title: Overexpression of Dickkopf-3 induces apoptosis through mitochondrial pathway in human colon cancer.
abstract: OBJECTIVE
  To investigate the mechanisms of the biological roles of Dickkopf-3 (Dkk-3) in cell invasion, survival and apoptosis in colon cancer cells.
  
  
  METHODS
  Three human colon cancer cell lines, i.e., HT-29, LoVo and SW480, were used. Overexpression of Dkk-3 induced by pEGFP-N1-Dkk-3-GFP plasmid in LoVo cells was performed using Lipofectamine 2000 reagent. Reverse transcription polymerase chain reaction and Western blotting were performed to determine the mRNA and protein expression levels of Dkk-3, respectively. Cell proliferation assay, cell cycle analysis, hoechst 33258 assay and Matrigel invasion assay were performed on Dkk-3 overexpressing transfectants.
  
  
  RESULTS
  The mRNA and protein expressions of Dkk-3 in HT-29 (mRNA: 0.06 ± 0.02, protein: 0.06 ± 0.01) and LoVo (mRNA: 0.07 ± 0.02, protein: 0.07 ± 0.02) cells were significantly lower than that in SW480 cells (mRNA: 0.92 ± 0.04, protein: 0.69 ± 0.13; all P < 0.05), and the greatest levels of invasiveness was in LoVo cells. Dkk-3 overexpression inhibited the proliferation and invasion of LoVo cells and induced cell cycle arrest at G(0)/G(1) phase and subsequent apoptosis, as indicated by increased chromatin condensation and fragments, upregulated Bax and cytochrome c protein, downregulated survivin and Bcl-2 protein, and the activation of caspase-3 and caspase-9. Furthermore, Dkk-3 overexpression reduced the accumulation of cytosolic fraction of β-catenin.
  
  
  CONCLUSIONS
  Dkk-3 overexpression induced apoptosis in human colon cancer possibly through the mitochondrial pathway. Dkk-3 may be involved in the Wnt/β-catenin signaling pathways in colon cancer.
authors.affiliation: Department of Gastroenterology, Renmin Hospital of Wuhan University, Wuhan 430060, Hubei Province, China.
authors.forename: Zi-Rong
authors.initials: ZR
authors.lastname: Yang
authors.forename: Wei-Guo
authors.initials: WG
authors.lastname: Dong
authors.forename: Xiao-Fei
authors.initials: XF
authors.lastname: Lei
authors.forename: Meng
authors.initials: M
authors.lastname: Liu
authors.forename: Qi-Sheng
authors.initials: QS
authors.lastname: Liu
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000230:Adenocarcinoma / Q000378:metabolism*; D017209:Apoptosis / Q000502:physiology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D018925:Chemokines; D003110:Colonic Neoplasms / Q000378:metabolism*; D059585:G1 Phase Cell Cycle Checkpoints / Q000502:physiology; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D019073:HT29 Cells; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis*; D060449:Wnt Signaling Pathway / Q000502:physiology; D051176:beta Catenin / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018925:Chemokines; C498624:DKK3 protein, human; D036341:Intercellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D051176:beta Catenin