they must be negative for CD14 or CD11b, CD34, CD45, CD79 alpha or CD19 and HLA-DR. Low levels of human leukocyte antigen (HLA-DR) make MSCs hypoimmunogenic. MSCs have trilineage differentiation capacity where they are able to adapt into osteoblast, chondrocytes, and adipocytes. They can also display anti-inflammatory as well as proinflammatory responses allowing for the potential to help with a broad range of immune disorders and inflammatory diseases. Sources of stromal cells It is well known that stromal cells arise and are stored in the bone marrow until maturation and differentiation. They are located in the stroma and aid hematopoietic cells in forming the elements of the blood. While a majority is found in the bone marrow scientists now know that stromal cells can be found in a variety of different tissues as well. These can include adipose tissue, endometrium, synovial fluid, dental tissue, amniotic membrane and fluid, as well as the placenta. High quality stromal cells are located in the placenta, due to their young age. MSCs lose function with age, and aged MSCs are less efficacious in therapy. Role in cancer During normal wound healing processes, the local stromal cells change into reactive stroma after altering their phenotype. However, under certain conditions, tumor cells can convert these reactive stromal cells further and transition them into tumor-associated stromal cells (TASCs). In comparison to non-reactive stromal cells, TASCs secrete increased levels of proteins and matrix metalloproteinases (MMPs). These proteins include fibroblast activating protein and alpha-smooth muscle actin. Furthermore, TASCs secrete many pro-tumorigenic factors such as vascular endothelial growth factor (VEGF), stromal-derived factor-1 alpha, IL-6, IL-8, tenascin-C, and others. These factors are known to recruit additional tumor and pro-tumorigenic cells. The cross-talk between the host stroma and tumor cells is essential for tumor growth and progression. Tumor stromal production exhibits similar qualities as normal wound repair such as new blood vessel formation, immune cell and fibroblast infiltration, and considerable remodeling of the extracellular matrix. Additionally, the recruitment of local normal host stromal cells, such as bone marrow mesenchymal stromal cells, endothelial cells, and adipocytes, help create a conspicuously heterogeneous composition. Furthermore, these cells secrete an abundance of factors that help regulate tumor development. Potential targets for tumor-associated stromal cell recruitment have been identified in the following host tissue: bone marrow, connective tissue, adipose tissue, and blood vessels. Moreover, evidence suggests that tumor-associated stroma are a prerequisite for metastasis and tumor cell