Melatonin Modulates lipid Metabolism in HepG2 Cells Cultured in High Concentrations of Oleic Acid: AMPK Pathway Activation may Play an Important Role

Melatonin exists as an active ingredient in several foods and has been reported to inhibit fatty liver disease in animals; however, its molecular mechanisms are not well elucidated. Herein, we explored effects of melatonin on lipid accumulation induced by oleic acid in HepG2 cells and characterized the underlying molecular mechanisms. Pretreatment with melatonin (0.1–0.3?mM) significantly inhibited accumulation of triglyceride and cholesterol induced by incubating HepG2 cells with high concentrations of oleic acid (oleic acid overload) (p?<?0.05). Melatonin pretreatment induced phosphorylation of AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC), causing their activation and inactivation, respectively. Expression levels of peroxisome proliferator activated receptor-α (PPARα) and its target gene carnitine palmitoyl-CoA transferase 1 (CPT1), which are associated with lipolysis, were upregulated by melatonin, whereas expression of sterol regulatory element binding protein-1c (SREBP-1c), fatty acid synthase (FAS), and stearoyl-CoA desaturase-1 (SCD1), which are associated with lipogenesis, were downregulated. Melatonin did not change expression of genes involved in cholesterol metabolism, including 3-hydroxy-3-methylglutaryl CoA reductase (HMGR) and SREBP-2. Melatonin inhibits lipid accumulation induced by oleic acid overload in HepG2 cells. The phosphorylation and activation of AMPK may have important roles in inactivating lipid anabolic pathways and activating triglyceride catabolic pathways.     

Inhibition of Paclitaxel-Induced Proteasome Activation Influences Paclitaxel Cytotoxicity in Breast Cancer Cells in a Sequence-Dependent Manner

Although the anti-tumour effects of paclitaxel result mainly from mitotic arrest, recent evidences suggest alternative mechanisms of cytotoxicity. Cell cycle, cell death, and gene expression assays were used to understand the molecular mechanisms of paclitaxel cytotoxicity in breast cancer cells. G₂/M cell cycle arrest and cell death coincided with the regulation of genes involved in cell death, cell cycle control, microtubule-based processes, oxidative stress, and ubiquitin-proteasome system. Induction of proteasome genes was also correlated with an accumulation of protein for proteasome subunits. Furthermore, a schedule-dependent regulation of paclitaxel-induced cytotoxicity was observed after combining paclitaxel and the proteasome inhibitor MG132. Proteasome inhibition after paclitaxel exposure induced the highest rate of growth inhibition and apoptosis, with no effect on mitotic arrest. These findings give support to clinical combinations of taxanes with proteasome inhibitors, outlining the importance of considering the sequence when designing such regimens.     

Rb Suppresses Collective Invasion,Circulation and Metastasis of Breast Cancer Cells in CD44-Dependent Manner

Basal-like breast carcinomas (BLCs) present with extratumoral lymphovascular invasion, are highly metastatic, presumably through a hematogenous route, have augmented expression of CD44 oncoprotein and relatively low levels of retinoblastoma (Rb) tumor suppressor. However, the causal relation among these features is not clear. Here, we show that Rb acts as a key suppressor of multiple stages of metastatic progression. Firstly, Rb suppresses collective cell migration (CCM) and CD44-dependent formation of F-actin positive protrusions in vitro and cell-cluster based lymphovascular invasion in vivo. Secondly, Rb inhibits the release of single cancer cells and cell clusters into the hematogenous circulation and subsequent metastatic growth in lungs. Finally, CD44 expression is required for collective motility and all subsequent stages of metastatic progression initiated by loss of Rb function. Altogether, our results suggest that Rb/CD44 pathway is a crucial regulator of CCM and metastatic progression of BLCs and a promising target for anti-BLCs therapy.     

