title: Mesenchymal stromal cells promote tumor growth through the enhancement of neovascularization.
abstract: Mesenchymal stromal cells (MSCs), also called mesenchymal stem cells, migrate and function as stromal cells in tumor tissues. The effects of MSCs on tumor growth are controversial. In this study, we showed that MSCs increase proliferation of tumor cells in vitro and promote tumor growth in vivo. We also further analyzed the mechanisms that underlie these effects. For use in in vitro and in vivo experiments, we established a bone marrow-derived mesenchymal stromal cell line from cells isolated in C57BL/6 mice. Effects of murine MSCs on tumor cell proliferation in vitro were analyzed in a coculture model with B16-LacZ cells. Both coculture with MSCs and treatment with MSC-conditioned media led to enhanced growth of B16-LacZ cells, although the magnitude of growth stimulation in cocultured cells was greater than that of cells treated with conditioned media. Co-injection of B16-LacZ cells and MSCs into syngeneic mice led to increased tumor size compared with injection of B16-LacZ cells alone. Identical experiments using Lewis lung carcinoma (LLC) cells instead of B16-LacZ cells yielded similar results. Consistent with a role for neovascularization in MSC-mediated tumor growth, tumor vessel area was greater in tumors resulting from co-injection of B16-LacZ cells or LLCs with MSCs than in tumors induced by injection of cancer cells alone. Co-injected MSCs directly supported the tumor vasculature by localizing close to vascular walls and by expressing an endothelial marker. Furthermore, secretion of leukemia inhibitory factor, macrophage colony-stimulating factor, macrophage inflammatory protein-2 and vascular endothelial growth factor was increased in cocultures of MSCs and B16-LacZ cells compared with B16-LacZ cells alone. Together, these results indicate that MSCs promote tumor growth both in vitro and in vivo and suggest that tumor promotion in vivo may be attributable in part to enhanced angiogenesis.
authors.affiliation: Department of Medical Oncology, Hirosaki University Graduate School of Medicine, Hirosaki, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Suzuki
authors.forename: Ruowen
authors.initials: R
authors.lastname: Sun
authors.forename: Makoto
authors.initials: M
authors.lastname: Origuchi
authors.forename: Masahiko
authors.initials: M
authors.lastname: Kanehira
authors.forename: Takenori
authors.initials: T
authors.lastname: Takahata
authors.forename: Jugoh
authors.initials: J
authors.lastname: Itoh
authors.forename: Akihiro
authors.initials: A
authors.lastname: Umezawa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kijima
authors.forename: Shinsaku
authors.initials: S
authors.lastname: Fukuda
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Saijo
mesh_terms: D000818:Animals; D018952:Antigens, CD34 / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002478:Cells, Cultured; D054426:Chemokine CXCL2 / Q000378:metabolism; D018920:Coculture Techniques; D005260:Female; D005434:Flow Cytometry; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D016173:Macrophage Colony-Stimulating Factor / Q000378:metabolism; D045164:Mesenchymal Stem Cell Transplantation; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D018613:Microscopy, Confocal; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental / Q000098:blood supply / Q000378:metabolism / Q000473:pathology*; D009389:Neovascularization, Pathologic / Q000378:metabolism / Q000473:pathology*; D047368:Tumor Burden; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: D018952:Antigens, CD34; D054426:Chemokine CXCL2; C404915:Cxcl2 protein, mouse; D042461:Vascular Endothelial Growth Factor A; D049452:Green Fluorescent Proteins; D016173:Macrophage Colony-Stimulating Factor