Abstract 2848: DNA replication stress and mitotic catastrophe mediate sotorasib addiction in KRASG12C-mutant cancer
Authors: Chiou Li-Wen , Chan Chien-Hui , Jhuang Yu-Ling , Yang Ching-Yao , Jeng Yung-Ming 
Published: April 2023

Abstract
The KRASG12C inhibitor sotorasib was approved by the US Food and Drug Administration (FDA) for treating KRASG12Cmutant locally advanced or metastatic NSCLC in 2021 (Nakajima, Drezner et al. 2022). Clinical trials on the use of sotorasib for cancer treatment have demonstrated promising results. However, KRASG12C-mutant cancers can acquire resistance to sotorasib after treatment. Most of the drug resistance mechanisms converge on reactivation of the MAPK pathway to bypass KRAS inhibition (Adachi, Ito et al. 2020, Ryan, Fece de la Cruz et al. 2020, Xue, Zhao et al. 2020, Zhao, Murciano-Goroff et al. 2021, Liu, Kang et al. 2022). Identifying the underlying drug resistance mechanisms is critical for improving treatment response and developing more effective combination strategies. During study on the mechanisms underlying sotorasib resistance, we incidentally found that when cultured in sotorasib-free medium, KRASG12C-mutant cancer cells adopted to sotorasib demonstrated a decreased growth rate and increased cell death. A similar “drug addiction” phenomenon was noted in BRAF-mutant cells treated with BRAF or MEK inhibitors (Das Thakur, Salangsang et al. 2013, Moriceau, Hugo et al. 2015, Hong, Moriceau et al. 2018, Rao, Shi et al. 2020). Here, we first verified the death property induced by sotorasib withdrawal in sotorasib-resistant cells, and further explored the mechanism underlying sotorasib addiction. Finally, we provide a novel therapeutic strategy against sotorasib-addicted cells. In the results, we uncovered in the absence of sotorasib, the sotorasib-resistant cells underwent p21Waf1/Cip1-mediated cell cycle arrest and caspase-dependent cell death. Robust mitogen-activated protein kinase (MAPK) pathway activation after sotorasib withdrawal triggered severe DNA damage and replication stress, resulting in DNA damage response (DDR) activation. Persistent MAPK pathway hyperactivation concomitant with exhausted DDR eventually drove the premature entry of cells into mitosis and to aberrant mitosis, followed by micronucleus and nucleoplasmic bridge formation. Pharmacologic activation of the MAPK pathway with a type I BRAF inhibitor could further enhance the effects of sotorasib withdrawal in sotorasib-resistant cancer cells in vitro and in vivo. Collectively, we identified the sotorasib addiction phenomenon in cancer cells, determined the underlying mechanisms of replication stress and mitotic catastrophe, and provide a novel therapeutic strategy against sotorasib-addicted cells with pharmacological enhancement of aberrant MAPK activation with a type I BRAF inhibitor, which can more effectively restrained cell growth both in vitro and in vivo.
Citation Format: Li-Wen Chiou, Chien-Hui Chan, Yu-Ling Jhuang, Ching-Yao Yang, Yung-Ming Jeng. DNA replication stress and mitotic catastrophe mediate sotorasib addiction in KRASG12C-mutant cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2848.