德国油菜高油酸育种情况(英文)

德国近年来油菜高油酸育种的一些情况,其中包括高油酸育种的意义,育种方法,高油酸突变体的遗传特点,高油酸-低亚麻酸育种的可能性和高油酸油菜的应用前景等,对于我国育种新技术的改进、改良和创新研究有一定的意义.     

Death Receptor-Induced Apoptosis Signalling Regulation by Ezrin Is Cell Type Dependent and Occurs in a DISC-Independent Manner in Colon Cancer Cells

Ezrin belongs to the ERM (ezrin-radixin-moesin) protein family and has been demonstrated to regulate early steps of Fas receptor signalling in lymphoid cells, but its contribution to TRAIL-induced cell death regulation in adherent cancer cells remains unknown. In this study we report that regulation of FasL and TRAIL-induced cell death by ezrin is cell type dependant. Ezrin is a positive regulator of apoptosis in T-lymphoma cell line Jurkat, but a negative regulator in colon cancer cells. Using ezrin phosphorylation or actin-binding mutants, we provide evidence that negative regulation of death receptor-induced apoptosis by ezrin occurs in a cytoskeleton- and DISC-independent manner, in colon cancer cells. Remarkably, inhibition of apoptosis induced by these ligands was found to be tightly associated with regulation of ezrin phosphorylation on serine 66, the tumor suppressor gene WWOX and activation of PKA. Deficiency in WWOX expression in the liver cancer SK-HEP1 or the pancreatic Mia PaCa-2 cell lines as well as WWOX silencing or modulation of PKA activation by pharmacological regulators, in the colon cancer cell line SW480, abrogated regulation of TRAIL signalling by ezrin. Altogether our results show that death receptor pro-apoptotic signalling regulation by ezrin can occur downstream of the DISC in colon cancer cells.     

High Bak Expression Is Associated with a Favorable Prognosis in Breast Cancer and Sensitizes Breast Cancer Cells to Paclitaxel

Breast cancer has become the leading cause of cancer-related death among women. A large number of patients become resistant to drug chemotherapy. Paclitaxel (Taxol) is an effective chemotherapeutic agent used to treat cancer patients. Taxol has been widely used in human malignancies including breast cancer because it can stabilize microtubules resulting in cell death by causing an arrest during the G2/M phase of the cell cycle. Pro-apoptotic Bcl-2 antagonist killer 1 (Bak) plays an important role in Taxol-induced apoptosis in breast cancer. In our present study, we investigated the expression of the Bak protein and clinicopathological correlations in a large sample of breast cancer tissues by immunohistochemistry. We found that the percentage of high scores of Bak expression in breast cancer was significantly lower than that of the non-cancerous breast control tissue. In addition, lower Bak expression was positively associated with the clinical TNM stage of breast cancer with a significant decrease in overall survival compared with those with higher Bak expression especially in the Luminal and HER2 subtypes. Importantly, higher Bak expression predicted a favorable clinical outcome in the cases treated with Taxol indicated by a higher overall survival than that of patients with lower Bak expression especially in Luminal and HER2 subtypes. Furthermore, these results were confirmed in vitro since overexpression of Bak sensitized breast cancer cells to Taxol by inhibiting proliferation and promoting apoptosis; in contrast, downregulation of Bak through siRNA transfection inhibited Taxol induced-apoptosis. Therefore, our results demonstrate that Bak acts as a sensitive biomarker and favorable prognostic factor for Taxol treatment in breast cancer. The restoration of Bak expression would be therapeutically beneficial for Taxol resistant breast cancer patients.     

