Role of angiogenesis in the development and growth of liver metastasis.

Cancer metastasis is a highly complex process that involves aberrations in gene expression by cancer cells leading to transformation, growth, angiogenesis, invasion, dissemination, survival in the circulation, and subsequent attachment and growth in the organ of metastasis. Angiogenesis facilitates metastasis formation by providing a mechanism to (1) increase the likelihood of tumor cells entering the blood circulation and (2) provide nutrients and oxygen for growth at the metastatic site. The formation and establishment of metastatic lesions depend on the activation of multiple angiogenic pathways at both primary and metastatic sites. A variety of factors involved in the angiogenesis of liver metastasis have been identified and may serve as prognostic markers and targets for therapy. Vascular endothelial growth factor, interleukin-8, and platelet-derived endothelial cell growth factor are all proangiogenic factors that have been associated with liver metastasis from various primary tumor types. Inhibition of the activity of these factors is a promising therapeutic approach for patients with liver metastases. In addition, inhibition of integrins that mediate endothelial cell survival may also serve as a component of therapeutic regimens for liver metastases. This review focuses on the biology of angiogenesis in liver metastasis formation and growth. Because colorectal carcinoma is the most common tumor to metastasize to the liver, this disease will serve as a paradigm for the study of angiogenesis in liver metastases.