higher than NOM suggesting changes in cell cycle control in OED. An enhanced expression of SCD was identified in OSCC when compared to OED. Correlating the SCD expression with survival rate in OSCC patients revealed an increased SCD expression with diminished survival rate, indicating that SCD may be used to predict prognosis. However, the role of SCD in assessing the prognostic potential within the grades of OED and OSCC requires future research.

Aberrant lipid metabolism in cancer cells - the role of oncolipid-activated signaling

Metabolic activity of malignant cells is very different from that of their nontransformed equivalents, which establishes metabolic reprogramming as an important hallmark of every transformed cell. In particular, the current arena of research in this field aims to understand the regulatory effect of oncogenic signaling on metabolic rewiring in transformed cells in order to exploit this for therapeutic benefit. Alterations in lipid metabolism are one of the main aspects of metabolic rewiring of transformed cells. Up-regulation of several lipogenic enzymes has been reported to be a characteristic of various cancer types. Lysophosphatidic acid (LPA), a simple byproduct of the lipid biosynthesis pathway, has gained immense importance due to its elevated level in several cancers and associated growth-promoting activity. Importantly, a current study revealed its role in increased de novo lipid synthesis through up-regulation of sterol regulatory element-binding protein 1, a master regulator of lipid metabolism. This review summarizes the recent insights in the field of oncolipid LPA-mediated signaling in regard to lipid metabolism in cancers. Future work in this domain is required to understand the up-regulation of the de novo synthesis pathway and the role of its end products in malignant cells. This will open a new arena of research toward the development of specific metabolic inhibitors that can add to the pre-existing chemotherapeutics in order to increase the efficacy of clinical output in cancer patients.

Integration of tissue metabolomics, transcriptomics and immunohistochemistry reveals ERG- and gleason score-specific metabolomic alterations in prostate cancer

Integrated analysis of metabolomics, transcriptomics and immunohistochemistry can contribute to a deeper understanding of biological processes altered in cancer and possibly enable improved diagnostic or prognostic tests. In this study, a set of 254 metabolites was determined by gas-chromatography/liquid chromatography-mass spectrometry in matched malignant and non-malignant prostatectomy samples of 106 prostate cancer (PCa) patients. Transcription analysis of matched samples was performed on a set of 15 PCa patients using Affymetrix U133 Plus 2.0 arrays. Expression of several proteins was immunohistochemically determined in 41 matched patient samples and the association with clinico-pathological parameters was analyzed by an integrated data analysis. These results further outline the highly deregulated metabolism of fatty acids, sphingolipids and polyamines in PCa. For the first time, the impact of the ERG translocation on the metabolome was demonstrated, highlighting an altered fatty acid oxidation in TMPRSS2-ERG translocation positive PCa specimens. Furthermore, alterations in cholesterol metabolism were found preferentially in high grade tumors, enabling the cells to create energy storage. With this integrated analysis we could not only confirm several findings from previous metabolomic studies, but also contradict others and finally expand our concepts of deregulated biological pathways in PCa.

Stearoyl-CoA desaturase 1 and paracrine diffusible signals have a major role in the promotion of breast cancer cell migration induced by cancer-associated fibroblasts

Background:

Despite the recognised contribution of the stroma to breast cancer development and progression, the effective targeting of the tumor microenvironment remains a challenge to be addressed. We previously reported that normal fibroblasts (NFs) and, notably, breast cancer-associated fibroblasts (CAFs) induced epithelial-to-mesenchymal transition and increases in cell membrane fluidity and migration in well- (MCF-7) and poorly-differentiated (MDA-MB-231) breast cancer cells. This study was designed to better define the role played, especially by CAFs, in promoting breast tumor cell migration.

Methods:

Fibroblast/breast cancer cell co-cultures were set up to investigate the influence of NFs and CAFs on gene and protein expression of Stearoyl-CoA desaturase 1 (SCD1), the main enzyme regulating membrane fluidity, as well as on the protein level and activity of its transcription factor, the sterol regulatory element-binding protein 1 (SREBP1), in MCF-7 and MDA-MB-231 cells. To assess the role of SREBP1 in the regulation of SCD1 expression, the desaturase levels were also determined in tumor cells treated with an SREBP1 inhibitor. Migration was evaluated by wound-healing assay in SCD1-inhibited (by small-interfering RNA (siRNA) or pharmacologically) cancer cells and the effect of CAF-conditioned medium was also assessed. To define the role of stroma-derived signals in cancer cell migration speed, cell-tracking analysis was performed in the presence of neutralising antibodies to hepatocyte growth factor, transforming growth factor-β or basic fibroblast growth factor.

Results:

A two to three fold increase in SCD1 mRNA and protein expression has been induced, particularly by CAFs, in the two cancer cell lines that appear to be dependent on SREBP1 activity in MCF-7 but not in MDA-MB-231 cells. Both siRNA-mediated and pharmacological inhibition of SCD1 impaired tumor cells migration, also when promoted by CAF-released soluble factors. Fibroblast-triggered increase in cancer cell migration speed was markedly reduced or abolished by neutralising the above growth factors.

Conclusion:

These results provide further insights in understanding the role of CAFs in promoting tumor cell migration, which may help to design new stroma-based therapeutic strategies.

