The IL-1/IL-1 receptor axis and tumor cell released inflammasome adaptor ASC are key regulators of TSLP secretion by cancer associated fibroblasts in pancreatic cancer

Abstract

BackgroundThe 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.MethodsWe 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.ResultsWe 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.ConclusionsOur 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.Electronic supplementary materialThe online version of this article (10.1186/s40425-019-0521-4) contains supplementary material, which is available to authorized users.

Thymic Stromal Lymphopoietin and Cancer: Th2-Dependent and -Independent Mechanisms

“…In cancer the expression of the two isoforms was evaluated in breast (21) and pancreatic (22) cancers. In breast cancer cells both isoforms were upregulated upon stimulation with IL-1β (21).…”

Dual Role of Inflammasome Adaptor ASC in Cancer

“…A novel role for extracellular ASC released by tumor cells in pancreatic cancer was recently reported (Brunetto et al, 2019). In this study, IL-1α and IL-1β from tumor cells and tumor associated macrophages (TAMs) were key to inducing cancerassociated fibroblasts (CAFs) to secrete the thymic stromal lymphopoietin (TSLP), which in turn drives predominant tumorpromoting Th2 cells, through the activation of resident dendritic cells with Th2 polarizing capability (De Monte et al, 2011;Protti and De Monte, 2012).…”

“…In pancreatic cancer ASC expression in the tumor, evaluated by immunohistochemistry, was upregulated in over 90% of tumor samples compared with surrounding tissue (Brunetto et al, 2019). Analysis in ASC expression distribution within the tumor showed that, in addition to the expression in tumor cells, ASC was also highly expressed in TAMs in all samples.…”

“…Analysis in ASC expression distribution within the tumor showed that, in addition to the expression in tumor cells, ASC was also highly expressed in TAMs in all samples. Patients with ASC mRNA expression inferior to the median value had a significantly increased survival (Brunetto et al, 2019), suggesting that ASC expression in pancreatic cancer correlates with an unfavorable clinical outcome.…”

The Immune Microenvironment in Pancreatic Cancer

“…In turn, TSLP was secreted by cancer-associated fibroblasts (CAFs) activated by IL-1α and IL-1β, which are products of cancer cells and tumor cell-conditioned macrophages [ 152 ]. Basophils expressing IL-4 present in the tumor draining lymph nodes of patients with PDAC probably contribute to the stabilization of the Th2 phenotype, since their presence correlates with an increased Th2/Th1 ratio in tumors and poor patient survival [ 153 ]. The Th2-driven responses promoting PDAC also depend on B cells and FcRγ + tumor-associated macrophages (TAMs) expressing Bruton tyrosine kinase (BTK) independent of PI3Kγ.…”