the possibility that PPAR participates in the development of CSCs was suggested. Disclosures: The following people have nothing to disclose: Osamu Kimura, Yasuteru Kondo, Takayuki Kogure, Jun Inoue, Yu Nakagome, Tatsuki Morosawa, Tomoaki Iwata, Yasuyuki Fujisaka, Teruyuki Umetsu Cholangiocarcinoma (CCA) is characterised by a strong invasiveness and a poor prognosis. Currently, surgical curative interventions can be offered to less than 30% of CCA patients, due to the early metastasisation to regional lymph nodes. In CCA, lymphangiogenesis develops within an abundant tumor reactive stroma, mainly composed by cancer-associated fibro-blasts (CAFs) recruited, among others, by Plateled-derived check details Growth Factor-D (PDGF-D) which is specifically secreted by CCA cells. In CCA, the mechanisms modulating lymphangio-genesis remains unexplored. Our aim was to investigate if PDGF-D secreted by CCA induces the release of lymphangio-genic growth factors (VEGF-C, Angiopoietin (Ang)-1 and-2) by CAF. METHODS. In human primary fibroblast cell lines challenged with PDGF-D, we evaluated the secretion of VEGF-C, Ang-1 and Ang-2 (ELISA). Furthermore, we studied the effects of the PDGFRβ inhibitor imatinib mesylate, of the MEK inhibitor U0126 and of the JNK inhibitor SP600126, on the secretion of lymphangiogenic growth factors (ELISA), and NF-kB expression (Western blotting).
In human CCA samples derived from surgical resection, we studied the immunohistochemical expression of D2-40 (lymphatic endothelial cell, LEC marker), CD34 (vascular endothelial cell marker), learn more αSMA (CAF marker), PDGF-D, VEGF-C, and VEGFR3 and compared with the per-itumoural area. Lymphatic microvessel density (LMVD) and vascular microvessel density (VMVD) were calculated in CCA and compared with HCC samples (n=6). RESULTS. Following stimulation RVX-208 with PDGF-D, cultured fibroblasts secreted significantly higher levels of VEGF-C but not of Ang-1; Ang-2 was not expressed. PDGF-D potently enhanced VEGF-C secretion by fibroblasts; this effect was associated with NF-kB nuclearization,
and was blunted by imatinib mesylate, U0126 and SP600126. As compared to HCC, CCA was characterized by a stark increase in LMVD with a concurrent reduction in VMVD; lymphatic vessels were clearly distributed in close contact to CAF and to CCA cells. As compared with the peritumoral area, in PDGF-D was specifically expressed in CCA cells, whereas VEGF-C was expressed by CAF and VEGFR-3 by LECs, consistent with a sequential cross talk from tumoral bile ducts to lymphatic vessels via CAF. CONCLUSIONS. PDGF-D released by CCA cells stimulates CAF to secrete VEGF-C through an ERK/ JNK/NF-kB pathway. In turn, CAF expressing VEGF-C stimulate LMVD in CCA. Pharmacological interference with the above cross talk mechanism may be a therapeutic target to inhibit CCA spread through lymphatics.