New blood vessel formation (angiogenesis) is an important factor for continued growth and development of both malignant tumours and metastases. Development of new blood vessels in tumours is stimulated by a wide variety of angiogenic factors produced by both tumour cells and stromal cells. In addition, several naturally occurring anti-angiogenic factors have been identified, most notably angiostatin and endostatin. New blood vessel formation in tumours is a complex and dynamic process requiring:

♦ Proliferation of endothelial cells from pre-existing capillaries or venules.

♦ Breakdown of extracellular matrix.

♦ Migration of endothelial cells.

Growth and development of blood vessels within tumours requires the same factors (i.e. increased matrix degradation and altered cell-to-cell and cell-to-matrix adhesion) that are crucial to tumour cell invasion.

New blood vessel formation is important in allowing tumour cells to enter the circulation and a high degree of tumour vascularity increases the likelihood of this. Newly formed blood vessels may be more permeable to tumour cells.

There is extensive interest in angiogenesis as a therapeutic target to prevent both tumour growth and metastases with both naturally occurring and synthetic anti-angiogenic compounds being intensively investigated for possible clinical use.

0 0

Post a comment