MRS measured fatty acid composition of periprostatic adipose tissue correlates with pathological measures of prostate cancer aggressiveness

PURPOSE

To investigate the association between magnetic resonance (MR) spectroscopically measured fatty acid composition of periprostatic adipose tissue and pathological markers of prostate cancer aggressiveness.

MATERIALS AND METHODS

Periprostatic adipose (PPA) and subcutaneous adipose (SQA) tissue from prostate cancer patients undergoing radical prostatectomy were examined ex vivo by proton MR spectroscopy at 14.1T (n = 31). Fractions of monounsaturated, polyunsaturated, total unsaturated, and saturated fatty acids, as well as T2 relaxation times were measured from the spectra. Univariate and multivariate analyses based on receiver operating characteristic (ROC) and support vector machines (SVM) were used to evaluate the association between differential measures of fatty acid levels in the PPA and SQA tissues and Gleason score and extracapsular extension (ECE), which are pathological measures of prostate cancer aggressiveness.

RESULTS

Both pathological markers for aggressive prostate cancer have separable patterns in the MRS features space. The association between ECE and PPA tissue fatty acid composition is linear (area under receiver operating characteristic curve (AROC) and 95% confidence intervals [CIs]: 1.00, [1.00, 1.00]), along the Δ(fM /fS ) measure, and is marked by elevated monounsaturated and reduced saturated fatty acids in the PPA tissue relative to SQA. In contrast, the association between Gleason score and PPA tissue fatty acid composition is nonlinear (classifier AROC and 95% CIs: 0.86, [0.71, 1.00]).

CONCLUSION

Fatty acid composition is altered in the PPA tissue of patients with aggressive prostate cancer. Ex vivo MR spectroscopy may be a useful tool in studying the altered fatty acid metabolism in prostate cancer.

NMR-based evaluation of the metabolic profile and response to dichloroacetate of human prostate cancer cells

The aim of this study was to evaluate the metabolic profile of human prostate cancer cells that have different metastatic potential and to determine their response to dichloroacetate (DCA) using NMR technology. Two isogenic human prostate cancer cell lines, differing in their metastatic potential [LNCaP (poorly metastatic) and LNCaP-LN3 (highly metastatic)], were studied. Metabolite ratios from NMR spectral integrals acquired at a field strength of 9.4 T using a 5-mm broadband probe with an NMR-compatible bioreactor were compared in the presence and absence of the pyruvate dehydrogenase kinase inhibitor DCA. Lactate dehydrogenase (LDH) isoenzymes were assessed by zymography. Following the treatment of cells with 50 mm DCA, there was a significant reduction in the lactate/choline, lactate/creatine, lactate/alanine and the combined lactate/(choline + creatine + alanine) ratios in LNCaP-LN3 cells relative to LNCaP cells. No significant changes in metabolite ratios were found in LNCaP cells following DCA treatment. As expected, LDH zymography assays showed an absence of the LDH-B subunit in LNCaP-LN3 cells, whereas both LDH-A and LDH-B subunits were present in LNCaP cells. DCA was shown to significantly modify the metabolite ratios in highly metastatic LNCaP-LN3 cells, but not in poorly metastatic LNCaP cells. This effect was probably related to the absence of the LDH-B subunit in LNCaP-LN3 cells, and could have a bearing on cancer treatment with DCA and related compounds.

Isolation and characterization of the anticancer gene organic cation transporter like-3 (ORCTL3)

ORCTL3, an organic cation/anion transporter expressed in various tissue types, was isolated in a genome-wide cDNA screen as a gene with a tumor-specific apoptosis activity. When overexpressed it elicits an apoptosis response in many transformed cells, while normal cells remain unaffected. It can be activated for apoptosis induction by individual tumorigenic mutations in renal cells. This effect is independent of the tumor cells' proliferation status and mediated by an incomplete ER stress response, characterized by the accumulation of the endoplasmic reticulum-stress marker ATF4, but not BiP. Recent studies show that for its apoptosis induction activity ORCTL3 targets the enzyme stearoyl-CoA desaturase-1 (SCD-1) that is involved in the fatty acid metabolism. This is evidenced by the inhibition of apoptosis induced through ORCTL3 when the SCD-1 product oleic acid is exogenously supplemented or when SCD-1 is co-transfected in the transformed cells. ORCTL3's activity to specifically target tumor cells is caused by the transmembrane domains 3 and 4 of the mouse, but not the human, gene. In an in vivo model ORCTL3 shows a significant shrinkage in the size of xenograft tumors when injected with an adenoviral carrier carrying the mouse ORCTL3 gene. An ex vivo study using human renal cancer cells confirmed the promising tumor-specific apoptosis effect of ORCTL3. Since ORCTL3 targets fatty acid metabolism in transformed cells and induces an ER stress specifically in these cells, it reveals a novel therapeutic interference option for tumor cells.

