Mouse Models for Pancreatic Ductal Adenocarcinoma are Affected by the cre-driver Used to Promote KRASG12D Activation

The fundamental biology of pancreatic ductal adenocarcinoma has been greatly impacted by the characterization of genetically engineered mouse models that allow temporal and spatial activation of oncogenic KRAS (KRASG12D). One of the most commonly used models involves targeted insertion of a cre-recombinase into the Ptf1a gene. However, this approach disrupts the Ptf1a gene, resulting in haploinsufficiency that likely affects sensitivity to oncogenic KRAS (KRASG12D). This study aims to determine if Ptf1a haploinsufficiency affected the acinar cell response to KRASG12D before and after induction of pancreatic injury.

The fundamental biology of pancreatic ductal adenocarcinoma has been greatly impacted by the characterization of genetically engineered mouse models that allow temporal and spatial activation of oncogenic KRAS (KRASG12D). One of the most commonly used models involves targeted insertion of a cre-recombinase into the Ptf1a gene. However, this approach disrupts the Ptf1a gene, resulting in haploinsufficiency that likely affects sensitivity to oncogenic KRAS (KRASG12D). This study aims to determine if Ptf1a haploinsufficiency affected the acinar cell response to KRASG12D before and after induction of pancreatic injury.

These findings suggest Ptf1a haploinsufficiency in Ptf1acreERT mouse models promotes KRASG12D priming of genes for promotion of pancreatic ductal adenocarcinoma.

We performed morphological and molecular analysis of 3 genetically engineered mouse models that express a tamoxifen-inducible cre-recombinase to activate KrasG12D in acinar cells of the pancreas. The cre-recombinase was targeted to the acinar-specific transcription factor genes, Ptf1a or Mist1/Bhlha15, or expressed within a BAC-derived Elastase transgene. Histological and RNA-seq analyses were used to delineate differences between the models.

Up to 2 months after tamoxifen induction of KRASG12D, morphological changes were negligible. However, induction of pancreatic injury by cerulein resulted in widespread PanIN lesions in Ptf1acreERT pancreata within 7 days and maintained for at least 5 weeks post-injury, which was not seen in the models with 2 functional Ptf1a alleles. RNA-sequencing analysis prior to injury induction suggested Ptf1acreERT and Mist1creERT mice have unique profiles of gene expression that predict a differential response to injury. Multiplex analysis of pancreatic tissue confirmed different inflammatory responses between the models. Conclusions: These findings suggest Ptf1a haploinsufficiency in Ptf1acreERT mouse models promotes KRASG12D priming of genes for promotion of pancreatic ductal adenocarcinoma.