title: Cannabinoid receptor activation induces apoptosis through tumor necrosis factor alpha-mediated ceramide de novo synthesis in colon cancer cells.
abstract: OBJECTIVE
  Cannabinoids have been recently proposed as a new family of potential antitumor agents. The present study was undertaken to investigate the expression of the two cannabinoid receptors, CB1 and CB2, in colorectal cancer and to provide new insight into the molecular pathways underlying the apoptotic activity induced by their activation.
  
  
  METHODS
  Cannabinoid receptor expression was investigated in both human cancer specimens and in the DLD-1 and HT29 colon cancer cell lines. The effects of the CB1 agonist arachinodyl-2'-chloroethylamide and the CB2 agonist N-cyclopentyl-7-methyl-1-(2-morpholin-4-ylethyl)-1,8-naphthyridin-4(1H)-on-3-carboxamide (CB13) on tumor cell apoptosis and ceramide and tumor necrosis factor (TNF)-alpha production were evaluated. The knockdown of TNF-alpha mRNA was obtained with the use of selective small interfering RNA.
  
  
  RESULTS
  We show that the CB1 receptor was mainly expressed in human normal colonic epithelium whereas tumor tissue was strongly positive for the CB2 receptor. The activation of the CB1 and, more efficiently, of the CB2 receptors induced apoptosis and increased ceramide levels in the DLD-1 and HT29 cells. Apoptosis was prevented by the pharmacologic inhibition of ceramide de novo synthesis. The CB2 agonist CB13 also reduced the growth of DLD-1 cells in a mouse model of colon cancer. The knockdown of TNF-alpha mRNA abrogated the ceramide increase and, therefore, the apoptotic effect induced by cannabinoid receptor activation.
  
  
  CONCLUSIONS
  The present study shows that either CB1 or CB2 receptor activation induces apoptosis through ceramide de novo synthesis in colon cancer cells. Our data unveiled, for the first time, that TNF-alpha acts as a link between cannabinoid receptor activation and ceramide production.
authors.affiliation: Department of Medical and Surgical Critical Care, University of Florence, Florence, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Cianchi
authors.forename: Laura
authors.initials: L
authors.lastname: Papucci
authors.forename: Nicola
authors.initials: N
authors.lastname: Schiavone
authors.forename: Matteo
authors.initials: M
authors.lastname: Lulli
authors.forename: Lucia
authors.initials: L
authors.lastname: Magnelli
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Vinci
authors.forename: Luca
authors.initials: L
authors.lastname: Messerini
authors.forename: Clementina
authors.initials: C
authors.lastname: Manera
authors.forename: Elisa
authors.initials: E
authors.lastname: Ronconi
authors.forename: Paola
authors.initials: P
authors.lastname: Romagnani
authors.forename: Martino
authors.initials: M
authors.lastname: Donnini
authors.forename: Giuliano
authors.initials: G
authors.lastname: Perigli
authors.forename: Giacomo
authors.initials: G
authors.lastname: Trallori
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Tanganelli
authors.forename: Sergio
authors.initials: S
authors.lastname: Capaccioli
authors.forename: Emanuela
authors.initials: E
authors.lastname: Masini
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002518:Ceramides / Q000096:biosynthesis*; D003110:Colonic Neoplasms / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D008819:Mice, Nude; D034741:RNA, Small Interfering; D043884:Receptor, Cannabinoid, CB1 / Q000378:metabolism*; D043885:Receptor, Cannabinoid, CB2 / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
chemical_list: D002518:Ceramides; D034741:RNA, Small Interfering; D043884:Receptor, Cannabinoid, CB1; D043885:Receptor, Cannabinoid, CB2; D014409:Tumor Necrosis Factor-alpha