title: Neutrophil gelatinase-associated lipocalin in gastric carcinoma cells and its induction by TPA are controlled by C/EBPβ.
abstract: Neutrophil gelatinase-associated lipocalin (NGAL) expression has been found to be upregulated in a variety of tumors, but the mechanism of NGAL elevation in gastric carcinoma remains unknown. Here, immunohistochemistry was applied to analyze NGAL expression in gastric carcinoma patients. Reverse transcription PCR, Western blot, and enzyme-linked immunosorbent assay (ELISA) were performed to evaluate NGAL mRNA and protein levels before and after 12-O-tetradecanoylphorbol-13-acetate (TPA) induction. Luciferase reporter assay was carried out to identify the core cis element in NGAL promoter. The binding ability and specificity of transcription factors were analyzed by electrophoretic mobility-shift assay (EMSA) and chromatin immunoprecipitation (ChIP), respectively. Results showed that NGAL was overexpressed in gastric tumor tissues. Gastric cancer cells treated with TPA resulted in the transactivation of NGAL promoter and the upregulation of its mRNA and protein levels. We identified the -110 to -79 sequence segment upstream from the transcription initiation site of NGAL as a TPA responsive element (TRE) and confirmed that C/EBPβ was able to bind to the -87 to -79 segment. Forced expression of C/EBPβ significantly increased the promoter activity of NGAL as well as its mRNA level. These results suggest that NGAL is overexpressed in gastric cancer, the binding of C/EBPβ to the TRE of its gene promoter mediates its TPA-induced overexpression in gastric carcinoma cells.
authors: Institute of Oncologic Pathology, Medical College of Shantou University, China.
authors: Ze-Peng
authors: ZP
authors: Du
authors: Hua-Min
authors: HM
authors: Yuan
authors: Bing-Li
authors: BL
authors: Wu
authors: Jing-Xia
authors: JX
authors: Chang
authors: Zhuo
authors: Z
authors: Lv
authors: Jian
authors: J
authors: Shen
authors: Jian-Yi
authors: JY
authors: Wu
authors: Hai-Bin
authors: HB
authors: Chen
authors: En-Min
authors: EM
authors: Li
authors: Li-Yan
authors: LY
authors: Xu