Comparative Effects of Boric Acid and Calcium Fructoborate on Breast Cancer Cells

Recent studies suggested that boron has a chemo-preventive role in prostate cancer. In the present report, we investigated the effects of calcium fructoborate (CF) and boric acid (BA) on activation of the apoptotic pathway in MDA-MB-231 human breast cancer cells. Exposure to BA and CF inhibited the proliferation of breast cancer cells in a dose-dependent manner. Treatment with CF but not BA resulted in a decrease in p53 and bcl-2 protein levels. Furthermore, after the treatment with CF, augmentation of pro-caspase-3 protein expression, cytosolic cytochrome c level, and caspase-3 activity were observed, indicating apoptotic cell death induction. This was also demonstrated by terminal deoxynucleotidyl transferase-mediated 2′-deoxyuridine 5′-triphosphate nick-end-labeling assay. In conclusion, our data provide arguments to the fact that both BA and CF inhibited the growth of breast cancer cells, while only CF induced apoptosis. Additional studies will be needed to identify the underlying mechanism responsible for the observed cellular responses to these compounds and to determine if BA and CF may be further evaluated as chemotherapeutic agents for human cancer.     

Fatty Acid Synthase Mediates the Epithelial-Mesenchymal Transition of Breast Cancer Cells

This study aimed to investigate the role of fatty acid synthase (FASN) in the epithelial-mesenchymal transition (EMT) of breast cancer cells. MCF-7 cells and MCF-7 cells overexpressing mitogen-activated protein kinase 5 (MCF-7-MEK5) were used in this study. MCF-7-MEK5 cells showed stable EMT characterized by increased vimentin and decreased E-cadherin expression. An In vivo animal model was established using the orthotopic injection of MCF-7 or MCF-7-MEK5 cells. Real-time quantitative PCR and western blotting were used to detect the expression levels of FASN and its downstream proteins liver fatty acid-binding protein (L-FABP) and VEGF/VEGFR-2 in both in vitro and in vivo models (nude mouse tumor tissues). In MCF-7-MEK5 cells, significantly increased expression of FASN was associated with increased levels of L-FABP and VEGF/VEGFR-2. Cerulenin inhibited MCF-7-MEK5 cell migration and EMT, and reduced FASN expression and down-stream proteins L-FABP, VEGF, and VEGFR-2. MCF-7-MEK5 cells showed higher sensitivity to Cerulenin than MCF-7 cells. Immunofluorescence revealed an increase of co-localization of FASN with VEGF on the cell membrane and with L-FABP within MCF-7-MEK5 cells. Immunohistochemistry further showed that increased percentage of FASN-positive cells in the tumor tissue was associated with increased percentages of L-FABP- and VEGF-positive cells and the Cerulenin treatment could reverse the effect. Altogether, our results suggest that FASN is essential to EMT possibly through regulating L-FABP, VEGF and VEGFR-2. This study provides a theoretical basis and potential strategy for effective suppression of malignant cells with EMT.     

Ethanol Tolerance in the Yeast Saccharomyces cerevisiae Is Dependent on Cellular Oleic Acid Content

In this investigation, we examined the effects of different unsaturated fatty acid compositions of Saccharomyces cerevisiae on the growth-inhibiting effects of ethanol. The unsaturated fatty acid (UFA) composition of S. cerevisiae is relatively simple, consisting almost exclusively of the mono-UFAs palmitoleic acid (Δ⁹Z-C_16:1) and oleic acid (Δ⁹Z-C_18:1), with the former predominating. Both UFAs are formed in S. cerevisiae by the oxygen- and NADH-dependent desaturation of palmitic acid (C_16:0) and stearic acid (C_18:0), respectively, catalyzed by a single integral membrane desaturase encoded by the OLE1 gene. We systematically altered the UFA composition of yeast cells in a uniform genetic background (i) by genetic complementation of a desaturase-deficient ole1 knockout strain with cDNA expression constructs encoding insect desaturases with distinct regioselectivities (i.e., Δ⁹ and Δ¹¹) and substrate chain-length preferences (i.e., C_16:0 and C_18:0); and, (ii) by supplementation of the same strain with synthetic mono-UFAs. Both experimental approaches demonstrated that oleic acid is the most efficacious UFA in overcoming the toxic effects of ethanol in growing yeast cells. Furthermore, the only other UFA tested that conferred a nominal degree of ethanol tolerance is cis-vaccenic acid (Δ¹¹Z-C_18:1), whereas neither Δ¹¹Z-C_16:1 nor palmitoleic acid (Δ⁹Z-C_16:1) conferred any ethanol tolerance. We also showed that the most ethanol-tolerant transformant, which expresses the insect desaturase TniNPVE, produces twice as much oleic acid as palmitoleic acid in the absence of ethanol and undergoes a fourfold increase in the ratio of oleic acid to palmitoleic acid in response to exposure to 5% ethanol. These findings are consistent with the hypothesis that ethanol tolerance in yeast results from incorporation of oleic acid into lipid membranes, effecting a compensatory decrease in membrane fluidity that counteracts the fluidizing effects of ethanol.     

