Endogenous ether lipids differentially promote tumor aggressiveness by regulating the SK3 channel.

SK3 channels are potassium channels found to promote tumor aggressiveness. We have previously demonstrated that SK3 is regulated by synthetic ether lipids, but the role of endogenous ether lipids is unknown. Here, we have studied the role of endogenous alkyl- and alkenyl-ether lipids on SK3 channels and on the biology of cancer cells. Experiments revealed that the suppression of alkylglycerone phosphate synthase or plasmanylethanolamine desaturase 1, which are key enzymes for alkyl- and alkenyl-ether-lipid synthesis, respectively, decreased SK3 expression by increasing micro RNA (miR)-499 and miR-208 expression, leading to a decrease in SK3-dependent calcium entry, cell migration, and matrix metalloproteinase 9-dependent cell adhesion and invasion. We identified several ether lipids that promoted SK3 expression and found a differential role of alkyl- and alkenyl-ether lipids on SK3 activity. The expressions of alkylglycerone phosphate synthase, SK3, and miR were associated in clinical samples emphasizing the clinical consistency of our observations. To our knowledge, this is the first report showing that ether lipids differentially control tumor aggressiveness by regulating an ion channel. This insight provides new possibilities for therapeutic interventions, offering clinicians an opportunity to manipulate ion channel dysfunction by adjusting the composition of ether lipids.

Variable effects of periprostatic adipose tissue on prostate cancer cells: Role of adipose tissue lipid composition and cancer cells related factors.

BACKGROUND: Periprostatic adipose tissue (PPAT) is likely to modulate prostate cancer (PCa) progression. We analyzed the variations in the effect of PPAT on cancer cells, according to its fatty acid (FA) composition and tumor characteristics. METHODS: The expression of markers of aggressiveness Ki67 and Zeb1, and epigenetic marks that could be modified during PCa progression, was analyzed by immunohistochemistry on a tissue-micro-array containing 59 pT3 PCa, including intra-prostatic areas and extra-prostatic foci in contact with PPAT belonging to the same tumor. In addition, we cocultivated PC3 and LNCaP cell lines with PPAT, which were then analyzed for FA composition. RESULTS: Although the contact between PPAT and cancer cells led overall to an increase in Ki67 and Zeb1, and a decrease in the epigenetic marks 5MC, 5HMC, and H3K27ac, these effects were highly heterogeneous. Increased proliferation in extra-prostatic areas was associated with the international society of uropathology score. PC3 and LNCaP cocultures with PPAT led to increased Ki67, Zeb1 and H3K27me3, but only for PPAT associated with aggressive PCa. PC3 proliferation was correlated with high 20.2 n-6 and low 20.5n-3 in PPAT. CONCLUSIONS: These results suggest that the effects of PPAT on cancer cells may depend on both PCa characteristics and PPAT composition, and could lead to propose nutritional supplementation.

Accumulation of Arachidonic Acid, Precursor of Pro-Inflammatory Eicosanoids, in Adipose Tissue of Obese Women: Association with Breast Cancer Aggressiveness Indicators.

While obesity is linked to cancer risk, no studies have explored the consequences of body mass index (BMI) on fatty acid profiles in breast adipose tissue and on breast tumor aggressiveness indicators. Because of this, 261 breast adipose tissue samples of women with invasive breast carcinoma were analyzed. Fatty acid profile was established by gas chromatography. For normal-weight women, major changes in fatty acid profile occurs after menopause, with the enrichment of long-chain polyunsaturated fatty acids (LC-PUFAs) of both n-6 and n-3 series enrichment, but a stable LC-PUFAs n-6/n-3 ratio across age. BMI impact was analyzed by age subgroups to overcome the age effect. BMI increase is associated with LC-PUFAs n-6 accumulation, including arachidonic acid. Positive correlations between BMI and several LC-PUFAs n-6 were observed, as well as a strong imbalance in the LC-PUFAs n-6/n-3 ratio. Regarding cancer, axillary lymph nodes (p = 0.02) and inflammatory breast cancer (p = 0.08) are more frequently involved in obese women. Increased BMI induces an LC-PUFAs n-6 accumulation, including arachidonic acid, in adipose tissue. This may participate in the development of low-grade inflammation in obese women and breast tumor progression. These results suggest the value of lifestyle and LC-PUFAs n-3 potential, in the context of obesity and breast cancer secondary/tertiary prevention.

