PPAR Receptors Expressed from Vectors Containing CMV Promoter Can Enhance Self-Transcription in the Presence of Fatty Acids from CLA-Enriched Egg Yolks-A Novel Method for Studies of PPAR Ligands.

PPAR receptors are ligand-dependent transcription factors activated in response to various small lipophilic ligands controlling the expression of different genes involved in cellular differentiation, development, metabolism, and tumorigenesis. Unexpectedly, our previous studies have shown that single plasmid-based expression of PPARs under the control of CMV promoter/enhancer was significantly elevated in the presence of PPAR agonists. Here we show that the PPAR reporters controlled by the CMV promoter/enhancer, that was shown to contain three internal non-canonical PPRE elements, can be used as a fast screening system for more effective PPAR ligands. This model allowed us to confirm our previous results indicating that fatty acids of CLA-enriched egg yolks (EFA-CLAs) are efficient PPAR ligands that can specifically upregulate the expression of PPARα and PPARγ leading to downregulation of MCF-7 cancer cell proliferation. We also show that synthetic cis9,trans11CLA is more effective in transactivation of PPARγ, while trans10,cis12CLA of PPARα receptor indicating the selectivity of the CLA isomers. This report presents a novel, fast, and reliable strategy for simple testing of PPAR ligands using PPAR expressing plasmids containing the CMV promoter/enhancer that can trigger the positive feedback loop of PPAR self-transcription in the presence of PPAR ligands.

Fatty Acids of CLA-enriched Egg Yolks Can Induce Mitochondrial Pathway of Apoptosis in MCF-7 Breast Cancer Cells.

BACKGROUND: Fatty acids from conjugated linoleic acid (CLA)-enriched egg yolk suppressed the viability of the MCF-7 cancer line more effectively than non-enriched egg yolk. Herein we aimed to determine the molecular mechanisms by analysing the expression and activation of proteins involved in cellular stress and apoptosis signaling. MATERIALS AND METHODS: Forty-eight Isa Brown laying hens (26-week-old) were fed a fortified (0.75% CLA) or a control diet (0% CLA) for 4 months. Collected eggs were used to obtain CLA-enriched (EFA-CLA) or non-enriched (EFA) fatty acid extracts for the treatment of the MCF-7 cancer cell line. Protein levels were analysed by PathScan® Stress and Apoptosis Signalling Antibody Array and western blot method. RESULTS: Treatment with EFA-CLA led to activation of caspase signalling as main effector of apoptosis. It also increased levels of pro-apoptotic B-cell lymphoma 2 family proteins as well as promoted the release of cytochrome c, second mitochondria-derived activator of caspase and mitochondrial serine protease from mitochondria to the cytoplasm. EFA-CLA increased levels of tumour protein 53 and mothers against decapentaplegic homolog 2 tumour suppressors, and activated p38 mitogen-activated protein kinases and stress-activated protein kinase/c-Jun NH2-terminal kinase proteins. Finally, treatment down-regulated anti-apoptotic extracellular signal-regulated protein kinases 1 and 2, RAC-alpha serine/threonine-protein kinase, heat-shock protein 27, inhibitor of nuclear factor κß, transforming growth factor beta-activated kinase 1 and survivin proteins. CONCLUSION: Taken together, our results suggest that activation of the mitochondrial apoptotic pathway may be a potential mechanism of EFA-CLA action.

Antitumor Properties of CLA-Enriched Food Products.

In this manuscript, we reviewed the available literature on the effects of conjugated linoleic acid (CLA)-enriched food products, including meat, dairy products, and eggs on cancer, both in vivo and in vitro. Based on our own studies on CLA-enriched eggs, we also identified potential molecular mechanisms by which such products may act on cancer cells. We propose the mitochondrial apoptosis pathway as mainly accountable for the reduction of cancer cells viability. Our hypothesis is supported by observed changes in expression of genes associated with downregulation of AKT/mTOR signalling pathway. In addition, we propose that CLA-enriched food products can act as peroxisome proliferator-activated receptors (PPAR) ligands showing predominately an agonist effect on PPAR isoforms.