High Oleic Acid Mutant in Soybean Induced by X-Ray Irradiation

Dry seeds of soybean [Glycine max (L.) Merr. var. Bay] were irradiated by X-rays (21.4 kR) and the M₂ generations were examined for the oleic acid content in their oil. The genetic variability of oleic acid content in the oil of the Bay variety was significantly increased by the X-ray treatment when compared with the Bay control. A mutant, designated as M23, was selected from 2747 M₂ plants, having an oleic acid content of 46.1%, twice as much as that in the normal Bay variety. A distinct inverse relationship was observed between the oleic and linoleic acid contents in M23. Mutant M23 isolated from the M₂ generations was confirmed to be always associated with a high oleic acid content under different environmental conditions in the M₃ generations.     

Wogonin Induced Calreticulin/Annexin A1 Exposure Dictates the Immunogenicity of Cancer Cells in a PERK/AKT Dependent Manner

In response to ionizing irradiation and certain chemotherapeutic agents, dying tumor cells elicit a potent anticancer immune response. However, the potential effect of wogonin (5,7-dihydroxy-8-methoxyflavone) on cancer immunogenicity has not been studied. Here we demonstrated for the first time that wogonin elicits a potent antitumor immunity effect by inducing the translocation of calreticulin (CRT) and Annexin A1 to cell plasma membrane as well as the release of high-mobility group protein 1 (HMGB1) and ATP. Signal pathways involved in this process were studied. We found that wogonin-induced reactive oxygen species (ROS) production causes an endoplasmic reticulum (ER) stress response, including the phosphorylation of PERK (PKR-like endoplasmic reticulum kinase)/PKR (protein kinase R) and eIF2α (eukaryotic initiation factor 2α), which served as upstream signal for the activation of phosphoinositide 3-kinase (PI3K)/AKT, inducing calreticulin (CRT)/Annexin A1 cell membrane translocation. P22/CHP, a Ca²⁺-binding protein, was associated with CRT and was required for CRT translocation to cell membrane. The releases of HMGB1 and ATP from wogonin treated MFC cells, alone or together with other possible factors, activated dendritic cells and induced cytokine releases. In vivo study confirmed that immunization with wogonin-pretreated tumor cells vaccination significantly inhibited homoplastic grafted gastric tumor growth in mice and a possible inflammatory response was involved. In conclusion, the activation of PI3K pathway elicited by ER stress induced CRT/Annexin A1 translocation (“eat me” signal) and HMGB1 release, mediating wogonin-induced immunity of tumor cell vaccine. This indicated that wogonin is a novel effective candidate of immunotherapy against gastric tumor.     

