Twist1 Overexpression Models an Aggressive Subtype of Pancreatic Ductal Adenocarcinoma in vivo

Pancreatic ductal adenocarcinoma (PDAC) is a lethal cancer with very poor survival outcomes. Genomic analyses have identified distinct molecular subtypes in human PDAC with quasimesenchymal/squamous/basal-like (QSB) having the worse prognosis. However, no in vivo models exist for QSB subtypes. The epithelial-mesenchymal transition (EMT) transcription factor TWIST1 is upregulated in QSB PDAC. We hypothesized that the TWIST1-dependent plasticity program is a key regulator of QSB PDAC subtype development. Non-negative matrix factorization (NMF) of human PDAC subtypes identified 3 NMF clusters. NMF1 was dominated by QSB subtypes, had the worst overall survival, and exhibited high TWIST1 expression. We generated a novel tetracycline-inducible autochthonous pancreas specific KrasG12D-Twist1 genetically engineered tumor mouse model (Pdx1 promoter-Cre (P); LSL-KrasG12D (R); LSL-rtTA-IRES-GFP (G); Twist1-tetO-Luc (T)). PGRT mice showed accelerated pancreatic tumor development and decreased overall median survival compared to PGR (KrasG12D alone) mice (4.6 months vs 9.7 months, p< 0.0001). Histological analyses showed that PGRT pancreatic tumors spanned a spectrum of PDAC to QSB PDAC subtype, exhibited an EMT profile and squamous histology. Twist1 induction resulted in increased metastases (9.52 % PGR at 48 weeks vs 73.91% PGRT at 24 weeks, p<0.0001). PGRT tumors demonstrated gene expression programs related to collagen content, EMT and cell movement and was most concordant with human QSB PDAC subtypes and squamoid single cell subtype. Twist1 overexpression cooperated with KrasG12D for PDAC development in vivo and progression towards metastasis and mimicked the human QSB PDAC subtypes. This novel model may offer new perspectives for PDAC research and for the testing of novel therapeutic strategies in an aggressive PDAC subtype.