Erlotinib Activates Different Cell Death Pathways in EGFR-mutant Lung Cancer Cells Grown in 3D Versus 2D Culture Systems

BACKGROUND/AIM Non-small cell lung cancer patients with epidermal growth factor receptor (EGFR) mutation have been shown to have a good response to erlotinib, a receptor tyrosine kinase inhibitor of EGFR. In this study, we found that the cell death pathways activated by erlotinib in 2D and 3D culture systems are different. MATERIALS AND METHODS The cell death pathways induced by erlotinib were evaluated by flow cytometry and immunoblotting in both 2D and 3D culture systems of EGFR mutant lung cancer cells. RESULTS Treatment with erlotinib induced caspase 8 activation and up-regulation of TNF-related apoptosis-inducing ligand (TRAIL) expression only in 3D cultures. Knockdown of TRAIL attenuated both erlotinib-induced activation of caspase-8 and apoptosis in 3D cultures. Erlotinib also increased LC3, an autophagy marker, expression and c-Jun N terminal kinase (JNK) activation. Both 3-MA as an autophagy inhibitor and SP600125 as a JNK inhibitor, significantly inhibited erlotinib-induced cell death. CONCLUSION Erlotinib induces apoptotic cell death in 3D cultures through an autophagy-TRAIL-JNK pathway.