Human breast cancer tissues contain abundant phosphatidylcholine(36∶1) with high stearoyl-CoA desaturase-1 expression

Breast cancer is the leading cause of cancer and mortality in women worldwide. Recent studies have argued that there is a close relationship between lipid synthesis and cancer progression because some enzymes related to lipid synthesis are overexpressed in breast cancer tissues. However, lipid distribution in breast cancer tissues has not been investigated. We aimed to visualize phosphatidylcholines (PCs) and lysoPCs (LPCs) in human breast cancer tissues by performing matrix assisted laser desorption/ionization-imaging mass spectrometry (MALDI-IMS), which is a novel technique that enables the visualization of molecules comprehensively. Twenty-nine breast tissue samples were obtained during surgery and subjected to MALDI-IMS analysis. We evaluated the heterogeneity of the distribution of PCs and LPCs on the tissues. Three species [PC(32∶1), PC(34∶1), and PC(36∶1)] of PCs with 1 mono-unsaturated fatty acid chain and 1 saturated fatty acid chain (MUFA-PCs) and one [PC(34∶0)] of PCs with 2 saturated fatty acid chains (SFA-PC) were relatively localized in cancerous areas rather than the rest of the sections (named reference area). In addition, the LPCs did not show any biased distribution. The relative amounts of PC(36∶1) compared to PC(36∶0) and that of PC(36∶1) to LPC(18∶0) were significantly higher in the cancerous areas. The protein expression of stearoyl-CoA desaturase-1 (SCD1), which is a synthetic enzyme of MUFA, showed accumulation in the cancerous areas as observed by the results of immunohistochemical staining. The ratios were further analyzed considering the differences in expressions of the estrogen receptor (ER), human epidermal growth factor receptor 2 (HER2), and Ki67. The ratios of the signal intensity of PC(36∶1) to that of PC(36∶0) was higher in the lesions with positive ER expression. The contribution of SCD1 and other enzymes to the formation of the observed phospholipid composition is discussed.

Quantitative proteomics reveals that enzymes of the ketogenic pathway are associated with prostate cancer progression

Prostate cancer is the most common malignancy and the second leading cause of cancer-related deaths in men. One common treatment is androgen-deprivation therapy, which reduces symptoms in most patients. However, over time, patients develop tumors that are androgen-independent and ultimately fatal. The mechanisms that cause this transition remain largely unknown, and as a result, there are no effective treatments against androgen-independent prostate cancer. As a model platform, we used the LNCaP cell line and its androgen-independent derivative, LNCaP-SF. Utilizing stable isotope labeling with amino acids in cell culture coupled to mass spectrometry, we assessed the differential global protein expression of the two cell lines. Our proteomic analysis resulted in the quantification of 3355 proteins. Bioinformatic prioritization resulted in 42 up-regulated and 46 down-regulated proteins in LNCaP-SF cells relative to LNCaP cells. Our top candidate, HMGCS2, an enzyme involved in ketogenesis, was found to be 9-fold elevated in LNCaP-SF cells, based on peptide ratios. After analyzing the remaining enzymes of this pathway (ACAT1, BDH1, HMGCL, and OXCT1), we observed increased expression of these proteins in the LNCaP-SF cells, which was further verified using Western blotting. To determine whether these enzymes were up-regulated in clinical samples, we performed quantitative PCR and immunohistochemistry on human prostate cancer tissues, from which we observed significantly increased transcript and protein levels in high-grade cancer (Gleason grade ≥ 8). In addition, we observed significant elevation of these enzymes in the LuCaP 96AI castration-resistant xenograft. Further assessment of ACAT1 on human castration-resistant metastatic prostate cancer tissues revealed substantially elevated expression of ACAT1 in these specimens. Taken together, our results indicate that enzymes of the ketogenic pathway are up-regulated in high-grade prostate cancer and could serve as potential tissue biomarkers for the diagnosis or prognosis of high-grade disease.

PPARγ isoforms differentially regulate metabolic networks to mediate mouse prostatic epithelial differentiation

Recent observations indicate prostatic diseases are comorbidities of systemic metabolic dysfunction. These discoveries revealed fundamental questions regarding the nature of prostate metabolism. We previously showed that prostate-specific ablation of PPARγ in mice resulted in tumorigenesis and active autophagy. Here, we demonstrate control of overlapping and distinct aspects of prostate epithelial metabolism by ectopic expression of individual PPARγ isoforms in PPARγ knockout prostate epithelial cells. Expression and activation of either PPARγ 1 or 2 reduced de novo lipogenesis and oxidative stress and mediated a switch from glucose to fatty acid oxidation through regulation of genes including Pdk4, Fabp4, Lpl, Acot1 and Cd36. Differential effects of PPARγ isoforms included decreased basal cell differentiation, Scd1 expression and triglyceride fatty acid desaturation and increased tumorigenicity by PPARγ1. In contrast, PPARγ2 expression significantly increased basal cell differentiation, Scd1 expression and AR expression and responsiveness. Finally, in confirmation of in vitro data, a PPARγ agonist versus high-fat diet (HFD) regimen in vivo confirmed that PPARγ agonization increased prostatic differentiation markers, whereas HFD downregulated PPARγ-regulated genes and decreased prostate differentiation. These data provide a rationale for pursuing a fundamental metabolic understanding of changes to glucose and fatty acid metabolism in benign and malignant prostatic diseases associated with systemic metabolic stress.

