Activation of caspase-8 contributes to 3,3'-Diindolylmethane-induced apoptosis in colon cancer cells.
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.
Kim
Eun Ji
EJ
Center for Efficacy Assessment and Development of Functional Foods and Drugs, Hallym University, Chuncheon, 200-702, Korea.
Park
So Young
SY
Shin
Hyun-Kyung
HK
Kwon
Dae Young
DY
Surh
Young-Joon
YJ
Park
Jung Han Yoon
JH
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
D016588:Anticarcinogenic Agents; D007211:Indoles; D053181:Caspase 8; C016392:3,3'-diindolylmethane