DNA topoisomerase II inhibition potentiates osimertinib’s therapeutic efficacy in EGFR-mutant non–small cell lung cancer models
Zhen Chen, … , Suresh S. Ramalingam, Shi-Yong Sun
Zhen Chen, … , Suresh S. Ramalingam, Shi-Yong Sun
Published March 7, 2024
Citation Information: J Clin Invest. 2024;134(10):e172716. https://doi.org/10.1172/JCI172716.
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Research Article Oncology

DNA topoisomerase II inhibition potentiates osimertinib’s therapeutic efficacy in EGFR-mutant non–small cell lung cancer models

Abstract

Development of effective strategies to manage the inevitable acquired resistance to osimertinib, a third-generation EGFR inhibitor for the treatment of EGFR-mutant (EGFRm) non–small cell lung cancer (NSCLC), is urgently needed. This study reports that DNA topoisomerase II (Topo II) inhibitors, doxorubicin and etoposide, synergistically decreased cell survival, with enhanced induction of DNA damage and apoptosis in osimertinib-resistant cells; suppressed the growth of osimertinib-resistant tumors; and delayed the emergence of osimertinib-acquired resistance. Mechanistically, osimertinib decreased Topo IIα levels in EGFRm NSCLC cells by facilitating FBXW7-mediated proteasomal degradation, resulting in induction of DNA damage; these effects were lost in osimertinib-resistant cell lines that possess elevated levels of Topo IIα. Increased Topo IIα levels were also detected in the majority of tissue samples from patients with NSCLC after relapse from EGFR tyrosine kinase inhibitor treatment. Enforced expression of an ectopic TOP2A gene in sensitive EGFRm NSCLC cells conferred resistance to osimertinib, whereas knockdown of TOP2A in osimertinib-resistant cell lines restored their susceptibility to osimertinib-induced DNA damage and apoptosis. Together, these results reveal an essential role of Topo IIα inhibition in mediating the therapeutic efficacy of osimertinib against EGFRm NSCLC, providing scientific rationale for targeting Topo II to manage acquired resistance to osimertinib.

Authors

Zhen Chen, Karin A. Vallega, Dongsheng Wang, Zihan Quan, Songqing Fan, Qiming Wang, Ticiana Leal, Suresh S. Ramalingam, Shi-Yong Sun

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Figure 3

Osimertinib, as well as other EGFR-TKIs, decreases the levels of Topo IIα and induces γ-H2AX foci formation in EGFRm NSCLC cells and tissues, and overexpression of ectopic TOP2A attenuates the effects of osimertinib on induction of apoptosis, decreasing cell survival, and increasing γ-H2AX foci formation.

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Osimertinib, as well as other EGFR-TKIs, decreases the levels of Topo II...
(A–D) The given cell lines were exposed to varied concentrations of osimertinib (Osim) for 24 hours (A), 200 nM osimertinib for different times (B), 200 nM different EGFR-TKIs for 24 hours (C), or 500 nM osimertinib for 24 hours (D). Proteins of interest were detected with Western blotting. (E) Topo IIα in tissues was detected with IHC. Scale bar: 50 μm. (F and J) The indicated cell lines were exposed to 250 nM osimertinib for 16 hours and then stained with anti–γ-H2AX antibody and DAPI. DSB inducer here served as a positive control and was used at 100 μM for 1 hour of treatment. Scale bar: 25 μm (F and J); 5 μm (F, high-magnification images). (G–I) The indicated cell lines were exposed to DMSO or 200 nM osimertinib for 18 hours (G) or 24 hours (H) or treated with different concentrations of osimertinib for 3 days (I). The proteins of interest were detected with Western blotting (G), and apoptotic cells were detected with annexin V staining/flow cytometry (H). Each bar in H represents mean ± SD of triplicate treatments. Cell numbers were measured by the SRB assay and are expressed as mean ± SD of 4 replicate determinations (I). Statistical differences between 2 groups were conducted with 2-sided unpaired Student’s t test.