The role of stearoyl-CoA desaturase in obesity, insulin resistance, and inflammation

Stearoyl-CoA desaturase 1 (SCD1) is an essential lipogenic enzyme that has been shown to play an intrinsic role in the development of obesity and related conditions, such as insulin resistance. Through the generation of various mouse models of SCD1 deficiency, we have come to understand that SCD1 plays a role, directly or indirectly, in diverse metabolic processes, including lipogenesis, fatty acid oxidation, insulin signaling, thermogenesis, and inflammation. This review will address recent advances in our understanding of this key regulator of cellular metabolic processes, including the role of SCD1 in maintaining skin barrier integrity and the role of skin SCD1 in the metabolic phenotype elicited by global SCD1 deficiency.

Roles of StearoylCoA Desaturase-1 in the Regulation of Cancer Cell Growth, Survival and Tumorigenesis

The development and maintenance of defining features of cancer, such as unremitting cell proliferation, evasion of programmed cell death, and the capacity for colonizing local tissues and distant organs, demand a massive production of structural, signaling and energy-storing lipid biomolecules of appropriate fatty acid composition. Due to constitutive activation of fatty acid biosynthesis, cancer cell lipids are enriched with saturated (SFA) and, in particular, monounsaturated fatty acids (MUFA), which are generated by StearoylCoA desaturase-1, the main enzyme that transforms SFA into MUFA. An increasing number of experimental and epidemiological studies suggest that high levels of SCD1 activity is a major factor in establishing the biochemical and metabolic perturbations that favors the oncogenic process. This review examines evidence that suggests the critical implication of SCD1 in the modulation of multiple biological mechanisms, specifically lipid biosynthesis and proliferation and survival signaling pathways that contribute to the development and progression of cancer.

Stearoyl CoA desaturase 1: role in cellular inflammation and stress

Stearoyl CoA desaturase 1 (SCD1) catalyzes the rate-limiting step in the production of MUFA that are major components of tissue lipids. Alteration in SCD1 expression changes the fatty acid profile of these lipids and produces diverse effects on cellular function. High SCD1 expression is correlated with metabolic diseases such as obesity and insulin resistance, whereas low levels are protective against these metabolic disturbances. However, SCD1 is also involved in the regulation of inflammation and stress in distinct cell types, including β-cells, adipocytes, macrophages, endothelial cells, and myocytes. Furthermore, complete loss of SCD1 expression has been implicated in liver dysfunction and several inflammatory diseases such as dermatitis, atherosclerosis, and intestinal colitis. Thus, normal cellular function requires the expression of SCD1 to be tightly controlled. This review summarizes the current understanding of the role of SCD1 in modulating inflammation and stress.

Inhibition of stearoyl-CoA desaturase 1 expression induces CHOP-dependent cell death in human cancer cells

BACKGROUND

Cancer cells present a sustained de novo fatty acid synthesis with an increase of saturated and monounsaturated fatty acid (MUFA) production. This change in fatty acid metabolism is associated with overexpression of stearoyl-CoA desaturase 1 (Scd1), which catalyses the transformation of saturated fatty acids into monounsaturated fatty acids (e.g., oleic acid). Several reports demonstrated that inhibition of Scd1 led to the blocking of proliferation and induction of apoptosis in cancer cells. Nevertheless, mechanisms of cell death activation remain to be better understood.

PRINCIPAL FINDINGS

In this study, we demonstrated that Scd1 extinction by siRNA triggered abolition of de novo MUFA synthesis in cancer and non-cancer cells. Scd1 inhibition-activated cell death was only observed in cancer cells with induction of caspase 3 activity and PARP-cleavage. Exogenous supplementation with oleic acid did not reverse the Scd1 ablation-mediated cell death. In addition, Scd1 depletion induced unfolded protein response (UPR) hallmarks such as Xbp1 mRNA splicing, phosphorylation of eIF2α and increase of CHOP expression. However, the chaperone GRP78 expression, another UPR hallmark, was not affected by Scd1 knockdown in these cancer cells indicating a peculiar UPR activation. Finally, we showed that CHOP induction participated to cell death activation by Scd1 extinction. Indeed, overexpression of dominant negative CHOP construct and extinction of CHOP partially restored viability in Scd1-depleted cancer cells.

CONCLUSION

These results suggest that inhibition of de novo MUFA synthesis by Scd1 extinction could be a promising anti-cancer target by inducing cell death through UPR and CHOP activation.

Erythrocyte fatty acids and prostate cancer risk: a comparison of methods

The role of fatty acids (FA) in prostate carcinogenesis is unclear. Interest in the inter-relationship among different types of FA has resulted in new analytic approaches to FA and their role in cancer development. We evaluated the association between erythrocyte FA and prostate cancer in 127 prostate cancer patients and 183 screen negative controls. We present three approaches to the analyses of the FA and prostate cancer association; (1) individual or common groups of FA, (2) biologically meaningful FA ratios and (3) principal components analysis. Monounsaturated FA and the alpha-linolenic:eicosapentaenoic ratio were associated with reduced risk of prostate cancer. However, Factor 1, which was strongly correlated with some long chain saturated FA, was associated with an increased risk of prostate cancer. We provide an example of modeling FA and their inter-relationships on the risk of prostate cancer. Comparing three approaches suggests the importance of considering the impact of the entire fatty acid profile in disease prevention.

