Increased Intratumoral Interleukin-22Levels And Frequencies Of IL-22-producing CD4~+T Cells Correlate With Pancreatic Cancer Progression

Research background：Pancreatic cancer (PC) is an aggressive malignancy with an extremely poor prognosis;it ranks fourth among cancer-related deaths in the United States. This cancer originates inthe ductal epithelium and evolves from a premalignant lesion to fully invasive cancer. Thecauses of PC remain unknown, although some studies have shown that chronicinflammation is a common feature of actively growing pancreatic tumors. Moreover,increasing evidence indicates that cytokines, the host immune response, and relatedinflammatory and immune mediators participate in human carcinogenesis.Interleukin-22(IL-22), which belongs to the IL-10cytokine family, is a recentlyidentified T cell-derived cytokine that mediates epithelial immunity and mucosal tissuerepair. It has been shown that IL-22triggers intracellular signaling by binding to aheterodimeric receptor complex that is composed of IL-22receptor1(IL-22R1) and IL-10receptor2(IL-10R2). However, the cellular responsiveness of IL-22is mainly determinedby IL-22R1, which is expressed in many organs, including the skin, kidney, lung, trachea,pancreas, small intestine, liver, and colon. It is most highly expressed in the skin andpancreas, resulting in the activation of the JAK-STAT pathway and subsequentphosphorylation of STAT-3(pSTAT-3) and STAT-1/STAT-5. pSTAT-3induces theexpression of genes important for cell cycle progression (such as cyclinD1) as well assuppression of apoptosis (Bcl-2, Bcl-xl), eventually promoting cell survival andproliferation during inflammation-associated tumorigenesis. In rat hepatoma cells, IL-22was reported to be an activator of multiple signaling pathways, such as the JAK/STAT,ERK, JNK, and p38MAPK pathways. IL-22was shown to protect hepatocytes fromConA-induced acute liver injury via STAT-3activation, but it was suggested that IL-22may have an opposite effect in hepatocellular carcinoma. Moreover, it has recently been shown that IL-22promotes human hepatocellular carcinoma via the activation of STAT-3.To date, no studies have examined the immunoregulation of IL-22during PC progression,and it is necessary to elucidate the role of IL-22in PC carcinogenesis.IL-22+CD4+T cells, based on its secretion of cytokine IL-22, have been reportedrecently. Although some IL-22+CD4+T cells also produce other cytokines such as IL-17,some IL-22+CD4+T cells expressed IL-22but not IL-17or IFN-γ. The later is now termedas Th22cells. Th22cells, which were recently identified as inflammatory CD4+T cells thatproduce IL-22but not IL-17or IFN-γ, were demonstrated to be the main IL-22producers inthe peripheral blood. However, the main producers of IL-22among tumor-infiltratinglymphocytes (TILs) in PC remain unknown. Th22cells produce cytokines, such as IL-22,whose functions depend on the activation of STAT-3. Moreover, Th22cells andIL-22+CD4+T cells have been reported to play important roles in many inflammatorydiseases, such as psoriasis, rheumatoid arthritis, and gastric cancer. However, little is knownregarding the expression and clinical relevance of IL-22+CD4+T and Th22cells in PCtissues.In this study, we investigated the role of IL-22and IL-22+CD4+T cells during PCprogression. We measured IL-22protein levels, the frequencies of IL-22+CD4+T and Th22cells, and the association between IL-22and Phosphorylation of STAT-3in vitro. We alsoanalyzed their relationship with the tumor-node-metastasis (TNM) staging system of PC.Research Objective and Theoretical significance:To investigate the expression and clinical relevance of IL-22and IL-22-producingCD4+T cells (IL-22+CD4+T cell, Th1, Th17, Th22) in pancreatic cancer (PC) tissues. Inthis study, we aimed to investigate the association between IL-22and phosphorylation ofSTAT-3.Method:IL-22protein levels in PC tissues were measured by Western blot analysis andimmunohistochemistry. The frequencies of IL-22+CD4+T cells in tumors and peripheralblood from PC patients and healthy controls were analyzed by flow cytometry. Theassociation between IL-22and phosphorylation of STAT-3were investigated in vitromodel. Result:IL-22protein was more highly expressed in PC tissues than in peritumoral and normalpancreatic tissues. The frequencies of all IL-22+CD4+T cells, and T help cell22(Th22)(IL-22+IFN-γ-IL-17-CD4+) were significantly higher in PC tissues than in the peripheralblood of PC patients and healthy controls. It was observed that up regulation pSTAT-3andits downstream genes such as Bcl-2, CyclinD1in vitro. Finally, we found that increasedintratumoral IL-22expression, frequencies of Th22and IL-22+CD4+T cells were positivelycorrelated with PC tumor-node-metastasis (TNM) staging.Conclusion:Increased intratumoral IL-22levels, IL-22+CD4+T cells, and Th22cells are correlatedwith PC TNM staging, suggesting that IL-22, IL-22+CD4+T cells may be related to tumorprogression and are potential therapeutic targets in patients with PC.