Tumor microenvironment: Blood vascular system in cancer metastasis

Despite improvements in diagnosis and other therapeutic methods for cancer treatment, mortality has increased only by a few months at best. It is a well-known fact that most cancer patients die due to metastasis. Different factors that contribute to the severity of metastasis include: (a) occurrence of metastasis before diagnosis of the primary tumor; (b) multiple localization of metastatic tumors; (c) biological heterogeneity of the primary neoplasm and metastatic tumors; and (d) the negative influence of the microenvironment on the response of a metastatic tumor cell to systemic therapy. For the past decade, various studies have shown the role of tumor microenvironments in cancer progression. Now it is well established that metastasis is an outcome of cancer cell adaptation to its microenvironment. Metastatic cancer cells have properties that enable them not only to adapt to an alien environment, but also to modify it in such a way that it becomes conducive for the establishment and continuous growth of the secondary tumor. Importantly, the tumor microenvironment, which is genetically more stable than tumor cells, is an attractive target for therapeutic purposes. Therefore only a better understanding of the tumor microenvironment will lead to improvements in the design of a more effective therapy for cancer metastasis.