Stearoyl-CoA desaturase-1: a novel key player in the mechanisms of cell proliferation, programmed cell death and transformation to cancer

As part of a shift toward macromolecule production to support continuous cell proliferation, cancer cells coordinate the activation of lipid biosynthesis and the signaling networks that stimulate this process. A ubiquitous metabolic event in cancer is the constitutive activation of the fatty acid biosynthetic pathway, which produces saturated fatty acids (SFAs) and monounsaturated fatty acids (MUFAs) to sustain the increasing demand of new membrane phospholipids with appropriate acyl composition. In cancer cells, the tandem activation of the fatty acid biosynthetic enzymes adenosine triphosphate citrate lyase, acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) leads to increased synthesis of SFA and their further conversion into MUFA by stearoyl-CoA desaturase (SCD) 1. The roles of adenosine triphosphate citrate lyase, ACC and FAS in the pathogenesis of cancer have been a subject of extensive investigation. However, despite early experimental and epidemiological observations reporting elevated levels of MUFA in cancer cells and tissues, the involvement of SCD1 in the mechanisms of carcinogenesis remains surprisingly understudied. Over the past few years, a more detailed picture of the functional relevance of SCD1 in cell proliferation, survival and transformation to cancer has begun to emerge. The present review addresses the mounting evidence that argues for a key role of SCD1 in the coordination of the intertwined pathways of lipid biosynthesis, energy sensing and the transduction signals that influence mitogenesis and tumorigenesis, as well as the potential value of this enzyme as a target for novel pharmacological approaches in cancer interventions.

Fatty acid desaturase expression in human leucocytes correlates with plasma phospholipid fatty acid status

Associations between and changes in plasma phospholipid fatty acid (FA) concentrations and expression of delta 5 desaturase (D5D), delta 6 desaturase (D6D) and delta 9 desaturase (D9D) in leucocytes were investigated both before and during n-3 FA supplementation for 2 weeks in 20 healthy individuals. Participants were divided into two groups depending on fish intake: one fish meal or less per week and no marine FA supplement (Lowfish, n = 9) and more than one fish meal per week and/or daily oral marine FA supplement (Highfish, n = 11). Before starting supplementation (t = 0), concentrations of n-3 FAs were significantly lower in the Lowfish group compared to the Highfish group. During supplementation in both groups, n-3 FAs increased, whereas n-6 FAs decreased. D5D expression was significantly higher in Lowfish compared to Highfish at t = 0. No difference in D6D or D9D expression was observed. D5D expression was inversely correlated with EPA, DPA, DHA and total n-3 FA, and positively correlated with the ratio total n-6 FA/total n-3 FA at t = 0. Expression of D5D in the Lowfish group as well as D6D in both groups significantly decreased relative to the expression at t = 0 during the first day of supplement. PUFA concentration was generally predicted by its precursor FA and D5D or D6D expression. The correlations mentioned disappeared after 2 weeks of supplementation. This indicates that steady-state FA desaturase expression is associated with plasma phospholipid FA composition. Whether leucocyte desaturase expression may have potential as a marker of PUFA status merits further investigation.

Regulation of desaturase expression in HL60 cells

The expression of delta 5 desaturase (D5D), delta 6 desaturase (D6D) and delta 9 desaturase (D9D) was determined by RT-PCR in the human promyelocytic cell line HL60. During 72 h of culture with 10% FBS, D5D and D6D were upregulated 5 to 6-fold, whereas D9D approximately doubled. The addition of fatty acids (FAs) to the culture medium suppressed upregulation of all desaturases. N-3 and n-6 FA appeared to be more effective than n-9 or saturated FA. When FAs were added after 72 h, further upregulation during the next 24 h was suppressed for nearly all desaturases and FAs tested, except for D5D when oleic acid (OA) or stearic acid (SA) was added. In cells cultured with restricted amounts of FBS, desaturase expression increased with decreasing concentrations of FBS. Cellular FA content decreased by 60% in the neutral lipid fraction, whereas that of the phospholipid fraction decreased by 10% during 72 h of culture. The largest decrease occurred in the sum of n-3 and n-6 FA of the neutral lipid fraction, which was reduced by 83%, whereas the content of these FAs in the phospholipid fraction decreased by 32%. The results indicate that when the supply of FA to HL60 cells is limited, the intracellular content of n-3 and n-6 FA decreases and this leads to upregulation of the desaturases, particularly D5D and D6D. Since HL60 cells resemble human leukocytes, the results suggest that desaturase expression in leukocytes may be exploited as a biomarker for FA status.

