Story Summary: They found that tumors can grow from adult stem cells that have lost a specific tumor-suppressor gene. The gene, Apc, has previously been implicated in human gastrointestinal cancers, including colon cancer. A long-standing question in cancer biology is Do tumors arise from specific cell types? When cells lining the intestinal tract die or are sloughed off, stem cells divide to produce replacements for the lost cells. When the researchers selectively knocked out the Apc gene in these cells, they saw that the cells divided rapidly, forming masses of cells that protruded into the gut interior. These tumor-like masses had characteristics very like those of adenomas of the human gastrointestinal tract. Without surgery to remove all or part of the colon, colon cancer is virtually inevitable in those with Apc loss. The incidence of this type of cancer ranges from 1 in 7,000 to 1 in 22,000. We have developed a system in fruit flies that allows us to precisely manipulate gene function in individual cells of the gastrointestinal tract, so the stage was set to ask whether Apc had a specific function in intestinal stem cells. The researchers showed that Apc is needed to regulate stem cell proliferation in the fruit fly gut. Loss of Apc function short-circuits regulation, increasing the number of cells even though there is no physiological need for new cells. Apc is known to be part of a complex of several proteins in cells that destroys other proteins. The fruit fly now provides a powerful genetic model system that can be used to study the earliest steps of gastrointestinal tumorigenesis, Micchelli says. Such genes constitute novel drug targets capable of retarding tumor growth at a very early stage. ——————————————————————————–Lee WC, Beebe K, Sudmeier L, Micchelli CA. This story was released on 2009-08-18….Read the Full Story

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