ETS-Transcription Factor ETV1 Regulates Stromal Expansion and Metastasis in Pancreatic Cancer

Abstract

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.

The role of stromal cancer-associated fibroblasts in pancreatic cancer

“…Heeg et al found that ETV1 overexpression doubled tumor volume by stromal expansion, altered the stromal morphology, increased invasive capacity, and upregulated EMT and MMP regulators including SLUG, SNAIL, TWIST, vimentin, ZEB1, ZEB2, and MMP9. They also identified secreted protein acidic cysteine-rich (SPARC) and hyaluronan synthetase 2 (HAS2) as important separate downstream targets, both known modulators of stromal expansion [39]. In fact, SPARC knockdown completely abrogated the pro-tumorigenic effects of ETV1 overexpression solidifying this pathway link.…”

“…Waghray et al identified a subpopulation of CAFs designated as cancer-associated mesenchymal stem cells (CA-MSCs) and demonstrated their role in invasion as mediated by granulocyte-macrophage colony-stimulating factor (GM-CSF) [42]. Their findings mirrored those of Heeg et al in demonstrating larger tumors with the addition of CA-MSCs for in vivo models, but they also demonstrated increased proliferation of cancer cells themselves with increased Ki67 expression as well as stromal expansion [39]. The group further demonstrated a mechanism through which GM-CSF production by CA-MSCs induces invasion by downregulation of E-cadherin and upregulation of TWIST1 and vimentin via the JAK2/STAT3 pathway, suggesting a link to results obtained by Wormann et al [33].…”

PIK3R3 Promotes Metastasis of Pancreatic Cancer via ZEB1 Induced Epithelial-Mesenchymal Transition

“…EMT is an essential phenotypic conversion from epithelial to mesenchymal phenotype during embryonic development, and is significantly correlated with cancer invasion and metastasis [9]. The conversion of EMT is promoted by transcription factors (such as SNAIL, SLUG, TWIST1, ZEB1, and ZEB2) which can be triggered by several endogenous and exogenous factors via specific signaling pathways [10-12].…”

Cellular Plasticity and Heterogeneity in Pancreatic Regeneration and Malignancy

“…The importance of this crosstalk between PSC and pancreatic cancer cells is demonstrated by the fact, that restoration of PSC quiescence profoundly affects cancer cells in proximity [66] . Furthermore, we were able to show that an epithelial-stromal crosstalk mediated by the transcription factor ETV1 regulates stromal expansion, epithelial to mesenchymal transition and metastatic spread underscoring the importance of the stromal compartment in regulating epithelial plasticity [67] . Immunosurveillance plays as major role to eliminate mutant cells before their expansion [68] .…”