Tumor Microenvironment

The tumor microenvironment is the cellular environment in which the tumor exists.  Tumors often undergo a process called angiogenesis.  This is when the tumor causes the formation of a new blood vessel so it can get its nutrients.  Furthermore, tumors that have access to a blood vessel may shed cells to be carried in the blood, then implant somewhere else to begin growth of another tumor.  This process is known as metastasis.  Tumors cause angiogenesis by secreting signaling molecules such as the growth factors bFGF and VEGF, as well as proteins.  The secretion of these also allows the tumor to avoid eliciting an immune response.  Other cells involved in the tumor microenvironment include fibroblasts - cells that synthesizes collagen which provides the structural framework for animal tissues and plays a role in wound healing.  Additionally, cancer of the bone includes bone marrow in its tumor microenvironment.