Development of a High-Performance Thin-Layer Chromatography Method for the Quantification of Alkyl Glycerolipids and Alkenyl Glycerolipids from Shark and Chimera Oils and Tissues.

Ether lipids are composed of alkyl lipids with an ether bond at the sn-1 position of a glycerol backbone and alkenyl lipids, which possess a vinyl ether bond at the sn-1 position of the glycerol. These ether glycerolipids are present either as polar glycerophospholipids or neutral glycerolipids. Before studying the biological role of molecular species of ether glycerolipids, there is a need to separate and quantify total alkyl and alkenyl glycerolipids from biological samples in order to determine any variation depending on tissue or physiopathological conditions. Here, we detail the development of the first high-performance thin-layer chromatography method for the quantification of total alkyl and alkenyl glycerolipids thanks to the separation of their corresponding alkyl and alkenyl glycerols. This method starts with a reduction of all lipids after extraction, resulting in the reduction of neutral and polar ether glycerolipids into alkyl and alkenyl glycerols, followed by an appropriate purification and, finally, the linearly ascending development of alkyl and alkenyl glycerols on high-performance thin-layer chromatography plates, staining, carbonization and densitometric analysis. Calibration curves were obtained with commercial alkyl and alkenyl glycerol standards, enabling the quantification of alkyl and alkenyl glycerols in samples and thus directly obtaining the quantity of alkyl and alkenyl lipids present in the samples. Interestingly, we found a differential quantity of these lipids in shark liver oil compared to chimera. We quantified alkyl and alkenyl glycerolipids in periprostatic adipose tissues from human prostate cancer and showed the feasibility of this method in other biological matrices (muscle, tumor).

Adipocytes Promote Breast Cancer Cell Survival and Migration through Autophagy Activation.

White adipose tissue interacts closely with breast cancers through the secretion of soluble factors such as cytokines, growth factors or fatty acids. However, the molecular mechanisms of these interactions and their roles in cancer progression remain poorly understood. In this study, we investigated the role of fatty acids in the cooperation between adipocytes and breast cancer cells using a co-culture model. We report that adipocytes increase autophagy in breast cancer cells through the acidification of lysosomes, leading to cancer cell survival in nutrient-deprived conditions and to cancer cell migration. Mechanistically, the disturbance of membrane phospholipid composition with a decrease in arachidonic acid content is responsible for autophagy activation in breast cancer cells induced by adipocytes. Therefore, autophagy might be a central cellular mechanism of white adipose tissue interactions with cancer cells and thus participate in cancer progression.

Identification of a Positive Association between Mammary Adipose Cholesterol Content and Indicators of Breast Cancer Aggressiveness in a French Population.

BACKGROUND: Several studies have recently highlighted important roles for adipose tissue in cancer. However, few have examined adipose tissue cholesterol, and no study has been performed in breast adipose tissue associated with breast tumors. OBJECTIVES: The present work was designed to determine if breast adipose tissue cholesterol from the tumor-surrounding area is associated with breast cancer aggressiveness. METHODS: Between 2009 and 2011, 215 breast adipose tissue samples were collected at the Tours University Hospital (France) during surgery of women (aged 28-89 y) with invasive breast cancer. Associations of free cholesterol (FC), esterified cholesterol (EC), and total cholesterol (TC) amounts with clinical variables (age, BMI, and treated or untreated hypercholesterolemia) and tumor aggressiveness parameters [phenotype, grade, presence of inflammatory breast cancer (IBC), and multifocality] were tested using Student's t test and after ANOVA. RESULTS: The predominant form of cholesterol in adipose tissue was FC, and 50% of patients had no detectable EC. The adipose tissue FC content (µg/mg total lipid) was 18% greater in patients >70 y old than in those 40-49 y old (P < 0.05) and the TC content tended to be 12% greater in untreated hypercholesterolemic patients than in normocholesterolemic patients (P = 0.06). Breast adipose cholesterol concentrations were increased in tissues obtained from patients with human-epidermal-growth-factor-receptor-2 (HER2) phenotype (+13% FC; P < 0.05 compared with luminal A), IBC (+15% FC; P = 0.06 compared with noninflammatory tumors), as well as with multifocal triple-negative tumors (+34% FC, P < 0.05; +30% TC, P < 0.05, compared with unifocal triple-negative tumors). Among patients with triple-negative tumors, hypercholesterolemia was significantly more common (P < 0.05) in patients with multifocal tumors (64%) than in patients with unifocal tumors (25%). CONCLUSIONS: This study is the first of this magnitude that analyzes cholesterol concentrations in adipose tissue from female breast cancer patients. An increase in breast adipose tissue cholesterol content may contribute to breast cancer aggressiveness (HER2 phenotype, multifocality of triple-negative tumors, and IBC).

