Cis-9,trans-11-conjugated linoleic acid affects lipid raft composition and sensitizes human colorectal adenocarcinoma HT-29 cells to X-radiation |
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Authors: | Iwona Grądzka,Barbara Sochanowicz,Kamil Brzó ska,Grzegorz Wó jciuk,Sylwester Sommer,Maria Wojewó dzka,Anna Gasińska,Christian Degen,Gerhard Jahreis,Irena Szumiel |
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Affiliation: | 1. Centre for Radiobiology and Biological Dosimetry, Institute of Nuclear Chemistry and Technology, Dorodna 16, 03–195 Warsaw, Poland;2. Department of Applied Radiobiology, Centre of Oncology, Garncarska 11, 31–115 Cracow, Poland;3. Institute of Nutrition, Friedrich Schiller University, Dornburger Str. 24, D-07743 Jena, Germany |
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Abstract: | BackgroundInvestigations concerned the mechanism of HT-29 cells radiosensitization by cis-9,trans-11-conjugated linoleic acid (c9,t11-CLA), a natural component of human diet with proven antitumor activity.MethodsThe cells were incubated for 24 h with 70 μM c9,t11-CLA and then X-irradiated. The following methods were used: gas chromatography (incorporation of the CLA isomer), flow cytometry (cell cycle), cloning (survival), Western blotting (protein distribution in membrane fractions), and pulse-field gel electrophoresis (rejoining of DNA double-strand breaks). In parallel, DNA-PK activity, γ-H2AX foci numbers and chromatid fragmentation were estimated. Gene expression was analysed by RT-PCR and chromosomal aberrations by the mFISH method. Nuclear accumulation of the EGF receptor (EGFR) was monitored by ELISA.Results and conclusionsC9,t11-CLA sensitized HT-29 cells to X-radiation. This effect was not due to changes in cell cycle progression or DNA-repair-related gene expression. Post-irradiation DSB rejoining was delayed, corresponding with the insufficient DNA-PK activation, although chromosomal aberration frequencies did not increase. Distributions of cholesterol and caveolin-1 in cellular membrane fractions changed. The nuclear EGFR translocation, necessary to increase the DNA-PK activity in response to oxidative stress, was blocked. We suppose that c9,t11-CLA modified the membrane structure, thus disturbing the intracellular EGFR transport and the EGFR-dependent pro-survival signalling, both functionally associated with lipid raft properties.General SignificanceThe results point to the importance of the cell membrane interactions with the nucleus after injury inflicted by X -rays. Compounds like c9,t11-CLA, that specifically alter membrane properties, could be used to develop new anticancer strategies. |
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Keywords: | CLA, conjugated linoleic acid(s) DNA-PK, DNA-dependent protein kinase DSB, DNA double-strand break EGFR, epidermal growth factor receptor FAME, fatty acid methyl ester(s) GC, gas chromatography LA, linoleic acid mFISH, multicolour fluorescence in situ hybridization MUFA, monounsaturated fatty acid(s), non-esterified fatty acids PCC, premature chromosome condensation PFGE, pulse-field gel electrophoresis PL, phospholipid(s) RT-PCR, real-time polymerase chain reaction SFA, saturated fatty acid(s) TAG, triacylglycerol(s) TLC, thin-layer chromatography |
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