Abstract B029: TWIST1 Associates with resistance to treatment and Twist1 drives tumor progression in vivo for small cell lung cancer
Authors: Nguyen Triet , Chang Jinhee , Gabrielson Kathleen , Shetty Amol , Song Yang , Chatterjee Apaala , Lafargue Audrey , Kim Yoo Sun , Council Danielle , Chan Aaron , Chowdhury Dipanwita Dutta , Khan Muhammad Ajmal , Connis Nick , Sforza Daniel , Gardner Eric , McFarland Christopher , Rezaee Mohammad , Roper Nitin , Hann Christine , Tran Phuoc T. 
Published: January 2025

Abstract
Purpose: Small cell lung cancer (SCLC) is a highly aggressive and deadly malignancy. Two major factors contributing to the high mortality of SCLC are early metastasis and rapid development of therapy resistance. Recent research suggests upregulation of the epithelial-mesenchymal transition (EMT) program and the EMT transcription factor Twist1 correlated with accelerated tumor progression and chemoradiation (CRT) resistance in SCLC. However, a causal relationship between Twist1 and these aspects of SCLC biology has not been rigorously studied. Here, we investigated whether Twist1 upregulation could promote SCLC tumorigenesis, metastasis, and resistance to CRT. Materials and Methods: We analyzed transcriptomic data from the IMpower133 phase 3 trial of extensive stage SCLC stratified by median TWIST1 levels using Kaplan-Meir statistic. To investigate the roles of Twist1 directly in SCLC biology, we have generated a novel genetically engineered mouse model (GEMM) termed RPGT (Rb1Flox; Trp53Flox; ROSA26LSL-rtTA-IRES-EGFP; Twist1-TetO7-Luc). The RPGT GEMM enables the generation of autochthonous SCLC tumors after induction with Cre recombinase adenovirus. By withdrawing or providing doxycycline to mice, we can control Twist1 expression to activate or inactivate EMT in tumors. By characterizing mouse tumor samples with histological, immunostaining, and transcriptomic profiling analyses, we evaluated the impact of Twist1 and EMT upregulation on SCLC tumor biology and plasticity as well as metastatic spread and outgrowth. To evaluate the impact of EMT activation on SCLC sensitivity to CRT, we performed in vitro viability assays on primary tumor cell lines established from RPGT tumors. We also treated RPGT mice with vs. without Twist1 overexpression with CRT to validate our in vitro data. Results: In the chemotherapy alone control arm of IMpower133 there was a trend towards a difference in overall survival (OS) between TWIST1-high or -low patients (p=025 by log-rank) and in the NMF1/NEUROD1 subtype, patients with TWIST1-high had statistically significantly inferior OS (p=0.01). We then observed that both control (no Twist1 overexpression) and Twist1-overexpressing RPGT mice developed neuroendocrine SCLC tumors. While SCLC-ASCL1 was the predominant subtype in both cohorts, RPGT tumors exhibited more plasticity, with features associated with SCLC-NEUROD1 subtype. Furthermore, Twist1 overexpression dramatically increased the metastatic incidence in RPGT compared to control animals, indicating an important role of EMT in SCLC dissemination. Transcriptomic profiling of primary tumors and matching metastases in RPGT mice also revealed downregulation of Twist1 and EMT in metastases, suggesting that EMT suppression was necessary for metastatic outgrowth. Furthermore, we found that repressing Twist1 expression enhanced SCLC susceptibility to CRT both in vitro and in vivo. Conclusions: Overall, our data suggest that TWIST1/Twist1 plays an important role in promoting SCLC plasticity, metastasis, and treatment resistance.
Citation Format: Triet Nguyen, Jinhee Chang, Kathleen Gabrielson, Amol Shetty, Yang Song, Apaala Chatterjee, Audrey Lafargue, Yoo Sun Kim, Danielle Council, Aaron Chan, Dipanwita Dutta Chowdhury, Muhammad Ajmal Khan, Nick Connis, Daniel Sforza, Eric Gardner, Christopher McFarland, Mohammad Rezaee, Nitin Roper, Christine Hann, Phuoc T. Tran. TWIST1 Associates with resistance to treatment and Twist1 drives tumor progression in vivo for small cell lung cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Translating Targeted Therapies in Combination with Radiotherapy; 2025 Jan 26-29; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(2_Suppl):Abstract nr B029.