Protein Farnesylation Takes Part in Arabidopsis Seed Development.

Protein farnesylation is a post-translational modification regulated by the ERA1 (Enhanced Response to ABA 1) gene encoding the ß-subunit of the protein farnesyltransferase in Arabidopsis. The era1 mutants have been described for over two decades and exhibit severe pleiotropic phenotypes, affecting vegetative and flower development. We further investigated the development and quality of era1 seeds. While the era1 ovary contains numerous ovules, the plant produces fewer seeds but larger and heavier, with higher protein contents and a modified fatty acid distribution. Furthermore, era1 pollen grains show lower germination rates and, at flower opening, the pistils are immature and the ovules require one additional day to complete the embryo sac. Hand pollinated flowers confirmed that pollination is a major obstacle to era1 seed phenotypes, and a near wild-type seed morphology was thus restored. Still, era1 seeds conserved peculiar storage protein contents and altered fatty acid distributions. The multiplicity of era1 phenotypes reflects the diversity of proteins targeted by the farnesyltransferase. Our work highlights the involvement of protein farnesylation in seed development and in the control of traits of agronomic interest.

Low Levels of Omega-3 Long-Chain Polyunsaturated Fatty Acids Are Associated with Bone Metastasis Formation in Premenopausal Women with Breast Cancer: A Retrospective Study.

In the present study, we investigated various biochemical, clinical, and histological factors associated with bone metastases in a large cohort of pre- and postmenopausal women with breast cancer. Two hundred and sixty-one consecutive women with breast cancer were included in this study. Breast adipose tissue specimens were collected during surgery. After having established the fatty acid profile of breast adipose tissue by gas chromatography, we determined whether there were differences associated with the occurrence of bone metastases in these patients. Regarding the clinical and histological criteria, a majority of the patients with bone metastases (around 70%) had tumors with a luminal phenotype and 59% of them showed axillary lymph node involvement. Moreover, we found a negative association between the levels of n-3 long-chain polyunsaturated fatty acids (LC-PUFA) in breast adipose tissue and the development of bone metastases in premenopausal women. No significant association was observed in postmenopausal women. In addition to a luminal phenotype and axillary lymph node involvement, low levels of n-3 LC-PUFA in breast adipose tissue may constitute a risk factor that contributes to breast cancer bone metastases formation in premenopausal women.

Development of a Novel High-Performance Thin Layer Chromatography-Based Method for the Simultaneous Quantification of Clinically Relevant Lipids from Cells and Tissue Extracts.

Lipids such as cholesterol, triacylglycerols, and fatty acids play important roles in the regulation of cellular metabolism and cellular signaling pathways and, as a consequence, in the development of various diseases. It is therefore important to understand how their metabolism is regulated to better define the components involved in the development of various human diseases. In the present work, we describe the development and validation of a high-performance thin layer chromatography (HPTLC) method allowing the separation and quantification of free cholesterol, cholesteryl esters, nonesterified fatty acids, and triacylglycerols. This method will be of interest as the quantification of these lipids in one single assay is difficult to perform.

Apolipoprotein-mediated regulation of lipid metabolism induces distinctive effects in different types of breast cancer cells.

