The purpose of the experiments proposed in this application is to further characterize genetic elements (cis-acting elements) and associated transcription factors (trans-acting factors) that are important for regulating the tissue specific expression of the human MUC1 gene. MUC1 protein is highly overexpressed and differentially glycosylated by different adenocarcinomas (including breast, pancreas, lung, prostate) and is a cell surface-associated mucin with a structure that is remarkably similar to some of the selectin ligands. The MUC1 protein probably plays a role in the biological properties of tumor progression, especially the process of metastasis. Thus, the discovery of mechanisms to modulate expression may help prevent metastatic spread of some adenocarcinomas. In addition, MUC1 is currently being investigated as a target antigen for different immunodiagnostic and immunotherapeutic protocols for diagnosing and treating these and other adenocarcinomas. It may be beneficial to upregulate expression of MUC1 on tumor cells during courses of immunotherapy, and to down-regulate expression of MUC1 on normal cell types in cases where autoinunune disease developed secondary to immunotherapy. In addition, identifying and characterizing the elements that control MUC1 expression may be useful for future gene therapy strategies. There are currently no promoter constructs that accurately control expression of genes in the secretory epithelial cell populations in which MUC1 is expressed (and adenocarcinomas derived from them). The proposed experimental design includes a novel approach to investigating promoter activity: They will utilize epitope-tagged products of the MUC1 gene and cDNA to measure levels of mRNA and protein expression. The epitope-tagged constructs provide them with the unique capability of monitoring levels of mRNA and protein expression. This experimental design circumvents some limitations of traditional reporter-promoter studies, in that it will allow the detection of the coding region of the gene i the proper context of sequence and chromatin structure. In addition, they will evaluate chromatin structure of this relatively compact gene by in vivo methods. The regulatory mechanisms that result in overexpression of MUC1 in tumors have not been established. One area they will investigate is activation of Signal Transducer and Activator of Transcription (STATs) factors. STATs are important because the MUC1 promoter contains a functional STAT3/STAT1 element that is responsive to IL-6, gamma- interferon and EGF. Glucocorticoids may cooperate synergistically with Il-6 and insulin in this system and there is evidence for a direct interaction between the glucocorticoid receptor (GR) and STAT3. In addition, activated GR can stimulate the basal activity of the MUC1 promoter independently of STAT3. STAT3 has been shown to be upregulated in breast cancer cells relative to normal breast epithelial cells.
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| Shiraga, Toshiyuki; Smith, David; Nuthall, Hugh N et al. (2002) Identification of two novel elements involved in human MUCI gene expression in vivo. Mol Med 8:33-41 |
| Parry, S; Silverman, H S; McDermott, K et al. (2001) Identification of MUC1 proteolytic cleavage sites in vivo. Biochem Biophys Res Commun 283:715-20 |
| Gaemers, I C; Vos, H L; Volders, H H et al. (2001) A stat-responsive element in the promoter of the episialin/MUC1 gene is involved in its overexpression in carcinoma cells. J Biol Chem 276:6191-9 |
