Biochemical and Biophysical Research Communications, Vol.423, No.4, 667-671, 2012
NF-kappa B signaling is activated and confers resistance to apoptosis in three-dimensionally cultured EGFR-mutant lung adenocarcinoma cells
Epidermal growth factor receptor (EGFR)-mutant lung adenocarcinoma cells in suspension undergo apoptosis to a greater extent than adherent cells in a monolayer when EGFR autophosphorylation is inhibited by EGFR tyrosine kinase inhibitors (TKIs). This suggests that cell adhesion to a culture dish may activate an anti-apoptotic signaling pathway other than the EGFR pathway. Since the microenvironment of cells cultured in a monolayer are substantially different to that of cells existing in three-dimension (3D) in vivo, we assessed whether two EGFR-mutant lung adenocarcinoma cell lines, HCC827 and H1975, were more resistant to EGFR TKI-induced apoptosis when cultured in a 3D extracellular matrix (ECM) as compared with in suspension. The ECM-adherent EGFR-mutant cells in 3D were significantly less sensitive to treatment with WZ4002, an EGFR TKI, than the suspended cells. Further, a marked degradation of I kappa B alpha, the inhibitor of nuclear factor (NF)-kappa B, was observed only in the 3D-cultured cells, leading to an increase in the activation of NF-kappa B. Moreover, the inhibition of NF-kappa B with pharmacological inhibitors enhanced EGFR TKI-induced apoptosis in 3D-cultured EGFR-mutant cells. These results suggest that inhibition of NF-kappa B signaling would render ECM-adherent EGFR-mutant lung adenocarcinoma cells in vivo more susceptible to EGFR TKI-induced cell death. (C) 2012 Elsevier Inc. All rights reserved.