Selective epithelial expression of KRASG12D in the Oncopig pancreas drives ductal proliferation and desmoplasia that is accompanied by an immune response

Pancreatic ductal adenocarcinoma (PDAC) remains a formidable challenge in oncology, characterized by a high mortality rate, largely attributable to delayed diagnosis and the intricacies of its tumor microenvironment. Innovations in modeling pancreatic epithelial transformation provide valuable insights into the pathogenesis and potential therapeutic strategies for PDAC. We employed a porcine (Oncopig) model, utilizing the Ad-K8-Cre adenoviral vector, to investigate the effects of variable doses (10⁷ to 10¹⁰ pfu) on pancreatic epithelial cells. This vector, the expression from which being driven by a Keratin-8 promoter, will deliver Cre-recombinase specifically to epithelial cells. Intraductal pancreatic injections in transgenic Oncopigs (LSL-KRAS^G12D-TP53^R167H) were performed with histologically based evaluation at 2 months post-injection. Specificity of the adenoviral vector was validated through Keratin-8 expression and Cre-recombinase activity. We confirmed that the Ad-K8-Cre adenoviral vector predominantly targets ductal epithelial cells lining both large and small pancreatic ducts, as evidenced by Keratin 8 and CAM5.2 staining. Higher doses resulted in significant tissue morphology changes, including atrophy, and enlarged lymph nodes. Microscopic examination revealed concentration-dependent proliferation of the ductal epithelium, cellular atypia, metaplasia, and stromal alterations. Transgene expression was confirmed with immunohistochemistry. Desmoplastic responses were evident through vimentin, α-SMA, and Masson's trichrome staining, indicating progressive collagen deposition, particularly at the higher vector doses. Our study suggests a distinct dose-response relationship of Ad-K8-Cre in inducing pancreatic epithelial proliferation and possible neoplasia in an Oncopig model. All doses of the vector induced epithelial proliferation; the higher doses also produced stromal alterations, metaplasia, and possible neoplastic transformation. These findings highlight the potential for site-specific activation of oncogenes in large animal models of epithelial tumors, with the ability to induce stromal alterations reminiscent of human PDAC.