LAUSR

BACKGROUND & AIMS Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy that invades surrounding structures and metastasizes rapidly. Although inflammation is associated with tumor formation and progression, little is known about the mechanisms of this connection. We investigate the effects of interleukin 22 (IL22) in development of pancreatic tumors in mice. METHODS We performed studies with Pdx1-Cre;LSL-KrasG12D;Trp53+/-;Rosa26EYFP/+ (PKCY) mice, which develop pancreatic tumors, and PKCY mice with disruption of IL22 (PKCY IL22-/-mice). Pancreata were collected at different stages of tumor development and analyzed by immunohistochemistry, immunoblotting, real-time PCR, and flow cytometry. Some mice were given cerulean to induce pancreatitis. Pancreatic cancer cell lines (PD2560) were orthotopically injected into C57BL/6 mice or Il22-/-mice and tumor development was monitored. Pancreatic cells were injected into tail veins of mice and lung metastases were quantified. Acini were collected from C57BL/6 mice and resected human pancreata and cultured. Cell lines and acini cultures were incubated with IL22, pharmacologic inhibitors and protein levels were knocked down with small hairpin RNAs. We performed immunohistochemical analyses of 26 PDACs and 5 non-neoplastic pancreas specimens. RESULTS We observed increased expression of IL22 and the IL22 receptor (IL22R) in the pancreas compared with other tissues in mice; IL22 increased with pancreatitis and tumorigenesis. Flow cytometry indicated that the IL22 was produced primarily by T-helper 22 cells. PKCY IL22-/-mice did not develop precancerous lesions or pancreatic tumors. Addition of IL22 to cultured acinar cells increased their expression of markers of ductal metaplasia; these effects of IL22 were prevented with inhibitors of JAK signaling to STAT (ruxolitinib) or MEK (trametinib) and with STAT3 knockdown. Pancreatic cells injected into IL22-/-mice formed smaller tumors than those injected into C57BL/6. Incubation of IL22R-expressing PDAC cells with IL22 promoted spheroid formation and invasive activity, resulted increased expression of stem-associated transcription factors (GATA4, SOX2, SOX17, and NANOG), and increased markers of the epithelial-mesenchymal transition (CDH1, SNAI2, TWIST1, and beta catenin); ruxolitinib blocked these effects. Human PDAC tissues had higher levels of IL22, phosphorylated STAT3, and markers of the epithelial-mesenchymal transition than non-neoplastic tissues. Increased level of STAT3 in IL22R-positive cells was associated with shorter survival times of patients. CONCLUSIONS We found levels of IL22 to be increased during pancreatitis and pancreatic tumor development, and to be required for tumor development and progression in mice. IL22 promotes acinar to ductal metaplasia, stem cell features, and increased expression of markers of the epithelial-mesenchymal transition; inhibitors of STAT3 block these effects. Increased expression of IL22 by PDACs is associated with reduced survival times.