Final answer:
Endostatin is a protein that is secreted into the extracellular matrix, where it inhibits angiogenesis by preventing the formation of new blood vessels.
Step-by-step explanation:
The protein that is thought to be secreted into the extracellular matrix that surrounds the lining of mature blood vessels, where it inhibits angiogenesis, is endostatin.
Endostatin is a naturally occurring fragment of collagen XVIII and acts as an endogenous inhibitor of angiogenesis. It prevents the formation of new blood vessels, thereby inhibiting the growth and spread of tumors.
Endostatin was discovered by scientists who observed that tumors in mice lacking collagen XVIII grew rapidly and had an extensive network of blood vessels. It was later found that endostatin inhibits the proliferation and migration of endothelial cells, which are responsible for forming new blood vessels during angiogenesis.
In a healthy body, angiogenesis is a normal part of growth and healing. However, in cancer, angiogenesis allows tumors to grow and spread. By secreting endostatin, the body can potentially regulate the formation of new blood vessels around tumors. Moreover, studies suggest that endostatin can also affect other mechanisms involved in cancer progression, such as cell migration and adhesion.
Ongoing research is aimed at leveraging the antiangiogenic properties of endostatin to develop novel cancer treatments. For instance, the use of nanoparticles to deliver endostatin directly to tumors is being explored as a way to increase its efficacy and reduce side effects.