Newer Vascular Targets.

The identification of cell-surface markers expressed selectively by tumor vasculature is challenging. To get as close to the human disease as possible, investigators have isolated endothelial cells from fresh human tumor specimens and subjected them to RNA-based gene-expression analysis. The data indicate that there are few proteins that distinguish tumor vasculature from normal vasculature and re-enforce the notion that the endothelium is a tissue specialized cell type. Endosialin and tumor endothelial marker 7 (TEM 7) were identified as a cell-surface TEMs. The selective expression of endosialin and TEM 7 by tumor vasculature and stroma has been confirmed. Although the function of endosialin and TEM 7 remains to be elucidated, the expression pattern for this protein may be favorable for cancer therapy. PRL-3 was also identified by SAGE (serial analysis of gene expression) as a TEM. PRL-3 is an intracellular phosphatase that is expressed not only in tumor vasculature but in aggressive disease. SAGE analysis of subpopulations of tumors has provided useful leads for new vascular targets. It remains to the basic scientists to elucidate the function of these proteins and to the "drug hunters" to determine whether these targets can be used in therapeutically meaningful ways. [ABSTRACT FROM AUTHOR]