Abstract 6060: The transactivation domain of TWIST1 is required for TWIST1-induced aggressiveness in non-small cell lung cancer
Authors: Lafargue Audrey , Wang Hailun , Chettiar Sivarajan T. , Gajula Rajendra P. , Taparra Kekoa , Nugent Katriana , Tran Phuoc T. 
Published: September 2020

Abstract
Lung cancer is the most common cause of mortality by cancer. Non-small cell lung carcinoma (NSCLC) accounts for 80% of lung cancers. Although progresses has been realized, resistance to current treatments still remain high and the overall survival is a dismal ~16%. The high expression of TWIST1 in cancers strongly correlates with invasive, resistant, and metastatic cancers, and is attributed to the induction of the epithelial-mesenchymal transition phenotype. Additionally, TWIST1 antagonizes the induction of the oncogene (KrasG12D)-induced senescence in primary NSCLC tumor. As TWIST1 is a pleiotropic transcription factor essential for development, the targeting of the entire TWIST1 protein may cause unintended side effects. Dissecting what are the critical domains of TWIST1 and its crucial downstream transcriptional targets required for TWIST1-dependent radioresistance and pro-tumorigenicity would allow to decipher new therapeutic strategies. In this goal, we generated a transactivation-null TWIST1 mutant by mutation of phenylalanine at position 191 to glycine and aimed to characterize its functions. We generated mouse models utilizing a tetracycline-inducible gene expression system: in this model, treatment with doxycycline allows to control concomitant induction of KrasG12D oncogene expression (R) with TWIST1 (T)/Luciferase expression or with TWIST1F191G mutant (T-F191G)/Luciferase expression, specifically in the lung epithelium using the CCSP promoter-rtTA construct (C). TWIST1 expression in CRT model induced a more aggressive tumor progression and a shorter survival (median= 15,6 weeks) compared to CR model (median= 31 weeks). The expression of TWIST1F191G mutant in CRT-F191G model abrogates these effects (median= 26.7 weeks) showing the importance of the transactivation domain of TWIST1 to fulfill its pro-tumor progression functions. Next, the histological analysis of the lung tumor sections of these models shown that the expression of TWIST1 in CRT mice induced a higher positivity for Ki67 and a reduced positivity for Caspase3. CRT mice also present a decrease for p16 expression compared to CR mice reflecting TWIST1-induced OIS suppression. Additionally, the expression of TWIST1F191G mutant shown a similar profile to CR model potentially indicating a role of TWIST1 transactivation domain in the suppression of OIS. On the other hand, the expression of TWIST1 in NSCLC lines conferred a partial radiation resistance. We also observed that the expression of TWIST1 in AEF line conferred the same resistant profile while the expression of TWIST1F191G increased the sensitivity to radiation. Moreover, the CRT model also presented more resistance to 1 × 15Gy or 10 × 3Gy thoracic irradiation suggesting again that targeting TWIST1 transactivation function would confer a potential new important therapeutic option.
Citation Format: Audrey Lafargue, Hailun Wang, Sivarajan T. Chettiar, Rajendra P. Gajula, Kekoa Taparra, Katriana Nugent, Phuoc T. Tran. The transactivation domain of TWIST1 is required for TWIST1-induced aggressiveness in non-small cell lung cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6060.