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 1

Topo II inhibitors in combination with osimertinib synergistically decrease cell survival, inhibit colony formation and growth, and induce Bim-dependent apoptosis in osimertinib-resistant EGFRm NSCLC cell lines.

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Topo II inhibitors in combination with osimertinib synergistically decre...
(A–C) The given cell lines were treated with 250 nM osimertinib (Osim), 1.25 μM VP-16, 125 nM DXR, 5 nM paclitaxel, 10 μM cisplatin, 25 μM carboplatin, 25 nM gemcitabine, 20 nM 5-FU, 25 μM cyclophosphamide, 25 μM capecitabine, or 10 nM vincristine alone or in combination (A) or with varied concentrations of the tested agents either alone or in combination (B and C) for 3 days. Cell numbers were then measured using the SRB assay. Data represent mean ± SD of 4 replicate determinations. **P < 0.01; ***P < 0.001 compared with each agent alone. The fixed suboptimal concentrations of the tested agents used in A were chosen based on their concentration-dependent survival curves. (D and E) The tested cell lines seeded in 12-well plates were treated with 50 nM osimertinib, 10 nM (PC-9/AR) or 50 nM (HCC827/AR) DXR, 150 nM VP-16, or the indicated combinations, which were repeated with fresh medium every 3 days. After 10 days, the cells were fixed, stained with crystal violet dye, imaged (D) and counted (E). Columns are mean ± SD of triplicate determinations. (F–J) The tested cell lines were exposed to 200 nM osimertinib, 100 nM (PC-9/AR) or 250 nM (HCC827/AR) DXR, 1 μM VP-16, or the indicated combinations for 48 hours (F, G, I, and J) or 16 hours (H). The proteins of interest were detected with Western blotting (F, H, and I), and apoptotic cells were detected with annexin V staining/flow cytometry (E and J). Each column represents mean ± SD of triplicate treatments. Statistical differences were conducted with 2-sided unpaired Student’s t test for 2 groups (J) or 1-way ANOVA test (A, E, and G) for multiple groups.