Cholangiocarcinoma (CCA) is characterized by an abundant stromal reaction. Cancer-associated fibroblasts (CAF) are pivotal players in tumor growth and invasiveness and represent a potential therapeutic target. To understand the mechanisms leading to CAF recruitment in CCA, we studied: 1) the expression of epithelial-mesenchymal transition (EMT) in surgical CCA specimens and CCA cells; 2) the lineage tracking of an EGFP-expressing human male CCA cell line (EGI-1) after xenotransplantation into severe-combined-immunodeficient mice; 3) the expression of platelet-derived growth factors (PDGFs) and their receptors in vivo and in vitro; 4) the secretion of PDGFs by CCA cells; 5) the role of PDGF-D in fibroblast recruitment in vitro; 6) the downstream effectors of PDGF-D signaling. CCA cells expressed several EMT biomarkers but not α-SMA. Xenotransplanted CCA masses were surrounded and infiltrated by α-SMA-expressing CAF, which were negative for EGFP and the human Y-probe, but positive for the murine Y-probe. CCA cells were strongly immunoreactive for PDGF-A and -D, whilst CAF expressed PDGFRβ. PDGF-D, a PDGFRβ agonist, was exclusively secreted by cultured CCA cells. Fibroblast migration was potently induced by PDGF-D and CCA conditioned medium, and was significantly inhibited by PDGFRβ blockade with Imatinib and by silencing PDGF-D expression in CCA cells. In fibroblasts, PDGF-D activated the Rac1 and Cdc42 Rho GTPases and JNK. Selective inhibition of Rho GTPases (particularly Rac1) and of JNK strongly reduced PDGF-D-induced fibroblast migration. Conclusion: CCA cells express several mesenchymal markers, but do not transdifferentiate into CAF. Instead, CCA cells recruit CAF by secreting PDGF-D, which stimulates fibroblast migration via PDGFRβ and Rho GTPase and JNK activation. Targeting tumor/stroma interactions with inhibitors of PDGF-D pathway may offer a novel therapeutic approach. (HEPATOLOGY 2013)
Cadamuro, M., Nardo, G., Indraccolo, S., Dall'Olmo, L., Sambado, L., Moserle, L., et al. (2013). Platelet-derived growth factor-D and Rho GTPases regulate recruitment of cancer-associated fibroblasts in cholangiocarcinoma. HEPATOLOGY, 58(3), 1042-1053 [10.1002/hep.26384].
Platelet-derived growth factor-D and Rho GTPases regulate recruitment of cancer-associated fibroblasts in cholangiocarcinoma
CADAMURO, MASSIMILIANO;Colledan, M;STRAZZABOSCO, MARIO
2013
Abstract
Cholangiocarcinoma (CCA) is characterized by an abundant stromal reaction. Cancer-associated fibroblasts (CAF) are pivotal players in tumor growth and invasiveness and represent a potential therapeutic target. To understand the mechanisms leading to CAF recruitment in CCA, we studied: 1) the expression of epithelial-mesenchymal transition (EMT) in surgical CCA specimens and CCA cells; 2) the lineage tracking of an EGFP-expressing human male CCA cell line (EGI-1) after xenotransplantation into severe-combined-immunodeficient mice; 3) the expression of platelet-derived growth factors (PDGFs) and their receptors in vivo and in vitro; 4) the secretion of PDGFs by CCA cells; 5) the role of PDGF-D in fibroblast recruitment in vitro; 6) the downstream effectors of PDGF-D signaling. CCA cells expressed several EMT biomarkers but not α-SMA. Xenotransplanted CCA masses were surrounded and infiltrated by α-SMA-expressing CAF, which were negative for EGFP and the human Y-probe, but positive for the murine Y-probe. CCA cells were strongly immunoreactive for PDGF-A and -D, whilst CAF expressed PDGFRβ. PDGF-D, a PDGFRβ agonist, was exclusively secreted by cultured CCA cells. Fibroblast migration was potently induced by PDGF-D and CCA conditioned medium, and was significantly inhibited by PDGFRβ blockade with Imatinib and by silencing PDGF-D expression in CCA cells. In fibroblasts, PDGF-D activated the Rac1 and Cdc42 Rho GTPases and JNK. Selective inhibition of Rho GTPases (particularly Rac1) and of JNK strongly reduced PDGF-D-induced fibroblast migration. Conclusion: CCA cells express several mesenchymal markers, but do not transdifferentiate into CAF. Instead, CCA cells recruit CAF by secreting PDGF-D, which stimulates fibroblast migration via PDGFRβ and Rho GTPase and JNK activation. Targeting tumor/stroma interactions with inhibitors of PDGF-D pathway may offer a novel therapeutic approach. (HEPATOLOGY 2013)
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