Radiation-induced effects on TGF-ß and PDGF receptor signaling in cancer-associated fibroblasts.

BACKGROUND: Cancer-associated fibroblasts (CAFs) consist of heterogeneous connective tissue cells and are often constituting the most abundant cell type in the tumor stroma. Radiation effects on tumor stromal components like CAFs in the context of radiation treatment is not well-described. AIM: This study explores potential changes induced by ionizing radiation (IR) on platelet-derived growth factor (PDGF)/PDGFRs and transforming growth factor-beta (TGF-ß)/TGFßRs signaling systems in CAFs. METHODS AND RESULTS: Experiments were carried out by employing primary cultures of human CAFs isolated from freshly resected non-small cell lung carcinoma tumor tissues. CAF cultures from nine donors were treated with one high (1 × 18 Gy) or three fractionated (3 × 6 Gy) radiation doses. Alterations in expression levels of TGFßRII and PDGFRα/ß induced by IR were analyzed by western blots and flow cytometry. In the presence or absence of cognate ligands, receptor activation was studied in nonirradiated and irradiated CAFs. Radiation exposure did not exert changes in expression of PDGF or TGF-ß receptors in CAFs. Additionally, IR alone was unable to trigger activation of either receptor. The radiation regimens tested did not affect PDGFRß signaling in the presence of PDGF-BB. In contrast, signaling via pSmad2/3 and pSmad1/5/8 appeared to be down-regulated in irradiated CAFs after stimulation with TGF-ß, as compared with controls. CONCLUSION: Our data demonstrate that IR by itself is insufficient to induce measurable changes in PDGF or TGF-ß receptor expression levels or to induce receptor activation in CAFs. However, in the presence of their respective ligands, exposure to radiation at certain doses appear to interfere with TGF-ß receptor signaling.

Synthesis of oleanolic acid analogues targeting PDGF receptor inhibitors and their antitumor biological activities.

The PDGF receptor is mock-coupled with a known active compound, and 14 novel skeleton candidate compounds were designed and synthesized. The structure was confirmed by 1H NMR, 13C NMR and MS. The in vitro cytotoxicity of the two cancer cell lines (SGC-7901 and A549) was evaluated by MTT assay. PDGF receptor protein inhibition assays were performed on I6 and II4 using fluorescence polarization immunoassay (FPIA). [Formula: see text].

Involvement of CD9 and PDGFR in migration is evolutionarily conserved from Drosophila glia to human glioma.

Platelet-derived growth factor receptor (PDGFR) signaling plays an important role in the biology of malignant gliomas. To investigate mechanisms modulating PDGFR signaling in gliomagenesis, we employed a Drosophila glioma model and genetic screen to identify genes interacting with Pvr, the fly homolog of PDGFRs. Glial expression of constitutively activated Pvr (λPvr) led to glial over migration and lethality at late larval stage. Among 3316 dsRNA strains crossed against the tester strain, 128 genes shifted lethality to pupal stage, including tetraspanin 2A (tsp2A). In a second step knockdown of all Drosophila tetraspanins was investigated. Of all tetraspanin dsRNA strains only knockdown of tsp2A partially rescued the Pvr-induced phenotype. Human CD9 (TSPAN29/MRP-1), a close homolog of tsp2A, was found to be expressed in glioma cell lines A172 and U343MG as well as in the majority of glioblastoma samples (16/22, 73 %). Furthermore, in situ proximity ligation assay revealed close association of CD9 with PDGFR α and ß. In U343MG cells, knockdown of CD9 blocked PDGF-BB stimulated migration. In conclusion, modulation of PDGFR signaling by CD9 is evolutionarily conserved from Drosophila glia to human glioma and plays a role in glia migration.

Fibroblast response to gadolinium: role for platelet-derived growth factor receptor.

OBJECTIVE: The purpose of this study was to assess the effects of gadolinium (Gd3+), provided as gadolinium chloride, on fibroblast function. MATERIALS AND METHODS: Human dermal fibroblasts in monolayer culture and intact skin in organ culture were exposed to the lanthanide metal (1-20 µM). RESULTS: Increased proliferation was observed, in association with upregulation of matrix metalloproteinase-1 and tissue inhibitor of metalloproteinases-1, without an apparent increase in production of type I procollagen. A platelet-derived growth factor (PDGF) receptor-blocking antibody inhibited fibroblast proliferation in response to Gd3+ as did inhibitors of signaling pathways--that is, mitogen-activated protein kinase and phosphatidylinositol-3 kinase pathways--that are activated by PDGF. CONCLUSION: The responses to gadolinium chloride are similar to responses previously seen with chelated Gd3+ in clinically used magnetic resonance imaging contrast agents. Fibroblast responses appear to reflect Gd3+-induced PDGF receptor activation and downstream signaling. Increased dermal fibroblast proliferation in conjunction with effects on matrix metalloproteinase-1 and tissue inhibitor of metalloproteinases-1 could contribute to the fibroplastic/fibrotic changes seen in the lesional skin of individuals with nephrogenic systemic fibrosis.