C-erbB-2/HER-2 upregulates fascin, an actin-bundling protein associated with cell motility, in human breast cancer cell lines

The over-expression of c-erbS-2/ HER-2, a receptor tyrosine kinase, correla tes with poor prognosis in patients with breast and ovarian cancer. In the human breast cancer cell line, MDA-MB-435, c-erbB-2 overexpression results in increased chemoinvasion and higher metastatic properties in nude mice. I -ion ever, the mechanisms by which c-erbB-2 increases the malignant potenti al of cells remains unclear. We have determined that over-expression of c-e rbB-2 in MDA-MB-435 cells, and in some additional breast cancer cell lines, is associated with graphic increases in mRNA and protein levels of the act in bundling protein fascin, Heightened fascin expression has been observed in other systems to result in greatly increased cell motility, and indeed, our work employing semi-automated time-lapse microscopy demonstrates that M DA-MB-435 cells over-expressing c-erbB-2 exhibit significantly heightened c ellular dynamics and locomotion, while visualization of bundled microfilame nts within fixed cells revealed enhanced formation of dendritic-like proces ses, microspikes and other dynamic actin based structures. To address the m eans by which c-erbB-2 over-expression might result in elevated fascin leve ls, we identified multiple perfect match TCF and NF-kappa B consensus sites in fascin's promoter and first intron,which appeared consistent with the g reater endogenous transcriptional activities of TCF and NF-kappa B in c-erb B-2 over-expressing MDA-MB-435 cells. While such transcriptional modulation may occur in the context of the intact gene/chromatin, subsequent tests us ing reporter constructs did not support involvement of these signaling path ways. In conclusion, highly increased fascin levels were observed in MDA-MB -435 over-expressing c-erbB-2, likely contributing to these cells' altered actin dynamics, and increased cell motility and malignancy. Studies in prog ress aim to discern the means by which c-erbB-2 over-expression leads to tr anscriptional activation of the fascin gene.