Carcinogenesis Advance Access originally published online on January 3, 2008
Carcinogenesis 2008 29(6):1219-1227; doi:10.1093/carcin/bgm297
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Expression of 15-PGDH is downregulated by COX-2 in gastric cancer
State key Laboratory of Cancer Biology and Institute of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, 15 Changle West Road, Shaanxi Province, Xi'an 710032, China
* To whom correspondence should be addressed. Tel: +86 29 84775221; Fax: +86 29 82539041; Email: kaicwu{at}fmmu.edu.cn
To explore the proteins regulated by cyclooxygenase-2 (COX-2) in gastric cancer, the expression plasmid of COX-2siRNA was constructed and transfected into gastric cancer cell line SGC7901. Then, two-dimensional electrophoresis and the PDQuest software analysis were applied to discover the differentially expressed proteins. The differential protein spots were analyzed by matrix-assisted laser desorption/ionization time of flight mass spectrometry. Fourteen differentially expressed proteins between the two cell lines were identified. 15-Hydroxyprostaglandin dehydrogenase [NAD+] (15-PGDH), a key enzyme in prostaglandin degradation, was identified as an upregulated protein in SGC7901 cells transfected with the COX-2siRNA plasmid. To further explore whether the 15-PGDH is regulated by COX-2, western blotting and immunocytochemical assay were performed to detect the expression of 15-PGDH in different cell lines with different expression level of COX-2. The results showed that the expression of 15-PGDH was upregulated (128.57%) as COX-2 was suppressed by small interfering RNA and downregulated (51.72%) as COX-2 was enhanced by COX-2 cDNA transfection in gastric cancer cells. In tissue specimens with gastric cancer, there was a decreased expression of 15-PGDH and an increased expression of COX-2 simultaneously. A significantly negative correlation of 15-PGDH expression was found to COX-2 level, tumor differentiation, tumor, lymph node, metastasis (TNM) staging and lymph node metastasis of gastric cancer. All the results suggest that 15-PGDH is downregulated by COX-2 in human gastric cancer and may contribute to the carcinogenesis and development of human gastric cancer in combination with COX-2.
Abbreviations: COX-2, cyclooxygenase-2; DTT, dithiothreitol; 2-DE, two-dimensional electrophoresis; IEF, isoelectric focusing; IPG, immobilized pH gradient; MALDI-TOF MS, matrix-assisted laser desorption/ionization time of flight mass spectrometry; 15-PGDH, 15-hydroxyprostaglandin dehydrogenase [NAD+]; siRNA, small interfering RNA; TNM, tumor, lymph node, metastasis
These authors contributed equally to this work. Received September 15, 2007; revised December 16, 2007; accepted December 17, 2007.