Cancer-associated fibroblasts induce epithelial–mesenchymal transition of bladder cancer cells through paracrine IL-6 signalling

Abstract

BackgroundCancer-associated fibroblasts (CAFs), activated by tumour cells, are the predominant type of stromal cells in cancer tissue and play an important role in interacting with neoplastic cells to promote cancer progression. Epithelial-mesenchymal transition (EMT) is a key feature of metastatic cells. However, the mechanism by which CAFs induce EMT program in bladder cancer cells remains unclear.MethodsTo investigate the role of CAFs in bladder cancer progression, healthy primary bladder fibroblasts (HFs) were induced into CAFs (iCAFs) by bladder cancer-derived exosomes. Effect of conditioned medium from iCAFs (CM iCAF) on EMT markers expression of non-invasive RT4 bladder cancer cell line was determined by qPCR and Western blot. IL6 expression in iCAFs was evaluated by ELISA and Western blot. RT4 cell proliferation, migration and invasion were assessed in CM iCAF +/− anti-IL6 neutralizing antibody using cyQUANT assay, scratch test and transwell chamber respectively. We investigated IL6 expression relevance for bladder cancer progression by querying gene expression datasets of human bladder cancer specimens from TCGA and GEO genomic data platforms.ResultsCancer exosome-treated HFs showed CAFs characteristics with high expression levels of αSMA and FAP. We showed that the CM iCAF induces the upregulation of mesenchymal markers, such as N-cadherin and vimentin, while repressing epithelial markers E-cadherin and p-ß-catenin expression in non-invasive RT4 cells. Moreover, EMT transcription factors SNAIL1, TWIST1 and ZEB1 were upregulated in CM iCAF-cultured RT4 cells compared to control. We also showed that the IL-6 cytokine was highly expressed by CAFs, and its receptor IL-6R was found on RT4 bladder cancer cells. The culture of RT4 bladder cancer cells with CM iCAF resulted in markedly promoted cell growth, migration and invasion. Importantly, inhibition of CAFs-secreted IL-6 by neutralizing antibody significantly reversed the IL-6-induced EMT phenotype, suggesting that this cytokine is necessary for CAF-induced EMT in the progression of human bladder cancer. Finally, we observed that IL6 expression is up-regulated in aggressive bladder cancer and correlate with CAF marker ACTA2.ConclusionsWe conclude that CAFs promote aggressive phenotypes of non-invasive bladder cancer cells through an EMT induced by the secretion of IL-6.Electronic supplementary materialThe online version of this article (10.1186/s12885-019-5353-6) contains supplementary material, which is available to authorized users.

Are Synapse-Like Structures a Possible Way for Crosstalk of Cancer with Its Microenvironment?

“…for efficient SDF-1 and TGF-β crosstalk. Following the above data, CAF, as has been shown [104], can promote aggressive metastatic phenotypes of non-invasive bladder cancer cells through an EMT induced by the secretion of IL-6. A critical study [105] showed that CAFs induced invasion through a heterophilic adhesion to both the participating N-cadherin on the membranes of CAFs and the E cadherin on the membranes of the cancer cells.…”

Fibroblasts in urothelial bladder cancer define stroma phenotypes that are associated with clinical outcome

“…The past years, stromal cells have been recognized as not only passive bystanders, but active key players in tumor progression 50 . While experimental functional studies have described tumor-supportive as well as tumor -restraining functions of CAFs in the UBC context, clinical evidence for the existence of different functional subsets remains sparse 5,[15][16][17]51 . The presented study has analyzed the interaction of the five stromal markers ASMA, CD90, FAP, PDGFRa and -b with survival and histopathological data within a UBC cohort.…”

“…experimental studies have demonstrated functional evidence for a modulatory role of fibroblasts on urothelial tumor cells in vitro and in vivo. While the majority of these studies describe pro-tumoral effects of fibroblasts derived growth-factors, like the induction of epithelial to mesenchymal transition and invasion 5,10,15,16 , one study also demonstrated that sonic hedgehog (Shh) activated fibroblasts exhibit rather tumor restraining functions during the transition of in situ to invasive UBC 17 . These findings, taken together with studies on fibroblast -tumor cell interactions in other solid tumors, point towards the existence of different fibroblast subsets with different functional roles at various stages of tumor progression and invasion (reviewed in [18][19][20][21][22][23] ).…”

Cancer‐associated fibroblasts–derived exosomes‐mediated transfer of LINC00355 regulates bladder cancer cell proliferation and invasion

“…For example, Sun et al found that CAFs exosome promoted oral squamous cell carcinoma (OSCC) cell migration and invasion by transporting miR‐382‐5p to OSCC cells . A recent study demonstrated that activated CAFs can secrete interleukin‐6 (IL‐6) to promote epithelial mesenchymal transformation of BC cells and participate in the regulation of proliferation and migration of BC cells . These findings highlighted the important role of CAFs‐exosome in mediating cell‐to‐cell communication in regulating cancer development.…”