ANGIOGENESIS IN BOTH NORMAL AND PATHOLOGICAL DEVELOPMENT

Angiogenesis is the formation and development of new blood vessels from pre-existing vasculature. Inadequate balance of angiogenesis can cause various pathological disorders and considered mainly in cancer development. The blood vessels in solid tumors have abnormal physiological and morphological characteristics compared to the normal vasculatures. Two main gene expressions (matrix metalloproteinases-9) and (tumor necrosis factor-α) have very critical role in development of angiogenesis associated with cancer as well as its further metastasis. As stem cells are considered the source for all cell differentiation in every process in the body, they also are the source for the whole process of tumor tissues development. Stem cells participate in angiogenesis by differentiation into vascular lineage and/or by releasing angiogenic factors. Cancer stem cells are tumor initiating cells and predicted as a critical population of tumor cells which might mainly drive each step of tumor development.