Chemical speciation by selective heteronuclear single-quantum coherence spectroscopy: determination of double-bond quantity in unsaturated fatty acid compounds

A method for identifying fatty acid species based on the number of double bonds contained in a lipid molecule is presented. Common to all polyunsaturated fatty acids are two signature resonances at approximately 5.3 and 2.8 ppm in the proton chemical-shift spectrum of NMR. These resonances are from the vinyl and bis-allyl protons, respectively, and, although they can be readily observed by NMR from lipid extracts of biological samples, direct speciation has never been demonstrated by NMR. By modifying a conventional HSQC pulse sequence with a J-pulse on the spin system of the vinyl group (generalized as an IS spin system) at the beginning of the initial polarization transfer period and selectively inverting the 13C (I) spins with a narrowband sech/tanh inversion pulse, the collection of data in both dimensions can be restricted to a narrow slice of the chemical-shift range. The resolution is subsequently determined by digitizer efficiency, and spectra can be collected optimally from within a very narrow 1 x 6 ppm window of the respective proton and carbon chemical-shift ranges. With this modification it is possible to distinguish at least one resonance each from the multiple shifts expected from the indirectly detected nuclei of the fatty acid species, oleic acid, linoleic acid, linolenic acid and arachidonic acid, which contain one, two, three and four double bonds, respectively. This and similar methods of applied selectivity are of potential interest in characterizing speciation in biological samples where mixtures are often encountered and chemical shifts of the same structural group of similar molecules give rise to complicated overlapping resonances but are important for diagnosis of disease processes such as cancer.

Low-fat, low-glycemic load diet and gene expression in human prostate epithelium: a feasibility study of using cDNA microarrays to assess the response to dietary intervention in target tissues

PURPOSE

We examined the feasibility of using gene expression changes in human prostate epithelium as a measure of response to a dietary intervention.

MATERIALS AND METHODS

Eight men with newly diagnosed prostate cancer were randomized to a low-fat/low-glycemic load intervention arm (<20% energy from fat and total daily glycemic load <100) or a "standard American" control arm (approximately 35% energy from fat and total daily glycemic load >200). Prostate tissue was collected before randomization and approximately 6 weeks later, at the time of radical prostatectomy. Epithelium was acquired by laser capture microdissection, and transcript abundance levels were measured by cDNA microarray hybridization and confirmed by quantitative reverse transcription-PCR.

RESULTS

Men in the intervention arm consumed 39% less total energy (P = 0.004) and the difference in weight change between intervention and control arms was -6.1 kg (P = 0.02). In the intervention arm, 23 (0.46%) of 5,711 cDNAs with measurable expression were significantly altered (P < 0.05; false discovery rate, <or=10%). In the control arm, there were no significant changes in transcript expression, even when using a false discovery rate as high as 50%.

CONCLUSIONS

A 6-week, low-fat/low-glycemic load diet was associated with significant gene expression changes in human prostate epithelium. These results show the feasibility of using prostate tissues collected at diagnosis and at surgery to study the effects of dietary manipulation on prostate tissue, which may give insight into the molecular mechanisms underlying the associations of diet and obesity with the development or progression of prostate cancer.

Integrative molecular concept modeling of prostate cancer progression

Despite efforts to profile prostate cancer, the genetic alterations and biological processes that correlate with the observed histological progression are unclear. Using laser-capture microdissection to isolate 101 cell populations, we have profiled prostate cancer progression from benign epithelium to metastatic disease. By analyzing expression signatures in the context of over 14,000 'molecular concepts', or sets of biologically connected genes, we generated an integrative model of progression. Molecular concepts that demarcate critical transitions in progression include protein biosynthesis, E26 transformation-specific (ETS) family transcriptional targets, androgen signaling and cell proliferation. Of note, relative to low-grade prostate cancer (Gleason pattern 3), high-grade cancer (Gleason pattern 4) shows an attenuated androgen signaling signature, similar to metastatic prostate cancer, which may reflect dedifferentiation and explain the clinical association of grade with prognosis. Taken together, these data show that analyzing gene expression signatures in the context of a compendium of molecular concepts is useful in understanding cancer biology.

Time- and concentration-dependent changes in gene expression induced by benzo(a)pyrene in two human cell lines, MCF-7 and HepG2

BACKGROUND

The multi-step process of carcinogenesis can be more fully understood by characterizing gene expression changes induced in cells by carcinogens. In this study, expression microarrays were used to monitor the activity of 18,224 cDNA clones in MCF-7 and HepG2 cells exposed to the carcinogen benzo(a)pyrene (BaP) or its non-carcinogenic isomer benzo(e)pyrene (BeP). Time and concentration gene expression effects of BaP exposure have been assessed and linked to other measures of cellular stress to aid in the identification of novel genes/pathways involved in the cellular response to genotoxic carcinogens.

RESULTS

BaP (0.25-5.0 muM; 6-48 h exposure) modulated 202 clones in MCF-7 cells and 127 in HepG2 cells, including 27 that were altered in both. In contrast, BeP did not induce consistent gene expression changes at the same concentrations. Significant time- and concentration-dependent responses to BaP were seen in both cell lines. Expression changes observed in both cell lines included genes involved in xenobiotic metabolism (e.g., CYP1B1, NQO1, MGST1, AKR1C1, AKR1C3,CPM), cell cycle regulation (e.g., CDKN1A), apoptosis/anti-apoptosis (e.g., BAX, IER3), chromatin assembly (e.g., histone genes), and oxidative stress response (e.g., TXNRD1). RTqPCR was used to validate microarray data. Phenotypic anchoring of the expression data to DNA adduct levels detected by 32P-postlabelling, cell cycle data and p53 protein expression identified a number of genes that are linked to these biological outcomes, thereby strengthening the identification of target genes. The overall response to BaP consisted of up-regulation of tumour suppressor genes and down-regulation of oncogenes promoting cell cycle arrest and apoptosis. Anti-apoptotic signalling that may increase cell survival and promote tumourigenesis was also evident.

