Rapp et al. demonstrate that dendritic cells in the lymph node secrete CCL22 to build cell–cell contacts with CCR4-expressing regulatory T cells, leading to immune suppression. Conversely, CCL22 deficiency results in enhanced T cell immunity, shown here in the setting of vaccination, cancer, and inflammatory disease.

Background & Aims Oncogenic Kras mutation is a defining genetic alteration in pancreatic ductal adenocarcinoma (PDAC), but is not sufficient to promote cancer formation on ist own. Secondary events, such as inflammation-induced signaling via the epidermal growth factor receptor (EGFR) and expression of the SOX9 gene, are required for tumor formation. In this study we sought to identify the underlying mechanisms which link EGFR signaling to Sox9 gene induction during acinar–ductal metaplasia (ADM), a transdifferentiation process that precedes pancreatic carcinogenesis. Methods We analyzed pancreatic tissues from KrasG12D;pdx1-Cre and KrasG12D;NFATc1Δ/Δ;pdx1-Cre mice after intraperitoneal administration of caerulein or dimethyl suloxide (controls). Pharmacological inhibition of NFATc1 activation was achieved by application of cyclosporin A. Induction of EGFR signaling and its effects on expression of NFATc1 or SOX9 were investigated by quantitative reverse transcription PCR, immunoblot, and immunohistochemical analyses of mouse and human tissues and acinar cell explants. Interactions between NFATc1 and partner proteins and effects on DNA binding or chromatin modifications were studied using co-immunoprecipitation and chromatin immunoprecipitation assays in acinar cell explants and mouse tissue. Results EGFR activation induced NFATc1 expression in metaplastic tissues from patients with chronic pancreatitis and in pancreatic tissues from KrasG12D mice and promoted complex-formation with c-Jun in dedifferentiating acinar cells, thereby stimulating the transcription of ductal gene signatures to provoke ADM. This process involved NFATc1:c-Jun-mediated activation of Sox9 transcription in converting acinar cells. Pharmacological inhibition of NFATc1 or disruption of the Nfatc1 gene inhibited EGFR-mediated induction of Sox9 transcription and blocked acinar–ductal transdifferentiation and pancreatic cancer initiation. Conclusion Our findings identify an EGFR-NFATc1-Sox9 signaling cascade as a critical mediator of inflammation-induced PDAC initiation and suggest that disruption of this pathway may offer a novel chemopreventive target for high-risk pancreatitis patients.

In cancer patients, immunosuppression through regulatory T cells (Treg) is a crucial component of tumor immune evasion and contributes to disease progression. Tumor-infiltrating Treg in particular suppress local effector T cell responses and are associated with poor prognosis in tumors such as human pancreatic cancer or hepatocellular carcinoma (HCC). The chemokine CCL22 is known to recruit Treg into the tumor tissue and many types of human tumors are known to express high levels of CCL22. The mechanisms leading to intratumoral secretion of CCL22 are so far unknown. We demonstrate here that intratumoral CCL22 is induced in tumor-infiltrating immune cells through cancer cell-derived interleukin-1 (IL-1a). In pancreatic cancer and HCC, CCL22 is produced by intratumoral dendritic cells, while the cancer cells themselves do not secrete CCL22 in vitro and in vivo. Incubation of human peripheral blood mononuclear cells (PBMC) or murine splenocytes with tumor cells or tumor cell supernatants strongly induced CCL22 secretion in vitro. Tumor cell supernatants contained IL-1 and CCL22 induction in PBMC could be specifically prevented by the IL-1 receptor antagonist anakinra or by transfection of tumor cell lines with IL-1 siRNA, leading to a suppression of Treg migration. In conclusion, we identify here tumor cell-derived IL-1a as a major inducer of the Treg attracting chemokine CCL22 in human cancer cells. Therapeutic blockade of the IL-1 pathway could represent a promising strategy to inhibit tumorinduced immunosuppression.

Many solid cancers including pancreatic ductal adenocarcinoma (PDAC) are characterized by an extensive stromal reaction that is accompanied by infiltrating tumor-associated macrophages (TAMs). The role of TAMs in malignant tumors is only partially understood. Previously, we identified the transcription factor CUX1 as an important mediator of tumor progression in PDAC. Interestingly, we found that CUX1 is highly expressed not only in tumor cells but also in TAMs. On the basis of these data, we aimed to elucidate the effects of CUX1 in TAMs in vitro and in vivo. We analyzed the effects of CUX1 on cytokine expression using overexpression and knockdown strategies. The cytokine regulation by CUX1 was further assessed by reporter assays, DNA pulldown experiments and chromatin-immunoprecipitation. CUX1 expression in TAMs was analyzed in human pancreatic cancer tissues and in a genetic mouse model. Immunohistochemical analysis revealed strong expression levels of CUX1 in a distinct subset of TAMs in human PDAC tissues. Furthermore, its expression increased during tumor progression in a genetic mouse model of PDAC. Profiling experiments showed that CUX1 downregulates several NF-κB-regulated chemokines such as CXCL10, which have been associated with M1 polarization and inhibition of angiogenesis and tumor progression. We could demonstrate that CUX1 interacts with NF-κB p65, leading to reduced binding of NF-κB p65 to the chemokine promoters. In addition, CUX1 reduces acetylation of NF-κB p65 at K310 by recruiting HDAC1. Functionally, CUX1 expression in TAMs antagonizes T-cell attraction and enhances angiogenesis in vitro. We identified CUX1 as an important modulator of the TAMs phenotype and function by modulating NF-κB-dependent cytokines.