Final answer:
Cancers evolve to create blood vessels through angiogenesis to support tumor growth and metastasis, thereby spreading throughout the body. Angiogenesis inhibitors are used in cancer treatment to obstruct the blood vessel formation, aiming to slow or halt the progression of the tumor by restricting its blood supply.
Step-by-step explanation:
Cancers evolve the ability to create blood vessels through a process known as angiogenesis, which is essential for tumor growth beyond the limitations of passive nutrient diffusion. By acquiring sustained angiogenesis, malignant tumors can attract more blood supply and thus more oxygen and nutrients, supporting their rapid growth and proliferation. This ability also facilitates cancerous cells to metabolize at higher rates, invade nearby tissues, and metastasize to distant sites by entering the bloodstream, ultimately leading to the spread of cancer throughout the body.
Angiogenesis inhibitors are drugs used in cancer treatment because they target the growth of new blood vessels. By inhibiting angiogenesis, these drugs aim to 'starve' the tumor by cutting off its blood supply, which can slow or halt tumor growth and spread. This strategy is particularly important in cancer types known for aggressive angiogenesis and metastasis, which typically have a worse prognosis and are associated with most cancer deaths.
The blood circulation system, including the heart and blood vessels, starts developing from the embryonic stage. Understanding therapies like angiogenesis inhibitors also links back to how blood vessels initially form from blood islands and how vascular tubes eventually connect, creating a complex vascular network. However, even in vertebrates, blood circulation has evolved differently, with certain adaptations arising in long-necked animals or those living in cold environments, showcasing the diversity in vertebrate blood circulation.