Identification of a Novel PGE₂ Regulated Gene in SNU1 Gastric Cancer Cell

Prostaglandin E₂ (PGE₂) plays an important role in the regulation of various gastric functions, and the growth-inhibitory activities on tumor cells are studied in vitro and in vivo. Although the mechanisms have attracted many researchers in the past decade, the molecular mechanisms of cell cycle arrest, or induction of apoptosis by PGE₂, is unclear. We investigated the effects of PGE₂ on the growth of the human gastric carcinoma cell line SNU1 and genes that are regulated by PGE₂ and isolated them using differential display RT-PCR (DD RT-PCR). FACS analysis suggested that SNU1 cells were arrested at the G1 phase by PGE₂ treatment. This growth inhibitory effect was in a time- and dose-dependent manner. Treatment of SNU1 cells with 10 μg/ml PGE₂, followed by DD RT-PCR analysis, revealed differently expressed bands patterns from the control. Among the differently expressed clones, we found an unidentified cDNA clone (HGP-27) overexpressed in PGE₂-treated cells. The full-length cDNA of HGP-27 was isolated using RACE, which consisted of a 30-nt 5′-noncoding region, a 891-nt ORF encoding the 296 amino acid protein, and a 738-nt 3′-noncoding region including a poly(a) signal. This gene was localized on the short arm of chromosome number 11. Using the MotifFinder program, a myb-DNA binding repeat signature was detected on the ORF region. The COOH-terminal half was shown to have similarity with the NH₃-terminal domain of thioredoxin (Trx). This relation between HGP-27 and Trx implied a potential role for HGP-27 in modulating the DNA binding function of a transcription factor, myb.