Induction of SREBP1 degradation coupled with suppression of SREBP1-mediated lipogenesis impacts the response of EGFR mutant NSCLC cells to osimertinib

• Type of Material: Article
• Authors: Zhen Chen, Emory University; Danlei Yu, Emory University; Taofeek Owonikoko, Emory University; Suresh Ramalingam, Emory University; Shi-Yong Sun, Emory University
• Language: English
• Date: 2021-10-11
• Publisher: SPRINGERNATURE
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2021, The Author(s), under exclusive licence to Springer Nature Limited
• Final Published Version (URL): http://dx.doi.org/10.1038/s41388-021-02057-0
• Title of Journal or Parent Work: ONCOGENE
• Volume: 40
• Issue: 49
• Start Page: 6653
• End Page: 6665
• Grant/Funding Information: This work was supported by the NIH/NCI R01 CA223220 (to S-Y.S.), R01 CA245386 (to S-Y.S.), UG1 CA233259 (to S.S.R.) and lung cancer SPORE P50 CA217691 DRP award (to S-YS) and Emory University Winship Cancer Institute lung cancer pilot funds (to S-Y.S)
• Keywords: FATTY-ACID SYNTHESIS; Life Sciences & Biomedicine; AZD9291; Oncology; INHIBITION; GROWTH; LIPID-METABOLISM; BIM; ACQUIRED-RESISTANCE; Cell Biology; THERAPEUTIC-EFFICACY; Science & Technology; Biochemistry & Molecular Biology; Genetics & Heredity

Abstract

Emergence of acquired resistance to osimertinib (AZD9291), the first-approved third-generation EGFR inhibitor that selectively and irreversibly inhibits the activating EGFR mutations and the resistant T790M mutation, is a giant and urgent clinical challenge. Fully understanding the biology underlying the response of EGFR mutant non-small cell lung cancer (NSCLC) to osimertinib is the foundation for development of mechanism-driven strategies to overcome acquired resistance to osimertinib or other third-generation EGFR inhibitors. This study focused on tackling this important issue by elucidating the critical role of sterol regulatory element-binding protein 1 (SREBP1) degradation in conferring the response of EGFR mutant NSCLC cells to osimertinib and by validating the strategy via directly targeting SREBP1 for overcoming osimertinib acquired resistance. Osimertinib facilitated degradation of the mature form of SREBP1 (mSREBP1) in a GSK3/FBXW7-dependent manner and reduced protein levels of its regulated genes in EGFR-mutant NSCLC cells/tumors accompanied with suppression of lipogenesis. Once resistant, EGFR-mutant NSCLC cell lines possessed elevated levels of mSREBP1, which were resistant to osimertinib modulation. Both genetic and pharmacological inhibition of SREBP1 sensitized osimertinib-resistant cells and tumors to osimertinib primarily through enhancing Bim-dependent induction of apoptosis, whereas enforced expression of ectopic SREBP1 in sensitive EGFR-mutant NSCLC cells compromised osimertinib’s cell-killing effects. Collectively, we have demonstrated a novel connection between osimertinib and SREBP1 degradation and its impact on the response of EGFR mutant NSCLC cells to osimertinib and suggested an effective strategy for overcoming acquired resistance to osimertinib, and possibly other EGFR inhibitors, via targeting SREBP1.