title: Cis-9,trans-11-conjugated linoleic acid affects lipid raft composition and sensitizes human colorectal adenocarcinoma HT-29 cells to X-radiation.
abstract: BACKGROUND
  Investigations 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.
  
  
  METHODS
  The cells were incubated for 24h with 70μM 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.
  
  
  CONCLUSIONS
  C9,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.
  
  
  CONCLUSIONS
  The 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.
authors.affiliation: Institute of Nuclear Chemistry and Technology, Warsaw, Poland. i.gradzka@ichtj.waw.pl
authors.forename: Iwona
authors.initials: I
authors.lastname: Grądzka
authors.forename: Barbara
authors.initials: B
authors.lastname: Sochanowicz
authors.forename: Kamil
authors.initials: K
authors.lastname: Brzóska
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Wójciuk
authors.forename: Sylwester
authors.initials: S
authors.lastname: Sommer
authors.forename: Maria
authors.initials: M
authors.lastname: Wojewódzka
authors.forename: Anna
authors.initials: A
authors.lastname: Gasińska
authors.forename: Christian
authors.initials: C
authors.lastname: Degen
authors.forename: Gerhard
authors.initials: G
authors.lastname: Jahreis
authors.forename: Irena
authors.initials: I
authors.lastname: Szumiel
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects / Q000528:radiation effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D044243:Linoleic Acids, Conjugated; D021962:Membrane Microdomains / Q000378:metabolism* / Q000473:pathology; D011836:Radiation Tolerance / Q000187:drug effects* / Q000528:radiation effects; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D014965:X-Rays
chemical_list: D044243:Linoleic Acids, Conjugated; D011838:Radiation-Sensitizing Agents; C503589:cis-9, trans-11-conjugated linoleic acid