Tumor endothelium is characterized by a matrix remodeling signature

Endothelial cells (EC) are attractive targets for therapeutic interference in diseases that are dependent on the formation of novel blood vessels, such as cancer. EC are readily accessible via the blood stream and are considered to be genetically stable, thus enabling efficient and effective drug delivery. However, for targeting of EC in blood vessels of the disease tissue, specific markers are needed. Though various studies have focused on the differences in gene expression in endothelial cells in different in vitro model systems, only few studies have focused on gene expression in EC derived from tumor tissues and corresponding normal tissues. Here, we review the gene expression data sets of EC isolated from tumors of the colon, breast, brain and ovaries. Gene ontology analysis reveals enrichment for genes involved in extracellular matrix turnover and adhesion. Several genes, including collagens 4A1, 4A2 and 1A1, SPARC, THY1 and MMP9 are overexpressed in the endothelium of more than one tumor type, whereas plexin domain containing 1 (PLXDC1), previously known as TEM7, is overexpressed in EC of all four tumor types.