title: Chronic but not acute conjugated linoleic acid treatment inhibits deoxycholic acid-induced protein kinase C and nuclear factor-kappaB activation in human colorectal cancer cells.
abstract: Conjugated linoleic acid (CLA) has anti-carcinogenic effects in a variety of cancers including colon cancer. Secondary bile acids on the other hand are known as tumour promoters in colon cancer with effects on protein kinase C (PKC) and nuclear factor kappa B (NF-kappaB) signalling pathways. The aim of this study was to examine acute and chronic, isomer-specific effects of CLA on bile salt-induced PKC and NF-kappaB signal transduction in human colon cancer cells. HCT116 cells were treated with 100 mumol/l and 50 mumol/l cis-9,trans-11-CLA and trans-10,cis-12-CLA for 24 h and 14 days, respectively. The cells were then transfected with DNA coding for PKC beta1-EGFP (enhanced green fluorescent protein), PKC delta-EGFP or PKC zeta-EGFP fusion protein and activated with deoxycholic acid (DCA), phorbol myristate acetate (PMA) or C2-ceramide. PKC translocation was observed using real-time photomicroscopy and fluorescent microscopy and NF-kappaB analyses by gel shift assays. Chronic c-9,t-11-CLA and t-10,c-12-CLA treatment inhibited DCA-induced PKC beta1 and PKC delta translocation and also inhibited NF-kappaB activation. Acute CLA treatment had no effect on PKC or NF-kappaB activation. In conclusion this study indicates that chronic CLA treatment inhibits DCA-induced PKC and NF-kappaB activation in colon cancer cells. These data suggest mechanisms by which CLA may influence the course of colonic cancer.
authors.affiliation: Montagu Hospital, Mexborough, UK. syed.shah@doctors.org.uk
authors.forename: Syed A
authors.initials: SA
authors.lastname: Shah
authors.forename: Nasir
authors.initials: N
authors.lastname: Mahmud
authors.forename: Mohamed
authors.initials: M
authors.lastname: Mftah
authors.forename: Helen M
authors.initials: HM
authors.lastname: Roche
authors.forename: Dermot
authors.initials: D
authors.lastname: Kelleher
mesh_terms: D015179:Colorectal Neoplasms; D003840:Deoxycholic Acid / Q000037:antagonists & inhibitors*; D024202:Electrophoretic Mobility Shift Assay; D049452:Green Fluorescent Proteins / Q000235:genetics; D045325:HCT116 Cells; D006801:Humans; D044243:Linoleic Acids, Conjugated / Q000494:pharmacology*; D016328:NF-kappa B / Q000378:metabolism*; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D064546:Protein Kinase C beta; D051745:Protein Kinase C-delta; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate; D014162:Transfection
chemical_list: D044243:Linoleic Acids, Conjugated; D016328:NF-kappa B; C485184:enhanced green fluorescent protein; C496197:trans-10,cis-12-conjugated linoleic acid; D003840:Deoxycholic Acid; D049452:Green Fluorescent Proteins; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D051745:Protein Kinase C-delta; D013755:Tetradecanoylphorbol Acetate