Original Article
Copyright ©2011 Baishideng Publishing Group Co., Limited. All rights reserved.
World J Gastroenterol. Sep 7, 2011; 17(33): 3810-3817
Published online Sep 7, 2011. doi: 10.3748/wjg.v17.i33.3810
Dickkopf3 overexpression inhibits pancreatic cancer cell growth in vitro
Yu-Mei Gu, Yi-Hui Ma, Wu-Gan Zhao, Jie Chen
Yu-Mei Gu, Yi-Hui Ma, Wu-Gan Zhao, Jie Chen, Department of Pathology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, China
Author contributions: Chen J and Gu YM designed the research; Gu YM, Ma YH and Zhao WG performed the research and analyzed the data; Gu YM and Chen J wrote the paper.
Supported by National Natural Science Foundation of China, No. 30471970; National Science and Technology Support Project (the 11th Five-Year Plan) of China, No. 2006BAI02A14; Scientific Research Special Projects of Health Ministry of China, No. 200802011 and National Data Sharing Project in Human Health, No. 2005DKA32403
Correspondence to: Jie Chen, Professor, Department of Pathology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, China. xhblk@163.com
Telephone: +86-10-65295490 Fax: +86-10-65295490
Received: February 17, 2011
Revised: April 13, 2011
Accepted: April 20, 2011
Published online: September 7, 2011

AIM: To elucidate the role of dickkopf3 (Dkk3) in human pancreatic cancer cell growth.

METHODS: Dkk3 mRNA and protein expression in human pancreatic cancer cell lines were detected by real-time reverse transcription polymerase chain reaction (real-time RT-PCR), Western blotting and immunofluorescence. Methylation of the Dkk3 promoter sequence was examined by methylation-specific polymerase chain reaction (MSP) and Dkk3 mRNA expression was determined by real-time RT-PCR after 5-aza-2’-deoxycytidine (5-aza-dC) treatment. The effects of Dkk3 on cancer cell proliferation and in vitro sensitivity to gemcitabine were investigated by CellTiter 96® AQueous One Solution Cell Proliferation Assay (MTS) after transfecting the Dkk3 expression plasmid into human pancreatic cancer cells. The expression of β-catenin, phosphorylated extracellular signal-regulated protein kinases (pERK) and extracellular signal-regulated protein kinases (ERK) was also examined by real-time RT-PCR and Western blotting after upregulating Dkk3 expression in human pancreatic cancer cells.

RESULTS: The results show that the expression levels of both Dkk3 mRNA and protein were low in all pancreatic cancer cell lines tested. The Dkk3 promoter sequence was methylated in the MIA PaCa-2 and AsPC-1 cell lines, which showed reduced Dkk3 expression. These two cell lines, which initially had a methylated Dkk3 promoter, showed increased Dkk3 mRNA expression that was dependent upon the dosage and timing of the DNA demethylating agent, 5-aza-dC, treatment (P < 0.05 or P < 0.01). When Dkk3 expression was upregulated following the transfection of a Dkk3 expression plasmid into MIA PaCa-2 cells, the ability of cells to proliferate decreased (P < 0.01), and the expression of β-catenin and pERK was downregulated (P < 0.01). Sensitivity to gemcitabine was enhanced in Dkk3 expression plasmid-transfected cells.

CONCLUSION: Our findings, for the first time, implicate Dkk3 as a tumor suppressor in human pancreatic cancer, through the downregulation of β-catenin expression via the ERK-mediated pathway.

Keywords: Cell growth, Dickkopf3, In vitro, Overexpression, Pancreatic cancer