Fatty Acids of CLA-Enriched Egg Yolks Can Induce Transcriptional Activation of Peroxisome Proliferator-Activated Receptors in MCF-7 Breast Cancer Cells.

In our previous study, we showed that fatty acids from CLA-enriched egg yolks (EFA-CLA) reduced the proliferation of breast cancer cells; however, the molecular mechanisms of their action remain unknown. In the current study, we used MCF-7 breast cancer cell line to determine the effect of EFA-CLA, as potential ligands for peroxisome proliferator-activated receptors (PPARs), on identified in silico PPAR-responsive genes: BCAR3, TCF20, WT1, ZNF621, and THRB (transcript TRß2). Our results showed that EFA-CLA act as PPAR ligands with agonistic activity for all PPAR isoforms, with the highest specificity towards PPARγ. In conclusion, we propose that EFA-CLA-mediated regulation of PPAR-responsive genes is most likely facilitated by cis9,trans11CLA isomer incorporated in egg yolk. Notably, EFA-CLA activated PPAR more efficiently than nonenriched FA as well as synthetic CLA isomers. We also propose that this regulation, at least in part, can be responsible for the observed reduction in the proliferation of MCF-7 cells treated with EFA-CLA.

Fatty acid extract from CLA-enriched egg yolks can mediate transcriptome reprogramming of MCF-7 cancer cells to prevent their growth and proliferation.

BACKGROUND: Our previous study showed that fatty acids extract obtained from CLA-enriched egg yolks (EFA-CLA) suppressed the viability of MCF-7 cancer cell line more effectively than extract from non-enriched egg yolks (EFA). In this study, we analysed the effect of EFA-CLA and EFA on transcriptome profile of MCF-7 cells by applying the whole Human Genome Microarray technology. RESULTS: We found that EFA-CLA and EFA treated cells differentially regulated genes involved in cancer development and progression. EFA-CLA, compared to EFA, positively increased the mRNA expression of TSC2 and PTEN tumor suppressors as well as decreased the expression of NOTCH1, AGPS, GNA12, STAT3, UCP2, HIGD2A, HIF1A, PPKAR1A oncogenes. CONCLUSIONS: We show for the first time that EFA-CLA can regulate genes engaged in AKT/mTOR pathway and inhibiting cell cycle progression. The observed results are most likely achieved by the combined effect of both: incorporated CLA isomers and other fatty acids in eggs organically modified through hens' diet. Our results suggest that CLA-enriched eggs could be easily available food products with a potential of a cancer chemopreventive agent.

Erratum to: Fatty acid extract from CLA-enriched egg yolks can mediate transcriptome reprogramming of MCF-7 cancer cells to prevent their growth and proliferation.

[This corrects the article DOI: 10.1186/s12263-016-0537-z.].

Fenofibrate Induces Ketone Body Production in Melanoma and Glioblastoma Cells.

Ketone bodies [beta-hydroxybutyrate (bHB) and acetoacetate] are mainly produced in the liver during prolonged fasting or starvation. bHB is a very efficient energy substrate for sustaining ATP production in peripheral tissues; importantly, its consumption is preferred over glucose. However, the majority of malignant cells, particularly cancer cells of neuroectodermal origin such as glioblastoma, are not able to use ketone bodies as a source of energy. Here, we report a novel observation that fenofibrate, a synthetic peroxisome proliferator-activated receptor alpha (PPARa) agonist, induces bHB production in melanoma and glioblastoma cells, as well as in neurospheres composed of non-transformed cells. Unexpectedly, this effect is not dependent on PPARa activity or its expression level. The fenofibrate-induced ketogenesis is accompanied by growth arrest and downregulation of transketolase, but the NADP/NADPH and GSH/GSSG ratios remain unaffected. Our results reveal a new, intriguing aspect of cancer cell biology and highlight the benefits of fenofibrate as a supplement to both canonical and dietary (ketogenic) therapeutic approaches against glioblastoma.