TWIST1 Suppresses Apoptosis and Mediates Therapeutic Resistance in Non-Small Cell Lung Cancer

Patients with non-small cell lung cancer (NSCLC) are classified into molecular subgroups based on the presence of oncogenic drivers. Patients with targetable oncogenic drivers, such as mutant EGFR, have benefited from tyrosine kinase inhibitors (TKIs) targeting these oncogenes. However, de-novo and acquired resistance to TKIs limits their efficacy. Studies investigating mechanisms of resistance to TKIs in NSCLC have demonstrated that epithelial-mesenchymal transition (EMT) is associated with resistance. TWIST1 is an EMT-transcription factor that is required for oncogene-driven NSCLC. Utilizing a chemical-bioinformatic screen, we identified the harmala alkaloid, harmine, as a first-in-class TWIST1 inhibitor. Harmine inhibited multiple TWIST1 functions, promoted TWIST1 degradation, and had activity in oncogene driver-defined NSCLC cell lines. Additionally, harmine cytotoxicity required degradation of the TWIST1-E2A heterodimer. Harmine also had activity in murine models of KRAS mutant NSCLC. Following identification of this novel TWIST1 inhibitor, we explored TWIST1 as potential target to overcome EGFR TKI resistance in EGFR mutant NSCLC. We demonstrated that TWIST1 expression is sufficient to mediate resistance to EGFR TKIs in vitro and in vivo. Genetic and pharmacological inhibition of TWIST1 in EGFR TKI resistant EGFR mutant cells increased sensitivity to EGFR TKIs. TWIST1-mediated EGFR TKI resistance was due in part to TWIST1 suppression of transcription of the pro-apoptotic gene, BCL2L11 (BIM), by directly binding to BCL2L11 intronic regions and promoter. In MET-driven NSCLC, TWIST1 overexpression mediated resistance to MET TKIs. Targeting TWIST1 with harmine increased crizotinib sensitivity in MET altered NSCLC cells. We also demonstrated that hepatocyte growth factor (HGF), a known mediator of EGFR and MET TKI resistance, induced TWIST1 expression. Harmine treatment overcame HGF-mediated resistance to MET and EGFR TKIs in MET- and EGFR-driven NSCLC. We also explored the role of TWIST1 in mediating resistance to other targeted agents in NSCLC. We demonstrated that TWIST1 negatively regulates death receptor signaling by directly upregulating transcription of CFLAR (CFLIP), an inhibitor of death receptor 4 and 5. TWIST1 upregulation of cFLIP was associated with resistance to TRAIL-based agents in NSCLC. Overall, these studies demonstrate that targeting TWIST1 is viable therapeutic strategy to overcome resistance to TKIs and TRAIL-based therapies in NSCLC