Preventive Treatment with a CD73 Small Molecule Inhibitor Enhances Immune Surveillance in K-Ras Mutant Pancreatic Intraepithelial Neoplasia

Immunoprevention is an emerging consideration for solid tumors, including pancreatic ductal adenocarcinoma (PDAC). We and others have shown that Kras mutations in genetic models of spontaneous pancreatic intraepithelial neoplasia (PanIN), which is a precursor to PDAC, results in CD73 expression in the neoplastic epithelium and some populations of infiltrating immune cells, including macrophages and CD8 T cells. CD73 is an ecto-enzyme that converts extracellular adenosine monophosphate (AMP) to adenosine, a critical immune inhibitory molecule in PDAC. We hypothesized inhibition of CD73 would reduce the incidence of PanIN formation and alter the immune microenvironment. To test our hypothesis, we used the KrasG12D; PdxCre1 (KC) genetically engineered mouse (GEM) model and tested the utility of AB-680, a small molecule inhibitor targeting CD73, to inhibit PanIN progression. AB-680, or vehicle control, was administered using oral gavage delivery three days/week at 10mg/kg, beginning when the mice were two months old and lasting three months. We euthanized the mice at five months old. In the KC model, we quantified significantly less pancreatitis, early and advanced PanIN, and quantified a significant increase in M1 macrophages in AB-680-treated mice. Single Cell RNA sequencing (scRNA-seq) of pancreata of AB-680 treated mice revealed increased infiltration of CD4+ T cells, CD8+ T cells, and mature B cells. The scRNA-seq analysis showed that CD73 inhibition reduced M2 macrophages, acinar, and PanIN cell populations. CD73 inhibition enhanced immune surveillance and expanded unique clonotypes of TCR and BCR, indicating that inhibition of CD73 augments adaptive immunity early in the neoplastic microenvironment. Overall design: We used the genetically engineered KrasG12D/PdxCre1(KC) mouse model, which slowly developed pancreatic intraepithelial neoplasia (PanIN) and pancreatic ductal adenocarcinoma (PDAC) over 12-15 months. AB-680 (HY-125286) was dissolved in 20% SBE-ß-CD (MedChem Express, HY-17031/CS-0731) and DMSO (Sigma-Aldrich, D8418) and administered oral gavage 10mg/kg three days a week. The Vehicle Control was DMSO in 20% SBE-ß-CD and administered oral gavage three days a week. Pancreas tissue from two mice per group was collected. The two tissue samples from each respective group were combined and submitted as one sample per group for library preparation.