Medicinal Chemistry

Persistent N-cadherin Expression Induced by Extended Epidermal Growth Factor Exposure Regulates Multicellular Aggregate Compaction and Sensitivity to Cisplatin

Abstract

Sabrina L Samudio-Ruiz and Laurie G Hudson

Objective: In ovarian cancer, activation of the epidermal growth factor receptor (EGFR) is associated with poor prognosis. The presence of EGFR activators in patient ascites fluid may cause constitutive EGFR activation thereby contributing to metastasis and/or resistance to therapy. Our goal was to identify alterations resulting from constitutive EGFR activation that influence cell behavior and drug sensitivity.

Methods: We used an in vitro model (OVCA 433 cells) to evaluate changes in mesenchymal marker levels and multicellular aggregate (MCA) formation following long term epidermal growth factor (EGF) treatment. We determined sensitivity to cisplatin following EGF treatment and evaluated the role of the mesenchymal marker, N-cadherin, in aggregate formation and sensitivity using siRNA.

Results: We found that EGFR activation led to phenotypic and functional changes in ovarian tumor cells that were retained after ligand was withdrawn (removal). Expression levels of the mesenchymal markers N-cadherin and vimentin were elevated in EGF treated and removal cells. This persistent increase in mesenchymal markers was associated with a significant increase in (MCA) compaction and cell spreading when MCAs were plated on collagen. N-cadherin silencing decreased MCA compaction and spreading in cells following extended exposure to EGF or in cells with high endogenous levels of N-cadherin. Furthermore, the compact MCA structure in EGF treated cells with increased N-cadherin expression conferred resistance to cisplatin and N-cadherin silencing largely restored cisplatin sensitivity.

Conclusion: Our results indicate that prolonged EGFR activation causes a persistent change in mesenchymal marker expression, which regulates compaction and drug sensitivity. The findings implicate N-cadherin as a key regulator of the EGFR-dependent functional changes in MCAs such as compaction, spreading and sensitivity to platinum-based chemotherapeutics. These findings suggest a mechanism by which persistent EGFR activation in the microenvironment may drive changes in ovarian cancer cells that contribute to the poor prognosis associated with EGFR activation.