BACKGROUND: The highest incidence of breast cancer is in the Western world. Several aspects of the Western lifestyle are known risk factors for breast cancer. In particular, previous studies have shown that cholesterol levels can play an important role in the regulation of tumor progression. METHODS: In the present study, we modulated cholesterol metabolism in the human breast cancer cell lines MCF-7 and MDA-MB-231 using a genetic approach. Apolipoprotein A-I (apoA-I) and apolipoprotein E (apoE) were expressed in these cell lines to modulate cholesterol metabolism. The effects of these apolipoproteins on cancer cell properties were examined. RESULTS: Our results show that both apolipoproteins can regulate cholesterol metabolism and can control the epithelial-to-mesenchymal transition process. However, these effects were different depending on the cell type. We show that expressing apoA-I or apoE stimulates proliferation, migration, and tumor growth of MCF-7 cells. However, apoA-I or apoE reduces proliferation and migration of MDA-MB-231 cells. CONCLUSIONS: These data suggest that modulating sterol metabolism may be most effective at limiting tumor progression in models of triple-negative cancers.

Epinephrine Infiltration of Adipose Tissue Impacts MCF7 Breast Cancer Cells and Total Lipid Content.

BACKGROUND: Considering the positive or negative potential effects of adipocytes, depending on their lipid composition, on breast tumor progression, it is important to evaluate whether adipose tissue (AT) harvesting procedures, including epinephrine infiltration, may influence breast cancer progression. METHODS: Culture medium conditioned with epinephrine-infiltrated adipose tissue was tested on human Michigan Cancer Foundation-7 (MCF7) breast cancer cells, cultured in monolayer or in oncospheres. Lipid composition was evaluated depending on epinephrine-infiltration for five patients. Epinephrine-infiltrated adipose tissue (EI-AT) or corresponding conditioned medium (EI-CM) were injected into orthotopic breast carcinoma induced in athymic mouse. RESULTS: EI-CM significantly increased the proliferation rate of MCF7 cells Moreover EI-CM induced an output of the quiescent state of MCF7 cells, but it could be either an activator or inhibitor of the epithelial mesenchymal transition as indicated by gene expression changes. EI-CM presented a significantly higher lipid total weight compared with the conditioned medium obtained from non-infiltrated-AT of paired-patients. In vivo, neither the EI-CM or EI-AT injection significantly promoted MCF7-induced tumor growth. CONCLUSIONS: Even though conditioned media are widely used to mimic the secretome of cells or tissues, they may produce different effects on tumor progression, which may explain some of the discrepancy observed between in vitro, preclinical and clinical data using AT samples.

Low eicosapentaenoic acid and gamma-linolenic acid levels in breast adipose tissue are associated with inflammatory breast cancer.

OBJECTIVE: Since it is thought that breast adipose tissue could influence breast cancer clinical presentation, we wanted to characterize specifically the relationship between breast adipose tissue fatty acid profile and Inflammatory Breast cancer (IBC). METHODS: Two hundred thirty-four women presenting with breast cancer were managed in our centre between January 2009 and December 2011. Breast adipose tissue specimens were collected during breast surgery. We established the biochemical profile of adipose tissue fatty acids (FA) by gas chromatography and assessed whether there were differences in function of the presence of breast inflammation or not. RESULTS: We found that IBC was associated with decreased levels in breast adipose tissue of eicosapentaenoic acid (EPA), one of the two main polyunsaturated n-3 fatty acids (n-3 PUFA) of marine origin, but also with decreased levels of Gamma Linolenic acid (GLA). Inversely, an increase in palmitic acid levels was associated with IBC. CONCLUSION: These differences in lipid content may contribute to the occurrence of breast cancer inflammation.

Synthesis of Alkyl-Glycerolipids Standards for Gas Chromatography Analysis: Application for Chimera and Shark Liver Oils.

