title: Bone marrow-derived, alternatively activated macrophages enhance solid tumor growth and lung metastasis of mammary carcinoma cells in a Balb/C mouse orthotopic model.
abstract: BACKGROUND
  Tumor-associated macrophages, which are derived from the infiltration of circulating bone marrow-derived monocytes, consist primarily of a polarized M2 macrophage (M2-Mϕ) population and are associated with poor prognosis in various cancers. In the present study, we attempted to assess whether M2-Mϕs derived from bone marrow stimulate the promotion and progression of mammary tumors.
  
  
  METHODS
  4T1 murine mammary carcinoma cells were injected either alone or coupled with M2-Mϕs into the mammary fat pads of syngeneic female Balb/C mice. M2-Mϕs were prepared by treating monocytes isolated from female Balb/C mouse bone marrow with IL-4. Tumor cell growth was determined using an in vivo imaging system and the expression of cell proliferation-related, angiogenesis-related, and lymphangiogenesis-related proteins in tumor tissues was immunohistochemically analyzed. To evaluate the effects of the crosstalk between 4T1 cells and M2-Mϕs on the secretion and mRNA expression of cytokines and the migration of monocytes, 4T1 cells and M2-Mϕs were co-cultured and cytokine antibody array, real-time RT-PCR, and trans-well migration assays were conducted.
  
  
  RESULTS
  The co-injection of M2-Mϕs into the mammary fat pads of mice increased solid tumor growth and lung metastasis of 4T1 cells as well as the infiltration of CD45+ leukocytes into tumor tissues. The proportions of Ki-67+ proliferating cells and the expression of hypoxia inducible factor-1α, vascular endothelial cell growth factor A, CD31, vascular endothelial cell growth factor C, and lymphatic vessel endothelial receptor-1 were increased significantly in the tumor tissues of mice co-injected with 4T1 cells and M2-Mϕs. The in vitro results revealed that the proliferation of 4T1 cells, the migration of monocytes, and the secretion of granulocyte colony-stimulating factor, IFNγ, IL-1α, IL-2, IL-16, IFNγ-induced protein-10, keratinocyte-derived chemokine, macrophage colony-stimulating factor, monocyte chemotactic protein-1, macrophage inflammatory protein-1α, and RANTES were increased when 4T1 cells were co-cultured with M2-Mϕs, as compared with when the 4T1 cells were cultured alone.
  
  
  CONCLUSIONS
  The crosstalk between 4T1 cells and M2-Mϕs increased the production of cytokines, which may have induced immune cell infiltration into tumor tissues, tumor cell proliferation, angiogenesis, and lymph angiogenesis, thereby increasing solid tumor growth and lung metastasis.
authors.affiliation: Department of Food Science and Nutrition, Hallym University, Chuncheon 200-702, Korea. jyoon@hallym.ac.kr.
authors.forename: Han Jin
authors.initials: HJ
authors.lastname: Cho
authors.forename: Jae In
authors.initials: JI
authors.lastname: Jung
authors.forename: Do Young
authors.initials: DY
authors.lastname: Lim
authors.forename: Gyoo Taik
authors.initials: GT
authors.lastname: Kwon
authors.forename: Song
authors.initials: S
authors.lastname: Her
authors.forename: Jong Hoon
authors.initials: JH
authors.lastname: Park
authors.forename: Jung Han Yoon
authors.initials: JH
authors.lastname: Park
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D018925:Chemokines / Q000378:metabolism; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D005260:Female; D006023:Glycoproteins / Q000096:biosynthesis; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D019394:Ki-67 Antigen / Q000096:biosynthesis; D008175:Lung Neoplasms / Q000556:secondary*; D042583:Lymphangiogenesis; D008262:Macrophage Activation; D008264:Macrophages / Q000502:physiology*; D015674:Mammary Neoplasms, Animal / Q000378:metabolism / Q000473:pathology*; D026901:Membrane Transport Proteins; D051379:Mice; D008807:Mice, Inbred BALB C; D009389:Neovascularization, Pathologic; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000096:biosynthesis; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis; D042582:Vascular Endothelial Growth Factor C / Q000096:biosynthesis
chemical_list: D018925:Chemokines; D016207:Cytokines; D006023:Glycoproteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D019394:Ki-67 Antigen; D026901:Membrane Transport Proteins; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D042582:Vascular Endothelial Growth Factor C; C497443:Hif1a protein, mouse; C498355:Mki67 protein, mouse; C492273:LYVE1 protein, mouse; C467480:vascular endothelial growth factor A, mouse; C467483:vascular endothelial growth factor C, mouse