Tumor angiogenesis in mice and men.

Over the past decade much research has focused on understanding the molecular pathways that regulate the development of a tumor-associated vasculature. In 1999, Lyden and colleagues showed that mice deficient in one to three Id1 or Id3 alleles could not support the growth of tumor xenografts due to defects in tumor-associated angiogenesis. Three recently published manuscripts have now re-examined the role of Id genes in the development of a tumor-associated vasculature using more clinically relevant tumor model systems. Remarkably, all three studies have found strikingly different results compared to the original xenograft data published in 1999. Below we review the current understanding of the role of Id genes in the development of a tumor-associated vasculature given the most recent data and suggest ways in which animal tumor model systems might be put to better use to provide more clinically relevant information.