Natural O-alkyl-glycerolipids, also known as alkyl-ether-lipids (AEL), feature a long fatty alkyl chain linked to the glycerol unit by an ether bond. AEL are ubiquitously found in different tissues but, are abundant in shark liver oil, breast milk, red blood cells, blood plasma, and bone marrow. Only a few AEL are commercially available, while many others with saturated or mono-unsaturated alkyl chains of variable length are not available. These compounds are, however, necessary as standards for analytical methods. Here, we investigated different reported procedures and we adapted some of them to prepare a series of 1-O-alkyl-glycerols featuring mainly saturated alkyl chains of various lengths (14:0, 16:0, 17:0, 19:0, 20:0, 22:0) and two monounsaturated chains (16:1, 18:1). All of these standards were fully characterized by NMR and GC-MS. Finally, we used these standards to identify the AEL subtypes in shark and chimera liver oils. The distribution of the identified AEL were: 14:0 (20-24%), 16:0 (42-54%) and 18:1 (6-16%) and, to a lesser extent, (0.2-2%) for each of the following: 16:1, 17:0, 18:0, and 20:0. These standards open the possibilities to identify AEL subtypes in tumours and compare their composition to those of non-tumour tissues.

Fatty acid profile in peri-prostatic adipose tissue and prostate cancer aggressiveness in African-Caribbean and Caucasian patients.

BACKGROUND: Genetic and nutritional factors have been linked to the risk of aggressive prostate cancer (PCa). The fatty acid (FA) composition of peri-prostatic adipose tissue (PPAT), which reflects the past FA intake, is potentially involved in PCa progression. We analysed the FA composition of PPAT, in correlation with the ethno-geographical origin of the patients and markers of tumour aggressiveness. METHODS: From a cohort of 1000 men treated for PCa by radical prostatectomy, FA composition of PPAT was analysed in 156 patients (106 Caucasians and 50 African-Caribbeans), 78 with an indolent tumour (ISUP group 1 + pT2 + PSA <10 ng/mL) and 78 with an aggressive tumour (ISUP group 4-5 + pT3). The effect of FA extracted from PPAT on in-vitro migration of PCa cells DU145 was studied in 72 patients, 36 Caucasians, and 36 African-Caribbeans. RESULTS: FA composition differed according to the ethno-geographical origin. Linoleic acid, an essential n-6 FA, was 2-fold higher in African-Caribbeans compared with Caucasian patients, regardless of disease aggressiveness. In African-Caribbeans, the FA profile associated with PCa aggressiveness was characterised by low level of linoleic acid along with high levels of saturates. In Caucasians, a weak and negative association was observed between eicosapentaenoic acid level (an n-3 FA) and disease aggressiveness. In-vitro migration of PCa cells using PPAT from African-Caribbean patients was associated with lower content of linoleic acid. CONCLUSION: These results highlight an important ethno-geographical variation of PPAT, in both their FA content and association with tumour aggressiveness.

Long chain n-3 polyunsaturated fatty acids increase the efficacy of docetaxel in mammary cancer cells by downregulating Akt and PKCε/δ-induced ERK pathways.

Taxanes can induce drug resistance by increasing signaling pathways such as PI3K/Akt and ERK, which promote survival and cell growth in human cancer cells. We have previously shown that long chain n-3 polyunsaturated fatty acids, such as docosahexaenoic acid (DHA, 22:6n-3) decrease resistance of experimental mammary tumors to anticancer drugs. Our objective was to determine whether DHA could increase tumor sensitivity to docetaxel by down-regulating these survival pathways. In docetaxel-treated MDA-MB-231 cells, phosphorylated-ERK1/2 levels were increased by 60% in membrane and nuclear compartments, compared to untreated cells. Our data showed that ERK1/2 activation depended on PKC activation since: i) enzastaurin (a pan-PKC inhibitor) blocked docetaxel-induced ERK1/2 phosphorylation ii) docetaxel increased PKC activity by 30% and phosphatidic acid level by 1.6-fold iii) inhibition of PKCε and PKCδ by siRNA resulted in reduced phosphorylated ERK1/2 levels. In DHA-supplemented cells, docetaxel was unable to increase PKCε and δ levels in membrane and nuclear fractions, resulting in diminished ERK1/2 phosphorylation and increased docetaxel efficacy. Reduced membrane level of PKCε and PKCδ was associated with significant incorporation of DHA in all phospholipids, including phosphatidylcholine which is a major source of phosphatidic acid. Additionally, examination of the Akt pathway showed that DHA could repress docetaxel-induced Ser473Akt phosphorylation. In rat mammary tumors, dietary DHA supplementation during docetaxel chemotherapy repressed ERK and Akt survival pathways and in turn strongly improved taxane efficacy. The P-ERK level was negatively correlated with tumor regression. These findings are of potential clinical importance in treating chemotherapy-refractory cancer.

