Regulation of the FABP7 gene by PAX6 in malignant glioma cells
ABSTRACT Brain fatty acid-binding protein (FABP7) and PAX6 are both expressed in radial glial cells and have been implicated in neurogenesis and glial cell differentiation. FABP7 and PAX6 have also been postulated to play a role in malignant glioma cell growth and invasion. Here, we address the role of PAX6 in regulating FABP7 gene expression in malignant glioma cells. We report that PAX6 and FABP7 RNA are generally co-expressed in malignant glioma cell lines, tumors and tumor neurospheres. Using the CAT reporter gene assay, we show that FABP7 promoter activity is upregulated by PAX6. Sequential deletion analysis of the FABP7 promoter, combined with gel shift and supershift assays demonstrate the presence of a PAX6 responsive region located upstream of the FABP7 gene, at -862 to -1033 bp. Inclusion of sequences between -1.2 and -1.8 kb reduced CAT activity, suggesting the presence of a repressor element within this region. While PAX6 overexpression did not induce endogenous FABP7 expression in FABP7-negative cells, knock-down of PAX6 in PAX6-positive malignant glioma cells resulted in reduced FABP7 levels. These data provide the first evidence of direct transactivation of the FABP7 proximal promoter by PAX6 and suggest a synergistic mechanism for PAX6 and other co-factor(s) in regulating FABP7 expression in malignant glioma.
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ABSTRACT: The purpose of this study is to review recent evidence for the role of the cytosolic fatty acid binding proteins (FABPs) as central regulators of whole-body metabolic control. Dysregulated FABPs have been associated with a number of diseases, including obesity and nonalcoholic fatty liver disease (FABP1, FABP2, FABP4), cardiovascular risk (FABP3) and cancer (FABP5, FABP7). As underlying mechanisms become better understood, FABPs may represent novel biomarkers for therapeutic targets. In addition, the role of FABPs as important signalling molecules has also been highlighted in recent years; for example, FABP3 may act as a myokine, matching whole-body metabolism to muscular energy demands and FABP4 functions as an adipokine in regulating macrophage and adipocyte interactions during inflammation. In addition to their traditional role as fatty acid trafficking proteins, increasing evidence supports the role of FABPs as important controllers of global metabolism, with their dysregulation being linked to a host of metabolic diseases.03/2014; 17(2):124-9. DOI:10.1097/MCO.0000000000000031
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ABSTRACT: Paired box 6 (PAX6), a highly conserved transcriptional factor, has been implicated in tumorigenesis. We aimed to explore the roles and molecular mechanisms of PAX6 and microRNA (miR-7) in colorectal cancer cells. Tissue microarray immunohistochemistry and Western blot were applied to examine the PAX6 expression. Real-time RT-PCR and Western blot were performed to determine the expression of miR-7 and PAX6. Luciferase reporter assay was used to determine whether PAX6 was a target of miR-7. Effects of miR-7 and PAX6 on colorectal cell proliferation, cell cycle progression, colony formation and invasion were then investigated. Western blot was used to determine the activities of the ERK and PI3K signal pathways, as well as the protein expression of MMP2 and MMP9. The protein levels of PAX6 were gradually increased, while the expression of miR-7 was gradually reduced with malignancy of colorectal cancer. PAX6 was further identified as a target of miR-7, and its protein expression was negatively regulated by miR-7 in human colorectal cancer cells. Overexpression of PAX6 in Caco-2 and SW480 cells enhanced cellular proliferation, cell cycle progression, colony formation, and invasion, while miR-7 upregulation repressed these biological processes. Furthermore, the activities of ERK and PI3K signal pathways, as well as the protein levels of MMP2 and MMP9, were upregulated in PAX6-overexpressed Caco-2 and SW480 cells but deregulated in miR-7-overexpressed Caco-2 and SW480 cells. Our study suggests that as a novel target of miR-7, PAX6 may serve as a promising therapeutic target for colorectal cancer.Digestive Diseases and Sciences 11/2013; DOI:10.1007/s10620-013-2929-x · 2.26 Impact Factor
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ABSTRACT: Paired box 6 (PAX6), a highly conserved transcription factor, is important in glioma. However, the molecular mechanisms involved remain unclear. The present study demonstrated that the expression of PAX6 was significantly reduced with the malignancy of glioma and also identified PAX6 as a novel target of microRNA (miR)‑335, which was significantly upregulated in glioma. The inhibition of miR‑335 increased the protein expression of PAX6, whereas the upregulation of miR‑335 suppressed its expression in human glioma U251 and U87 cells. Furthermore, upregulation of miR-335 promoted U251 cell proliferation, colony formation and invasion, which was reversed by the overexpression of PAX6. Furthermore, the present study demonstrated that the effect of miR‑335 on U251 cell invasion was via the modulation of matrix metalloproteinase (MMP)‑2 and MMP‑9 expression by targeting PAX6. In conclusion, the present study demonstrated that PAX6, as a novel target of miR‑335, has an anti‑oncogenic function in glioma, and thus PAX6 may serve as a therapeutic target for glioma.Molecular Medicine Reports 04/2014; 10(1). DOI:10.3892/mmr.2014.2150 · 1.48 Impact Factor