title: Activation of caspase-8 contributes to 3,3'-Diindolylmethane-induced apoptosis in colon cancer cells.
abstract: 3,3'-Diindolylmethane (DIM) is the major in vivo product of acid-catalyzed oligomerization of indole-3-carbinol, which is a promising anticancer agent present in cruciferous vegetables and has itself been reported to have anticarcinogenic properties. This study examined DIM-mediated regulation of apoptosis in the HCT116 (wild-type p53) and HT-29 (mutant p53) human colon cancer cell lines. DIM (0-30 micromol/L) substantially decreased the number of viable cells and induced apoptosis of HCT116 and HT-29 cells in a concentration-dependent manner. Western-blot analyses of total cell lysates revealed that DIM increased the activation of caspase-3, -7, -8, and -9 and enhanced poly(ADP-ribose) polymerase cleavage in both HCT116 and HT-29 cells. In addition, DIM increased the translocation of cytochrome c and Smac/Diablo from the mitochondria to the cytoplasm. In concert with the caspase-8 activation by DIM, increased levels of Fas and truncated Bid were observed. DIM did not affect the protein levels of p53, Bcl-2, Bax, or Fas ligand (FasL) in HCT116 cells. In HT-29 cells, however, DIM decreased Bcl-2 levels, although the protein levels of Bax or FasL were not affected. The caspase-8 inhibitor Z-IETD-FMK attenuated the DIM-induced apoptosis, indicating that increased activation of this enzyme contributed to the increase in p53-independent apoptosis that was observed in colon cancer cells. We have demonstrated that DIM induces apoptosis in colon cancer cells, providing insights into the mechanisms underlying its antitumorigenic activities.
authors.affiliation: Center for Efficacy Assessment and Development of Functional Foods and Drugs, Hallym University, Chuncheon, 200-702, Korea.
authors.forename: Eun Ji
authors.initials: EJ
authors.lastname: Kim
authors.forename: So Young
authors.initials: SY
authors.lastname: Park
authors.forename: Hyun-Kyung
authors.initials: HK
authors.lastname: Shin
authors.forename: Dae Young
authors.initials: DY
authors.lastname: Kwon
authors.forename: Young-Joon
authors.initials: YJ
authors.lastname: Surh
authors.forename: Jung Han Yoon
authors.initials: JH
authors.lastname: Park
mesh_terms: D000818:Animals; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D053181:Caspase 8 / Q000378:metabolism*; D002460:Cell Line; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000201:enzymology / Q000473:pathology*; D004789:Enzyme Activation; D005434:Flow Cytometry; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D051381:Rats
chemical_list: D016588:Anticarcinogenic Agents; D007211:Indoles; D053181:Caspase 8; C016392:3,3'-diindolylmethane