Binding was due to TCF-4, as GST alone did not bind to the radioactively end-labeled TBE3-DNA probe (Fig.?2C, lane 7). in some tumor cells mostly at the invasive front of CRC25 and thereby reflects the expression pattern of -catenin.26 UR 1102 Additionally, the gene might be directly regulated by -catenin. This hypothesis was additionally supported by the finding that the gene contains at least one TCF-4 binding site.28 Here, we show evidence that is another direct target gene of -catenin, and that therefore the UR 1102 hallmark eternal life is directly controlled by -catenin in human colorectal cancer. During the preparation of this manuscript, the relationship of hTERT and -catenin was also exhibited in embryonic and adult stem cells as well as in colorectal cancer cell lines.29 Results hTERT and -catenin are coexpressed at the invasive front of human colorectal cancers Many CRCs are characterized by an invasive front with tumor cells displaying -catenin. These tumor cells also express -catenin target genes.26,30 Therefore, invasive fronts of such CRCs are a useful screening tool for the UR 1102 identification of -catenin target genes in human colorectal cancers. Moreover, it had already been shown that hTERT is usually expressed at the invasive front of CRC.25 But, no relation with the nuclear localization of -catenin is known. Therefore, we investigated if nuclear -catenin and hTERT displayed overlapping expression patterns employing serial histological sections of 24 human CRC with invasive fronts expressing nuclear -catenin. It turned out that tumor cells with nuclear -catenin (Fig.?1A) also strongly expressed hTERT (Fig.?1B). In contrast, tumor cells lacking nuclear -catenin (Fig.?1C) did not TLR4 display hTERT expression (Fig.?1D). Thus, it was affordable to argue that -catenin might be involved in the regulation of hTERT. Open in a separate window Physique?1. Coexpression of -catenin and hTERT in tumor cells at the invasive front of colorectal tumors. (A) Tumor cells at the invasive front express nuclear -catenin (inset, black arrows) and display a mesenchymal differentiation. (B) Corresponding tumor cells also express hTERT (inset, white arrows). (C) Tumor cells in central areas of the tumor display poor or no expression of nuclear -catenin (inset). These cells are characterized by epithelial differentiation. (D) Corresponding tumor cells display poor or no hTERT expression (inset). At 200x magnification. The promoter/enhancer of the by -catenin is usually c-myc as it is usually on the one hand a target gene of -catenin9 and is known to regulate the transcription of the gene was detected.28 To investigate the transcriptional regulation of by -catenin/TCF-4 in more detail, we analyzed the promoter/enhancer region of the gene (accession number “type”:”entrez-nucleotide”,”attrs”:”text”:”AB016767″,”term_id”:”4239869″,”term_text”:”AB016767″AB016767) for the occurrence of consensus TBEs (WWCAAAG).28,32 Four TBEs were identified at positions -1,627 (TBE1), -2,149 (TBE2), -2,488 (TBE3) and -2,974 (TBE4), with respect to the transcription start (+1) of the gene. These four TBEs are embedded in binding elements for a variety of other transcription factors like AP2 (activation protein 2), MAD (MAX dimerization protein), c-Myc, MZF2 (myeloid zinc finger protein 2), SP1 (specificity protein 1) or WT1 (Wilms tumor 1-gene) (Fig.?2A).31 Thus, based on the composition of its UR 1102 promoter/enhancer region, the promoter/enhancer and confers transcriptional activation. (A) Schematic representation of the promoter/enhancer with four located consensus motif TBEs (TCF binding elements) and other known responsive elements: MZF2 (myeloid zinc finger protein 2), WT1 (Wilms tumor 1 gene), c-Myc/MAD1 (MAX dimerization protein 1), AP2 (activation protein 2) and SP1 (specificity protein 1). The arrows below the TBEs represent the orientation of the consensus sequence WWCAAAG. The sites of the EMSA-DNA probes and competitors as well as the binding site of primer used in the ChIP-assay are indicated. Physique is not drawn to scale. (B) The promoter/enhancer reporter gene.
Binding was due to TCF-4, as GST alone did not bind to the radioactively end-labeled TBE3-DNA probe (Fig