The intermediate filament gene family, composed of six classes, shows both tissue and development-specific expression. Vimentin is a unique member of the intermediate filament protein family: although it is expressed in cells of mesenchymal origin, vimentin may also be expressed with other intermediate filament proteins during early stages of development. In some cases, as differentiation continues, vimentin is normally down-regulated whereas other intermediate filament proteins, like desmin, glial fibrillary acidic protein, or neurofilaments are turned on in muscle, glial cells, or neurons, respectively. In some metastatic cancers, including breast and prostate cancers, vimentin is aberrantly expressed, despite the embryonic origin of the metastatic cell. From a Northern analysis (Thompson et al., 1992; Stover et al., 1994), it was determined that vimentin mRNA is highly abundant in the metastatic breast carcinoma cell line, MDA-MB-231, while in the nonmetastatic breast carcinoma cell line, MCF-7, no vimentin mRNA is present.
A central question to metastasis is, how is the vimentin gene expressed in the metastatic but not the nonmetastatic cancer cell? Several cis-acting elements localized to the 5'-end of the chicken vimentin gene and trans-acting factors important in the regulation of vimentin gene expression have been identified. By sequence homology, comparable elements can be found in the human vimentin gene. Most notable of these is a unique silencer element and an overriding element, referred to as an antisilencer. These elements bind a 90 kDa and 120 kDa protein, respectively, in chicken, mouse, and human nuclear extracts. Previously, the silencer factor was found to be missing in nuclear extracts from a metastatic breast cancer cell line MDA-MB-231 but abundant in the nonmetastatic counterpart MCF-7 (Stover et al., 1994). The antisilencer exhibits the opposite pattern. Here, various combinations of these elements have been fused to the bacterial chloramphenicol acetyltransferase reporter gene, CAT. Transcriptional activity was then compared in the different breast cancer cell lines in order to try and understand how vimentin is expressed in the metastatic but not the nonmetastatic cancer cell.
| Identifer | oai:union.ndltd.org:vcu.edu/oai:scholarscompass.vcu.edu:etd-5424 |
| Date | 01 January 1994 |
| Creators | Bird, Danielle N. |
| Publisher | VCU Scholars Compass |
| Source Sets | Virginia Commonwealth University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
| Rights | © The Author |
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