title: Progranulin and granulin-like protein as novel VEGF-independent angiogenic factors derived from human mesothelioma cells.
abstract: Malignant mesothelioma is an aggressive tumor arising from the mesothelial cells of serous membranes and is associated with tumor angiogenesis, which is a prerequisite for tumor progression. Vascular endothelial growth factors (VEGFs) including VEGF-A have a crucial role in tumor angiogenesis. However, bevacizumab, a monoclonal antibody to VEGF-A, has recently been reported not to improve the progression-free survival of patients with malignant mesothelioma. Cell culture supernatant contains extracellular components such as serum, which can mask the existence of unknown cell-derived factors in the supernatant and make it difficult to detect the factors by subsequent protein analysis. We tried using serum-free culture for human mesothelioma cell lines, NCI-H28, NCI-H2452 and NCI-H2052, and only NCI-H2052 cells adapted to serum-free culture. We found that serum-free culture supernatant derived from NCI-H2052 cells induces the formation of capillary-like tube structures (tube formation) in three-dimensional culture, in which endothelial cells sandwiched between two layers of collagen or embedded in collagen are incubated with various angiogenic inducers. However, neither neutralization of VEGF-A nor RNA interference of VEGF receptor 2 (VEGFR2) suppressed the supernatant-induced tube formation. Using mass spectrometry, we identified a total of 399 proteins in the supernatant, among which interleukin-8 (IL-8), growth-regulated α-protein, midkine, IL-18, IL-6, hepatoma-derived growth factor, clusterin and granulin (GRN), also known as progranulin (PGRN), were included as a candidate protein inducing angiogenesis. Neutralizing assays and RNA interference showed that PGRN, but not the above seven candidate proteins, caused the supernatant-induced tube formation. We also found that NCI-H28 and NCI-H2452 cells express PGRN. Furthermore, we demonstrate that not only PGRN but also GRN-like protein have an important role in the supernatant-induced tube formation. Thus, mesothelioma-derived GRNs induce VEGF-independent angiogenesis.
authors.affiliation: Department of Environmental and Preventive Medicine, Hyogo College of Medicine, Hyogo, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Eguchi
authors.affiliation: Division of Respiratory Medicine, Department of Internal Medicine, Hyogo College of Medicine, Hyogo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Nakano
authors.affiliation: Department of Environmental and Preventive Medicine, Hyogo College of Medicine, Hyogo, Japan.
authors.forename: I
authors.initials: I
authors.lastname: Wakabayashi
mesh_terms: D045744:Cell Line, Tumor; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism*; D008175:Lung Neoplasms / Q000098:blood supply / Q000378:metabolism* / Q000473:pathology; D008654:Mesothelioma / Q000098:blood supply / Q000378:metabolism* / Q000473:pathology; D000086002:Mesothelioma, Malignant; D009389:Neovascularization, Pathologic / Q000378:metabolism; D000077153:Progranulins; D015398:Signal Transduction; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*
chemical_list: C492314:GRN protein, human; D036341:Intercellular Signaling Peptides and Proteins; D000077153:Progranulins; D042461:Vascular Endothelial Growth Factor A