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 Therapeutics

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 4

Osimertinib does not affect TOP2A transcription but promotes GSK3-dependent and FBXW7-mediated Topo IIα protein degradation associated with suppression of SMURF2 expression.

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Osimertinib does not affect TOP2A transcription but promotes GSK3-depend...
(A) The tested cell lines were exposed to 200 nM osimertinib (Osim) for 16 hours. TOP2A mRNA was detected with quantitative reverse transcription PCR. NS, not significant with 2-sided unpaired Student’s t test. (B) The tested cell lines were pretreated with 10 μM MG132 for 30 minutes and then cotreated with DMSO or 200 nM osimertinib for another 6 hours. (C) Both PC-9 and HCC827 cells were treated with 200 nM osimertinib for 16 hours followed by the addition of 10 μg/mL CHX and then harvested at the indicated times. (D) RNA-Seq detection of SMURF2 mRNA expression in the given cell lines exposed to 100 nM osimertinib for 14 hours. (E) The tested cell lines were exposed to varied concentrations of osimertinib as indicated for 24 hours. (F and G) The tested cell lines were transfected with the given siRNAs or infected with lentiviruses carrying the given shRNA for 48 hours. (H) The tested cell lines were exposed to 10 μg/mL CHX and then harvested at different times as indicated. (I) The tested cell lines were treated with 200 nM osimertinib for 24 hours. (J) Both PC-9 and HCC827 were pretreated with 10 μM CHIR99021 or SB216763 for 30 minutes and then cotreated with 200 nM osimertinib for an additional 16 hours. (K and L) The tested cell lines were transfected with scrambled GSK3 (K) or FBXW7 (L) siRNA for 48 hours followed by treatment with 200 nM osimertinib for another 24 hours. (M) The indicated cell lines expressing pLKO.1 or shFBXW7 were exposed to 200 nM osimertinib for 24 hours. The proteins with the aforementioned treatments were detected with Western blotting. Band intensities were quantified with ImageJ (NIH) software and plotted as percentage of 0 time (C and H).