The combination of antitumor drugs, exemestane and erlotinib, induced resistance mechanism in H358 and A549 non-small cell lung cancer (NSCLC) cell lines

Abstract

Context: Estrogens in non-small-cell lung cancer (NSCLC) are important, and their interaction with epidermal growth factor receptor (EGFR) might be crucial.

Objective: This study investigates the effect of exemestane, an aromatase inhibitor, and erlotinib, an EGFR inhibitor, on human NSCLC cell lines; H23, H358 and A549.

Materials and methods: A cell proliferation assay was used for measuring cell number, apoptosis assay for detecting apoptosis and necrosis and immunoblotting for beclin-1 and Bcl-2 proteins detection. An immunofluorescence assay was used for EGFR localization. A migration assay and zymography were used for cell motility and metalloproteinases (MMPs) expression, respectively.

Results: Exemestane, erlotinib or their combination decreased cell proliferation and increased apoptosis. Exemestane’s half maximal inhibitory concentration (IC₅₀) was 50 μM for H23 and H358 cells and 20 μM for A549. The IC₅₀ of erlotinib was 25 μM for all cell lines. Apoptosis increase induced by exemestane was 58.0 (H23), 186.3 (H358) and 34.7% (A549) and by erlotinib was 16.7 (H23), 65.3 (H358) and 66.3% (A549). A synergy effect was observed only in H23 cells. Noteworthy, the combination of exemestane and erlotinib decreased beclin-1 protein levels (32.3 ± 19.2%), an indicator of autophagy, in H23 cells. The combination of exemestane and erlotinib partially reversed the EGFR translocation to mitochondria and decreased MMP levels and migration.

Discussion and conclusions: The benefit from a dual targeting of aromatase and EGFR seems to be regulated by NSCLC cell content. The diverse responses of cells to agents might be influenced by the dominance of certain molecular pathways.

• Beclin-1
• EGFR
• migration
• mitochondria

Acknowledgements

We would like to thank the Medical School, University of Patras, Greece, for providing us the Advanced Light Microscopy facility, EOGE Oncological Research Fund for financial support and Gregoris Iconomou, PhD, Quality of life Unit, Division of Oncology, University Hospital of Patras, Greece for linguistic editing.