The role of ATBF1 nuclear translocation in gastric and intestinal phenotype and chemosensitivity of gastric cancer

点击翻译按钮获取中文摘要

Background and aims: MUC5AC belongs to the family of secreted mucins and expresses in foveolar cells of the stomach. Alterations of mucin expression take place in gastric cancer. It was reported that MUC5AC expression in gastric cancer correlates with poor prognosis. However, the transcriptional regulation mechanism of MUC5AC has not been well elucidated. AT motif binding factor 1 (ATBF1) is a homeotic transcription factor which negatively regulates Alpha-fetoprotein (AFP) and oncoprotein Myb. We have showed previously that ATBF1 negatively regulates transcription of brush-border enzyme gene, aminopeptidase-N and that the absence of ATBF1 is a distinct feature of AFP-producing gastric cancer cells, which are characterized by extremely high malignancy (Oncogene 2001). ATBF1 has recently been identified as a candidate of tumor suppressor for prostate cancer (Nat. Genet. 2005). In this study, we investigated the transcriptional regulation of MUC5AC by ATBF1.Materials and Methods: 1. We an … More alyzed ATBF1 and MUC5AC expression by immunohistochemistry in 123 area of 41 gastric cancers specimen. 2. We analyzed whether there is an AT motif in MUC5AC promoter region or not. 3. To analyze the transcriptional regulation of MUC5AC by ATBF1, we performed transient transfection and dual luciferase-reporter assay in MKN45 cells (gastric cancer cells). 4. To analyze the transcriptional regulation of MUC5AC by ATBF1 in protein level, we examined the protein expression of MUC5AC in MKN45 cells which was overexpressed ATBF1 using confocal microscopy. 5. To assess the binding of ATBF1 to the AT motif in MUC5AC promoter region, we performed chromatin immunoprecipitation (ChIP).Results: 1. Only 9% (3/33) of ATBF1-positive(nuclear staining) gastric cancers were MUC5AC positive, and, 76% (68/90) of ATBF1-negative (cytoplasm staining or no staining )gastric cancers were MUC5AC positive. ATBF1 nuclear staining tends to be observed in gastric cancer cells negative for MUC5AC (p<.0001). 2. We detected the AT motif in MUC5AC promoter region (-1646-1634). 3. Transient transfection and dual luciferase-reporter assay demonstrated that ATBF1 suppressed the activity of MUC5AC promoter (35 plus minus 1.1%). 4. 70. 7 plus minus 1.2% of MKN45 cells transfected with control were MUC5AC positice, however only 11.3 plus minus 3.1% of MKN45 cells transfected with ATBF1 were MUC5AC positive (p<.0001). Overexpressed ATBF1 suppressed MUC5AC endogeneous protein in gastric cancer cells. 5. ChIP revealed that ATBF1 binds AT motif of MUC5AC promoter.Conclusion: ATBF1 binds to AT motif of MUC5AC promoter and negatively regulates transcription of the MUC5AC gene in gastric cancer. Less