title: Bleb formation is induced by alkaline but not acidic pH in estrogen receptor silenced breast cancer cells.
abstract: De novo and acquired resistance to endocrine-based therapies in breast cancer occurs in parallel with epithelial to mesenchymal transition (EMT), which is associated with enhanced proliferative and metastatic potential, and poor clinical outcome. We have established several endocrine insensitive breast cancer lines by shRNA-induced depletion of estrogen receptor (ER) by transfection of MCF7 cells. All of these exhibit EMT. We have previously reported that brief exposure of specifically ER- breast cancer cells, to extracellular alkaline pH, results in cell rounding and segregation, and leads to enhanced invasive potential. In this study we describe more detailed morphological changes and compare these with cell exposure to acidic pH. Morphological changes and localization of various molecules critical for cell adhesion and motility, associated with pH effects, were assessed by live cell microscopy, electron microscopy, and immunofluorescence. Exposure of either ER- or ER+ breast cancer cells to extracellular acidic pH did not induce significant changes in morphological appearance. Conversely, brief exposure of specifically ER silenced cells, to alkaline pH, resulted in cell contractolation and formation of bleb-like actin-rich structures which were evenly distributed on the outer membrane. Integrin α2, FAK, and JAM-1 were found in the cytoplasm streaming into the newly formed blebs. These blebs appear to be related to cell polarity and movement. Pre-treatment with cytochalasin-D or inhibitors of Rho or MLCK prevented both contractolation and bleb formation. Our data suggest that the effect of pH on the microenvironment of endocrine resistant breast cancer cells needs to be more extensively investigated. Alkaline, rather than acidic pH, appears to induce dramatic morphological changes, and enhances their invasive capabilities, through re-organization of cortical actin.
authors: Faculty of Pharmacy, Kuwait University, Safat 13110, Kuwait.
authors: Maitham A
authors: MA
authors: Khajah
authors: Faculty of Pharmacy, Kuwait University, Safat 13110, Kuwait.
authors: Princy M
authors: PM
authors: Mathew
authors: Faculty of Pharmacy, Kuwait University, Safat 13110, Kuwait.
authors: Nada S
authors: NS
authors: Alam-Eldin
authors: Faculty of Pharmacy, Kuwait University, Safat 13110, Kuwait.
authors: Yunus A
authors: YA
authors: Luqmani
mesh_terms: D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology*; D015815:Cell Adhesion Molecules / Q000378:metabolism; D045744:Cell Line, Tumor; D002465:Cell Movement; D016764:Cell Polarity; D015638:Cytochalasin D / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D058750:Epithelial-Mesenchymal Transition; D005260:Female; D051417:Focal Adhesion Kinase 1 / Q000378:metabolism; D020868:Gene Silencing; D006801:Humans; D006863:Hydrogen-Ion Concentration; D039421:Integrin alpha2 / Q000378:metabolism; D061986:MCF-7 Cells; D011956:Receptors, Cell Surface / Q000378:metabolism; D011960:Receptors, Estrogen / Q000235:genetics*
chemical_list: D015815:Cell Adhesion Molecules; C407243:F11R protein, human; D039421:Integrin alpha2; D011956:Receptors, Cell Surface; D011960:Receptors, Estrogen; D015638:Cytochalasin D; D051417:Focal Adhesion Kinase 1; C496050:PTK2 protein, human