Abstract 1981: Interference of the polyphenolic compound curcumin with expression regulation of target genes of the PLAG1 oncogenic transcription factor

Abstract

Abstract Transcriptional upregulation of a variety of signaling genes is a key feature of PLAG1-induced tumorigenesis. The PLAG1 gene is mainly expressed during embryogenesis and mobilization of its oncogenic potential in human tumors results from genetic aberrations. The oncogenic capacity of the PLAG1 gene was initially demonstrated by various standard experimental approaches in vitro. The oncogenic potential of the PLAG1 gene was further demonstrated by the generation of a versatile tumor mouse model system with Cre-mediated expression activation of the PLAG1 gene. In previous studies, it was demonstrated that the PLAG1-encoded protein is a genuine transcription factor, which recognizes a specific bipartite DNA sequence motif and activates a variety of target genes among which genes of the Igf and Wnt signaling pathways. In an attempt to interfere with the oncogenic PLAG1 transcription factor, the possible effect of a variety of natural products including various polyphenols was studied. Initially, PLAG1 transduced Balb/c-3T3 expressing high levels of PLAG1 were screened for the possible effect of a variety of polyphenols on the PLAG1-induced upregulation of various established PLAG1 target genes such as for instance Igf2. The polyphenolic compound curcumin was selected for further studies since, in the initial experiments, it was shown to exhibit downregulation of Igf2 expression as well as that of other well-established PLAG1 target genes such as H19, Dlk1, and Gtl2. Evaluation of the expression of various genes which lack the PLAG1-specific bipartite DNA binding motif in their promoter regions revealed no effect of curcumin; e.g. Plag1, Wnt6 and Ctnnb1. The observation that preferentially the expression of PLAG1 target genes was affected by curcumin raised the possibility that curcumin might interfere with the binding of the PLAG1 transcription factor to its specific DNA binding sites in the promoter regions of the tested PLAG1 target genes. To test this hypothesis, the effect of curcumin on the expression of two reporter gene constructs was studied. These reporter constructs consisted of the luciferase gene under expression control of a HSK-tk promoter with either three wild-type PLAG1-specific DNA binding motifs or, as a control, three mutated forms of it upstream of HSV-tk. The results of these experiments suggested that curcumin indeed might interfere directly with the binding of the PLAG1 transcription factor protein to its cognate DNA binding motif. To further substantiate these results in an independent way, EMSA experiments are being performed. Altogether, the results of these studies seem to favor the notion that curcumin could directly affect the PLAG1-induced tumorigenic process in vivo by interfering with the binding of the PLAG1 transcription factor to its cognate binding sites in promoter regions of target genes. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1981. doi:1538-7445.AM2012-1981