CONCLUSION

This study has further characterised the gene expression response of human cells after genotoxic insult, induced after exposure to concentrations of BaP that result in minimal cytotoxicity. We have demonstrated that investigating the time and concentration effect of a carcinogen on gene expression related to other biological end-points gives greater insight into cellular responses to such compounds and strengthens the identification of target genes.

Molecular markers in the diagnosis of prostate cancer

The genetic alterations leading to prostate cancer are gradually being discovered. A wide variety of genes have been associated with prostate cancer development as well as tumor progression. Knowledge of gene polymorphisms associated with disease aid in the understanding of important pathways involved in this process and may result in the near future in clinical applications. Urinary molecular markers will soon be available to aid in the decision of repeat prostate biopsies. Recent findings suggest the importance of androgen signaling in disease development and progression. The further understanding of interaction of inflammation, diet, and genetic predisposition will improve risk stratification in the near future.

Influence of surgical manipulation on prostate gene expression: implications for molecular correlates of treatment effects and disease prognosis

PURPOSE

Measurements of tissue gene expression are increasingly used for disease stratification, clinical trial eligibility, and assessment of neoadjuvant therapy response. However, the method of tissue acquisition alone could significantly influence the expression of specific transcripts or proteins. This study examines whether there are transcript alterations associated with surgical resection of the prostate gland by radical retropubic prostatectomy.

MATERIALS AND METHODS

Twelve patients with clinically localized prostate cancer underwent immediate in situ prostate biopsy after induction of anesthesia for radical prostatectomy. Ex vivo prostate biopsies were performed immediately after surgical removal. Prostate epithelium was acquired by laser-capture microdissection, and transcript abundance levels were quantitated by cDNA microarray hybridization and confirmed by quantitative polymerase chain reaction. Data were analyzed by paired, two-sample t test using Statistical Analysis of Microarray algorithms, and linear models were fit as a function of clinical characteristics.

RESULTS

Of 5,753 cDNAs with measurable expression in prostate epithelium, 88 (1.5%) were altered as a result of surgery (false-discovery rate < or = 10%), representing 62 unique genes. These included transcripts encoding acute phase response proteins, IER2 and JUNB, and regulators of cell proliferation, p21Cip1 and KLF6. Of the clinical characteristics examined, including patient age, prostate volume, serum prostate-specific antigen, blood loss, and operative time, only gland volume was significantly and negatively associated with the magnitude of gene expression difference between pre- and postsurgical specimens.

CONCLUSION

Surgical manipulation results in significant gene expression changes. Molecular analyses of surgical samples should recognize that transcript alterations occur rapidly, and these results are important when designing and analyzing molecular correlates of clinical studies.

Increased lipogenesis in cancer cells: new players, novel targets

PURPOSE OF REVIEW

This review evaluates recent findings on the mechanisms by which lipogenic enzymes are upregulated or activated in cancer cells, the implications of increased lipogenesis for cancer cell biology and the feasibility of exploiting this pathway and its regulators as targets for antineoplastic intervention.

RECENT FINDINGS

The list of cancer types showing increased lipogenic enzyme expression keeps growing and further evidence is accumulating that growth factor signaling and particularly activation of the phosphatidylinositol 3'-kinase/protein kinase B pathway plays a role in this process. This signaling pathway stimulates lipogenic gene transcription through activation of the lipogenic transcription factor sterol regulatory element-binding protein-1 and directly activates lipogenic enzymes such as ATP-citrate lyase, linking the upregulation of lipogenesis in cancer cells to the well known tumor-associated increase in glycolysis. Steroid hormones, overexpression of the ubiquitin-specific protease-2a and mutations in breast cancer susceptibility gene 1 may further enhance lipid synthesis. While fatty acid synthase is further established as a target for antineoplastic intervention, recent findings show that interference with acetyl-CoA carboxylase-alpha, ATP citrate lyase or the AMP-activated protein kinase limits cancer cell proliferation and survival.

SUMMARY

The same disturbances in signaling pathways responsible for oncogenic transformation may also contribute to the increased lipogenesis observed in tumor cells. Increased lipogenesis involves modulation of multiple lipogenic enzymes at both transcriptional and posttranscriptional level and is linked to other cancer-associated metabolic changes. Not only fatty acid synthase, but in fact all key enzymes involved in fatty acid synthesis as well as key metabolic regulators are potential targets for antineoplastic intervention.

