Molecular dynamics driving phenotypic divergence among KRAS mutants in pancreatic tumorigenesis.

Inflammation in the pancreas drives acinar-to-ductal metaplasia (ADM), a progenitor-like state that can be hijacked by mutant Kras in the formation of pancreatic ductal adenocarcinoma. How these cell fate decisions vary according to KRAS mutation remains poorly understood. To define mutation-specific lineage reversion and tumor initiation, we implement Ptf1a-tdTomato mice and multiple KRAS mutants across several genetic, pharmacologic, and inflammatory perturbations in vivo. Whereas KRASG12D co-opts injury to enable lineage reversion, enhancer reprogramming, and tumor initiation, KRASG12R/V cannot sustain dedifferentiated and neoplastic transcriptional and epigenetic programs. Specifically, KRASG12R/V mutants fail to invoke robust EGFR, AKT, and RAC1/VAV1 signaling and to license Pou2f3 and Vav1 in chromatin, such that only constitutive AKT activation is sufficient to rescue the tumorigenic potential of KRASG12Rin vivo. As the marked heterogeneity among KRAS variants begins early in tumorigenesis, these data are crucial to deciphering mutation-specific oncogenic trajectories and directing the implementation of KRAS-directed therapeutics.