Pancreatic cancer is a very aggressive disease characterized by a marked desmoplasia with a predominant Th2 (GATA-3⁺) over Th1 (T-bet⁺) lymphoid infiltrate. We found that the ratio of GATA-3⁺/T-bet⁺ tumor-infiltrating lymphoid cells is an independent predictive marker of patient survival. Patients surgically treated for stage IB/III disease with a ratio inferior to the median value had a statistically significant prolonged overall survival, implying an active role for Th2 responses in disease progression. Thymic stromal lymphopoietin (TSLP), which favors Th2 cell polarization through myeloid dendritic cell (DC) conditioning, was secreted by cancer-associated fibroblasts (CAFs) after activation with tumor-derived tumor necrosis factor α and interleukin 1β. TSLP-containing supernatants from activated CAFs induced in vitro myeloid DCs to up-regulate the TSLP receptor (TSLPR), secrete Th2-attracting chemokines, and acquire TSLP-dependent Th2-polarizing capability in vitro. In vivo, Th2 chemoattractants were expressed in the tumor and in the stroma, and TSLPR-expressing DCs were present in the tumor stroma and in tumor-draining but not in nondraining lymph nodes. Collectively, this study identifies in pancreatic cancer a cross talk between tumor cells and CAFs, resulting in a TSLP-dependent induction of Th2-type inflammation which associates with reduced patient survival. Thus, blocking TSLP production by CAFs might help to improve prognosis in pancreatic cancer.

In pancreatic ductal adenocarcinomas (PDAC), lymphoid infiltrates, comprised mainly of Th2 cells, predict a poor survival outcome in patients. IL4 signaling has been suggested to stabilize the Th2 phenotype in this setting, but the cellular source of IL4 in PDAC is unclear. Here, we show that basophils expressing IL4 are enriched in tumor-draining lymph nodes (TDLN) of PDAC patients. Basophils present in TDLNs correlated significantly with the Th2/Th1 cell ratio in tumors, where they served as an independent prognostic biomarker of patient survival after surgery. Investigations in mouse models of pancreatic cancer confirmed a functional role for basophils during tumor progression. The recruitment of basophils into TDLN relied partly upon the release of chemokine CCL7/MCP3 by "alternatively activated" monocytes, whereas basophil activation was induced by T-cell–derived IL3. Our results show how basophils recruited and activated in TDLNs under the influence of the tumor microenvironment regulate tumor-promoting Th2 inflammation in PDAC, helping in illuminating a key element of the immune milieu of pancreatic cancer. Cancer Res; 76(7); 1792–803. ©2016 AACR.

Background The thymic stromal lymphopoietin (TSLP), a key cytokine for development of Th2 immunity, is produced by cancer associated fibroblasts (CAFs) in pancreatic cancer where predominant tumor infiltrating Th2 over Th1 cells correlates with reduced patients’ survival. Which cells and molecules are mostly relevant in driving TSLP secretion by CAFs in pancreatic cancer is not defined. Methods We performed in vitro, in vivo and ex-vivo analyses. For in vitro studies we used pancreatic cancer cell lines, primary CAFs cultures, and THP1 cells. TSLP secretion by CAFs was used as a read-out system to identify in vitro relevant tumor-derived inflammatory cytokines and molecules. For in vivo studies human pancreatic cancer cells and CAFs were orthotopically injected in immunodeficient mice. For ex-vivo studies immunohistochemistry was performed to detect ASC (apoptosis-associated speck-like protein containing a caspase recruitment domain) expression in surgical samples. Bioinformatics was applied to interrogate published data sets. Results We show in vitro that IL-1α and IL-1β released by pancreatic cancer cells and tumor cell-conditioned macrophages are crucial for TSLP secretion by CAFs. Treatment of immunodeficient mice orthotopically injected with human IL-1 positive pancreatic cancer cells plus CAFs using the IL-1R antagonist anakinra significantly reduced TSLP expression in the tumor. Importantly, we found that pancreatic cancer cells release alarmins, among which ASC, able to induce IL-1β secretion in macrophages. The relevance of ASC was confirmed ex-vivo by its expression in both tumor cells and tumor associated macrophages in pancreatic cancer surgical samples and survival data analyses showing statistically significant inverse correlation between ASC expression and survival in pancreatic cancer patients. Conclusions Our findings indicate that tumor released IL-1α and IL-1β and ASC are key regulators of TSLP secretion by CAFs and their targeting should ultimately dampen Th2 inflammation and improve overall survival in pancreatic cancer.

Pancreatic cancer is a devastating disease with dismal prognosis. The tumor microenvironment is composed by multiple cell types, molecular factors, and extracellular matrix forming a strong desmoplastic reaction, which is a hallmark of the disease. A complex cross-talk between tumor cells and the stroma exists with reciprocal influence that dictates tumor progression and ultimately the clinical outcome. In this context, tumor infiltrating immune cells through secretion of chemokine and cytokines exert an important regulatory role. Here we review the correlation between the immune infiltrates, evaluated on tumor samples of pancreatic cancer patients underwent surgical resection, and disease free and/or overall survival after surgery. Specifically, we focus on tumor infiltrating lymphocytes (TILs), mast cells (MCs) and macrophages that all contribute to a Th2-type inflammatory and immunosuppressive microenvironment. In these patients tumor immune infiltrates not only do not contribute to disease eradication but rather the features of Th2-type inflammation and immunosuppression is significantly associated with more rapid disease progression and reduced survival.