ERK activation and nuclear signaling induced by the loss of cell/matrix adhesion stimulates anchorage‐independent growth of ovarian cancer cells

Abstract

Ovarian cancer metastasis involves the sloughing of epithelial cells from the ovary into the peritoneal cavity, where the cells can survive and proliferate in peritoneal ascites under anchorage-independent conditions. For normal epithelial cells and fibroblasts, cell adhesion to the extracellular matrix is required to prevent apoptosis and for proper activation and nuclear signaling of the ERK MAP kinase. The mechanisms of ERK regulation by adhesion have been determined by our lab and others. In this report, we elucidate a novel means of ERK regulation by cellular adhesion in ovarian cancer cells. We demonstrate that ERK and its activator MEK are robustly stimulated after cell detachment from a substratum in several ovarian cancer cell lines, but not a benign ovarian cell line, independent of serum and FAK or PAK activity. MEK and ERK activation was sustained for 48 h after detachment, while activation by serum or growth factors in adherent cells was transient. Re-attachment of suspended ovarian cells to fibronectin restored basal levels of MEK and ERK activity. ERK activity in suspended cells was dynamically controlled through an autocrine stimulatory pathway and prevalent phosphatase activity. Suspended cells demonstrated higher levels of ERK nuclear signaling to Elk1 compared to adherent cells. Inhibition of ERK activation with the MEK inhibitor U0126 had minor effects on adherent cell growth, but greatly decreased growth in soft agar. These data demonstrate a unique regulation of ERK by cellular adhesion and suggest a mechanism by which ERK may regulate anchorage-independent growth of metastatic ovarian cancer cells.

Role of Fetuin-A in Breast Tumor Cell Growth

“…Surprisingly the ERK1/2 activation signal in anchorage-independent cells in the presence of exosomes (0.1 mg/ml) was evident even after 18 h of growth (data not shown). A similar sustained activation of ERK in non-adhered cells was recently reported in ovarian cancer cells [31].…”

“…As expected most of the cell attachment and growth activities are associated with fetuin-A and not α-2-macroglobulin. Now that we have established this method, we hope to begin to purify large quantities of human fetuin-A using this method (Months [30][31][32]. This is the first time we have been able to see a single band of fetuin-A in both SDS-PAGE-coomassie and western blot.…”

Mitogen-Activated Protein Kinase Phosphorylation of Splicing Factor 45 (SPF45) Regulates SPF45 Alternative Splicing Site Utilization, Proliferation, and Cell Adhesion

“…Clone T8 was used further and named SKOV-3-QG. We recently demonstrated an enhancement of ERK activation in detached SKOV-3 cells, which induced ERK2 nuclear signaling (1). Therefore, SKOV-3-QG cells were either grown adherent (Adh) or trypsinized and put into suspension culture (Susp) for 3 h. The cells were then lysed, and FLAG-ERK2-Q103G was immunoprecipitated under mild conditions to preserve protein-protein interactions and incubated in kinase buffer containing [␥-…”

E-cadherin promotes proliferation of human ovarian cancer cells in vitro via activating MEK/ERK pathway

“…The activation of EGFR/ MEK/ERK signaling has been demonstrated to support survival in squamous cell carcinoma cells by inducing the antiapoptotic protein Bcl-2 [29] . In addition, MEK/ERK singling has been reported to help cells escape anoikis and maintain anchorage-independent growth in several ovarian cancer cell lines which are deprived of ECM in an in vitro environment that intimates the conditions of metastatic cells detached from ovaries and able to survive in the ascites of ovarian cancer patients [30] . These reports may partially explain the underlying mechanism of how E-cadherin promotes ovarian cancer cell survival and proliferation, which may help to clarify the unique role of E-cadherin in ovarian cancer progression.…”