title: Microenvironment and multiple myeloma spread.
abstract: In patients with multiple myeloma (MM), the bone marrow (BM) contains hematopoietic stem cells (HSCs) and non-hematopoietic cells. HSCs are able to give rise to all types of mature blood cells, while the non hematopoietic component includes mesenchymal stem cells (MSCs), fibroblasts, osteoblasts, osteoclasts, chondroclasts, endothelial cells, endothelial progenitor cells (EPCs), B and T lymphocytes, NK cells, erythrocytes, megakaryocytes, platelets, macrophages and mast cells. All of these cells form specialized "niches" in the BM microenvironment which are close to the vasculature ("vascular niche") or to the endosteum ("osteoblast niche"). The "vascular niche" is rich in blood vessels where endothelial cells and mural cells (pericytes and smooth muscle cells) create a microenvironment that affects the behavior of several stem and progenitor cells. The vessel wall serves as an independent niche for the recruitment of endothelial progenitor cells, MSCs and HSCs. The activation by angiogenic factors and inflammatory cytokines switch the "vascular niche" to promote MM tumor growth and spread. This review will focus on the mechanisms involved in the generation of signals released by endothelial cells in the "vascular niche" that promote tumor growth and spread in MM.
authors.affiliation: Department of Basic Medical Sciences, Neurosciences and Sensory Organs, University of Bari Medical School, Bari, Italy, National Cancer Institute "Giovanni Paolo II", Bari, Italy. Electronic address: domenico.ribatti@uniba.it.
authors.forename: Domenico
authors.initials: D
authors.lastname: Ribatti
authors.affiliation: Department of Biomedical Sciences and Human Oncology, University of Bari Medical School, Bari, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Moschetta
authors.affiliation: Department of Biomedical Sciences and Human Oncology, University of Bari Medical School, Bari, Italy. Electronic address: angelo.vacca@uniba.it.
authors.forename: Angelo
authors.initials: A
authors.lastname: Vacca
mesh_terms: D006412:Hematopoietic Stem Cells / Q000276:immunology* / Q000473:pathology*; D006801:Humans; D009101:Multiple Myeloma / Q000097:blood / Q000276:immunology / Q000473:pathology; D009389:Neovascularization, Pathologic / Q000276:immunology / Q000473:pathology; D015398:Signal Transduction / Q000276:immunology*; D059016:Tumor Microenvironment / Q000276:immunology*
keywords: Angiogenesis; Endothelial cells; Multiple myeloma; Tumor microenvironment