Reduced cardiolipin content decreases respiratory chain capacities and increases ATP synthesis yield in the human HepaRG cells.

Cardiolipin (CL) is a unique mitochondrial phospholipid potentially affecting many aspects of mitochondrial function/processes, i.e. energy production through oxidative phosphorylation. Most data focusing on implication of CL content and mitochondrial bioenergetics were performed in yeast or in cellular models of Barth syndrome. Previous work reported that increase in CL content leads to decrease in liver mitochondrial ATP synthesis yield. Therefore the aim of this study was to determine the effects of moderate decrease in CL content on mitochondrial bioenergetics in human hepatocytes. For this purpose, we generated a cardiolipin synthase knockdown (shCLS) in HepaRG hepatoma cells showing bioenergetics features similar to primary human hepatocytes. shCLS cells exhibited a 55% reduction in CLS gene and a 40% decrease in protein expression resulting in a 45% lower content in CL compared to control (shCTL) cells. Oxygen consumption was significantly reduced in shCLS cells compared to shCTL regardless of substrate used and energy state analyzed. Mitochondrial low molecular weight supercomplex content was higher in shCLS cells (+60%) compared to shCTL. Significant fragmentation of the mitochondrial network was observed in shCLS cells compared to shCTL cells. Surprisingly, mitochondrial ATP synthesis was unchanged in shCLS compared to shCTL cells but exhibited a higher ATP:O ratio (+46%) in shCLS cells. Our results suggest that lowered respiratory chain activity induced by moderate reduction in CL content may be due to both destabilization of supercomplexes and mitochondrial network fragmentation. In addition, CL content may regulate mitochondrial ATP synthesis yield.

Regulation of hepatic cardiolipin metabolism by TNFα: Implication in cancer cachexia.

Cardiolipin (CL) content accumulation leads to an increase in energy wasting in liver mitochondria in a rat model of cancer cachexia in which tumor necrosis factor alpha (TNFα) is highly expressed. In this study we investigated the mechanisms involved in liver mitochondria CL accumulation in cancer cachexia and examined if TNFα was involved in this process leading to mitochondrial bioenergetics alterations. We studied gene, protein expression and activity of the main enzymes involved in CL metabolism in liver mitochondria from a rat model of cancer cachexia and in HepaRG hepatocyte-like cells exposed to 20 ng/ml of TNFα for 12 h. Phosphatidylglycerolphosphate synthase (PGPS) gene expression was increased 2.3-fold (p<0.02) and cardiolipin synthase (CLS) activity decreased 44% (p<0.03) in cachectic rat livers compared to controls. CL remodeling enzymes monolysocardiolipin acyltransferase (MLCL AT-1) activity and tafazzin (TAZ) gene expression were increased 30% (p<0.01) and 50% (p<0.02), respectively, in cachectic rat livers compared to controls. Incubation of hepatocytes with TNFα increased CL content 15% (p<0.05), mitochondrial oxygen consumption 33% (p<0.05), PGPS gene expression 44% (p<0.05) and MLCL AT-1 activity 20% (p<0.05) compared to controls. These above findings strongly suggest that in cancer cachexia, TNFα induces a higher energy wasting in liver mitochondria by increasing CL content via upregulation of PGPS expression.

Cholesterol uptake disruption, in association with chemotherapy, is a promising combined metabolic therapy for pancreatic adenocarcinoma.