Targeting Breast Cancer Stem Cells

The potential roles of breast cancer stem cells (BCSCs) in tumor initiation and recurrence have been recognized for many decades. Due to their strong capacity for self-renewal and differentiation, BCSCs are the major reasons for poor clinical outcomes and low therapeutic response. Several hypotheses on the origin of cancer stem cells have been proposed, including critical gene mutations in stem cells, dedifferentiation of somatic cells, and cell plasticity remodeling by epithelial-mesenchymal transition (EMT) and the tumor microenvironment. Moreover, the tumor microenvironment, including cellular components and cytokines, modulates the self-renewal and therapeutic resistance of BCSCs. Small molecules, antibodies, and chimeric antigen receptor (CAR)-T cells targeting BCSCs have been developed, and their applications in combination with conventional therapies are undergoing clinical trials. In this review, we focus on the features of BCSCs, emphasize the major factors and tumor environment that regulate the stemness of BCSCs, and discuss potential BCSC-targeting therapies.     

Eicosapentaenoic Acid and Rosiglitazone Increase Adiponectin in an Additive and PPARγ‐Dependent Manner in Human Adipocytes

Adiponectin, an anti‐inflammatory and insulin‐sensitizing protein secreted from adipose tissue, may be modulated by dietary fatty acids, although the mechanism is not fully known. Our objective was to investigate the effect of long‐chain n‐3 polyunsaturated fatty acids (PUFAs) on adiponectin in cultured human adipocytes, and to elucidate the role of peroxisome proliferator‐activated receptor‐γ (PPARγ) in this regulation. Isolated human adipocytes were cultured for 48 h with 100 µmol/l eicosapentaenoic acid (C20:5n‐3, EPA), docosahexaenoic acid (C22:6n‐3, DHA), palmitic acid (C16:0), 100 µmol/l EPA plus 100 µmol/l DHA, or bovine serum albumin (control). Additionally, adipocytes were treated for 48 h with a PPARγ antagonist (BADGE) or agonist (rosiglitazone) in isolation or in conjunction with either EPA or DHA. At 48 h, EPA and DHA increased (P < 0.05) adiponectin secretion by 88 and 47%, respectively, while EPA, but not DHA, also increased (136%, P < 0.001) cellular adiponectin protein. Interestingly, PPARγ antagonism completely abolished the DHA‐mediated increase in secreted adiponectin, but only partially attenuated the EPA‐mediated response. Thus, EPA's effects on adiponectin do not appear to be entirely PPARγ mediated. Rosiglitazone increased (P < 0.001) the secreted and cellular adiponectin protein (90 and 582%, respectively). Finally, the effects of EPA and rosiglitazone on adiponectin secretion were additive (+230% at 48 h combined, compared to 121 and 124% by EPA or rosiglitazone alone, respectively). Overall, our findings emphasize the therapeutic importance of long‐chain n‐3 PUFA alone, or in combination with a PPARγ agonist, as a stimulator of adiponectin, a key adipokine involved in obesity and related diseases.     

龙生型高油酸花生种质油酸亚油酸含量及其比值的遗传分析

应用植物数量性状主基因+多基因混合遗传模型,对2个龙生型花生高油酸种质与低油酸珍珠豆型品种杂交组合F2的油酸、亚油酸含量及其比值(O/L值)进行遗传分析,结果表明:花生油酸、亚油酸含量的遗传均表现为1对主基因加性-显性模型。控制油酸含量主基因的加性、显性效应值和遗传率在组合I中分别为8.6281、-2.0164和65.26%,在组合II中则分别为10.6638、1.0652和71.39%;控制亚油酸含量主基因的加性、显性效应值和遗传率在组合I中分别为8.0327、1.2858和73.64%,在组合II中则分别为9.0885、-1.0826和71.59%。O/L值的遗传表现为2对主基因加性-显性-上位性模型。2对主基因的加性效应值分别为0.6855、0.6814(组合I)和1.6842、0.8835(组合II),显性效应值分别为-0.6838、0.024(组合I)和-1.6559、-0.5127(组合II);加性×加性效应(i)、加性×显性效应(jab)、显性×加性效应(jba)、显性×显性效应(l)分别为0.6812、0.024、-0.6803、-0.0244(组合I)和0.8822、-0.5124、-0.8594、0.496(组合II);组合I、II主基因遗传率分别为82.57%和88.64%。