Cancer Associated Fibroblast-Derived IL-6 Determines Unfavorable Prognosis in Cholangiocarcinoma By Affecting Autophagy-Associated Chemoresponse

Abstract Background: Interleukin-6 (IL-6) massively released by cancer-associated fibroblast (CAFs) has been shown to associate with the malignant behavior of cholangiocarcinoma (CCA). In vitro studies demonstrated the ability of CAFs-derived IL-6 to inhibit autophagy in CCA cells thus promoting their proliferation and invasiveness potential. Here, we aimed to validate with clinical and molecular data the hypothesis that CAFs infiltration and release of IL-6 predict poor prognosis in CCA patients following dysregulation of autophagy in cancer cells.Methods: Stromal IL-6 and cancer cell-associated autophagy proteins LC3 and p62 were assayed by Tissue MicroArray immunohistochemistry and their expression correlated with overall survival (OS) in a cohort of 70 CCA patients. Additionally, copy number and mRNA expression data of BECN1, MAP1-LC3B, p62/SQSTM1 and IL6 were extracted from a CCA database in TCGA and correlated with OS. 5-FU Cytotoxicity in CCA cells was assessed by cell counting, clonogenic assay, cytofluorometry and western blotting and immunofluorescence of apoptotic-related proteins. Results: We show that patients bearing a CCA with low production of stromal IL-6 and active autophagy flux in the cancer cells have the best prognosis and this correlates with a more effective response to post-operative chemotherapy. Similar trend was observed in CCA patients from TCGA database. In vitro experiments with primary CAFs isolated from human CCA and epigenetic manipulations showed that IL-6 plays a pivotal role in determining the autophagy-associated apoptotic response to chemotherapeutic drug in cultured human CCA cells. Conclusions: Our data support a therapeutic strategy that includes autophagy-enhancing drugs along with adjuvants limiting the stromal inflammation (i.e., the secretion of IL-6) to improve the survival of CCA patients.