The malignant progression of pancreatic ductal adenocarcinoma (PDAC) is accompanied by a profound desmoplasia, which forces proliferating tumor cells to metabolically adapt to this new microenvironment. We established the PDAC metabolic signature to highlight the main activated tumor metabolic pathways. Comparative transcriptomic analysis identified lipid-related metabolic pathways as being the most highly enriched in PDAC, compared with a normal pancreas. Our study revealed that lipoprotein metabolic processes, in particular cholesterol uptake, are drastically activated in the tumor. This process results in an increase in the amount of cholesterol and an overexpression of the low-density lipoprotein receptor (LDLR) in pancreatic tumor cells. These findings identify LDLR as a novel metabolic target to limit PDAC progression. Here, we demonstrate that shRNA silencing of LDLR, in pancreatic tumor cells, profoundly reduces uptake of cholesterol and alters its distribution, decreases tumor cell proliferation, and limits activation of ERK1/2 survival pathway. Moreover, blocking cholesterol uptake sensitizes cells to chemotherapeutic drugs and potentiates the effect of chemotherapy on PDAC regression. Clinically, high PDAC Ldlr expression is not restricted to a specific tumor stage but is correlated to a higher risk of disease recurrence. This study provides a precise overview of lipid metabolic pathways that are disturbed in PDAC. We also highlight the high dependence of pancreatic cancer cells upon cholesterol uptake, and identify LDLR as a promising metabolic target for combined therapy, to limit PDAC progression and disease patient relapse.

Cardiolipin content is involved in liver mitochondrial energy wasting associated with cancer-induced cachexia without the involvement of adenine nucleotide translocase.

Cancer-induced cachexia describes the progressive skeletal muscle wasting associated with many cancers leading to shortened survival time in cancer patients. We previously reported that cardiolipin content and energy-wasting processes were both increased in liver mitochondria in a rat model of peritoneal carcinosis (PC)-induced cachexia. To increase the understanding of the cellular biology of cancer cachexia, we investigated the involvement of adenine nucleotide translocator (ANT) in mitochondrial energy-wasting processes in liver mitochondria of PC and pair-fed control rats and its interactions with cardiolipin in isolated liver mitochondria from healthy rats exposed to cardiolipin-enriched liposomes. We showed in this study that functional ANT content was decreased in liver mitochondria from PC rats but without any effects on the efficiency of ATP synthesis. Moreover, non-phosphorylating energy wasting was not affected by saturating concentrations of carboxyatractylate (CAT), a potent inhibitor of ANT, in liver mitochondria from PC rats. Decreased efficiency of ATP synthesis was found in normal liver mitochondria exposed to cardiolipin-enriched liposomes, with increased non-phosphorylating energy wasting, thus mimicking mitochondria from PC rats. However, the functional ANT content in these cardiolipin-enriched mitochondria was unchanged, although non-phosphorylating energy wasting was reduced by CAT-induced inhibition of ANT. Finally, non-phosphorylating energy wasting was increased in cardiolipin-enriched mitochondria with substrates for complexes 1 and 2, but not for complex 4. In conclusion, increased energy wasting measured in liver mitochondria from rats with cancer cachexia is dependent on cardiolipin but independent of ANT. Interactions between ANT and cardiolipin are modified when cancer cachexia occurs.

Pivotal role of the lipid Raft SK3-Orai1 complex in human cancer cell migration and bone metastases.

The SK3 channel, a potassium channel, was recently shown to control cancer cell migration, a critical step in metastasis outgrowth. Here, we report that expression of the SK3 channel was markedly associated with bone metastasis. The SK3 channel was shown to control constitutive Ca(2+) entry and cancer cell migration through an interaction with the Ca(2+) channel Orai1. We found that the SK3 channel triggers an association with the Orai1 channel within lipid rafts. This localization of an SK3-Orai1 complex seemed essential to control cancer cell migration. This suggests that the formation of this complex in lipid rafts is a gain-of-function, because we showed that none of the individual proteins were able to promote the complete phenotype. We identified the alkyl-lipid Ohmline as a disrupting agent for SK3-Orai1 lipid raft localization. Upon Ohmline treatment, the SK3-Orai1 complex moved away from lipid rafts, and SK3-dependent Ca(2+) entry, migration, and bone metastases were subsequently impaired. The colocalization of SK3 and Orai1 in primary human tumors and bone metastases further emphasized the clinical relevance of our observations. Targeting SK3-Orai1 in lipid rafts may inaugurate innovative approaches to inhibit bone metastases.