Cell State Plasticity and Spatial Organization of the Pancreatic Epithelium in Homeostasis, Injury and Cancer

Pancreatic ductal adenocarcinoma (PDAC) remains among the most lethal human malignancies, with a five-year survival under 15 percent1. The identity of the cells in which PDAC initiates, and the spatial and molecular heterogeneity of the human pancreatic ductal epithelium, are critical and incompletely resolved questions. This dissertation integrates novel mouse lineage tracing, ex-vivo organoid single-cell transcriptomics, and spatially resolved transcriptomics of human pancreatic tissue to dissect the role of the pancreatic ductal glands (PDGs) as a candidate cell of origin for PDAC and to characterize the larger ductal compartment that has been systematically under-represented in published single-cell atlases. Using the novel TFF2-iCre-ERT2; ROSA26mT/mG mouse system, we demonstrate that TFF2-expressing PDG cells function as transit-amplifying progenitors during ductal epithelial regeneration following cerulein-induced pancreatitis. In compound transgenic models (TTKS and TTKP), oncogenic Kras combined with Smad4 or Trp53 loss in TFF2-expressing cells converts these progenitors into self-renewing cancer stem-like cells that drive progressive PanIN and IPMN like lesions, and ultimately invasive PDAC. Single-cell sequencing of organoids reveals a TA-to-CSC transition characterized by collapse of ductal-identity transcription factors, activation of integrated stress/UPR programs, and dominance of an AREG-EGFR signaling axis. Spatial transcriptomic profiling of normal human pancreata using GeoMx and CosMx spatial profiling defines a previously under-described transcriptional heterogeneity within the large ducts and PDG compartment, including a rare periductal somatostatin-expressing population. Finally, multi-platform spatial and whole-exome characterization of a rare KRAS-wild-type undifferentiated carcinoma with rhabdoid features identifies a Class II BRAF deletion as an actionable target. Collectively, this work establishes the PDG as a bona fide cell of origin for PDAC, defines the earliest molecular programs of its malignant transformation, and provides a spatially resolved reference map of human pancreatic ductal heterogeneity with an emphasis on the larger ducts and associated ductal glands, with direct implications for early detection, molecular stratification, and therapeutic targeting of pancreatic cancer.