difference ring. a gene sequence called TEM-7 (red) was highly expressed in endothelial cells of blood vessels in a colorectal tumor.
researchers have yet obtained the most detailed picture of how cancer tumors secure blood supplies that feed their growth. In August 18 number of Science , they show a set distinctly different gene is expressed in blood vessels of the human colon cancers compared to normal colon tissue. The work could pave the way for new drugs that stifle tumors by blocking the growth of blood vessels.
Scientists had already identified some "marker" gene that differ between normal blood vessels and presumably newly formed vessels that feed tumors growing. But a team led by Bert Vogelstein and Kenneth Kinzler Johns Hopkins University School of Medicine undertook to cast a much wider net. First, they had to overcome a serious obstacle - learning to isolate pure populations of endothelial cells that form blood vessels. These cells are only one of many types of cells present in the tumor and normal tissues, and are present in relatively small amounts. After trying for 2 years, Brad St. Croix the Hopkins group managed using a protein called P1H12, which occurs mainly on endothelial cells, as a handle to separate the cells.
Next, the team sought the active genes in endothelial cells of colon cancers and tissue from normal colon from the same patients. They found about 100,000 extracts of messenger RNA, representing more than 32,500 genes that had protein. Of these, 46 are substantially more active and 33 were less active in tumor endothelial cells than in normal colon tissue. In addition, the researchers found similar patterns of expression for most of the same genes in other vessels tumors, including lung, brain and metastatic liver cancers. "It is clear that the tumor vasculature is different from the normal vasculature," says Douglas Hanahan of the University of California, San Francisco.
Experts interested in the development of new treatments against cancer are intrigued. Philip Thorpe of the University of Texas Southwestern Medical Center at Dallas notes that the work could lead to compounds that block the protein products of genes overexpressed in the hope of cutting the growth of tumor vessels. Indeed, the researcher Judah Folkman Angiogenesis of Harvard Medical School in Boston, who launched the idea of killing tumors by targeting the blood vessels, described the document as a "landmark".
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