Twist1-induced suppression of oncogene-induced senescence in non-small cell lung cancer requires the transactivation domain of Twist1.

Non-small cell lung carcinoma (NSCLC) is a major cause of cancer mortality. High expression of the epithelial-to-mesenchymal transition transcription factor (EMT-TF) Twist1 is strongly associated with metastatic cancers and with treatment resistance. Twist1 can also upregulate O-GlcNAcylation to suppress fail-safe programs such as Kras(G12D) oncogene-induced senescence (OIS) that accelerates NSCLC tumorigenesis. We wanted to decipher the critical domains and transcriptional targets required for Twist1 acceleration of lung tumorigenicity. We created a novel genetically-engineered mouse model for autochthonous lung cancer through lung epithelial expression of Kras(G12D) oncogene (CR) concomitantly with Twist1(wt) (CRT) or a Twist1(F191G) transactivation-deficient mutant (CRF191G). Compared to CR and CRF191G, CRT mice had shorter tumor-free survival and more aggressive tumors histologically. CRT lung tumors also showed higher proliferation and lower cell-cycle arrest suggesting that the Twist1 transactivation-domain is important for OIS suppression. Supporting these data, we observed in non-cancer human bronchial epithelial cells (HBECs) that the co-expression of human TWIST1(wt) enhanced tumorigenic/invasive programs and could suppress HRas(G12V)-induced senescence while co-expressing TWIST1(F187G) transactivation-deficient mutant could not. TWIST1(wt) co-expression with HRas(G12V) in HBECs differentially modulated MYC downstream transcriptional programs. Finally, OIS induction in HBECHRas(G12V)-TWIST1(wt) was rescued by O-GlcNAcylation inhibition or by treatment with a novel MYC inhibitor MYCi975 or by MYC knockdown. Altogether, these results indicate that the Twist1 transactivation domain is required for Twist1-dependent acceleration of lung tumorigenesis via MYC and nominate MYCi975 as a means to activate latent OIS programs. MYC targeting strategies could limit pro-tumorigenic programs and serve as a therapeutic for TWIST1-overexpressing NSCLCs.