Cell type-specific analyses for identifying prostate cancer biomarkers

Cancers of the prostate contribute substantial morbidity and mortality to the male population. The correlation of prostate cancer incidence with aging suggests that the disease burden associated with prostate carcinoma will increase dramatically over the next several decades. Despite the large number of fatalities directly linked to prostate cancer, most men harboring the disease will die of other causes. This fact poses substantial dilemmas for screening programs designed to diagnose cancers at an early stage, as the optimal approach also would provide guidance as to which cancers could or should be observed, versus those malignancies that require curative therapy, and whether localized treatments are sufficient or if additional systemic interventions are indicated. To address these issues, substantial resources have been focused on the identification of biomarkers capable of specifically and sensitively diagnosing prostate cancers and providing prognostic information. However, the discovery and use of biomarkers must contend with the complexity and heterogeneity of body fluids and tissues. This review describes approaches that use cell type-specific analysis methods to identify cancer-associated features with the potential of distinguishing individuals with cancer of the prostate.

Fatty acid oxidation is a dominant bioenergetic pathway in prostate cancer

Most malignancies have increased glycolysis for energy requirement of rapid cell proliferation, which is the basis for tumor imaging through glucose analog FDG (2-deoxy-2-fluoro-D-glucose) with positron emission tomography. One of significant characteristics of prostate cancer is slow glycolysis and low FDG avidity. Recent studies showed that prostate cancer is associated with changes of fatty acid metabolism. Several enzymes involved in the metabolism of fatty acids have been determined to be altered in prostate cancer relative to normal prostate, which is indicative of an enhanced beta-oxidation pathway in prostate cancer. Increased fatty acid utilization in prostate cancer provides both ATP and acetyl-coenzyme A (CoA); subsequently, increased availability of acetyl-CoA makes acceleration of citrate oxidation possible, which is an important energy source as well. Dominant fatty acid metabolism rather than glycolysis has the potential to be the basis for imaging diagnosis and targeted treatment of prostate cancer.

Options available for profiling small samples: a review of sample amplification technology when combined with microarray profiling

The possibility of performing microarray analysis on limited material has been demonstrated in a number of publications. In this review we approach the technical aspects of mRNA amplification and several important implicit consequences, for both linear and exponential procedures. Amplification efficiencies clearly allow profiling of extremely small samples. The conservation of transcript abundance is the most important issue regarding the use of sample amplification in combination with microarray analysis, and this aspect has generally been found to be acceptable, although demonstrated to decrease in highly diluted samples. The fact that variability and discrepancies in microarray profiles increase with minute sample sizes has been clearly documented, but for many studies this does appear to have affected the biological conclusions. We suggest that this is due to the data analysis approach applied, and the consequence is the chance of presenting misleading results. We discuss the issue of amplification sensitivity limits in the light of reports on fidelity, published data from reviewed articles and data analysis approaches. These are important considerations to be reflected in the design of future studies and when evaluating biological conclusions from published microarray studies based on extremely low input RNA quantities.

Application of proton NMR spectroscopy in the study of lipid metabolites in a rat hepatocarcinogenesis model

Liver cancer is one of the most common cancers worldwide. Altered lipid metabolism in the liver is a key feature of developing liver nodules and tumors. Methods of analysis vary from the most sophisticated chromatography to the in vivo nuclear magnetic resonance (NMR) spectroscopy. In this study, we present a systematic method for the identification and quantitation of signature signals from lipid metabolites using 1D NMR proton spectroscopy. We assessed lipid metabolites in an epigenetic rat hepatocarcinogenesis model induced by treatment with a choline-deficient diet (CDAA, choline-deficient l-amino acid defined) over a period of 1 year, from the formation of steatosis, to the development of nodules and adenomas. A comparable choline-sufficient (CSAA) diet was used for the controls. The resonances of the methylene protons of the glycerol backbone in phospholipids were used to quantify the total concentration of such compounds. CDAA rat livers were found to have significantly higher levels of phospholipids, when compared to CSAA, throughout the entire carcinogenesis period. The tri-methyl protons of choline compounds serves to quantify total choline, and the vinyl and bis-allyl proton resonances can be used to not only quantify fatty acid concentrations but also to probe the number of double bonds in a fatty acid moiety. Early stages of carcinogenesis indicate a lower degree of double bonds in fatty acyl containing compounds in CDAA rat livers, when compared to CSAA. The results of this study are in agreement with those previously published in the literature on other rat hepatocarcinogenesis models.

Increased ratio of saturated to unsaturated C18 fatty acids in colonic adenocarcinoma: implications for cryotherapy and lipid raft function

Mammalian fatty acid synthase (FASE) overexpression has been shown in a number of human malignancies including colonic adenocarcinoma. Since FASE synthesizes only saturated fatty acids, we hypothesized that cancer cells have a greater proportion of long-chain saturated fatty acids. We studied and found an unequivocal increase in saturated C18 fatty acid (stearic acid) in colonic adenocarcinoma compared to adjacent normal colonic mucosa. The increase is even more striking when measured as a ratio of stearic acid to the unsaturated C18 fatty acids (oleic acid and linoleic acid). This change in fatty acid composition of the cancer cells should significantly alter their physical and biological properties. The increase in relative proportion of saturated fatty acids should make the cancer cells more susceptible to cryodamage and measurement of fatty acid composition of cancer cells may help individualize the temperature for cryotherapy. Also, the lipid alterations may affect the structure and functions of lipid rafts, which may enable the cancer cells to affect signaling mechanisms such as those involved in cell growth and apoptosis. Dietary or therapeutic interventions targeting lipid rafts may thus be an option for cancer treatment.