Background & Aims The ETS-transcription factor ETV1 is involved in the epithelial–mesenchymal transition (EMT) during pancreatic development and is induced in mouse pancreatic intraepithelial neoplasia (PanIN) and pancreatic ductal adenocarcinoma (PDAC). We investigated the function of ETV1 in stromal expansion of PDAC and metastasis, as well as its effects on its downstream target Sparc, which encodes a matricellular protein found in the PDAC stroma that has been associated with invasiveness and metastasis and poor outcomes of patients. Methods Pancreatic ductal cells were isolated from Pdx1Cre;KrasG12D/+ mice (PanIN), Pdx1Cre;KrasG12D/+;p53fl/+ and Pdx1Cre;KrasG12D/+;p53fl/+;Rosa26YFP mice (PDAC), and Pdx1Cre;KrasG12D/+; p53fl/+;Sparc-/- mice. Cells were grown in 3-dimensional organoid culture to analyze morphology, proliferation, and invasion. Human PanIN and PDAC tissues were evaluated for ETV1 expression. Orthotopic transplants of ETV1-overexpressing PDAC and control cells were assessed in mice. Results Analyses of orthotopic xenografts revealed that ETV1 induced significantly larger primary tumors than controls, with significantly increased stromal expansion and significantly more ascites and metastases. Three-dimensional organoids that overexpressed ETV1 had a disrupted cyst architecture, underwent the EMT, and were more invasive. ETV1 expression was increased in human PanINs and even more so in primary and metastatic PDACs. We identified Sparc as a functional gene target of ETV1 by luciferase assays, and SPARC and ETV1 proteins co-localized in vivo. Disruption of Sparc reduced the phenotype of stromal expansion and metastasis found with ETV1 overexpression in vivo. We identified Has2 as another downstream factor of ETV1; it may mediate ETV1's significant expansion of hyaluronic acid. Conversely, disruption of Etv1 in PDAC mice (Pdx1Cre;KrasG12D/+;p53fl/+;Rosa26YFP;Cre;Etv1fl/fl) reduced levels of SPARC and hyaluronic acid in the stroma. Conclusions ETV1 is critical in the desmoplastic stromal expansion and metastatic progression of pancreatic cancer in mice, mediated functionally in part through SPACR2 and HAS2.

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BackgroundIntrinsic chemoresistance of glioblastoma (GBM) is frequently owed to activation of the PI3K and MEK/ERK pathways. These signaling cascades are tightly interconnected however the quantitative contribution of both to intrinsic resistance is still not clear. Here, we aimed at determining the activation status of these pathways in human GBM biopsies and cells and investigating the quantitative impact of both pathways to chemoresistance.MethodsReceptor tyrosine kinase (RTK) pathways in temozolomide (TMZ) treatment naive or TMZ resistant human GBM biopsies and GBM cells were investigated by proteome profiling and immunoblotting of a subset of proteins. Resistance to drugs and RTK pathway inhibitors was assessed by MTT assays. Apoptotic rates were determined by Annexin V staining and DNA damage with comet assays and immunoblotting.ResultsWe analyzed activation of RTK pathways by proteome profiling of tumor samples of patients which were diagnosed a secondary GBM and underwent surgery and patients which underwent a second surgery after TMZ treatment due to recurrence of the tumor. We observed substantial activation of the PI3K and MEK/ERK pathways in both groups. However, AKT and CREB phosphorylation was reduced in biopsies of resistant tumors while ERK phosphorylation remained unchanged. Subsequent proteome profiling revealed that multiple RTKs and downstream targets are also activated in three GBM cell lines. We then systematically describe a mechanism of resistance of GBM cell lines and human primary GBM cells to the alkylating drugs TMZ and cisplatin. No specific inhibitor of the upstream RTKs sensitized cells to drug treatment. In contrast, we were able to restore sensitivity to TMZ and cisplatin by inhibiting PI3K in all cell lines and in human primary GBM cells. Interestingly, an opposite effect was observed when we inhibited the MEK/ERK signaling cascade with two different inhibitors.ConclusionsTemozolomide treatment naive and TMZ resistant GBM biopsies show a distinct activation pattern of the MEK/ERK and PI3K signaling cascades indicating a role of these pathways in resistance development. Both pathways are also activated in GBM cell lines, however, only the PI3K pathway seems to play a crucial role in resistance to alkylating agents and might serve as drug target for chemosensitization.Electronic supplementary materialThe online version of this article (10.1186/s12935-018-0565-4) contains supplementary material, which is available to authorized users.