Cancer is a condition that occurs in our body due to the uncontrolled and abnormal cell growth and division. Normal body cells become cancerous due to DNA damage or gene mutations or break down of mechanisms which regulated the cell cycle. Cancerous cells grow continuously unlike normal cells, and also have the capacity to invade other healthy parts of the body.

Angiogenesis is a process of making new blood vessels in the body. Angiogenesis or new blood formation occurs in an adult, during healing of wound or repairing the some damage occurred in the organ or tissue of the body. But in case of patients with cancer, angiogenesis or formation of new blood vessels are seen very regularly to provide blood supply or mineral and oxygen to the cancer cell and help in the tumor growth and development. Anti-angiogenesis is a kind of target therapy, which stops tumors from making new blood vessels using the drugs or other pharmaceutical substances. These new blood vessels which are formed by the tumor are very fragile when compared to the normal blood vessels formed during the normal conditions. Therefore targeting these new blood vessels using anti-angiogenesis drugs is easy, this stops the blood supply, hence stops the tumor growth.

Need for New Blood Vessel:

Cancer or tumor starts from a single cancerous cell, this cell divides and produces many number of cancer cells. When tumor is small in the beginning all these cancer cells gets their nutrients and energy from the neighbouring blood vessels, but as the tumor grows, the cancerous cells which are present in the middle of the tumor don't get the blood supply. Tumor cells to keep on dividing and grow they need blood vessels, without these blood vessels tumors can grow about 1 to 2 cubic millimetres ( the size of a pin head).

Cancer cells release the chemicals, which have the capacity to induce angiogenesis by promoting the endothelial cell growth. As more number of new blood vessels are formed, tumor cells grow and divide and form large tumors. New blood vessels provide nutrients, energy and oxygen which are needed by the tumor cells to grow. At the same time tumor cells release the chemicals which induce the formation of angiogenesis; therefore the tumor cells and blood vessels support each other's growth and development.

Anti-angiogenesis Drug Therapy:

Anti-angiogenesis drugs target the new blood vessels formed by cancer cells, which are very important for cancer cell growth and survival. Anti-angiogenesis drugs may also prevent growth of new tumors. These drugs may also help in shrinking of large tumors by destroying the blood vessels which supply blood to these tumors. A number of different pathways are used by the cancer cells to produce new blood vessels, each and every step in these pathways are used as potential targets to treat cancer. Different anti-angiogenesis drugs may target different steps involved in these pathways.

For example, one of the most important proteins involved in the formation of new blood vessels is vascular endothelial growth factor (VEGF). VGFR produced from cancer cells attach to the specific receptor and activated endothelial cells to form new blood vessels. Many of the drugs used in anti-angiogenesis treatment attack the VEGF pathway.

Bevacizumab (Avastin) first approved monoclonal antibody to trat cancer by targeting the formation of new blood vessels. Drugs like sunitinib (Sutent®) and sorafenib (Nexavar®), are also used in anti-angiogenesis therapy to treat cancer. These drugs attach to the VEGF receptors and inhibit the activation of endothelial cells by vascular endothelial growth factor protein. Hence prevents the formation of new blood vessels, this leads to the starvation of cancer cells and leads to cancer cell death.

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