Abstract 344: Mifepristone alters morphology, cytoskeletal architecture, and epithelial-mesenchymal transition-related proteins in human metastatic cancer cells

Abstract

Abstract The burden of secondary metastatic spread accounts for nearly 90% of cancer-related deaths. The ability of cancer cells to metastasize is often accompanied by biochemical changes leading to transition from an epithelial to a mesenchymal phenotype (EMT), changes in cell morphology, loss of tight junctions, remodeling of the cytoskeleton, and acquisition of migratory and invasive capacities. Previous work in our laboratory demonstrated that the antiprogestin mifepristone (MF) inhibits growth of known metastatic ovarian, prostate, breast, and brain cancer cells. In response to MF the cells displayed changes in morphology, and had reduced adhesive, migratory, and invasive capabilities. In this study, we assessed if such anti-metastatic phenotype induced by MF is associated with changes in the expression of EMT biomarkers (vimentin, slug, E-cadherin, and high and low molecular weight keratins), abundance of actin and tubulin, and/or modifications in the composition or intracellular localization of focal adhesion proteins [vinculin, phospho-focal adhesion kinase (p-FAK), and total FAK]. We studied all these parameters in cancer cells of the ovary (SK-OV-3), breast (MDA-MB-231), prostate (LNCaP), and brain (U87MG) upon exposure to concentrations of MF that block growth, adhesion, migration and invasion. MF induced a striking change in cellular morphology that was similar in all cell lines, and that included shrinkage of the cell body, long, thin cellular extensions, and a loss of cell-to-cell connections. Morphology changes were dependent on time of drug exposure, not influenced by cell density, and not associated with changes in the abundance of actin and tubulin, but instead linked to a remarkable cytoplasmic redistribution of actin and tubulin filaments. Upon removal of MF, cell morphology and proliferation returned to normal in all cell lines expect for LNCaP in which MF appears to induce irreversibly quiescence. The epithelial marker E-cadherin was found expressed only in LNCaP cells, and was not modified by MF. The mesenchymal intermediate filament protein vimentin was found in SK-OV-3, MDA-MB-231, and U87MG cells, but not in LNCaP cells. MF had a slight tendency to increase vimentin expression in SK-OV-3 and U87MG cells, and altered the expression of cytokeratins in LNCaP, MDA-MB-231 and U87MG, but not in SK-OV-3 cells. The focal adhesion marker, vinculin, was highly expressed in all cell lines and was not modified by MF, whereas FAK and p-FAK were reduced by MF in LNCaP, MDA-MB-231, and U87MG cells, but not in SK-OV-3 cells. In summary the anti-cancer effect of MF manifested by inhibition of cell growth, adhesion, migration, and invasion, is also associated with profound changes in cell morphology, actin and tubulin distribution, and, to a lesser extent, dysregulation of FAK, p-FAK and EMT-related proteins. 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 344. doi:1538-7445.AM2012-344